Role of microbial exopolymeric substances (EPS) on chromium sorption and transport in heterogeneous subsurface soils: II. Binding of Cr(III) in EPS/soil system

Laboratory batch sorption and column experiments were performed to investigate the effects of microbial EPSs isolated from Pseudomonas putida P18. Pseudomonas aeruginosa P16 and Pseudomonas srutzeri P40 on Cr(III) mobility in heterogeneous subsurface soils. Our batch and column results indicate that microbial EPS may have a pronounced effect on Cr(III) sorption and transport behavior depending on system conditions (e.g., pH, type of EPS). While EPS had no effect on Cr(III) sorption at pH < 5, it led to a significant decrease in Cr(III) sorption under slightly acidic to alkaline pH range. Column experiments performed at pH 7.9 suggest that, in the presence of EPS, chromium(III) was significantly mobilized relative to non-EPS containing system due to the formation less sorbing and highly soluble Cr-EPS complexes and competition of EPS against Cr for surface sites.