Fact-checked by Grok 2 weeks ago

Activated carbon

Activated carbon is a family of highly porous carbonaceous materials derived from organic precursors, distinguished by their exceptionally large internal surface area—often exceeding 1,000 square meters per gram—and a tridisperse pore structure that includes micropores, transitional pores, and macropores, enabling outstanding adsorption and catalytic capabilities for removing contaminants from fluids.^[1] These properties arise from a two-stage production process: first, carbonization of carbon-rich feedstocks such as bituminous coal, coconut shells, wood, or agricultural residues like nut shells and grain hulls through pyrolysis at temperatures of 500–750°C to form a char; second, activation via physical methods (e.g., exposure to steam or carbon dioxide at 800–1,000°C) or chemical agents (e.g., phosphoric acid or zinc chloride) to etch and expand the pore network, enhancing porosity and surface reactivity.^[2]^[1] The resulting material is black, odorless, and tasteless, with adsorption primarily driven by van der Waals forces and surface chemistry influenced by elements like oxygen, hydrogen, and trace metals, allowing it to selectively bind low-molecular-weight organics, humic substances, trace pollutants, and some inorganics.^[1]^[3] Activated carbon is most notably employed in drinking water treatment to adsorb organic compounds, taste- and odor-causing agents, and disinfection byproducts like trihalomethanes, often in granular (GAC) or powdered (PAC) forms, with GAC beds post-coagulation achieving up to 80% removal of UV-absorbing substances when combined with pre-ozonation.^[1]^[3] Beyond water purification, it serves in air filtration to capture volatile organics and gases, food and beverage processing for decolorization (e.g., in sugar refining or grape juice) and ethylene removal in fruit storage, as well as industrial uses like solvent recovery, gold extraction from cyanide solutions, and pharmaceutical purification, with regeneration via thermal or steam methods extending its service life by up to 70%.^[2]^[1]

History and Overview

Historical Development

The earliest documented uses of charcoal, a precursor to activated carbon, trace back to ancient Egypt around 1500 BCE, where it was employed for medicinal purposes such as treating digestive ailments, as noted in historical papyri.^[4] By approximately 400 BCE, ancient civilizations including the Phoenicians, Greeks, Romans, and Hindus utilized charcoal for water purification, leveraging its adsorptive properties to remove impurities, odors, and bad tastes from drinking water during storage and treatment.^[5] These practices laid the groundwork for recognizing charcoal's purifying capabilities, though systematic activation processes had yet to emerge. In the late 18th century, scientific advancements began formalizing charcoal's adsorptive potential. In 1773, Swedish chemist Carl Wilhelm Scheele observed charcoal's ability to adsorb gases, marking an early step toward understanding its mechanisms.^[6] This was followed in 1785 by German-Russian chemist Johann Tobias Lowitz, who demonstrated charcoal's efficacy in decolorizing aqueous solutions, particularly for sugar syrups, leading to its industrial application in refining processes during the early 19th century.^[7] Chemical activation techniques, involving agents like metal chlorides, were patented around 1900–1901 by Raphael von Ostrejko, enabling commercial production of high-porosity carbon.^[8]^[9] Concurrently, physical activation methods using steam or carbon dioxide at high temperatures (800–1000°C) were developed in the early 1900s, enhancing porosity without chemical additives and becoming a standard for large-scale manufacturing.^[10] The 20th century saw activated carbon's industrialization accelerate, particularly during World War I, when Russian chemist Nikolay Zelinsky invented the first effective activated charcoal gas mask in 1915 to protect against chemical warfare agents like chlorine and phosgene.^[10] This spurred widespread production, often from coconut shells, and post-war applications expanded into air and water purification. Following World War II, regulatory frameworks further drove adoption; for instance, the U.S. Safe Drinking Water Act of 1974 mandated controls on organic contaminants, promoting granular activated carbon (GAC) filters in municipal treatment plants to remove taste, odor, and synthetic pollutants.^[11] In recent decades, sustainability concerns have shifted production toward renewable feedstocks, with agricultural wastes like rice husks, coffee grounds, and fruit peels emerging as viable precursors since the 2010s, reducing reliance on non-renewable sources and minimizing environmental impact through eco-friendly activation processes.^[12]

Definition and Structure

Activated carbon is a highly porous, amorphous form of carbon material engineered to exhibit an exceptionally large internal surface area, typically ranging from 500 to 1500 m²/g and reaching up to 3000 m²/g in optimized variants, through a specialized activation process that significantly enhances its adsorptive properties.^[13]^[14]^[15] This high porosity arises from a complex network of voids developed within the carbon skeleton, enabling effective capture of gases, liquids, and dissolved substances via physical adsorption. The material's efficacy stems from its ability to provide vast accessible surface for molecular interactions without relying on chemical reactivity.^[16] Structurally, activated carbon comprises an amorphous carbon matrix interspersed with graphitic microcrystallites, forming a rigid, interconnected framework that supports the porous architecture.^[17]^[18] The pores are hierarchically organized and classified by the International Union of Pure and Applied Chemistry (IUPAC) into micropores (diameter < 2 nm), which dominate the surface area; mesopores (2–50 nm), facilitating transport; and macropores (> 50 nm), serving as entry channels for adsorbates.^[19] This distribution optimizes both adsorption capacity and diffusion kinetics, with micropores contributing the majority of the surface area due to their high density.^[20] The specific surface area of activated carbon is quantitatively assessed using the Brunauer–Emmett–Teller (BET) theory, a multilayer adsorption model that interprets experimental isotherms—plotting adsorbed gas volume against relative pressure—to derive monolayer capacity and total accessible area.^[21] The foundational BET equation is:

\frac{P}{V (P_0 - P)} = \frac{1}{V_m C} + \frac{(C - 1) P}{V_m C P_0}

where V is the volume of gas adsorbed at pressure P, V_m is the monolayer adsorption capacity, P_0 is the saturation pressure, and C is a constant related to adsorption energy. Porosity development occurs during activation, where initial carbonization decomposes the precursor, expelling volatile components and generating internal voids that are subsequently enlarged.^[22] This process yields a tortuous, three-dimensional pore network essential for the material's performance.^[23]

Production

Raw Materials

Activated carbon production relies on carbonaceous precursors selected for their carbon content, availability, and ability to develop desirable pore structures upon processing. Common raw materials include fossil-derived sources such as bituminous coal and anthracite, which provide high yields and robust structures suitable for industrial-scale production. Renewable biomass options are also widely used, including hardwoods like oak for their lignocellulosic composition, coconut shells noted for their hardness and micropore-forming potential, and agricultural wastes such as rice husks and bamboo, which offer cost-effective alternatives with inherent silica content that can enhance mechanical strength.^[24]^[25]^[26] The choice of precursor influences the final activated carbon's yield, surface area, and adsorption properties, with biomass generally favoring microporosity while coal supports mesoporosity.^[26] Preparation of these precursors begins with carbonization, a thermal decomposition process known as pyrolysis, typically conducted at 400–600°C in an inert atmosphere such as nitrogen or argon to expel volatile matter and form a carbon-rich char. This step is crucial for concentrating carbon while minimizing oxidation, with the reaction progressing through dehydration, devolatilization, and aromatization phases. Key factors affecting carbonization efficiency include the precursor's particle size, where smaller particles (e.g., 1–5 mm) promote uniform heating and higher char yields by reducing mass transfer limitations, and initial moisture content, which should be below 10–15% to prevent excessive energy loss to evaporation and uneven pyrolysis.^[27]^[28]^[12] Poor control of these variables can lead to lower fixed carbon content or structural defects in the char.^[12] Since the early 2000s, sustainability considerations have driven a shift from traditional fossil fuels toward biomass wastes, reducing reliance on non-renewable resources and mitigating environmental impacts like deforestation and emissions from coal mining. This trend aligns with circular economy principles, valorizing agricultural byproducts that would otherwise contribute to waste streams. For instance, rice husks, an abundant residue from rice milling, have been processed into activated carbons with surface areas exceeding 1500 m²/g, demonstrating comparable performance to commercial products while lowering production costs and carbon footprints.^[12]^[29]^[30] Similar successes with bamboo and other lignocellulosic wastes highlight the potential for scalable, eco-friendly sourcing in modern activated carbon manufacturing.^[24]

