Catalytic ozonation of 2, 2′-methylenebis (4-methyl-6-tert-butylphenol) over nano-Fe3O4@cow dung ash composites: Optimization, toxicity, and degradation mechanisms

Composite magnetic oxide at cow dung ash, nano-Fe 3 O 4 @cow dung ash (nano-Fe 3 O 4 @CDA), was used as catalytic material for the degradation of 2, 2′-methylenebis (4-methyl-6-tert-butylphenol) (AO 2246) in real biologically pretreated landfill leachate . The Fe 3 O 4 @CDA composite exhibited catalytic ozonation activity and allowed material separation and magnetic recovery. The effects of several operating parameters including O 3 concentration, catalyst dosage, temperature and scavengers were evaluated in parallel. Over 70% of AO 2246 were removed by the nano-Fe 3 O 4 @CDA/O 3 system under optimum conditions within 120min reaction time. The EPR, GC–MS and free-radical quenching experiments expatiated the mechanism of this degradation process. It was confirmed that the AO 2246 was degraded efficiently in this catalytic micro-ozonation process, Additionally, GC–MS analysis state clearly that the 3,5-bis(1,1-dimethylethyl)phenol, 4-(1,5-dihydroxy-2,6,6-trimethylcyclohex-2-enyl)but-3-en-2-one, ethanone, 1-(1,4-dimethyl-3-cyclohexen-1-yl)-, 5-tert-butyl-6-3, 5-diene-2-one, 2-hydroxyhexanoic acid, 2-propenoic acid 1,1-dimethylethyl ester, butanoic acid, 2-methyl-, methyl ester and propanoic acid, 2, 2-dimethyl- were the dominant oxidation products (OPs) during the degradation of the AO 2246. The EPR results showed that the catalytic ozonation over Fe 3 O 4 @CDA led to produce more hydroxyl radicals , which were in favor of AO 2246 degradation. The toxicity evolution was also performed through a QSAR analysis calculated by the ECOSAR program which further demonstrated the different responses toward the AO 2246 and its OPs.