离子阻隔型胶囊状吸附剂的制备及其分离液相中铂钯的机理研究

Owing to the limited resource and expensive price of precious metal Pt and Pd, it is urgent to separate/recover them from related wastewaters. Adsorption technology as a better green method has good potential and prospect for selective recovery of PMs. In this study, the concept of “ionic barrier” is introduced to prepare capsulate adsorbents based on a simple encapsulation method for Pt and Pd recovery. The adsorbent is composed of an outer Ca2+-alginate shell (used as ionic barrier) and an inner N or S based ionic polymer solution (providing binding sites). Based on the fabricating Ca2+-alginate film, its penetrating performance for differently charged Pt and Pd ions will be evaluated. According to the changes of metal concentrations and species before and after penetration, the penetrating mechanism will be studied in detail. A series of capsulate adsorbents will be prepared and their selective sorption performances towards to Pt and Pd will be investigated by sorption tests. Moreover, the characterization analysis of the adsorbent before and after sorption will be carried out in order to illuminate the selective sorption mechanism. The present study is expected to provide a better technology and theory for the fabrication of highly selective adsorbents.

贵金属铂钯矿产资源有限且价格昂贵，相关工业废水中共存铂钯的分离和回收已成为现代社会亟待解决的问题。吸附分离技术作为一种更为绿色环保的工艺，在选择性分离铂钯应用中具有较大的潜力和前景。本研究引入“离子隔板”概念，设计一种简单的内封装合成方法，旨在构建胶囊状铂钯高选择性吸附材料，吸附剂组成结构为海藻酸钙凝胶薄膜（充当离子隔板）内包富含N或S官能团的离子型高分子化合物（用以提供吸附位点）。通过制备海藻酸钙水凝胶薄膜，研究其对不同带电性的铂钯离子的穿透性能，结合穿透前后离子浓度和形态变化，探究穿透机理。随后通过制备系列基于海藻酸钙作为外膜的胶囊状吸附剂，以铂钯混合溶液为吸附分离对象，设置吸附性能评价实验，考察各吸附剂选择性吸附铂钯的特性，结合吸附前后材料表征，阐明选择性吸附铂或钯的机理。本项目有望为今后高选择性吸附剂的研发提供理论和技术支持。

贵金属铂钯价格昂贵，但由于其特殊的理化性质被广泛应用在许多行业中。铂钯常以阴离子形态共存于相关废液中，因此，高效分离废液中的铂钯显得尤为重要。在众多的分离方法中，吸附法由于其成本低、易操作和良好的回收效率而被广泛应用。利用吸附法的关键点之一为研发高选择性的吸附剂。据此，本研究通过引入“离子隔板”概念和一种简单的内封装合成法，成功制备出了海藻酸钙水凝胶薄膜型隔板、三聚氰胺复合海藻酸钙胶囊型吸附剂和Cyphos IL 101复合壳聚糖胶囊型吸附剂。针对二元混合体系即Pt(IV)-Pd(II)，穿透实验结果表明制备出的水凝胶隔板能有效阻止铂钯阴离子形态穿过，但不会阻隔钯的中性形态，这为选择性吸附Pd(II)创造了条件；三聚氰胺复合海藻酸钙胶囊型吸附剂在此二元体系中能够选择性吸附Pd(II)，最佳吸附pH约为4.3，最大选择性吸附量为316.92 ± 9.50 mg/g（约是Pt(IV)的47倍），1 M 酸性硫脲为最佳吸附剂再生洗脱剂，通过简单的选择性吸附-解吸附过程，成功分别获得了纯度约为99.12%的Pd(II)的溶液和98.25%的Pt(IV)溶液，结合表征分析得出了可能的选择性吸附机理：当溶液中的铂钯存在形态分别为阴离子和中性分子时，吸附剂的海藻酸钙外壳可以阻挡阴离子形式的铂，但钯的中性形态可以顺利穿过外壳，进而可以与吸附剂内部的三聚氰胺结合，完成了选择性吸附过程。针对四元混合体系即Pd(II)-Co(II)-Ni(II)-Zn(II)，制备出的Cyphos IL 101复合壳聚糖胶囊型吸附剂在pH约为2时效果最佳，选择性吸附Pd(II)的最大吸附量为215.30 ± 5.12 mg/g，机理研究表明吸附剂的壳聚糖外壳具备阻隔溶液中金属阳离子的能力。本项目的研究结果可为高选择性吸附剂的研发提供一定的理论和技术支持。