Witold A. Charewicz

Permeation of Chromium(VI) and Rhenium(VII) Oxyanions through Liquid Organic Membranes Facilitated by Quaternary Ammonium Chlorides

Abstract An experimental investigation is presented on the facilitated transport of Cr(VI) and Re(VII) oxyanions from aqueous solution into and through organic solutions of quaternary ammonium chlorides as mobile carriers of anions. Trimethyl tallow ammonium chloride (Aliquat 26), dimethyl dicoco ammonium chloride (Aliquat 221), and methyl tricapryl ammonium chloride (Aliquat 336) from General Mills Chemicals have been investigated. Effects of both anions and mobile carriers as well as the pH of feed aqueous solution and mixing rate on the course of metal permeation have been established. The hydrophobicity and nucleophilicity of a quaternary ammonium chloride were found to be the key factors influencing the transport of Cr(VI) and Re(VII) anions through bulk and emulsified liquid organic membranes. The permeation of perrhenates was much faster than that of chromates. Fast and effective separation was determined to be possible for rhenium from chromium in aqueous solution by means of facilitated transport...

The liquid surfactant membrane separation of copper, cobalt and nickel from multicomponent aqueous solutions

Abstract The separation of the cations of copper(II), cobalt(II) and nickel(II) from their mixed aqueous solutions, by liquid surfactant membranes containing di-(2-ethylhexyl)phosphoric acid (D2EHPA), lauric acid, caprylic acid, LIX-70 and Kelex-100 as ion exchangers and sorbitan monooleate as emulsifier has been studied. The effects of composition and acidity of the external feed solution on the separation of each metal are established. The multistage separation with fresh and reused liquid surfactant membrane was also applied to copper, cobalt and nickel mixed aqueous solution. D2EHPA liquid membranes appeared to be effective for nitrate and chloride systems, while Kelex 100 and LIX 70 membranes allow the separation of the metals studied, even from aqueous sulphate solutions. The process can be strongly competitive with liquid—liquid extraction, in particular in applications to the hydrometallurgical processing of low grade raw materials.

Separation of Cobalt by Liquid Surfactant Membranes

Abstract An experimental study is presented on the separation of cobalt(II) cations from an aqueous solution by means of liquid surfactant membranes containing the ion exchanger di(2-ethylhexyl)phosphoric acid. The process was studied at various emulsifier (Span 80) concentrations, membrane viscosities, pHs, and rates of stirring as well as at various KNO3 and cobalt concentrations. Cobalt recovery over 99% was achieved with up to tenfold enrichment. A substantial difference of the process course for cobalt and copper was found which allowed for their effective separation.

Selective Transport of Alkali Metal Cations in Solvent Extraction by Proton-Ionizable Dibenzocrown Ethers

Abstract Lipophilic crown ethers with pendant proton-ionizable groups are novel metal complexing agents for use in solvent extraction of alkali metal cations. A variety of dibenzocrown ether carboxylic acids and dibenzo crown phosphonic acid monoesters have been examined to probe the effect of structural variation within the complexing agent upon selectivity and efficiency in solvent extraction. Results from competitive solvent extractions of alkali metal cations from aqueous solutions into chloroform are summarized.

The oxidation of Fe(II) in aqueous sulphuric acid under oxygen pressure

Abstract An experimental investigation is presented on the oxidation of Fe(II) in aqueous sulphuric acid under oxygen pressure. The effects of partial oxygen pressure, pO2, temperature and initial concentrations of H2SO4 and Cu(II) on the oxidation process rate have been determined within the ranges applied in a new hydrometallurgical process for copper recovery from its sulphide concentrates [13–16]. The Fe(II) oxidation reaction rate was found to be described by a second-order kinetic equation at a ferrous iron concentration exceeding 3–8 g/l: d[Fe(III)] d t =− d[Fe(II)] d t =κ[ Fe(II)] 2 p O 2 exp − 56.9 RT

Foam Separation of Anions from Aqueous Solution: Selectivity of Cationic Surfactants

Abstract Anions are selectively separated and concentrated from dilute aqueous solution by foam fractionation. Selectivity coefficients are established from steady-state equilibrium data (solution concentrations 10−4 to 10−3 M) for SCN-, I-, ClO3-, NO3-, BrO3 −, and NO2 −, each vs Br−, with the quaternary ammonium surfactant modeled as a soluble anion exchanger. Studies are reviewed on the foam separation of Re(VII), Mo(VI), and V(V) oxyanions; Au(I), Ag(I), Ni(II), and Co(III) cyanide complexes; and Pt(IV), Pd(II), and Au(III) chloro complexes. In a five-component system, the oxyanions of Re(VII), Mo(VI), Cr(VI), W(VI), and V(V) are foam fractionated from 10−6 M solutions with the cationic surfactant, hexadecyldimethylbenzylammonium chloride. In the batch, time-dependent experiments, the metals are monitored by radiotracers and gamma radiation spectrometry. At pH 6.0 and a chloride (NaCl) concentration of 10−2 M, and at pH 2.0, adjusted with HCl, Re(VII) and Mo(VI) oxyanions can be separated completely f...

