The Behavior of Uranium in Forming Hydroxyl Aluminum Silicate Ion(Soil and Non-Crystalline Clays,Proceedings of the 13^<th> International Clay Conference)

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To study the interaction of uranium with HAS (hydroxyl aluminum silicate) in a solution, HAS was synthesized from the mixture of four solutions (25ml of 0.1M hydrochloric acid solutions, 40ml of 20mM aluminum chloride, 25ml of 20ppm uranium nitrate and 40ml of 20mM sodium orthosilicate) and 370ml of distilled water at the pH between 3.6 and 6.0. The XRD and FTIR analysis of solid products showed that the product was amorphous HAS. Analysis of the solutions filtered with four kinds of filters (5nm, 25nm, 100nm, 450nm) showed that HAS colloids containing uranium were formed between pH 4.3 and pH 5.4 and that the particle sizes of the HAS colloids are between 100nm and 450nm. At pH 5.6, the HAS colloids floating in the solution aggregate to large particles and precipitate; more than 99% of Al and U were depleted from the solution, and 72% of Si was depleted. This indicates that uranium co-precipitate with HAS. One of the possible mechanism of the co-precipitation is that the amount of uranyl-hydroxyl carbonate ion having negative charge increased with increasing pH, and this uranyl-hydroxyl carbonate anion was absorbed on HAS cation, thus uranium hydroxide precipitated with HAS.
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