Efficient phosphate removal from wastewater using Mg/Fe-functionalized tea stalk biochar through green synthesis and bio-assembly method

In this study, an innovative biogenic assembly process was employed to synthesize magnesium modified magnetic biochar using tea waste as the precursor (MgO@MTB), which was utilized for the treatment of wastewater contaminated with phosphate. The characterization results confirmed the successful doping of Mg, C, and Fe onto the composite of MgO@MTB, thereby enhancing its magnetic property and facilitating efficient recyclability. The kinetic experiment confirmed that MgO@MTB achieved equilibrium for phosphate adsorption within 120 min, and the material exhibited its strongest adsorption capacity at the pH of 6.00. In addition, the Langmuir model revealed that MgO@MTB exhibited a maximum phosphate adsorption capacity of 83.34 mg/kg. Furthermore, as the temperature increases, the phosphate adsorption capacity of MgO@MTB also enhanced, suggesting that the reaction was endothermic in nature. Meanwhile, MgO@MTB with pH dependence demonstrated remarkable resistance to various interfering anions, and the removal efficiency remained at 67.08 % after three regeneration cycles. Significantly, the effective removal of phosphate by MgO@MTB could be attributed to the synergistic combination of chemical adsorption (including ligand exchange, precipitation, and inner-sphere complexation) and physical adsorption (such as pore filling and electrostatic attraction). Therefore, MgO@MTB possesses great potential as a promising material for efficient phosphate removal in aquatic environments.