Enhanced Cr (VI) reduction and removal by Fe/Mn oxide biochar composites under acidic simulated wastewater

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

“…After loading Fe–Mn oxides, the relative contents of Fe–O/Mn–O and CO in FMBC increased from 6.04% and 0.72% to 21.68% and 3.02%, respectively, which demonstrated that Fe–Mn oxides effectively increased the number of O-containing groups on FMBC. 13 In Fe 2p profile of BC (Fig. S2c†), The element Fe in BC existed as Fe( iii ) corresponding to binding energies of 711.07 eV and 724.57 eV.…”

“…20 Notably, the intensity of O-H, C]C/C]O, and -COOH groups on FMBC were all enhanced upon loading of Fe-Mn oxides, suggesting that the Fe-Mn oxide loading increased the number of O-containing groups in the adsorbents. 13 Additionally, the vibrational peak at 531 cm −1 corresponded to Fe-O group in BC. 19 Aer Fe-Mn oxide loading, the characteristic peak at 531 cm −1 was shied to 539 cm −1 , which may be caused by Fe/Mn-O characteristic peak formed by Fe-Mn oxide loading.…”

“…These results indicated that the oxygen-containing groups (e.g., -OH, -COOH, C-O, and Mn/Fe-O groups) on the FMBC complex with negatively charged Cr(VI). 13,25,35 Notably, the vibrational peak of C]C groups at 1640 cm −1 was shied to 1610 cm −1 , where the vibrational peaks were attributed to the C]C group on the carbon ring, which could be able to provide p-electrons as the adsorption site for contaminants and remove contaminants from solution by cation-p interactions. 32 However, since Cr(VI) existed mainly as anion in solution, this could be the result of cationic-p interaction between Cr(III) generated by reduction and C]C structure on FMBC during the adsorption process.…”

“…12 However, in practical applications, the iron and manganese oxides exhibit insufficient mechanical strength, poor flocculation and easy agglomeration. 13 Biochar as a carrier could effectively improve the agglomeration of Fe–Mn oxides. After the introduction of Fe–Mn oxides, the amount of active site of biochar increased, and its removal performance for contaminants was greatly improved.…”

“…14 Additionally, the multi-metal materials have synergistic adsorption and reduction effects, which can improve the effect of Cr( vi ) treatment. 13 Applying composites to treat Cr( vi )-containing wastewater is expected to achieve the dual purpose of waste biomass resource utilization and Cr( vi ) pollutant control.…”