Adsorption of Heavy Metals from Water and Waste Water Using Low Cost Adsorbents from Agricultural By-Products

Abstract

The use of agricultural by-products have been widely investigated as a replacement for current conventional methods for removing heavy metals from waste water, such as chemical precipitation, ion exchange, membrane technologies and electrochemical treatment. Although adsorption process using activated carbon are successfully applied for purification of potable water and the removal of organic pollutants in waste water, the expensive cost of the adsorbent material is still an issue for developing countries. Alternative adsorbents using low cost agricultural by-products are now becoming emergent. The application of low cost adsorbent for treating various adsorbate contaminants such as colour, trace metals, trace organics or chemical oxygen demand have been investigated worldwide. A focus on heavy metals contamination in waste water is a major concern due to their potential toxicity, persistence and tendency to become concentrated in food chains. With sources from more than 100 published papers low cost agricultural by-products have demonstrated outstanding capabilities in adsorbing heavy metal ions from aqueous solution. In this review, an extensive list of adsorbent literature has been compiled to provide a summary of information on a wide range of low-cost agricultural by-product adsorbents. The adsorption capacities depend largely on the characteristics of the adsorbent, pretreatment of the adsorbents, pH and the initial metal concentration.