Recent trends in metals extraction

After near 70 years of practical usage, solvent extraction is a perfectly mastered technique of separation, widely used on an industrial scale for the separation of metals mainly from raw materials. However, currently, in the era of depleting natural resources and increasingly less accessible deposits, environmental restrictions, etc., an increasing interest, both from social and economical constrains, is being directed at the extraction of metals from the secondary sources (such as batteries, electronic scrap). In many cases, solvent extraction, due to its operational characteristics, can be considered as the Best Available Technology for the purpose of separating multielemental metal solutions. This paper provides a brief overview of past achievements and present scenario of solvent extraction investigations and developments, describing some recently commissioned solvent extraction plants, whereas the Skorpion Zinc plant (Namibia) for zinc extraction from raw materials and caesium removal from radioactive High Level Wastes (HLWs) are told over in detail as case studies. The paper also presents some proposals for the use of liquid-liquid extraction to separate metal ions from secondary sources (e.g. cobalt from industrial waste streams). The review highlights the emerging use of ionic liquids as new extractants for metals, providing an insight into this exciting research field. Despite its detractors, solvent extraction has entered in force into XXI century as a leading separation technology for metals.Peer Reviewe

Treatment of spent pickling baths coming from hot dip galvanizing by means of an electrochemical membrane reactor

The performance of a one (OCR) and a two-compartment electrochemical reactor in the presence of a cation-exchange membrane (CEM) for the zinc recovery present in the spent pickling baths is analyzed in this paper under galvanostatic control. These solutions, which mainly contain ZnCl2 and FeCl2 in aqueous HCl media, come from the hot dip galvanizing industry. The effect of the applied current, the dilution factor of the baths and the presence or absence of initial cathodic zinc is also studied. For the 1:50 diluted spent bath, OCR experiments initially present higher values of the figures of merit than those obtained in the presence of the CEM since zinc is close to the cathode from the first electrolysis instants. However, at long electrolysis times, OCR presents zinc redissolution for all the current values tested due to the chlorine and iron presence close to the zinc deposits. In addition, the iron codeposition phenomenon is also observed in the OCR experiments when pH values are close to 2. On the other hand, CEM experiments become very similar to the OCR experiments at long time values since the CEM under these experimental conditions prevents zinc redissolution phenomenon and also iron codeposition. When the 1:50 diluted bath is concentred to 1:10, OCR experiments present the same tendency as that observed for the 1:50 dilution factor but the effect of zinc redissolution is increased due to the greater amount of chlorine generated in the anode. Under these experimental conditions, iron deposition has also been observed in the presence of the cation-exchange membrane as the rate of zinc deposition is greater than that of zinc transport through the membrane, and the zinc/iron ratio in the cathodic compartment is not high enough to prevent iron codeposition. In both cases, the pH values when iron codeposits with zinc are close to 2 and the zinc/iron ratio is below 0.6. The presence of initial zinc in the cathodic compartment of the electrochemical reactor enhances the reactor performance since it allows the zinc–iron separation in one single step and avoids the zinc redissolution phenomenon.The authors want to express their gratitude to the Generalitat Valenciana for a postgraduate grant (GV/2010/029) and to the Ministerio de Economia y Competitividad for financing the project number CTQ2012-37450-C02-01/PPQ.Carrillo Abad, J.; García Gabaldón, M.; Pérez Herranz, V. (2014). Treatment of spent pickling baths coming from hot dip galvanizing by means of an electrochemical membrane reactor. Desalination. 343:38-47. https://doi.org/10.1016/j.desal.2013.11.040S384734

Removal of phenols from aqueous solutions with solvating extractants

The removal of selected phenols (phenol, 4-methoxyphenol, 4-fluorophenol, 4-nitrophenol, 4-methylphenol, 4-chlorophenol, 2,4-dichlorophenol) from aqueous streams by liquid-liquid extraction is studied. Butylene and propylene carbonate – are used as green extractants. They permit to remove almost 100% of the examined phenols from feed solutions of phenol concentration about 20 g/dm3. Additionally, stripping of phenols from loaded organic phases is carried out with NaOH. The results of extraction parameters for alkylene carbonates (extraction efficency and distribution ratio) are compared with commercial solvating extractant – Cyanex 923

