Separation of Iron,Cobalt, Nickel,and Cadmium in Aqueous Acid Halide Solution Using Aliquat-Foam Columns

Abstract

Polyurethane foam loaded with Aliquat 336 was prepared. The suitability of the prepared reagent foam for the separation of various relative concentrations of iron and cobalt in acidic aqueous solutions was confirmed using the static technique. The separation of other metal couples was achieved on the basis of similar ideas. Columns packed with the Aliquat foam were successfully used in the separation of iron or cadmium from cobalt and nickel. The foam column performance proved quite reasonable, and the application of relatively high flow rates (10 mL/min) was found to be possible.     

Selective Separation of Gallium from Acidic Leach Solutions by Emulsion Liquid Membranes

Abstract

The separation and concentration of gallium from acidic leach solutions, containing various other ions such as iron, cobalt, nickel, zinc, cadmium, lead, copper, and aluminium, by an emulsion liquid membrane (ELM) technique using tributyl phosphate (TBP) as carrier has been presented. Liquid membrane consists of a diluent, a surfactant (ECA 4360J), and an extractant (TBP), and 0.1 M HCl or 0.1 M H₂SO₄ were used as the stripping solution. The important variables governing the permeation of gallium and their effect on the separation process have been studied. These variables were membrane type and composition, mixing speed, diluent type, surfactant concentration, extractant concentration, HCl concentration in the feed, acid type of stripping phase, feed concentration, and treatment ratio. The optimum conditions were determined. It was possible to selectively extract 96.0% of gallium from the acidic leach solutions, containing Fe, Co, Ni, Zn, Cd, Pb, Cu, and Al, at the optimum conditions.     

Separation of Cobalt and Nickel with Phenylphosphonic Acid Mono-4-tert-octylphenyl Ester by Liquid Surfactant Membranes

Abstract

The separation of cobalt and nickel with liquid surfactant membranes (LSMs) was carried out in a stirred cell using a newly synthesized extractant. The effect of a surfactant on the kinetics of cobalt and nickel extraction was investigated to elucidate the role of a surfactant used in LSMs. The extraction equilibrium of these metals was also examined. Further, the interfacial tension between the organic and aqueous phases was measured to elucidate the adsorption equilibrium of a surfactant. It was found that the interfacial activity of the extractant is as high as that of a surfactant. In the extraction equilibrium study of these metals, extraction equilibrium constants were obtained for cobalt and nickel for the following equations:

Co²⁺ + 2(HR)₂=CoR₂(HR)₂ + 2H⁺ Ni²⁺ + 3(HR)₂=NiR₂2(HR)₂ + 2H⁺ The effects of the extractant and surfactant on the extraction rate of cobalt and nickel in LSMs were studied. The results were analyzed by a proposed model with an interfacial reaction, and rate constants were obtained for each metal. It was found that the new extractant has a very strong extractability for each metal compared with a conventional commercial extractant such as 2-ethylhexylphosphonic acid mono-2-elhylhexylester (commercial name, PC-88A) or di(2-ethylhexyl)phosphoric acid (D2EHPA). Further, a surfactant strongly affected the extraction rate and the separation of these metals, and a cationic surfactant was selected.     

A New Method for Recovering Fe(II) Sulfate,Copper, and Cobalt from Converter Slag

Abstract

The aim of this study was to recover copper and cobalt from the stock-piled converter slags at the Ergani Mining Co. in Turkey. Copper and cobalt are present in various chemical forms in the slag. For that reason, copper and cobalt were first converted to Cu₂S and CoS by passing H₂S gas through a slurry of ground slag in H₂SO₄ solutions. In the second stage, the slurry was filtered and it was determined that 30–40% of the iron and trace amounts of copper and cobalt passed into the solution as Fe²⁺, Cu²⁺, and Co²⁺ ions. The slag residue was then dried at 105°C for 2 h and roasted in a muffle furnace at about 600–700°C for different time periods. In the third stage, the mass obtained at the end of the roasting process was boiled with distilled water and filtered. The final solution was brought to volume and analyzed for copper and cobalt. It was determined that practically all of the Cu and 70.7% of the Co passed into the solution.     

