Abstract Sorption distribution coefficient (Kd) of niobium-94 on minerals are an important parameter in safety assessment of intermediate-depth disposal of waste from core internals etc. The Kd of Nb on clay minerals in Ca(ClO4)2 solutions were, however, not successfully modeled in a previous study. The high distribution coefficients of Nb on illite in Ca(ClO4)2 solutions were successfully reproduced by taking Ca–Nb–OH surface species into account. Solubility of Nb was studied in Ca(ClO4)2 solutions and the results were reproduced by taking an aqueous Ca–Nb–OH complex species, CaNb(OH)6 +, into account in addition to previously reported Nb(OH)6 − and Nb(OH)7 2−. Based on this aqueous speciation model, the Ca–Nb–OH surface species responsible for the sorption of Nb on illite in Ca(ClO4)2 solutions was presumed to be X_OCaNb(OH)6. Although uncertainties exist in the speciation of aqueous Ca–Nb–OH species, the result of this study proposed a possible mechanism for high distribution coefficient of Nb on illite in Ca(ClO4)2 solutions. The mechanism includes Ca–Nb–OH complex formation in aqueous, solid and surface phases.

中文翻译：

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粘土矿物上 Nb 吸附模拟的思考

摘要 铌 94 在矿物上的吸附分布系数 (Kd) 是岩心内件等废物中深度处置安全评估的重要参数。然而，Nb 在 Ca(ClO4)2 溶液中粘土矿物的吸附分布系数 (Kd) 为在之前的研究中没有成功建模。通过考虑 Ca-Nb-OH 表面物质，成功再现了 Ca(ClO4)2 溶液中 Nb 在伊利石上的高分配系数。研究了 Nb 在 Ca(ClO4)2 溶液中的溶解度，除了先前报道的 Nb(OH)6 - 和Nb(OH)7 2-。根据该水相形态模型，推测负责在 Ca(ClO4)2 溶液中伊利石吸附 Nb 的 Ca-Nb-OH 表面物质是 X_OCaNb(OH)6。尽管含水 Ca-Nb-OH 物种的形态存在不确定性，但本研究结果提出了 Nb 在 Ca(ClO4)2 溶液中伊利石上高分配系数的可能机制。该机制包括在水相、固相和表面相中形成 Ca-Nb-OH 络合物。