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1

The effect of nut shell addition on the permeability of a crushed gold ore

Yilmaz S., Sirkeci A. A., Bilen M., Yigit I., Kizgut S.

Physicochemical Problems of Mineral Processing

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2018

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Vol. 54, iss. 2

467--475

EN

In this study, variations in permeability of a gold ore by nut shell addition was studied. Ore particle size, nut shell size and volume fraction in the ore were the parameters investigated. Permeability is an important issue in heap leach operations considering the processing duration. Particularly below 6 mm particle size permeability is greatly hampered. Turkey is the leading country in the world in hazelnut production. Therefore, considerable amounts of nut shell are obtained as a by-product. Incerase in the permeability of a finely crushed ore will obviously enable an increase in the leaching efficiency. The finer the particle size the more the liberation of gold is yet the permeability is lower. Therefore, this study focuses on the possibility of improving the permeability of ore heaps with nut shell addition. Optimum amount of nut shell which should be added to the ore was found to be 5% by volume. It was found that the permeability of ore crushed below 2.36 mm considerably increased by the addition of nut shell below 18 mm.

2

Thiosulfate-copper-ammonia leaching of pure gold and pressure oxidized concentrate

Porvali A., Rintala L., Aromaa J., Kaartinen T., Forsen O., Lundstrom M.

Physicochemical Problems of Mineral Processing

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2017

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Vol. 53, iss. 2

1079--1091

EN

In this research cyanide-free leaching of pure gold and pressure oxidized refractory gold concentrate by thiosulfate-copper-ammonia solutions were examined. A quartz crystal microbalance (QCM) was used to study gold leaching as a factorial series where the best gold leaching rate (2.987 mg/(cm2∙h)) was achieved with a solution consisting of 0.2 M (NH4)2S2O3, 1.2 M NH3, 0.01 M CuSO4 and 0.4 M Na2SO4. Temperature had the greatest effect on the gold leaching rate. An increase in thiosulfate concentration (0.1–0.2 M) increased gold dissolution. The combined effect of temperature and ammonia concentration had a statistically significant effect on the gold leaching rate at 0.1 M M2S2O3. Combination of applied potential and NH3:S2O3 ratio had a statistically significant effect on the gold leaching rate at 0.2 M M2S2O3. An increase in applied potential decreased the gold dissolution rate at low ammonia concentrations but increased it at high concentrations. A pressure oxidized gold concentrate was leached for 6 hours in the batch reactor leaching experiments. The effect of rotative velocity (1.26–1.56 m/s) and slurry density (10–30 wt%) was investigated at the following leaching parameters: 0.2 M Na2S2O3, 0.6 M NH3, 0.01 M CuSO4, 0.4 M Na2SO4. Lower slurry density (10 wt%) resulted in a higher Au leaching efficiency. An increase in the rotation rate did not have an effect on the final Au leaching recovery. The best Au leaching efficiency (89%) was achieved with 590 rpm mixing, 1.56 m/s rotative velocity and 10 wt% slurry density.

3

Dissolution of gold with cyanide replacingreagents

Aromaa J., Rintala L., Kahari M., Forsen O.

Physicochemical Problems of Mineral Processing

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2015

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Vol. 51, iss. 1

269--279

EN

Cyanide is used in the leaching phase of hydrometallurgical recovery of gold. The toxicity and environmental risks have created a need for safer alternatives. There is a vast amount of information about gold extraction and a selection has been collected and formalized to be used in a decision support tool. The tool Auric Advisor uses case-based reasoning (CBR) to provide process alternatives for the user queries. The aim of this paper is to study leaching of gold with cyanide replacing alternatives such as ammonium thiosulfate, chloride-hypochlorite, thiourea and thiocyanate to provide new cases for the tool. The behaviour of gold was examined with electrochemical tests and weight loss measurements a using quartz crystal microbalance (QCM) were used to determine the dissolution rate. Based on literature, the dissolution rate determined for cyanide solution was 2.5 mgcm-2h-1. Based on polarisation experiments and potential measurements, the ammonium thiosulfate system with cupric ion as oxidant was estimated to dissolve gold slower than cyanide. In the QCM tests the chloride-hypochlorite alternative showed highest dissolution rate of 8.6 mgcm-2h-1 at the redox potential of 900 mV vs. SHE. The thiocyanate system with ferric ion dissolved gold at a rate of 3.4 mgcm-2h-1 at the redox potential of 620 mV vs. SHE. Thiourea system with ferric ion showed the dissolution rate of 1.65 mg cm-2 h-1 at the redox potential of 450 mV vs. SHE. The results of the rapid tests were comparable with literature and were included in the case base of the Auric Advisor decision-support tool.

