Biosorption of Heavy Metals by the Bacterial Exopolysaccharide FucoPol

Despite the efforts for minimizing the usage of heavy metals, anthropogenic activities still generate high amounts of wastewater containing these contaminants that cause significant health and environmental problems. Given the drawbacks of the conventional physical and chemical methods currently used, natural biosorbents (microbial cells or their products) arise as promising environmentally friendly alternatives. In this study, the binding efficiency of the polysaccharide secreted by Enterobacter A47, FucoPol, towards lead (Pb2+), cobalt (Co2+), copper (Cu2+) and zinc (Zn2+) cations was demonstrated. FucoPol revealed a higher performance for the biosorption of Pb2+, with a maximum overall metal removal of 93.9 +/- 5.3% and a specific metal uptake of 41.1 +/- 2.3 mg/gEPS, from a Pb2+ solution with an initial concentration of 10 mg/L, by a 5 g/L FucoPol solution. The overall metal removal decreased considerably (<= 31.3 +/- 1.6%) for higher Pb2+ concentrations (48 and 100 mg/L) probably due to the saturation of FucoPol's binding sites. Pb2+ removal was also less efficient (66.0 +/- 8.2%) when a higher FucoPol concentration (10 g/L) was tested. Pb2+ removal efficiency of FucoPol was maximized at pH 4.3, however, it was affected by lower pH values (2.5-3.3). Moreover, the FucoPol's sorption performance was unaffected (overall metal removal: 91.6-93.9%) in the temperature range of 5-40 degrees C. These findings demonstrate FucoPol's great potential for utilization as a biodegradable and safe biosorbent for treating waters and wastewaters contaminated with Pb2+.