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In view of environmental concern, sorption of radium on natural bentonite mineral (Aleppo, Syria) was investigated using a batch-type method. Data were expressed in terms of distribution coefficients. An attempt to increase the selectivity of bentonite for radium was made by preparing M-derivatives. Loss of mineral crystallinity in acidic media and the formation of a new phase, such as BaCO3, in Ba-derivative were evidenced by XRD characterizations. Of the cationic forms, Na-bentonite showed the highest affinity. Mechanisms of radium uptake were studied using M-derivatives and simulated radium solutions. The obtained results indicated that surface sorption/surface ion exchange were the predominant processes. The distinct sorption behaviour observed with the Ba-form was, possibly, a reflection of radium coprecipitation with barium carbonate. The competing order of macro components, likely present in waste streams, was investigated by studying different concentrations of the corresponding salt media. Sodium was found to be the weakest inhibitor. The performance of natural bentonite and the most selective forms, i.e. Ba- and Na-derivatives, to sorb radium from actual oil co-produced waters, collected form Der Ezzor Petroleum Company (DEZPC), was studied. This showed the influential effect ofpH compared with other parameters.

Birnessite, antimonysilicate, and their cation-exchange derivatives were tested to take up thorium. Sorption experiments were performed in different concentrations of acid, sodium, potassium, and calcium nitrate solutions in order to evaluate the influence of cations that are likely to be present in waste effluents. Variation in the magnitude and mechanism of thorium sorption on the exchangers was ascribed to structural differences and the exchange properties of the materials, as well as the aqueous chemistry of thorium. The work included investigation of thorium solution' pH in controlling the sorption process. In acidic solutions, H-antimonysilicate proved to be the best sorbent. The structure of M-H-birnessite allows facile mobility of the interlayer cations with little structural rearrangement, making it of great importance for ion-exchange use in salt conditions. Potassium had the most, and sodium the least effect on thorium selectivity by birnessites, when they are present as macro components. Conversely, calcium ions did greatly inhibit the sorption behavior of thorium on Ca-antimonysilicate. Studying the effect of thorium solution' pH reflected the fact that the microcrystal modifications of birnessites occurred during experiments. In summary, H-birnessite showed superior uptake for thorium in comparison to other materials investigated in the literature, which reflects the characteristics of the material selectivity.