4

Surface enhanced raman scattering spectroelectrochemical studies of mineral processing

Hope G. A., Woods R., Watling K.

Physicochemical Problems of Mineral Processing

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2002

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Vol. 36

21-38

EN

The application of in situ surface enhanced Raman scattering (SERS) spectroscopy to aspects of mineral processing is discussed. In the study of flotation systems, SERS has been used to characterise the species formed on coinage metal surfaces over a range of controlled potentials for ethyl, i-propyl, i-butyl and i-amyl xanthates, for O-isopropyl-N-ethylthionocarbamate (IPETC), for 2-mercaptobenzothiazole (MBT), and for diisobutyl dithiophosphinate (DIBDTPI). For each collector, adsorption occurs via charge transfer to form a metal-sulfur bond and, in situations in which the reversible potential for the formation of the bulk phase is known, at underpotentials. The dissolution of silver in basic solutions containing cyanide has been shown to be inhibited by MBT and by DIBDTPI as a result of the chemisorption of the collector species. In hydrometallurgy, SERS has been applied to the investigation of gold leaching. Changes in the surface species that occur during gold cyanidisation as the potential is varied have been identified from SERS spectra recorded in real time on voltammograms. In electrometallurgy, SERS investigations of copper electrodeposition from sulfuric acid solutions have shown that a transient surface sulfate species is involved in the plating process.

PL

W pracy przedyskutowano zastosowania spektroskopii rozproszenia ramanowskiego (ze wzmocnieniem sygnału wskutek odbicia promieniowania od powierzchni - SERS) w badaniach związanych z procesami przeróbki minerałów w których widmo wykonywane jest in situ. W układach flotacyjnych zastosowano SERS do charakterystyki pokryć na metalach z grupy miedzi, powstających w wyniku oddziaływania na te metale w warunkach kontrolowanego potencjału roztworów ksantogenianów: etylowego, izopropylowego, izobutylowego i izoamylowego, a także o-izopropylo-Netylotionocarbaminianu, 2-merkaptobenzotiazolu oraz dwuizobutylo dwutiofosfonianu. W przypadku wszystkich kolektorów adsorpcja następuje w wyniku przeniesienia ładunku z wytworzeniem wiązania metal-siarka, a jeśli znany jest odwracalny potencjał tworzenia fazy objętościowej to można stwierdzić, że wiązanie z powierzchnią następuje przy potencjale niższym niż dla reakcji w fazie objętościowej. Zaobserwowano, że roztwarzanie srebra w zasadowych roztworach cyjankowych jest silnie spowalniane w wyniku chemisorbcji 2-merkaptobenzotiazolu i dwuizobutylo dwutiofosfonianu. W zakresie hydrometalurgii zastosowano SERS do badania ługowania złota. Stosując rejestrację widm SERS w trakcie wykonywania woltamperogramów przy zmieniającym się potencjale obserwowano zmiany w składzie warstw powierzchniowych na złocie w wyniku traktowania powierzchni złota cyjankami przy różnych potencjałach. SERS zastosowano również do badania procesów elektrometalurgicznych, stwierdzając że w procesach osadzania miedzi z kwaśnych roztworów siarczanowych bierze udział przejściowy produkt zawierający grupę siarczanową.

5

A combined chemical and biological heap leaching of an oxide gold-bearing ore.

Groudev S. N., Spasova I. I., Ivanov I. M.

Fizykochemiczne Problemy Mineralurgii

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1999

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Vol. 33

55-61

EN

A heap consisting of an oxide gold-bearing ore contgaining 3.5 g/ton of gold and 14.0 g/ton of silver was leached by solutions containing amino acids of microbial origin and thiosulfate as gold-complexing agents. 68.4% of the gold and 53.6% of the silver were leached within 20 days in this way. The pregnant solutions after leaching were treated by cementation with metallic zinc. Mixed gold-bearing concentrations containing also zinc and copper as valuable components were the products from the cementation.