1. IntroductionCotton is the most important natural textile fiber. Its structureconsists of cellulose, a polymer constructed of monomeric glucoseunits. Since cellulose is susceptible to hydrolysis when heated inacidic medium, dyeing of cotton must be achieved at pH valuesabove 4 (Broadbent, 2001). The pendant hydroxymethyl groupsin the cellulose chains are partially oxidized to carboxyl groupsduring plant growth, and subsequent processing. These carboxylgroups confer a negative charge to the surface of cotton uponimmersion during the dyeing process. At higher pH values (>8),side chain hydroxyl groups can be ionized, thus increasing the neg-ative surface charge significantly (Rattee, 1995). Therefore, cottongenerally shows poor affinity toward anionic dyes due to chargerepulsion, leading to low uptake of such dyes (Janhom et al., 2006;