Enhanced Phosphate Removal from Aqueous Solutions By MgO-Impregnated Magnetic Biochar and Biochar-Mg/Al Layer Double Hydroxide Composite.

The formation of harmful algal blooms due to excessive phosphates in surface water bodies has become a major risk worldwide. It is crucial to control and lower the levels of phosphate in aquatic system in order to alleviate the eutrophication. Biochar has been used as a potential low-cost adsorbent for contaminant remediation. However, biochar’s predominantly negatively charged surface limits its ability in the adsorption of anionic pollutants. Recently, metal oxides have been incorporated into biochar matrix in order to modify its surface properties. In this study, MgO nanoparticle-impregnated biochar with magnetic nature as well as biochar-Mg/Al layered double hydroxide (LDHs) were synthesized and evaluated for removing phosphates from aqueous solutions. It was found that the magnetic biochar with 20% Mg content exhibited the highest phosphate removal capacity at around 121.25 mg P/g. Mg/Al-LDHs biochars with Mg/Al ratio of 2, 3 and 4 showed significantly higher phosphate removal rate than raw biochar. The maximum adsorption capacity of Mg/Al-LDHs biochar composites was observed with Mg/Al ratio of 4:1 at 81.83 mg P/g. In addition, phosphate-loaded 20% Mg magnetic biochar enhanced plant growth and could be used as a fertilizer. Overall, engineered biochar composites impregnated with metal oxides could be used as cost-effective adsorbents as well as potential alternative fertilizer after use in water remediation.