For the successful solution of the problem of safe high level waste (of which Sr is one of the most dangerous component for biosphere) it is necessary to choose suitable materials for engineered barrier construction. The aim of this work was to study the sorption of Sr by red muds from various Russian aluminium-works. We chose the red mud because it consists of the ferric oxide and hydroxide, hydrogranate and hydroalumosilikate of Na are known as a good sorbents.
The sorption/ desorption experiments were carried out using the batch method at room temperature. Weighed amounts of the red mud samples were kept in contact with known volumes of SrCl2 solution for certain times. The degree of the attainment of equilibrium was determined by periodic analysis of solution. Concentration of Sr in solutions were determined before and after runs. Chemical analysis were carried out using atomic adsorption spectrometry. Studies of the desorption of strontium from red muds followed the same pattern. Red mud samples with the known Sr content were subjected to repeated extraction by the distilled H2O, after which aliquots of the filtrated liquids were analyzed for Sr. Furthermore the influence of the presence Mg2+- cations in solutions on the sorption Sr was studied.
It was found that generally red muds adsorb Sr much more than the well known natural and technical sorbents. The
magnitude of the value of saturation capacity reached 420±24 meq/100g. It was found also t hat the adsorption - desorption phenomenon is irreversible, and values of desorption are small. This suggests that the formation of a hard soluble compound of Sr keeps pace with adsorption phenomenon.
It may be concluded that various samples of red mud adsorb and desorb Sr in a similar way. The differences observed are only in the magnitudes of distribution coefficient values which may be a reflection of their different composition and pH. The presence of Mg2+-cations in solutions had little effect on the sorption of strontium when the Mg2+-ion concentration is less than 10-2 % (and initial Sr2+-ion concentration is more 5*10-3 %).