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By J. Petersen, T. Moyo, D. Maharaj

This study investigates the effect of ammonium thiosulfate on the leaching of gold from the contacts of unpopulated cut electronic printed circuit boards (PCBs). Studies in the literature show ammonium thiosulfate to be a viable option in comparison to the commonly used but hazardous cyanide leaching route. However, the simultaneous dissolution of Cu interferes with the Au leaching reaction, often limiting the extraction to moderate levels. To optimize the system, an ammoniumthiosulfate system containing 0.5M ammonia, 0.5M ammonium thiosulfate, and Cu(II) sulfate at varying concentrations was studied as an alternative hydrometallurgical option for the recovery of gold from PCB. Tests were done with unpopulated standardized model PCBs (cut to 15 x 30mm pieces). Gold extraction of 47.3% was achieved after a 24-hour leaching experiment with a 0.02M copper background concentration. Further experiments focused using different initial background Cu concentrations (0M – 0.1M) to determine its effect on both gold and copper extractions. An initial Cu concentration of 0.045M resulted in the highest gold extraction, with 93.7% extraction after 6 hours of leaching. Further analysis of the data shows that the kinetic rate of gold leaching is correlated in a first-order dependence with the actual copper concentration in the solution, which increases with the concomitant dissolution of copper and gold from the PCBs. A lower threshold of 0.017M and an upper threshold of 0.15M copper in solution were determined, in between which gold extraction shows this first-order rate increase. The upper threshold is potentially linked to the onset of copper precipitation, which blinds the metal surfaces, slowing further leaching. The findings of this study suggest that in an industrial recovery operation of gold from waste PCB using the thiosulfate method, copper concentrations need to be carefully monitored, and the process should preferably operate with uncut or coarsely cut untreated boards to minimize exposure to copper circuits.

Dec 11, 2024

By S. Liaghat, J. Rosenkranz, P. Semsari Parapari, S. Chehreh Chelgani, A. Tohry

It is commonly accepted that the energy consumption for comminution within mineral processing is responsible for around 3% of the global electrical energy usage. However, it was clearly noted that inside mills, less than 1% of this energy efficiency is actually consumed for particle size reduction. Therefore, monitoring of grinding parameters and modelling of product particle size distribution (e.g. characterised by the 80% passing size P80) play an essential role in operating costs of a mineral processing plant. Several empirical models have been introduced for the prediction of the P80. Since in the industrial scale usually a few numbers of grinding variables are monitored, these models cannot identically be used in plants. In addition, these empirical models do not always indicate the magnitude of correlations between milling variables. This study proposes to introduce the Hilbert-Schmidt independence criterion (HSIC) as an intelligent model for exploring linear and nonlinear relationships between grinding variables and P80 for an industrial scale data assessment. HSIC can rank variables based on their importance and help to select the most effective one for the generation of predictive models. HSIC modelling through various monitored grinding variables (ball charge, feed input rate, F80, power draw and work index) of an industrial plant indicated that F80 as a feed property has the highest effect on P80 of the ball mill products. Modelling results highlighted that the P80 can be accurately predicted, based on effective variables by using a HSIC model. These outcomes showed that HSIC as a powerful modelling tool can assess the relationships between monitored grinding parameters, select the most effective grinding parameters and satisfactorily predict the P80. Keywords: Product particle size, variable importance measurement, Hilbert-Schmidt independence criterion, mill charge

Jan 1, 2020

By P. Mbele

Iron ore concentrate is not easily transported to, or processed in, ironmaking plants, therefore it is necessary to agglomerate. This paper will determine the possibility of agglomerating Sishen concentrate into suitable ironmaking feedstock. Pelletizing is one of the conventional and preferred agglomeration processes for iron ore concentrate investigated at Kumba Value-In-Use Laboratories. Sishen concentrate was mixed with binder, and then pelletized using a laboratory pelletizing disc; afterwards the green pellets were indurated at high temperatures to give strength high enough to survive handling and lessen disintegration in the shaft during ironmaking. Sishen pellets have satisfactory physical and metallurgical properties which make them suitable feedstock for the direct reduction processes. These were tested under Midrex shaft operational conditions and performed well, with a metallization of 94.47% being attained.

