Bromide (Br−) is a sink for sulfate radical (SO4*−) and hydroxyl radical (HO*) to form reactive bromine species (RBS) such as Br* and Br2*−. However, effects of Br− in fresh water (~μM) on the radical chemistry of UV/peroxydisulfate (UV/PDS) for the degradation of structurally diverse micropollutants are largely unknown. These gaps were systematically investigated in this work. Combined probing methods with kinetic model, Br− at 1 − 50 μM promoted the conversion from SO4*− to HO* and RBS in UV/PDS. At pH 7, the concentration of HO* showed an increasing and then decreasing pattern with a maximum increase at 5 μM Br−, while those of RBS were 2 – 3 orders of magnitude higher than SO4*− and HO*. At pH 10, alkaline condition promoted the conversion from SO4*− to HO*, and accelerated the transformation from RBS to HO*. Br− at 1 and 5 μM decreased the pseudo-first-order reaction rates of 15 pharmaceuticals and personal care products (PPCPs) by 15.2 – 73.9%, but increased those of naproxen and ibuprofen by 13.7 – 57.3% at pH 7. The co-existence of 10 − 1000 μM Cl− with 5 μM Br− further converted SO4*− to HO* compared to Br− alone. Bicarbonate scavenged SO4*− and HO* but slightly affected RBS, while natural organic matter consumed HO* and RBS more significantly than SO4*−. This study demonstrated that Br− in fresh water significantly altered the radical chemistry of UV/PDS, especially promoted HO* formation.

Effects of bromide at fresh water levels on radical chemistry and PPCP degradation by UV/peroxydisulfate treatment

ACS Spring Meeting 2021

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