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By M. Kanuchová, J. Briancin, M. Achimovicová

"Faculty of Mining, Ecology, Process Control and Geotechnology, Technical University, Košice, Slovakia An industrial eccentric vibratory mill was used for direct and short-time mechanochemical reduction of ilmenite concentrate (FeTiO3) and anatase (TiO2) with magnesium metal powder in order to reduce Fe and Ti resp. and hereby to convert them to the more soluble phases suitable for further hydrometallurgical processing. X-ray diffraction analysis of FeTiO3 after 60 min of milling with Mg confirmed the presence of Fe0 and Mg2TiO4 phases and for TiO2 after 180 min of milling the new TiO and MgO phases have appeared. X-ray photoelectron spectroscopy has detected Fe0 (metal) and Mg2+ species which are corresponding to the product of FeTiO3 mechanochemical reduction. The product of TiO2 mechanochemical reduction has revealed XPS spectral lines corresponding to Ti2+, Ti4+ and Mg2+ species on its surface. Morphology of mechanochemically reduced samples was studied by scanning electron microscopy analysis. Subsequent leaching of mechanochemically reduced FeTiO3 and TiO2 was performed in dilute HCl and H2SO4 at 80oC and compared with mechanically activated samples. The recovery of Ti has reached 100% for FeTiO3 and 79% for TiO2 after 60 min of leaching. Based on this study the flowsheet for possible processing of natural refractory titanium ores patented by author was adapted and documented. INTRODUCTION Ilmenite (FeTiO3), along with rutile (TiO2) represents the most important titanium resource necessary for titanium industry, for production of titanium metal, alloys and pigment grade TiO2 which are becoming more important and versatile for various industries such as an aircraft and aerospace, navy, chemical, automotive, medical and offshore wind industries, for machine and plant engineering and architecture as well, mainly due to high corrosion resistance. Pigment grade TiO2 is utilizing in pigment, plastic, glass, paper and rubber industries (Zhang, 2011). There are obvious research efforts for development of the potential alternatives to the expensive thermo-chemical commercial processes of titanium raw materials processing. Zhang (2011) has summarized conventional thermo- a electrochemical processes which involved a combination of pyrometallurgical, hydrometallurgical and electrometallurgical technologies and highlighted the improved hydrometallurgical routes promising for commercial application in the future. Such improvement could also be mechanical activation of FeTiO3, TiO2 by high-energy milling which causes their structural disordering, the changes of physical and chemical properties, consequently and has a positive effect on the dissolution kinetics (Achimovicová et al., 2014a, 2017, Baláž, 2008). The various types of mills such as a planetary ball mill, a vertical ball mill, a drum mill, an attritor were used for mechanical activation of FeTiO3 as a pretreatment process for subsequent leaching (Achimovicová et al., 2014)."

Jan 1, 2018

By Thenepalli Thriveni, Seong-Young Nam, Nam-Il Um

New modern water treatment technologies required for arsenic removal from waste waters contaminated extensively by various background sources from mining, industrial waste, agricultural waste, painting industry and natural geological bed rock system etc. Arsenic is a widely dispersed element in the earth's crust and exists at an average concentration of approximately 5 mg/kg. Arsenic (As) and heavy metals may be released from the mine wastes to the ground and surface water systems, as well as the geological environment due to their solubility and mobility. This research focuses on the effect of accelerated carbonation process for successful removal of heavy metal arsenic anions from artificial waste water and mining waste waters. This accelerated carbonation process is a simple and novel method with 85 ~ 88% removal efficiency. Carbonation has been studied as a process to further improve immobilization of solidified/stabilized waste and granular waste. After successful removal of arsenic anions from solid mining waste and its potential benefits for producing construction materials. Besides, the industrial and urban management systems are generating bulk solid mining wastes, and most often dumping them in open fields. To prevent the landfilling with mining waste, many efforts are being made for the recycling of different types of mining solid wastes with a view to utilizing them in the production of various construction materials.

