Synergistic extraction and recovery of Cerium(IV) and Fluorin from sulfuric solutions with Cyanex 923 and di-2-ethylhexyl phosphoric acid

Synergistic extraction and recovery of Cerium(IV) (Ce(IV)) and Fluorin (F) from sulfuric solutions using mixture of Cyanex 923 and di-2-ethylhexyl phosphoric acid (D2EHPA) in n-heptane have been carried out. in order to investigate the synergistic extraction of Cyanex 923 + D2EHPA, extraction Ce(IV), F, Ce(III) and Ce-F mixture solution using D2EHPA or Cyanex 923 as extractant alone were studied firstly, and then Synergistic extraction of Ce(IV), F and Ce(IV)-F mixture solution with D2EHPA + Cyanex 923 were carried out. The largest synergistic coefficient of Ce(IV) is obtained at the mole fraction X-Cyanex (923) = 0.8. The synergistic enhancement coefficients (R-max) obtained for Ce(IV) are 23.12 in Ce(IV) solution, and in Ce-F mixed solution R-max for Ce(IV) and F are 2.24 and 3.25 respectively.

利用Cyanex 923和离子液体的复合材料分离钇及重稀土

提供了一种固定Cyanex 923的新方法-溶胶-凝胶法。在溶胶-凝胶过程中离子液体的加入增加了复合材料的比表面积和孔容,并在硅胶网络中为Cyanex 923提供了一个可以扩散的介质。包埋离子液体和Cyanex 923的有机-无机复合材料的制备过程不需要其他有机溶剂,绿色、环保。结果表明,该复合材料对Y(Ⅲ)和重稀土元素有较好的分离效果。经过4次萃取/反萃过程,该复合材料对Y(Ⅲ)去除率仍高于78%。表明材料性能稳定,可多次重复使用。

Thermodynamic behavior and applications of KMnO4 in cerium separation process using cyanex 923

In this work, studies were carried out on the extraction properties of Mn(II) and MnO4- in sulfuric acid medium using Cyanex 923. Effects of different variables on the extraction of Mn(II) and MnO4-, such as the concentrations of acid, the extractant, and the temperature, were investigated. Results indicated that Mn(II) was extracted weakly by Cyanex 923; however, MnO4- could be strongly extracted into the organic phase. The extraction mechanism of MnO4- was proposed, and the influence of MnO4- on the extraction of cerium was identified when KMnO4 as oxidizer added into the bastnasite sulfuric acid leaching liquor. As MnO4- was easier to be extracted into the organic phase than Ce(IV) and then lost its ability for oxidization, a new device was designed to realize sufficient oxidization of cerium from III to IV, and which has been applied to industrialization.

Determination of Hg(II) in waters by on-line preconcentration using Cyanex 923 as a sorbent - Cold vapor atomic absorption spectrometry

Using a solid phase extraction mini-column home-made from a neutral extractant Cyanex 923, inorganic Hg could be on-line preconcentrated and simultaneously separated from methyl mercury. The preconcentrated Hg (11) was then eluted with 10% HNO3 and subsequently reduced by NaBH4 to form Hg vapor before determination by cold vapor atomic absorption spectrometry (CVAAS). Optimal conditions for and interferences on the Hg preconcentration and measurement were at 1% HCl, for a 25 mL sample uptake volume and a 10 mL min(-1) sample loading rate. The detection limit was 0.2 ng L-1 and much lower than that of conventional method (around 15.8 ng L-1). The relative standard deviation (RSD) is 1.8% for measurements of 40 ng L-1 of Hg and the linear working curve is from 20 to 2000 ng L-1 (with a correlation coefficient of 0.9996). The method was applied in determination of inorganic Hg in city lake and deep well water (from Changchun, Jilin, China), and recovery test results for both samples were satisfactory.

