A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering, School of Environment, Resources and Development

Thesis (M.Eng.) - Asian Institute of Technology, 1979

This report describes the work conducted on the removal. of chromium hexavalent from water employing activated carbon adsorption. The study consists of an initial batch phase and· then follows a continuous column operation. Two types of activated carbon (Actibon and Hydrodarco) were employed in batch adsorption study whereas only granular 1-C.l hydrodarco activated carbon was used for batch regeneration and continuous columns adsorption-desorption. Some of the major factors affecting removal of Cr(VI) by activated carbon were studied in batch process, i.e., pH, initial Cr(VI) concentration, carbon dose, and contact time. It was found that maximum adsorption was at pH value of 2.0 or less and at low Cr(VI) concentration (i.e. 10 mg/l) maximum adsorption is obtained within 10 minutes. It was also observed that the particle size of carbon does not change the magnitude of Cr(VI) removal. The free energy of specific chemical interaction, AG chem was computed by Gouy-Chapman-Stern-Grahame model giving average value of -3.04 Kcal/mole which is enough to influence the overall magnitude of Cr(VI) adsorption. Regeneration with one percent NaOH solution proved almost as efficient as with five percent or 10 percent NaOH and maximum desorption efficiency was 63 percent with 10 percent NaOH solution. Results of various phases of study indicated that activated carbon adsorption for Cr(VI) removal may have practical application in small water treatment plants.