Determination Of Gold In Ores Research Articles

Sodium peroxide fusion for reliable determination of gold in ores and metallurgical samples

A protocol based on peroxide fusion has been developed for the determination of Au in metallurgical samples and ores covering a wide range of concentrations and diverse mineralogies. The quantity of Na2O2 required was minimised, while maintaining lixiviant efficacy, by the use of mixed NaOH + Na2O2 fluxes. The method was shown to be particularly applicable to the determination of coarsely-particulate gold. Fusion cakes were dissolved in hydrochloric acid and then extracted using methylisobutylketone to provide concentrations appropriate for quantification by graphite furnace atomic absorption spectroscopy and to minimise interferences from dissolved salts. The protocol was tested on a variety of certified reference materials and produced results in excellent agreement (at Au concentrations ranging from 0.05 to 47μgg−1) with the traditional lead fire assay method, while avoiding the health and safety issues associated with that technique.

Flow-injection spectrophotometric determination of gold using 5-(4-sulphophenylazo)-8-aminoquinoline

Gold (0–75 μg ml −1) was determined spectrophotometrically at 605 nm in a flow injection (FI) system based on the reaction of gold(III) and 5-(4-sulphophenylazo)-8-aminoquinoline (SPA) in the presence of cetyltrimethylammonium bromide (CTAB). The carrier stream was 1% (w/v) disodium ethylenediaminetetraacetate and the reagent streams were 2.0 × 10 −4 M SPA and 0.6% (w/v) sodium hydroxide solution. The sample solution was mixed with 0.2% (w/v) CTAB solution prior to injection. The various chemical and physical variables were optimised and a study of interfering ions was carried out. The relative standard deviation for the determination of 5 μg ml −1 gold was 0.9% ( n = 10) and the limit of detection (blank signal plus three times the standard deviation of the blank) was 1.1 μg ml −1, both based on injection volumes of 60 μl. The method has been successfully applied to the determination of gold in ores and anode slimes.

Comparison of chemical modifiers used for the determination of gold in ores by electrothermal atomic absorption spectrometry

The interference effects of major matrix elements, contained in gold ores (silicate-, oxide-, sulfide-, bismuth- and tellurium-ores) for the determination of gold by electrothermal atomic absorption spectrometry (ETAAS), were studied. Samples of five one-component (Cu, Mo, Ni, Pd and V) and 12 two-component chemical modifiers composed from above five one-component modifiers were compared for their anti-interference effects on the major matrix elements (Al, As, Bi, Ca, Cu, Fe, Mg, Mn, Pb, Sb, Te and Zn) in gold ores. A chemical-modifier solution composed of 1000 mg l −1 each of Ni and V showed the best performance. Gold in five decoppered copper oxide ores was determined by ETAAS with the help of the Ni/V chemical modifier without matrix pre-separation. The relative standard deviation was 3.9% ( n=9) for 0.47 mg l −1 gold. The recoveries of added gold (50 mg l −1) were 93–102%. The characteristic mass was 12.8 pg.

Potentiometric titration of gold in ores with potassium iodide

A direct potentiometric titration method for the determination of gold in ores and alloys is described. It is based on the reduction of Au(III) with iodide ions yielding accurate and reproducible results. Detection limit and sensitivity were 0.06 and 0.032 mg/l Au, respectively. The linear response range was between 0.1 and 120 mg/l Au. The method can be used for the routine assay of gold in different kind of samples.

Determination of trace gold by solid surface chemiluminescence analysis

A solid surface chemiluminescence method for the determination of gold in ores is proposed. Several solid materials could be used for the purpose, foamed plastic being the best. The method permits the selective determination of 0.1–10 μg of gold adsorbed on foamed plastic with a relative standard deviation of less than 10%.

Evaluation of the reduction factor for the determination of gold in ores by epithermal neutron activation analysis

The underestimation (or reduction factor) of gold (198Au) in ore samples due to the self-shielding of epithermal neutrons during epithermal neutron activation analysis (ENAA) was measured. Three synthetic ores with different size ranges of gold particles were prepared and analysed by NAA and ENAA. Epithermal neutron activation analysis was found to underestimate gold in synthetic ores containing gold particles with size ranges of ⩽53, 53–150 and 150–250 µm by the factors 11, 31 and 33%, respectively, in comparison with NAA. A reduction factor of 5% was also measured for gold in reference ore MA-1, certified by CANMET Canada, with 80% of particles below 37 µm.

Determination of gold in ores by flame and graphite furnace atomic absorption spectrometry using a vanadium chemical modifier

The determination of gold in ores by both flame and graphite furnace atomic absorption spectrometry at different analytical wavelengths are compared. Vanadyl chloride was shown to be effective as a chemical modifier for determining gold in the presence of heavy metals. A sensitivity of 1 μg l −1 and a detection limit of 1 μg l −1 (or 0.1 μg g −1 in the original sample) were obtained. The best linear range was between 1 and 120 μg l −1 and a characteristic mass of 1 pg was obtained.

