Removal of arsenite and arsenate from contaminated water using Fe-ZrO-modified biochar

Arsenic (As) pollution of groundwater and drinking water is a global problem. Metal/metal oxide-modified biochars (BCs) have been widely used to remove As from water. Few studies have analyzed the removal effects of zirconium oxide (ZrO)- or iron (Fe)-ZrO-modified BC. In this study, Fe ion (FeCl2) and zirconium oxychloride (ZrOCl2) were used to synthesize modified BC (FeZrO-BC) by a co-precipitation method, which was then used to remove arsenite [As(III)] and arsenate [As(V)] from contaminated natural water. The results showed that Zr and Fe were successfully loaded onto the surface of modified BC and formed abundant positively charged Zr-O and Fe-O groups. The specific surface area (SSA) of FeZrO-BC2 was higher than that of the pristine BC. Kinetic and isothermal adsorption fitting results indicated that the As(III) and As(V) adsorption processes were chemisorption reactions on a monolayer. The maximum adsorption capacities for As(III) and As(V) were 46.7 and 47.8 mg g–1, respectively. The pH (range, 3–11) had little influence. FeZrO-BC2 had improved removal performance for inorganic As [As(III) and As(V)] compared with ZrO- or Fe- modified biochar under various pH conditions in natural water. Therefore, the abundant Zr-O and Fe-O functional groups and large SSA render FeZrO-BC2 a promising adsorbent for removing inorganic As from polluted water.