Metal-Loaded Biochar for the Removal of Arsenic from Water: A Critical Review on Overall Effectiveness, Governing Mechanisms, and Influential Factors

Arsenic (As) contamination in water sources is a serious threat to safe drinking water afflicting many developed and developing nations. Among the different water treatment techniques, arsenic removal using metal-loaded biochar has gained considerable interest as an efficient environmentally sustainable adsorbent. This review critically focuses on an in-depth analysis of different adsorption mechanisms and various physicochemical properties such as pH, surface area and surface charge, porosity, and functional groups of the metal-loaded biochar that are significant for As adsorption, which has not been previously described. It centers on addressing the overall effectiveness, governing mechanisms, and influential factors of metal-loaded biochars for As removal from the aqueous medium. Special consideration on oxidation of arsenite to arsente and its removal was given. The oxidation processes are also effective in reducing arsenic toxicity by oxidation of arsenite to arsenate. A comprehensive insight into the utility of biochar for As removal for future field applications of biochar is delineated.