Adsorption of Lead (ii), Chromium (vi) and Manganese (ii) metal ions from water using modified Pennisetum purpureum Schumach plant stalk

Abstract

Water pollution is a global problem affecting humanity. Availability of clean water is a fundamental prerequisite to public health safety and the survival of the human race as well as animals. However, pollution of river water by heavy metal ions deposition is a grave environmental problem. Presence of the heavy metals in the water, pose a serious health risk particularly to rural populations which rely majorly on the river water for domestic purposes. Several methods for elimination of the heavy metal pollutants from river waters have been previously employed. However, most of these methods are expensive and cumbersome, hence not sustainable. This research explored the potential of modified Pennisetum purpureum Schumach plant adsorbent in removal of Lead (II), Manganese (II) and Chromium (VI) ions from spiked water samples by adsorption. Surface analysis of the adsorbent using FTIR Photometer confirmed presence of functional groups such as -NH2, C=O and O-H responsible for adsorption of heavy metal ions. Concentration of heavy metal ions in water samples was determined before and after adsorption process using Atomic Absorption Spectroscopy (AAS) and means concentration computed. Effect of changes in pH on adsorption was investigated by conducting adsorption at three different pH conditions of 5, 7 and 9. Modification of the adsorbent surface improved its adsorption capacity. For instance, at pH 5, adsorption of Cr+6 increased from 12% to 14.82% when modified adsorbent was used. The modified adsorbent achieved greater % adsorption in all the three metals. Increase in the pH of adsorption from 5 to 9 had a reducing effect on the percent adsorption. At pH of 5 the % adsorption of Pb+2 reduced from 90.26% to 73.75% at pH of 9. This reductions in percentage adsorption were recorded for Pb+2 and Mn+2 ions but not significant for Cr+6 ions. These results show the potential of P. purpureum plant for use as an adsorbent in purification/detoxification of river water which would present a cheaper and more readily available alternative to many current adsorbents and adsorption methods in use. However further research is needed to determine the optimal set of conditions as well as the most suitable modification treatment for maximum adsorption.