Determination of gold in complex sulphide minerals by differential-pulse anodic stripping voltammetry after anion-exchange separation

A method is described that is suitable for the determination of gold in ores, concentrates, residues and solutions obtained from pilot-plant metallurgical research on complex sulphides. Gold(III) is selectively absorbed from nitric acid solution on an anion-exchange resin. Gold is eluted from the column with dimethylformamide-nitric acid at 65 °C. The gold in the eluate is determined by differential-pulse anodic stripping voltammetry using a glassy carbon electrode. The samples analysed ranged in gold concentration from 0.5 to 35 µg g–1. Results obtained for gold in two Canadian Certified Reference Material Project ores were in good agreement with the certified values. The relative standard deviations were 1–2%.

1,2,4,6-Tetraphenylpyridinium perchlorate as a reagent for ion-association complex formation and its use for the spectrophotometric determination of gold

The synthesis, characteristics, and applications of 1,2,4,6-tetraphenylpyridinium perchlorate (TPPP) as an agent that forms ion-association complexes is described. This new spectrophotometric analytical reagent forms with AuCl 4 −1 a 1:1 complex which is slightly soluble in water and can be extracted with isopentyl acetate, with maximum absorbance 313 nm, molar absorptivity 3.44 × 10 4 liters mol −1 cm −1. The variables involved in the formation and extraction of the complex in the mentioned organic solvent are studied. In the selected conditions, 1 M hydrochloric acid medium, the extraction efficiency was 95.3%. The apparent stability constant of the complex is log K = 5.9 ± 0.1 at 20 °C. The extracted complex is useful for the spectrophotometric determination of gold in the range of 0.05 to 0.5 ppm. Standard deviation at 0.2 ppm (10 determinations) was 0.0022 and the relative error was ±0.78%. The interferences of many foreign ions are studied, concluding that the procedure proposed shows a high selectivity. The method has been applied satisfactorily to the determination of gold in ores, leads and other materials.

Neutron-activation determination of gold in ores in an automated version

The transition to semiconductor spectrometry made it possible to build a completely automated analyzing system and to improve some parameters of the method, In measurements on a semiconductor spectrometer (Fig. i) [Ge(Li) detector with a volume of 50 cm ~, resolution of 3.5 keV with respect to the ~~ line, Ey = 1332.5 keV] with a multichannel analyzer, the limit of gold determination attained (0.01-0.02 g/ton) was roughly an order of magnitude lower than in the scintillation variant with an rms error of ~30% (the threshold signal/background ratio for the 412-keV analytical line being 0.05). The influence of some noise (e.g., ~Yb, Ey = 395.6 keV), which is appreciable for ores from some deposits, has been eliminated.

Spectrophotometric determination of gold with 2-(p-methoxyphenyl)-5,7-diphenyl-1,3,4-thiadiazolo-(3,2-a)-pyridinium chloride

In 0.4M hydrochloric acid medium, gold(III) forms with 2-(p-methoxyphenyl)-5,7-diphenyl-1,3,4-thiadiazolo(3,2-a)pyridinium chloride (TDZP) an ion-association compound which is extractable into isoamyl acetate. The extracted ion-pair, which has an Au:TDZP mole ratio of 1∶1, is used for the spectrophotometric determination of gold (e=3.80 x 104l·mole−1·cm−1) in the concentration range 1–25μg of gold per 5 ml of organic solvent. The interference of a number of foreign ions has been investigated. The method is applicable to the determination of gold in ores.

Specific solvent extraction method for the determination of gold in ores and products

The development of, and the recipe for, the extraction of gold from ores and products are described.Samples, suspended in dilute hydrochloric acid, are shaken for up to 3 h with amyl acetate containing a small proportion of bromine. The bromoaurates thus formed are extracted into the organic phase with excellent reproducibility and virtually 100% efficiency. The method appears to be completely specific for gold in that, of 25 elements tested, none was found in the extract in more than trace amounts.By adjusting the sample masses and volumes of hydrochloric acid and amyl acetate, extracts can be made suitable for the determination of gold by a choice of methods; electrothermal and flame atomic-absorption spectrometry and gravimetry have been applied for sample masses in the range 0.05–400 g.In both accuracy and precision the results compare favourably with those from standard methods, while comparison between the method of standard additions and the direct use of a calibration line on small samples containing 0.1–0.3 p.p.m. of gold is excellent.

The determination of gold in ores by atomic absorption spectrometry after chromatographic separation

The determination of gold in ores by atomic absorption spectrometry after chromatographic separation

Atomic absorption spectrophotometric determination of gold in ores

Atomic absorption spectrophotometric determination of gold in ores

The determination of gold in ores and solutions by activation analysis with a neutron generator

THE DETERMINATION OF GOLD IN ORES SOLUTIONS BY ACTIVATION ANALYSIS WITH A NEUTRON GENERATOR There is a continuing need for more sensitive and more rapid techniques for the direct analysis of gold in solutions and in the ore bodies of the Witwatersrand series in South Africa. Neutron-activation analysis has been investigated with a small accelerator type of neutron generator yielding 14 MeV, and thermal neutrons. The results presented indicate that only in special circumstances does this technique offer any advantages over the conventional assay methods.

An experimental evaluation of neutron activation, wet assay and fire assay methods of determining gold in ores

The errors associated with fire assay, wet extraction and neutron activation methods are evaluated, the accuracy and precision of these methods are compared, and a method of determining chemical recovery in the activation determination of gold in ores and concentrates is presented.