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

Abstract

a b s t r a c tThe 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

Advances in Treatment of Brominated Hydrocarbons by Heterogeneous Catalytic Ozonation and Bromate Minimization

“…Li et al [19] studies confirmed that bromate formation increased significantly in ozonation alone as pH was increased from 6.3 to 9.5. This can be due to fact that in alkaline medium (i) OH− shifts the acid/base equilibria of HOBr false(pKa= 8.8) towards OBr−, which reacts readily with both O3 and HO• [1], and (ii) OH− decomposes O3 to HO• radicals, which enhances BrO3− formation.…”

“…Li et al [19] reported on catalytic ozonation of bromide containing waters with MCM-48, CeO 2 and combined mesoporous sieve Ce x -MCM-48 (cerium combined with MCM-48) with various Si/Ce molar ratios (Ce 30/66/100/200 -MCM-48). All catalysts were able to considerably impede BrO3− formation in comparison to ozonation alone.…”

“…Li et al [19] proposed a bromate reduction pathway for Ce 66 -MCM-48 with the aid of bromine mass balance studies. Their results revealed that Ce 66 -MCM-48 did not adsorb Br−, HOBr/OBr− and BrO3−, the main bromine-containing species present in the water solution.…”

“…The inhibition activity and bromate yield were as follows: Cu-MCM-41 (28.8 ppb) ≈ Fe-MCM-41 (31.5 ppb) > Fe-Cu-MCM-41 (124.5 ppb) > O 3 (432.5 ppb). They attributed the bromate reduction to ozone decomposition by the catalysts, resulting in a reduced amount of ozone for bromate generation [19]. The higher bromate yield in Fe-Cu-MCM-41/O 3 than in Fe-MCM-41/O 3 and Cu-MCM-41/O 3 systems, is due to more HO• presence in the Fe-Cu-MCM-41/O 3 system.…”

“…After the addition of the catalyst, more ozone is consumed, resulting in a hindrance of the direct oxidation of Br− to HBrO/BrO− by ozone (a key intermediate reaction for bromate generation), and additional oxidation of HBrO/BrO− to BrO3− [19]. The superior efficiency of Fe-Cu-MCM-41, causes an abundance of hydroxyl radicals.…”