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Extraction of metals in columns is scarce despite the advantage of low solvent inventory and the feasibility of high throughputs. Fast extraction kinetics allow short residence times and thus small apparatus height. A simulation of column concentration profiles via droplet population balances is less sophisticated as with surface active ion exchangers droplet breakage dominates and coalescence is hindered (rigid droplet surface). The extraction of Zn with D2EHPA (di(2-ethylhexyl)phosphoric acid) in a countercurrent Kühni column was investigated and the impact of different breakage kernels analyzed. Experiments in a lab scale test cell based on a DN32 Kühni extraction column geometry gave the basis to validate existing correlations and kernels for droplet breakage probability and daughter droplet size distribution. Since single droplet breakage tests were performed, a breakage dominated regime prevailed in the investigations. This yielded into a new unified correlation for the latter valid for different column geometries and physical and reactive extraction systems. As to this, a more firm basis for the simulation and design of stirred columns in hydrometallurgical application is established. [ABSTRACT FROM AUTHOR]

The influence of high-frequency AC fields on mass transfer from aqueous pendant and moving droplets into a continuous organic phase is investigated. Results are compared with those of applied DC voltage and those with no electric field present. Experiments are carried out in a low viscosity water–toluene system with acetone as the solute and in a high viscosity water–isotridecanol system with 1-propanol as the solute. AC and DC effects on Marangoni phenomena at pendant droplets are studied. High-frequency AC voltage is found to depress Marangoni phenomena whereas DC voltage enhances or initially induces Marangoni phenomena. Mass transfer from moving droplets could not be enhanced by the use of electric fields (AC or DC) at constant droplet size. The experimentally achieved concentration–time profiles are compared with those calculated from different mass transfer models for single droplets. [Copyright &y& Elsevier]

• Membrane-based microreactor is used for determination of chemical kinetics. • Kinetic models for cobalt and manganese are established considering back reaction. • Back reaction has even at low metal concentrations in the organic phase a strong influence on mass transfer. • Overall mass transfer from the aqueous to the organic phase could be modeled within a deviation of 5%. The separation of manganese from cobalt sulfate solutions is crucial in the field of spent lithium-ion battery recycling. A membrane-based microreactor is used to reveal required mass transfer characteristics as is diffusion and chemical reaction. The dependence of di-(2-ethylhexyl)phosphoric acid (D2EHPA) concentration, pH, and metal ion concentration on the extraction efficiency are investigated. A back-reaction term is introduced giving a significant influence on the effective extraction rate even at small metal complex concentrations as initial extraction rates proved to be inaccurate to describe the system. It is shown that the extraction of manganese at a pH of 3.0 is mainly diffusive while the cobalt extraction is strongly kinetically controlled. At a separating pH of 3.9 a good agreement between the model and experimental data is only given if the equilibrium back-extraction rate is considered (deviation less than 5%). [ABSTRACT FROM AUTHOR]

• Processing industrial leaching solutions from spent lithium-ion batteries. • Separation of manganese with saponified D2EHPA. • Influence of saponification degree on extraction yield and selectivity. • Equilibrium study for two extraction stages. • Overall extraction yield of manganese is 98.7%. Solvent extraction is used for the selective extraction of manganese from an industrial leaching solution based on active material from spent lithium-ion batteries. As solvent 100 g L−1 di-(2-ethylhexyl) phosphoric acid (D2EHPA) diluted in Isopar L and an addition of 5 vol% tributyl phosphate is used. D2EHPA is well studied for the separation of manganese from cobalt and nickel but no data can be found on the influence of saponification. The influence of the saponification degree on the extraction yield and selectivity is investigated for two extraction stages. An overall extraction yield of 98.7% is achieved. 40% saponified D2EHPA for the first and 20% for the second stage at a phase ratio of 2.33 shows the best performance in terms of extraction yield and selectivity. The saponification influences the pH shift during the extraction from initial 2.8 to 3.4. [Display omitted] [ABSTRACT FROM AUTHOR]

• Recycling of spent LiNi 0.33 Mn 0.33 Co 0.33 O 2 (NMC) active material from lithium ion batteries. • Continuous extraction of manganese from synthetic leaching solution with 100 g/L D2EHPA. • Correlations for Sauter mean diameter and holdup. • Mass transfer for cobalt, manganese and nickel in a disc and doughnut column. • Influence of feed pH value on selectivity and extraction yield. Solvent extraction of manganese was performed in a lab-scale DN50 pulsed disc and doughnut column. Optimal conditions for hydrodynamics and mass transfer were evaluated for the separation of manganese from cobalt and nickel with 100 g L-1 D2EHPA (di-(2-ethylhexyl) phosphoric acid) as a liquid ion exchanger. In performance tests with 0.01 mol L-1 MnSO 4 solution a maximum extraction yield of 94% was achieved at a phase ratio of 1.2 and a pulsation intensity of 3.2 cm s−1. Statistical analysis showed that the column loading (12 and 24 m h−1) had no significant influence on the extraction performance. The feed was a synthetic leaching solution likewise from active material of spent Li-NMC (nickel-manganese-cobalt) ion batteries. It consisted of an equimolar solution of 0.01 mol L-1 cobalt, manganese and nickel sulfate. Highest extraction yields of manganese 84% resulted at a feed pH of 2.7 or higher. At a pH of 2.2 the selectivity had its maximum at 40 and 22 for Mn to Ni and Mn to Co, respectively. A feed pH of 2.7 is recommended for optimum extraction performance and selectivity. [ABSTRACT FROM AUTHOR]

In industrial solvent extraction units, minimizing the energy input of liquid–liquid contactors is essential. Knowledge of the pressure drop evolution with both geometry and operating conditions is therefore required in order to achieve optimal sizing of the column. In this paper, yet unexplored parameters possibly affecting pressure drop in pulsed columns are investigated, namely the packing mounting clearance and the pulsation features. Their effect on pressure drop is addressed based on an experimental study, otherwise complemented by CFD simulations. The three possible types of flow (permanent flow, oscillating flow, and their combinations) have been actually investigated and compared, for both a disk and doughnut column (DDC) and a perforated plate column (PPC). Our experiments categorically confirm that the pressure drop along the column depends only on the mean fluid velocity, and is independent of the flow-type. This was moreover evidenced regardless of the pulsing device used (mechanical or pneumatical). Additionally, the influence of the mounting clearance required for the assembly of packing elements in industrial columns has been investigated and quantified for the first time. Thanks to an original DDC set-up, we measured the effect of a controlled non-zero gap between the rings and the wall on the pressure drop, hence completing the list and the analysis of parameters influencing the energy consumption in a pulsed column. [ABSTRACT FROM AUTHOR]