New recovery system of novel metals by earth friendly polymer gel/liquid extraction method

我们成功地开发了一种利用单宁凝胶颗粒回收手机电子部件中的金(Au)、银(Ag)和钯(Pd)的新体系。天然缩合单宁是一种普遍存在且价格低廉、含有大量羟基的物质，它是由天然缩合单宁分子交联而成的凝胶颗粒。详细研究了这些新型金属在单宁凝胶颗粒上的吸附机理，建立了聚合物凝胶/液体萃取法。结果表明：(1)单宁凝胶颗粒对Au、Ag、Pd的吸附是通过Au、Ag、Pd离子对单宁凝胶颗粒表面金属的还原和单宁分子的氧化两个步骤进行的。(2)金属银的最大吸附容量高达930 mg-Ag/(g-干-单宁-凝胶)。(3)单宁凝胶对Au的吸附容量最大(8000 mg·Au/g干胶)。(4)对于Pd，PdCl2和PdCl2等含氯较少的Pd物种在单宁凝胶颗粒上的吸附能力比PdCl3^-和PdCl4^&lt；2-&gt；(5)根据Au-Pd水溶液的条件，确定了Au和Pd的最佳分离条件。

We succeeded in developing a novel recovery system of gold(Au), silver(Ag), and palladium(Pd) contained in the electric parts of mobile phones, utilizing tannin gel particles. Tannin gel particles were prepared by cross-linking natural condensed tannin molecules which is ubiquitous and inexpensive material having a lot of hydroxyl groups. The adsorption mechanisms of those novel metals onto the tannin gel particles was investigated in detail to establish the polymer gel/liquid extraction method. The following results were obtained.(1)The adsorption of Au, Ag and Pd onto the tannin gel particles was found to take place through the two steps : the reduction of Au, Ag and Pd ions to the metals on the surface of tannin gel particles and the oxidization of tannin molecules.(2)The maximum capacity of metallic silver adsorbed was extremely high as 930mg-Ag/(g-dry-tannin-gel). The adsorption rate of Ag was accelerated in the presence of small amount of Cu ions and Ag ions were recovered selectively in Ag-Cu mixtures.(3)The tannin gel showed the most highest adsorption capacity (8000mg-Au/g-dry-tannin gel that) for Au among the previous reports.(4)As for Pd, the Pd species containing fewer Cl such as PdCl^+ and PdCl_2, were more adsorbable onto the tannin gel particles than PdCl_3^-and PdCl_4^<2->.(5)It was elucidated that the separation of Au and Pd occurred perfectly depending on the conditions of Au-Pd aqueous solution.