Shinji Wada

Removal of chlorophenols from wastewater by immobilized horseradish peroxidase

Immobilization of horseradish peroxidase on magnetite and removal of chlorophenols using immobilized enzyme were investigated. Immobilization by physical adsorption on magnetite was much more effective than that by the crosslinking method, and the enzyme was found to be immobilized at 100% of retained activity. In addition, it was discovered that horseradish peroxidase was selectively adsorbed on magnetite, and the immobilization resulted in a 20-fold purification rate for crude enzyme. When immobilized peroxidase was used to treat a solution containing various chlorophenols, p-chlorophenol, 2,4-dichlorophenol, 2,4,5-trichlorophenol, 2,4,6-trichlorophenol, 2,3,4,6-tetrachlorophenol, and pentachlorophenol, each chlorophenol was almost 100% removed, and also the removal of total organic carbon (TOC) and adsorbable organic halogen (AOX) reached more than 90%, respectively. However, in the case of soluble peroxidase, complete removal of each chlorophenol could not be attained, and in particular, the removal of 2,4,5-trichlorophenol was the lowest, with a removal rate of only 36%. (c) 1996 John Wiley & Sons, Inc.

Flavin-sensitized photooxidation of substituted phenols in natural water

Abstract Photooxidation of substituted phenols in the presence of flavins as sensitizers was investigated under aerobic conditions to determine the fate of synthetic chemicals in the environment. Riboflavin was easily decomposed: lumichrome formed after several minutes of illumination with simulated sunlight. In contrast, lumichrome was extremely stable toward sunlight, and was found to be a major flavin component in natural water. From the result of the lumichrome-sensitized photodecomposition of substituted phenols, the order of photolysis rate is p- methoxyphenol > p- chlorophenol > phenol > p- nitrophenol . A decrease in total organic carbon (TOC) from the reaction solutions of all phenols except for p- nitrophenol was observed, and the carbon released was found to mainly originate from phenols. The compound p- chlorophenol has been shown to degrade readily by lumichrome-sensitized photooxidation, but the transformation occurs only by dechlorination. Polychlorophenols were completely dechlorinated in ∼ 1 hr after lumichrome-sensitized photolysis, and the rate increased with chlorine content on the aromatic ring.