(331a) Cyclic Adsorption and Persulfate Oxidation on Iron-Activated Activated Biochar for Removal of Microcystin-LR in Water and Wastewater

In this study, FeCl₃-activated biochar (FA-BC) was prepared and applied for the removal of microcystin-LR (MC-LR) in lake water and DI water by adsorption with persulfate (PS) oxidation-driven regeneration. The increase in temperature resulted in a faster increase in the MC-LR adsorption rate on FA-BC due to the improvement in the desorption of MC-LR from FA-BC and the diffusion of MC-LR in water. The lower pH and higher PS concentration led to the higher regeneration efficiency of MC-LR-spent FA-BC by PS oxidation. In addition, the MC-LR oxidation and PS reaction rates were remarkably improved by factors of 3.4 and 3.5 with increasing temperature from 20 to 50 °C. Both diffusion and desorption of MC-LR from FA-BC controlled the MC-LR oxidation rate during the PS oxidation-driven regeneration of MC-LR-spent FA-BC. Sulfate radical was proven to be the main oxidant participating in the PS oxidation process. Under the conditions of 200 mg/L PS, pH 6, and 50 °C, 83 - 99% regeneration efficiencies were achieved during four cycles of adsorption-PS regeneration in DI water and lake water. Moreover, XRD analysis showed that the crystal structures of α-Fe₂O₃, Fe₃O₄, and Fe⁰ in FA-BC were stable during PS oxidation. Therefore, this study indicates effective regeneration of MC-LR-spent FA-BC by PS oxidation, which would allow cost-effective treatment of MC-LR in water.