Removal of heavy metal ions by modified activated carbons derived from agricultural waste as adsorbents

Abstract

The tremendous increase in the use of heavy metals over the past few decades has inevitably result an increased flux of metallic substances in aquatic environment. The removal of heavy metal pollutants is essential for safeguard of human beings, animals and plants. A number of technologies have been developed for the removal of toxic organic and inorganic constituents from water and waste water. The present study is undertaken to evaluate the efficiency of an activated carbon prepared from Ricinus communis (RCC) and Cajanus cajan L Milsp seed shells (CCC) as an agricultural waste products used for the removal of heavy metal ions from aqueous solution and industrial waste water. Adsorption isotherms are mathematical relationship used to describe the adsorption behaviour of a particular adsorbent-adsorbate combination. Three adsorption isotherms like Langmuir, Freundlich and Tempkin isotherms were applied. Kinetic studies showed that there is a good agreement between the calculated adsorption capacity (qe) and experimental adsorption capacity (qe) results were found in pseudo-second order kinetic model than the pseudo-first order kinetic model. The industrial waste water containing the metal ions like Fe(III), Ni(II) and Cr(VI) ions are subjected to the adsorption treatment and showed that the maximum removal of these metal ions are possible by sufficient amount of adsorbents are used. The amount of adsorbents required for removal of the metal ions is more for industrial waste water compared to metal ions in aqueous solution. The functional groups of the adsorbents and change in wave number before and after adsorption were identified by FTIR studies. The changes in the morphology of the metal ions adsorption on adsorbents surface was indicated by SEM images. Based on the removal percentage of Fe(III), Ni(II) and Cr(VI) ions on RCC, CCC, Ppy/RCC and Ppy/CCC, it concluded that modified activated carbons can be effectively employed for the removal of these toxic metal ions from aqueous solution and waste water. newline newline