Jan 1, 2014

By Shuji Owada, Shinya Suzuki, Chiharu Tokoro, Daisuke Haraguchi, Sayaka Izawa

"Coprecipitation with ferrihydrite has been one of the major treatment method for As(V) removal from wastewater such as acid mine drainage. We already confirmed coprecipitation of As(V) with ferrihydrite consists of two kinds of mechanism; one is two dimensional As(V) uptake to the surface of ferrihydrite by surface complexation and another is three dimensional As(V) uptake into ferrihydrite by surface precipitation. We also already confirmed As(V) adsorption process by ferrihydrite could be quantitatively evaluated by original surface complexation model with parameter values reported by Dzombak and Morel. However, As(V) coprecipitation process couldn’t quantitatively be represented by only the original model. In this study, construction and calculation using surface precipitation model were attempted for As(V) coprecipitation treatment with ferrihydrite. In the surface precipitation model, precipitation was described by the formation of solid compound between ferrihydrite and ferric arsenate. Activity of these precipitates was determined by surface precipitation ratio of FeAsO4(s) obtained experimentally from XANES analyses. Solubility products of surface precipitation of FeAsO4(s) (Ksp_FeAsO4(suf.)) were determined by fitting to sorption densities and surface precipitation ratio in each condition. The values of Ksp_FeAsO4(suf.) were determined 10-7.7 at pH5 and 10-10.2 at pH7, respectively. Based on the obtained Ksp_FeAsO4(suf.) value, As(V) removal and isotherm were calculated for As(V) co-precipitation treatment using surface precipitation model. Good agreement between experimental and calculated values was observed. These results were suggested that the quantitative prediction of As(V) co-precipitation treatment was possible if Ksp_FeAsO4(suf.) value was estimated experimentally."

Jan 1, 2014

By M. E. Holuszko

This paper reports the results of induction time measurements carried out on the products of film flotation of galena and sphalerite particles from three different size fractions (38~75µm; 75~150µm; 150~212µm). As expected, the tailings (sinking fraction) from film flotation at any particular surface tension, had always longer induction times than the concentrates (floating fraction), for both minerals. The difference between the induction times of film flotation concentrate and tailings could be as little as 2.5 ms and 5 ms, and as large as 6 ms and 10 ms. These differences can be related to the different hydrophobic characteristics of these fractions, as expressed by (?c) and composition of the particular film flotation product. In addition, the induction times of the larger particle size fraction were shown to be longer than for the corresponding smaller particle size fraction, even though the average ?c(degree of hydro-phobicity) of these fractions appears to be very similar. Desliming, Cu activation and collector addition to the sphalerite samples was shown to decrease the induction time values significantly.

Jan 1, 2014

By R. C. Miranda

Artificial vision systems are increasingly used to assist humans to perform different tasks in different areas. These systems are able to recognize patterns in complex images, which can provide multiple data. Currently, vision systems are used in both; monitoring traffic - which uses radars for vehicular plate recognition- as in metallurgical and food industries for strict quality inspections. Their use in mining occurs in measuring the speed of froth over the lip of a cell, in determining the shape and size of pellets, in obtaining from the tendency of mineral content and as a replacement for laboratory analysis of particle size. With this advanced tool, it is possible to achieve significant improvements in quality, productivity, and especially in reducing costs in pelletizing plant of iron ore. The objective of this paper is to contemplate the current situation of image analysis in the pelleting plants and glimpse at the potential applications that are being developed. This paper also presents the conception and implementation of an automatic control system of the pellets size distribution applied on a pelletizing plant of iron ore. The article demonstrates the strategy used for measuring the size distribution of the iron ore pellets, based on image analysis and the strategy implemented on advanced process control, which shows substantial gain on plant performance.

Sep 1, 2012

By Nilmara Dias, Maria Margarida Martins, Maria Teresa Carvalho

"The heavy residual fraction of the mechanical and biological treatment (MBT) plants treating undifferentiated municipal solid waste is mostly composed by inert materials, such as glass, stones, ceramics and brick. Glass, appearing in significant grade and amount, is not recycled today due to the high content in the other materials, mainly stones. All these materials have approximately the same density but stones have significantly different shape from other materials particles. In this paper it is presented the research developed to eliminate stones appearing in the fine fraction (2.8-8 mm) of the MBT plants heavy residual fraction (MBTr) using a shaking table operated in dry conditions. Two different samples from two different MBT plants were used. Firstly, the samples were characterized (materials content and particle size analysis). Then, laboratory work was carried out to optimize the operation of the shaking table, by changing the machine parameters, deck slope and movement frequency. The study showed that it is possible to upgrade the product in glass. The best results, obtained with one single stage of processing, were 82% content in glass with 84% in recovery, in the glass concentrate, when the coarser fraction (-8+5.6 mm) of one of the MBT plants was used. With the intermediate particle size fraction (-5.6 + 4mm), the glass concentrate attained 74% content in glass with 91% recovery."