Jan 1, 2012

By M. Moseki

Paper written on project work carried out in partial fulfilment of B.Sc. (Eng.) (Metallurgy of Materials) degree This paper presents the research into melting of scrap for job creation purposes in rural areas. The research was done on behalf of Mine Recycling Services (MRS), the company that will implement the project. The project involves the research into available cost effective and easy to operate technology. The paper covers the experimental and theoretical work that was conducted. The results were used to determine the best equipment and method for melting and casting brass scrap.

Jan 1, 2002

By E. Bakhtavar, R. Mikaeil, D. Khademi

"Fuzzy-weighted integer goal programming has been developed and used to select the most suitable site to construct a central processing plant for several adjacent small-scale dimension stone quarries, based on the most effective criteria. In the first step of mathematical modelling, the most important goals and decision variables were defined. Accordingly, an objective function was used in the model for minimizing the sum of undesired fuzzy-weighted deviations. Fuzzy weights were determined by a matrix of pairwise comparisons of various expert judgments in this field and the fuzzy geometric mean. The goal and systemic constraints were also modelled. The most suitable site for the construction of the plant was selected after solving the mathematical model in the ExcelR Solver add-in. The selected site had various advantages over the other sites, such as the shortest average distance to the quarries, the shortest distance to power access and workforce, and the lowest land price. IntroductionSelection of the most suitable site of a plant is one of the most important considerations when constructing an industrial project. A suitable site has a significant effect on a company's competitiveness in the market. Selecting a desirable location for constructing plants such as mineral processing facilities is an essential part of the economic planning that will enable a company to meet the needs of related upstream and downstream operations. These units are considered to be best built near the relevant mining sites because of technical difficulties, the cost of transporting minerals, and the traffic hazard caused by the movement of trucks transporting materials. Two main types of research using multiattribute decision-making models have been reported for selection of a processing plant site (Safari et al. 2010, 2012). In that research, the analytic hierarchy process (AHP) and fuzzy technique for order preference by similarity to ideal solution (TOPSIS) approach were applied to select the suitable locations for the mineral processing plants for phases 1 and 2 of Sangan iron ore mine."

Jan 1, 2017

By J. Petersen, S. W. Robertson

Heap leaching is used extensively for the processing of low-grade copper, gold, and uranium ores. The hydrodynamics is often the most important factor that limits the rate of metal recovery. Over the past decades the author has performed physical and hydraulic testing of a large number of ore samples considered for heap leaching. The data were reviewed to investigate the effect of physical properties such as particle size distribution (PSD) and bulk density on the hydrology. The unsaturated flow through the bed is traditionally modelled with soil science models such as Brooks-Corey (BC) and Van Genuchten-Mualem (VGM), which relate the hydraulic conductivity to the degree of saturation, also known as the hydraulic conductivity function (HCF). However, most authors found a disconnect between the saturated hydraulic conductivity (KS) and the rest of the HCF, which is explained as resulting from a transition from capillary-to gravity-controlled flow. However, the author found no such transition, and found the flow to be governed by capillary flow throughout. Traditional BC or VGM fits were found to be appropriate, however it was necessary to modify the model to include a point of inflection, above which the hydraulic conductivity remains constant while the moisture content keeps on increasing. It was proposed that this is the result of unconnected or poorly connected pores, which fill with solution but do not create additional flow channels. The point of discontinuity was also found to correspond with the air entry point, measured independently from the air conductivity curves. On average, the air entry point corresponds to the experiential rule that the void saturation should remain below 65% for aerated heaps.

Dec 11, 2024

By S. Krishnannair

Singular Spectrum Analysis (SSA) is an effective data-adaptive multimodal tool for monitoring chemical processes. However, monitoring multiscale signals using principal component analysis obtained from the multilevel decomposition of process signals using basic SSA assume the upper control limits of monitoring charts (" ) to have a Gaussian distribution. This assumption deteriorates the performance of basic SSA when applied to the monitoring of nonlinear processes. To address the issue in this paper, the kernel density estimation (KDE) was used to estimate upper control limits of monitoring charts for basic SSA based nonlinear process monitoring techniques. The monitoring performance of the resulting basic SSA-KDE approach was then compared with a basic SSA approach of which upper control limits of the monitoring charts were determined based on a Gaussian distribution. Application on nonlinear dynamic simulated process and base metal flotation plant chemical processes showed that the SSA-KDE approach provided better overall performance than the SSA approach with Gaussian assumption-based upper control limits for its monitoring charts. Keywords: Fault detection, singular value decomposition, singular spectrum analysis, kernel density estimation

