Cerium incorporated MCM-48 (Ce-MCM-48) as a catalyst to inhibit bromate formation during ozonation of bromide-containing water: Efficacy and mechanism

摘要

The composite mesoporous sieve Ce-MCM-48 (cerium incorporated MCM-48) with different Si/Ce molar ratios were synthesized hydrothermally and characterized with X-ray diffraction, X-ray photoelectron spectroscopy, BET surface area, and pH(pzc). Results indicate that Ce-MCM-48, especially with a Si/Ce molar ratio of 66 (i.e., Ce-66-MCM-48), could significantly inhibit bromate (BrO3-) formation during ozonation of Br- -containing water, achieving 91% of inhibition efficiency at pH 7.6 and 25 degrees C. An acidic or alkaline pH decreased the inhibition efficiency of Ce-66-MCM-48 to some extent, but reaction temperature ranging from 15 to 30 degrees C had no significant impact By comparing the bromine mass balance, aqueous O-3 decomposition, and newly formed H2O2 between O-3 and O-3/Ce-66-MCM-48 processes, the inhibition mechanism was proposed: Ce-66-MCM-48 promoted aqueous O-3 decomposition to generate hydroxyl radicals (center dot OH) that could merge into H2O2, so the oxidative transformation of Br- and HOBr/OBr- by O-3 and center dot OH was primarily suppressed. The catalytic ability of Ce-66-MCM-48 was continuously regenerated through the circulating reactions between Ce(III) and Ce(IV) occurring on the catalyst surface. Besides its inhibition on BrO3- formation, Ce-66-MCM-48 could also enhance the degradation of refractory organic micropollutants. Because of these distinct merits, Ce-66-MCM-48 has potential applications to water treatment by ozone. (c) 2015 Elsevier Ltd. All rights reserved.