ABSTRACT:In this research, adsorption of chromium (VI) ions on wheat bran has been studied through using batch adsorption techniques. The main objectives of this study are to 1) investigate the chromium adsorption from aqueous solution by wheat bran, 2) study the influence of contact time, pH, adsorbent dose and initial chromium concentration on adsorption process performance and 3) determine appropriate adsorption isotherm and kinetics parameters of chromium (VI) adsorption on wheat bran. The results of this study showed that adsorption of chromium by wheat bran reached to equilibrium after 60 min and after that a little change of chromium removal efficiency was observed. Higher chromium adsorption was observed at lower pHs, and maximum chromium removal (87.8 %) obtained at pH of 2. The adsorption of chromium by wheat bran decreased at the higher initial chromium concentration and lower adsorbent doses. The obtained results showed that the adsorption of chromium (VI) by wheat bran follows Langmuir isotherm equation with a correlation coefficient equal to 0.997. In addition, the kinetics of the adsorption process follows the pseudo second-order kinetics model with a rate constant value of 0.131 g/mg.min The results indicate that wheat bran can be employed as a low cost alternative to commercial adsorbents in the removal of chromium (VI) from water and wastewater.

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Aluminum and ferric salts are widely used as coagulants in water and wastewater treatment. They are effective in removing a broad range of impurities from water, including colloidal particles and dissolved organic substances. As well as traditional additives, such as aluminum sulphate ("alum") and ferric chloride, other products containing prehydrolized metal ions such as polyaluminum chlorides are now commonly used. The aim of this study was to develop a model for coagulation/flocculation process using various coagulants. It is attempted to have an acceptable model for prediction of coagulant doses based on the desired turbidity. In this study, three coagulants including polyaluminum chloride (PACl), alum and ferric chloride were used. The results obtained indicated that modeling can be used for the prediction of these coagulants doses for Tehran drinking water. This could provide an alternative to the experimental jar test for determining coagulant doses for the treatment of raw waters.