Allan Ang

Laboratory bench scale experiments were performed to develop a process for electrodialysis (ED) of LiCl liquor from spodumene leaching and purification to produce LiOH solution, for subsequent conversion by evaporative crystallisation to LiOH·H2O crystals as the end-product. Nafion® 117 cation-selective membranes were used in all experiments. The small electrolytic test cell achieved an average LiOH production rate of 7.5g/h with 83% coulombic efficiency and specific electrical consumption of 6.5 kWh/kg LiOH. In the large electrolytic test cell, a higher average LiOH production rate of 11.2g/h was attained but at lower coulombic efficiency (62%) and greater specific electrical consumption (8.8 kWh/kg LiOH). In a longer period ED process, there was a further decrease in coulombic efficiency and an increase in the specific electrical consumption. Also, the cation-selective membranes were found susceptible to the deportment of cation and anion impurities (i.e., Na+, K+, and Cl-), which impacted the LiOH·H2O product purity. Higher purity LiOH·H2O was obtained from the LiOH liquor produced in the ED testwork by subjecting the liquor to partial evaporation under a nitrogen gas blanket. Further optimisation of the process parameters is expected to enhance the yield and purity of the LiOH·H2O product and reduce operating costs.

Lithium hydroxide (LiOH) is rapidly becoming the main precursor for layered oxide cathodes used in lithium ion batteries. Current hydrometallurgical method for LiOH production uses substantial amounts of chemicals and creates wastes, leaving behind a negative environmental footprint. Electrodialysis is emerging as a more sustainable technology for LiOH production, effectively eliminating the conventional chemical addition step and its subsequent waste management. Additionally, hydrogen is generated as a by-product during the electrodialysis process. Various configurations of the electrodialysis cell have been employed to maximize the energy efficiency of the process and the purity of the LiOH product. Nonetheless, this review found that there is a lack of concerted effort in developing ion exchange membranes specific for LiOH production. Current membrane technologies are not tailored to LiOH production, with limited selectivity to lithium in relative to other monovalent cations, as well as relying heavily on harmful perfluoroalkyl (PFA)-based polymeric membranes. In this review, special attention is given to the state of the art in the testing and development of membranes, i.e., cation and anion exchange membranes, bipolar membranes, as well as novel membranes that are potentially low-cost, non-fluorinated, lithium-selective with high chemical stability and mechanical robustness.

The project, part of a major collaboration between the Minerals Research Institute of Western Australia (MRIWA), Murdoch University and sponsors Lithium Australia and Venus Metals Corp, sought to develop new technology for battery grade lithium production. The project also aimed to capture valuable byproducts from the extraction of high-grade lithium carbonate from certain groupings of minerals, known as micas.

The project, part of a major collaboration between the Minerals Research Institute of Western Australia (MRIWA), Murdoch University and sponsors Lithium Australia and Venus Metals Corp, sought to develop new technology for battery grade lithium production. The project also aimed to capture valuable byproducts from the extraction of high-grade lithium carbonate from certain groupings of minerals, known as micas.

Chelating resins with different functional groups were evaluated for their potential application in separating uranium U(VI) and thorium Th(IV) from rare earth elements, RE(III). The candidate resins included a bis-picolylamine resin, aminophosphonic resins, iminodiacetic resins, and solvent-impregnated resins. The adsorption selectivity of these resins towards U(VI) and Th(IV) in the presence of selected RE(III) was examined in sulfuric acid media of varying concentrations. It was evident that the adsorption performance of the resins was acid concentration-dependent. Most candidate resins had potentially feasible selective adsorption at or below 0.1 mol/L H2SO4 (or pH ≥ 1). Depending on their functional groups, the chelating resins displayed varying selectivity towards U(VI), Th(IV) and RE(III). It was found that the iminodiacetic resins exhibited the highest affinity for U(VI) and Th(IV) over RE(III). At 0.005 mol/L H2SO4 (or pH 2), the adsorptions of U(VI) and Th(IV) were approximately 90% while adsorption of RE(III) was less than 20%. This can be explained by considering the coordination chemistry of the resins whereby molecular ligands with N- and O-donor atoms were demonstrated to adsorb both U(VI) and Th(IV) strongly. Comparing the different O-donor groups (i.e., sulfonyl, phosphoryl and carboxyl), the carboxyl group from the iminodiacetic resin gave the best separation of U(VI) and Th(IV) from RE(III). The performance of the solvent-impregnated resins has indicated the possibility of exploiting steric effects to obtain a highly selective chelating resin for U(VI) and Th(IV) over RE(III). In addition, the potential application of these resins in an integrated process for sequential 2-stage separation of U(VI) and Th(IV) from RE(III) in sulfuric acid media is also presented.

