Recovery of Lead(II) from Aqueous Solutions by Zea mays Tassel Biosorption

Abstract

Problem statement: Major adsorbent materials used in heavy metal ion removal from polluted aqueous streams are expensive and difficult to regenerate. In this study, the possibility of using Zea mays tassel, as an alternative low cost biosorbent material to remediate heavy metal pollution was investigated. Lead (II) was used because of its wide application in industrial products and well documented toxicity. Approach: Tassel was obtained from mature Zea mays cultivar R52 hybrid plants. The tassel was milled to a powder and was used to adsorb lead(II) ions from simulated solutions in batch experiments. The desorption of lead(II) was carried out using nitric acid and sodium citrate solutions. The adsorbent was characterized by FTIR, EDX and ESCA before and after application of lead(II) solutions. Results: For samples with concentrations of 100 mg L^-1 Pb(II), 94-98% was adsorbed and 57-74 and 57-67% recoveries were achieved with 0.5-5 M nitric acid and 0.01-0.2 M sodium citrate as the stripping solutions, respectively. EDX spectrum of pure tassel indicated that group 1 and 2 metals were the major exchangeable ions present on its surface. ESCA analysis picked up small amounts of lead(II) in the form of Pb(OH)⁺ and Pb(NH)⁺ ions on the surface of tassel adsorbent exposed to Pb²⁺ ions and none on pure tassel sample. Functional groups such as -H, -NH₂, -C = O and -COOH which are polar and are legends which are capable of binding heavy metals were identified by FTIR. Conclusion: The potential of Zea mays tassel to adsorb and recover heavy metals from aqueous solution was successfully demonstrated with Pb(II) sample solutions. The results obtained thus far demonstrated the possibility of using tassel powder in the removal as well as recovery of metals from aqueous solutions.