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.