Removal of Cr(vi) in wastewater by Fe–Mn oxide loaded sludge biochar

Abstract

Sludge biochar loaded with Fe–Mn oxides (FMBC) was prepared and employed to remove Cr(VI) from wastewater. The influences of solution pH, co-existing ion, contact time, adsorption temperature and Cd(VI) concentrations on removing Cr(VI) by FMBC were investigated. The Cr(VI) adsorption on FMBC had strong pH dependence. Additionally, Na⁺, Mg²⁺, Ca²⁺, SiO₃²⁻, NO₃⁻ and Cl⁻ ions exhibited no influence on Cr(VI) removal efficiency for FMBC, whereas there were inhibition effects of Pb²⁺, Cu²⁺, Ni²⁺, CO₃²⁻, SO₄²⁻, and PO₄³⁻ on removing Cr(VI). The Cr(VI) adsorption from solution for FMBC was well described by models of pseudo-second-order and Langmuir, and the largest Cr(VI) removal capacity of FMBC reached 172.3 mg g⁻¹. FMBC had good capacity for treating electroplating wastewater and mineral dissolving wastewater containing Cr(VI). After five regenerations, the 50 and 5 mg L⁻¹ Cr(VI) removing efficiency of FMBC was 82.34% and 97.68%, respectively. The Cr(VI) removal for FMBC involved adsorption-reduction and re-adsorption of Cr(III) generated by reduction. These results indicated that FMBC has good prospects for remediating Cr(VI)-containing wastewater.