The reactivity of new ligands described as S-1, S-5, S2O9 (in respect to character and amount of donors) towards metal ions was examined by extraction from HNO3 and HCl media. These ligands were next utilised as carriers for Ag and Pd transport through a supported liquid membrane (SLM). The effect of collecting a greater number of S donors in one molecule and the influence of type of donors (O-S versus S) on efficiency and selectivity of Ag and Pd(II) extraction and transport were examined.The extraction of Ag from HNO3 solutions increased with increasing amount of S-donors in one molecule (S-1 < S2O9 < S-5). For palladium the sequence was different (S-5 < S-1 < S2O9). The transport of Ag through SLM impregnated with m-chlorotoluene solution of ionophore increased in the same order as in the case of extraction, whereas for Pd the row was different: S-5 < S2O9 < S-1. The highest fluxes of Ag and Pd transported from HNO3 equalled to 5.25 x 10(-7) and 1.37 x 10(-7) mol/m(2) s, respectively. Palladium flux depended on stripping solution type (Na2S2O3 < NaSCN). Very high selectivity of Ag and Pd extraction and Pd transport over Cu(II), Pb, Cd, Zn, Ni ions was achieved. The value of separation factor in Pd transport ranged from 30 to 19,000. (C) 2002 Elsevier Science B.V. All rights reserved.

The polydentate neutral sulphide podand 1,12-di-2-thienyl-2,5,8,11-tetrathiadodecane, (TTD), C4H3S-(CH2-S-CH2)4-C4H3S, which shows high affinity towards “soft metal ions” has been used as a carrier for gold transport through a supported liquid membrane (SLM). Transport of gold (5 × 10−5M) from hydrochloric acid solution to the stripping solution was facilitated by TTD in m-chlorotoluene(MCT)/kerosene solution immobilized in the pores of a polyvinylidene fluoride Millipore membrane. A study of the influence of different chemical and physical parameters on Au transport has been carried out. This includes the presence of kerosene in TTD-MCT solutions, the concentration of the carrier in the liquid membrane, the concentration of the stripping agent NaI (or NaSCN) and the stirring rate of both aqueous solutions. The highest value obtained for the permeability coefficient P was 0.34 cm min−1, and for the Au flux 1.5 × 10−6 mol m−2s−1. A high selectivity in the separation of Au from its bi-cation mixtures with an excess of Zn, Cu(II), Fe(III), or Cd was achieved.

The transport of gold ions (5×10-5 M) from a diluted hydrochloric acid solution to a stripping solution across a supported liquid membrane (SLM) containing 0.1 M solution of polydentate neutral sulfide podand l,12-di-2-thienyl-2,5,8,ll-tetrathiadodecane (TTD) in m-chlorotoluene was studied. The rate of transport of gold ions increased in the sequence of the stripping solutions, NaBr ≪ NH3, thiourea<NaSCN<NaK<thiosulfate. Among three microporous polymers used, the rate with Celgard 2500 membrane is ca. 23% higher than for Celgard 4510 or 2502. The present result shows that the selectivity for gold ion is good against copper, zinc and iron ions present in 200:1 excess. The gold flux (J) increases almost linearly with an increase in the initial gold concentration over the range 10-5 - 10-4 M; for 5×10-5 M Au it is equal to 10.3×10-8 mol cm-2 h-1.

A reaction scheme, developed at the Ames Laboratory, for the determination of the sulfur forms in coal takes advantage of the selective oxidizing power of perchloric acid. Sulfate, pyritic and organic sulfur are removed sequentially from a single sample of coal by solutions of perchloric acid boiling at 120, 155 and 205 °C, respectively, and converted to sulfate for subsequent turbidimetric measurement. Work in this paper focused on improving the selectivity by trying to remove pyrite at lower temperatures and improving the low sulfur recoveries observed for some coals. The results indicated that pyritic sulfur can be removed at lower temperatures and that possibly two different forms of organic sulfur can be delineated. After several potential explanations for the low sulfur recoveries had been explored, a standard additions technique, when applied to the turbidimetric measurement of sulfate, alleviated the problem of low sulfur recoveries.

