Oxidative magnetization of biochar at relatively low pyrolysis temperature for efficient removal of different types of pollutants

A novel oxidative magnetization, involving phosphomolybdic acid and Fe(NO 3 ) 3 co-promoted pyrolysis, was established to manufacture highly adsorptive magnetic biochars for adsorbing aqueous tetracycline, methylene blue, and Cr 6+ . The modification of phosphomolybdic acid greatly boosted the formation of γ-Fe 2 O 3 and oxygen containing groups with enhancement of specific surface area and pore volume at 400 °C. Importantly, γ-Fe 2 O 3 was stably fixed on surface in quasi-nanoscale. The oxidized magnetic biochar displayed 631.53, 158.45, 155.13 mg/g adsorption capabilities for tetracycline, methylene blue, and Cr 6+ with 22.79 emu/g saturation magnetization, respectively. Oxygen containing groups and quasi-nanoscale γ-Fe 2 O 3 served as key adsorption sites for these pollutants. A general oxidative magnetization was established for manufacturing high-performance magnetic biochar through phosphomolybdic acid/Fe(NO 3 ) 3 co-promoted pyrolysis at relatively low temperature.