Treatment of aqueous arsenic - A review of biosorbent preparation methods.

Arsenic (As) is a worldwide human health issue with the major exposure route being the consumption of As-contaminated drinking water. Sorption is considered to be an efficient treatment method, among other technologies, for As removal from various water and wastewater matrices. There are common commercially available sorbents, however, the use of locally or regionally available biomasses have recently been of interest as potentially cost-effective and environmentally friendly alternatives. Despite these benefits, untreated biomasses often show low sorption capacity, can be too fragile, and can lead to coloration of waters when used in treatment processes. Treatment methods of biomasses can include chemical processes using acid or alkaline solutions, developing of biomass composite by deposition of activating agents, and preparation of biochars. This review includes an overview of 53 recent studies that assess a variety of biomass modification methods meant to overcome these issues such as activation with acids or bases and biomass-based composites. Furthermore, future perspectives have been provided to assist in the further optimization of methods for biomass modifications to enhance their As sorption capacities.

Treatment of aqueous arsenic - A review of biochar modification methods.

Arsenic (As) is an ever-present worldwide environmental contamination issue. The process of As sorption for treatment of contaminated waters is regarded as a promising treatment technology approach due to its simplicity and potential for high efficiency. Biochars are carbon-rich porous solids produced by heating of biomasses under low oxygen conditions. Biochars are considered to be environmentally friendly sorbents that can be used to treat various As-containing waters. However, unmodified biochar is generally a poor sorbent for As species due to static repulsion between the As oxyanions and the negatively charged biochar surface. The As sorption capacity of biochars can be substantially improved by treatments using various physical and chemical activation and modification methods. Thus, this review includes 63 research studies using physical and chemical approaches to enhance biochar physicochemical structures and As sorption efficiencies. The effectiveness of each method for altering the characteristics and sorption capacity of biochars is described. This review can help to focus the scope of future As biochar sorption studies and aid researchers in optimization of biochar-based sorbents for As treatment.