Ion exchange
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In the ion exchange method, the waste water is passed over ion exchange resin until the available exchange sites are saturated. The process can remove both the dye cations and dye anions from the effluent. This method is not generally used for the decolourisation due to limited applicatbility of the ion exchange resins. A combined process involving adsorption on the synthetic polymers and ion exchange may be used to decolourise the dye waste water. The process has several operating and performance advantages. The polymeric absorbent loaded with the dye waste is regenerated and the solvent is reclaimed for reuse, minimising the operating cost45.
One of the effective anion exchange is the quaternised cellulose to which hydrolysed reactive dye bonds through coulombic association of the dye sulphonate groups with resin quaternary amines. Or through additional interaction46.