A method for the rapid measurement of current efficiency for the deposition of zinc by a computer controlled anodic stripping technique has been successfully developed and evaluated in the laboratory and in a zinc tankhouse. This method provides rapid measurement of the efficiency within about 3 min from 1 to 2 L of electrolyte at a fixed temperature. Minimum preparation time is involved as the pure lead wire cathode surface can be easily renewed by simply cutting the coated wire to expose a new surface. Reproducible results have been achieved which compare very favourably with those obtained by longer term conventional methods. It has been demonstrated that the technique can also prove to be useful as a convenient method for the study of cathode morphology and for the nature of the potential/time transients during nucleation and growth of zinc deposits under various conditions. Thus, the effects of the concentrations of various impurities such as selenium, antimony and cobalt on the current efficiency and the morphology of the zinc deposits have been studied. The effects of the addition of additives such as glue and gelatine have similarly been evaluated. The results have been shown to be consistent with published data.

Conventional ion exchange resins with different functional groups were evaluated for their potential application in separating uranium U(VI) and thorium Th(IV) from rare earth elements RE(III). The resins studied comprised strong- and weak-base anion exchange resins, and strong- and weak-acid cation exchange resins. The selectivity of these resins to adsorb U(VI) and Th(IV) in the presence of selected RE(III) was examined in sulfuric acid media of varying concentrations. It was evident that the adsorption performance of the resins was acid concentration-dependent. Most candidate resins had potentially feasible selective adsorption at or below 0.1 mol/L H2SO4 (pH ≥ 0.7). Within the group of anion exchange resins, both the strong- and weak-base resins exhibited a similar selectivity with U(VI) adsorbed in preference to RE(III). The difference between them was their adsorption of Th(IV). The weak-base resin with primary amine functional group demonstrated superior separation of Th(IV) from RE(III). For this resin, 78% of U(VI) and 68% of Th(IV) were adsorbed while RE(III) co-adsorption was < 5% at 0.0005 mol/L H2SO4 (pH 3). In the case of the strong-acid cation exchange resins, Th(IV) and RE(III) were adsorbed in preference to U(VI), i.e., RE(III) > Th(IV) >> U(VI). The weak-acid cation exchange resins, on the other hand, displayed limited adsorption of all elements.

The objective of this study was to investigate the applicability and performance of the selected ion exchangers with different physicochemical characteristics and functional groups to simultaneously recover three different platinum group elements (PGE), platinum(IV), palladium(II) and rhodium(III), present in a chloride solution produced by the leaching of spent automotive catalysts. The tested ion exchangers included a resin with a quaternary ammonium functional group (Lewatit MonoPlus (M +) MP 600), a resin with a polyamine functional group (Purolite S985) and a resin with a thiouronium functional group (XUS 43600.00). The study also focused on the achievable desorption from the loaded resins using different eluent systems. The leach solution was chlorine-saturated and contained 2.35 mol/L hydrochloric acid, platinum and palladium in concentrations of 0.13 mmol/L, and rhodium 0.03 mmol/L. It was found that XUS 43600.00 showed the best adsorption performance for platinum(IV) and palladium(II) chloride complexes among the investigated resins, but weak affinity for rhodium(III) chloride complexes was observed for all three resins. The adsorption kinetics were found to obey the Ho pseudo-second order expression. For Lewatit MonoPlus (M +) MP 600 and Purolite S985 the adsorption was best described by the Freundlich isotherm, while for XUS 43600.00 the Langmuir isotherm was more apt. Desorption of the PGE was examined using four different elution agents: sodium thiocyanate (2 mol/L), hydrochloric acid (2 mol/L), thiourea (1 mol/L) in hydrochloric acid (2 mol/L), and thiourea (1 mol/L) in sodium hydroxide (2 mol/L). The results showed that platinum and palladium can be fully eluted with the acidic thiourea but desorption of rhodium proved difficult with all the eluents.

Platinum-group metals (PGMs) have become one of the most sought after rare metals in this modern age of science and they will continue to increase in importance as a result of their advantageous use in clean-air technology. Due to the scarcity of these precious metals, the application of ion exchange processes to recover PGM ions from relatively uncontaminated aqueous solutions, such as produced by the leaching of secondary sources including used automotive catalytic converters and electronic scrap, is becoming an increasingly cost-effective option and hence an important topic for the PGM production industry. This paper provides a general overview of the basic principles and theories relevant to the hydrometallurgical recovery of PGMs using ion exchange resins, along with a review and discussion of the most important factors that affect the separation and purification of PGMs present initially in predominantly ionic state in an aqueous hydrochloric acid solution. It is shown that in these acidic chloride solutions, the current system of choice for the leaching of PGMs, the adsorption behavior of the PGM ions onto chelating ion exchange resins is strongly dependent on the anionic PGM chloro-complex species present. In addition, it is revealed that the main factors affecting this complexation are (i) acidity and chloride ion concentration of the contacting aqueous chloride solution, (ii) "ageing" of the solution, and (iii) temperature of the solution.