Zerovalent Iron/Cu Combined Degradation of Halogenated Disinfection Byproducts and Quantitative Structure-Activity Relationship Modeling

This studyreports effective degradation of halogenated(aromatic) DBPs by ZVI/Cu, and a novel mechanism-based quantitativestructure-activity relationship model to predict degradationrate constants was established. Previous studies have reported that zerovalent iron (ZVI)can reduceseveral aliphatic groups of disinfection byproducts (DBPs) (e.g.,haloacetic acids and haloacetamides) effectively, and the removalefficiency can be significantly improved by metallic copper. Informationregarding ZVI/Cu combined degradation of different types of halogenatedDBPs can help understand the fate of overall DBPs in drinking waterdistribution and storage systems consisting of unlined cast iron/copperpipes and related potential control strategies. In this study, wefound that, besides aliphatic DBPs, many groups of new emerging aromaticDBPs formed in chlorinated and chloraminated drinking water can beeffectively degraded by ZVI/Cu; meanwhile, total organic halogen andtotal ion intensity were reduced significantly after treatment. Moreover,a robust quantitative structure-activity relationship modelwas developed and validated based on the ZVI/Cu combined degradationrate constants of 14 typical aromatic DBPs; it can predict the degradationrate constants of other aromatic DBPs for screening and comparativepurposes, and the optimized descriptors indicate that DBPs possessinga lower value of the lowest unoccupied molecular orbital energy anda higher value of dipole moment tend to present higher degradationrate constants. In addition, toxicity data of 47 DBPs (belonging to18 groups) were predicted by two previously established toxicity models,demonstrating that, although most DBPs exhibit higher toxicity thantheir dehalogenated products, some DBPs show lower toxicity than theirlowly halogenated analogs.