Jan 1, 2014

By T. N. Matveeva, T. A. Ivanova

"The article presents the results of the research aimed at development and testing of new effective reagents – collectors and green modifiers for more complete extraction of gold and platinum to concentrates at reduced loss with waste products. The main deposits of Au and PGM ores of Russia and abroad are presented by refractory raw material with the non-uniform finely-interspersed sulfide mineralization, submicron gold and platinum, the low metal content, non-uniform distribution of valuable minerals. and show low indicators of recovery. The main losses of precious metals (up to 15 %) at flotation are associated with thin slam tailings because of inefficiency of standard reagent modes.In the paper, the new trends in design of collecting agents for extraction of gold and PGM sulfide minerals and their application in flotation tests are substantiated. The original technique for obtaining the modified collector reagents – dithiocarbamate, dithiophoshpinate and dithiazine, incorporated non-ionic compounds that are able to generate stable complexes with gold and platinum has been developed. A novel class of collectors – cloud point polymers showed high flotation recovery of fine particles of gold and platinum. The original technique to create the mineral samples of natural sulfides with ""invisible"" or sub-micron gold on their surface designed helped to indicate the mechanism of selective adsorption of novel agents on Au and Pt-sulfide minerals. Extractive UV spectrophotometry, potential measurements, X-ray phase and spectral analysis, scanning electronic microscopy (SEAM), laser SIM and AFM microscopy were applied to analyze the adsorbed layer of modified reagents on the mineral surface. Selective hydrophobic covering on the surface of micro- and nanoparticles of noble metals provided an increase in their extraction during flotation. New reagent modes of modified collectors and green modifiers were tested in scaled-up laboratory flotation and the results obtained demonstrated the increased quality of the concentrates in terms of gold content by 1.5 times and higher gold recovery by 1.5-5%. The studies have been supported by Grants of the President of RF “Scientific School of Academician Chanturiya” NSh-220.2012.5; NSh-748.2014.5."

Jan 1, 2018

By S. Gaydardzhiev

Initial experiments towards preparation of hollow ceramic microtubes by dip-coating of fibrous plants with water based alumina gel-casting slurries using hemp and coconut fibres as templates have been done. It has been found that the wettability of fibres and accordingly the stability of the developed ceramic layer on their surface during slurry gelation varied significantly within the different fibre types. Good correlation between the diameters of the template fibres and the resulting channels has been found at the level of solids loadings used, 31 %. Hemp fibres used as bundles have led to formation of multi channel patterns while the coconut fibres-templated process resulted in uniform monochannel materials. The micro tubes have show good mechanical handling.

Jan 1, 2014

By V. Tsyplakov

This article reviews factors of preg-robbing effect, occurring in the course of pressure oxidation of ore and concentrates, containing chloride compounds and so-called 'organic carbon'. The article also summarizes the main results of the studies and testwork conducted to overcome this effect. The following efficient preg-robbing mitigation methods have been noted: higher temperature of pressure oxidation process, preliminary removal of natural carbonaceous material from concentrate, chloride removal prior to concentrate pressure oxidation, and addition of water-soluble organic blanking agents, which suppress the adsorption activity of the native ore adsorbents. Keywords: preg-robbing, double-refractory gold concentrates, pyrite, arsenopyrite, blanking agents, pressure oxidation, autoclave leaching

Sep 1, 2012

By Dave Deglon

The Western Cape Mineral Processing Facility (WCMPF) is a collaborative educational initiative between the Departments of Chemical Engineering of the University of Cape Town, the University of Stellenbosch and the Cape Technikon. The WCMPF was established in 1989 with the aim of improving mineral processing education in the Western Cape. Since its inception the WCMPF has had a number of successes in this area, especially in improving the quality of mineral processing practical training. In addition, the WCMPF has played an important role in promoting liaison and interaction between tertiary educational institutions teaching mineral processing in the Western Cape. Over the past decade the WCMPF has played a key role in the education of over five hundred mineral processing graduates and diplomates. This paper presents an overview of the activities of the WCMPF and attempts to encapsulate the ‘lessons learned’ from over a decade of successful functioning as a collaborative educational initiative in mineral processing.

