察尔汗盐湖铷资源利用——从基础认知到技术创新

Economically Utilization of the Rubidium resources in Qarhan Salt Lake: From Fundamental Study to Technology Innovation

铷是诸多高新技术领域中的关键元素。青海察尔汗盐湖卤水中蕴藏着丰富的铷资源,但由于铷浓度极低,且与大量钠、钾、镁等离子共存,提取难度极大。利用已知技术从察尔汗盐湖卤水中直接提取铷难以满足经济性约束的前提,这成为察尔汗盐湖铷资源难以利用的症结之一。本文从理论和实验两个方面分析了NaCl+KCl+RbCl+MgCl_(2)+H_(2)O体系中(K,Rb)Cl和铷钾光卤石固溶体—水溶液平衡对察尔汗盐湖卤水中铷分布的制约作用,确定了钾光卤石基固溶体是控制卤水中微量铷进入固相的关键矿物,钾光卤石的形成会使卤水中的铷浓度迅速下降至极低水平。用光卤石矿生产氯化钾,铷几乎全部进入氯化钾产品中,这一结论得到了现场盐田样品分析结果的支持。在上述新认知的启发下,我们设计了从察尔汗盐湖氯化钾产品中浓缩铷的工艺流程,并进行了公斤级小试和吨级放大试验,获得了铷浓度为400 mg/L的富铷料液,其中镁/铷比和钾/铷比均大幅降低;此外,进一步利用本团队成熟的t-BAMBP萃取方法可高效提取氯化铷,其工艺综合成本约为2 090元/kg,较好满足了察尔汗盐湖铷资源开发的经济性前提。

Rubidium is a critical element in high-tech fields.Extensive rubidium exists in the Qarhan salt lake in Qinghai province.However,due to the very low concentration,e.g.5~10 mg/L,and the very concentrated sodium,potassium and magnesium coexisted with rubidium,the extraction of rubidium from Qarhan salt lake brine economically is a very difficult challenge.In respect of the economical aspect,nearly all the well documented technologies are not adapted to the rubidium resource of Qarhan salt lake,which is one of the bottle neck for the development of rubidium utilization in Qarhan for a long time.In this study,we highlighted the key function of aqueous-solid solution,i.e.(K,Rb)Cl and carnallite type solid solution,in the NaCl+KCl+RbCl+MgCl_(2)+H_(2)O system on controlling the fate of the rubidium during the processing of the Qarhan brine in solar pond and KCl factory.We find that the K-carnallite is a key mineral for understanding the mechanism of the behavior of rubidium in solids,and the precipitation of K-carnallite will bring nearly all the rubidium in brine with them resulting very low rubidium concentration in residual brines.When the K-carnallite is used for the production of KCl,nearly all the rubidium in it will further enriched in the final KCl product.These findings derived from fundamental studies are also well supported by our analysis of the fieldsamples obtained from Qarhan solar pond and KCl factory.Inspirited by above fundamental knowledge,we designed a flow sheet for concentrating rubidium from the KCl produced using Qarhan salt lake brine and performed laboratory and bench-scale experimental studies.Finally,we obtained a concentrated brine with rubidium 400 mg/L,in which the mass ratios of Mg/Rb and K/Rb have been significantly decreased compared with any other flows of solar pond and KCl factory.Rubidium can be extracted from the concentrated brine by combining the t-BAMBP extraction process known well by us.The rough cost for the production of 1 kg RbCl is about 2090 RMB.