A comparative study of adsorbents prepared from industrial wastes for removal of dyes

Waste materials such as blast furnace dust, sludge and slag from steel plants and carbon slurry from fertilizer plants were treated and activated to prepare low-cost adsorbents. The adsorbents were chemically characterized and the surface area determined. The carbonaceous adsorbent prepared from carbon slurry had appreciable surface area (380 m(2)/g); whereas, the other three adsorbents had poor surface area (428 m(2)/g). The adsorption of three basic dyes, that is, chrysoidine G, crystal violet, and meldola blue was studied on all the adsorbents and the results indicated that only carbonaceous adsorbent removed the dyes from solution to an appreciable extent compared to the others. The carbanaceous adsorbent can, therefore, be a useful material for dye removal. All further studies were, therefore, done on the carbonaceous adsorbent. The adsorption isotherms of the dyes were found to conform to the Langmuir equation. The thermodynamic parameters calculated indicated that the dye adsorption was exothermic and physical in nature. The kinetic studies of the adsorption process showed it to be first order and pore diffusion controlled. The adsorption with the carbonaceous adsorbent is about 70-80% of the amount taken up by standard activated charcoal. Thus, the prepared carbonaceous adsorbent is efficient and can be used for the removal of dyes from solution.