CHROMIUM(VI) REMOVAL WITH ACTIVATED CARBONS

Several activated carbons, in powder and granular form, prepared from different raw materials and obtained by different activation procedure s, were used to remove chromium(VI) from solution. The porous texture of the activated carbons was characterized by adsorption of N-2/77 K a nd methylene blue/298 K. The Cr(VI)-adsorption experiments were carrie d out to analyze the influence of (i) pH, (ii) initial Cr(VI) concentr ation and (iii) carbon-solution contact time, on the efficiency of Cr( VI) retention by the activated carbons. The amount of Cr(VI) retained increased with increasing both pH and initial Cr(VI) concentration. At pH < 1, the retention of Cr(VI) was found to be affected by its reduc tion to Cr(lll), the lower the pH the greater the facility to be reduc ed to Cr(III). The extent of adsorption and reduction processes depend s on the porous texture, nature and preparation procedure of the activ ated carbons, the best performance being obtained with those prepared by physical activation.