Activation Methods

Activated carbon is produced through activation processes that develop its porous structure from carbonized precursors, primarily via physical or chemical methods. These techniques etch away carbon material to create a network of micropores, mesopores, and macropores, enhancing adsorption capabilities. Physical activation involves high-temperature treatment with oxidizing gases, while chemical activation uses activating agents at moderate temperatures to induce porosity.^[31] Physical activation begins with carbonization of the raw material at around 500–600°C under inert conditions to form char, followed by exposure to gases such as steam or carbon dioxide at elevated temperatures of 800–1000°C. This process relies on gasification reactions where the oxidizing agent reacts with carbon atoms, selectively removing them to form pores; for instance, steam activation proceeds via the endothermic water-gas reaction: C + H₂O → CO + H₂, which etches the carbon surface and generates hydrogen and carbon monoxide as byproducts. Carbon dioxide activation similarly employs the Boudouard reaction: C + CO₂ → 2CO, promoting micropore development. The reaction rates increase with temperature, typically requiring 1–3 hours of exposure to achieve optimal porosity, and nitrogen gas may be used as a carrier to enhance uniformity.^[32]^[33] Chemical activation, in contrast, involves impregnating the precursor with chemical agents before or after carbonization, followed by heating at lower temperatures of 400–800°C and subsequent washing to remove residues. Common agents include potassium hydroxide (KOH) at 700–900°C, phosphoric acid (H₃PO₄) at around 500°C, and zinc chloride (ZnCl₂) above 500°C; these facilitate dehydration, oxidation, and cross-linking reactions that create interconnected pores by volatilizing non-carbon elements and intercalating into the carbon matrix. For example, KOH reacts to form potassium carbonate and releases gases like CO₂, while H₃PO₄ promotes phosphorylation and ether bond cleavage, yielding surface areas up to 2800 m²/g after neutralization. The process often uses a biomass-to-agent mass ratio of 1:1 to 1:4, with yields ranging from 26–85% depending on the agent and conditions.^[31]^[34] Physical activation tends to produce larger pores suitable for granular activated carbon (GAC) applications, operating at higher energy inputs due to elevated temperatures but avoiding chemical residues for environmental benefits. Chemical activation achieves higher surface areas and microporosity ideal for powdered activated carbon (PAC), with greater energy efficiency from lower temperatures and shorter times, though it requires additional washing steps; yields are calculated as (mass of activated carbon / mass of precursor) × 100%, often higher in chemical methods (30–50%) compared to physical (20–40%). Selection depends on desired pore size distribution and precursor type, with chemical methods offering more control over hierarchical porosity.^[34]^[31]

Classification

Powdered Activated Carbon (PAC)

Powdered activated carbon (PAC) consists of fine particles typically smaller than 0.18 mm, equivalent to 50–100 mesh size, which allows for rapid mixing and contact with target substances. This form of activated carbon possesses a high specific surface area, generally ranging from 1000 to 1500 m²/g, enabling substantial adsorption capacity for organic compounds. PAC is manufactured by first activating carbonaceous raw materials through processes such as carbonization followed by activation, and then subjecting the product to fine grinding or pulverization to achieve the desired particle size. Chemical activation methods, involving agents like phosphoric acid or zinc chloride, are often preferred for PAC production due to their ability to develop extensive microporosity suited for quick adsorption kinetics. In water treatment applications, PAC is dosed at concentrations typically between 1 and 100 mg/L, depending on the contaminant levels and treatment objectives, such as addressing seasonal taste and odor issues. Its fine particle nature facilitates swift dispersion in batch processes, providing immediate adsorption effects without the need for fixed-bed systems, though this also makes handling more challenging due to dust generation and the requirement for subsequent filtration or sedimentation to remove spent carbon. While PAC offers high adsorption capacity for organics, its single-use nature in temporary treatments limits regeneration options compared to other forms. These characteristics make PAC particularly suitable for intermittent or emergency applications in drinking water purification, where rapid deployment for taste and odor control is essential, though careful dosing is required to avoid impacts on downstream processes like disinfection.

Granular Activated Carbon (GAC)

Granular activated carbon (GAC) is a coarse form of activated carbon characterized by irregular particles ranging from 0.2 to 5 mm in diameter, equivalent to 8 to 30 mesh sizes, which allows for effective packing in fixed-bed systems.^[17] Its specific surface area typically falls between 700 and 1200 m²/g, providing substantial adsorption sites while maintaining structural integrity.^[35] For optimal hydraulic performance, GAC has an effective particle size of 0.6 to 2.5 mm and a uniformity coefficient less than 2.5, ensuring even flow distribution and minimal channeling.^[36] Production of GAC favors physical activation processes, such as steam or CO₂ gasification at high temperatures (around 800–1000°C), to develop porosity while preserving mechanical durability and hardness essential for long-term use in dynamic flow environments.^[37] This method contrasts with chemical activation by avoiding residues that could compromise strength, resulting in robust granules suitable for column-based continuous filtration without rapid attrition. In applications, GAC excels in fixed-bed columns for water treatment, particularly dechlorination, where an empty-bed contact time of 5 to 10 minutes achieves effective chlorine removal through catalytic reduction.^[38] Pressure drop across the bed is governed by Darcy's law, expressed as \Delta [P](/page/P′′) = \frac{\mu L [Q](/page/Q)}{k A}, where flow rate Q inversely affects head loss \Delta [P](/page/P′′) relative to bed depth L, guiding design for balanced throughput and energy efficiency.^[39] Adsorption capacity is often evaluated via the iodine number, typically exceeding 900 mg/g for high-quality GAC.^[40]

Extruded Activated Carbon (EAC)

Extruded activated carbon (EAC) is a molded form of activated carbon created by combining powdered carbon precursor with a binder and extruding it into rigid cylindrical pellets, typically 1–5 mm in diameter, which provides enhanced structural integrity for specialized filtration tasks. This shape distinguishes EAC from irregularly shaped granular forms, enabling uniform packing and reduced channeling in fixed-bed systems. The use of binders such as coal tar pitch or other organic materials like tars and resins ensures cohesion during forming, resulting in a product with superior rigidity compared to unbound powders or granules.^[41]^[42]^[43] The production of EAC begins with mixing a carbonized char—derived from raw materials like coal, coconut shells, or wood—with the binder to form a dough-like paste, which is then forced through an extruder die to produce continuous cylindrical extrudates. These extrudates are dried and cut to length before undergoing activation, often via steam or chemical methods at high temperatures (800–1000°C), to develop the extensive microporous structure essential for adsorption. This sequence—mixing, extrusion, and post-forming activation—yields a low-dust product with high mechanical strength, characterized by abrasion loss below 2% as measured by ball-pan hardness tests exceeding 98%. The resulting pellets exhibit minimal friability, making EAC ideal for dynamic environments where particle breakdown could generate contaminants.^[44]^[45]^[46] EAC's design offers lower flow resistance than granular activated carbon (GAC) due to its uniform cylindrical geometry, which minimizes pressure drop in gas streams while maintaining efficient contact time for adsorbates. This property, combined with its low dust emission, makes EAC particularly suitable for gas-phase applications such as air purification and solvent recovery in industrial processes like vapor extraction from chemical manufacturing. In respiratory protection, such as gas masks, EAC's durability and negligible dust generation ensure reliable performance without risking inhalation hazards. Additionally, EAC can be impregnated with chemicals to boost reactivity for targeted pollutant removal, though this is addressed in dedicated modification techniques.^[46]^[47]^[48]

Bead Activated Carbon (BAC)

Bead activated carbon (BAC) consists of spherical particles typically ranging from 0.3 to 3 mm in diameter, offering uniform size distribution that minimizes channeling in adsorption systems.^[49] This spherical morphology, combined with a bulk density of 0.4–0.6 g/cm³, enhances packing efficiency and flow characteristics compared to irregular shapes.^[50] The beads exhibit high mechanical strength, with abrasion resistance often below 0.7%, ensuring durability in dynamic environments.^[50] BAC is produced through polymerization or emulsion techniques using carbon-rich precursors such as petroleum pitch, phenolic resins, or cross-linked polystyrene.^[49] The process begins with forming spherical precursors via suspension or emulsion polymerization, followed by carbonization at 700–900°C and activation—either physical (using steam or CO₂) or chemical (with KOH or H₃PO₄)—to develop a porous structure with surface areas typically up to 2000–2200 m²/g.^[51] This integrated method avoids binders, resulting in beads with consistent pore development suited for adsorption.^[50] The primary advantages of BAC include superior fluidity in moving or fluidized beds, which facilitates uniform contact with fluids and reduces pressure drops.^[49] Its uniform particle size prevents preferential flow paths, improving overall adsorption efficiency.^[50] In gold recovery, BAC is employed in the carbon-in-pulp (CIP) process, where beads of 1.7–3.35 mm size adsorb gold-cyanide complexes from leached pulp, leveraging high hardness and abrasion resistance for repeated cycling through mixing, pumping, and regeneration stages.^[52]

