The key to achieving sustainable metal extraction development is to avoid the generation of high-salt wastewater from the source. Here, a new system for the extraction and separation of lanthanide elements Eu(III), Gd(III) and Tb(III) from the acetic acid solution using HEHEHP (2-ethylhexyl hydrogen-2-ethylhexylphosphonate) was studied. The corresponding parameters including contact time, HEHEHP concentration, concentrations of rare earth metal ions and acetic acid in the initial solution, aqueous/organic phase volume ratio (R(A/O)), and temperature were considered to optimize the conditions for the separation of different rare earth elements. The results showed that the separation coefficients of Tb(III)/Gd(III) and Gd(III)/Eu(III) in the acetic acid system were approximately 6.2 and 1.7, with HEHEHP of 0.15 mol/L and R(A/O) of 2:1, and the extraction efficiency of RE(III) reached approximately 73.1%, which was higher than that in the hydrochloric acid and sulfuric acid systems. The mechanism associated with the extraction reaction was evaluated and discussed by the maximum loading capacity method, chromatographic analysis, and FT-IR spectrometric analysis. The mechanism followed a cation exchange reaction and acetic acid did not participate in the extraction process. The feasibility of the separation of Tb(III) from Eu(III) and Gd(III)was also given in terms of the separation coefficients between different elements at different extraction conditions. Since saponification is not necessary in the acetic acid extraction system, it can considerably reduce wastewater discharge to the ecological environment from the source.

中文翻译：

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使用 HEHEHP/正庚烷对乙酸溶液中的 RE（III）（RE = Eu、Gd 和 Tb）进行环保型非皂化溶剂萃取和分离工艺


实现可持续金属提取开发的关键是避免从源头上产生高盐废水。在这里，研究了一种使用 HEHEHP（2-乙基己基氢-2-乙基己基膦酸盐）从乙酸溶液中提取和分离镧系元素 Eu（III）、Gd（III） 和 Tb（III） 的新系统。考虑了接触时间、HEHEHP 浓度、初始溶液中稀土金属离子和乙酸浓度、水/有机相体积比 （R（A/O）） 和温度等相应参数，以优化不同稀土元素的分离条件。结果表明，乙酸体系中Tb（III）/Gd（III）和Gd（III）/Eu（III）的分离系数分别约为6.2和1.7，HEHEHP为0.15 mol/L，R（A/O）为2：1，RE（III）的提取效率达到约73.1%，高于盐酸和硫酸体系。通过最大负载能力法、色谱分析和 FT-IR 光谱分析评价和讨论与萃取反应相关的机制。该机制遵循阳离子交换反应，乙酸不参与提取过程。还根据不同萃取条件下不同元素之间的分离系数，给出了 Tb（III） 与 Eu（III） 和 Gd（III） 分离的可行性。由于醋酸萃取系统中不需要皂化，因此它可以大大减少废水从源头排放到生态环境。