Biosorption of Cu+2 ions from wastewater by chemically immobilized Rhizobium BJVr 12 cells and exopolysaccharides

Abstract

The biosorption efficiency of biotraps consisting of chemically immobilized Rhizobium BJVr 12 exopolysaccharides in adsorbing Cu+2 ions was studied. Preliminary screening using the solubility test revealed that the most suitable microbial carrier is the ratio 2A1(OH); : 1 SiO; of 20% aluminum hydroxide and silicon dioxide. The effect of flow rate, time of collection, and kind of biotrap (w/ or w/o EPS) in the percent removal of Cu+2 ions in wastewater was determined. Atomic Absorption Spectroscopy was used to determine the residual Cu+2 ion concentration of the collected 10 ml samples. Three-factor Factorial in CRD to analyze simultaneously the effect of the three factors (flow rate, time of collection and kind of biotrap) and the Duncan’s Multiple Range Test to determine the optimum condition for each factor were used to analyze the data. Results showed that flow rate and time of collection significantly affect the percent removal of Cu™ ions in the wastewater. Maximum percent removal (%) of Cu+2 ions (98.25%) occurred at the 6-min (0.10 hr) time interval. A slower flow rate (1 ml/min) showed greater adsorption efficiency. Both biotraps (w/ and w/o EPS) exhibited high percentage removals of Cu+2 ions. Although the percent removal of Cu+2 ions by the biotraps without EPS is significantly greater than the biotraps with EPS for the 2.5 ml/min and 5 ml/min flow rates, no significant difference between the two was noted for the 1 m/min flow rate.