Reducing DBPs formation in chlorination of Br-containing Diclofenac via Fe-Cu-MCM-41/O3 peroxidation: Efficiency, characterization DBPs precursors and mechanism

Abstract

Abstract Fe-Cu-MCM-41/O3 was first used as an alternative to O3 to control disinfection by-products generation from chlorinated-disinfection of Br-containing Diclofenac. Accompanying with decrease of TOC, THMs and HAAs had an initial increase, reaching the highest at 30 min, then gradually decreased. Coupling Fe-Cu-MCM-41 with O3 successfully enhanced TOC removal and inhibited bromate, THMs and HAAs formation in post-chlorination when compared with those in ozonation. Four kinds of THMs and six kinds of HAAs were detected. CHCl3 was main Cl-THMs and CHBrCl2 was main Br-THMs. CHCl2COOH was the dominant Cl-HAAs and CHClBrCOOH was main Br-HAAs. A converse Br-THMs order was observed in O3 and Fe-Cu-MCM-41/O3 pre-treatment. Fe-Cu-MCM-41 decreased ozone exposure, reducing the direct reaction of O3 with Br− to form bromate. More DBPs precursors in Fe-Cu-MCM-41/O3 were removed by ·OH. H2O2, which generated during pre-treatment process, reduced HBrO/BrO−to Br−, inhibiting both its reaction with Br-DBPs precursors and bromate formation. The pre-treatment process changed intermediates’ properties and hydrophilic DOM was the dominant component. Hydrophobic acids and transphilic DOM were the main chlorine consuming intermediates and had major contribution to DBPs formation. Fulvic-like intermediates was suggested as precursors of Br-DBPs. Fe-Cu-MCM-41/O3 were suggested as a good alternative to O3 pretreatment.