Sulfidized nanoiron-loaded carbon for efficient removal of Cr(VI) from wastewater

With the advancement of industrial development, the threat of chromium (Cr) pollution in the aquatic environment has escalated significantly. So, it is essential to develop economically and environmentally friendly means to remove Cr(VI). In this experiment, a novel material, activated carbon loaded sulfidized nanoscale zerovalent iron (S-nZVI@AC) was prepared by sulfide modification and activated carbon (AC) loading modification. According to the data, the most effective material was found to have a S/Fe molar ratio of 0.07 and an SnZVI@AC mass ratio of 3:1, with a removal rate (RR%) was as high as 99.9% at 60 min. The RR% of the dosage of 0.8 g/L was 99.9% and demonstrated good economic efficiency. The RR% of S-nZVI@AC for Cr(VI) was higher at pH = 3 or 7, reaching 99.8% and 99.6%, respectively. The presence of coexisting ions significantly impacted the RR%, with SO42- , K+, and high concentration of Na+ promoting removal, while PO43- , CO32- and Ca2+ had an inhibitory effect. Of these, PO4 3- could even reduce the RR% to about 10%, whereas a low concentration of Na+ had minimal impact. S-nZVI@AC also exhibited good resistance to aging, maintaining approximately 80% removal after being soaked in water for 10 days. Furthermore, using kinetic and thermodynamic studies, the pseudo-first-order kinetic model, Freundilch, and Elovich models were found to suit the experimental data better. Cr(VI) was eliminated by S-nZVI@AC via a combination of adsorption, reduction, co-precipitation. In summary, it is concluded that S-nZVI@AC was a new material that showed promise in the treatment of Cr(VI) effluent.