Georgiou Efthalia, Pashalidis Ioannis, Raptopoulos Grigorios, Paraskevopoulou Patrina
Laboratory of Radioanalytical and Environmental Chemistry, Department of Chemistry, University of Cyprus, P.O. Box 20537, Cy-1678 Nicosia, Cyprus.
Inorganic Chemistry Laboratory, Department of Chemistry, National and Kapodistrian University of Athens, Panepistimiopolis Zografou, 15771 Athens, Greece.
Gels. 2022 Jul 29;8(8):478. doi: 10.3390/gels8080478.
The removal of polyvalent metal ions Eu(III) and Th(IV) from aqueous solutions using polyurea-crosslinked calcium alginate (X-alginate) aerogels has been investigated by batch-type experiments under ambient conditions and pH 3. The material presents relatively high sorption capacity for Eu(III) (550 g kg) and Th(IV) (211 g kg). The lower sorption capacity for Th(IV) compared to Eu(III) is attributed to the net charge of the dominant species in solution under the given experimental conditions, which is Eu for Eu(III), and Th(OH) and Th(OH) for Th(IV). Generally, the sorption is an endothermic and entropy-driven process, and it follows the Langmuir isotherm model. According to the FTIR spectra, sorption occurs via formation of inner-sphere complexes between the surface functional groups and the -metal cationic species. The presence of europium and thorium in the adsorbent material was confirmed and quantified with EDS analysis. To the best of our knowledge, this is the first report of an aerogel material used as an adsorbent for Eu(III). Compared to other materials used for the sorption of the specific ions, which are mostly carbon-based, X-alginate aerogels show by far the highest sorption capacity. Regarding Th(IV) uptake, X-alginate aerogels show the highest capacity per volume (27.9 g L) among the aerogels reported in the literature. Both Eu(III) and Th(IV) could be recovered from the beads by 65% and 70%, respectively. Furthermore, Th(VI) could also be quantitatively removed from wastewater, while Eu(III) could be removed by 20%. The above, along with their stability in aqueous environments, make X-alginate aerogels attractive candidates for water treatment and metal recovery applications.
在环境条件和pH值为3的情况下，通过间歇式实验研究了使用聚脲交联海藻酸钙（X-海藻酸盐）气凝胶从水溶液中去除多价金属离子铕（III）和钍（IV）的情况。该材料对铕（III）（550 g/kg）和钍（IV）（211 g/kg）具有相对较高的吸附容量。与铕（III）相比，钍（IV）的吸附容量较低，这归因于给定实验条件下溶液中主要物种的净电荷，对于铕（III）为Eu，对于钍（IV）为Th(OH)₂⁺和Th(OH)₃⁺。一般来说，吸附是一个吸热且由熵驱动的过程，并且遵循朗缪尔等温线模型。根据傅里叶变换红外光谱，吸附是通过表面官能团与金属阳离子物种之间形成内球络合物而发生的。通过能谱分析确认并定量了吸附剂材料中铕和钍的存在。据我们所知，这是关于气凝胶材料用作铕（III）吸附剂的首次报道。与大多数用于吸附特定离子的碳基材料相比，X-海藻酸盐气凝胶显示出迄今为止最高的吸附容量。关于钍（IV）的吸附，X-海藻酸盐气凝胶在文献报道的气凝胶中显示出最高的单位体积吸附容量（27.9 g/L）。铕（III）和钍（IV）分别可以从珠子中回收65%和70%。此外，钍（VI）也可以从废水中定量去除，而铕（III）可以去除20%。上述特性以及它们在水环境中的稳定性，使X-海藻酸盐气凝胶成为水处理和金属回收应用的有吸引力的候选材料。
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