Impregnated and Coated Carbons

Impregnated activated carbons are produced by soaking a base activated carbon substrate, such as granular or powdered forms, in solutions containing chemical agents to enhance specific reactivity or selectivity.^[53] This impregnation process introduces active compounds that catalyze reactions or improve adsorption for targeted pollutants, with typical loading levels ranging from 5 to 15 wt% depending on the agent and application.^[54] Common impregnants include silver for antibacterial properties, where silver ions disrupt microbial cell walls, making it effective against pathogens like E. coli in water treatment systems. Similarly, potassium iodide (KI) impregnation facilitates hydrogen sulfide (H₂S) removal by oxidizing H₂S to elemental sulfur or sulfate under humid conditions, outperforming untreated carbon in biogas purification.^[55] Copper oxide (CuO) impregnation targets formaldehyde, promoting its catalytic decomposition to CO₂ and water in indoor air filtration, with enhanced performance at low concentrations.^[56] Coated activated carbons involve surface modification with thin layers of polymers to tailor adsorption properties, often applied via dip-coating or chemical grafting on the carbon substrate. Chitosan, a natural polysaccharide, is a widely used coating that introduces amino and hydroxyl groups, boosting hydrophilicity and enabling selective adsorption of heavy metals like lead (Pb²⁺) through chelation mechanisms in wastewater treatment.^[57] This modification increases water affinity compared to hydrophobic base carbons, improving contact efficiency and regeneration potential while maintaining high surface area.^[58] Woven activated carbon, typically in cloth form from carbonized and activated fibers, provides a flexible matrix for filtration applications, with activation often performed after weaving to preserve structural integrity. This form is particularly suited for respirators and protective gear, where its microporous structure adsorbs vapors, toxins, and particulates rapidly, offering lightweight alternatives to granular beds.^[59] Catalytic impregnation extends to nitrogen oxides (NOx) reduction, where metals like copper or iron are loaded onto activated carbon to promote selective catalytic reduction (SCR) with ammonia or hydrocarbons, achieving up to 90% NOx conversion at low temperatures (100-200°C) in exhaust streams.^[60] These impregnated variants outperform standard carbons by facilitating redox reactions on the metal sites, minimizing secondary emissions like N₂O.^[53]

Properties

Physical Properties

Activated carbon exhibits a highly porous structure that results in exceptionally high specific surface areas, typically measured by the Brunauer-Emmett-Teller (BET) method using nitrogen adsorption at 77 K.^[61] This surface area generally ranges from 500 to 1500 m²/g for commercial forms, though advanced activation processes can achieve values up to 3000 m²/g, enabling extensive adsorption sites within a compact material volume.^[62]^[63] The associated total pore volume, also derived from BET analysis, typically spans 0.5 to 1.5 cm³/g, distributed across micropores (<2 nm), mesopores (2–50 nm), and macropores (>50 nm), which collectively define the material's accessibility for adsorbates.^[64] Density properties of activated carbon reflect its porous architecture. The true (skeletal) density, excluding all pores, is approximately 2.0–2.1 g/cm³, akin to that of pure carbon materials.^[65] In contrast, the apparent density, which includes the volume of closed pores but excludes interparticle voids, ranges from 0.3 to 0.6 g/cm³, varying with the degree of activation and precursor type.^[66] Bulk density, the mass per unit volume of a packed bed including interparticle spaces, is lower still at 0.25–0.55 g/cm³ and is particularly sensitive to particle size and shape, influencing handling and bed design in applications.^[67] Particle size distribution is a critical physical attribute, commonly determined through sieve analysis according to standards like ASTM E11, which classifies particles by mesh size.^[68] For granular activated carbon, typical distributions include ranges such as 8×30 mesh (0.60–2.36 mm) or 12×40 mesh (0.425–1.70 mm) in U.S. sieve nomenclature, while powdered forms are finer, often below 0.18 mm.^[65] These distributions directly impact hydraulic flow resistance in fixed beds and the rate of adsorption kinetics, with smaller particles offering faster diffusion but higher pressure drops.^[69] The overall low bulk density arises from the extensive pore network, which occupies a significant fraction of the material's volume.^[65]

Adsorption Capacity Metrics

The adsorption capacity of activated carbon is evaluated through standardized tests that quantify its ability to adsorb specific molecules, providing insights into pore structure and suitability for various applications. These metrics focus on the carbon's microporous and mesoporous volumes, which determine its effectiveness in removing contaminants from liquids and gases.^[70] The iodine number is defined as the milligrams of iodine adsorbed per gram of activated carbon under standardized conditions where the residual iodine concentration in solution reaches 0.02 N. This metric primarily measures the content of micropores (pores smaller than 2 nm), which are crucial for adsorbing small molecules, and typical values range from 500 to 1200 mg/g, corresponding to surface areas of approximately 900 to 1100 m²/g. Higher iodine numbers indicate greater microporosity and are commonly used to assess carbons for water and air purification.^[71]^[70] The molasses number measures the decolorization efficiency of activated carbon on a standard molasses solution compared to a reference, where higher numbers indicate greater capacity for adsorbing larger organic molecules via mesopores (2-50 nm), with typical values ranging from 95 to 600 for commercial products optimized for decolorization tasks like sugar refining.^[72] The methylene blue number quantifies the milligrams of methylene blue dye adsorbed per gram of activated carbon, serving as an indicator of pore sizes greater than 1.5 nm, particularly mesopores suitable for larger dye molecules and organic pollutants. This test is valuable for evaluating carbons in wastewater treatment, where values often exceed 100 mg/g for high-performance materials.^[73] Carbon tetrachloride (CTC) activity is expressed as the percentage of CTC adsorbed by the carbon sample relative to its weight, under controlled vapor phase conditions, and it evaluates the capacity for non-polar organic compounds. Typical commercial values range from 20% to 90%, with higher percentages denoting enhanced adsorption for volatile organics in air filtration applications.^[74]

Mechanical and Chemical Properties

Activated carbon exhibits significant mechanical durability, primarily assessed through its hardness or abrasion resistance, which is crucial for applications involving mechanical stress such as fluidized bed reactors. The ball-pan hardness test, standardized under ASTM D3802, involves subjecting a screened sample of granular activated carbon to agitation with steel balls in a pan for 30 minutes, followed by sieving to measure the percentage of material retained on a mesh with openings half the size of the original sample's minimum particle size. Typical hardness numbers for high-quality activated carbons range from 95% to 98% retention, indicating minimal degradation and suitability for demanding processes where attrition could otherwise lead to particle breakdown and reduced performance.^[75]^[76] Chemically, activated carbon contains ash as inorganic residues derived from the raw materials and activation process, typically comprising metal oxides and salts that remain after high-temperature treatment. Ash content generally falls within 3–10% by weight for many commercial grades, influencing the material's purity and potential interference in adsorption applications; higher levels can introduce impurities that affect water quality or catalytic activity. These residues originate from minerals in precursors like coal or wood, and low-ash variants are preferred for sensitive uses to minimize secondary contamination.^[77]^[78] The surface chemistry of activated carbon is characterized by its pH and diverse functional groups, which dictate interactions with adsorbates. The pH at the point of zero charge (pH_ZPC) typically ranges from 7 to 10, below which the surface becomes positively charged due to protonation of basic sites, and above which it is negatively charged from deprotonation of acidic groups. Acidic functional groups, such as carboxyl (-COOH) and phenolic (-OH), predominate on oxidized surfaces and enhance selective adsorption of cationic species like heavy metals through electrostatic attraction, while basic groups like pyrones and chromenes favor anionic pollutants.^[79] A key chemical property is the dechlorination capability, where activated carbon catalytically reduces free chlorine species in water via redox reactions. The primary reaction involves hypochlorous acid (HOCl) reacting with the carbon surface: HOCl + C → H⁺ + Cl⁻ + CO, converting chlorine to harmless chloride ions while oxidizing the carbon. Dechlorination half-value length, the bed depth required to reduce chlorine concentration by 50%, typically ranges from 1 to 3 inches for high-quality carbons under standard test conditions (e.g., 2 mg/L chlorine at neutral pH and specified flow rate per AWWA B604).^[80]^[81]^[82]

Modification and Reactivation

Property Modifications

Property modifications of activated carbon involve post-production techniques to customize its physical structure, surface chemistry, and reactivity for targeted applications such as enhanced adsorption or catalysis. These methods allow tailoring of pore size distribution, introduction of functional groups, and integration of nanomaterials without altering the core production process. Physical and chemical approaches are commonly employed, often in combination, to optimize performance metrics like selectivity and capacity.^[83] Physical modifications primarily adjust particle morphology and porosity. Grinding and sieving reduce particle size to improve accessibility and flow dynamics in applications like water filtration; for instance, ball milling of granular activated carbon can decrease median particle diameter to 140-190 μm while increasing surface oxygen content by up to 34%, thereby enhancing adsorption kinetics for organic contaminants. Steam treatment serves as a post-activation step to widen micropores and increase overall pore volume, resulting in expanded internal surface area and improved gas permeation rates, such as for helium and carbon dioxide in membrane separations. These changes maintain structural integrity while boosting throughput without compromising selectivity.^[84]^[85] Chemical modifications focus on surface functionalization to introduce specific reactive sites. Oxidation with nitric acid (HNO₃) generates oxygen-containing groups like carboxyl and phenolic moieties, increasing surface acidity and hydrophilicity; this enhances adsorption of cationic heavy metals such as Cu(II) and Pb(II) through complexation, though it may slightly reduce specific surface area by 9-10%. Amine grafting, often via ammonia treatment at 400-900°C or impregnation with amine compounds, incorporates nitrogen functionalities like pyrrolic and pyridinic groups, promoting basic sites for CO₂ capture through acid-base interactions.^[86]^[83] Advanced techniques integrate nanotechnology and doping to achieve superior properties. Metal doping, such as loading palladium (Pd) at 5-10 wt% via impregnation, enhances catalytic reactivity for hydrogenation reactions like nitrobenzene reduction, leveraging spillover effects for efficient H₂ activation and selectivity ratios like H₂/N₂ up to 40 at room temperature. Templating methods, including soft or hard templates combined with activation, enable ultrahigh surface areas exceeding 3000 m²/g; a notable example yields 4800 m²/g through hypergolic reactions and KOH activation of biomass precursors, significantly boosting CO₂ adsorption and energy storage capacities. These modifications, including nanoparticle dispersion for heterogeneous catalysis, prioritize scalability and environmental compatibility as of 2025.^[87]^[88]

