A novel neutral-base coupling synergistic extraction system of Cyanex923 and primary amine N1923 for the recovery of cerium(IV) and fluorine from sulfuric acid medium

A clean process for the recovery of rare earth and transition metals from NiMH battery based on primary amine and lauric acid

A novel rare earth separation system composed of lauric acid (LA) and primary ammonium (RNH2) was studied. Compared with individual LA and RNH2, the mixed extraction system can significantly improve the extraction and separation ability of rare earth (RE). When LA and RNH2 are mixed in an equal molar ratio, the synergistic coefficient for extracting Nd(III) in the system reaches 136.85. Effective separation of Nd from Co and Ni can be achieved, with the separation coefficients of 1503 and 2762 for Nd/Co and Nd/Ni, respectively. The ion association mechanism of developed extraction system can avoid the generation of saponification wastewater. Thus, the negative impact of saponification wastewater on the economy and environment can be reduced. The extraction system is simple to be prepared and easy to be stripped, which helps to reduce acid and alkali consumption. Application of this extraction system can effectively realize the separation of RE elements La, Ce, Pr, Nd and transition metals Co, Ni, Mn in nickel-metal hydride (NiMH) battery. This paper provides a new strategy for the development of ionic liquid saponification technology without saponified wastewater.

Predictive capability evaluation and mechanism of Ce (III) extraction using solvent extraction with Cyanex 572

Owing to the high toxicity of cerium toward living organisms, it is necessary to remove cerium from aqueous solutions. In this regard, the extraction of cerium (Ce (III)) from nitrate media by Cyanex 572 under different operating conditions was examined in this study. The effect of contact time, pH, extractant concentration, and nitrate ion concentration were investigated to characterize the extraction behavior of cerium and based on these outcomes, an extraction mechanism was suggested. The analysis of infrared spectra of Cyanex 572 before and after the extraction of cerium indicated that cerium extraction was performed via a cation-exchange mechanism. Then, the predictive models based on intelligent techniques [artificial neural network (ANN) and hybrid neural-genetic algorithm (GA-ANN)] were developed to predict the cerium extraction efficiency. The GA-ANN model provided better predictions that resulted higher R² and lower MSE compared to ANN model for predicting the extraction efficiency of cerium by Cyanex 572. The interactive effects of each process variable on cerium extraction were also investigated systematically. pH was the most influential parameter on cerium extraction, followed by extractant concentration, nitrate ion concentration and contact time. Finally, the separation of cerium from other rare earth elements like La (III), Nd (III), Pr (III), and Y (III) was conducted and observed that the present system provides a better separation of cerium from rare heavy earth than light rare earths.

Study on Reduction Stripping Kinetics of Ce4+ Using a Constant Interfacial Area Cell with Laminar Flow

The reduction stripping kinetics of Ce4+ by HEH/EHP was studied by a constant interfacial area cell with laminar flow. The effects of stirring speed, temperature, specific interfacial area, Ce4+ concentration in the organic phase, free extractant concentration in the organic phase, HCl concentration, and H2O2 concentration on the stripping rate were investigated. The control mode and control steps of stripping process were judged. The kinetic equation of stripping was derived. The mechanism of stripping process was discussed. The results show that the stripping process is controlled by both diffusion and interfacial chemical reaction. The apparent activation energy Ea was calculated using Arrhenius’s formula. The kinetic equation of Ce4+ reduction stripping is R = k[Ce4+](o)1.08[HEH/EHP](o)−1.03[H+](a)0.99[H2O2](a)0.53, and the apparent rate constant k is 10−3.66 (mol−0.57·L0.57)/min.