Ball milling potassium ferrate activated biochar for efficient chromium and tetracycline decontamination: Insights into activation and adsorption mechanisms

Herein, novel Fe-biochar composites (MBCBM500 and MBCBM700) were synthesized through K2FeO4 co-pyrolysis and ball milling, and were used to eliminate Cr(VI)/TC from water. Characterization results revealed that higher temperature promoted formation of zero-valent iron and Fe3C on MBCBM700 through carbothermal reduction between K2FeO4 and biochar. The higher specific surface area and smaller particle size of MBCBM500/700 stemmed from the corrosive functions of K and the ball milling process. And the maximal uptake amount of MBCBM700 for Cr(VI)/TC was 117.49/90.31 mg/g, relatively higher than that of MBCBM500 (93.86/84.15 mg/g). Furthermore, ion exchange, pore filling, precipitation, complexation, reduction and electrostatic attraction were proved to facilitate the adsorption of Cr(VI), while hydrogen bonding force, pore filling, complexation and π-π stacking were the primary pathways to eliminate TC. This study provide a reasonable design of Fe-carbon materials for Cr(VI)/TC contained water remediation, which required neither extra modifiers nor complex preparation process.