Biosorption Characteristics of Extracellular Polymeric Substance (EPS) Produced by Rhizobium radiobacter for Removal of Cu (II) and Mn (II) Ions Form Aqueous Solutions

This paper deals with the extracellular polymeric substance (EPS) of Rhizobium radiobacter F2 used as a novel biosorbent to remove Cu (II) and Mn (II) ions from aqueous solutions. The Cu (II) and Mn (II) ions biosorption characteristics of the EPS were examined as a function of initial pH, contact time and EPS concentration. The proper pH of the aqueous solution was found to be 6.0 for both the biosorption of Cu (II) and Mn (II). Biosorption equilibrium times of Cu (II) and Mn (II) were achieved in 1.0 h. The maximum biosorption capacities under optimum conditions of Cu (II) and Mn (II) on the EPS were determined to be 45.30 ±± 1.62 mg/g and 28.86 ±± 1.28 mg/g, respectively. The fitness of the biosorption data for Langmuir and Freundlich isotherm models was investigated. It was found that biosorption of Cu (II) and Mn (II) ions onto the EPS were better suitable to Langmuir than Freundlich isotherm model. Competitive biosorption of Mn (II) and Cu (II) ions was also investigated to determine the selectivity of the bioflocculant.