Removal of strontium from aqueous solutions by sodium dodecyl sulfate-modified palygorskite

Palygorskite (PAL) was modified with sodium dodecyl sulfate (SDS) for the removal of Sr(II) from aqueous solutions. Analysis of the structural characteristics of PAL before and after modification showed that PAL was successfully modified with SDS. Sorption experiments were conducted in batch mode under optimum conditions to evaluate the effect of initial pH and co-existing ions on the removal of Sr(II) by SDS-modified PAL. The equilibrium sorption isotherm data for Sr(II) were analyzed using Freundlich and Langmuir isotherm sorption equations, and the data fitted well to the Freundlich isotherm model. Pseudo-first-order and pseudo-second-order kinetic models were examined, and the sorption of Sr(II) showed better agreement with the pseudo-second-order kinetic model (r2 > 0.99). The desorption experiments indicated that the SDS-modified PAL having sorbed Sr(II) does not release significant amounts of Sr(II) into the environment under natural conditions, thus avoiding secondary pollution.