Reactivation Techniques

Thermal reactivation is the most established method for restoring the adsorption capacity of spent activated carbon, involving high-temperature treatment in the presence of steam or carbon dioxide to desorb and gasify adsorbed contaminants. The process typically heats the carbon to 800–950°C in a controlled atmosphere, such as a rotary kiln, where steam injection facilitates the removal of organic adsorbates through volatilization and subsequent gasification reactions. For instance, the primary gasification reaction with steam is C + H₂O → CO + H₂, which converts residual carbon-bound contaminants into gaseous products, achieving 75–90% recovery of the original adsorption capacity depending on the contaminant type and process conditions.^[89]^[90] Similarly, CO₂ can be used as the activating agent via the Boudouard reaction, C + CO₂ → 2CO, which is effective for oxidizing and removing persistent organic residues without excessive carbon loss. This method is widely applied in industrial settings for water treatment carbons, though it requires significant energy input and specialized equipment to minimize unwanted carbon burn-off.^[90] Chemical regeneration offers a lower-energy alternative to thermal methods, focusing on solvent extraction or acid washing to desorb contaminants without high temperatures. In solvent extraction, organic solvents like ethanol are used to dissolve and remove adsorbed organics, such as pesticides or hydrocarbons, achieving desorption efficiencies exceeding 99% in some cases for specific compounds like MCPA. Acid washing, often with nitric acid or hydrochloric acid, targets inorganic or polar contaminants by protonation and solubilization, providing partial recovery of adsorption sites while being less disruptive to the carbon's porous structure. These techniques are particularly suitable for laboratory or small-scale applications but typically yield only 50–80% overall capacity restoration due to incomplete removal of strongly bound adsorbates, and they generate liquid waste that requires proper disposal.^[91]^[92]^[93] Electrochemical reactivation represents another energy-efficient approach, applying an electric potential to desorb contaminants through oxidation or reduction reactions at electrodes in contact with the carbon. This method operates at ambient temperatures and pressures, achieving regeneration efficiencies of 70-85% for organics like phenol, with lower energy consumption (e.g., 10-20 kWh/kg carbon) compared to thermal processes. It is suitable for granular activated carbon in flow-through reactors but faces challenges like electrode fouling and limited scalability for high-volume industrial use as of 2025.^[94]^[95] Biological regeneration, an emerging approach in the 2020s, utilizes microbial degradation to break down low-concentration organic pollutants adsorbed on activated carbon, leveraging bacteria or fungi to metabolize contaminants directly on the carbon surface. Microorganisms such as Pseudomonas species can be immobilized on the carbon, where they enzymatically degrade recalcitrant organics like surfactants or pharmaceuticals under ambient conditions, restoring 60–90% of adsorption capacity over extended periods without thermal or chemical inputs. This method is eco-friendly and cost-effective for dilute effluents but is slower than thermal processes and best suited for biodegradable pollutants, with ongoing research focusing on optimizing microbial consortia for broader applicability.^[96]^[97] Economically, reactivation techniques significantly extend the operational life of activated carbon, allowing 3–5 reuse cycles before replacement is necessary due to cumulative capacity loss. However, each cycle incurs attrition losses of 5–10% from mechanical wear and partial oxidation, necessitating periodic replenishment of carbon inventory in large-scale systems. These factors make reactivation viable for reducing overall costs by up to 50% compared to virgin carbon use, particularly in continuous processes like wastewater treatment.^[98]^[99]

Applications

Environmental and Water Treatment

Activated carbon plays a crucial role in environmental remediation and water treatment, primarily through adsorption processes that capture contaminants from aqueous and gaseous streams. In water purification, granular activated carbon (GAC) is widely employed in fixed-bed filters to remove organic pollutants such as pesticides, volatile organic compounds (VOCs), and disinfection byproducts. This adsorption mechanism relies on the carbon's high surface area, which attracts non-polar organics via van der Waals forces, effectively reducing concentrations to meet potable water standards. Additionally, GAC catalytically reduces chlorine residuals and mitigates taste, odor, and color issues caused by natural organic matter. Typical designs incorporate empty bed contact times (EBCT) of 10–30 minutes for optimal organics removal, ensuring sufficient interaction between water and the carbon bed.^[82]^[100]^[101] For air purification, activated carbon filters VOCs and odors from industrial emissions and indoor environments, often integrated into systems like HVAC units or exhaust treatments. In personal protective equipment, such as gas masks, impregnated variants enhance selectivity; for instance, carbons treated with potassium hydroxide or triethylenediamine target alkaline gases like ammonia (NH₃), while those impregnated with copper or zinc oxides address hydrogen sulfide (H₂S) through chemisorption. These modifications allow for efficient removal of specific gases in high-concentration scenarios, such as wastewater treatment plants or chemical handling facilities.^[102]^[103] In broader environmental remediation, sulfur-impregnated activated carbon is used for mercury scrubbing in flue gas streams, where elemental mercury vapor binds chemically to the sulfur, achieving removal efficiencies exceeding 90% under controlled conditions. For soil vapor extraction (SVE) at contaminated sites, vapor-phase activated carbon treats off-gases extracted from unsaturated soils, adsorbing VOCs and semi-volatiles to prevent atmospheric release during in-situ cleanup. This application is common in Superfund sites, where carbon units serve as a polishing step post-extraction.^[104]^[105] Regulatory frameworks, stemming from the 1974 Safe Drinking Water Act (SDWA), have increasingly mandated activated carbon use for contaminant control, with significant updates in 2024 establishing national primary drinking water standards for per- and polyfluoroalkyl substances (PFAS). The U.S. Environmental Protection Agency (EPA) designates GAC as a best available technology for PFAS removal, targeting limits of 4 parts per trillion for PFOA and PFOS, alongside standards for four additional PFAS compounds. These rules require public water systems to complete initial monitoring for PFAS by 2027 and achieve compliance with maximum contaminant levels (MCLs) by 2029, promoting GAC adsorption as a cost-effective compliance method that also addresses co-occurring organics, though as of May 2025, the EPA has proposed extending the compliance deadline for PFOA and PFOS to 2031.^[106]^[107]

Medical and Analytical Uses

Activated carbon serves as a critical agent in medical toxicology for treating acute poisonings by adsorbing toxins in the gastrointestinal tract, preventing their absorption into the bloodstream. In cases of overdose involving alkaloids such as strychnine or tropane alkaloids, a single oral dose of 50 to 100 grams of activated carbon is commonly administered to adults to bind and eliminate these substances via fecal excretion.^[108]^[109] Similarly, for pesticide poisonings such as those from carbamates, activated carbon may be considered for gastrointestinal decontamination, with recommended doses of 1 gram per kilogram of body weight if ingestion occurred within one hour, though its efficacy is disputed; it is less effective for organophosphates.^[110]^[108] This adsorption primarily occurs through non-specific physical interactions, such as van der Waals forces, between the toxin's molecules and the carbon's porous surface.^[108] Despite its efficacy, activated carbon is non-digestible and inert, passing through the digestive system without being metabolized or absorbed, which minimizes secondary risks in most cases.^[111] However, it is contraindicated in poisonings involving hydrocarbons, such as petroleum distillates, as it may interfere with endoscopic evaluation and does not mitigate their inherent toxicity.^[112] In analytical chemistry, activated carbon is widely employed as a sorbent in solid-phase extraction (SPE) techniques to preconcentrate trace analytes from complex matrices, enhancing detection sensitivity. For heavy metals like cadmium, cobalt, copper, nickel, lead, and zinc in environmental or biological samples, modified activated carbon enables efficient separation and enrichment at trace levels prior to instrumental analysis.^[113] It also supports the extraction of organic compounds, including volatile organic hydrocarbons and other pollutants, by adsorbing them onto its high-surface-area structure for subsequent elution and quantification via methods like gas chromatography-mass spectrometry.^[114]^[115] Beyond toxicology and analysis, activated carbon plays a key role in the purification of distilled beverages, where it is used for decolorization during vodka and whiskey production to remove impurities, colorants, and off-flavors from the distillate.^[116] This process improves clarity and sensory quality without altering the alcohol content, typically involving passage through activated carbon beds or filters.^[117]

