Implementation of regrind–flotation pre-treatment of the CIL feed in a copper–gold plant

A regrind–flotation pre-treatment method developed to improve performance of a CIL circuit at copper–gold concentrators has been implemented at plant scale at the Newcrest Telfer mine. Low gold recovery in the CIL circuit due to the occlusion of gold by iron sulphide gangue minerals was overcome by the fine grinding of the CIL feed. A post-regrind copper flotation stage recovered liberated copper sulphide minerals allowing lower cyanide consumption in the subsequent CIL circuit than by regrinding alone. Gold recoveries achieved during the laboratory development of the regrind–flotation pre-treatment method have been replicated during the commissioning of the full-scale plant.     

Post-regrind selective depression of pyrite in pyritic copper–gold flotation using aeration and diethylenetriamine

The present study investigates the effect of aeration and diethylenetriamine (DETA) on the selective depression of pyrite in a porphyry copper–gold ore, after regrinding (at grind sizes, d₈₀ = 38 and 8 μm) with respect to Au recovery and grade using oxygen demand tests, flotation, QEMSCAN, X-ray spectroscopy (XPS) and EDTA extraction analysis. It was found that pyrite depression increases after aeration and with decreasing grind size. This was observed to be due to the markedly higher oxygen consumption rate of pyrite at the 8 μm (kla = 0.10 min⁻¹) than at the 38 μm grind size (kla = 0.02 min⁻¹). The addition of DETA improved pyrite depression (9% with aeration only versus 39% with aeration + DETA) at the 38 μm grind size. Gold and copper flotation recovery followed pyrite recovery for the two grind sizes using XD5002 in the presence of air and DETA.The surface analysis (XPS and EDTA extraction) revealed that the significant pyrite depression at the 8 μm grind size was due to increased amount of surface iron oxides, oxy-hydroxides (FeO/OH), sulphate species and increased liberation of mineral phases (QEMSCAN analysis), whilst the poorer pyrite depression at the 38 μm grind size was due to insufficient liberation of mineral phases and the persistence of activating Cu on the pyrite surface. The addition of DETA increased pyrite depression at the coarser grind size due to a significant reduction in Cu(I)S and increased Cu(II)O species, correlating with the flotation results of pyrite under this test condition. Two-stage copper and pyrite flotation, followed by Au cleaning after regrinding to 38 μm grind size, under high pH or aerated condition is proposed as the recommended route to optimise Au flotation.     

Assessing the potential of activated bagasse as gold adsorbent for gold–thiourea

This study was conducted to establish the potential of bagasse, the fibrous by-product of sugarcane milling operation, as a precursor for preparing adsorbents for gold–thiourea complex. It was also of interest to identify the carbon properties, which promotes adsorption. Bagasse was activated in this study by physical (gasification) and chemical techniques. It was found bagasse is more amenable to activation by physical techniques producing activated carbon with surface areas exceeding 1000 m²/g. Among the chemical activating agents, it was found that ZnCl₂ was most effective in developing the surface structure of bagasse. Gold–thiourea adsorption was found to be favoured in carbon exhibiting high surface area. Finer pore sizes are developed with higher surface area. As such the extent to which the surface area could improve adsorption was limited by steric hindrance in the finer pore size. It was found that steric hindrance affected gold–thiourea adsorption in mean pore sizes less 20 Å. The effect was particularly significant when the carbon pH was greater than 7.0, where the alkaline nature of the carbon may have shifted the Tu/Au ratio to higher values such that the formation of the larger AuTu₂⁺ and AuTu₃⁺ are promoted. The greater development of physically activated bagasse favoured gold–thiourea adsorption. The optimum adsorption capacity by the physically activated bagasse was approximately 318 mg Au/g of adsorbent (ash free), achieved after 25 h of gasification in 15% CO₂. This was comparable to adsorption capacities obtained from commercial activated carbon and resins of 197–321 mg Au/g adsorbent (ash free). These results are encouraging and confirm the potential of activated bagasse as gold–thiourea adsorbent.     

The interaction of lignosulfonate dispersants and grinding media in copper–gold flotation from a high clay ore

This study was conducted to explain an inconsistent observation in the previous study that a lignosulfonate-based polymeric dispersant improved copper and gold flotation from high clay ores significantly in laboratory but clear improvement was not observed during the full-scale plant trial (Seaman et al., 2012). In this study the flotation of low and high clay ores after grinding with different grinding media was performed to understand the interaction of lignosulfonate dispersant and grinding conditions equipped with rheology measurements and EDTA (ethylene diamine-tetra acid) extraction. It was found that lignosulfonate dispersant mitigated the negative effect of clay minerals on copper and gold flotation when the amount of iron oxidation products originated from the grinding media was minimised. Mild steel media produced a great amount of iron oxidation products depressing copper and gold flotation and masking the role of the dispersant.     