FLOTATION OF Co(II), Sr(II), and Cs(I) CATIONS WITH PROTON-IONIZABLE LARIAT ETHERS

An experimental investigation is presented on flotation of Co(II), Sr(II), and Cs(I) cations from very dilute aqueous solutions with proton-ionizable crown ethers: monoethyl sym-(butyl)dibenzo-16-crown-5-oxymethylphosphonic acid, sodium 3-[sym-(decyl) dibenzo-16-crown-5-oxy]propanesulfonate, and sym-(decyl) dibenzo-16-crown-5-oxyacetic acid, used separately or together with a nonionic foaming agent (Triton X-100). The effect of major process variables on both the efficiency and the rate of flotation of Sr(II) cations with sym-(decyl)dibenzo- 16-crown-5-oxyacetic acid and Triton X-100 were established. Moreover, the competitive Sr2+/Cs+ flotation was studied with sulfonic and carboxylic 16-crown-5 derivatives. The carboxylic collector exhibited strong affinity towards Sr(II) cations and up to 1000-fold molar excess of lithium, ammonium, and potassium chlorides, and nitrates did not stop flotation of Sr(II) cations. Such affinity allowed for complete separation of Sr2+ from Cs+ in a single-stage batch flotation. Selectivity of flotation of Sr(II), Cs(I), and Co(II) cations with the sulfonic and carboxylic collectors did not follow the “crown ether cavity size” selectivity rule. Nevertheless, the separation of Sr and/or both Sr with Cs from extremely dilute aqueous solutions with these collectors was efficient and fast, which might have a practical meaning for the decontamination of aqueous solutions containing radioactive isotopes. Proton-ionizable crown ether derivatives of sufficient surface activity and water solubility could make a new generation of specific collectors for flotation of aqueous ions.

Selectivity Coefficients for Zn(CN)4 2-, Cd(CN)4 2-, and Hg(CN)4 2- from Continuous Foam Fractionation with a Quaternary Ammonium Surfactant

Abstract An experimental study is presented on the continuous flow, foam fractionation of cyanide complex anions. Zn(CN)4 2-, Cd(CN)4 2-, and Hg(CN)4 2- form 7.5 × 10−6 to 1.5 × 10−5 M aqueous solutions with the quaternary ammonium surfactant, hexadecyltrimethylammonium iodide. The selectivity coefficients were determined for Zn(CN)4 2- vs I− equal to 8.86. for Cd(CN)4 2- vs I− equal to 21.79 and for Hg(CN)4 2- vs I− equal to 25.12. The surfactant ion-exchange reaction with the studied complex ions was also suggested.

Pressure leaching of a sulphide copper concentrate with simultaneous regeneration of the leaching agent

Abstract An experimental study is presented of leaching of a sulphide copper concentrate with aqueous ferric sulphate under oxygen pressure. The effects of oxygen pressure, sulphuric acid concentration and ferrous iron additions on the copper leaching rate have been determined. Partial pressure of oxygen has been found to govern the rate of copper leaching while the concentration of sulphuric acid only slightly influences this rate. Oxygen enhances the leaching rate mainly by oxidizing ferrous iron to ferric iron — the major leaching agent — and not by direct action on the minerals. Leaching of a sulphide copper concentrate under oxygen pressure with aqueous ferric sulphate leads to a three-fold reduction of both the necessary leaching time and ferric sulphate concentration in the leaching solution over those for conventional leaching with concentrated aqueous ferric sulphate.

Pressure reduction of copper(II) from highly acidic aqueous solutions containing arsenic

Abstract An experimental investigation is presented on pressure reduction with hydrogen of aqueous Cu(II) from highly acidic sulfate solutions containing arsenates in order to develop a process of recovering copper and arsenic from spent electrolytes in copper smelters. In particular, the effect of temperature, concentration of arsenic, concentration of sulfuric acid, and partial pressure of hydrogen on the course of pressure reduction of aqueous Cu(II) was examined. The following kinetic equation described this process: −(d[Cu(II)]/dt)=k[Cu(II)p0.5H2exp−(3100/RT). The reduction of copper and arsenic was studied from the actual spent electrolyte from Glogow II smelter. Principal parameters were determined for removing pure copper powder and arsenic from spent electrolyte using pressure reduction with hydrogen. Reduction of the electrolyte at temperature not exceeding 443 K gave pure copper powder with almost complete recovery. Then, the second reduction of remaining electrolyte with hydrogen at 473 K gave a solid arsenic product (Cu3As) with high recovery. The final electrolyte is suitable for re-use.