草酸铵同步反萃-沉淀-皂化P507-钕负载有机相的研究

P507-Neodymium Loaded Organic Phase Synchronous Stripping-PrecipitationSaponification with Ammonium Oxalate

为简化稀土负载有机相反萃、沉淀和皂化工艺,降低化工材料消耗,首次采用草酸铵溶液反萃P507-钕负载有机相。实验结果表明,在草酸铵用量为理论量1.20倍,草酸铵溶液浓度45 g·L^(-1),反萃温度25℃、反萃时间15 min和有机相/水相(O/A)体积比1∶1时,有机相、水相和固相三相分相迅速,钕负载有机相单级反萃率为75%,有机相皂化值达0.53 mol·L^(-1)。采用4级逆流连续反萃,钕负载反萃率可高达99%以上,有机相皂化值为0.53~0.55 mol·L^(-1),皂化有机相中钕离子浓度小于0.002 mol·L^(-1),用该皂化有机相萃取钕离子,负载钕浓度达0.19 mol·L^(-1),钕离子与酸根离子(HA_(2))-基本符合1∶3的萃取规律,制备的氧化钕产品可达GB/T 5240-2015要求,残碳为0.035%。用草酸铵反萃负载有机相同步实现了负载有机相反萃、空白有机相皂化和稀土沉淀,使反萃、皂化和沉淀3个工序合并为一个工序完成,大大缩短了工艺流程。草酸铵一物三用,既是反萃剂,又是皂化剂和沉淀剂,使化工材料消耗降低了530元·t^(-1)-Nd_(2)O_(3),为简化稀土萃取分离提供了新的指导方向。

Rare earth elements play a very important role in modern high-tech industry and global supply and demand.The purification and extraction of rare earth mainly adopts P507-acid system,but the whole process consumes a large number of saponifier,stripping agent and precipitant,and blank organic saponification,loaded organic stripping,rare earth precipitation process are independent and discontinuous,these are common problems in the extraction process.To this end,scholars have solved these common problems by combining some steps,such as stripping rare earth loaded organic phase with oxalic acid solution to completing organic stripping and rare earth precipitation at the same time,but the blank organic phase still needs to be saponified to achieve recycling;the preparation of load organic phase directly dissolved by P507 organic phase realized rare earth dissolution and organic phase saponification synchronously,but faced with the problems of low loaded rare earth concentration and incomplete dissolution resulting in emulsification;P507-amine cooperative system could achieve non-saponification extraction,but affected by the stability of the extraction system,there were few examples used for rare earth production.During the extraction process,saponification is to maintain system pH balance and easy to extract rare earth;stripping is to exchange the rare earth in the load organic phase with H+,and precipitation is to generate rare earth deposits hardly soluble in water.In fact,the whole process is an exchange between rare earth ions and cation ions(cation ions in saponifier,acid and precipitates).In order to realize the single and versatility of cation in the exchange of rare earth ions,using the characteristics of neodymium oxalate with small solubility in water and insoluble in ammonium oxalate solution and organic phase,single stage and countercurrent continuous stripping experiments of P507-Nd loaded organic phase with ammonium oxalate solution in a constant temperature oscillator were carried out,which look forward to realizing the loaded organic phase stripping,rare earth precipitation and blank organic phase saponification simultaneously to shorten the process.The effects of ammonium oxalate dosage,reaction time,reaction temperature,ammonium oxalate concentration,organic phase/aqueous phase(O/A)volume ratio on Nd^(3+) stripping rate and organic phase saponification value were comprehensive investigated.Then,under the optimal conditions,the countercurrent continuous stripping was performed.The influence of stripping stage on Nd^(3+) stripping rate,organic phase saponification value,and Nd^(3+)concentration in saponified organic phase were studied,and using the obtained saponified organic phase to extraction Nd^(3+) to review the cyclic extraction effect.The results showed that when the amount of ammonium oxalate was 1.20 times of the theoretical amount,the concentration of ammonium oxalate solution was 45 g·L^(-1),the stripping temperature was 25 ℃,the stripping time was 15 min and the O/A volume ratio was 1∶1,the organic phase,aqueous phase and solid phase divided rapidly,the single stage stripping rate of Nd^(3+) loaded organic phase was 75%,and the saponification value of organic phase was 0.53 mol·L^(-1).The countercurrent continuous stripping results showed that the Nd^(3+) stripping rate and the saponification value increased and Nd^(3+) concentration in the saponified organic phase decreased gradually with the increase of stripping stages.When the stripping stages was increased to 4,the Nd^(3+) stripping rate and the saponification value of organic phase reached 99% and 0.53~0.55 mol·L^(-1),the Nd^(3+) concentration in saponified organic phase less than 0.002 mol·L^(-1).Using this saponified organic phase to extract neodymium chloride solution,the Nd^(3+) concentration in loading organic phase up to 0.19 mol·L^(-1),that was neodymium ion and the acid ion(HA2)-basically conformed to the extraction law of 1∶3.The neodymium oxalate from Stage 1 of countercurrent continuous stripping were filtered and washed with absolute ethyl alcohol to dissolve and remove floating oil,centrifugal separated and filtered,then washed with 50 ℃ pure water for 3 times,filtered and dried the precipitant at low temperature in muffle furnace,and then continuous calcinated at 850 ℃ for 2h to prepare neodymium oxide.The content of REO(the total rare earth content and was expressed as oxides)and Cl-in the obtained neodymium oxcarbon in neodymium oxide was 0.035%.All the results indicated that the P507-Nd load organic phase could be stripped directly with ammonium oxalate solution.During the reaction process,making full use of the oxalate anion stripping loaded organic phase and precipitation rare earth,using ammonium cation saponification the blank organic phase after stripping and realizing the cyclic extraction of rare earth,highlighted its singleness and versatility.Ammonium oxalate solution stripping process completed the loaded organic phase stripping,rare earth precipitation and blank organic phase saponification simultaneously,so that the three processes of stripping,saponification and precipitation were combined into one process,which greatly shortened the process flow.Ammonium oxalate was used for three purposes,not only a stripping agent,but also a saponifier and precipitant.Compared to the traditional process of P507-HCl system,the calculated chemical materials consumption of ammonium oxalate stripping process was reduced by 530 RMB/t-Nd_(2)O_(3).