Integrated Green Complexing Agent and Biochar Modified Nano Zero-Valent Iron for Hexavalent Chromium Removal : A Characterization and Performance Study

In the present study, nano zero-valent iron (nZVI) was loaded on biochar (BC) prepared from recycled waste peanut shells. The loaded biochar in the nZVI@BC composite assumed to weakened the agglomeration of nZVI and environment-friendly complexing agents, sodium citrate (Cit) and sodium carboxymethyl cellulose (CMC) were used respectively to establish the Cit-nZVI@BC and CMC-nZVI@BC for effective removal of Cr(VI) from aqueous environments. Characterization results suggested that Cit and CMC were not only inhibited the oxidation of nZVI, but also effectively improved its reactivity. The experiment results showed that the Cr(VI) removal by nZVI was less than 20%, while CMC-nZVI@BC enhanced the removal efficiency of Cr(VI) to 80.73%, since CMC coated on the nZVI surface for anti-passivation and improved the surface activity of nanoparticles. In addition, Cr(VI) removal efficiency reached to about 100% with the presence Cit-nZVI@BC and the citrate dissociated the passivation layer on the surface of zero-valent iron particles to ensure the reactivity of zero-valent iron. Kinetic studies revealed that the removal of Cr(VI) by Cit-nZVI@BC or CMC-nZVI@BC followed the second-order reaction kinetic model, and the reaction rate of Cit-nZVI@BC and CMC-nZVI@BC were both higher than that of nZVI. Findings revealed that the prepared composites are promising for Cr(VI) remediation from contaminated environments