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

Ying Han; Kemin Zhang; Qingjie Lu; Zhao Wu; Jun Li

doi:10.1016/j.scitotenv.2021.145550

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

Sci Total Environ. 2021 Jun 10:772:145550. doi: 10.1016/j.scitotenv.2021.145550. Epub 2021 Feb 3.

Authors

Ying Han¹, Kemin Zhang², Qingjie Lu², Zhao Wu², Jun Li³

Affiliations

¹ College of Civil Engineering, Zhejiang University of Technology, Hangzhou 310023, China. Electronic address: yinghan@zjut.edu.cn.
² College of Civil Engineering, Zhejiang University of Technology, Hangzhou 310023, China.
³ College of Environment, Zhejiang University of Technology, Hangzhou 310014, China.

PMID: 33770887
DOI: 10.1016/j.scitotenv.2021.145550

Abstract

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 Ni²⁺ 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.

Keywords: Active hydrogen atom; Fe; N-nitrosodimethylamine; Nickel hydroxide.