Removal of phosphate from aqueous solution using magnesium-alginate/chitosan modified biochar microspheres derived from Thalia dealbata

The objective of this study was to determine the feasibility of using magnesium-alginate/chitosan modified biochar microspheres to enhance removal of phosphate from aqueous solution. The introduction of MgCl 2 substantially increased surface area of biochar (116.2 m 2 g −1 ), and both granulation with alginate/chitosan and modification with magnesium improved phosphate sorption on the biochars. Phosphate sorption on the biochars could be well described by a simple Langmuir model, and the MgCl 2 -alginate modified biochar microspheres exhibited the highest phosphate sorption capacity (up to 46.56 mg g −1 ). The pseudo second order kinetic model better fitted the kinetic data, and both the Yoon-Nelson and Thomas models were superior to other models in describing phosphate dynamic sorption. Precipitation with minerals and ligand exchange were the possible mechanisms of phosphate sorption on the modified biochars. These results imply that MgCl 2 -alginate modified biochar microspheres have potential as a green cost-effective sorbent for remediating P contaminated water environment.