Optimization of Preparation Conditions for Activated Carbon from Date Stones by Chemical Activation using Response Methodology on Removal of Cr (VI) from Aqueous Solution

摘要

Aims: the objective of this work was to evaluate the adsorption potential of date stones based activated carbon for Cr (VI) removal from aqueous solution. Study design: Date stones (DS), agriculture wastes, available in large quantity in Tunisia, were used to prepare a low cost activated carbon (DSAC) for removing Cr (VI) from aqueous solution. Chemical activation method using sulphuric acid was employed for the preparation of the DSAC. Place and Duration of Study: Chemical Engineering Department, National School of Engineers of Gabes, between January and June 2013. Methodology: Response Surface Methodology (RSM) called central composite design (CCD) was applied to correlate the preparation variables (activation temperature, activation time and impregnation ratio) to the percentage removal of Cr (VI) from aqueous solution. The influence of the studied parameters on the Cr (VI) removal was also investigated by using the analysis of variance (ANOVA) to identify the significant variables.Moreover, the batch adsorptions of Cr (VI) on activated carbon prepared at optimal conditions were carried out and the experimental data were analysed by Freundlich and Langmuir isotherms models. Results: The results obtained showed that the optimum conditions for preparing activated carbon from DS for Cr (VI) adsorption were activation temperature of 150°C, activation time of 20 h and impregnation ratio of 4.85:l(acid/DS, wt basis) which resulted in 97.25 removal of Cr (VI) from aqueous solution. It was observed that experimental values obtained were in good agreement with the values predicted by the model. The adsorption studies indicated that the equilibrium data for adsorption of Cr (VI) on the optimum activated carbon was well described by both the Freundlich and Langmuir isotherm models which yielded maximum adsorption capacity of 58.82 mg/g at pH 2.0. Conclusion: The DSAC seems to be a good adsorbent for the removal of Cr (VI) from wastewaters.