Industrial and Energy Storage Applications

In the mining industry, activated carbon plays a crucial role in gold recovery processes, particularly through the carbon-in-leach (CIL) method, where gold-cyanide complexes are adsorbed directly from the leaching solution onto the carbon surface.^[118] This process enhances efficiency by combining leaching and adsorption in a single step, allowing for higher gold yields compared to traditional methods.^[52] The adsorption behavior is often modeled using the Freundlich isotherm, expressed as q = K C^{1/n}, where q is the amount of gold adsorbed per unit mass of carbon, C is the equilibrium concentration in solution, K is the Freundlich constant, and $1/n indicates adsorption intensity; this model fits well for gold loading on activated carbon from cyanide solutions.^[119] Beyond mining, activated carbon is widely employed in chemical purification across industries, where it removes impurities, colors, and odors from liquid products such as solvents, pharmaceuticals, and petrochemicals through selective adsorption.^[120] Its high surface area and tunable pore structure make it effective for decolorizing and deodorizing bulk chemicals, ensuring compliance with quality standards in manufacturing.^[121] In fuel storage applications, activated carbon serves as an adsorbent for natural gas, particularly methane, enabling storage at moderate pressures around 30 bar with capacities up to 0.32 g-CH₄/g-carbon in optimized materials.^[122] This approach supports compressed natural gas vehicles by increasing volumetric storage efficiency without requiring extreme conditions.^[123] Activated carbon also functions as a support in heterogeneous catalysis, providing a stable, high-surface-area matrix for metal catalysts in reactions such as selective oxidation of hydrocarbons or alcohols.^[124] For instance, impregnation with transition metals like copper or cobalt enhances its activity in wet oxidation processes for wastewater treatment, achieving significant chemical oxygen demand reduction.^[125] In environmental catalysis, sulfur-impregnated activated carbon is used for mercury scrubbing in coal-fired power plant flue gases, capturing elemental and oxidized mercury with efficiencies exceeding 90% through chemisorption.^[126] This application integrates with existing flue gas treatment systems, minimizing emissions in compliance with regulations.^[127] In energy storage, activated carbon electrodes enable electrochemical double-layer capacitors (EDLCs), or supercapacitors, by storing charge via ion adsorption at the electrode-electrolyte interface, with specific capacitances reaching up to 300 F/g in aqueous electrolytes due to optimized micropore structures.^[128] These devices offer high power density and rapid charge-discharge cycles, making them suitable for applications like regenerative braking in vehicles.^[129] As anodes in lithium-ion batteries, activated carbon provides stable cycling with reversible capacities around 750 mAh/g at moderate rates, leveraging its conductivity and ability to accommodate lithium intercalation without significant volume expansion.^[130] Advancements as of 2025 have focused on high-density hybrid systems combining activated carbon with pseudocapacitive materials, achieving energy densities over 100 Wh/kg in lithium-ion hybrid capacitors through enhanced ion transport and surface functionalization.^[131] Nanotechnology enhancements, such as incorporating graphene or metal oxides into activated carbon matrices, have pushed EDLC capacitances to 500 F/g by improving pore accessibility and electrical conductivity, addressing limitations in traditional double-layer storage.^[132] These hybrids bridge the gap between batteries and supercapacitors, enabling scalable, sustainable energy solutions.^[133]

Other Specialized Uses

In agriculture, activated carbon serves as a soil amendment to enhance pesticide adsorption, thereby reducing the mobility and bioavailability of these chemicals in the soil and minimizing their uptake by crops.^[134] This application is particularly valuable in remediating contaminated sites, where activated carbon binds persistent organic pollutants like insecticides, preventing leaching into groundwater.^[135] Additionally, activated carbon is incorporated as a feed additive in animal husbandry to mitigate toxin exposure, such as aflatoxins produced by molds in livestock feed, by adsorbing these mycotoxins in the gastrointestinal tract and reducing their absorption.^[136] Studies have shown that such supplementation can lower aflatoxin toxicity in dairy cows without adversely affecting nutrient intake.^[137] In the food industry, activated carbon functions primarily as a decolorizing and purifying agent during processing. It is employed in sugar refining to remove color impurities from raw sugar solutions, improving clarity and yield through selective adsorption of non-sugar organic compounds.^[138] Vegetable carbon, a specialized form of activated carbon derived from plant sources, is approved as the food additive E153 for imparting a black color to products like confectionery and bakery items, where it acts as a natural pigment without nutritional impact.^[139] Activated carbon's adsorptive properties also extend briefly to wine stabilization, where it targets tannin adsorption to adjust astringency and color stability in select formulations.^[140] Activated carbon plays a key role in smoking filtration systems, particularly in cigarette filters, where it captures volatile organic compounds, tar, and nicotine from mainstream smoke. Charcoal-integrated filters can reduce gas-phase radicals by up to 40% and carbonyl compounds by nearly 99% at higher loadings, compared to standard cellulose acetate filters.^[141]^[142] Woven activated carbon fabrics are utilized in advanced traps and mouthpieces for pipes or electronic cigarettes, providing a porous matrix that enhances the retention of harmful particulates and odors during inhalation.^[143] Emerging applications of activated carbon include its use in cosmetics, such as detoxifying face masks, where the material's high surface area draws out impurities, excess oil, and toxins from pores for skin clarification.^[144] In biofuel production, activated carbon facilitates purification by adsorbing residual contaminants like heavy metals and color bodies from biodiesel, enhancing fuel quality and meeting regulatory standards for clarity and stability.^[145] For instance, carbons derived from agricultural wastes, such as cocoa pods, have demonstrated effective removal of impurities in pre-treatment stages.^[146]

