Phosphate recovery from anaerobic digestion effluent using synthetic magnetite particles

Many researchers studied for phosphate recovery, but practical approach through scale-up still remains a challenge. Therefore, we present a technology for recovery of phosphate in anaerobic digestion effluent by synthesizing magnetite. The zeta potential, Fourier transform infrared spectroscopy (FT-IR), and X-ray Photoelectron Spectroscopy (XPS) analyses were used to derive the phosphate adsorption mechanism of magnetite. Physical adsorption is a weak bond generated by electrostatic attraction on the magnetite surface, and chemical adsorption occurs by ligand exchange in which OH- bonded to the magnetite surface is replaced with H2PO3-. The pseudo-second-order kinetics (R-2 > 0.9999) and Langmuir-Freundlich model (R-2 > 0.9999) were most suitable for phosphate adsorption. Magnetite follows both Langmuir and Freundlich adsorption isotherms, the phosphate adsorption characteristics by adsorption isotherm is consistent with the zeta potential, XPS and FT-IR analysis. In addition, it was confirmed that magnetite is a stable adsorbent when operating phosphate recovery processes for sewage through adsorption, desorption, and reuse.