Complete removal of N-nitrosamines using in-situ constructed sequential microreactors: Synergies of catalysis-adsorption between N-nitrosamines and their degradation products

Abstract

The removal of N-nitrosamines from water faces the challenges of their difficult adsorption, and incomplete mineralization of degradation products. Herein, we report a new strategy by in-situ constructing microreactor on carbon cloth arrayed CoNi spinel oxide through membrane encapsulation. The NiCo2O4-nanoarrays activate peroxonosulfate, generating reactive oxygen species that rapidly degrade N-nitrosamines. The breaking N-N bond of N-nitrosamines provides an effective binding site for adsorbing degradation products (secondary amines). Meanwhile, electrons conducted from secondary amines adsorbed on Ni sites reconstruct the charge of CoNi sites, bolstering the peroxonosulfate activation to further remove N-nitrosamines and secondary amines. Moreover, the microreactive interface formed between membrane substrate and NiCo2O4-nanoarrays improved the reaction efficiency. It maintains efficient N-nitrosamines removal (96–99%) even in the presence of humic acid. Actual wastewater experiments confirmed its effective control of both N-nitrosamines and N-nitrosodimethylamine formation potential. This study provides a novel approach for eliminating the risk of N-nitrosamines in water.