Jan 1, 2003

By A. Singh, M. Ntlhane, V. Ross, M. Dlame

"Fine valuable particles are often lost to flotation tailings streams due to inefficient collection by air bubbles as well as passivation of surfaces by oxidation and slimes. The application of high-shear hydrodynamic cavitation devices (HCDs) to overcome this problem has already proven to be a considerable success in the industry. This paper details the results of further investigations that were undertaken at Mintek to better understand the mechanisms involved when preconditioning feed slurries in an HCD. By promoting inter-particle attrition and conditions of high shear within the reactor, cleaning of particle surfaces is enhanced as well as the formation of superfine (nano) bubbles which are believed to aid their agglomeration and subsequent collection by normal sized bubbles. In order to broaden the envelope of understanding with regard to application of the technology, rather than tailings material as investigated earlier, a Platinum Group Mineral (PGM) UG2 ore from the Bushveld Complex in South Africa was used in this study. The results of a series of batch flotation tests in a 10L Denver cell are presented, being conducted after the feed has been subjected to different methods of preconditioning. It was demonstrated that the preconditioning significantly improved the flotation kinetics of the PGMs, the optimum being obtained after around 20 passes through the reactor. This was accompanied by a much enhanced recovery-mass pull relationship and a significant improvement in the grade-recovery response. Significantly, the selectivity between the PGM and the deleterious chromite (expressed as Cr2O3) gangue more than doubled under these conditions. Modelling of the PGM data by means of the modified Kelsall model indicated that both the fast and slow floating rate constants were improved.INTRODUCTIONIt is well known that the flotation recovery of fine and ultrafine particles, typically less than 10 micron in size, is a challenge (Yoon et al., 1989; Miettenin et al., 2010). Although these particles are typically well liberated, due to their very low mass and inertia, the collision efficiency with air bubbles is low as a result of the inability of particles to penetrate the liquid streamlines around bubbles. Hence the probability of contact is often regarded as the ratedetermining step in flotation of ultrafine particles. Introducing more power into conventional flotation machines is likely to solve only part of the problem, as conventional mechanisms are effective only to a point in terms of shear and micro-turbulence. Further challenges are posed by the treatment of low-grade or oxidised tailings dump material, where valuables are passivated due to prolonged exposure to the atmosphere or slimes. Over the years, various mitigating strategies have been investigated, including the use of dissolved air flotation (Martinez-Gomez et al., 2013; Calgaroto et al., 2015), shear flocculation (Subrahmanyam and Forssberg, 1990), seed or carrier flotation (Tabosa and Rubio, 2010), sonication to clean particle surfaces (Aldrich and Feng, 1999; Newell et al., 2006), high intensity conditioning (Bulatovic and Salter, 1989; Chen et al., 1999; Tabosa and Rubio, 2010), and various electrochemical approaches such as changing Eh in order to promote formation of dixanthogen, dissolution of oxidation products by lowering the pH, activation by sulphidisation (Newell et al., 2006; Becker et al., 2014), and the use of alternative collectors."

Jan 1, 2018

By Philippe De Donato, Odile Barres, Mukendi Kongolo, Stoyan Gaydardzhiev, David Bastin, Jean-Marie Kanda

The adsorption patterns of potassium amylxanthate on the surface of high purity malachite subjected to prior sulfidization with NaSH have been followed and elucidated. DRIFTS spectroscopy has been used to trace the associated physicochemical alterations as well as the chemical species present on the mineral surface. Varying the collector concentration from 5.10-4 to 1.10-2 mol/L has led to different degree of surface coverage of the alkyl groups and to formation of organometallic hydrophobic complexes of CuX or CuX - X2 type. The results reveal that the CuX complex formed on the malachite surface without sulfidizing agent is more unstable and prone to dissolution-precipitation phenomena. Based upon the constructed adsorption isotherms and upon the degree of statistical coverage, different zones of mineral-reagent interactions could be distinguished. They correspond respectively to the monolayer, bi-layer and tridimensional condensation domains. In each of the identified zones mono or double layer adsorption patterns of the collector are proposed leading respectively to formation of surface compounds with different degree of hydrophobicity. The results suggest that sulfidisation remains an important prerequisite in view achieving efficient flotation of the malachite from the studied copper ore.

Jan 1, 2014

By Hong Nguen Vu, Pavla Ovcarí, Peter Fecko, Barbara Tora

The aim of this paper is to evaluate the suitability of a coal sample from the mine Jaworzno (Poland)- locality for bacterial leaching. Laboratory research used a pure bacterial culture of Thiobacillus ferrooxidans. The results showed that bacterial leaching was effective, with a one month leaching time, when 65% of total sulphur and 85% of pyritic sulphur was leached. The paper describes changes to the pyrite during and after bacterial leaching.

