US EPA

193727 

Journal Article 

Mechanisms of photocatalytical degradation of monomethylarsonic and dimethylarsinic acids using nanocrystalline titanium dioxide 

Xu, Z; Jing, C; Li, F; Meng, X 

2008 

1 

Environmental Science & Technology
ISSN: 0013-936X
EISSN: 1520-5851 

42 

7 

2349-2354 

English 

18504964 

10.1021/es0719677 

WOS:000254492800024 

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=18504964
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Photodegradation mechanisms of monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA) with nanocrystalline titanium dioxide under UV irradiation were investigated. In the presence of UV irradiation and 0.02 g/L TiO2, 93% MMA (initial concentration is 10 mg-As/L) was transformed into inorganic arsenate, [As(V)], after 72 h of a batch reaction. The mineralization of DMA to As(V) occurred in two steps with MMA as an intermediate product. The photodegradation rate of MMA and DMA could be described using first-order kinetics, where the apparent rate constant is 0.033/h and 0.013/h for MMA and DMA, respectively. Radical scavengers, including superoxide dimutase (SOD), sodium bicarbonate, tert-butanol, and sodium azide, were used to study the photodegradation mechanisms of MMA and DMA. The results showed that hydroxyl radicals (HO*) was the primary reactive oxygen species for the photodegradation of MMA and DMA. The methyl groups in MMA and DMAweretransformed into organic carbon, including formic acid and possibly methanol, also through photochemical reactions. The results showed that nanocrystalline TiO2 can be used for the photocatalytical degradation of MMA and DMA and subsequent removal of the converted As(V), since the high adsorption capacity of the material for inorganic arsenic species has been demonstrated in previous studies.