Competitive adsorption behavior and mechanism of loess towards Pb(II), Cu(II) and Cd(II)

Lead, copper, cadmium is three kinds of typical heavy metal contaminants which can be used to simulate the solution of composite contaminate. The factors including the concentration and soil-water ratio are studied to investigate the competitive adsorption behaviors of loess towards Pb(II), Cu(II) and Cd(II). The adsorption test results can be interpreted by three isotherm models (i.e., Langmuir, Freundlich and D-R models) to certain extent. The preference ranking of loess to three heavy metal ions is Pb(II)>Cu(II)>Cd(II). Compared with those of single adsorption, the adsorption capacities of the competitive ions on loess decrease to some extent. Higher initial concentration of heavy metal ions leads to larger optimum adsorption amount of loess, and the adsorption removal efficiency decreases at the same time. The removal efficiency of three heavy metal ions from aqueous solution can be increased by increasing the solid-liquid ratio. The results may provide an evidence for loess as the containment barrier system as well as the adsorbent removing heavy metal containment in aquatic environment.