Selective separation and recovery of palladium by hybrid microcapsules

在乏核后处理过程中产生的高放废液中，含有多种有用元素。目前，高放废物是与玻璃颗粒混合并通过焦耳加热熔化的。玻璃制品被多层屏障覆盖，然后被放置在深部地质场地中。钯在熔化过程中容易析出，阻碍玻璃化。Pd是一种后矿金属，其分离回收可有效地促进废物处理，使其得以利用。此外，从“元素策略”的观点来看，分离回收方法的发展变得非常重要。本文介绍了对Pd~(2+)和Gt~(2+)具有高选择性的不溶性亚铁氰化物的制备和分离回收方法的进展。研究结果表明：(1)KCuFC表现出较高的摄取动力学(10min内摄取平衡，99.9%摄取)，对Pd的摄取顺序为KCuFC&GT；KNiFC&GT；KCoFC；由于离子交换/氧化和还原作用，Pd~(2+)和Gt~(2+)在亚铁氰化物上的吸附是非常特殊的。在0.3-7M HNO_3存在下，Pd~(2+)&Gt~(2+)的吸收率可达90%以上。吸附后的亚铁氰化物经热分解和酸处理后，可回收高纯度的Pd~(2+)作为不溶性残渣。(2)采用海藻酸凝胶基质微胶囊化法制备细粒亚铁氰化物，并进行柱层吸附。Pd~(2+)~(2+)和Gt~(2+)离子的穿透容量为0.031 mmoL/g，92%的Pd可被硫脲洗脱。(3)以滤纸为载体，制备了不同厚度的海藻酸盐膜。Pd~(2+)~(2+)~(2+)选择性吸附在海藻酸盐膜上。因此，包裹不溶性亚铁氰化物的海藻酸膜有望作为离子交换过滤器和液膜选择性分离和浓缩Pd~(2+)。

In the high-level liquid wastes (HLLWs) generated from reprocessing process of spent nuclear, various useful elements are contained. At present, HLLWs were mixed with glass granules and melted by Joule heating. The glass products are covered with multi-barrier and then disposed in a deep geological site. Palladium tends to precipitate during melting process and to hinder the vitrification. The separation and recovery of Pd, a kind of rear metals, are thus effective for the advancement of waste treatment and enables its utilization. Further, the development of separation and recovery method becomes very important from the standpoint of "element strategy".The present paper deals with the preparation of insoluble ferrocyanides with high selectivity towards Pd^<2+> and the advancement of separation and recovery methods. The results of this study are as follows: (1) KCuFC shows relatively high uptake kinetics (uptake equilibrium within 10 min and 99.9% uptake), and the order of Pd^<2+> uptake is KCuFC > KNiFC > KCoFC. The adsorption of Pd^<2+> on ferrocyanides is very specific due to ion-exchange/oxidation and reduction. The uptake of Pd^<2+> is over 90% in the presence of 0.3-7 M HNO_3. After adsorption, the ferrocyanide was thermally decomposed and treated with acid, and then PdO with high purity was recovered as insoluble residue. (2) The fine ferrocyanides were granulated by the microencapsulation with alginate gel matrices for the column adsorption. The breakthrough capacity of Pd^<2+> ions was estimated to be 0.031 mmol/g and 92% of Pd can be eluted with thiourea. (3) The alginate films with different thicknesses enclosing KZnFC were prepared by supporting with filter paper. The Pd^<2+> ions were selectively adsorbed on the alginate film. Thus the alginate film enclosing insoluble ferrocyanides are expected for the selective separation and concentration of Pd^<2+> as an ion-exchange filter and a liquid membrane.