Zhixing Su

Synthesis of silica gel immobilized thiourea and its application to the on-line preconcentration and separation of silver, gold and palladium

A new silica gel based chelating sorbent with thiourea as a functional group was used for the flow injection (FI) on-line preconcentration and separation of trace levels of silver, gold and palladium. Its sorption characteristics were evaluated by FI-FAAS. The selected metal ions were adsorbed on a column packed with thiourea modified silica gel (TuSG) with a sampling flow rate of 5.0 ml min1, eluted with 5% thiourea with a flow rate of 2.5 ml min1 and determined by FAAS. Common co-existing ions did not interfere with the preconcentration and determination. The detection limits, defined as three times of the standard deviation of the blank (3σ), of Ag, Au and Pd are 1.3, 14 and 21 ng ml1, respectively, with a 1 min sample loading time. The RSD is not more than 3.0% for 0.040 µg ml1 of Ag, 0.20 µg ml1 of Au and 0.30 µg ml1 of Pd. With 40 min of the sample loading time, 1.0 ng ml1 of Ag, 5.0 ng ml1 of Au and 7.5 ng ml1 of Pd were successfully preconcentrated. The total dynamic capacity of TuSG was 24.5, 50.9 and 30.3 mg g1 for Ag, Au and Pd, respectively. The sorbent exhibited excellent stability. Its sorption properties did not change after 1000 cycles of use. The selected metals in a secondary nickel alloy, an anode slime, an electrolytic solution and three national certified ore samples were determined satisfactorily using the proposed method.

Application of a macroporous resin containing imidazoline groups to preconcentration and separation of gold, platinum and palladium prior to ICP-AES determination.

A new functional resin with a long functional side chain was synthesized by modification of aminated macroporous poly(vinyl chloride) resin with cyanoethylene and ethylenediamine. Traces of Au(III), Pt(IV) and Pd(II) in aqueous solution were quantitatively adsorbed in the acidity range of pH 4 and C(H(+)) 3 M. The rate of equilibration is high; Cu(2+), Fe(3+), Ni(2+), etc. exhibit little interference on the adsorption of the sought noble metals. The saturated adsorption capacities for Au(III), Pt(IV), Pd(II) and Ir(IV) in 2 M HCl were 4.0, 1.57, 2.26, 1.85 mmol g(-1). Adsorbed ions can be quantitatively desorbed by 4% thiourea +0.25 M H(2)SO(4). The resin has good reusability, and can be used for preconcentration and separation of Au(III), Pt(IV) and Pd(II) prior to their determination by ICP-AES with satisfactory results.

Application of isodiphenylthiourea immobilized silica gel to flow injection on-line microcolumn preconcentration and separation coupled with flame atomic absorption spectrometry for interference-free determination of trace silver, gold, palladium and platinum in geological and metallurgical samples

A simple and highly selective flow injection on-line preconcentration and separation–flame atomic absorption spectrometric method was developed for the routine analysis of trace amounts of silver, gold, palladium and platinum in geological and metallurgical samples. The selective preconcentration of the noble metals was achieved in a wide range of sample acidities (0.5–3.0 M HNO3 or HCl for Ag, Au and Pd) on a microcolumn packed with an isodiphenylthiourea immobilized silica gel (DPTSG). The noble metals retained on the microcolumn were effectively eluted with thiourea solution. With the use of a 0.85 mL microcolumn (about 0.14 g of DPTSG) the present system tolerated up to 25.0 mg mL−1 of common base metal ions and 100.0 mg mL−1 of anion when 0.040 µg mL−1 of AgI, 0.200 µg mL−1 of AuIII, 0.200 µg mL−1 of PdII and 1.00 µg mL−1 of PtIV were preconcentrated for 60 s with a sample flow rate of 5.0 mL min−1. The limits of detection were 0.33 ng mL−1 for AgI, 3.2 ng mL−1 for AuIII, 4.7 ng mL−1 for PdII and 69 ng mL−1 for PtIV, respectively, with the relative standard deviation being not more than 3.0%. The analytical results obtained by the proposed method for geological and metallurgical samples were in good agreement with the certified values.

