Octa Journal of Environmental Research Jul. – Sept., 2016 International Peer-Reviewed Journal ISSN 2321 3655 Oct. Jour. Env. Res. Vol. 4(3): 208-229 Available online http://www.sciencebeingjournal.com Octa Journal of Environmental Research Review Article AGRICULTURAL WASTE MATERIALS AS BIOSORBENTS FOR THE REMOVAL OF HEAVY METALS AND SYNTHETIC DYES– A REVIEW Hina Khatoon a and Jai Prakash Narayan Rai b Department of Environmental Science, G.B. Pant University of Agriculture and Technology, Pantnagar (U.S. Nagar), Uttarakhand, India Corresponding Author‘s e-mail: hinakhatoon29@gmail.com Received: 29 th Aug. 2016 Revised: 12 th Sep. 2016 Accepted: 21 st Sept. 2016 Abstract: This review discusses the potential use of agricultural waste based bio-sorbents for sequestering heavy metals and synthetic dyes in terms of their adsorption capacities, cost effectiveness, binding mechanisms, operating factors and pre-treatment methods. Agricultural wastes are known to be rich in functional carboxyl and hydroxyl groups which facilitate binding of cation on to the surface. Adsorption by using low cost alternative adsorbent is a fascinating area as it has dual benefits i.e. water treatment and waste management. The literature survey indicates that agricultural waste based bio-sorbents have shown equal or even greater adsorption capacities compared to conventional adsorbents. In most cases, chemical pre-treatments bring about an obvious improvement in metal uptake capacity. However, there are still several gaps, which require further investigation, such as (i) searching for novel, multi-function agricultural waste based bio-sorbents, (ii) developing cost- effective modification methods and (iii) assessing agricultural waste based bio-sorbents under multi- metal and real wastewater systems. Once these challenges are addressed, the replacement of traditional adsorbents by agricultural waste based bio-sorbents in decontaminating heavy metals and dyes from wastewater more efficiently could be achieved. Keywords: Adsorption capacities; Agricultural wastes; Bio-sorbents; Heavy metals; Synthetic dyes. Postal Address: Department of Environmental Science, G. B. Pant University of agriculture and Technology, Pantnagar-263145, Uttarakhand, India, Phone: +91 9410579950 INTRODUCTION Water is vital requirement of life and used for various household as well as industrial activities. The rapid and continuous growth of industries over the last few decades has increased fresh water demand and thereby also the amount of waste water discharged. This waste water contains many heavy metals and synthetic dyes, which often have been regarded as hazardous pollutants because of their potential toxicity to human health. Many methods available for the removal of pollutants from aqueous solution, include chemical precipitation, ion exchange, membrane separation process, biological degradation, chemical oxidation, solvent extraction, and adsorption. However, these methods have several disadvantages such as limited metal concentrations specificity, generation of huge toxic sludge and high capital costs. On the contrary, adsorption is found to be the most effective and prolific technique due to its convenience, cost effectiveness, ease of operation, high adsorption capacities and versatility, which explain why the adsorption method is more economical for heavy metals and dyes removal (Yildiz, et al., 2005; Yan, et al., 2007). Recently scientists have paid much attention on the use of biological-based materials for pollutants removal from different waste waters because of presence of several carboxyl, hydroxyl and amino groups over their surface, which facilitates the biosorption process (Ay, et al., 2012). Potential applications of agricultural wastes as low-cost biosorbents