The interaction of clay minerals with gypsum and its effects on copper–gold flotation

The interaction of two clay minerals, kaolinite and bentonite with gypsum and its effects on the flotation of a copper–gold ore was investigated in this study. It was found that bentonite increased the viscosity more than kaolinite when mixed with the copper–gold ore at low shear rates. The detrimental effect of these clay minerals on flotation was attributed to the entrainment of clay particles when kaolinite was added to the ore and to a decrease in true flotation by bentonite. Bentonite formed a sponge-like structure with predominant edge–edge (E–E) interactions which might affect hydrodynamics in the flotation cell and have a detrimental effect on flotation recovery. Kaolinite did not form a particular network structure and its aggregates mostly consisted of face–face (F–F) type associations which did not affect flotation hydrodynamics. The addition of gypsum to the ore–bentonite mixture inhibited the formation of interconnected network structures. This led to lower viscosity values with flotation behaviour similar to that of mixtures with kaolinite. In this case, there was an improvement in recovery, but the grade decreased due to entrainment. The addition of gypsum to the ore–kaolinite mixture created aggregates with long strings further enhancing particle entrainment with more mass transported to the froth.     

Thermodynamic modeling of dearsenation of rebellious gold–quartz–arsenic ore in water vapor

The article describes theoretical and experimental data on dearsenation of gold-containing scorodite ore in water vapor. It is shown that roasting of scorodite with pyrite in super-heated vapor enables complete removal of arsenic and sulfur in the form of sulfides from the original material and exposes noble metals.     

The effect of mechanical–physical pretreatment on hydrometallurgical extraction of copper and tin in residue from printed circuit boards from used consumer equipment

This work is focused on studying mechanical–physical pretreatment of printed circuit boards from used consumer equipment followed by extraction of copper and tin from residue fractions by leaching in hydrochloric acid solutions. Mechanical–physical pretreatment was realized in three different procedures. Key processes were electro-dynamic separation, cross-flow air sifter separation and air table separation, respectively. Leaching experiments were carried out in 1 M and 2 M HCl at 80 °C. The results show that cross-flow air sifting leads to the highest accumulation of non-ferrous metals in a residue fraction. From this fraction, the highest extraction of tin with minimal copper extraction was achieved.     

Sulfhydryl phosphorus-containing collectors in flotation of copper–nickel platinum-group metals

The analysis involves influence of sulfhydryl phosphorus-containing collectors (SPC) on flotation of copper–nickel ore-bearing metals from platinum group. Efficiency of SPC and butyl xanthate combination is illustrated, and their optimal ratio is determined. The authors study influence of the test agents on electrode potential and hydrophobic behavior of pyrrhotine, pentlandite and platinum black. UV and IR spectrophotometry has shown origination of disulfide di-isobutyl dithiophosphinate on the surface of pyrrhotine.     

Accumulation of heavy metals by naturally colonising Typha domingensis (Poales: Typhaceae) in waste-rock dump leachate storage ponds in a gold–copper mine in the central tablelands of New South Wales,Australia

Abstract

Naturally colonised populations of Typha domingensis in mine waste-rock dump leachate ponds (northern leachate pond [NLP] and southern leachate pond [SLP] and a nearby reference site (Cadiangullong Creek [CAC] were analysed for accumulation of Cu, Mn, and Zn in the winter of 2010 and early autumn of 2011. Concentrations in sediment, leachate and creek water at NLP, SLP, and CAC were also analysed for Cu, Mn, and Zn. Linear regression of Cu, Mn, and Zn concentrations in the leachate at each site revealed a significant reduction in these metals at NLP only in early autumn as leachate travelled away from the toe of the waste-rock dump and through the naturally colonised populations of T. domingensis. This study indicates that this species is a suitable candidate for the process of phytoimmobilisation of the tested metals.     

The effect of a new polysaccharide on the depression of talc and the flotation of a nickel–copper sulfide ore

The effect of the depressant galactomannan (KGM) on the depression of talc and the flotation of a nickel–copper sulfide ore have been investigated through microflotation, batch flotation and industrial flotation tests, zeta potential and infrared spectrum measurements. The flotation results indicated that KGM had a straining influence on the depression of talc while had little effect on nickel minerals flotation. Compared with the depressant carboxymethyl cellulose (CMC) and guar gum, the KGM increased the nickel recovery dramatically, it not only negated the need for a talc removal process, but also achieved a significant decrease in the depressant consumption by half. Zeta-potential and infrared spectrum measurements illustrated that chemical adsorption was seen between KGM and talc, and a possible weak physical adsorption was seen between KGM and pentlandite. This was the reason why KGM had high depression selectivity for talc and little depression effect on nickel minerals.     