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

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.     

Novel Electrochemical Hydrogen Separation Device Using Phosphoric Acid Membrane Cell

Abstract

State-of-the-art hydrogen separation technologies operate at/or near ambient temperatures and are not considered very effective with gases containing low concentrations of hydrogen (such as coal-gas) and are susceptible to common impurities such as H₂S, H₂O, and NH₃. Energy Research Corporation is developing an alternate, versatile process for hydrogen separation from any hydrogen-containing gas. This novel process involves oxidation of hydrogen at a gas diffusion anode to hydrogen ions, transportation of the ions under applied electrical field to a cathode, and reduction of the hydrogen ions at the cathode to hydrogen gas. The device offers many attractive features, including high hydrogen recovery (>90%), high product purity (>99%), tolerance to a variety of impurities, flexible product pressure, efficient operation with very dilute gases, negligible pressure loss, and wide operating pressure range including atmospheric. The feasibility of this electrochemical hydrogen separation device (EHSD) has been demonstrated at ERC using hydrogen concentrations as high as 75% (reformer product) and as low as 10% (process purge). The operating principle, design, and performance (current-potential relationship, product gas purity, effect of feed hydrogen concentration on hydrogen recovery and power requirements) of this process are presented in this paper.     

Solvent-Extraction Behavior of Cobalt(II), Nickel(II), Copper(II), and Palladium(II) with Tri-n-butylphosphate

Abstract

A systematic study of the extraction behavior of cobalt(II), nickel(II), copper(II), and palladium(II) with TBP from thiocyanate system in various ranges of acid concentrations has been performed. The thiocyanate medium leads to enhanced extractions in all these cases compared to those in the previously used chloride medium. For palladium, the chloride and nitrate systems have been critically examined. Sixty-two per cent extraction occurs from 4 M hydrochloric acid using 100% TBP in a single run and the extraction becomes quantitative (>99%) after four successive equilibrations. A simpler method has been proposed for rapid extraction of palladium(II) as the thiocyanate complex. Quantitative extraction occurs in the presence of 1.2% thiocyanate solution from 0.5 to 2 M hydrochloric acid (initial) up to pH 8.0. The extractable species of cobalt(II), nickel(II), copper(II), and palladium(II) from thiocyanate medium are probably similar and of the type [M(CNS)₄]^2? [K·TBP·3H₂O]₂ ⁺ (buffer solution) and [M(CNS)₄]^2? [H·TBP·3H₂O]⁺ ₂ (acid solution). A simple extraction scheme has been worked out for the separation of palladium(II) from iron(III), cobalt(II), nickel, manganese(II), copper(II), and platinum.     

As(V) Recovering‐Separation from Aqueous Systems by DAF Technique

Abstract

As(V) oxyanions removal from aqueous systems by dissolved air flotation (DAF) using Fe₂O₃ · xH₂O as solid support and sodium laurate as anionic surfactant was investigated. The influencing factors of the process: pH, support, surfactant, and As(V) concentrations, the presence of flocculant and foreign ions, conditioning time and dissolved air pressure were discussed, as they may affect in a great extent the separation efficiency. The systematic study aims to establish the optimum operating parameters of the process, to investigate the equilibrium and mechanism of separation.     

