TOPO体系萃取分离铑与铱

【作者】 马亮帮；

【导师】 范必威；

【作者基本信息】 成都理工大学 ， 分析化学， 2006， 硕士

【摘要】 铑在氯化物溶液中的化学性质十分复杂，它的分离与纯化一直是贵金属提取冶炼中的难题。 本文研究了活化—溶剂萃取技术分离铑的TOPO体系，以SnCl₂为活化试剂，从Rh（Ⅲ）—Sn（Ⅱ）—Cl^-体系中的萃取Rh（Ⅲ），考察了SnCl₂加入量，酸度，萃取剂浓度，料液恒温时间等条件对Rh（Ⅲ）萃取率的影响。在相比为1：1，Sn：Rh：4：1（摩尔比），恒温时间为1h，酸度为3mol·L^-1盐酸，一级萃取率可达98％以上，而且分相速度快。用加KClO₃的4mol·L^-1盐酸反萃，一级反萃率达95％。研究结果表明，含铑料液经SnCl₂活化处理后，能显著提高铑的被萃取性能，指出了活化—溶剂萃取技术分离回收铑的应用可行性。 本文还研究了在TOPO体系中，应用活化—溶剂萃取技术于Rh（Ⅲ）和Ir（Ⅳ）的选择性分离，研究结果表明： 在Ir（Ⅳ）和Rh（Ⅲ）的混合液的萃取体系中，在含氯化亚锡的RhCl₆^3-和IrCl₆^2-初试料液中IrCl₆^2-被还原为IrCl₆^3-，IrCl₆^3-不能被TOPO萃取，RhCl₆^3-被还原为Rh（Ⅰ），同时与SnCl₃^3-进一步络合形成一个双核桥联基配合物阴离子[Rh₂Cl_6-n（SnCl₃）_n]^4-（n=2—4），可以被TOPO萃取。 在反萃取体系中HCl和KClO₃的混合溶液产生具有很强的氧化性的氯气，可以利用它的氧化性来反萃铑。在反萃过程中，在络阴大离子中的Rh（Ⅰ）和SnCl₃^-被氧化为Rh（Ⅲ）和Sn（Ⅳ），破坏了[Rh₂Cl_6-n（SnCl₃）_n]^4-（n=2—4）的结构，Rh（Ⅲ）被反萃到水相中。由于受到IrCl₆^3-与IrCl₆^2-离子间价态变化的高频率性的微弱影响，在萃取过程中有一小部分IrCl₆^2-可能被TOPO萃取。在强氧化性的溶液中IrCl₆^2-不发生变化而仍然在有机相中，最后可以被硝酸反萃回收。无论在萃取还是在反萃铑的过程中，由于TOPO萃取SnCl₃^-和SnCl₆^2-阴离子的萃取率很高，SnCl₃^-和SnCl₆^2-始终保持在有机相中。最终所有的锡可以被氢氧化钠反萃下来，TOPO得到循环利用。 应用斜率法讨论了萃合物中各组分的物质的量的比，用紫外光谱UV，红外光谱FT—IR研究了探讨了TOPO萃取体系萃取铑的萃取机理。更多还原

【Abstract】 The separation and purification of rhodium from the other precious metals is one of the more difficult areas in precious metal refining, due mainly to the complex solution chemistry of rhodium in chloride solution.In this paper ,Tin （II） chloride was used as labilizing reagent, and the results of a systematic study on the solvent extraction of rhodium with tri-n-octylphosphine oxide（TOPO） in aqueous solution of Rh（III）-Sn（II）-Cr system by activation-solvent extraction technology are given. The effects of the molar ratio of Sn to Rh , TOPO concentration, acidity, aging time ect. were inspected. The optimum extraction conditions are as follows: the amount of added stannous chloride is four times that of Rh according to the molar ratio of Sn to Rh, the temperature of complex reaction 60℃, aging time 1 h, phase ratio 1:1, the Rh percentage extraction was over 98% .The percentage of stripping may reach to 95% through one stage with 4 mol·L^-1 hydrochloric acid containing potassium chlorate. The results of this study show that the extraction of rhodium can be improved observably by the labilizing progress with SnCLl₂ and indicate the feasibility of recovery and purification of rhodium by activation-solvent extraction technology.In the TOPO system , activation-solvent extraction technology was put forward to separate Ir（IV） and Rh（III） ions from a mixed chloride solution by extraction of rhodium .Stannous chloride was added to the original solution containing IrCl₆^2- and RhCl₆^3- ions before extraction. IrCl₆^2- was reduced to IrCl₆^3- , which cannot be extracted by TOPO, and RhCl₆^3- was reduced to Rh（I）, which was further complexed with SnCl₃^- forming a bi —nuclei bridged complex anions of the form[Rh₂Cl_6-n（SnCl₃）_n]^4-（n=2—4） and were extracted by TOPO simultaneously.A mixed solution of HC1 and KClO3 in which the strong oxidant chlorine was produced was used for stripping the rhodium. During the stripping process, both Rh（I） and SnCl₃^- in the complex anions were oxidized to Rh（III） and Sn（IV） destroying the structure of the [Rh₂Cl_6-n（SnCl₃）_n]^4-（n=2 — 4） anions; Rh（III）was stripped into the aqueous solution . The process was affected only slightly by the characteristic hing frequency of between IrCl₆^2- and IrCl₆^3- ions;a little amount of IrCl₆^2- might be extracted by TOPO in the course of extracting rhodium . IrCl₆^2- remained in the organic phase experiencing no change in the strong oxidative environment can be stripped with nitric acid. Because of their high percent extraction by TOPO, the SnCl3"" and SnCl₆^2- anions are always kept in the organic phase whether in the process of extraction or stripping the rhodium. Finally, all of the tin was stripped by sodium hydroxide and reclaimed. Meanwhile the TOPO was更多还原