Removal of Chromium(VI) from waste water by using adsorbent prepared from green coconut shell

Abstract

In recent years, industrial effluents containing heavy metals have become a major problem. For the removal of heavy metals, several types of adsorbents have been developed economically from waste materials by different processes. In present work, “Green Coconut Shell,” which is waste material, was chosen for the development of adsorbent by treatment with orthophosphoric acid economically. This adsorbent was used for the removal of chromium(VI) in batch mode in concentration and temperature range of 10–100 mg/g and 10–80°C, respectively. The influence of contact time, temperature, concentration, adsorbent dose, particle size, and pH was studied. Langmuir and Freundlich isotherm models were fitted for equilibrium data with maximum adsorption capacity of 22.96 mg/g. Pseudo-second-order model also confirmed that the chromium(VI) uptake capacity of adsorbent was due to pore, film, and particle diffusion. To know the properties of adsorbent different analysis such as XRF, X-ray diffraction, scanning electron microscope, energy dispersive spectroscope, and particle size distribution using Malvern analyzer were studied. The adsorption capacity of green coconut shell-based adsorbent achieved was greater than 90% for 10 mg/l solution and contact time of 30 min.

Keywords:

• Green coconut shell
• Orthophosphoric acid
• Adsorption
• Concentration
• Chemical activation
• Hexavalent
• Contact time

Acknowledgement

The authors gratefully acknowledge the support for this work by National Research Foundation (NRF) of South Africa (Ref: IFR2011032900004).