الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
Hexavalent chromium exists in the waste water produced by different industries like pigments, leather making, electroplating, corrosion inhibitors, etc. It’s very toxic and carcinogenic so it must be removed from waste water to prevent its harmful environmental effects. Several techniques could be used for removal of hexavalent chromium such as: adsorption on Granular Activated Carbon (GAC), electro-coagulation, chemical precipitation, biosorption. Reduction of hexavalent chromium to the less toxic trivalent chromium is considered to be the most effective and cheapest method to remove Cr+6. The goal of the present work was to study the factors affecting the rate of removal of Cr+6 inside tank reactor suitable for conducting liquid solid diffusion controlled reactions. The vessel was fitted with a fixed bed of iron cylinders placed at the bottom of the vessel. The performance of the reactor in conducting diffusion controlled reactions was evaluated in terms of the mass transfer coefficient. The diffusion controlled dissolution of iron in acidified dichromate technique was used to determine the mass transfer coefficient under different conditions such as solution velocity, bed height and concentration of sulfuric acid. The present study revealed that the mass transfer coefficient and the rate of reduction reaction increased by the increase in H2SO4 concentration and solution velocity. The rate of reduction was found to decrease by increasing in the bed height. Mass transfer data were correlated using the method of dimensional analysis, the following overall mass transfer correlation was obtained