References

[1]
An Evaluation of Activated Carbon for Drinking Water Treatment
The subcommittee defined ''activated carbon" as a family of carbonaceous substances that are characterized primarily by their surface area, pore size ...
[2]
None
### Summary of Activated Carbon Processing
[3]
Activated Carbon
Activated carbon is useful in drinking water treatment because it acts as an adsorbent, and can effectively remove particles and organics from water.
[4]
Charcoal: From antiquity to artificial kidney - ResearchGate
Aug 9, 2025 · According to Herodotus, the use of charcoal was introduced in ancient Egypt; however only in 1773 Carl Willhelm Scheele utilized it for ...
[5]
(PDF) History, Method of Production, Structure and Applications of ...
Activated charcoal is non-graphitic and non graphitizable carbon with a disordered microstructure. It has high potential for adsorption due to its high surface ...
[6]
[PDF] Water and Wastewater Treatment: Historical Perspective of Activated ...
Jul 7, 2011 · In 1811 it was shown that bone char had an even higher decolorizing ability for sugar syrups than wood char. Consequently, a switch took place ...Missing: Johann | Show results with:Johann
[7]
Some intriguing items in the history of adsorption - Academia.edu
Charcoal was recommended as an antidote. Based on Lowitz' discovery of the decolorizing effect in 1785, charcoal was used for the purification first of sugar.
[8]
[PDF] history-method-of-production-structure-and-applications-of-activated ...
In 20th century Ostrejko et al [1900] developed commercial activated carbon through two processes (a) Use of metal chlorides before carbonization. (b) Using ...
[9]
Chemical Technology and Economics in Environmental Perspectives
During World War I, extensive interest in activated carbon developed for use in gas masks as protection against gas warfare. ... Few companies used the activated ...
[10]
25 Years of the Safe Drinking Water Act: History and Trends
One of these laws was the Safe Drinking Water Act (SDWA) of 1974. That ... activated carbon adsorption (for removal of organic contaminants). In the ...Missing: WWII | Show results with:WWII
[11]
A comprehensive insight on activated carbon production from ...
Biomass-derived AC (BDAC) is an eco-friendly alternative to traditional AC, adding value to agricultural waste and supporting sustainable technologies. However, ...
[12]
Research - Math@LSU
Just one gram of activated carbon has a surface area of approximately 500 m². ... This total exposed surface will typically be in the range of 600-1200 m2/g.
[13]
https://www.math.lsu.edu/clinic/4020clinic/GACSP08/RESEARCH.htm
[14]
Ultrahigh Surface Area Three-Dimensional Porous Graphitic Carbon ...
Traditional porous carbon materials, such as activated carbons (ACs), have high surface area (up to 3000 m2/g), but their large pore tortuosity and poor pore ...Missing: m2/ | Show results with:m2/
[15]
The Analysis of Pore Development and Formation of Surface ... - NIH
Activated carbon is an amorphous carbon-based material which exhibits a high degree of porosity, an extended surface area, microporous structure, high ...
[16]
[PDF] adsorption of synthetic organic chemicals: a ... - Clemson OPEN
2.1.2 Structure of Activated Carbon. Activated carbons have a microcrystalline structure, which is rigidly interconnected and consist of a stack of graphitic ...
[17]
Hydrogen Storage in Pure and Boron-Substituted Nanoporous ...
Aug 25, 2021 · Model activated carbons, based on assemblies of graphitic micro-crystallites containing from 56 to 212 carbon atoms, have been proposed by ...
[18]
[PDF] Lignin Based Activated Carbon Using H3PO4 Activation
Nov 28, 2020 · According to the IUPAC classification, the pore diameter of micropores are less than 2 nm, mesopores 2–50 nm, and macropores > 50 nm.
[19]
Activated Porous Carbon Derived from Tea and Plane Tree Leaves ...
Jan 11, 2021 · The structure of activated carbon can be separated into micropores, mesopores, and macropores, with pore widths less than 2 nm, between 2 ...
[20]
Surface Area Estimation: Replacing the Brunauer–Emmett–Teller ...
Surface area estimation using the Brunauer–Emmett–Teller (BET) analysis has been beset by difficulties. The BET model has been applied routinely to systems ...
[21]
Effect of synthesis conditions on the porous texture of activated ... - NIH
Jan 27, 2024 · During this process, volatiles are removed and char is consequently enriched in elemental carbon. The efficiency of the carbonisation ...
[22]
[PDF] porosity and specific surface area measurements for solid materials
Some materials are consolidated; i.e., distinguishable microscopic particles are bound together in some manner to form a relatively rigid, macroscopic body.
[23]
A Review of Bio-Based Activated Carbon Properties Produced from ...
Nov 27, 2023 · These properties make it ideal for a wide range of applications, such as water purification, gas separation, and catalysis. In addition to its ...Missing: definition | Show results with:definition
[24]
Activated carbon from biomass - NASA ADS
Most commonly used on a commercial scale are cellulosic based precursors such as peat, coal, lignite wood and coconut shell. Variation occurs in precursors in ...
[25]
[PDF] Certain Activated Carbon from China - usitc
Nov 2, 2023 · surface area and pore structure of activated carbon depend greatly on the raw materials and processing methods used. The primary use for ...
[26]
Activated carbon as catalyst support: precursors, preparation ... - BJOC
Jun 2, 2020 · After preparation of char by carbonization of the precursor materials for a certain time at a defined temperature under inert gas atmosphere, ...
[27]
[PDF] Industrial Crops and Products - CDC Stacks
The highest BET surface area of activated carbon obtained at 650 ◦C with ... (b) Effects of flow rates on Brunauer, Emmett, Teller surface area. et al ...
[28]
Analysis of environmental impact of activated carbon production ...
Jun 27, 2018 · The results showed that the activated carbon system using one tonne of wood wastes has an environmental benefit of 163 kg CO2-eq. for reducing ...
[29]
Physical Activation of Rice Husk Pyrolysis Char for the Production of ...
Jul 2, 2015 · They then used KOH as activating agent to obtain active carbons of high quality, with the maximum surface area being 1936 m2 g–1.
[30]
https://pubs.acs.org/doi/10.1021/acs.iecr.5b01589
[31]
https://doi.org/10.3390/ma16237365
[32]
https://doi.org/10.1515/revce-2017-0113
[33]
https://doi.org/10.3390/ma16196558
[34]
[PDF] Granular Activated Carbons from Agricultural By-products
Jan 2, 2000 · Surface area is the single most important characteristic of activated carbon designed for adsorption of compounds from liquid media such as ...
[35]
Rule 3701-28-15 - Ohio Administrative Code | Ohio Laws
The effective sand size shall be between .30 and .45 millimeters. The sand uniformity coefficient shall not be greater than 2.5. (a) Granular activated carbon ...
[36]
Process Design Manual Carbon Adsorption - epa nepis
... Granular Activated Carbon Treatment Cost 5-24 5-7A Estimated Granular ... Activated carbon can be manufactured by two different procedures: physical activation ...
[37]
Activated carbon replacement frequency - Carbotecnia
After chlorination, the water is treated in a tank with granular activated carbon, with an empty bed contact time of 5 min, for eight hours per day, six days ...
[38]
[PDF] Modeling Flow through a Fixed Bed Packed Reactor - ResearchGate
Granular activated carbon (GAC) is ... The solutions obtained for pressure drop across the fixed bed are consistent with hand-calculations for Darcy's Law.Missing: depth | Show results with:depth
[39]
Activated Carbon Treatment for Drinking Water Supplies : CAFE
Jun 1, 2007 · Granular activated carbon (GAC) treatment is most common for private water systems. ... The iodine number is defined as the amount of ...
[40]
Introduction to Activated Carbon - FEECO International
Many applications will require the activated carbon to have a high particle strength and a resistance to attrition (the breakdown of material into fines).
[41]
Columnar Activated Carbon Production Process
Oct 15, 2025 · The selected raw material is crushed into fine powder, then mixed with a binder such as pitch or tar. The binder ensures proper adhesion and ...
[42]
Whey as a sustainable binder for the production of extruded ...
Binders for this purpose can be either inorganic (clays) or organic (pitches, tars, and resins). Binders are thus essential in the production of extruded ACs.
[43]
(PDF) Whey as a sustainable binder for the production of extruded ...
Aug 6, 2025 · Whey, the main by-product of the dairy industry, is proposed as a sustainable binder for the production of extruded activated carbon.
[44]
Extruded Activated Carbon Pellets | Bulk Supply for Gas Treatment
Professional extruded activated carbon pellets for gas purification, VOCs removal ... Ball-pan hardness: ≥98%; Bulk density: 0.50-0.60 g/ml. Indoor Air ...
[45]
None
### Summary of Extruded Activated Carbon (EAC) from the Document
[46]
Types of Activated Carbon: A Comprehensive Guide to Purification ...
Jun 4, 2024 · Extruded Activated Carbon (EAC) · Excellent flow dynamics: Creates predictable pressure drop in gas-phase applications · Low dust content: ...
[47]
Solvent Recovery Activated Carbon Solutions-Heycarbons
Ball Pan Hardness: Min. 98 %; Moisture Content: as packed Max. 5%; Bulk ... Special process adding Special substance Pellet (Extruded) activated carbon also named ...
[48]
https://heycarbons.com/activated-carbon-for-solvent-recovery/
[49]
[PDF] Bead-shaped Activated Carbon BAC
High flowability makes BAC suitable for fluidized bed type filters. □ High wear resistance contributes to longer lifetime in fluidized bed filter. □ The six ...
[50]
[PDF] ACTIVATED CARBON IN GOLD RECOVERY - Kemix (Pty) Ltd
This article serves to discuss the fundamental aspects of gold recovery utilizing the. Carbon-in-Pulp or Carbon-in-Leach processes.
[51]
Catalytic reduction of NO over copper supported on activated carbon
Jun 1, 2023 · The selective catalytic reduction of NOx with carbon is an alternative technology to the more common reduction processes using NH3. This work's ...
[52]
[PDF] 0.5% Silver Impregnated Activated Carbon
