Prevention of bromate formation by adsorption phase ozonation using high silica zeolites

摘要

The objectives of this work are to propose a novel ozonation process in adsorption phase using high silica zeolites and elucidate its advantages for simultaneous achievement of prevention of bromate formation and sufficiently high ozonation performance. Bromate is formed from bromide during ozonation under conventional conditions and needs to be reduced at least below a regulated concentration because of its considerable carcinogenicity. The ozonation of 2-methylisoborneol (2-MIB), a model Taste and Odor (T&O) chemical, has been studied in our process. It was known that 2-MIB is adsorbed onto high silica zeolite and oxidized with ozone rapidly in micropores. An adsorbent, named US-Y, in which the SiO_2/Al_2O_3 ratio is 70, was the best candidate in this study in terms of adsorption of 2-MIB, decomposition of 2-MIB and prevention of bromate formation. Actually, bromate formation was not detected, while about seventy five percent of 2-MIB was decomposed with extremely low ozone concentration of 0.07 ppm and short retention time of 0.2 min in the presence of US-Y. Its applicability for the treatment of natural water containing natural organic matters (NOMs) was also demonstrated.