Jan 1, 2020

By J. A. Sweet, T. BACHMANN, G. E. Sandoval, T. M. Hauyon, F. A. Contreras

In many respects a porphyry copper ore concentrator plant can be considered as a simple system. Chalcopyrite typically liberates well at relatively coarse sizes, and even low grade ores are amenable to upgrading 20 to 30 times to produce concentrate grades in excess of 25 % in very simple Rougher- Regrind-Cleaner+Scavenger flotation circuits. The flotation response of chalcopyrite has been well characterised in many fundamental and applied research studies and the conditions necessary to depress pyrite and other floating gangue species are well understood. But what happens to the particle surfaces when you have a 50 km pipeline between the grinding circuit and the flotation plant? How does the seasonal variation in water quality affect your ability to control pulp chemistry? What impact does the relative concentration of the different sulphide species have on their separability? Why do two plants that receive nominally the same ore produce consistently different results? And most importantly, what do you need to do to improve the performance of both plants? To answer these and other questions, a focussed sampling and analysis programme was carried out at the Las Tórtolas flotation plants in 2018 and 2019. The work included full down-the-bank sampling, hot floats, the use of radioactive tracers for determining residence time distribution profiles, gas dispersion measurements, detailed mineralogy by size across the circuits and multiple regrind surveys. This comprehensive study was augmented by analysis of historical mineralogy, geometallurgy and operating data using modern data science techniques, and has provided the foundation for current and future optimisation initiatives. Some of the findings and their implementation will be presented in this paper. Keywords: Circuit optimization, Residence time, Gas dispersion, Pulp chemistry

Jan 1, 2020

By C. E. More

Some observations on 'ancient' mining at Phalaborwa C. E. MORE. B.A. (Pretoria) (Visitor) A brief account is given of historical references to the Phalaborwa area, the first being to the mountain of copper and iron sought by Francois de Cuiper in 1725. These are followed by a description of several finds in the area, which are related to finds described in the literature and to Bantu tradition on the subject. Phalaborwa is one of the earliest known mining sites in the Republic of South Africa, Loolekop having been a mining centre, as shown by carbon-14 dating, since 770 A.D.

Jan 1, 1974

By M. Sanchez, I. Imris, G. Achurra

The Smelting and Converting El Teniente Process for copper concentrates as well as Slag Cleaning Furnace Technologies to treat slags coming out from the El Teniente Furnaces are widely applied today in Chile and around the world. Several industrial applications of this process have shown their capability to treat copper concentrates in a wide range of chemical and mineralogical compositions. Main operational parameters determining performance of the process are: oxygen enriched air flow rate, degree of oxygen enrichment, moisture content of the solid materials processed, molten material levels inside the vessel, frequency of molten materials tapping, bath temperature and copper losses in slags. In this work, the copper losses in the slags from El Teniente pyrometallurgical process are predicted by calculation from thermodynamic data and compared with those determined by microscopic examination and slag industrial data. Results obtained show that the main part of copper losses in the slag from El Teniente Furnace are mechanically entrapped or floated unsettled droplets of the coexisting matte phase. by the contrary the very low copper losses in the slag from slag cleaning furnace are limited by the physico-chemical form.

Jan 1, 2004

By A. D. Pelton

The evolution of thermodynamic models of molten salts and slags, starting with Temkin in 1948, has culminated in today?s sublattice models. These modern models have permitted the development of large thermodynamic databases of model parameters, which can be used to calculate and predict accurately the properties of multicomponent solutions. The model parameters are mainly obtained by the critical evaluation and optimization of available thermodynamic and phase equilibrium data for binary and ternary subsystems. The models are then used to estimate the properties of multi component slags and salts from these assessed binary and ternary parameters. When used in conjunction with thermodynamic databases for solids and solid solutions (salts, oxides, sulphides, metals, etc.), other liquid solutions (such as liquid metals),and gases, these databases permit the calculation of complex multiphase equilibria in multicomponent systems, with applications in a wide variety of industries. These calculations can be performed with general commercial software for Gibbs energy minimization, which can also be incorporated into process simulation software packages. Keywords: slags, salts, solution models, thermodynamics, phase diagrams, oxide systems, molten salts

Jan 1, 2004

Bacterial leaching represents an unusual problem in biochemical engineering, because the substrate for bacterial growth is not supplied directly, but is a product of another reaction, the leaching of mineral particles. Leaching arises from the bacterial oxidation of ferrous ions to ferric ions, which in turn oxidize the mineral. For the bacterial dissolution of pyrite, these reactions are: [ ] (Y represents a stoichiometric yield factor, and N represents the amount of bacteria.) Equations [1] and [2] represent a cyclic auto-catalytic system since more ferric ions are added to the system with an increase in the extent of leaching.

