Wood Saw Dust as Adsorbent for the Removal of Direct Red (DR) Dye from Aqueous Solution

Abstract

Current researches in adopting or synthesizing materials for water purification through adsorption are targeted on those ones that are renewable or those that have great potentials of reducing waste in the environment. Attempt was made to utilized wastes from the wood industry (wood sawdust) as adsorbent for the removal of Direct red dye from aqueous solution. The results indicated maximum percentage dye removal approaching 100 %. The adsorption of the dye tends to increase with adsorbate dosage and with increase in the initial dye concentration. The adsorption efficiency also increases with time upto 60 minutes after which, further increase in time did not reflect corresponding increase in time. The mechanism of physical adsorption was established for the adsorption of Direct red dye unto the surface of the wood due to decrease in extent of adsorption with increase in temperature, observed values of standard free energy and heat if been less than the threshold values required for the mechanism of chemical adsorption). Langmuir, Temkin and Dubinin-Raduskevich adsorption models were sufficient to explain the adsorption characteristics of wood sawdust for the removal of Direct dye from aqueous solution. Application of pseudo first order kinetics fails with respect to the adsorption of Direct dye on wood sawdust. However, pseudo second order kinetic was established in addition to the freedom of intra particle diffusion model as a controlling factor.