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By O. A. Punishko, G. G. Mineev, Zabaikalsky Ore-Dressing Plant, M. V. Malova, O. V. Belousova, S. A. Bogidaev

"In order to intensify benefication processes (flotation and magnetic separation) for rebellious tantalitecolumbite ores electrochemical machining of pulp (ECM) is suggested instead of costly mechanic-chemical activation and magnetizing roasting. Any change in the surface mineral-semiconductor potential under the action of electrochemical treatment results in the change in the isoelectrical state of the surface and the adsorption property of the mineral with respect to ionogenic reagents-collectors. In this case conditions are created for regulating the ion composition, reduction-oxidation potential and pH of the liquid phase of the pulp without any extra introduction of expensive and often ecologically harmful chemical substances.Ores containing tantalum and niobium are characterized by complex chemical composition, determining their physical properties (conductivity, dielectric penetration, magnetization value, etc.) and their electric susceptibility.The authors investigations show that the pulp electrochemical treatment leads to the increasing magnetic susceptibility of the paramagnetic minerals. The main chemical elements forming the columbite-tantalite minerals except tantalum and niobium are iron and manganese. They determine the rare-metal minerals paramagnets properties. The electrochemical treatment changes the relation of the oxidized and reduced forms of these elements having. The method of cathode pulp treatment before flotation is successfully tested industrially.In the field of noble metals metallurgy new technological proposals are reduced to the following. As is know, the production of noble metals from unusual raw materials demands the elaboration of principally new technologies new technologies in so far as the methods for gold and silver extraction from ores are as a rule low elective and at the existing level of engineering are economically not expedient.The analysis of the main trends in the field of non-standard raw material treatment shows that the perspective ones are the geo- and biotechnological processes (underground leaching and leaching in heaps - UL and HL and microbiological methods of metal extraction)."

Jan 1, 2003

By Y. Y. Zhou

This paper introduces the application of CRIMM high-gradient magnetic separator in refinement of feldspar powders as well as the supporting technical outfits needed by the refining process with the high-gradient magnetic separator as main equipment. It could reduce the content of Fe2O3 to 0.03% with a deferrization rate of 85.88% from the feldspar raw ore containing 0.17% Fe2O3by using the above refining technology, producing an ultrapure feldspar product.

Jan 1, 2014

By A. V. Abshilawa, D. G. Talakhadze, R. I. Sturua

"Processing of the tailings accumulated over the lifetime of Madneuli Copper Concentrator is an opportunity to extract additional salable copper and gold products. This paper presents a pre-concentration process for the valuable components (copper and gold) of the accumulated tailings. The developed process makes it possible to obtain a copper pyrite concentrate with a yield of 14.05%, copper grade of 1.36%, and recovery of 83.22% containing 3.78 g/ton of gold at a recovery of 84.31%. The bulk concentrate is produced by a combined process bringing together selective flotation to produce salable copper concentrate and hydrometallurgical processing of the selective flotation tailings to recover gold. KEYWORDS: FLOTATION, ALBION PROCESS, LEACHING, COPPER CONCENTRATE, SELECTION Madneuli Copper Concentrator, Georgia, was put into operation in 1975. Over its lifetime, 40 mn tons of tailings have been accumulated at the tailings storage facility (TSF). Sampling of the TSF has indicated that the average copper and gold grade is 0.23% and 0.56-0.65 g/ton, respectively. Accordingly, the TSF can be classified as a technogenic reserve. This paper discusses pre-concentration of valuable components using flotation, followed by processing of the bulk concentrate in the Albion process. Mineralogical analysis of the accumulated tailings showed that the main ore mineral is pyrite (11.71%). Copper minerals are mainly represented by chalcopyrite (0.7%). The main nonmetallic mineral is quartz (67.3%); sericite, chlorites, etc. also occur. Pyrite is present both as liberated grains and intergrowth. The absolute majority of copper minerals are found as intergrowth with pyrite, less often with quartz. Ore minerals are slightly oxidized. Chemical analysis results are shown in Table 1. Particle size distribution shows that the size class -0.2 mm - 0.045 mm has the highest grade of 0.85 to 0.97 g/ton of gold. Size class +1.25 mm has the lowest grade. Based on the chemical and mineralogical studies and particle size distribution, an optimized process was developed for pre-concentration of the valuable components prior to hydrometallurgical processing. Several gravitation, direct selective, bulk, and bulk selective flotation processes were trialed. (1,2)"