Extraction and stripping of ytterbium (III) from H2SO4 medium by Cyanex 923

The extraction and stripping of ytterbium (III) from sulfuric acid medium using Cyanex 923 in heptane solution was investigated. The effects of extractant concentration, pH and sulfate ion as well as stripping agents, acidity and temperature on the extraction and stripping were studied. The equilibrium constants and thermodynamic parameters, such as Delta H (10.76 kJ(.)mol(-1)), Delta G (-79.26 kJ(.)mol(-1)) and Delta S (292.41 J(.)K(-1.)mol(-1)), were calculated. The extraction mechanism and the complex species extracted were determined by slope analysis and FrIR spectra. Furthermore, it was found that the extraction of Yb (III) from sulfuric acid medium by Cyanex 923 increased with pH, concentration of SO42-, HSO4-, and extractant concentration, and approximately a quantitative extraction of Yb (III) was achieved at an equilibrium pH near 3.0, and the extracted complex was YbSO4(HSO4)(.)2Cyanex923((o)).

Three-phase extraction study of Cyanex 923-n-heptane/H2SO4 system

Phase behavior of the extraction system, Cyanex 923-heptane/H2SO4-H2O has been studied. The third phase appeared at different aqueous H2SO4 concentration with varying initial Cyanex 923 concentration and temperature affects its appearance. Almost all of H2SO4 and H2O are extracted into the middle phase. The H2SO4 concentration in the third phase increases with the increasing aqueous acid concentration (C-H2SO4,C-b) while the water content first increases and then reaches a constant value at CH2SO4,(b) = 11.3 mol l(-1). In the region of C-H2SO4,C-b higher than 5.2 mol l(-1), the composition of the middle phase is only related to the equilibrium concentration of H2SO4 in the bottom phase. H2SO4 and H2O are transferred into the middle phase mainly by their coordination with Cyanex 923 when C-H2SO4,C-b is less than 11.3 mol l(-1). When C-H2SO4,C-b is higher than 11.3 mol l(-1), excess H2SO4 is solubilized into the polar layer of the aggregates. In the region considered, the extracted complex changes from C923.H2SO4 to C923 . H2SO4 . H2O and then to C923 . (H2SO4)(2) . H2O.

Three-phase extraction study of Cyanex 923-n-heptane/Ce4+-H2SO4 system

Phase behavior of the extraction system, Cyanex 923-heptane/Ce4+-H2SO4 has been studied and compared with Cyanex 923-heptane/H2SO4 System. Cerium(IV) is mainly extracted into the third phase, and its concentration in the third phase first increases with the increasing aqueous acid concentration, reaches maximum and then decreases. At higher acidity, cerium(IV) is hardly extracted in the third phase. The phase behavior and change of the contents of acid and water are similar to those in the acid system. The acid concentration increases with increase of the aqueous acid in the whole extraction region while the water content first decreases with it and then increases after the third phase formation. The third phase has a characteristic lamellar structure formed by the aggregates of Cyanex 923 (.) (H2SO4)(2) (.) H2O as those in the case of acid system. The third phase loaded Ce(IV) has been used to prepare ultrafine CeO2 powder conveniently by precipitation with oxalic acid, and powders with size mostly smaller than 100 nm can be obtained.

Kinetics of cerium(IV) extraction from H2SO4-HF medium with Cyanex 923

Studies of the extraction kinetics of cerium(IV) from H2SO4-HF solutions with Cyanex 923 in n-heptane have been carried out using a constant interfacial area cell with laminar flow. The experimental hydrodynamic conditions were chosen so that the contribution of diffusion to the measured rate of reaction was minimized. The data were analyzed in terms of pseudo-first order constants. The results were compared with those of the system without HF. It was concluded that the addition of HF reduces the activation energy for the forward rate from 46.2 to 36.5 U mol(-1) while it has an opposite effect on the activation energy for the reverse process(the activation energy increased from 23.3 to 90.8 U mol(-1)). Thus, HF can accelerate the rate of cerium(IV) extraction. At the same time, the extraction rate is controlled by a mixed chemical reaction-diffusion rather than by a chemical reaction alone. A rate equation has also been obtained.

Kinetic study of Ce4+ extraction with Cyanex 923

Ce4+ extraction rate from aqueous sulphate solutions by Cyanex923 in heptane was studied using a constant interfacial cell with laminar flow at 30 degreesC. The experimental hydrodynamic conditions were chosen and the contribution of diffusion to the measured rate of reaction was minimized. Cerium extraction rate was measured at different chemical composition by varying the concentrations of hydrogen ion, sulphate and Cyanex923. A cerium-Cyanex923(B) extractive is formed at the interface. The data were analyszed in terms of pseudo-first order constants and a reaction mechanism was developed.