Jan 1, 2000

By D. W. Dew

Billiton Process Research has carried out extensive research over the past four years to develop new process technology using bioleaching for extraction of copper and nickel from their sulphide concentrates. Continuous pilot scale and laboratory batch testwork has been carried out with adapted mesophile bacterial cultures at40°C?45°C, moderate thermophile cultures at 50°C?55°C and thermophile cultures at 65°C?85°C. Pilot scale work has demonstrated the commercial viability of mesophile cultures for bioleaching of secondary copper sulphide and nickel sulphide concentrates. Moderate thermophiles offer benefits in terms of reduced cooling requirements for commercial reactors and, in the case of bioleaching of nickel concentrates, some selectivity over bioleaching of pyrite. Continuous pilot scale testwork has shown that thermophiles achieve efficient bioleaching of primary copper sulphide and nickel sulphide concentrates, giving much higher recoveries than achieved by bioleaching with a mesophile or moderate thermophile culture.

Jan 1, 2000

By Jo Katembo, Patty Bwando, Patient K. Ilunga, Yves Kalubi, Emman Mulaj

"From 2010, the dolomite concentration in the ore fed to the Usoke Plant increased, resulting in a significant increase in the gangue acid consumption and Mg build-up in the circuit, and thus an increase in the Mg:Co ratio in the plant solutions. This affected the Co salt grade, reagent consumption, filtration and drying capacity. Efforts were put in place to minimise the acid consumption and consequently the Mg dissolution (such as use of pre-diluted acid), but the benefits were negligible. Various efforts were then initiated by CHEMAF to improve the cobalt plant productivity (quantity and quality) by process changes, dual precipitation and seed recycle. The positive results obtained in the laboratory were successfully implemented on plant scale. A change in the process from a single-stage precipitation with Na2CO3 to dual precipitation using a combination of Na2CO3 and NaOH improved the capacity of the Co salt filtration by 30%, the Co salt grade and drying capacity by 50%, and reduced the reagent consumption by 22%. Implementation of precipitate seed recycle increased Mg rejection by 40%, improving the Co salt grade from 20% to 25%, and yielding a further drop in reagent consumption. INTRODUCTION CHEMAF (Chemicals of Africa), a mining company located in Katanga province of Democratic Republic of Congo (DRC), has been operating since 2003. The Usoke hydrometallurgical plant treats the Cu-Co ore from the Etoile pit to produce Cu cathodes via a leach–solvent-extraction (SX)–electrowinning (EW) circuit and Co salt via a selective precipitation process. The plant was designed to treat run-of-mine (ROM) ore grading 6% Cu and 1.5% Co; but, in 2008, due to a decline in grades, a heavy-media separation (HMS) plant was commissioned to enrich the low-grade ROM (3.5% Cu and 0.5% Co) up to 8% Cu and 1% Co before feeding it to the hydrometallurgical plant. Co is recovered by precipitation of Fe and Al with limestone, followed by Co precipitation as Co carbonate using sodium carbonate (Na2CO3), also known as soda ash. 85% of the final effluent from cobalt precipitation is recycled back to the plant as process water; the balance, 15%, is bled out and compensated for by fresh water top up to control and retard the rate of sodium sulfate build up."

Jan 1, 2015

The Modified Zincex® Process, developed by Técnicas Reunidas, is highly flexible dealing with a wide range of pregnant leach solutions. No matter if those solutions are produced from primary or secondary raw materials, and/or are based on conventional leaching, pressure leaching, heap leaching or bio leaching the result is always high-purity zinc product. The zinc solvent extraction unit within the process is a very effective barrier for impurities and a buffer for the composition of the pregnant liquor. This unit achieves an extremely pure aqueous extract that can be converted into different final products. All of them are characterized by fulfilling the highest purity standards. Also, there is the possibility to adapt the global process to a wide range of pregnant liquor compositions and various production capacities up to a zinc production limit over 150 000 t/a with a single solvent extraction plant.

