Innovative iron-manganese modified microalgae biochar for efficient phosphate iron removal from water: Preparation and adsorption mechanisms

This study developed a novel FeMn composite biochar (FMBC) with the pyrolysis raw resource of Chlorella, applying for phosphates removal from the aqueous. Under optimal conditions, the FMBC prepared from microalgae achieved a phosphate removal rate of approximately 91.6 % (adsorption capacity: 23.23 mg/g) within 120 min, demonstrating superior adsorption performance compared to the pristine biochar. Response Surface Methodology (RSM) was applied for FMBC preparation optimization. To improve the metal loading capacity of biochar, Ethylene Diamine Tetraacetic Acid (EDTA) was used as a chelating agent during the preparation process. The optimum preparation conditions for FMBC were Fe/biomass(w/w) ratio of 1.25, Mn/biomass(w/w) ratio of 1.10, pyrolysis time of 120 min, and pyrolysis temperature of 650 degrees C, which presented a large specific surface area (14.681 m(2)/g), pore volume (0.036 cm(3)/g) with the rich oxygen-containing functional groups. Phosphorus removal kinetic and isotherm process were better described by pseudo-second-order model and the Dubinin-Radushkevinch (D-R) isotherm. In addition, the optimal adsorption conditions for FMBC were as follows: biochar dosage of 0.1 g, initial pH of 7.0, adsorption temperature of 25 degrees C, and initial phosphate concentration of 50 mg/L. Physical adsorption, surface complexation, precipitation, electrostatic attractions, and ion exchange were responsible for phosphate adsorption process by FMBC. The main innovation of this study is the use of explosive growth algae to prepare metal-modified biochar for phosphorus removal from water bodies, to realize the goals of resource utilization of waste biomass and eutrophication control in water, which are significant for sustainable development.