Research On Complexation Ultrafiltration Process Of Rare Earth Leaching Solution

In recent years, the complexation ultrafiltration in metal ion separation and enrichment research is being widely researched.The complexation ultrafiltration used on separation of rare earth ions(RE3+), the advantages as follows: no use of precipitating agent, no secondary pollution; no acid soluble phase, reducing the amount of acid; the RE3+ enriched and so on. Taking rare earth leaching solution as research object, the issue investigated the factors that may affect the complexation ultrafiltration process of rare earth leaching solution, in order to provide theoretical basis on the application of complexation ultrafiltration technology in rare earth leaching solution separated areas separation and enrichment.Firstly, with anionic polyacrylamide APAM, sodium polyacrylate PAASS and polyethyleneimine PEI as complexing agents, the paper investigated the complexation ultrafiltration behavior between the complexing agents and the simulation rare earth leaching solution, discussing the pretreatment process of three complexing agents and the effect of p H, the applied load ratio L and Al3+ concentration on the behavior of complexation ultrafiltration. The results showed as follows:(1)After pretreatment, the retention rate of three complexing agents reached 100%;(2)Near neutral range was suitable for complexation reaction of PAASS and PEI;(3)The optimum load ratio L of PEI and PAASS for complexation reaction is L=0.75;(4) APAM is unsuitable as complexing agent of RE3+;(5)The concentration of Al3+ has a greater impact on rare earth leaching solution complexation reaction, the rare earth leaching solution must be purified before complexation reaction.In addition, based on the study of the simulation rare earth leaching solution complexation ultrafiltration behavior, the impurity removed rare earth leaching solution complexation ultrafiltration process was researched. The optimum hydrolysis impurity p H was 7.1.The effect of p H, L, ΔP and T on complexation ultrafiltration was investigated, also analyzing the enrichment and decomplexation experiment. The results show that:(1) The optimum complexation reaction conditions between PAASS and the rare earth leaching solution is pH=6-7, L=1.0;(2) The optimum ultrafiltration conditions between PAASS and the rare earth leaching solution isΔP=0.6Mpa, T=25-30℃;(3)The concentration of RE3+ can be improved through complexation ultrafiltration, after two hours decomplexation the permeate solution RE3+ concentration can reach to 1367mg/L, the dissociation rate was 71.2%.The mechanism analysis of complexation reaction between PAASS and RE3+ showed that PAASS combined with RE3+ mainly through COO- groups, the complex pattern was diverse; the reaction kinetics of complexation reaction can be described by a pseudo-first-order equation, the rate constant k1 of reaction is 0.0357; the complexation reaction belongs Langmuir adsorption, the experimental data fitting can obtain a linear equation, correlation coefficient R2= 0.997, Langmuir adsorption constant is 0.133.