Assessment of Sawdust potential in the removal of Dye colour from Textile Waste Water

Abstract

The potential of hardwood and softwood sawdust as low cost adsorbents in the removal of a disazo dye (Congo Red) from water was evaluated. Two softwoods, Cypress (Cypress us lusitanica) and Pine (Pinus spp.) and two hardwoods Camphor (Ocotea usambarebsis), and Meru oak (Vitex keniensis) were used in the studies. Those materials were selected on the basis of their relative abundance as a waste in the timber mills industry.

Sawdust was found to have potential in removing Congo red dye from wastewater. The interaction of dye and the sawdust conform to Freundlich adsorption model with softwoods showing a higher potential both in capacity and intensity of removing Congo red dye from wastewater than hardwoods. The coefficients of Freundlich equilibrium model, k and n show that Cypress (Cypressus lusitanica) had the highest potential having k and n values of 0.40 and 1.79, respectively, followed Pine (Pinus spp.) with k and n values of 0.33 and 1.05, while Meru oak and Camphor had the two values being 0.23 and 0.823, and 0.0069 and 0.619, respectively.

The higher dye uptake by softwood sawdust is attributable to more pore spaces and high specific surface area for adsorption than hardwood. The softwoods had lower densities than hardwoods and thus the far more porous. The adsorption correlated positively with the hemicellulose extract of the sawdust, which was high in cypress, pine, Meru oak, and Camphor in that order. Cellulose and lignin content correlated negatively with the adsorption capacity and intensity.