Cationized sawdust as ion exchanger for anionic residual dyes

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 EPTMAC-cotton, and its use for depollution of waste waters from dyeing industries presents advantages over cotton, such as a larger availability and a lower price. (C) 2001 John Wiley & Sons, Inc.