Chu Yong Cheng

Purification of synthetic laterite leach solution by solvent extraction using D2EHPA

Abstract The world mineral industry is experiencing an unprecedented interest in nickel–cobalt extraction from laterite ores through acid pressure leach and SX-EW processes. The recovery of cobalt and nickel from the leach solution through direct solvent extraction is of great interest as this would result in significant capital and operating cost savings. In the direct solvent extraction approach, the separation of zinc, calcium, copper and, in particular, manganese from cobalt and nickel is highly important. A series of shakeout tests was undertaken to investigate the fundamentals of the separation of the above impurities from cobalt and nickel using di-2-ethylhexyl phosphoric acid (D2EHPA) in kerosene. D2EHPA pH-extraction isotherms from solutions each containing a single element showed that the extraction order for the seven elements of interest as a function of pH 50 was Zn 2+ >Ca 2+ >Mn 2+ >Cu 2+ >Co 2+ >Ni 2+ >Mg 2+ . This confirmed that manganese would be extracted from sulfate solution ahead of cobalt and nickel. Extraction isotherms from solutions containing Zn, Ca, Mn, Cu, Co, Ni and Mg showed that the separation of zinc and calcium from the other elements was not difficult and the separation of copper and manganese from cobalt and nickel was possible. The separation of manganese from cobalt and nickel by D2EHPA in kerosene was affected by temperature and pH. At pH 3.0, better separation of manganese from cobalt and nickel was achieved at room temperature (23°C). At pH 3.5, better separation of manganese from cobalt was achieved at room temperature (23°C). However, better separation of manganese from nickel could be obtained at elevated temperatures (40–60°C). The McCabe–Thiele diagram for the system showed that at pH 3.5 and 40°C, two theoretical extraction stages at A/O ratio 1:1 were needed to extract 99.9% manganese from the aqueous solution and to reduce the manganese concentration from 2.0 g/L to 3 ppm. Multiple stage extraction with fresh aqueous solution showed that cobalt and nickel were crowded out by zinc and manganese. Multiple stage extraction with fresh organic solution showed that manganese and copper in the aqueous solution were eliminated. Multiple stage scrubbing of the loaded organic solution with manganese solution indicated that after one stage of contact, only about 3 ppm cobalt and nickel were present in the organic solution.

Dephosphorisation of western australian iron ore by hydrometallurgical process

Abstract More than 80% of Western Australian iron ore contains an average of 0.15% phosphorus, and attracts a penalty due to its high level of phosphorus when it is exported. At the current rate of mining, identified premium grade iron ore with low phosphorus content ( In the current work, effective dephosphorisation of Western Australian iron has been demonstrated. Sulphuric acid was chosen as the leachant on the basis of its availability and low cost. The iron ore sample used in this study typically contained 0.126% phosphorus, was from the Pilbara region of Western Australia. After roasting at 1250°C lump ore P80 5.6 mm), pellet 1 (grinding to 100% −1.5 mm before pelletisation) and pellet 2 (grinding to 100% −0.15 mm before pelletisation) were leached in solutions with different sulphuric acid concentrations. After leaching for 5 hours at 60°C in 0.1 M sulphuric acid solution, 67.2%, 69.0% and 68.7% of the phosphorus was leached from the above three samples, respectively. The phosphorus content was reduced from 0.126% to 0.044%, 0.055% and 0.042% respectively. The dissolution of iron during leaching was negligible. The optimum sulphuric acid concentration was 0.1 M in terms of acid cost and iron loss. The acid consumption cost is as low as

Synergistic Solvent Extraction of Nickel and Cobalt: A Review of Recent Developments

A 0.47/tonne. reserved.

Manganese in copper solvent extraction and electrowinning

Abstract Synergistic solvent extraction of nickel and cobalt has been an important research subject since the 1960s. In recent years, several synergistic systems have been further developed for possible industrial application, including carboxylic acids/pyridinecarboxylates for the separation of nickel and calcium; carboxylic acids/α-hydroxyoxime systems for the separation of cobalt from manganese, magnesium, and calcium, and carboxylic acid/α-hydroxyoxime/organophosphate systems for the separation of nickel and cobalt from manganese, magnesium, and calcium. The separation of nickel and cobalt from iron and aluminum using synergistic systems has also been explored. Industrial application of synergistic solvent extraction systems is expected in the near future.

