This article reports on the preparation of cationized cotton fiber by treating alkali cellulose cotton fibers with epoxy propyltrimethylammonium chloride (EPTMAC) in a nonaqueous medium and its use as support for the immobilization of pollutant dyes. Evidence of attaching quaternary ammonium groups onto cellulose is provided by IR analysis, nitrogen determination, and weight uptake. Four EPTMAC-Cotton fiber samples with different nitrogen content (0.5-1.85) are tested for the adsorption of four acid dyes (Acid Blue 25, Acid Yellow 99, Reactive Yellow 23, and Acid Blue 74). Adsorption is followed spectrometrically, the capacity of adsorption depending on the nitrogen content and on the number of anionic groups in the dye. The Langmuir and Freundlich isotherms constants are evaluated from the experimental data, but better agreement is obtained by using a composite isotherm of the general form Y e ϭ iC e /(1 ϩ jC e m ), where i, j, and m are constants.

Experimental adsorption isotherms for four anionic dyes (Acid Blue 25, Acid Yellow 99, Reactive Yellow 23 and Acid Blue 74) on to cationized cotton have been analyzed using a multilayer adsorption model. For such purpose, the double-layer model showed the best fit with a high correlation coefficient R 2. The analytical expression of the model has been established from an application of the grand canonical ensemble of statistical physics. This method allowed an estimation of all the mathematical parameters in the model. Thus, the receptor site density and the half-saturation concentration have been related to physicochemical variables such as the chemical potential, the adsorption energy, the anchorage number, etc. A physical interpretation of the model parameters has been provided and some results relating to the adsorption process discussed.

Using the same procedure as recently described for cotton fiber, the preparation of cationized wood sawdust was performed by treating alkali sawdust with epoxy propyl trimethyl ammonium chloride (EPTMAC) in a nonaqueous medium (dimethylformamide, DMF). The fixation of ammonium groups onto sawdust was monitored by weight uptake, nitrogen content determination, and infrared spectroscopy. EPT-MAC-sawdust with a 0.5 wt % nitrogen content is then used as adsorbent for acid dyes (Acid Blue 25, Acid Yellow 99, Reactive Yellow 23, and Acid Blue 74). The adsorption capacity, determined by spectrometric measurement of the residual dye in the treated solution, decreases with increasing temperature. The modeling of the adsorption isotherms using Langmuir, Freundlich, and General relations allows the determination of isotherm constants. Globally, EPTMAC-sawdust has a behavior similar to EPTMACcotton, and its use for depollution of waste waters from dyeing industries presents advantages over cotton, such as a larger availability and a lower price.