Degradation of anthraquinone dyes from effluents: a review focusing on enzymatic dye degradation with industrial potential

Up to 84,000 tons of dyes can be lost in water and 90 million tons of water are attributed annually to dye production and their application, mainly in the textile and leather industry, making dyestuff industry responsible for up to 20% of the industrial water pollution. The majority of dyes industrially used today are aromatic compounds with complex, reinforced structures, with anthraquinone dyes being the 2nd largest produced in terms of volume. Despite the progress on decolourisation and degradation of azo dyes, very little attention has been given to anthraquinone dyes. Anthraquinone dyes pose a serious environmental problem as their reinforced structure makes them difficult to be degraded naturally. Existing methods of decolorisation might be effective but are neither efficient nor practical due to extended time, space and cost requirements. Attention should be given to the emerging routes for dye decolorisation via the enzymatic action of oxidoreductases, which have already a strong presence in various other bioremediation applications. This review will discusses the presence of anthraquinone dyes in the effluents and ways for their remediation from dyehouse effluents, focusing on enzymatic processes.