Sorptive removal of cobalt, strontium and cesium onto manganese and iron oxide-coated montmorillonite from groundwater

Applicability of montmorillonite, manganese oxide-coated montmorillonite (MOCM) and iron oxidecoated montmorillonite (IOCM) as backfill materials in permeable reactive barrier (PRB) to remediate contaminated groundwater was investigated. Single-and bi-solute competitive sorptions of Co, Sr and Cs were conducted. The Freundlich, Langmuir and Dubinin-Radushkevich models fitted the single-solute sorption data well (R² > 0.95). Maximum sorption capacities (q_ml) of Co and Sr predicted by the Langmuir model were in the order of MOCM (0.37 mmol/g for Co and 0.28 mmol/g for Sr) > montmorillonite (0.27 mmol/g for Co and 0.19 mmol/g for Sr) IOCM (0.23 mmol/g for Co and 0.21 mmol/g for Sr), while those of Cs were in the order of montmorillonite (1.11 mmol/g) > MOCM (0.68 mmol/g) > IOCM (0.62 mmol/g). In the bi-solute sorptions, the sorbed amount of one solute decreased due to the presence of the other competing metal ion. Langmuir model parameters for single-solute (q_mLmL and b_L) and bi-solute (q_mL and b_L) sorptions were compared to analyze the effect of competition between the metal ions. The competitive Langmuir (R² > 0.81) and P-factor (R² > 0.82) models predicted the bi-solute competitive sorption data well but not the SRS model (0.003 < R²< 0.97).