Rational separation of complex copper–zinc concentrates of sulfide ore

Monomineral and compound fractions, ore material and concentrates are used to study the effect of basic processing factors on mineral separation. The key criteria are determined to choose a method of selective extraction of minerals and their species in various cycles of a process flow chart. Such key criteria include: degree of activating effect of copper minerals on other sulfides; multifunction role of iron compounds; medium pH values; combination and concentration of depressing ions of modifying reagents; ratios of selective collectors in their combinations; scientific principles of flow chart designing; principles of concentration and recovery of minerals in different processes of dressing.     

Study of silver leaching with the thiosulfate–nitrite–copper alternative system: Effect of thiosulfate concentration and leaching temperature

Thiosulfate system is considered an interesting alternative leaching process for precious metals. Nevertheless, most of the literature published on these conventional thiosulfate leaching solutions has been focused on the use of ammonia and copper to generate the cupric tetraamine complex, which acts as a catalytic oxidant for silver. However, ammonia toxicity is also a detrimental issue in terms of the process sustainability. For that reason, thiosulfate–nitrite–copper solutions were studied as an alternative less toxic system for silver leaching.In this work, the effect of the thiosulfate concentration (0.07 M, 0.1 M and 0.15 M) and temperature (room temperature, 30, 35, 40 and 45 °C) on the metallic silver leaching kinetics is presented for the S₂O₃–NO₂–Cu system. The results show that the thiosulfate concentration plays an important role in the S₂O₃–NO₂–Cu–Ag system since it controls the silver leaching kinetics. On the other hand, an increase in temperature favors the silver recovery.Finally, the SEM–EDS analysis, the X-ray mapping and the X-ray diffractograms show that the solid silver particles are coated by a Cu, S and O layer for the 0.07 M and 0.1 M thiosulfate experiments, which is consistent with the formation of antlerite (Cu₃(SO₄)(OH)₄); while the 0.15 M thiosulfate scenario produced a layer composed only of Cu and S, revealing the formation of stromeyerite (CuAgS). The UV–Visible technique confirmed the in-situ generation of copper–ammonia complexes for the 0.07 M leaching condition; however, these complexes are not formed at the 0.15 M condition.     

Simultaneous sulfide oxidation and gold leaching of a refractory gold concentrate by chloride–hypochlorite solution

In this research, oxidation of sulfide and leaching of gold from a gold–bearing sulfide concentrate using chloride–hypochlorite solution has been investigated. Effects of calcium hypochlorite concentration, initial pH and sodium chloride concentration on the recovery of gold were examined. Two conditions were considered; the stability range of the gold complex (Eh > 900 mV) and formation of chlorine gas (pH < 3.5). During leaching, due to oxidation of sulfide and generation of acid, pH dropped. About 82% of gold was extracted from 200 g/L concentrate after 2 h using 200 g/L Ca(OCl)₂, 200 g/L NaCl at initial pH of 11, stirring speed of 600 rpm and temperature of 25 °C.     

What Limits the Productivity of Acid Mine Drainage Treatment Ponds?

Abstract.  Acid mine drainage (AMD) treatment ponds are very common in the U.S. Appalachian coal region and are the main source of many headwater streams. Though the water that discharges from these ponds generally meets state and federal water quality standards, there is a distinct lack of productivity in most of these ponds. Our first objective was to compare the productivity of chemically-treated, biologically-treated, and untreated AMD ponds with uncontaminated (reference) ponds. Next, we used principal component analysis and multiple regression of 20 physicochemical characteristics of these ponds to resolve which factor(s) were responsible for inhibiting productivity. We discovered that chemically-treated AMD ponds and untreated AMD ponds exhibited significantly less gross primary productivity (GPP) than reference ponds; biologically-treated ponds (containing AMD that has passed through a wetland) did not vary significantly from reference ponds. Chemically-treated ponds also had significantly less net primary productivity (NPP) than reference ponds. Community respiration did not vary among the pond types. Our test results indicated that soluble reactive phosphate concentration explained most of the variance in both GPP and NPP. Apparently, phosphate availability, not metal toxicity, regulated phytoplankton productivity in these ponds.     