2-Mercaptobenzothiazole-bonded silica gel as selective adsorbent for preconcentration of gold, platinum and palladium prior to their simultaneous inductively coupled plasma optical emission spectrometric determination

A 2-mercaptobenzothiazole-bonded silica gel chelating adsorbent(MBTSG) was synthesised by the Mannich reaction between 2-mercaptobenzothiazole and aminopropyl silica gel, and its adsorption characteristics were studied in detail. AuIII, PtIV and PdII can be quantitatively adsorbed by the adsorbent from aqueous solution at pH≤5.0 and CH+≤6 M. The adsorption capacities of AuIII, PtIV and PdII were >4.5, >6.5 and >18 mg per gram of dry MBTSG, respectively. The adsorbed metal ions can be readily desorbed with 3% thiourea in 3 M HCl solution. Other metal ions caused little interference in the preconcentration and simultaneous determination of AuIII, PtIV and PdII by ICP-OES. Concentrations of 2 ppb of Au, Pt and Pd can be determined reliably with a preconcentration factor of 250.

Synthesis and characterization of a macroporous poly(vinyl-aminoacetone) chelating resin for the preconcentration and separation of traces of gold, palladium, rhodium and ruthenium

An inductively coupled plasma atomic-emission spectrometry (ICP-AES) procedure is established with a new macroporous poly(vinyl-aminoacetone) chelating resin (PVAA) for preconcentration and separation of traces of Au(III), Pd(IV), Rh(III) and Ru(III) from sample solutions. The conditions of quantitative enrichment and desorption of these analytes from PVAA columns, including investigations of the stability, the regeneration capabilities and the adsorption capacities of that collector, are discussed. Moreover, interferences of foreign ions on the analytes are not observed and analysis of a real sample is performed with reliable results. Recoveries of these elements added to non-ferrous matrices are above 95% with relative standard deviations (RSD) between 2.0 and 4.0%.

Efficiency and mechanism of macroporous poly(vinylthiopropionamide) chelating resin for adsorbing and separating noble metal ions and determination by atomic spectrometry

Abstract A macroporous poly(vinylthiopropionamide) chelating resin was synthesized from spherical poly(vinyl chloride) resin particles and used for the enrichment and separation of trace noble metal ions. Trace Au(III), Pt(IV) and Pd(II) in sample solutions can be enriched quantitatively in the range 5 M HClpH 9 with recoveries > 96%, and the recovery of trace Ir(IV) at pH 1–9 was > 93%; however, the adsorption of Rh(III) and Ru(III) at pH 3–6 was −1 , the recoveries of Au, Pt, Pd eluted with 6% thiourea-1 M HCl and Ir with 6 M HCl were > 96%. The adsorption capacity of the resin was 978 ng g −1 for Au, 288 mg g −1 for Pt, 455 mg g −1 for Pd and 10 mg g −1 for Ir. When the resin was reused ten times, the recoveries of the above ions on enrichment were still > 92% and a 100-fold excess of other ions caused little interference in the determination of the ions. The eluted ions were determined by inductively coupled plasma atomic emission spectrometry (ICP-AES). The lowest concentrations determined were 0.040 μg ml −1 for Au, Pt and followed by Zeeman-effect atomic absorption spectrometry or ICP-AES were in good agreement with the certified values. The structures of the resin, investigated by Fourier transform IR spectrometry and electron spectroscopy revealed that Au, Pt and Pd ions were chelated mainly with the thioketo form of the thiorpropionamide group in the resin, forming a quadridentate chelate.

