5 research outputs found
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Extractant effect on the retention of the stationary phase in a rotating coiled column
This is an open access article that be found at the links below - Copyright @ 2002 Springer VerlagThe effects of physicochemical properties of two-phase liquid systems (interfacial tension and differences in density and viscosity) on the retention of the stationary phase in the column were examined. These effects mainly determine the separation parameters of compounds. Extractant/decane–aqueous phase systems were used; their physicochemical properties changed both as a result of adding an extractant (di-(2-ethylhexyl) phosphoric acid, trioctylamine, or tributyl phosphate) to the organic solvent and because of a change in the composition of the aqueous phase. Aqueous ammonium sulfate of varying concentration was used as a mobile phase. It was shown that interfacial tension substantially affects the behavior of the systems under consideration. An increase in the ammonium sulfate concentration only slightly affects the retention factor of the stationary phase in the column. With a proper choice of the stationary phase, countercurrent chromatography can be used for the extraction of components from salt solutions of various concentrations
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The efficiency of substance separation in countercurrent liquid chromatography
This is an open access article that can be found from the links below - Copyright @ 2003 Springer VerlagThe effect of hydrodynamic parameters and the specific features of instrument design on the efficiency of substance separation in countercurrent liquid chromatography (CCC) was studied using a constant retention factor of the stationary phase in the column. The study was conducted with the separation of benzyl alcohol and p-cresol in a two-phase liquid system heptane–ethyl acetate–methanol–water (1.4 : 0.6 : 1 : 1) in as an example. It was shown that the peak resolution is improved with an increase in the rotational speed of the column and a decrease in the flow rate of the mobile phase. The best peak separation was attained using columns for which the ratio of the column rotation radius to the radius of column revolution was 0.615. It was shown that countercurrent chromatography allows the separation of substances with low partition constants (K < 1)="" in="" dilute="" solutions.="" the="" volume="" of="" the="" test="" sample="" may="" be="" up="" to="" 15%="" of="" the="" total="" volume="" of="" the="" chromatography=""
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Separation of substances in rotating coiled columns: From trace elements to microparticles
This is an open access article that can be found from the links below - Copyright @ Springer VerlagThe potentialities of rotating coiled columns in countercurrent chromatography (CCC) and centrifugal field-flow fractionation (CFFF) are demonstrated. A rotating coiled column is a fluoroplastic or steel coil wound around a rigid cylindrical drum, which revolves about its axis and, at the same time, revolves around the central axis of the device called planet centrifuge. The stationary (liquid, solid, or heterogeneous) phase is retained in the column because of the centrifugal force field, and the mobile liquid phase is continuously pumped through the column. The methods for recovery, separation, and preconcentration of various trace elements in geological samples and high-purity substances with the use of two-phase liquid systems (CCC) are developed. Procedures are proposed for the continuous sequential extraction of various element species from soil and for the recovery of polycyclic aromatic hydrocarbons from sewage sludge with the use of natural suspensions or solid particulates as stationary phases. It is also shown that rotating coiled columns can be used in a new field, microparticle fractionation by CFFF
Crude oils as ore fluids: An experimental in-situ XAS study of gold partitioning between brine and organic fluid from 25 to 250°C
Organic matter can be associated with mineralization in hydrothermal ore deposits. One hypothesis is that this organic matter represents remnants of organic fluids (crude oils) that were competing with aqueous fluids for metal transport and contributed to metal endowment. We investigated the transport of gold (Au) in model oil compounds (S-free n-dodecane, CH3(CH2)10CH3, DD; and S-bearing 1-dodecanethiol, CH3(CH2)10CH2SH; DDT) from 25 °C to 250 °C using in-situ synchrotron X-ray absorption spectroscopy (XAS) experiments to determine the speciation and the structural properties of gold complexes in the aqueous- and oil-based fluids. For most experiments, DD or DDT were in contact with Au-bearing acidified water, or acidified water plus 10 wt% NaCl (pH25°C = 1.85 in both cases). Gold rapidly partitioned from the aqueous phase into DD and DDT. Below 125 °C, Au(III)Cl is dominant in the DD and the adjacent water with a refined coordination number (CN) of chloride of 4.0(3) and an AuCl bond length of 2.28 Å, consistent with the tetrachloroaurate complex (AuCl4−) being stable in both the aqueous and organic phases. In contrast, Au(III) is rapidly reduced in the presence of DDT and an Au(I) complex dominates in both water and adjacent DDT with a CN of sulfur ∼2.0, suggesting a [RS-Au-SR]− (RS = DDT with deprotonated thiol group) complex with AuS bond lengths ranging from 2.29(1) Å to 2.31(3) Å. In an open system of DDT in contact with water, of which the water and DDT were analyzed separately, AuCl4− was dominant in the water phase, and Au(RS)2− dominant in DDT, possibly due to different equilibration kinetics in the beaker and glassy carbon tube.
Since sulfur and organothiol compounds are ubiquitous and abundant components in natural oils, this study demonstrates the potential of natural oils to scavenge and enrich gold from co-existing gold-bearing brines. In particular, Au(I) organothiol complexes may contribute to transport in low-temperature (<125 °C) ore fluids such as those in basinal environments – in both hydrothermal fluids and oils. At temperatures ≥125 °C, gold was reduced to metallic gold in all experiments, suggesting that organo-stabilized nanoparticles may be the major form of gold to be scavenged, concentrated or transported in crude oils at these conditions. The results imply that brine-oil interactions may enrich Au in oils, and that oils may be an effective ore fluid in sedimentary environments