Production of activated biochar via a self-blowing strategy-supported sulfidated nanoscale zerovalent iron with enhanced reactivity and stability for Cr(VI) reduction

Abstract

Biochar-supported nanoscale zero-valent iron (nZVI) has been unitized for the reduction of Cr(VI). However, the low specific surface area of biochar and the surface oxidation of nZVI limit its contaminant removal efficiency. In this study, activated biochar (ABC) was prepared through a self-blowing strategy and was used as a supporter for sulfidated nZVI (S-nZVI@ABC). The results revealed that S-nZVI@ABC had a significantly increased specific surface area (414 m2 g−1) as compared to S-nZVI supported on commercial biochar (S-nZVI@BC, 62 m2 g−1), and the S-nZVI particles were evenly dispersed. Compared with S-nZVI@BC, the reactivity S-nZVI on ABC increased by 23%. The removal efficiency of Cr(VI) by S-nZVI@ABC was also much higher than the content removed by nZVI, nZVI@ABC. The removal efficiency was nearly doubled when the S/Fe was increased from 0 to 0.5. Higher dosage, lower pH value and Cr(VI) concentration led to an increased Cr(VI) removal efficiency. The retention rate of Cr(VI) removal efficiency was higher than 90% after 10 days of aging. S-nZVI@ABC also showed good reusability in the recycling experiment. The removal process of Cr(VI) was classified as an endothermic process and fitted with the Langmuir adsorption isotherm. Multiple interaction mechanisms including reduction, precipitation, and adsorption were involved in the removal of Cr(VI) by S-nZVI@ABC.