Volume No. 3 Issue No.: 1 Page No.: 228-243 July-Sept 2008

 

MECHANISMS OF Cr(VI) REMOVAL FROM SYNTHETIC WASTEWATER BY LOW COST ADSORBENTS

 

Manjeet Bansal, Diwan Singh, V.K. Garg* and Pawan Rose

Deptt. of Civil Engineering, National Institute of Technology, Kurukshetra (India)

 

Received on : March 7, 2008

 

ABSTRACT

 

Chromium in the industrial effluent is a major concern for the environment. Chemical precipitation methods are commonly employed for the removal of chromium but this leads to the formation of chromo-bearing solid waste and it is uneconomical when the concentration of chromium in the effluent is low. Ion exchange and membrane separation methods are relatively expensive. In this study the removal of Cr(VI) from aqueous solutions by batch adsorption technique using different low cost adsorbents was investigated. Adsorbents such as rice husk a surplus agricultural byproduct, saw dust a timber industry waste were used to determine adsorption efficiency. The influence of pH, adsorbent dose, initial Cr(VI) concentration and contact time on the selectivity and sensitivity of the removal process was investigated. Adsorption process was found to be highly pH dependent. Optimum pH for adsorption of Cr(VI) was found to be 2.0. Kinetic studies were performed to understand the mechanistic steps of the adsorption process and rate kinetics for the adsorption of Cr(VI) was best fitted with pseudo 2nd order kinetic model. EDAX of the Rice husk and Sawdust (native and metal loaded) were recorded to explore the elemental constitution of the adsorbents. Reusability of the adsorbents was examined by desorption in which HCl eluted 84.08% and 79.63% Cr(VI) from Rice husk and Sawdust, respectively. Langmuir and Freundlich isotherms were applied to the adsorption process and their constants were evaluated. The adsorption capacity qmax calculated from Langmuir isotherm obtained for the different adsorbents showed that sawdust was the most effective among the selected adsorbents for the removal of Cr(VI) from aqueous solutions.

 

Keywords : Cr(VI), Rice husk, Saw dust, Low cost adsorbents, Langmuir and Freundlich isotherms

 

 

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