Bulletin Spring‧Summer 2001

Save the Brooks, Rivers and the Seas Using Biosorption and Biodegradation to FIGHT Toxic Dyes Synthetic Dyes a Th r eat t o t he Env i ronmen t Synthetic dyes are indispensable to th e textile and dyeing industries. Fashion would not have so much colour and arouse so much interest were it not for the effects o f such dyes. Amo n g all synthetic dyes, azo dyes are the most common, being used up to 90 per cent o f the time, because they are versatile and easy to synthesize. Yet many azo dyes are toxic and may cause genetic mutations. A n d because they are synthetic, the natural en v i r onmen t cannot recognize t hem or degrade their toxicity. T h o u gh man ha s invented sewage treatment plants to deal with d i f f e r e n t k i n d s o f ma n - ma de sewage, technology as it is now is unable to degrade the toxic components of azo dyes. Even a very l ow concen t r a t i on o f these dyes in industrial effluents is enough to do great damage t o the environment. Mo r e worrying is the fact that current legislation only governs the amo u n t o f b i o c hem i c a l oxides i n , and the level of alkalinity and acidity of industrial effluents, but not the dye concentration. I f polluted fluids are discharged directly into the aquatic environment, their toxicity will be absorbed by aquatic creatures and will eventually find its way through the food chain int o human beings. The crucial thing right now is to find a way to degrade azo dyes and this is precisely what Prof. Wong Po-keung of the Department of Biology has been working at since 1989. Cur rent Methods o f Degradation Less Than Ideal Prof. Wong said methods of treating azo dyes f a l l i n t o three b r o ad categories: physical, chemical, and biological. Physical methods include flocculation, memb r ane f i l t r a t i o n, electrolysis, and electroflotation. Ch em i c a l me t h o ds i n v o l v e a d d i ng chemicals into industrial effluents to break up azo dyes into tiny spheres that float or sink, or using i on exchange to enable the dyes to stick to resin. I r r a d i a t i o n and oxidation are also used. Save the Brooks , Rivers, and the Seas 33