Hydro–pyro integration in the processing of nickel laterites

Hydrometallurgical process routes are seen to be the future of treatment of the lower grade nickel laterites ores. Hydrometallurgical projects of recent years have focused on HPAL and have been largely unsuccessful economically so far, with huge capital cost overruns.The simplest and least capital intensive of the possible alternatives to HPAL is atmospheric heap leaching. Development work is also underway by several companies into atmospheric tank leaching which is also a potentially viable alternative.The natural product for a leaching process is a high grade nickel intermediate either from a direct precipitation process (containing approx. 36% Ni) or via ion exchange (>50% Ni).There are many existing pyrometallurgical facilities which could easily be adapted to take this nickel intermediate giving them significant potential benefits especially as nickel laterite ore grades diminish. The nickel production from these plants could also be increased and for new plants large capital and operating cost savings achieved by using suitable intermediates.There are also potential environmental benefits with much less energy consumed and lower greenhouse gases emitted per tonne of nickel produced.In the future an integrated hydrometallurgical plant with attached existing smelter or a more advanced pyrometallurgical smelting process (e.g. a DC arc furnace) could well be the way forward for new projects.     

Assessment of water quality effects on flotation of copper–cobalt oxide ore

Results from lab scale flotation show that when process water was re-used copper and cobalt recovery from an oxidized ore decreased respectively with 25% and 30% at the rougher stage bringing lower grade concentrate as well. The presence of thiosulphate ions contributed to slow down of NaHS consumption during sulphidisation of pure malachite and hindered collector adsorption. Elevated concentration of thiosulphate ions affected malachite surface properties and induced dissolution effects. DRIFT spectroscopy on activated malachite enabled to reveal the effects of thiosulphate ions presence with hydrophilic species being identified.     

Study on the preparation and properties of ultrafine copper powder

1IntroductionAs ani mportant raw material of powder metallurgy products,copper powder plays a vital role in in-dustrial fields.There are many methods for preparation of copper and copper based powder as follows[1-5]:electrolytic technique,gas-reduction technique,atomization machanical smashing,permutation,high-pres-sure hydrogen reduction,microbe lixiviation,and so on.Recently,high energy ball millingis used widelyin preparation and sythesis of materials such as dispersion intensified alloy ma…     

Stress–Strain State of Rock Mass in the Zone of Tectonic Fractures in the Korobkov Iron Ore Deposit

The actual lithostatic stresses are calculated with regard to physical characteristics and structural features of rock mass. The results are compared with the in-situ observations. It is shown that vertical stresses naturally grow with depth though their values are very different along horizontal cross sections due to the complex structure of rock mass. On the average, the vertical stresses are close in values to the lithostatic stresses. The horizontal stresses measured by the borehole slotter method are many times higher than their calculated values, which is governed by the nonunform properties of rocks or is reflective of tectonic compression.     

Genetic algorithms for the optimisation of the Schwartz–Smith two-factor model: a case study on a copper deposit

Mining companies typically seek ways to hedge risks affecting their production. One useful instrument to mitigate the financial risk is the futures contracts on commodity prices. Information from the transactions in futures markets is publicly available and can be analysed with the Schwartz–Smith two-factor model (SSTF). However, finding the parameters governing this model can be very challenging. This step is done using a deterministic optimisation approach called the Expectation–Maximisation algorithm (EM). The starting values of the model will have a significant effect on the convergence of the EM. To ensure the solution does not get stuck in a local maximum, the EM algorithm is performed multiple times with different starting values. This paper assesses the value of genetic algorithms (GA) to optimise the parameters of the SWTF model. Although they are slower than EM algorithms because they use random number generators to search for the optimal solution, GA optimise a population of solutions instead of working on only one solution at the time. Moreover, a constraint on the range parameter can be applied to ensure the parameter has a sound economic meaning. Once the SWTF parameters have been calibrated on the observation of futures contracts, the model can be used for the simulation of spot and futures prices. To demonstrate the performance of the proposed approach, a case study was conducted on a copper deposit. The simulations based on the SWTF model whose parameters are determined by GA are used. An active management strategy of the stockpile, dependent on discrepancies in commodity futures prices is tested. Results show that the active management strategy produces positive returns over the passive investment approach.     

Effect of calcium and thiosulfate ions on flotation selectivity of nickel–copper ores

Effect of calcium and thiosulfate ions on flotation of a Ni–Cu ore was investigated. The ions improved the flotability of sulfides at the normal process pH after grinding in steel mill. Calcium activated especially nickel and copper sulfides when the galvanic effect of mill iron was effective. The UV/Vis measurements showed that calcium ions increased xanthate adsorption on the sulfides. The effect of thiosulfate was different. It was concluded that thiosulfate reduced the effect of hydrophilic compounds on sulfide particles, and in that way improved their flotation.