Methods of regeneration of spent pickling solutions from steel treatment plants

Facing the still growing demand for metals, particularly for zinc, the recovery of metals from secondary sources should be considered. Spent pickling solutions can be the source of valuable products such as hydrochloric acid, zinc or iron salts or even metallic zinc. The selection of an efficient, selective and economical method for the regeneration of such solutions is a key issue for hot dip galvanizing plants, especially in reference to strict environmental protection regulations

Application of quaternary phosphonium salts as extractants of Ru(III) and Rh(III) from model aqueous solutions

Przedstawiono badania ekstrakcji rodu(III) i rutenu(III) z modelowych chlorkowych roztworów wodnych za pomocą czterech czwartorzędowych soli fosfoniowych, mających taki sam kation triheksylo(tetradecylo)fosfoniowy i różne aniony: chlorkowy (Cyphos IL 101), bromkowy (Cyphos IL 102), bis( 2,4,4-trimetylopentylo)fosfinianowy (Cyphos IL 104) oraz bis(trifluorometylosulfonylo)imidkowy (Cyphos IL 109) rozpuszczonych w toluenie. Badano wpływ czasu wytrząsania obu faz, stężenia HCl, a także stężenia cieczy jonowej (IL) na ekstrakcję jonów Ru(III) i Rh(III).Rhodium(III) and ruthenium(III) were extracted from model chloride solutions with four quaternary phosphonium salts with the same cation trihexyl(tetradecyl)phosphonium and various anions: chloride (Cyphos IL 101), bromide (Cyphos IL 102), bis( 2,4,4-trimethylpentyl)phosphinate (Cyphos IL 104) and bis(trifluoromethylsulfonyl) imide (Cyphos IL 109) dissolved in toluene. The effect of shaking time of both phases, HCl concentration and IL concentration on Ru(III) and Rh(III) extraction were studied

Methods of regeneration of spent pickling solutions from steel treatment plants

Facing the still growing demand for metals, particularly for zinc, the recovery of metals from secondary sources should be considered. Spent pickling solutions can be the source of valuable products such as hydrochloric acid, zinc or iron salts or even metallic zinc. The selection of an efficient, selective and economical method for the regeneration of such solutions is a key issue for hot dip galvanizing plants, especially in reference to strict environmental protection regulations

Extraction of palladium (II) ions from chloride solutions with phosphonium ionic liquid CyphosŽIL101

The extraction of palladium(II) from hydrochloric acid solutions of various concentrations in the presence of different amounts of sodium chloride with phosphonium ionic liquid CyphosŽIL101 in toluene was investigated. The extraction of Pd(II) is very effective. The percentage extraction of Pd(II) from 0.1 mol dm-3 HCl solution amounts to 97% with CyphosŽIL101. Both the increase in HCl concentration and the presence of NaCl have a negative influence on the extraction. The extent of extraction from 0.1 mol dm-3 HCl solution in the presence of 0.5 mol dm-3 NaCl is about 80% and from 3 mol dm-3 HCl is lower and amounts to 56%. The extraction of Pd(II) from aqueous 0.1 mol dm-3 HCl and from 0.1 mol dm-3 HCl in the presence of 0.5 mol dm-3 NaCl with this phosphonium ionic liquid is rapid and the equilibrium is achieved after 1 - 2 minutes. The extraction of Pd(II) from aqueous 3 mol dm -3 HCl is slower and the equilibrium is achieved after 5 - 6 minutes

Hydrometallurgical treatment of hazardous copper Cottrell dusts to recover copper

Copper flue dusts, or copper Cottrell dusts, from three types of copper smelting furnaces were leached with different ammonia-based reagents (ammonium chloride, ammonium carbonate and aqueous ammonia solutions) to dissolve the oxidised copper species via the formation of copper-ammonia complexes, so that most of the copper-accompanying metals, especially iron, remained in the solid residue. Such copper-bearing dusts are not only valuable secondary source of copper but also are considered as hazardous materials and cannot be dumped as such. Therefore, two procedures for copper dust treatment are proposed, one of them includes ammonium-based leaching, liquid-liquid extraction with LIX 860 (aldoxime), LIX 84 (ketoxime) or LIX 54 (β-diketone) and electrowinning to grade A copper cathode. The other one covers also ammonium-based leaching followed by cementation with zinc to copper cement as a final product.Agencia CSIC (Spain) for support is acknowledged.Peer Reviewe