Distribution of Cd(II) between (K,H)-montmorillonite and an aqueous solution of 0.10 M KNO3 at pH 4.5 and 298 K ― Comparison between potentiometric and miscible displacement experiments

摘要: Sorption of Cd(II) by (K,H)-montmorillonite from acidic (pH 4.5) background 0.10-M KNO3 solutions was investigated potentiometric titrations using a Cd sensitive electrode and saturated miscible displacement experiments columns packed with clay-quartz mixtures. Under the chosen experimental conditions, obtained results could conveniently be expressed in terms distribution coefficient KD (dm3 kg−1). Potentiometric were carried out at different initial concentrations adsorbing solids, ranging 9·10−6 M to 4·10−4 M. The values found decrease strongly increasing concentration solids. For free step input used column work (6.5·10−5 M), decreased 50.5 dm3 kg−1 approach limiting value 18.8 as solids increased 6.0·10−3 88.5·10−3 kg dm−3. Coagulation clay is proposed explain these results. Additional only one Cd-free (5.7 ± 0.5·10−5 M) varying tend support this suggestion. The close agreement (17.2 < 24.5) observed for experiments, indicating thus that time scales did not seem play determinant role system. Conditions under which pertinent transport can are discussed.