Reactivity of Metal Oxide Sorbents for Removal of Sulfur Compounds from Coal Gases at High Temperature and Pressure

Abstract

Hot-gas desulfurization for the integrated gasification combined cycle (IGCC) process has been investigated to effectively remove hydrogen sulfide with various metal oxide sorbents at high temperatures and pressures. Metal oxide sorbents such as zinc titanate oxide, zinc ferrite oxide, copper oxide, manganese oxide, and calcium oxide were found to be promising sorbents in comparison with other removal methods such as membrane separation and reactive membrane separation. The removal reaction of H₂S from coal gas mixtures with zinc titanate oxide sorbents was conducted in a batch reactor. The main objectives of this research are to formulate promising metal oxide sorbents for removal of hydrogen sulfide from coal gas mixtures, to compare reactivity of a formulated sorbent with a sorbent supplied by the Research Triangle Institute at high temperatures and pressures, and to determine effects of concentrations of moisture contained in coal gas mixtures, and to determine effects of concentrations of moisture contained in coal gas mixtures on equilibrium absorption of H₂S into metal oxide sorbents. Promising durable metal oxide sorbents with high-sulfur-absorbing capacity were formulated by mixing active metal oxide powders with inert metal oxide powders and calcining these powder mixtures.     

Solvent Extraction Separation of Chromium(VI), Iron(III), Cobalt(II), and Nickel(II) with Di-n-pentyl Sulfoxide

Abstract

Di-n-pentyl sulfoxide (DPSO) was employed for the solvent extraction separation of some transition metals from hydrochloric acid medium. It was found that chromium(VI) gets extracted at low acid concentrations (3 to 4.5 M), and iron(III) and cobalt(II) only above 5 M HCl. Nickel was not extracted at any of the test conditions. These transition metals were separated from one another by suitable choice of the extraction conditions.     

Improving SAPO-34 performance for CO2/CH4 separation and optimization of adsorption conditions using central composite design

ABSTRACT

SAPO-34 molecular sieves have a high adsorption capacity in separation of CO₂ from CO₂/CH₄ mixture. In this study, SAPO-34 was modified by different solutions at various operating conditions to enhance the removal of carbon dioxide from the methane gas. Modifications can change pore size and also Si/Al ratio in SAPO-34 and make changes in the acidity of the adsorbent via the ion exchange process. The effects of temperature and pressure on the separation were studied using the design of experiments. Finally, based on the results of the experimental optimization process applying central composite design (CCD) method, the highest yield of CO₂ separation from the methane gas (95%) was obtained when using P-SAPO-34 sample at 17.4°C and 4.6 bar.     

Thiosubstituted Organophosphorus Acids as Selective Extractants for Ag(I) from Acidic Thiourea Solutions

Abstract

This paper deals with the solvent extraction of silver from thiourea leaching Ag ore liquors as an alternative to the traditional process involving cyanide. The investigation of the extraction mechanism of silver from acidic thiourea solution had not been clearly established to date.

The extraction behavior of silver using di(2‐ethylhexyl)dithiophosphoric acid (D2EHDTPA) and di(2,4,4‐trimethylpentyl) thiophosphinic acid (CYANEX 302) was studied. The effect of various parameters such as concentrations of metal, mineral acid, thiourea, and extractant has been investigated. The extracted complexes have been identified through a slope method analysis as AgX(HX)₅ for CYANEX 302 and AgX for D2EHDTPA, where HX denotes the extractant. Moreover, complete stripping was ensured with a mixture of NH₄SCN and H₂SO₄. In addition we showed that a first step of extraction with D2EHPA or CYANEX 272 results in the preferential separation of Fe(III) from the Ag(I) leach solution.     

Process for the Recovery of Cobalt and Nickel from Sulphate Leach Liquors with Saponified Cyanex 272 and D2EHPA

Abstract

In this paper, a process is reported for the recovery of cobalt and nickel from copper raffinate solutions using partially saponified Cyanex 272 and D2EHPA as the extractants. The aqueous feed contains 1.65 g/L cobalt and 16.42 g/L nickel. More than 99.9% cobalt separation was achieved with 0.13 M Cyanex 272 (60% neutralized with alkali) in two counter‐current stages at an aqueous to organic phase ratio of 1.1:1. Co‐extraction of nickel was 0.18% only. Stripping of cobalt from a loaded organic phase was carried out with synthetic spent electrolyte solution at an organic to aqueous phase ratio of 2.5 in two counter‐current stages to generate a pregnant electrolyte solution to produce cobalt metal by electrowinning. Similarly, optimum conditions for nickel extraction with 60% neutralized 1 M D2EHPA at O/A ratio of 1.4 in 2 two stages and stripping of metal with synthetic spent electrolyte at O/A ratio of 1.6 in two stages were standardized. Extraction and stripping efficiencies were >99% and the flowsheet of the process is demonstrated.     

