Enhanced Cr(VI) removal from simulated electroplating rinse wastewater by amino-functionalized vermiculite-supported nanoscale zero-valent iron.

A novel amino-functionalized vermiculite (AVT)-supported nanoscale zero-valent iron (AVT-nZVI) was successfully synthesized for Cr(VI) removal from simulated electroplating rinse wastewater. Since the agglomeration and oxidation of nZVI could be weakened and the reaction rate between Cr(VI) and nZVI could be enhanced for the novel AVT-nZVI, an efficient Cr(VI) removal could be achieved. The experimental results showed that 100% of Cr(VI) removal was obtained with AVT-nZVI, whereas only 87.5% was achieved by nZVI after reacting for 60 min with 20.0 mg L-1 Cr(VI) (pH = 5.0). After four cycles, the removal efficiency of Cr(VI) by AVT-nZVI still maintained at above 70%, suggesting that AVT-nZVI exhibited a good performance of reusability. The stability of AVT-nZVI particles was better than nZVI, which was confirmed by the steady-state polarization measurements. Furthermore, the removal of Cr(VI) by AVT-nZVI was proved to be in accordance with the pseudo-second-order adsorption kinetics and Langmuir model. Based on the experiments and characterization, the reaction mechanism of Cr(VI) removal by AVT-nZVI was clarified. The protonated amino groups (-NH3+) on the AVT promoted negative Cr(VI) species to be adsorbed on AVT-nZVI surface. Besides, Cr(VI) was reduced by Fe (0) to Cr(III), which was eventually adsorbed on the surface of AVT-nZVI particles as the Cr(III)-Fe(III) co-precipitates.