Modification of coconut shell charcoal for metal removal from aqueous solutions

Abstract

Treatment of the contaminated aqueous solutions to improve their quality is indispensible for their reuse resulting in an emergent challenge to develop facile, nontoxic and less energy consuming techniques to purify water. Present study is therefore aimed at the synthesis of an adsorbent using agricultural waste i.e. coconut shell. The charcoal obtained from coconut shell was modified by acid activation and manganese doping following a simple chemical route. The products were characterized by scanning electron microscopy, energy dispersive X-ray analysis and infrared spectroscopy. Preliminary studies were carried out to compare the adsorption potential of acid modified coconut shell charcoal (AMCSC) and manganese doped coconut shell charcoal (MDCSC) for the removal of chromium (VI) and iron (III) from aqueous solutions. Various physicochemical parameters such as adsorbent dosage, initial metal ions concentration and pH were studied. MDCSC was found to be a better adsorbent for metals as compared to AMCSC and removed chromium more efficiently than iron from synthetic solutions i.e. 56.10% at optimum conditions i.e. 0.6 g/L adsorbent dosage, 10 mg/L initial metal ions concentration and pH = 3. The effect of adsorbents on color and conductivity of the aqueous solutions was also noted; slight variation in color of all the aqueous solutions with a maximum of 91.67% removal was observed.

Adsorption studies of hexavalent chromium ions on the dead biomass of Cystoseira indica

“…This behavior can be explained by the fact that under highly acidic conditions, the surface hydroxyl groups involved in the biosorption process are minimized and the biosorbent is positively charged due to the presence of more hydrogen ions; therefore, an electrostatic attraction is developed between the biosorbent and Cr(VI) anions such as HCr2O 7-, HCrO 4-, CrO4 2and Cr2O7 2present in the solution; all these factors result in the reduction of metal ions removal. Therefore, metal uptake increases to a certain pH value and then at higher pH values, interference with the diffusion of metal ions due to increase in hydroxyl ions concentration results in a lower percentage of metal ions removal [27,28]; slightly acidic conditions were selected to carry out the biosorption process.…”