Removal of chromium from tannery waste water using Non Agricultural wastes

Abstract

The removal of Cr (III) from aqueous solutions by batch adsorption technique using different low cost adsorbents was investigated. The objective of the study was to find out a suitable low cost, available, environmental friendly and highly effective adsorbent and minimization of pollution. In the present study different low cost adsorbents of non agricultural origin such as Plastic, Rubber, Hen hair, Sheep wool, Newspaper, Activated bone carbon, Goat skin trimmings, Brick powder, Concrete and Packaging (Corrugated box) boxes have been studied. Of these, Newspaper and Packaging box (Corrugated box) were found to be the most efficient adsorbents. The influences of pH, adsorbent dose, initial adsorbate concentration, contact time and particle sizes were studied. The physico-chemical properties of Newspaper and Packaging box were studied using different characterization techniques such FTIR, Langmuir adsorption isotherm, Freundlich adsorption isotherm and kinetics of the adsorption process.

The basic data obtained were interpreted kinetically using first order rate kinetics. In the case of Newspaper and Packaging box the kinetics followed first order rate equation. Experimental data for all the adsorbents were fitted to different isotherm models such as Freundlich and Langmuir isotherm. Newspaper and Packaging box were observed to be the most effective among all the selected adsorbents for the removal of Cr (III) from aqueous solution. Therefore, all further studies were carried out using these two adsorbents only. Since all adsorbents were porous in nature, it was assumed that the adsorption process might follow surface or intra-particle diffusion or both. In both the cases, the mass transfer coefficients were evaluated from the experimental data. From the values of mass transfer coefficient it was concluded that the initial faster rate was due to surface diffusion and the latter slower part was due to intra particle diffusion.

The desorption process was also studied on saturated adsorbents using different chemicals such as 0.5M of KOH, NaOH, HCL, HNO 3 , H 2 SO solution. Among the five chemicals KOH is observed to be the strong efficient desorbent. Finally, the adsorbents were applied to the effluents emerging from tanneries and it is found effective for the removal of the Cr (III) from the effluent. Thus, the study concluded that the Newspaper and Packaging box serve as an inexpensive and easy to operate adsorbent to remove chromium from tannery waste water discharges.