Agricultural Waste as Adsorbent for Removal of Chromium (VI) from Aqueous Solution

Background & Aims of the Study: Since the chromium (VI) is a toxic, carcinogenic andnon-biodegradable element and can accumulate in the tissues, the presence and release ofthis element through the effluents is associated with dangerous effects on life cycle. Thus, itshould be removed from the effluents. In the present study, biosorption of Cr(VI) fromaqueous solutions using Rice husk was investigated.Materials and Methods: The various parameters such as pH, initial Cr(VI) ionconcentration, adsorbent dose, and contact time were optimized in batch adsorption system.The experimental data were modeled by Langmuir, Freundlich, Temkin and Dubinin-Radushkevich isotherm models. The pseudo-first order, pseudo-second order andintraparticle diffusion models were used to describe the kinetic data.Results: The results indicated that Cr(VI) removal efficiency increases by increasing ofcontact time and adsorbent dosage. Langmuir models demonstrated the best fit of theadsorption data. The maximum adsorption capacity was 38.4 mg/g at optimum conditionsof pH 5.0, contact time of 75 min, temperature of 30 ◦C and biomass dose of 5 g/L. Thebest correlation was provided by the second-order kinetic model.Conclusion: It can be concluded that the Rice husk can be considered as an effectiveadsorbent to remove the Cr(VI) from aqueous solution.

Keywords:

Rice huskAdsorptionChromium (VI)IsothermsIran