title: Reducing bromate formation with H(+)-form high silica zeolites during ozonation of bromide-containing water: Effectiveness and mechanisms.
abstract: This paper investigated the effect of H(+)-form high silica ZSM-5 (HZSM-5) zeolites on bromate formation. HZSM-5 zeolites with different Si/Al molar ratios (i.e., 25-300) were tested taking ozonation alone as control. The zeolites were more effective in reducing bromate formation for the filtered surface water than CeO₂, a former reported oxide that can reduce bromate formation at slightly acidic pH. The reduction efficiencies were not closely related to their Si/Al ratios. The HZSM-5 (Si/Al=300) selected for detailed studies effectively reduced bromate formation by 58% for the filtered water, and also enhanced the removal of dissolved organic carbon (DOC) during ozonation. The efficiency of the HZSM-5 in reducing bromate formation increased with ozone dose (0.38-1.16 mg O₃ mg⁻¹ DOC) and pH (6.6-9.3). The HZSM-5 adsorbed OBr⁻ (one of the critical intermediates in bromate formation) quickly with an adsorption capacity of 54 mg g⁻¹, but had no adsorption for ozone, Br⁻, HOBr and BrO₃⁻. It also significantly inhibited the formation of trace H₂O₂ which was generated from ozone decomposition and had been considered promoting bromate formation at low concentrations during ozonation. The reduction of bromate formation in O₃/HZSM-5 is possibly ascribed to the selective OBr⁻ adsorption in combination with the inhibited H₂O₂ formation.
authors.affiliation: Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, China. taozhang@rcees.ac.cn
authors.forename: Tao
authors.initials: T
authors.lastname: Zhang
authors.forename: Pin
authors.initials: P
authors.lastname: Hou
authors.forename: Zhimin
authors.initials: Z
authors.lastname: Qiang
authors.forename: Xiaowei
authors.initials: X
authors.lastname: Lu
authors.forename: Qunhui
authors.initials: Q
authors.lastname: Wang
mesh_terms: D001959:Bromates / Q000032:analysis / Q000138:chemical synthesis / Q000737:chemistry*; D001965:Bromides / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D010126:Ozone / Q000737:chemistry; D014867:Water / Q000737:chemistry; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000138:chemical synthesis / Q000737:chemistry*; D018508:Water Purification / Q000379:methods*; D017641:Zeolites / Q000138:chemical synthesis / Q000737:chemistry*
chemical_list: D001959:Bromates; D001965:Bromides; D014874:Water Pollutants, Chemical; D014867:Water; D017641:Zeolites; D010126:Ozone