Kinetics Of 2,4-dibromophenol Degradation By UV/Persulfate System And Products Identification

In recent years,bromophenol as one of typical emerging contaminants have gained increasing attentions.Advanced oxidation processes?AOPs?has been widely investigated and applied for degradation of organic pollutants in drinking water and wastewater treatment plants.Sulfate radical(SO₄^·-)based AOPs has been a hotspot of research in China and abroad.Because of convenient operation,friendly to environment,combined with disinfection process and so on,UV photolysis of persulfate has a bright outlook of engineering application.In this paper,2,4-dibromophenol?2,4-DBP?which was often detected in natural water was selected as the typical model pollutants.This research seeks to investigate the effects of water matrix?natural organic matter?NOM?,pH,carbonate/bicarbonate?CO32-/HCO₃^-?,and chloride ions?Cl-??on pollutants degradations by UV/PDS and UV/PMS process.Degradation products and pathways of UV/PDS and UV/PMS for the model pollutants oxidation were compared.The formation of inorganic bromate in the process of degradation of brominated organic compounds was investigated,along with the influence factors.Finally,UV/PDS combined chloride?chloramine?disinfection process was proposed.The effect on the degradation of 2,4-DBP and oxidation products in the natural water were compared.2,4-DBP could be degraded effectively by using UV/PS process.The second-order rate constants for 2,4-DBP reacting with SO₄^·-and HO· were determined to be 4.32×109 M-1s-1 and 8.73×109 M-1s-1 at netural condition.The removal efficiency increased with increasing the dosage of oxidant,the same result occurred when decreasing the initial compounds concentration.The inhibited effect were exhibited for 2,4-DBP removal in presence of Cl-?CO32-/HCO₃^-and NOM.LC-MS/MS results indicated that hydroxylated polybrominated diphenyl ethers?OH-PBDEs?and hydroxylated polybrominated biphenyls?OH-PBBs?were readily produced in the UV/PDS system,Bromine and 2,4-DBP was porn to react the bromosubstituent in the UV/PMS process,in addition,benzoquinones was detected.The BrO₃^-formation was completely suppressed at higher pH=9 in UV/PS process.Cl-promotes the rate of Bromate production in UV/PDS system.The presence of CO32-/HCO₃^-and NOM significantly scavenge effect on the BrO₃^-formation,but their mechanism were different.The removal efficiency significantly increased by UV/PDS combined with chloride disinfection process in the distribution system water,while the addition of chloramine significantly reduces the degradation efficiency of the target.The presence of Clpromoted the degradation of 2,4-DBP in UV/PDS/chlorine system and UV/PDS/chloramine system,it's worth nothing that the heavy concentration of Clinhibited the degradation of the target in UV/PDS/chloramine system.In addition,chlorine and hydroxyl substituted products were detected in the UV/PDS/chlorine system.When the disinfectant was chloramine,the Nitrogenous Disinfection Byproducts?NDBPs?were generated in oxidation process.