Pervaporation Separation of Water/Ethanol Mixtures through Polycarbonate/Cobalt(III) Acetylacetonate Membranes

ABSTRACT

In the present work, cobalt(III) acetylacetonate [Co(acac)₃] was added to polycarbonate (PC) to improve its performance on pervaporation separation of water/ethanol mixtures. By adding 3 wt% of Co(acac)₃ the resulting PC/Co(acac)₃ complex membrane possessed a permeation rate similar to a pure polycarbonate membrane, but the separation factor (water/ethanol) was about three times higher. The stability of the complex membrane was tested, and it was found that, after being immersed in an aqueous ethanol solution for 72 hours, the complex membrane was still stable. In addition, the effects of the added amount of Co(acac)₃ and the feed composition on pervaporation performance are presented in this work, and the mechanism of the improvement in pervaporation performance is briefly discussed.     

Electrochemical and XPS investigations of cobalt in KOH solutions

The electrochemical behaviour of cobalt in KOH solutions of different concentrations was studied. The effects of applied potential, temperature and the presence of aggressive Cl^– ions were investigated. Different electrochemical methods such as open-circuit potential measurements, polarisation techniques and electrochemical impedance spectroscopy (EIS) were used. The electrochemical behaviour of cobalt in naturally aerated KOH solutions is characterized by three different regions according to the alkali concentration. Corrosion behaviour was observed at high concentrations (0.3–1.0 M); passivation at lower concentrations (0.01–0.05 M), and at intermediate concentrations (0.1–0.2 M) corrosion followed by passivation was recorded. The corrosion parameters (i _corr, E _corr, and R _corr) under various conditions were calculated. Equivalent-circuit models for the electrode–electrolyte interface under different conditions were proposed. The experimental impedance data were fitted to theoretical data according to the proposed models. The relevance of the proposed models to the corrosion–passivation phenomena occurring at the electrode–solution interface was discussed. The electrochemical experimental results and discussions were supported by surface analytical techniques.     

Cation Exchange Chromatographic Separation of Scandium from Other Elements on Dowex 50W-X8

Abstract

Cation exchange chromatographic studies of scandium on Dowex 50W-X8 are reported. Mineral acids and their salts were tested as eluants. Their efficiency was evaluated in terms of the elution constant and the bed distribution coefficient as H₂SO₄ > CH₃COONH₄ > NH₄Cl > NaCl > HNO₃ > HCl > NH₄NO₃.

Scandium was separated from alkali, alkaline earths, iron, zinc, cadmium, mercury, copper, indium, aluminum, vanadium, uranium, and bismuth by the process of selective elution. It was separated from titanium, zirconium, hafnium, and antimony by the process of selective sorption. Separation of cobalt, nickel, manganese, lead, and silver from scandium was accomplished with sodium chloride as an eluant. The separation from thorium was carried out by gradient elution with hydrochloric acid.     

COBALT–NICKEL SEPARATION: THE EXTRACTION OF COBALT(II) AND NICKEL(II) WITH BIS(2-ETHYLHEXYL) PHOSPHINIC ACID (PIA-8) IN TOLUENE

The extraction behaviour of cobalt(II) and nickel(II) from sulfate solutions with bis(2-ethylhexyl) phosphinic acid (PIA-8) in toluene has been studied. Quantitative extraction of Co(II) was observed at pH 5.0–5.9 while that of Ni(II) at pH 6.8–7.0 with 0.03 M PIA-8 in toluene. The difference in pH_0.5 for Co(II) and Ni(II) was 1.9. The stoichiometry of the extracted species were determined by slope analysis method. The extraction reaction proceeds by cation exchange mechanism and the extracted species were Co · R₂(HR)₂ and Ni · R₂ · 2(HR)₂. Temperature dependance of the extraction equilibrium constants were determined to estimate the apparent thermodynamic functions (ΔG, ΔS and ΔH). The method was used for separation of cobalt(II) and nickel(II). Cobalt(II) was separated from nickel even at 1:20 (Co:Ni) ratio. The separation of cobalt(II) from nickel(II) was favoured with the increase in temperature.     

