MTBE oxidation by conventional ozonation and the combination ozone/hydrogen peroxide: efficiency of the processes and bromate formation.
Oxidn. of Me tert-Bu ether (MTBE) by conventional ozonization and the advanced oxidn. process (AOP) O3/H2O2 under drinking water treatment conditions was examd. Major degrdn. products identified were tert-Bu formate (TBF), tert-Bu alc. (TBA), 2-methoxy-2-Me propionaldehyde (MMP), acetone (AC), Me acetate (MA), hydroxy isobutyraldehyde (HiBA), and formaldehyde (FA). Rate consts. for the reaction of O3 and OH- radicals with MTBE were 0.14 and 1.9 * 109/M-s, resp. Rate consts. for the same oxidn. processes were also measured for the degrdn. products TBF, MMP, MA, and HiBA (kO3-TBF = 0.78/M-s; kOH-TBF = 7.0 * 108/M-s; kO3-MMP = 5/M-s; kOH-MMP = 3 * 109/M-s, kO3-MA = 0.09/M-s, kO3-HiBA = 5/M-s; kOH-HiBA = 3 * 109/M-s). Since all compds. reacted slowly with mol. O3, only the degrdn. pathway of MTBE with OH- radicals was detd., including formation of primary degrdn. products. Expts. were performed using natural water to show the efficiency of MTBE elimination, and bromate formation as a disinfection byproduct was measured. With a Br- concn. of 50 mg/L, only 35-50% of MTBE was eliminated by the O3/H2O2 AOP without exceeding the bromate drinking water std. (10 mg/L). Transient concns. of MTBE and primary degrdn. products were modeled using a combination of kinetic parameters (degrdn. product distribution and rate consts.) and O3 and OH- radical concns.; results were in good agreement with exptl. results.
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