Recovery of Ce(IV) and Th(IV) from rare earths(III) with Cyanex 923

Solvent extraction of Ce(IV), Th(IV) with Cyanex 923 in n-hexane from sulphuric acid medium was studied with the dependence of the extraction on acidity and temperature being investigated. The Ce(IV) and Th(IV) extraction mechanism was proposed by slope analysis and the IR spectra of purified Cyanex 923 saturated with Ce(IV) were employed to determine the composition of the Ce(IV) complex. The equilibrium constant and thermodynamic functions of Th(IV) extraction were calculated and the characteristics of the stripping of Ce(IV), Th(IV) from the loaded organic phase were studied. (C) 1998 Elsevier Science B.V. All rights reserved.

Solvent extraction of scandium(III) by Cyanex 923 and Cyanex 925

The extraction equilibria of Sc(III), Zr(IV), Ti(IV), Th(IV), Fe(III) and Lu(III) from sulphuric or hydrochloric acid media by Cyanex 923 (mixture of straight chain alkylated phosphine oxides) and Cyanex 925 (mixture of branched chain alkylated phosphine oxides) were studied at various aqueous acidities. The extractant Cyanex 923 demonstrated better scandium loading and selectivity for TI(IV). Fe(III) and Lu(III) than Cyanex 925. The effects of extractant concentration on the extractions of sulphuric acid and Sc(III) by Cyanex 923 were examined. The stoichiometries of the extraction reactions were postulated based on slope analysis. The experimental results indicate that Cyanex 923 can be employed to recover scandium directly from the hydrolytic mother solution arising from TiO2 production via the sulphate process. The parameters studied were scandium loading capacity, phase ratio, concentrations of Ti(IV) scrubbing and Sc(III) stripping agents. A new solvent extraction technology of scandium recovery was developed. The purity of the final Sc(III) product is above 95% with a yield > 94%. (C) 1998 Elsevier Science B.V.

Cyanex 923对稀土元素硝酸盐的萃取

研究了Ｃｙａｎｅｘ９２３在正庚烷溶液中对１５种稀土元素硝酸盐的卒取，计算了分离系数，得出了反应机理，考察了温度对萃取平衡的影响以及萃合物的红外光谱，发现Ｃｙａｎｅｘ９２３有可能应用于从轻稀土中分离镧以及从重稀土中分离钇。

Cyanex923萃取稀土热力学、动力学及界面现象的研究

本文研究了中性萃取剂三烷基氧化膦(Cyanex 923)从硫酸介质中萃取与反萃三价稀土Yb(III)的热力学和动力学机理，对该萃取剂的界面活性进行了深入的研究，并详细探讨了其从硫酸介质中萃取Ce(IV)时液/液界面的吸附参数及萃合物的聚集。此外，还考察了一种羧酸类萃取剂仲辛基苯氧基取代乙酸(CA-12)所组成的萃取有机相中W/O微乳液的热力学稳定性与结构参数。 1. 研究了Cyanex 923从硫酸介质中萃取与反萃Yb(III)的热力学。考察了一些影响萃取与反萃的条件，如：酸度、盐析剂、温度、反萃剂种类等，得出了萃取机理与热力学函数，为分离Yb(III)与其它稀土元素提供了有用的参数。 2. 研究了Cyanex 923 从硫酸体系中萃取Yb(III)的动力学，通过考察搅拌强度、比界面积、温度、反应物浓度等各种因素对萃取速率的影响，确定其对Yb(III) 的萃取动力学为扩散控制过程，反应主要在液/液界面进行，控制步骤为反应物种通过界面凝滞膜的界面扩散过程，并推导出了萃取速率经验式。 3. 考察了温度、离子强度、酸度、添加剂和不同稀释剂对萃取剂Cyanex 923在Cyanex 923-稀释剂/Na2SO4-H2SO4界面的界面活性的影响，得到了Cyanex 923在不同条件下的界面吸附参数，对萃取剂界面活性与萃取动力学的关系进行了讨论。 4.考察了Cyanex 923-正庚烷/Ce(IV)-H2SO4 萃取体系在液/液界面的吸附参数，重点研究了体系的界面活性物种、萃合物聚集造成的界面现象及其对溶剂萃取过程的影响，详细地研究了Ce(IV)和H2SO4的萃取对萃取体系一些物化性质的影响,观测到了萃取体系中反胶束的存在。 5. 研究了皂化CA-12—添加剂组成的萃取有机相中W/O微乳液的热力学稳定性，考察了皂化率、电解质本性与浓度、pH值、温度对体系最大加溶水量的的影响，并考查了不同添加剂与含水量时微乳液形成的热力学函数及结构参数。

