Abstract

Adsorption techniques are widely used to remove certain groups of pollutants such as dyes which are not amenable to biodegradation and environmentally very problematic. Although commercial activated carbon is a preferred sorbent for color removal, its widespread use is restricted due to high cost. As such, alternative non-conventional sorbents should be investigated. It is well-known that natural materials, waste materials from industry and agriculture, and bio sorbents can be obtained without a cost, therefore could be employed as inexpensive sorbents. Therefore the present investigation reports the adsorptive capacity of an industrial residue for the removal of azo dyes. Batch experiments were carried out for the sorption of the dye onto the adsorbent. The influence of contact time, adsorbent dose, pH and initial dye concentration on the adsorption capacity of the material was studied. Kinetics and adsorption isotherms were also studied to evaluate the rate of dye removal and the capacity of the adsorbent. The equilibrium data best fits freundlich isotherm equation. Adsorption capacity (K_f) and intensity of adsorption (n) as determined by fitting the equilibrium data to freundlich isotherm equation are calculated to be 0.26 and 0.82, respectively. The adsorption process was found to undergo via a pseudo-second-order adsorption kinetics with a rate constant of 3.81×10^-3(g /mg / min). The removal of dye was not affected for the initial dye concentration range of 15 to 256 mg/L. An adsorption process; requiring an equilibrium time of 30 h with optimum adsorbent dose of 19 g/L for 77.4% dye removal efficiency was observed at near neutral pH. However, as the pH of water is adjusted from 7 to 9, the dye removal efficiency was greater than 90%. The overall result shows that the industrial by product investigated in this study exhibited a high potential for the removal of dye from aqueous solution.

Key words: Dye, adsorbent, adsorption isotherms, batch adsorption, removal.