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Photocatalytic degradation of pesticides and bio‐molecules in water
Author(s) -
Muszkat Lea,
Feigelson Leonid,
Bir Lena,
Muszkat Karol A
Publication year - 2002
Publication title -
pest management science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.296
H-Index - 125
eISSN - 1526-4998
pISSN - 1526-498X
DOI - 10.1002/ps.578
Subject(s) - chemistry , hydrogen peroxide , photochemistry , singlet oxygen , radical , photocatalysis , peroxide , metribuzin , oxygen , inorganic chemistry , catalysis , organic chemistry , weed control , agronomy , biology
Abstract Two approaches are suggested for the acceleration of the photocatalytic oxidation of organic contaminants of water: acceleration by oxidants and photo‐enhancement by dyes. These processes were examined with several substances: two widely applied herbicides, bromacil (a uracil) and metribuzin (a triazine), and three proteins, studied as models of biocontaminated waters. The effects of oxygen and hydrogen peroxide indicated two different reaction patterns of photo‐oxidation of the herbicides. With metribuzin, oxygen had a pronounced effect on the rate of photo‐oxidation, while the influence of hydrogen peroxide was quite moderate; with bromacil, oxygen had a limited effect on the rate of photo‐oxidation, which however was considerably enhanced by hydrogen peroxide. Acceleration of the photo‐catalytic oxidation of colourless refractory contaminants by photo‐excited dye was observed. Both UV and visible light were required for the enhanced decomposition. The mechanism of the reaction seems to involve a combination of oxidation by hydroxyl radicals, via the hole‐electron semiconductor route, with subsequent oxidation of photo‐intermediates by singlet oxygen formed by dye sensitization. The TiO 2 ‐photocatalyzed oxidation of proteins (albumin, ovalbumin and gamma‐globulin) showed the susceptibility of proteins to photocleavage and of the amino acids to photocatalytic degradation. Tyrosine was the most sensitive, while the degradation of the aliphatic amino acids Gly and Asp was slow. © 2002 Society of Chemical Industry