Investigation of Removal Characteristics of Heavy Metal Ions by Natural Adsorbents

Abstract

Rice husk, which is a relatively abundant and inexpensive material, is currently being used as the source of activated carbon an adsorbent for the removal of various pollutants from water. Activated carbon was prepared and characterized from rice husk. Rice husk was collected from local rice mill and used as raw material for producing activated carbon. Low-cost furnace was designed from locally available pottery and very slow burning of rice husk in presence of insufficient oxygen was applied for the preparation of activated carbon. The carbonized temperature and time was 350-550 C and about 3.0 hours respectively. The percentage of the yield in this method is about 25 (wt) %. Prepared activated carbon was characterized by a series of' experiments such as ash content, volatile content, moisture content, fixed carbon content, porosity and adsorption study. The prepared activated carbons contain 39.47% ash and 35.98% fixed carbon. SEM photographs exhibit that the prepared activated carbon possesses significant number of micropores, mesopores and macrospores. XRD analysis provides information that the prepared samples are amorphous in nature. All these observed properties indicate that the prepared samples might be used as good adsorbent.SEM photograph before and after adsorption clearly showed the evidence in favor adsorption. Prepared activated carbon used as potential adsorbent for methylene blue.Pb2+and Hg2+ in aqueous solution. Methylene blue showed maximum adsorption at pH 6.0. With increasing the sizes of adsorbents the extent of adsorption decreased at two investigated temperatures, 30 °C and 40 T. The equilibrium time for the adsorption was found to be about 180 minutes. Under all conditions amount of adsorbed increased with increasing the concentration of adsorbates. The experimental data have been found to be fit into Freundlich adsorption isotherm suggesting the chemisorption occurred. Both Pb2+and Hg2+ in aqueous solution showed maximum adsorption at pH 5.7 and 150 Rev/min shaking frequency. The equilibrium time for the adsorption in both cases were found to be about 180 minutes under all conditions and the amount of' adsorption increased with increasing the concentration of adsorbates. The experimental data have been found to be fit into Freundlich adsorption isotherm suggesting the chemisorptions occurred.