Equilibrium studies for the adsorption of dyestuffs from aqueous solutions by low-cost materials

A number of low-cost materials (teakwood bark, ricehusk, coal, bentonite clay, hair and cotton waste) have been used as adsorbents for dyestuffs in aqueous solutions. Four red and four blue dyes have been studied; each color group consisted of an acidic, a basic, a disperse and a direct dye. The equilibrium isotherm for each dye-adsorbent system was determined and adsorption capacities from zero to 200 mg dye g^?1 of adsorbent was obtained. In general basic dyes adsorbed to a greater extent than the other dye classes but no single characteristic of the dye or adsorbent seemed responsible for such dye-adsorbent interactions and adsorption capacities.