Activated Carbon and Its Applications in Pollution Treatment

Activated carbon is a porous carbonaceous material featuring well-developed micropore structures and an enormous specific surface area. It performs liquid-phase and gas-phase purification relying on surface adsorption capacity. Liquid-phase adsorption is widely applied for decolorization, refining, separation, capture and recovery across food, chemical and pharmaceutical industries. Gas-phase adsorption is used for deodorization, organic solvent recovery, raw material gas separation and gas purification. At present, activated carbon is extensively adopted for the purification of urban drinking water, industrial wastewater and waste gas.

1. Purification of Drinking Water

Environmental pollution in China has intensified in recent years, with urban drinking water contamination standing out as a prominent concern. Advanced overseas drinking water treatment processes combine ozone oxidation with adsorption purification via activated carbon and activated carbon biofilm technology, representing an optimal pollution-free water supply solution available today.

2. Purification of Chromium-Containing Wastewater

Electroplating wastewater pollution plagues numerous domestic regions, among which the treatment of chromium-laden wastewater poses notable technical challenges. In recent years, surface-modified oxidized activated carbon has been deployed for remediation. Hydroxyl functional groups on activated carbon release free hydroxide ions to conduct ion exchange and complex adsorption with chromate () and dichromate (), thereby removing hexavalent chromium () from wastewater.

3. Purification of Printing and Dyeing Wastewater

Domestic facilities once relied entirely on microbial treatment for printing and dyeing wastewater, while activated carbon adsorption has gained growing application in recent years. The iodine value of activated carbon serves as an indirect indicator of its specific surface area, with its numerical value roughly equivalent to the specific surface area figure. Activated carbon effectively adsorbs low-solubility organic compounds yet struggles to eliminate water-soluble low-molecular-weight organics and high-molecular polymers, where microorganisms excel instead. The carbon-biological process complements activated carbon adsorption and microbial biodegradation to deliver superior treatment outcomes compared with standalone techniques.In nutrient-rich wastewater with sufficient dissolved oxygen, microorganisms breed on activated carbon granules to form an activated carbon biofilm. Either excessively thin or overly thick biofilm severely compromises purification efficiency, constituting a core technical parameter alongside the selection of optimal microbial strains. This technology eliminates toxic and carcinogenic organic substances and adsorbs low-molecular-weight oxides. It achieves optimal BOD removal at a wastewater pH range of 3–4 and bears an organic loading capacity 50 times higher than the conventional activated sludge process for domestic sewage treatment. The process boasts robust resistance to loading fluctuations, extends activated carbon service life and cuts carbon consumption and operational costs substantially. It generates minimal sludge and requires no sedimentation tanks for streamlined management.

4. Purification of Refinery Wastewater

Refinery wastewater first undergoes oil separation before secondary purification with activated carbon to remove COD, TOC, phenols and sulfides. Domestic refineries commonly deploy granular activated carbon paired with aeration for oxidative desulfurization during inflow treatment, markedly improving effluent quality while removing carcinogen benzo[a]pyrene.Saturated activated carbon is regenerated via steam stripping to desorb adhered oily contaminants followed by high-temperature thermal regeneration under these specifications: regeneration temperature 800–850°C, retention time 20–30 minutes, steam-to-carbon feed ratio of 1:1, with an estimated regeneration cost of 0.063 RMB per ton of treated wastewater.

5. Purification of Vehicle Washing Wastewater

Freight terminals in major Chinese cities follow a standardized workflow for cleaning trucks previously hauling livestock, chemical fertilizers and pesticides: flushing, sedimentation, dosing with flocculants, sludge removal via plastic bead filtration, activated carbon adsorption and final effluent discharge. The process mainly targets COD reduction; the deployed granular activated carbon has a service lifespan of 1.5 to 2 years with no on-site regeneration.

6. Gas Purification for Coating Industry

Paint is diluted with organic solvents prior to spraying; unused paint and volatile solvents disperse into ambient air during coating operations, triggering severe air pollution, wasting organic solvents and endangering occupational health. Granular activated carbon adsorption is widely used across domestic coating sectors including tin can and bicycle manufacturing to capture and recover airborne organic solvents such as gasoline, benzene derivatives, esters and alcohols with satisfactory recovery performance.

7. Tail Gas Purification for Chemical Industry

Chemical manufacturing generates low-volume, low-concentration and occasionally highly toxic waste gas streams. Activated carbon-based drying, purification and recovery technology has been domestically commercialized for reclaiming carbon tetrachloride from vinyl chloride production tail gas and converting high-concentration sulfur dioxide from sulfuric acid plant exhaust into finished sulfuric acid.

8. Flue Gas Desulfurization

Burning high-sulfur coal (sulfur content >2 wt%) produces flue gas with sulfur dioxide concentrations up to several thousand ppm, triggering acid mist and acid rain, worsening air pollution, disrupting ecological balance and corroding historic architectures and industrial infrastructure. Activated carbon impregnated with 0.5% iodine delivers efficient removal and recovery for exhaust from power and sulfuric acid plants. At flue gas concentrations ranging from 3,000–4,000 ppm or below 350 ppm, the process recovers 20% concentration sulfuric acid. Untreated iodine-doped activated carbon features a adsorption capacity of 12–15 g per 100 g carbon, rising to 14–16 g per 100 g for nitrated activated carbon.

9. Hydrocarbon Fuel Vapor Treatment

China’s annual crude oil output exceeds 100 million metric tons; around 2.2% of crude oil (over 2 million tons yearly) volatilizes into the atmosphere during transportation, processing and storage, causing environmental contamination and massive energy loss. Activated carbon adsorption achieves outstanding results in recovering fugitive hydrocarbon vapors.Furthermore, activated carbon adsorption-desorption technology recovers hydrocarbon fuel from internal combustion engine exhaust, cutting vehicle fuel consumption by 1/4 to 1/3.

10. Technical Advances in Activated Carbon Regeneration

China’s activated carbon regeneration technology has undergone rapid advancement in recent decades. Prior to the 1970s, industrial carbon regeneration techniques remained rudimentary with low carbon recovery rates: acid-base elution regenerated spent carbon saturated from monosodium glutamate decolorization, while sealed calcination in tunnel kiln pottery crucibles was adopted for glucose refining spent carbon.From the 1970s onward, chemical reagent regeneration, a technically feasible desorption method, was applied for activated carbon saturated with adsorbed metallic elements and inorganic compounds. Thermal oxidative regeneration became the preferred route for organically saturated carbon, achieving over 90% carbon activity recovery.

Activated carbon-based pollution abatement is still in its preliminary domestic development stage, with most projects confined to pilot testing. Restricting factors include insufficient popularization of relevant fundamental theories, limited product varieties of dedicated pollution-control activated carbon and high raw material prices. Accordingly, further research and industrial practice are required to refine activated carbon regeneration technologies.