The transport of silver through a supported liquid membrane saturated with a polydentate neutral ionophore 1,12-di-thienyl-2,5,8,11-tetrathiadodecane in m-chlorotoluene has been studied. Thiosulphate was used as the stripping solution. The influence of the feed solution composition, the type of a microporous polypropylene Celgard support, the ratio of feed/receiving solution volume, and the initial Ag concentration on the rate of transport of silver was examined. Transport of Ag is selective towards Cu(II), Pb and Zn, but these cations affected the rate of the Ag flux.

The extraction properties of the sulphide podand 1,12-di-2-thienyl-2,5,8,11-tetrathiadodecane (TTD), an open-chain neutral polythioether with six sulphur donor atoms in 1,2-dichloroethane, chloroform and MIBK for Pd and Au in hydrochloric, nitric and perchloric acid media have been examined. The kinetic aspects of the extraction of palladium(II) from hydrochloric acid by TTD and dioctyl sulphide (DOS) were compared. The rate of Pd extraction with TTD is considerably higher than that with DOS, especially with chloroform. Combined use of a reducing agent and TTD enhances the extraction of gold(III) into 1,2-dichloroethane.

A method has been developed for the determination of silver in copper ores and tailings by AAS based on the solvent extraction of silver with 1,12-di-2-thienyl-2,5,8,11-tetrathiadodecane, an acyclic neutral ligand with six sulphur donor atoms (sulphide podand), in IBMK. The separation was carried out on samples dissolved in 2 M nitric acid in the presence of boric acid. The accuracy of the method was examined using standard reference materials [a copper-zinc ore and a copper (pyrite) ore]. An r.s.d. of 2.8–4.9% for 10–4–10–3% silver in ores was obtained.

An extraction-AAS method of determination of Co, Ni, and Mn in metallurgical copper materials containing considerable amounts ofCu, Fe, Pb, Zn, and Al has been developed. Good selectivity of group separation of Co, Ni, and Mn has been achieved by (a) the use of tetrabutylammonium bromide to improve extractability of HTTA complexes by ion-pair formation, and (b) the masking of major elements with sodium thiosulphate and sulphosalicylic acid. The extracts are stable for at least 3 weeks.

The sulfide podand (an open-chain neutral mutlidentate ligand with six sulfur donor atoms) 1,12-di-2-thienyl-2,5,8,11-tetrathiadodecane (TTD) was synthesized. Its extracting properties were examined with 1,2-dichloroethane and 4-methylpentan-2-one as solvents. The reagent showed high selectivity for silver(I) and copper(I) ions; mercury(II) was extracted (ca. 97%) under certain conditions. Extraction of silver(I) was studied in detail with 110mAg tracer. Log D values ⩾2 were obtained for the range from pH 6 (with perchlorate as counter-ion) to 2 M perchloric acid or 6 M nitric acid. The ratio of Ag:TTD in the complex was 1:1. Silver could be back-extracted with 4–6 M hydrochloric acid.

A method has been developed for the AAS determination of Co, Ni, Mn and Cr in ores, concentrates and dusts of copper metallurgy at the 10−3–10−1% level. The matrix elements (Cu, Pb, Zn, Fe) were separated in a two-stage extraction: with MIBK from 6 M HCl solution and with 0.1 M tetrahexylammonium iodide (THAI) in MIBK from 3 M HCl, in form of ion-pairs, without Co, Ni, Mn and Cr losses. Values of r.s.d. were 2.0–6.0%.

The pyrolysis of samples containing copper, lead, iron, sulphur compounds and organic carbon is applied to separate mercury prior to its determination by a.a.s. Amalgamation on gold collectors followed by thermal desorption, or trapping in an absorption solution followed by reduction/aeration were used depending on the mercury content in the materials. Appropriate additives to the samples and filters are used to ensure complete release of mercury and removal of interfering pyrolysis products.

A method combining co-precipitation of traces of elemental Te on Se as carrier with organic solvent flotation is described. The best reduction and flotation conditions (hydrochloric and phosphinic acid concentrations, amount of Se, solvent used) were chosen. The recoveries for 100μg of Te(IV) (AAS measurement in MIBK) and 2μg of Te (radiochemical measurement with127Te) were 98% and 84–88%. The method was applied for separation of Te(IV) from copper metallurgy dust and slag.