0.5% Silver Impregnated Activated Carbon. Description. Type 1184 is a silver-impregnated coconut shell activated carbon specifically designed for ...Missing: antibacterial | Show results with:antibacterial
[53]
Removal of hydrogen sulfide from a biogas mimic by using ... - NIH
Feb 12, 2019 · Impregnated activated carbon for H2S adsorbents, which used alkaline compounds, such as sodium hydroxide (NaOH), potassium hydroxide (KOH), and ...
[54]
Indoor air treatment of formaldehyde by N-enriched activated carbon ...
Sep 13, 2025 · Indoor air treatment of formaldehyde by N-enriched activated carbon beads with or without CuO/Cu ... A Brief Review of Formaldehyde Removal ...
[55]
Chitosan Polymer Functionalized-Activated Carbon/Montmorillonite ...
May 5, 2023 · A simple approach for synthesizing a highly adsorbent composite was described for the uptake of heavy metal ions from wastewater.Missing: selective | Show results with:selective
[56]
Adsorption kinetics and mechanisms of nano chitosan coated cotton ...
NCCF has a higher moisture absorption capacity than cotton fiber (CF). Since chitosan is hydrophilic, the moisture content of NCCF rises from 8 % to 12 %. With ...
[57]
Adsorption Characteristics of Activated Carbon Fibers in Respirator ...
Aug 12, 2021 · Activated carbon fiber (ACF) has potential as an alternative adsorbent for developing thinner, lightweight, and efficient respirators due to its ...
[58]
NO Reduction by Activated Carbons. 5. Catalytic Effect of Iron
Low temperature reduction of NO by activated carbons impregnated with Fe based catalysts. ... Catalytic NOx reduction by carbon supporting metals. Applied ...
[59]
[PDF] Adsorption Properties of Lignin-derived Activated Carbon Fibers ...
Feb 25, 2016 · Adsorption of nitrogen at 77 K was used to calculate total surface area by the BET method,15 total pore volume, and the pore size distribution ...<|control11|><|separator|>
[60]
Effects of Molecular Properties on Adsorption of Six-Carbon VOCs ...
Feb 18, 2021 · In general, the specific surface area of the activated carbon ranges from 500 to 1500 m2/g, and its porosity is on the scale of nanometers. The ...
[61]
[PDF] Activated carbon with exceptionally high surface area and ... - HAL
Oct 25, 2021 · This not only provided very high specific surface area of 2934.60 m2/g with a total pore volume of 1.33 cm3/g, and highest capacitance (198.15 F ...
[62]
FR2856399A1 - PROCESS FOR THE PREPARATION OF AN ...
Activated carbon generally has a very porous structure and can have a total pore volume ... 0.5 to 1.5 cm3 / g. Activated carbon can be in the form of ...<|control11|><|separator|>
[63]
What is Activated Carbon? | Newterra
Jan 17, 2023 · The solid, or skeletal, density of most activated carbons will range between 2.0-2.1 g/cc, or about 125-130 lbs/cubic foot. However, this would ...
[64]
Activated Carbon Density: Everything You Should Know
The apparent density of activated carbon will be in the range of 300 to 500 kg/m3, however this can also be outside of this spectrum because of for example raw ...
[65]
Activated Carbon Density:3 Types, Measurements, Applications
May 26, 2025 · Bulk Density, Mass per volume including voids, 0.25–0.55 g/cm³ ; Particle Density, Mass per particle volume (excluding interparticle voids), 0.50 ...Missing: apparent | Show results with:apparent
[66]
[PDF] Effect of particle size distribution on activated carbon adsorption
3) The physical properties of the particles (eg., surface). 4). The method of shaking the sieve. 5) The dimension and shape of the particle. 6). The geometry ...
[67]
Experimental Study of the Effect of Different Parameters on the ...
Oct 22, 2020 · The effect of particle size (and also the surface area) on the adsorption capacity of activated carbon was also studied. It was observed that ...
[68]
What is the iodine number of the activated carbon? - Carbotecnia
The most widely accepted variable for measuring operational capacity in activated carbon is the iodine number. Learn more about this here.Missing: metrics | Show results with:metrics
[69]
Characterization and Properties of Activated Carbon Prepared ... - NIH
The typical range is 500–1200 mg/g, which is equivalent to surface area of carbon between 900 and 1100 m2/g [17]. It can be seen from Figure 2 that iodine ...
[70]
Important Properties of Activated Carbon
Apr 12, 2019 · A high molasses number indicates a high adsorption of big molecules (range 95–600). Caramel dp (decolorizing performance) is similar to molasses ...
[71]
Methylene Blue Number as Useful Indicator to Evaluate the ...
Aug 6, 2025 · Methylene blue number (MBN) indicates the mesoporosity of activated carbon materials and is defined as the maximum amount of dye in mg adsorbed ...
[72]
Carbon Tetrachloride Activity
Apr 18, 2015 · ... means of specifying the degree of activation or quality of activated carbon. Commercially available carbons range from 20% to 90% CTC activity.Missing: definition | Show results with:definition
[73]
Activated Carbon Hardness (ASTM D3802-89)
Activated carbon hardness is a measure of its mechanical strength, measured by the ASTM D3802 test, where carbon is rotated in a drum with steel rods.Missing: 85-98% retention
[74]
[PDF] Preparation and Characterization of Activated Carbon from Date Pits ...
However, neither of the GAC sample, obtained from date pits, attain the minimum standard hardness of 95% required for GAC [17]. The data on retention of ...
[75]
[PDF] Activated Carbon Basics
. Physical activation with H2O vapor is the most common acti- vation process prac- ticed industrially, but chemical activation is. FIGURE 1. Activated carbon ...
[76]
Decoding The Science Behind The Ash Content Of Activated Carbon‌
May 15, 2025 · Ash refers to the inorganic residues (metal oxides, inorganic salts, etc.) left after activated carbon is processed at high temperatures, typically accounting ...
[77]
https://www.calgoncarbon.com/app/uploads/Basics-of-Activated-Carbon-Calgon-Carbon-Chemical-Engineering-Magazine.pdf
[78]
Activated Carbon For Chlorine Removal From Water - Heycarbons
Chlorine (Cl₂) reacts with carbon (C) on the surface of activated carbon: Cl2+H2O+C→HCl+HOCl · Hypochlorous acid (HOCl) reacts with activated carbon: HOCl+C→H++ ...Missing: half- 0.5-2 min/
[79]
[PDF] GRANULAR ACTIVATED CARBON (GAC) FACT SHEET
This tells us that if it takes x number of seconds (or minutes) to reduce a particular contaminant by 50%, it will take x number of seconds to reduce the ...Missing: g HOCl
[80]
Surface Modified Activated Carbons: Sustainable Bio-Based ... - NIH
Nov 21, 2021 · In this review, we summarized several modification methods for agricultural-waste-based ACs. In addition, the applications of AC for the adsorption of various ...
[81]
Role of grinding method on granular activated carbon characteristics
Granular activated carbon (GAC) is commonly used in water treatment to adsorb dissolved organic contaminants and metallic ions that cannot be effectively ...
[82]
Use of Steam Activation as a Post-treatment Technique in the ...
Steam activation widens the microporosity as from the early stages of the activation process, the resulting activated carbons exhibiting a lower micropore vol.
[83]
Current Progress on the Surface Chemical Modification of ... - MDPI
The present review article intends to deliver precise knowledge on efforts devoted by researchers to surface modification of activated carbons.
[84]
Tailored Metal-Doped Activated Carbon Adsorbents Exhibiting High ...
Aug 19, 2025 · Based on the above findings, we developed metal-decorated high-surface-area AC adsorbents via in situ deposition and parametrically studied the ...
[85]
Ultrahigh Surface Area Nanoporous Carbons Synthesized via ...
The materials design leads to nanoporous carbons with a BET area of 4800 m2 g ... The masimum surface area of activated carbon is up to 3839 m2 g-1, and high ...
[86]
A Look at Activated Carbon Thermal Regeneration
The material is heated up to around 1000º F, which volatilizes 75 – 90% of the adsorbed materials. At this point, steam is injected into the system to remove ...
[87]
[PDF] Steam Regeneration of Adsorbents: An Experimental and ... - HAL
Aug 25, 2023 · Abstract: Once adsorption process is over adsorbent is to be discarded as waste. Generation of waste adsorbent is a serious environmental ...
[88]
Performance of Regenerated Activated Carbons on Pesticides ...
Aug 19, 2023 · All ACs had more than 99% desorbed MCPA after the first cycle of washing with ethanol. The washing with NaOH solution was less efficient.
[89]
(PDF) Chemical and Thermal Regeneration of an Activated Carbon ...
Apr 9, 2025 · The spent activated carbon samples were regenerated by means of organic solvent treatments and subsequent heat treatments. The organic solvents ...
[90]
Chemical regeneration of granular activated carbon - RSC Publishing
Jun 15, 2020 · Chemical regeneration, using a novel regenerant solution, offers a low-energy and resource efficient process for the removal of poorly adsorbed ...
[91]
Bio-Based Adsorption as Ecofriendly Method for Wastewater ... - NIH
A recent study was devoted to the biological regeneration of activated carbons and indicates that the use of micro-organisms to regenerate activated carbon ...
[92]
Bioregeneration of activated carbons by bacterial degraders after ...
Aug 9, 2025 · Effective bioregeneration depends on a number of factors, such as the type of microbe present, the optimal microbial growth, including nutrients ...Missing: 2020s | Show results with:2020s
[93]
Process Design Manual For Carbon Adsorption - epa nepis
... carbon losses usually vary from 5% to 10% per regeneration cycle. As stated before, the relatively high cost of granular activated carbon (24^ to 30^ per ...
[94]
Electrochemical reactivation of granular activated carbon
Aug 7, 2025 · However, the process characteristics include: (1) loss of carbon mass (5–15% during each cycle) due to carbon burn-off and attrition; (2) ...
[95]
Home Water Treatment Using Activated Carbon - Purdue Extension
AC effectively removes organic compounds such as volatile organic compounds, pesticides and benzene. It can also remove some metals and radon. As with any ...
[96]
[PDF] 1. Empty Bed Contact Time (EBCT) - Urbans Aqua
