Coloured wastewaters are a consequence of batch processes in both dye-manufacturing and dye-consuming industries. Dyes are widely used in a number of industries, such as textile and leather dyeing, food, cosmetics, paper printing, gasoline, with the textile industry as the largest consumer. Dyeing as a fundamental operation during textile fibre processing causes the production of more or less coloured wastewaters, depending on the degree of fixation of dyes on substrates, which varies with the nature of substances, desired intensity of coloration, and application method. Dye bearing effluents are considered to be a very complex and inconsistent mixture of many pollutants ranging from dyes, dressing substances, alkalis, oils, detergents, salts of organic and inorganic acids to heavy metals.Thus after dyeing wastewaters are characterized not only by intensive and difficult for removal colour but also by high pH, suspended and dissolved solids, chemical and biochemical oxygen demands. Ion exchange is a very versatile and effective tool for treatment of aqueous hazardous wastes including dyes. The role of ion exchange in dye effluents treatment is to reduce the magnitude of hazardous load by converting them into a form in which they can be reused, leaving behind less toxic substances in their places or to facilitate ultimate disposal by reducing the hydraulic flow of the stream bearing toxic substances. Another significant feature of the ion exchange process is that it has the ability to separate as well as to concentrate pollutants. Taking into account high capacity and selectivity of ion exchange resins for different dyes, they seem to be proper materials for dyes sorption from textile effluents. The aim of the paper is to study the removal of the acid, reactive and direct textile dyes such as C.I. Acid Orange 7, C.I. Reactive Black 5 and C.I. Direct Blue 71 on the commercially available anion exchangers (Lewatit MonoPlus MP 62, Lewatit MonoPlus MP 64, Lewatit MonoPlus MP 500, Lewatit MonoPlus M 500, Amberlite IRA 67, Amberlite IRA 478RF, Amberlite IRA 458 and Amberlite IRA 958) differing not only in basicity of the functional groups but also in composition and structure of the matrix. Comparison of the sorption parameters obtained by the batch method taking into account influence of phase contact time, dyes initial concentration and solution pH were discussed in detail. Desorption conditions depending on the dyes sorption mechanism were also presented. Influence of the auxiliaries typically present in textile effluents such as inorganic electrolytes and different surfactants on the amounts of dyes retained by the anion exchangers was presented. The adsorption behaviour of the polyacrylic Amberlite IRA 958 demonstrates that it can be a promising adsorbent for the textile wastewater treatment. The results obtained with raw textile wastewaters purification confirmed this statement.
Part of the book: Ion Exchange