氟碳铈矿分离过程中的氧化问题及工艺改进

针对Cyanex 923萃取分离铈、钍、稀土过程中Ce(IV)在萃取过程中被有机相中的还原性物质还原的问题，提出采用高锰酸钾氧化萃余水相中的Ce(III)。研究结果表明，在酸性条件下，高锰酸钾能有效的氧化水相中的Ce(III)，但在萃取过程中，高锰酸根会先于Ce（IV）被萃入到有机相中，从而失去氧化Ce(III)的能力，由此提出氧化过程必须无含Cyanex 923有机相存在并参与设计了一套油水分离氧化装置。经过高锰酸钾氧化后，萃余水相中铈可低于0.5g/L，铈收率达到98%。 针对攀西氟碳铈矿新流程中直接制备的纳米级氟化铈，考察了氟化铈的紫外吸收性能，发现其在254nm处有特征吸收峰，还考察了分散剂的极性强弱、分散物浓度、粒径、温度及表面包覆等因素对紫外吸收性能的影响；发现随着粒径的减小，紫外吸收峰发生明显的红移；经TiO2包覆后CeF3的紫外吸光域范围扩展。 研究了Cyanex 923与P204组成的双溶剂萃取体系及其单独体系萃取Ce(IV)、F及Ce(IV)-F混液的热力学性质，得出了协同萃取机理，获得了萃取平衡方程式以及协萃物的组成。研究发现混合体系对Ce(IV)及Ce(IV)-F混液中的Ce、F均有明显的协萃作用，这为该萃取体系应用于现实分离中提供了可靠的保证。 在上述工作的基础上，提出了Cyanex 923与P204组成的双溶剂萃取体系分离攀西氟碳铈矿的新清洁冶金流程。对影响这一流程的化学因素进行了系统研究，并给出了工艺运行参数。

