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Study on removal of bromate by activated carbon

Study on removal of bromate by activated carbon. By Weifang Chen. Benefits of ozonation a. Prevents the production of halogenated DBP b. Improve flocculation c. Help remove natural and synthetic organic compounds such as taste and odor compounds, pesticides.

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Study on removal of bromate by activated carbon

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  1. Study on removal of bromate by activated carbon By Weifang Chen

  2. Benefits ofozonation a. Prevents the production of halogenated DBP • b. Improve flocculation c. Help remove natural and synthetic organic compounds such as • taste and odor compounds, pesticides. • Disadvantages of ozonation a. Larger amount of aldehydes and other oxidized organic by- • products than chlorination b.Inorganic by-products. potential of formation of • bromate (BrO3-) during ozonation of raw waters containing • bromide ion (Br-)

  3. Mechanism of bromate ion formation O3 BrO3- O3 Br- HOBr/OBr- ·OH Disproportionation Br2- O3 BrO· BrO2- BrO3- ·OH CO3-· BrO2·

  4. Regulations on bromate ion • Bromate is a possible carcinogen, cause kidney, and possibly other tumors • WHO: Maximum 25g/L • USA and EU: less than10g/L.

  5. Treatment of bromate ion • Minimization strategies a. pH depression/acid addition influence the speciation of HOBr/OBr- high cost for high-alkalinity water b. Ammonia addition react with HOBr/OBr- to form bromamine c. Radical scavenger addition ethanol, formate, acetate, oxalate, and glucose do not react with molecular ozone but with OH radicals.

  6. Removal strategies a. Ferrous iron b. Ultraviolet irradiation c. High-energy electron beam irradiation d. Heterogeneous redox catalysis e. Ion exchange f. Activated carbon

  7. Strategies for removal of bromate ion

  8. AC removal mechanismadsorption and reduction

  9. Factors influence the removal of bromate by activated carbon • Carbon surface chemistry carbon with higher PZC has the higher capacity

  10. Solution pH (1) reactivity of bromate ion is higher at low pH (2) surface charge positive at low pH

  11. NOM and other inorganic anions (1) block the access to the pores (2) competition for active sites on carbon surfaces

  12. Conclusions 1.Bromate ion occurs through both a molecular ozone and a free radical pathway. 2.pH depression, addition of ammonia or OH radical scavenger are possible ways to limit the formation of bromate ion during ozonation. 3.Fe2+ reduction, activated carbon adsorption, ion exchange, UV irradiation and electron beam have been used in various scales to remove the bromate.

  13. Conclusions 4.Mechanism of removal of bromate ion by activated carbon is first adsorption of bromate ion onto the activated carbon and then reduced to Br-. 5. Carbon surface chemistry, solution, and NOM and anions in water can affect the performance of activated carbon.

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