Catalytic reduction of N-nitrosodimethylamine in water by zero-valent iron with cobalt-based catalysts

N -nitrosodimethylamine (NDMA) has been the subject of considerable research in the environment. Zero-valent iron (ZVI) technology is essential for the removal of pollutants from water. Cobalt-based catalysts are commonly employed in redox reactions . In this study, the investigation focused on the removal of NDMA by ZVI in the presence of tricobalt tetraoxide (Co 3 O 4 ) and cobalt hydroxide (Co(OH) 2 ). The results indicated that both Co 3 O 4 and Co(OH) 2 could effectively catalyze the removal of NDMA by ZVI. In terms of catalytic efficiency, the ZVI/Co 3 O 4 system exhibited a removal increase of 86.03 % compared to ZVI, while the ZVI/Co(OH) 2 system demonstrated a removal rise of 74.21 %. The ZVI/Co 3 O 4 system demonstrated optimal performance under neutral conditions, whereas the ZVI/Co(OH) 2 system exhibited superior efficacy in weakly acidic and neutral environments. Significant removal of NDMA was achieved across a range of dissolved oxygen (DO) concentrations. The iron mass normalized pseudo-first-order kinetic constants were significantly higher in the ZVI/Co 3 O 4 system compared to those observed in the ZVI/Co(OH) 2 system at pH 6, pH 7 and with DO concentrations varying between 0 and 12 mg·L −1 . In both systems, degradation products of NDMA included unsymmetrical dimethylhydrazine (UDMH) and dimethylamine (DMA). The main active substance was the active hydrogen atom , and the reaction mechanism was catalytic hydrogenation. Characterization of the solid powders yielded that Co 3 O 4 and Co(OH) 2 acted as catalysts and enabled these two systems to have different surface morphologies , corrosion rates, and abilities to generate active hydrogen atoms. These findings provided novel insights into the efficient removal of NDMA from water utilizing ZVI integrated with cobalt-based catalysts. • Co 3 O 4 and Co(OH) 2 could catalyze the removal of NDMA by ZVI. • The catalytic efficiencies of Co 3 O 4 and Co(OH) 2 were different. • The reduction products were detected as UDMH and DMA. • The primary active substance was the active hydrogen atom . • Catalytic hydrogenation was proposed to be the reaction mechanism.