The role of Cu(II) in the reduction of N-nitrosodimethylamine (NDMA) with zero-valent metals was investigated by determining the effects of Cu(II) on the removal, kinetics, products, and mechanism. NDMA removal was enhanced, and all reactions followed a pseudo-first-order kinetic model except for the Fe and Fe/0.1 mM Cu(II) systems. The iron mass-normalized pseudo-first-order rate constants (kMFe) increased with the Cu(II) concentration. The zinc mass-normalized pseudo-first-order rate constants (kMZn) were identical to those with the Cu(II) concentrations from 0.1 mM to 1.0 mM and were higher with 2.0 mM Cu(II). The types of products detected were unchanged. Some unknown products were also found. NDMA was reduced to 1,1-dimethylhydrazine (unsymmetrical dimethylhydrazine, UDMH). Then, UDMH was reduced into dimethylamine (DMA) by the Fe/Cu(II) and Zn/Cu(II) systems. Catalytic hydrogenation was proposed as the reduction mechanism. Several copper species, such as Cu(OH)2 in the Fe/Cu(II) system and Cu2O and Cu(OH)2 in the Zn/Cu(II) system enhanced NDMA reduction. Differences between the Fe/Cu(II) and Zn/Cu(II) systems were caused by the reduction potentials and surface conditions of the different metals and the copper species in the various systems.
Keywords: Cu(II); Iron; N-Nitrosodimethylamine; Reduction; Zinc.
Copyright © 2016 Elsevier Ltd. All rights reserved.