Abstract
Heavy metals ions in water have been a major preoccupation for many years because of their toxicity toward aquatic life, plants, animals, human beings and the environment. Water contaminated by heavy metal ions had become much more serious with a rapid development of industries and competitive use of fresh water in many parts of world. Therefore, heavy metals ions removal from water has become an important subject today. This present work reports a study about lead adsorption from aqueous solution onto agar beads with an extracellular polysaccharide (EPS) produced by the bacterium Paenibacillus polymyxa. The ability of produced beads to adsorb lead has been studied at different optimized conditions such as contact time, solution pH, biomass dosage and initial lead concentration. According to the experiments results, it was shown, that equilibrium was achieved in less than 120 min. The effect of pH investigated for values ranging from 1 to 5, showed maximum adsorption for pH 5. In order to determine the adsorption characteristics, Langmuir, Freundlich and Dubinin –Radushkevich adsorption isotherms were applied to the experimental data. The Freundlich isotherm provided the best fit for lead adsorption onto agar beads and the maximum adsorption capacity was found to be 111.11 mg.g-1 according to the Langmuir model. The results suggested that (Agar + EPS) beads could be suitable as a sorbent material for removal of lead ions from aqueous solutions.
