A critical review on arsenic removal from water using biochar-based sorbents: The significance of modification and redox reactions

Biochar is considered to be the cost-effective, environmentally-friendly and sustainable sorbent that has an extraordinary potential to efficiently remove toxic elements, including arsenic (As) from water. Until now, no review has focused to understand various important and intriguing aspects on biochar use as a sorbent for As removal from water, either pristine or modified. This review discusses various factors governing As removal potential of biochars (e.g., pH, biochar dose and physico-chemical properties of biochar), sequestration mechanisms, fate of sorbed As on biochar and the redox-mediated interactions between biochar and As. The significance of biochar-derived materials for the treatment of As-contaminated drinking water/wastewater and their potential regeneration ability is also critically discussed, which has not been previously elaborated. This comprehensive review article could be greatly valuable for scientists, policymakers, water treatment industries, environmentalists and graduate students, who are involved in biochar-As research. The review covers some new overarching and key scientific opportunities for the remediation of As-contaminated water using biochar-based materials, which is a potential health risk to millions of people worldwide.