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 Ca2+. NOM was found to be suppressive on the activity of ZVM, and coupled effect of Ca2+ 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).

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► Steel pickling waste liquor was employed to obtain nanoscale zero-valent metal.
► Effects of factors were investigated to lay foundations for in situ remediation.
► The nZVM had a removal capacity of 182 mg/g.
► Mechanism was proposed to understand transport pathways of Cr(VI) in mediums.