Soybean Peroxidase-Induced Treatment of Dye-Derived Arylamines in Water

This research investigated the enzyme-catalyzed oxidative polymerization and precipitation/co-precipitation of the anilino compounds, p-cresidine (2-methoxy-5-methylaniline), and 4,4′-oxydianiline (ODA) suspected to be human carcinogens by the U.S. Environmental Protection Agency, as a means of treating industrial wastewater containing these pollutants. p-Cresidine is a synthetic chemical intermediate for azo dyes and pigments in the food and textile industries whereas ODA is used in the production of polyimide and poly(ester)imide resins in North America. A potentially inexpensive enzyme extracted from the soybean seed coat, soybean peroxidase (SBP), which is widely available from the agricultural commodity, was used to treat both these compounds. The optimum operating conditions such as pH, hydrogen peroxide-to-substrate concentration ratio, and the minimum SBP concentration required to achieve at least 95% SBP-catalyzed conversion of these pollutants in synthetic wastewaters were determined. Electrospray ionization mass spectrometry, employed for preliminary product determination after enzymatic conversion of the substrates, revealed the formation of azo dimers in the precipitates. A pro-forma cost analysis is presented showing the feasibility of commercialization of enzymatic treatment as an alternative, or as an adjunct, to conventional treatment methods.