Adsorptive/Desorptive Potential of Cationic Basic Yellow 28 (BY28) Dye onto Natural Untreated Clay from Aqueous Phase

Textile industries are one of the largest consumers of water and hence producers of liquid effluents. The dyeing and finishing processes generate volumes of wastewaters in the range 45450 m3 per ton of product [1], containing salts, acids, bases, additives and unfixed dyes. A suitable treatment of these complex wastewaters should lead to a strong decline on the organic load, and desirably to a complete elimination of the residual color. There are several types of commercial dyes [2,3], and some of these dyes posses a high resistance to biodegradation and persist a long time in the environment [4]. These compounds and their degradation by products are generally believed to be carcinogenic or toxic and become harmful to humans or to the environment. Adsorption processes have been proposed as a fast alternative to remove contaminants from water. Several natural low cost adsorbents have been tested to remove synthetic dyes [5]. In particular, smectite clays have been broadly studied as adsorbents of cationic dyes. This type of clay has a layered structure where each layer is composed by tetrahedral silicate units fused into an edge-shared octahedral plane of aluminum. The isomorphic substitution of Al3+ for Fe2+ or Mg2+ and Si4+ for Al3+ generates charge deficiencies on the surface and interlayer space.