A comprehensive review on the synthesis, performance, modifications, and regeneration of activated carbon for the adsorptive removal of various water pollutants

Rapid urbanization has led to the generation of a large quantum of complex wastewater comprising of recalcitrant organic and inorganic pollutants. The inability of the conventional treatment techniques to bring down the recalcitrant pollutant concentrations below desired standards has paved the way for the emergence of tertiary treatment technologies. Among various tertiary treatment techniques, adsorption is widely preferred due to the ease of operation, high removal performances, and diverse on-field applications. Activated carbon (AC) has found immense popularity due to easy synthesis routes, high stability, large specific surface area (SSA), etc. The synthesis and performance of AC derived from different carbonaceous precursors for pollutants removal, the role of activation techniques, pollutant specific modifications, regeneration techniques, and their disposal, are covered in this article. Trend analysis showed that research on AC derived from agricultural waste and sludge has a high potential for at least another 50 and 25 years, respectively. Most of the precursors are chemically activated to prepare the AC, which may be further modified using the metal impregnation technique for removing specific pollutants. Among various ACs, maximum mean pore volume has been shown by sludge-based AC (1.17 cm(3)/g) and the maximum mean SSA value has been exhibited by husk-based AC (1339 m(2)/g). AC is mostly used to treat dyes and metals, followed by pharmaceuticals, pesticides, and other recalcitrant organics. Moreover, by implementing microwave-assisted and biological-based regeneration techniques, the life of the AC can be increased and may serve as an efficient adsorbent for wastewater treatment for a prolonged duration.