稀土分离过程的平衡反应和动力学研究

本论文共分六章，论文首先综述了近年稀土溶剂萃取最新出现的一些萃取体系及萃取方法，然后用溶剂萃取法系统研究了新萃取剂 PT-2 萃取稀土(III)、Cyanex 923 和 Cyanex 925 萃取铈(IV)、钍和稀土(III)的性质，推导层流型恒界面池的理论基础并用恒界面池法研究 Cyanex 272、PT-2 萃取稀土动力学，用高效离心分配色层仪(HPCPC) PT-2、Cyanex 302 和 Cyanex 272-P507 混合体系分离稀土(III)的规律，本论文还在大量实验数据的基础上，提出从氟碳铈矿中提取稀土的具有创新性的绿色工艺流程。论文第一章综述了近年衡土溶剂萃取的研究成果，为探求优于应用于工业生产的萃取稀土(III)的 P507 体系以及萃取钇的环烷酸体系，人们合成大量的有机磷类、羧酸类、苯胲类萃取剂并研究了它们萃取稀土的性能，将现有的萃取剂进行优化组合得到许多稀土的协同萃取体系，还将结晶反萃、还原反萃等方法应用于稀土分离过程。第二章用两相滴定法在测定 PT-2 的 K_d、K_2 等基本常数基础上，研究了 PT-2 的正庚烷溶液在盐酸、硝酸介质中萃取 15 个稀土离子（除了 Pm 外）的分配规律及萃取机理，同硫酸体系、高氯酸体系萃取平衡进行了对比，得到一些在理论上和实际上很有价值的结果。首次发现高位阻的酸性膦酸类萃取剂 PT-2 萃取轻、重稀土(III)时存在不同的机理，在盐酸、硝酸和硫酸体系中， PT-2 萃取轻稀土(III)为阳离子交换机理， PT-2 萃取重稀土时，阳离子交换机理和溶剂缔合机理共存；高氯酸介质中，由于高氯酸根离子难以同稀土(III)形成络合物， PT-2 萃取稀土(III)的机理符合一般的酸性膦酸酯的萃取规律，为阳离子交换机理。第三章探求了多种纯化 Cyanex 923 和 Cyanex 925 的途径，得出了较为行之有效的纯化方法，系统地研究了 Cyanex 923 从硫酸和硝酸介质中萃取 Ce(IV)、Th、La 和 Gd的规律，确定了萃合物的组成，计算了 lgK、ΔG、ΔH、ΔS 等热力学常数。 Cyanex 923 对 Ce(IV)、 Th(IV)的萃取在高酸度时随酸度的增大而降低，而 Ce(IV)、 Th(IV)同时萃取时， Th(IV)的萃取受到 Ce(IV)的抑制。发现 Cyanex 923 是一种良好 Ce(IV)的萃取剂，可用于铈从稀土(III)、钍中的分离、富集，具有很好的应用前景。第四章在层流型恒界面池的传质过程理论研究基础上，研究了二 (2,4,4-三甲基戊基)膦酸(HBTMPP)、PT-2 萃取 Er(III)的动力学，测定了流体线性流速、有机相浓度、水相浓度和酸度、温度及界面面积等因素对萃取速率的影响，对萃取的控制模式作出判断，为 Cyanex 272、 PT-2 在稀土湿法冶金中的应用提供基础参数。推导出层流型恒界面池中扩散控制模式下的萃取过程善于传质量和扩散层厚度两个基本公式。PT-2 萃取 Er(III)的过程属于扩散控制模式，在不同参数（温度、线性流速、界面面积、两相组成等）条件下，以 ln[(1/β + 1)C_b~a/C_(b,0)~a - 1/β] 对时间 t 作图得到都为直线，这些参数的变化对萃取的控制模式没有影响。萃取速率随温度、线性流速、界面面积等的变化规律也表明，该萃取过程为一扩散控制模式。根据萃取速率随线性流速、界面面积和温度的影响推断 HBTMPP 萃取 Er(III)为扩散控制和化学反应共同作用的混合控制模式。利用稳态法推导出该萃取过程的初始速率方程，该速率方程能和实验结果较好吻合。第五章用 HPCPC 研究 PT-2、Cyanex 302 及 Cyanex 272-P507 体系分离重稀土元素，评估 HPCPC 的性能及萃取剂的萃取性能，考察了流动相的流速、 pH 及 HPCPC 的转速等对分离效率的影响，并对这些体系萃取重稀土(III)的机理进行了探讨。发现流速对 HPCPC 的分离效率有显著的影响，随流速的增大，理论板数降低，分离度减小；理论塔板数和分离度随转速的变化无明显的变化；在 D 值相同时， Vs/Vm 越小，理论塔板数 N 越大；pH 越高，D 越大，理论塔板数则越低；萃取剂的浓度越高，理论塔板数越低。用 HPCPC 梯度洗脱法在 Cyanex 302 体系中只经过一次运行可将轻、重稀土混合物 La(III)、Sm(III)、Dy(III)和 Tm(III)分离。第六章针对攀西稀土矿 冶炼工艺中存在由于稀土收率低、放射性钍未得到分离和利用、存在二个放射性废渣和放射性废水等问题，采用溶剂萃取法，从攀西矿氧化焙烧－硫酸浸出液中萃取分离钍和铈(IV)。研究了 N1923 从氟碳铈矿硫酸浸出液中萃取分离钍和铈(IV)的工艺，并在此基础上提出从攀西矿中萃取分离铈(IV)、钍和提取氯化稀土的流程 I。用 N1923 萃取铈(IV)、钍，稀硫酸为洗液，形成含四价铈及钍的有机相和含三价稀土元素的萃余液，实现铈、钍与三价稀土的萃取分离。由于用含过氧化氢的硫酸溶液反萃铈(IV)困难，用含过氧化氢的硝酸溶液反萃铈(IV)、钍，再以 Cyanex 923 萃取钍，实现钍和铈(III)的分离。还研究了用 S501 萃取萃取铈(IV)工艺，以稀硫酸为洗液，用含过氧化氢的硫酸溶液为反萃取液反萃铈(IV)。解决了萃取过程铈(IV)的还原性问题；探明了氟离子对萃取过程的影响以及在料液、洗液、反萃取液中加入硼酸的作用，在大量数据的基础上提出了工艺的各成分的组成。