Jan 1, 2003

By André Mans, Frans B. Waanders

Current losses of Ferrosilicon (Fe-Si), which is used in the dense medium separation (DMS) of iron ore at Kumba Resources, Sishen, South Africa occur due to adhesion to the separation products and also by being present in the effluent stream, due to abrasion. The losses contribute greatly to the running cost of the plant and the purpose of this project was to determine the characteristics of the unused Fe-Si and then to characterise the changes that occur during storage and the use thereof. A Scanning Electron Microscope (SEM) and Mössbauer Spectroscopy (MS) were used to investigate the characteristics of the fresh and used Fe-Si. It was found that the biggest loss of Fe-Si was due to the abrasion of the particles during the DMS process, which resulted in the liberation of Fe and subsequent formation of an oxihydroxide froth. A possible change in magnetic properties was also observed, leading to further losses that could occur during prolonged use of the medium. No clear changes to the Fe-Si occurred during correct storage methods, as was initially thought.

Jan 1, 2003

By L. Burdukova

"In flotation, depressants are used to reduce the amount of gangue that reports to the concentrate and hence increase the selectivity of the flotation process. At the University of Cape Town extensive batch flotation tests are carried out to evaluate industrial depressants and standard procedures have been developed over the years.This study was conducted in order to develop an improved method for comparing depressants using machine vision as an aid. The modified method of batch flotation involved a test with prolonged intervals between scraping to allow more time for the froth to build up and mature.This method of testing showed increased differences between the flotation performance obtained as represented by grade recovery curves for carboxymethyl cellulose and guar depressants when compared to the standard method of testing with shorter scraping intervals. The improvement was attributed to reduced entrainment resulting from longer drainage time in the froth and therefore yielded a better test for comparing depressants on the basis of true gangue flotation with minimized entrainment. As expected, the sulphide recoveries were unaffected by the change in method. The machine vision system also added to the information obtained during these tests by recording bubble size trends throughout the tests which were later analyzed and related to the amount of flotable gangue in the froth. Modifications are recommended to improve the usefulness of machine vision in batch flotation."

Jan 1, 2003

By W. Pawlos

"The paper will present the methods of visual observation and recording of movement paths of coal grains of different physical properties in the paramagnetic liquid. The paths were recorded with a video camera in the working chamber by means of a specially constructed device, acting as a periscope, which were then transformed into digital images.Experimental movement paths were confronted to the paths obtained in a theoretical way by means of solving differential equations of movement. The outlet level of a grain of the same physical properties from the separator is a random variable with normal distribution which modal value is equal to the outlet level of a spherical grain, calculated from the solution of grain movement equations. At these assumptions it is possible to calculate the height of the passage from the separator working chamber to separate a given product with a given separation accuracy, measured by a probable error and to determine separation conditions."

Jan 1, 2003

By James A. Finch

"Developed countries are in the midst of re-structuring education in minerals-related disciplines as raw materials, once vital to wealth generation, contribute progressively less to the economy. The changing circumstances mean institutions must justify mineral processing by new criteria. After considering what a mineral processor needs to know the ways to deliver are considered. Taking twenty graduates per year to illustrate, one institute could justify this number as a program in a department or school (of whatever grouping of disciplines). A strong research component would make the package additionally attractive. Divide among four institutions and mineral processing is best served in a research centre with delivery taking advantage of multi-centre and distance learning opportunities.INTRODUCTIONThis is one of five plenary lectures at the Congress. I may have preferred a technical subject, as that is what occupies most of my thinking hours, but it is reasonable as an academic that this topic should come to one of us. The fact the topic has not been high on my agenda may provide one advantage: that I can suggest directions free of pre-conceived notions, just as when reviewing the background to a technical article the temptation to select in support of one?s interpretations is resisted. The trick will be to add something new.One reading of the title seems to query whether mineral processing education has a future. (I will refrain at this juncture from defining mineral processing and assume for now we share an understanding of the term.) The proximity of natural and human resources led to the Industrial Revolution and the interaction continues to stimulate and sustain industrial and economic development in many parts of the world. The search for raw materials has historically played a key role in opening frontier areas, with undersea and outer space next. The reason is obvious: raw materials along with food and energy underpin society. Thus mining will remain part of human activity along with the need to pass on the knowledge and skills.What happens over time is resource relocation. Raw materials become exhausted in one area to be replaced by sources elsewhere; the demand for some materials lessens while growing for others. Educational institutions can find themselves with the wrong geography or with staff focussing on the wrong subjects. When this happens the restructuring produces much discussion. This is where we are in parts of the world. Japan, Western Europe and the United States are the prominent examples (Dowd, 1998; Flemings and Suresh, 2001; McDivitt, 2002). Mineral processing is becoming a series of courses in related disciplines: resource engineering, environment engineering or materials engineering. The start of the transition is evident in Canada and Australia, perhaps earlier than expected given the contribution of raw materials to their economies. A common backdrop in the developed countries is social pressure to reduce the impact of the ?untidy? aspects of life, and that includes mining. (This is not new: in classical times the mine face was the preserve of slaves and convicts.) These values are exportable, potentially affecting recruitment into mining schools everywhere."

