Investigation of carbon adsorbents (biochar, graphene, activated carbon) in the removal of heavy metals from industrial wastewater: mechanisms, challenges and future prospects

Heavy metal pollution in industrial wastewater is one of the most significant and destructive environmental challenges in recent years. Due to their non-biodegradability, high toxicity, and detrimental effects on human health and other living organisms, the removal of these metals from industrial effluents has become a critical necessity. Common treatment methods for heavy metal removal from industrial wastewater include flotation, coagulation/flocculation, adsorption, ion exchange, chemical precipitation, photocatalysis, electrochemical coagulation, nanotechnology-based filtration, genetic engineering, and microbial fuel cells. Among these, adsorption stands out as an economically and environmentally effective method and has attracted considerable attention. This review focuses on three categories of carbon-based adsorbents: biochar, graphene, and its derivatives, and activated carbon. The study emphasizes their synthesis methods, physicochemical properties, adsorption mechanisms, influencing factors, challenges, opportunities, and less-explored aspects. After evaluating various studies, nine different adsorbents from these three carbon materials were identified as having superior performance compared to other adsorbents of the same type. Results indicate that graphene and its derivatives, despite their relatively low adsorption capacity, exhibit high adsorption efficiency, likely due to active functional groups, layered structure, and strong chemical interactions. For biochar, the best adsorption performance was observed for cadmium. Activated carbon, despite its high specific surface area, showed lower efficiency in some cases. Therefore, the selection of an appropriate adsorbent should consider the target metal and operational conditions. The ultimate goal of this article is to provide a comprehensive summary of the advancements in carbon-based adsorbents for heavy metal pollutant removal to date, highlight their potential, and suggest future directions for enhancing their performance, thereby contributing to a better understanding of industrial wastewater treatment.

کلیدواژه ها:

Biochar ، Graphene ، Activated Carbon ، Carbon Nanomaterial