Separation of Cobalt and Zinc from Manganese, Magnesium, and Calcium using a Synergistic Solvent Extraction System Consisting of Versatic 10 and LIX 63

Abstract In the copper solvent extraction–electrowinning (SX–EW) process, Mn2+ entrained in the organic solution may be transferred to the loaded electrolyte. It will then be oxidised during copper EW. The high-oxidation state manganese formed may in turn return to the SX circuit. The presence of high-oxidation state manganese has been associated with deterioration in the phase separation characteristics of the organic and aqueous mixture, resulting in increased phase disengagement times and the formation of stable mixed phases and emulsions. In the current work, recycle of manganese from copper EW to SX was simulated on a laboratory scale in continuous trials to investigate the mechanism of organic degradation via recycle of manganese from EW. During copper EW trials, Mn2+ in the electrolyte was primarily oxidised to Mn3+, which was further oxidised to MnO4−. Solid MnO2 particles also formed. The existence of high-oxidation state manganese species was consistent with the high redox potential in the solution. Manganese species Mn2+, Mn3+ and MnO4− were identified by their characteristic visible spectra. No evidence was found for the existence of Mn4+ in solution. The Mn2+ and Mn3+ or MnO4− concentration and the amount of MnO2 solids in the solution were determined by a combination of chemical analysis and redox titration. During copper SX–EW trials, the high-oxidation state manganese species oxidised some organic components of the organic phase during stripping. This oxidation correlated with poor phase separation and the formation of stable emulsions in both extraction and stripping stages. In this study, most of the observed organic oxidation and consequent emulsion formation was associated with the presence of Mn3+ rather than MnO4−. A number of degradation products of the hydroxyoxime extractants were detected by a combination of gas chromatography (GC), high performance liquid chromatography (HPLC) and pre-concentration techniques. The observed deterioration in phase separation characteristics correlated with the presence of 5-nonyl salicylic acid and a further hydroxyoxime degradation product which eluted in the most polar of three column chromatography fractions used to separate the degraded organics. Degradation products which eluted in the less polar fractions, to which the undegraded hydroxyoxime extractants reported, were shown not to be contributing to the observed deterioration in phase separation characteristics. Further work is in progress to verify that these more polar species do in fact inhibit phase separation processes. If correct, analysis for species more polar than the extractant could be used as a tool for diagnosis of phase separation problems due to organic degradation in SX systems.

Kinetic Separation of Co from Ni, Mg, Mn, and Ca via Synergistic Solvent Extraction

Abstract The Boleo leach solution contains large amounts of manganese (45 g/L), magnesium (25 g/L) and small amounts of cobalt (0.2 g/L) and zinc (1 g/L) in sea water. Due to the high manganese concentration, it is very difficult to separate cobalt and zinc from manganese, magnesium, and calcium using conventional solvent-extraction processes, which has led to the development of a synergistic solvent extraction (SSX) system consisting of Versatic 10 and LIX®63. By adding 0.4 M LIX 63 to 0.5 M Versatic 10, large synergistic shifts were obtained for cobalt (max. ΔpH50 4.24) and zinc (max. ΔpH50 1.62). After a single contact at pH 4.5, the extraction of cobalt was almost complete and that of zinc 80%. The extraction of manganese was 1.55%, and almost no magnesium and calcium were extracted, indicating excellent separation of cobalt and good separation of zinc from manganese, magnesium, and calcium. The SSX system was further optimized to reduce the co-extraction of manganese with the synthetic Boleo demonstration plant solution. It was found that with 0.33 M Versatic 10 and 0.30 M LIX 63, the SSX system composition approached optimum. After a single contact at pH 5.5, the extractions of cobalt and zinc were 93% and 70%, respectively, while the manganese concentration in the loaded organic solution was only 0.28 g/L. The extraction and stripping kinetics of cobalt and zinc were rapid. The SSX system was tested in two integrated pilot-plant trials with excellent results. Baja Mining has planned to implement the SSX circuit in their future Boleo plant.

The Recovery of Zinc and Manganese from Synthetic Spent‐Battery Leach Solutions by Solvent Extraction

Abstract The combination of LIX 63 and Versatic 10 acts synergistically for the selective extraction of nickel and cobalt from impurities of manganese, magnesium, and calcium. Nickel extraction kinetics is, however, slow relative to cobalt. The present work exploited this difference to selectively remove Co (1.0 g/L) from a Ni-rich feed solution (20 g/L) containing aforementioned impurities to achieve a raffinate Ni:Co ratio > 667. Batch testing was used to assess the effect of various factors on selective metal extraction. The selective stripping of the resulting loaded organic was also assessed. The metal selectivity properties of the organic solution did not deteriorate over five cycles.