Jan 1, 2003

High flotation of iron sulfide minerals at high pH values in copper ores is mainly due to the activation of these minerals by copper species dissolved from copper sulfide minerals during grinding. Several methods have been tested to reduce this copper activation during grinding and therefore to depress iron sulfide flotation. They include grinding the minerals at high pH values or with a less reactive medium such as high chrome, and addition of a thiol collector or copper complexant during grinding. The efficacy of these methods in the flotation of a copper ore was tested against more common methods of depression of iron sulfide flotation. The mechanism of iron sulfide depression in these methods was also investigated.

Jan 1, 2014

By Gerke Gilian, Pretz Thomas, Pehlken Alexandra

"The evaluation of health hazards within the treatment of mineral and waste materials is gaining more and more importance in industrial countries. The need to control occupational health and safety has been recognised, and regulations which describe general protective measurements for personnel provide a tool to protect their health. It is the aim of the paper to give an outlook for practical approaches to risk assessment and to present measures for exposure reduction in accordance with the state of the art in Germany.Both the treatment of minerals and of waste materials are described in relation to the risk assessment. The method of evaluating health hazards in the two industries is similar and therefore both examples are presented next to each other.The example presented in the paper is the German “Biostoffverordnung” (the regulation for biological materials) which is important for the waste treatment industry. All kinds of waste treatment facilities (like composting facilities, waste dumps, sorting facilities for packaging materials) are obliged to carry out an assessment of health hazards for a variety of working areas and working places. The possible safety requirements deriving from this regulation are presented and discussed under the aspect of biological hazards."

Jan 1, 2003

By Chris Plackowski, Bruckard. Warren J., Anh V. Nguyen

"Enargite is a significant penalty mineral in the copper industry and its separation from many copper sulfides by flotation is difficult. The separation may be crudely achieved using selective oxidation techniques or through the use of pulp potential control. This paper summarizes our latest contributions to a better understanding of enargite surface electrochemistry and hydrophobicity. Oxidation, roughness, hydrophobicity and species formation on the surface of natural enargite were examined by a novel experimental approach that combines electrochemical techniques, atomic force microscopy, X-ray photoelectron spectroscopy and droplet evaporation tensiometry. It allows for synchronized electrochemical control and examination of the oxidative surface morphology, speciation and hydrophobicity of enargite at pH 4 and pH 10. At low pH, surface layer formations consisting of metal deficient sulfide and elemental sulfur were identified associated with a limited increase in roughness and heterogeneous distribution of surface species produced by initial rapid dissolution of Cu, followed by diffusion limited surface layer deposition. At high pH, a similar diffusive mechanism associated with oxidation products consisting of copper sulfate and hydroxide and a significant increase in surface roughness were established. Receding contact angle measurements showed no significant difference in the contact angle on a surface oxidized at pH 10 and the freshly polished surface. Contact angle increased from 46° on the polished surface to 59° after oxidation at pH 4. Competing effects of hydrophilic copper oxides and hydroxides, and hydrophobic species of elemental sulfur on the mineral surfaces under oxidizing conditions at pH 4, and the change in surface roughness at pH 10, contribute to the changes in enargite hydrophobicity under electrochemically-controlled oxidation conditions. Most likely, both surface species and surface roughness produced by oxidation are critical to the changes in the wettability of enargite and other sulfide minerals."

Jan 1, 2014