Generation of dichloroacetonitrile with the co-presence of g-C3N4 and chloride in peroxymonosulfate/Vis system: Impacts and mechanism

Monitoring and regulating the formation of toxic byproducts in advanced oxidation processes (AOPs) is of great significance for their practical application in water treatment. In this work, we found that dichloroacetonitrile (DCAN), a common N-containing byproduct in chloramination disinfection, can be formed with the co-presence of g-C3N4 and chloride in a peroxymonosulfate (PMS) system. The measured value was 12.01 mu M within 12 h under the given conditions. Structure analysis of raw and used g-C3N4 demonstrated that g-C3N4 decomposition indeed occurred, and C = N bonds acted as primary active sites, releasing N resources for subsequent DCAN formation. Additionally, multiple parameters, including the reactant (i.e., g-C3N4, PMS, Cl-, phenol) dose and solution pH, were observed to remarkably affect the yield of DCAN. Phenol was identified as the organic precursor of DCAN and may cooperate with inorganic chloramine to promote DCAN formation via the decarboxylation pathway. This study highlights the generation of DCAN in N-involved catalyst-based AOPs and improves understanding of the DCAN formation mechanism.