Studies on the Adsorption of Traces of Zirconium on Manganese Dioxide from Acid Solutions

Abstract

The adsorption of zirconium on manganese dioxide from nitric and perchloric acid solutions has been investigated at different concentrations of electrolyte, adsorbent, and adsorbate. The effect of other cations and anions on adsorption has been studied. Fluoride, citrate, oxalate, molybdate, tartrate, carbonate, phosphate, Fe(III), Sr(II), Zn(II), Cr(III), and Mg(II) drastically reduce adsorption. Adsorption of other metal ions on the oxide has been measured under identical conditions. Based on these data, separation of zirconium from a number of elements, including cobalt, zinc, caesium, neodymium and lutetium, can be achieved. Zirconium adsorption follows Freundlich's equation C _Ads = AC ^1/n Bulk with the values of 1/n = 0.92 and A = 40 mmol/g. Thus manganese dioxide can be used for the separation and preconcentration of zirconium from dilute solutions.     

KINETICS OF ZINC REMOVAL FROM COBALT ELECTROLYTES BY ION EXCHANGE

ABSTRACT

The removal of trace zinc concentrations from the INCO (Port Colborne) cobalt advance electrolyte by solvent impregnated ion exchange was studied in column and batch tests. The resins OC 1026, SIR 272 and SIR 302 were compared in terms of zinc loading and selectivity.

The OC 1026 resin demonstrated superior zinc loading and selectivity characteristics, but retained significant amounts of cobalt. Cobalt loading was determined to be closely related to the electrolyte pHdrop across the column. Resin pre-treatment with the advance electrolyte at pH 3 acts to diminish the pH drop across the column, and hence reduced the cobalt retained. Results from batch tests were fitted to kinetic models to gain an insight into process mechanisms. It was found that pre-treatment enhanced the apparent diffusion coefficient inside the resin phase by nearly an order of magnitude, improved exchange kinetics by allowing a lower pH reduction during the loading process, and improved Co²⁺/Zn²⁺ exchange in a matrix of the cobalt complex. Breakthrough curve analysis was also undertaken to determine the rate determining steps in the column process.

Further work is needed in X-ray microprobe analysis of resin samples from various portions of the column after loading, to gain a better understanding of the column loading process. The use of zinc selective electrodes in batch tests could also be undertaken to obtain more accurate estimates of diffusion and mass transfer coefficients.     

Reverse Osmotic Separation of Sodium Chloride and Cobalt (II) Chloride through Membranes Prepared from Schiff Bases of Polyallylamine

Abstract

Crosslinked membranes from Schiff base derivatives of polyallylamine were prepared with 2-pyridinecarboxaldehyde (P) and with P followed by salicyl-aldehyde, and used for the reverse osmotic separation between sodium chloride (NaC1) and cobalt (II) chloride (CoCl₂). The membranes whose rejection (R) was high against CoCl₂ and low against NaCl at each single feed supply showed a reduced difference in R in the case of a mixed solute feed due to Donnan exclusion by fixed charges in the CoCl₂-complexed membrane. An approximate calculation of the complexed CoCl₂ revealed that a very small portion of Schiff base groups took part in the complexation. Composite membranes on a cellulosic sheet solved the problem of an extreme reduction of the membrane strength after complexation, enabling continuous and repeated use. Some transport parameters were determined. Since they indicated a semipermeable character for CoCl₂, multistage runs of a single membrane or low pressure runs of a more porous composite membrane were suggested for the effective separation of NaCl and CoCl₂.