A study on the chemical stability of the Versatic 10-Acorga CLX50 synergistic system

Recycling zinc‐carbon spent batteries is receiving growing interest due to environmental concerns and also the large quantity involved. It would therefore be advantageous to develop a solvent‐extraction (SX) process for the recovery of zinc and manganese from spent zinc‐carbon battery leach solutions. Among the two systems considered, D2EHPA and Ionquest 801, the latter is a better choice in terms of metal separation and stripping. It was shown that two theoretical stages are needed for the extraction of iron and zinc with the system containing 30% (v/v) Ionquest 801 and 5% (v/v) TBP in Shellsol D70 at an A/O ratio of 1:1, pH 3.0, and 40°C. The extraction kinetics of iron and zinc were very fast, and their extractions reached 99% and 93% within one minute, respectively. Less than 1% of the manganese was extracted in two minutes. The stripping kinetics of zinc was very fast, with over 97% being stripped in 30 seconds. The selective stripping of zinc from iron could be achieved at pH 0.5. Iron cannot be stripped effectively with the stripping solution containing 40 g/L zinc and 170 g/L H2SO4. Thus, an organic bleed stream could be needed to strip the iron with 400 g/L sulphuric acid. A process flowsheet has been proposed for the recovery of zinc and manganese from spent zinc‐carbon battery leach solutions using the Ionquest 801/TBP system. The advantage of this process is that both pure zinc and manganese product solutions could be obtained.

Recovery of water and acid from leach solutions using direct contact membrane distillation

Abstract Synergistic solvent extraction (SX) utilises combinations of extractants and synergists to enhance the selectivity of the organic extraction system. It has previously been shown by work conducted at the AJ Parker CRC/CSIRO Minerals that the selectivity of Versatic 10 for nickel over calcium was substantially improved by adding the Avecia reagent Acorga CLX50 to the organic system as a synergist. However, the chemical stability of this reagent under conditions relevant to an operating circuit had not been established. This study aimed to assess the chemical stability of Acorga CLX50 in a Versatic 10/Acorga CLX50/Shellsol 2046 system under conditions used at the Bulong Nickel SX circuit. This was achieved by monitoring physical and compositional changes in the organic solution with time when tested under the following conditions: continuous batch mixing with synthetic strip solution over 12 weeks at 40 °C, continuous batch mixing with synthetic strip solution over 16 days at elevated temperature (60 °C), and continuous extraction-stripping operation using a mixer/settler with synthetic aqueous leach solution and spent nickel electrolyte from the Bulong plant over 16 days at 40 °C. Minor changes in physical properties associated with the addition of Acorga CLX50 to a mixture of Versatic 10/Shellsol 2046 were observed, namely a decrease in interfacial tension and an increase in primary and secondary phase disengagement times after both organic continuous and aqueous continuous mixing. Importantly, no adverse changes in the physical properties of any of the organic solutions from the three tested systems were noted as a function of extended mixing time and/or mixing temperature. Similarly, no loss of Acorga CLX50 or ongoing generation of degradation products associated with the presence of Acorga CLX50 was observed in any of the organic solutions from the three tested systems, by gas chromatography or high performance liquid chromatography. From these results it can be concluded that the Versatic 10/Acorga CLX50/Shellsol 2046 organic system is chemically stable under the conditions tested and the addition of Acorga CLX50 does not, directly or indirectly, lead to the generation of species that adversely affect phase separation.

Uranium Solvent Extraction and Separation From Vanadium in Alkaline Solutions

This paper describes for the first time the use of direct contact membrane distillation (DCMD) for acid and water recovery from a real leach solution generated by a hydrometallurgical plant. The leach solutions considered contained H2SO4 or HCl. In all tests the temperature of the feed solution was kept at 60 °C. The test work showed that fluxes were within the range of 18-33 kg/m(2)/h and 15-35 kg/m(2)/h for the H2SO4 and HCl systems, respectively. In the H2SO4 leach system, the final concentration of free acid in the sample solution increased on the concentrate side of the DCMD system from 1.04 M up to 4.60 M. The sulfate separation efficiency was over 99.9% and overall water recovery exceeded 80%. In the HCl leach system, HCl vapour passed through the membrane from the feed side to the permeate. The concentration of HCl captured in the permeate was about 1.10 M leaving behind only 0.41 M in the feed from the initial concentration of 2.13 M. In all the experiments, salt rejection was >99.9%. DCMD is clearly viable for high recovery of high quality water and concentrated H2SO4 from spent sulfuric acid leach solution where solvent extraction could then be applied to recover the sulfuric acid and metals. While HCl can be recovered for reuse using only DCMD.