Synthesis and efficiency of a polyacrylacylisothiourea chelating fibre for the preconcentration and separation of trace amounts of gold, palladium and ruthenium from solution samples

A polyacrylacylisothiourea chelating fibre was synthesized using polyacrylonitrile fibre as a starting material, and the structure of the chelating fibre was determined by infrared spectrometry. The parameters influencing the efficiency of the fibre at concentrating trace amounts of AuIII, PdIV, and RuIII, including acidity, flow rate, adsorption capacity, effect of re-use, interfering ions, and desorption, were investigated. Gold(III), PdIV, and RuIII were enriched and separated from real samples and were detected using inductively coupled plasma optical emission spectrometry with satisfactory results. For concentrations of AuIII, PdIV, and RuIII of 0.008 mg l–1, the relative standard deviation was 1.8% for AuIII, 2.5% for PdIV, and 0.8% for RuIII. The concentrations obtained for these ions in real solution samples by this method were basically in agreement with the given values, with average errors of less than 2.5%. The method is rapid, precise, simple, and convenient to use.

Synthesis of poly(acrylamidrazone-hydrazide) chelating fiber and application of enrichment-separation for traces of indium, tin, chromium, vanadium and titanium from solution samples.

A poly(acrylamidrazone-hydrazide) chelating fiber has been synthesized from polyacrylonitrile fiber and used for enrichment-separation of traces of In(III), Sn(IV), Cr(III), VO(I) and Ti(IV) from solution samples with satisfactory results. These ions (5-250 ng/ml) can be quantitatively enriched (recovery > 95%) by the fiber at a 10 ml/min flow rate in the pH range 4-7, and desorbed quantitatively (recovery > 95%) with 10 ml of 2-5M hydrochloric acid from a fiber column at 6 ml/min flow rate. When the fiber, which had been stored in a glass bottle for about two years and then treated with strong acids (concentrated hydrochloric or nitric acid), was reused 10 times, the recoveries of the above ions by enrichment were still over 94%, and hundred-fold to thousand-fold excesses of Cu(II), Zn(II), Co(II), Ca(II), Mg(II), Fe(III) and Al(III) caused little interference in the determination of these ions by ICP-AES. The lowest concentrations for the proposed method were 50 ng/ml and In and Sn and 5 ng/ml for Cr, V and Ti. The RSD was 1.2-4.0%. The contents of these ions in real solution samples determined by this method were basically in agreement with the certified values of the samples, with average errors below 3.3%. The IR spectra of the fiber adsorbed with Cr(III) or VO(I) showed that Cr(III) or VO(I) combined mainly with nitrogen atoms in the fiber to form a coordination complex.

FAAS Determination of Platinum Using an On-Line Separation and Preconcentration System with a Polymelamine Dendrimer Immobilized Silica Gel

Abstract A G4.0 polymelamine dendrimer based on silica gel (PMDSG) was fabricated via a divergent approach via repetitive reaction of 2,4,6-trichloro-1,3,5-triazine and 1,6-hexylenediamine from a γ-aminopropyl silica gel (APSG) core for the first time. It was then used as the microcolumn packings for the flow injection (FI) preconcentration and separation of trace or ultra trace Pt(IV) for the flame atomic absorption spectrometry determination. A limit of detection (LOD) of 0.065 µg mL−1 was achieved when a 0.500 µg mL−1 Pt(IV) was preconcentrated at pH 3.0 with a sampling flow rate of 5.0 mL min−1 for 60 s and the relative standard deviation (RSD) was no more than 5.0%. The proposed method was successfully used for the determination of Pt in two metallurgical samples.

Performance for PAN-3 chelate fiber for adsorbing and separating trace uranium : determination by ICP-OES

An ICP-OES method is established for polyacrylamidoxime-carboxylic acid chelate fiber (PAN-3) adsorbing and separating trace uranium in waste water. The conditions for quantitative enrichment and desorption uranyl ions are investigated. The stability and the reuse performance of the chelate fiber are discussed. The interference of co-existent ions on uranyl ions as well as the analyses of samples are performed with satisfactory results. The lowest concentration of uranium determined by ICP-OES is 5 μg/l, its RSD is 2.6%.