Performance and mechanism of nickel hydroxide catalyzed reduction of N-nitrosodimethylamine by iron

Since iron (Fe) was first proven to have a strong reduction ability, it has been successfully applied to remove pollutants from water. In this study, nickel hydroxide (Ni(OH) 2 ), a catalyst commonly used in hydrogen evolution reactions, was added to improve the activity of Fe to remove N- nitrosodimethylamine (NDMA). The results showed that with the increasing Ni(OH) 2 dosages, the reactions accelerated. The NDMA removal rates increased when the pH value was 6 or 7. Further, when the dissolved oxygen concentration was in the range of 0–12.0 mg∙L −1 , it had little effect on the Fe/Ni(OH) 2 system, and all the reactions obeyed pseudo-first-order kinetics. 1,1-dimethylhydrazine and dimethylamine were formed during NDMA degradation. The capture of active substances and electron spin resonance method confirmed that the main active species were active hydrogen atoms , which participated in the removal of NDMA. Ni(OH) 2 acting as a catalyst was confirmed using wide-angle X-ray diffraction, X-ray photoelectron spectroscopy and Ni 2+ dissolution. Further, catalytic hydrogenation was proposed as the main removal mechanism as Ni(OH) 2 promotes the corrosion of Fe and dissociation of water, thereby generating more active hydrogen atoms. In addition, Ni(OH) 2 may activate both Fe and NDMA. This technique could be employed as an alternative for NDMA reduction and expand the application field of Ni(OH) 2 .