Sep 20, 2017 · Empty Bed Contact Time (EBCT) is the time water is in contact with activated carbon, calculated by bed volume divided by flow rate.
[97]
[PDF] Respirators and Human Protection - Calgon Carbon
In the simplest terms, impregnated carbon does double duty: first it grabs the contaminants, and then it either holds them or turns them into something harmless ...<|separator|>
[98]
Impregnated Activated Carbon
For water treatment and acid gas and VOC removal in air purification, such as SO2, NOX,etc. K2CO3. For NH3 removal and acid gas removal, such as SO2. H3PO4.
[99]
Removal of mercury vapor from air with sulfur-impregnated adsorbents
Applied and Environmental Soil Science 2009, 2009 , 1-8. ... Sulfur Impregnation on Activated Carbon Fibers through H2S Oxidation for Vapor Phase Mercury Removal.
[100]
[PDF] Off-Gas Treatment Technologies for Soil Vapor Extraction Systems
Estimated Capital Cost Range for Vapor-Phase Activated Carbon Treatment Units ... referred to as “scrubbing” and is widely used in both industrial and site ...
[101]
[PDF] and Polyfluoroalkyl Substances (PFAS) in Drinking Water - EPA
Mar 6, 2024 · In addition to removing PFAS, GAC can remove contaminants including taste and odor compounds, natural organic matter, volatile organic compounds ...
[102]
The Use of Activated Charcoal to Treat Intoxications - PMC
In adults, a single dose of 50 g activated charcoal is generally recommended independent of BW, in exceptional circumstances up to 100 g (Table).
[103]
Beauty of the beast: anticholinergic tropane alkaloids in therapeutics
Sep 16, 2022 · The treatment of TA poisoning including gastric emptying, use of activated charcoal (0.5 to 1 g/kg in children or 25 to 100 g in adults) to ...Missing: 100g | Show results with:100g
[104]
Carbamate Toxicity - StatPearls - NCBI Bookshelf
Some experts recommend administering 1 g/kg of single-dose activated charcoal if the patient presents within 1 hour of a massive life-threatening GI ingestion.
[105]
Activated Charcoal - PubChem - NIH
Used as a antidote to treat poisonings following excessive oral ingestion of certain medications or poisons. DrugBank. An oral suspension of activated charcoal ...Missing: 100g | Show results with:100g
[106]
Common Causes of Poisoning: Etiology, Diagnosis and Treatment
Oct 11, 2013 · Activated charcoal administration is contraindicated after the ingestion of corrosive substances (e.g., inorganic acids), surfactants, or liquid ...
[107]
Preconcentration of heavy metals on activated carbon and their ...
A method of separation and preconcentration of cadmium, cobalt, copper, nickel, lead, and zinc at trace level using activated carbon is proposed.
[108]
Determination of volatile organic hydrocarbons in water samples by ...
The analytes were extracted using a SPDE needle device, coated with a poly(dimethylsiloxane) with 10% embedded activated carbon phase (50-microm film thickness ...
[109]
desorption from activated charcoal using accelerated solvent ...
A desorption study of 57 volatile organic compounds (VOCs) has been conducted by use of accelerated solvent extraction (ASE) and gas chromatography-mass ...
[110]
[PDF] ARTISAN DISTILLING - Regional Vegetable Program Admin
Mar 25, 2004 · fermentable and are acceptable for whiskey, vodka, and gin production; ... An activated-carbon treatment can still lead to a partial ...
[111]
[PDF] BEVERAGE INDUSTRY - Calgon Carbon
Activated carbon is an effective technology that improves the quality of beverages by removing undesired compounds, such as color, odors and organic.
[112]
Modeling and optimization of Carbon in leach (CIL) circuit for gold ...
Carbon in leach (CIL) is a gold processing step involving continuous leaching of gold from ore to liquid and counter-current adsorption of gold from liquid to ...
[113]
Langmuir, Freundlich and Temkin adsorption isotherm for gold ...
This study investigates the behavior of gold adsorption from cyanide leaching solution onto activated coconut shell carbon.
[114]
Why is Activated Carbon Important for Liquid Chemicals? - Chemviron
Activated carbon is proven to be highly successful for the purification, decolourising, or deodorizing of many liquid chemical products.
[115]
Purification of chemicals by NORIT activated carbon
NORIT activated carbons find widespread use in the chemical industry, to purify numerous products ranging from bulk to fine chemicals.
[116]
Evaluating methane adsorbed film densities on activated carbon in ...
In small micropores (< 8 Å), at 30 bar, the film densities have typically been found to be between 0.20-0.27 kg/L while in the larger micropores they have ...
[117]
The Effects of Methane Storage Capacity Using Upgraded Activated ...
Sep 9, 2018 · The results showed that upgraded ACs with surface areas of 3052 m 2 /g had the highest CH 4 storage capacity (0.32 g-CH 4 /g-ACs at 3.5 MPa).
[118]
Advanced Applications of Activated Carbon: Catalysis and ... - Books
May 10, 2023 · This work covers the recent use of AC as the catalyst in several reactions, as well as methods investigated to improve the AC properties for catalytic ...Characteristics of AC as a... · Transesterification for... · Catalytic Oxidation of Nitric...
[119]
Use of heterogeneous activated carbon supported copper catalyst ...
5% Cu/AC catalyst improved COD and color removal from real wastewater. The catalyst could be reused twice after regeneration as wet oxidation catalyst.
[120]
Mercury Removal with Activated Carbon
Specially designed to treat a variety of flue gas compositions, FLUEPAC combines high adsorption capacity for many pollutants with exceptional mercury removal ...
[121]
[PDF] Removal of Mercury from Flue Gas using Activated Carbon
Using Activated Carbon, in conjunction with other flue gas treatment methods, can further improve mercury removal efficiency. Applicability. Mercury control ...
[122]
Electrode Materials for Supercapacitors: A Review of Recent ... - MDPI
The specific capacitance values for the activated carbon electrodes in aqueous electrolytes (between 100 to 300 F·g−1) is higher than in organic solution (<150 ...<|separator|>
[123]
Recent Advanced Supercapacitor: A Review of Storage ... - NIH
... carbon-based supercapacitor electrodes exceeds 300 F g−1. ... Capacitance limits of high surface area activated carbons for double layer capacitors.
[124]
High-capacity activated carbon anode material for lithium-ion ...
The activated carbon anode possesses a reversible capacity of 757 mAhg−1 at a current density of 100 mAg−1 and a good cycling performance at high current rates.
[125]
Boosting energy storage density of lithium-ion hybrid capacitors via ...
The device incorporating 2.5 wt% GNF achieved an impressive capacity of 62.35 mAh g−1, along with advanced energy density of 115.58 Wh kg−1. These results ...Missing: advancements | Show results with:advancements
[126]
Carbon hybrid nano-architectures as an efficient electrode material ...
Impressive capacitance values between 230 F/g and 500 F/g were obtained ... activated carbons are widely employed as electrode materials for EDLCs.
[127]
High energy density carbon–cement supercapacitors for ... - PNAS
Sep 29, 2025 · These advances solidify the scientific foundation of ecˆ3 as a class of scalable energy storage materials in the realm of building physics ...
[128]
Use of carbon to reduce the uptake of insecticidal soil residues by ...
Use of carbon to reduce the uptake of insecticidal soil residues by crop plants. Effects of carbon on insecticide adsorption and toxicity in soils.
[129]
[PDF] Activated Carbon, Biochar and Charcoal - USDA ARS
Feb 9, 2018 · Feedstock moisture is not just a question of the energy balance of biochar production, but has also the potential to define biochar properties.
[130]
[PDF] Activated Charcoal - Agricultural Marketing Service
Aug 15, 2002 · Executive Summary. 1. Activated carbon was petitioned for veterinary use, principally to remove toxins. It is considered to be the universal ...
[131]
Aflatoxin Toxicity Reduction in Feed by Enhanced Binding to ... - NIH
Jun 10, 2011 · However, animal feeding studies concluded that activated carbon does not effectively reduce aflatoxin toxicity to fed animals or is not as ...
[132]
Activated Carbon in Sugar Refining - American Chemical Society
This decrease in viscosity after carbon treatment results in increased rate of evaporation, higher filtration rates, and improved workability of the fillmass.Missing: purification | Show results with:purification
[133]
E153 (Vegetable carbon) – what is it? | Colorants - Foodcom S.A.
Vegetable carbon (E153) – what is it? Vegetable charcoal, designated as E153, is a natural food coloring derived from plants. It is a form of activated carbon ...
[134]
Synthesis, Characterization, Adsorption Isotherm, and Kinetic Study ...
Oct 29, 2020 · Adsorption equilibria isotherms for tannin adsorption onto the AC were collected at three different pH of 2, 4, and 6 and were nonlinearly ...
[135]
Effect of Charcoal in Cigarette Filters on Free Radicals in ...
Apr 18, 2019 · Commercial cigarettes containing charcoal filters produced 40% fewer gas-phase radicals than did regular cellulose acetate filter cigarettes.
[136]
The use of charcoal in modified cigarette filters for mainstream ...
Feb 24, 2017 · At the highest charcoal loadings, carbonyls were reduced by nearly 99%. Tar and nicotine decreased modestly (<20%) compared to reductions in ...
[137]
Removing tar and nicotine from mainstream cigarette smoke using ...
Mar 1, 2021 · The objective of this work was to use air-dried sepiolite granules as an additive in cigarette filter tips to increase the removal yield of tar and nicotine ...
[138]
[PDF] Formulation And Evaluation Of Activated Charcoal Peel Off Mask
This activated charcoal peel-off mask uses activated charcoal to adsorb dust and unclog pores, and includes PVA, glycerine, and ascorbic acid.
[139]
Decolorization of Biofuels and Biofuel Blends for Biogenic Carbon ...
Jul 11, 2022 · Reduction of color may be accomplished by the addition of selective adsorbents such as silica gel, (14−16) activated carbon, (14) or various ...
[140]
[PDF] Purification of Biodiesel Using Activated Carbon Produced from ...
In this study, activated carbon from cocoa pod husk activated with was used for purification in pre-treatment process of biodiesel production.