Utilization of extracellular polymeric substances for removal of heavy metals from contaminated soils

In order to evaluate extracellular polymeric substances (EPS) for their effectiveness in removing heavy metals from contaminated soils, we examined the effect of concentration of EPS, initial pH of EPS solution and duration of EPS treatment for identification of the best way to achieve efficient removal of heavy metals from contaminated soils, compare the fraction distributions of heavy metals in soils before and after EPS treatment for determination of optimal remedying conditions, and study the kinetics of heavy metal extraction by EPS from contaminated soils for a better understanding of the remediation process. Our findings include EPS can be used to remove 83% of Cd, 45% of Pb and 48% of Zn from contaminated soils at an initial pH of 7-8 and a concentration of 180mg/L in 24 hours; metal-ion removal process can be modeled by fast and slow reactions, and the order of rate constant is Cd>Zn>Pb for fast reaction and Cd>Pb>Zn for slow reaction; EPS is more effective in removing the organically bound and carbonate fractions of heavy metals from contaminated soils. Our conclusion is therefore that, as a promising extractant, EPS can be used for removal of heavy metals from contaminated soils.