Pentavalent Ions Sorption on Bentonite Clay

Sorption of pentavalent radioactive pollutants from ground and sea water to bentonite clay was studied under various conditions using Monte Carlo simulation. The primitive model was used in which water of a certain dielectric permittivity constant is contained, and the ions are treated as charged hard spheres with the same diameter. Furthermore, the clay platelets were considered to be two parallel planer uniformly charged surfaces. Depending on a series of simulations in grand canonical ensemble, the average electrical double layer concentration and the retention coefficient of pentavalent cations were calculated as a function of pentavalent concentration in the aqueous solution, temperature of the whole system, surface charge density on the platelets and ionic strength of the solution. The results of this study indicate that, the sorption behavior of pentavalent cations is strongly influenced by the previously mentioned parameters. In particular, the average electrical double layer concentration of pentavalent cations increases by increasing the bulk concentration of pentavalent pollutants and the surface charge density. This average concentration decreases by increasing the ionic strength. However, the retention coefficient of pentavalent cations tends to increase by increasing the surface charge density whilst it becomes less by increasing the pentavalent concentration in the bulk and the ionic strength. Moreover, the average concentration and the retention coefficient of pentavalent cations decrease very slightly with increasing temperature. Besides, the results show that bentonites are suitable sorbents for recovery and sorption of pentavalent radioactive pollutants from different aqueous solutions.