Jan 1, 2002

By T. Grewar

"South Africa is a water-scarce country, rated as one of the 30 driest countries in the world. Worryingly, government expects water demand to outstrip supply as early as 2025. The South African government believes that substantial volumes of water can be made available through the reuse of treated mining-impacted water. Currently, however, large volumes of treated mining-impacted water are produced, often with no end use in mind other than discharge or disposal, when these treated effluents may have further uses in applications which are currently and unnecessarily using high-quality water. Treating the wastewaters to levels that meet ’fitness-for-use’ guidelines for alternative applications such as agriculture, sanitation, or industrial processes will reduce the treatment cost burden compared to potable water production. The primary conclusion of this review is that the most suitable option for re-using treated mine-impacted water is in agriculture, for irrigation of crops (food, forage, or energy crops), which currently and unnecessarily makes use of the majority of South Africa’s high-quality resources or potable water. Other findings include the realization that although guidelines and legislation for water re-use in South Africa exist and are readily available, they tend to be contradictory and confusing in many cases. It is imperative that these ambiguities and incongruities in the available guidelines and legislation for water re-use be clarified and updated swiftly IntroductionSouth Africa is a water-scarce country and is currently rated as one of the 30 driest countries in the world, with an average rainfall of 490 mm/a, approximately half of the global average. As an indicator of the degree of regional variability in South Africa’s water supply, it has been shown that 70% of all runoff is from approximately 20% of the land area. Regardless of the water scarcity faced in South Africa, our water conservation track record is poor, with an average consumption of 280 L/d per person, almost 60% more than the global average of 175 L/d per person. Around 40% of this allocation is utilized in watering lawns and gardens (Zhuwakinyu, 2017).The South African government predicts water demand to outstrip supply as early as 2025. On an international scale, the situation appears just as dire, with the United Nations High Level Panel on Water (HLPW) expecting a 40% water shortfall by 2030, which may affect up to 1.8 billion people based on current water demand trajectories (Zhuwakinyu, 2017)."

Mar 1, 2019

By R A. Lynch, D A. Malovichko

The implementation of routine real-time micro-seismic monitoring of open pit mine slopes has been discussed. Some examples of seismic arrays have been given, and a recommendation of suitable seismic sensors made. Unfortunately near-surface sensors are required for good location accuracy, and the effects of reflection, mode conversion and surface waves must be accepted and compensated for during processing of the seismograms. It makes sense that mining at the base of a slope and levels of seismic activity within the slope should be related, and this is confirmed using both 2002-2003 and 2005 seismic data recorded at Navachab mine. An example of how seismic data can be used to gain information about seismically active geological structures has been described. The removal of broken rock, and not blasting nor the breaking of supporting rock, has been found to cause slope micro-seismicity. While the standard Brune source model is suitable for some 20% of the seismic events, unreasonable results are obtained for the rest. A moment tensor inversion has been performed after S-wave splitting and surface effects have been filtered out. This approach confirms a predominantly shear mechanism for a typical high frequency source.

Jan 1, 2006

By M. B. Shongwe

Pt-based alloys are being developed for high-temperature applications with the aim of replacing some of the currently used Ni-based superalloys (NBSAs) in the highest temperature applications. The Pt-based alloys have a similar structure to the NBSAs, and since Pt is more chemically inert than nickel and has a higher melting point, they can potentially be used at higher temperatures, up to 1300°C, and in more aggressive environments. Several experimental Pt-based alloys were studied at Mintek, and an optimum composition was found to be Pt84:Ahi:Ru2:Cr3 (at.%). On the basis of hardness and microstructure, a later study identified a new optimum: Ptr8:A111:Ru5:Cr6 (at.%). There are at least two Pt3A1 allotropes, and the high-temperature cubic structure has better properties than the lower temperature tetragonal form, and so needs to be stabilized. This work describes the latest results obtained in transmission electron microscopy (TEM) studies of the quaternary Pt-based superalloys. These results are both interesting and important, because the samples have a higher precipitate density compared to those from earlier work. The precipitate morphology is mainly cubic, with minor areas having irregular-shaped precipitates. The high volume fraction of the precipitates is a major breakthrough, since the objective of this work is to improve the alloys. A prior disadvantage was that the proportion of the precipitates was too low in samples before this work, especially compared with the work from Germany on Pt-Al-Cr-Ni¬-based alloys as well as the NBSAs. TEM -Pt3A1 diffraction patterns were studied, and for each diffraction pattern, many possible lattice point combinations were tried, with the angle between the lattice spots as well as interplanar spacings being calculated for each phase (cubic or tetragonal) to match the measured results. An overall analysis of the diffraction results indicates that the cubic phase fitted the experimental lattice points with much lower errors compared to the tetragonal phase. Thus, with the close match achieved with the cubic structure, the structure of -Pt3A1 precipitates is likely to be cubic. X-ray diffraction has been carried out on selected samples, and the results confirmed the presence of cubic -Pt3A1 and (Pt). Different X¬ray diffractometers were used to further verify the results, and the results were also compared with those from TEM.

