Removal of chromium in electroplating wastewater by nanoscale zero-valent metal with synergistic effect of reduction and immobilization

Reductive immobilization of chromium in wastewater by nanoscale zero-valent metal (nZVM) prepared from steel pickling waste liquor was investigated. A series of characterization techniques were conducted to characterize the properties of the synthesized nanoparticles . Effects of pH, buffer substances, natural organic matter (NOM) and hardness were evaluated to probe the impact of environmental factors. Removal of Cr(VI) benefited from a decrease in pH value and the presences of buffer substances and Ca 2+ . NOM was found to be suppressive on the activity of ZVM, and coupled effect of Ca 2+ and NOM was additive effect due to their non-interference when operating under acidic condition. The nZVM was proved to be more effective (up to 40.6-fold) than zero-valent iron and nanoscale zero-valent iron for Cr(VI) removal, and its removal capacity in wastewater was 182   ±   2   mg   g −1 . The removal mechanism included mass transfer on solid–liquid interface, reduction of Cr(VI) and simultaneous co-precipitation as Cr–Fe (oxy)hydroxide on the surface of nanoparticles. The results presented herein indicated nZVM was promising for in-situ remediation of Cr(VI).