Simultaneous removal of phosphate and dissolved organic matter from wastewater by MgO-doped magnetic biochar: Binary adsorption and interaction mechanism

To achieve simultaneous removal of phosphate (P) and dissolved organic matter (DOM) from the wastewater effluent, a novel MgO-doped magnetic biochar (MMBC) was developed in this study. The adsorption capacities of P and the humic acid (HA, a representative DOM) were 28.65 and 176.8 mg/g in single adsorption system, 27.74 and 162.5 mg/g in binary adsorption system, respectively. Moreover, the co-existence of P influenced the preferential adsorption order of HA with different average molecular weights. Mechanistic study exhibited that the adsorption of phosphate was mainly depended on the ligand exchange while the combination of ligand exchange, electrostatic attraction, and π-π interaction was the potential mechanism for HA adsorption. The long-term adsorption suggested that the MMBC-600 could be reliable in P and DOM removal from wastewater tailwater for multiple cycles. This study highlighted the feasibility of MMBC in P and DOM removal, making it a sustainable adsorbent for wastewater purification.