Jan 1, 2012

By K. Muchima, C. Siame, L. Little, B. Kaputula, Q. Mclennan

"The variability of copper mineralization at Kansanshi mine significantly affects the efficiencies of the processes used to recover copper. Quantifying this variability is therefore essential for monitoring and optimizing the performance of the concentrator, which comprises three different flotation circuits (sulphide, mixed, and oxide) and an atmospheric leach circuit. Onsite automated scanning electron microscopy with energy-dispersive X-ray spectrometry (Auto-SEM-EDS) is used to analyse routine weekly composite samples for each circuit, providing detailed analyses of bulk mineralogy, copper deportment to different minerals, mineral liberation, and associations. Weekly mineralogical trends are used to assess changes in process performance, and characterization of the copper losses has inspired a number of projects to target the specific particle types responsible for the main losses. In this paper we describe the relationship between mineralogy and plant performance at Kansanshi, and discus IntroductionKansanshi is a copper and gold mine located in the Northwestern Province of Zambia, with an annual production in the region of 250 000 t of copper and 160 000 ounces of gold. Ore mined from the epigenetic vein-hosted deposit is classified into three ore types based on the extent of oxidation and supergene enrichment. Sulphide, oxide, and mixed ore are fed to separate mineral processing circuits tailored for recovery of the dominant copper minerals in each. After comminution to a target grind size of 80% passing 150 µm, each ore type is subjected to flotation to recover the copper sulphide minerals (chalcopyrite, bornite, chalcocite, covellite). The oxide float tails and a large proportion of the mixed float tails are then treated by atmospheric leaching to extract copper from the remaining copper-hosting minerals, which include cuprite, malachite, chrysocolla, and delafossite. Some native copper is recovered by flotation and some of it is recovered by leaching. A small portion of the combined concentrate from all circuits is subjected to high-pressure leaching and the rest is sent to the smelter. Sulphuric acid produced during smelting is used for the atmospheric leach."

Nov 1, 2018

By A. V. Rasskazova

Theoretical substantiation of leaching of clustered ultra-fine gold by the electro-photo activated cyanide and chloride solutions is given in the paper; and processes of activation of leach solution by electrolysis and photo-activation are described. Comparative experiments on electro-photo activated leaching of ultra-fine gold from refractory ores by cyanide and chloride solutions were carried out. The material for research is primary ore of the Pogromnoe deposit (Russian Federation, Trans-Baikal Territory). The ore is characterised by the minimum sulfide minerals and the organic carbon content. Gold in ores of this deposit is presented as mainly ultra-fine. Gold inclusions in quartz and silica-alumina minerals (metasomatic minerals) are ultra-fine. Sulfide minerals (2.5-3%) are presented in ore generally by pyrrhotine (gold content does not exceed 10 g/t). Standard cyanide technology provides 49.5% gold recovery. Photo-electro activated air saturated NaCN provides 69.9% gold recovery. Laboratory research of chloride-hypochlorite column leaching demonstrated that the electro-photo activated method provided 78.9 % gold recovery to pregnant leach solution. Chloride-hypochlorite photo-electro activated solution can provide higher level of gold recovery with shorter process duration (10 days) in comparison with cyanide (40 days). The final decision regarding the choice of leach solution has to be done on the basis of technical and economic calculations. Keywords: Ultra-fine gold, cluster chemical reactions, active clusters, leaching, electro-photo activation of leach solution

Jan 1, 2020