Rapid decolorization of anthraquinone and triphenylmethane dye using chloroperoxidase: Catalytic mechanism, analysis of products and degradation route

• Very efficient enzymatic decolorization for anthraquinone and triphenylmethane dye.
• Products analysis indicated it is a good alternative for biodegradation of these compounds.
• No restriction for dye species due to the active oxidants generated online in catalytic cycle.
• Strong toleration to high saline wastewater was observed ensuring it potential application.

A rapid and efficient enzymatic decolorization of anthraquinone (Alizarin Red) and triphenylmethane dyes (Crystal Violet) by a heme peroxidase, chloroperoxidase (CPO), was presented in this work. The decolorization efficiency of Alizarin Red reached 98.23%, and that of Crystal Violet was 97.68% both within 7 min at mild condition with an enzyme concentration below ppm level. A characteristic mechanism was involved in this enzymatic oxidation, in which some small intermediates with high oxidative activity generated online during enzymatic catalytic cycle. The decolorization was in fact carried out in bulk solution instead of in heme, which can get rid of the restriction for the size of dyes required by the channel access to enzymatic active site. UV–vis and HPLC–MS analysis of products indicated the chromophoric groups were destructed and the dye molecules were broken-down into small pieces, indicating an increase in biodegradability of the dyes. COD and TOC values of dyes solution were all decreased. Meanwhile, the strong toleration of this CPO-catalyzed oxidative decolorization to the typical salt species (NaCl, NaNO3, and Na2SO4) was observed, which showed a potential application of this method in treatment of industrial wastewater.