Jan 1, 2018

By Y. De Gao, C. Gang Zhong, X. Yang Qiu, Li Wan

The chelating reagents are used as effective collectors in wolframite flotation, and certain metal cations need to be added using chelating collectors so as to activate valuable minerals and obtain good flotation indexes. Different metal cations will result in different reactivity with collectors, in order to select the effective activator in BHA flotation of wolframite, the activation effectiveness of different metal cations on wolframite ((Fe,Mn)WO4) flotation were studied using pure minerals. The results showed that the wolframite activation by Pb2+was the best among the selected cations. The maximum flotation recovery of wolframite was found to be 95.58 % under conditions of 100mg/LBHA and 1×10-4mol/L of Pb2+at pH 9. The dosage of Pb2+needs to be controlled in an optimum range. Also, the activation mechanism of Pb2+ on BHA flotation of wolframite was investigated by measurements of contact angle, zeta potential, adsorption capacity and IR spectroscopy. It was found that Pb2+ could chemically adsorb onto the wolframite surface improving the flotability of wolframite and enhancing the adsorption of BHA on wolframite. When the dosages of BHA and Pb2+ were 100 mg/L and 1×10-4 mol/L, the adsorption quantity of BHA on wolframite sharply increased up to 0.30 mg/L at pH 9 compared with wolframite treated with only BHA.

Jan 1, 2014

By Steven Bradshaw, Edson Charikinya

The application of high power microwave energy to secondary crusher products has been shown to induce micro fractures and cracks in the ore. This suggests that heap leaching could benefit from microwave-induced fractures, as the extent and kinetics of heap leaching processes depend on the accessibility of grains to lixiviants, which can potentially be improved through microwave treatment. The density and pattern of microwave induced cracks and how these cracks subsequently affect heap leaching recovery has not yet been investigated. The objective of this study was to apply X-ray micro computed tomography (X-ray CT) to investigate microwave induced cracks in large cone and HPGR crushed sphalerite particles within 3D space. The ore particles were microwave treated in a single mode microwave applicator coupled to a switched mode power supply and a water cooled microwave transmission sub system operating at 2.45 GHz. The ore particles were treated at specific absorbed microwave heating energies of between 2 and 3kWh/t by treating at 6 kW of forward power for treatment times of 1 s. X-ray tomography analysis was conducted on fine (-5+4.75) mm, medium (-16+9.5) mm, and large (-25+19) mm sphalerite particles before and after microwave treatment at voxel resolutions of 5 µm, 15 µm and 25 µm respectively. Image segmentation, thresholding and spatial registration techniques were used to study crack patterns in 3D images of HPGR and cone crushed particles. Analysis of the X-ray CT images after microwave treatment shows considerable micro crack formation within the Cone and HPGR crushed particles. The cracks pattern showed interphase cracks propagating across all phases, with no evidence of preferential cracking. A greater density of microwave induced cracks was observed on fine (-5+4.75) mm particles compared to the medium (-16+9.5) mm and (-25+19) mm large particles. The results showed overall increased particle porosity following microwave treatment.

Jan 1, 2014

By Wenying Liu, Marek Pawlik

Long-chain ionic surfactants, with fatty acids and amines as the most important representatives, are widely used as collectors in froth flotation. These surfactants, generally referred to as weak electrolyte collectors, frequently form solid insoluble precipitates within a certain pH range. However, the action and behavior of these colloidal precipitates in froth flotation systems are not well understood and has not been well decoupled from those of dissolved forms. The objective of this study was to understand and compare the role of colloidal precipitates with that of the dissolved forms at gas-liquid and gas-liquid-solid interfaces. Using primary amine as the model surfactant, experiments were carried out to measure: the maximum volume of bubbles generated in the presence of dissolved and precipitated forms of the surfactant; surface tension for both forms of the surfactant using the drop shape and maximum bubble pressure methods; and contact angle using the sessile drop method. The experimental results showed that: in the presence of the precipitate, bubble volume was smaller, which was correlated with the lower surface tension and higher contact angle measured; the surface tension of solutions containing surfactant precipitate was affected by the surface age of liquid droplets. This study enhances understanding of the interfacial behavior of long-chain ionic surfactants under different conditions, which would help improve the efficiency of reagent utilization in froth flotation.

Jan 1, 2014

By B. Orberger

The fine fraction (< 2 mm) of the high grade Mn-ore from the world class Moanda deposit, Francevillan basin, in Gabon, contains up to 30 wt. % of manganese and about 0.4 wt. % phosphorous. A pilot study at laboratory scale integrating mineralogy and geochemistry before and after ultrasonic treatment was conducted on the fine fraction (< 2 mm) of oxidized Mn ore in order to reduce the phosphorous content and enrich this fraction in manganese. The fine fraction was dried, crushed at 2 cm and sieved at 2 mm. The two fractions (< 2 mm and 2 mm ? 2 cm) were investigated by X-ray diffraction and scanning electron microprobe ? electron dispersive spectroscopy analyses. Both fractions contain lithiophorite, cryptomelane and pyrolusite as Mn carrier, and goethite, muscovite, illite and quartz as contaminants. The Mn hydroxide nsutite was only found in the fraction 2mm ? 2 cm.The < 2 mm fraction is significantly richer in goethite, muscovite/illite, and quartz. Phosphorous carriers are mainly goethite (up to 2.8 wt. % P2O5), while the Mn minerals contain up to 0.8 wt. % P2O5. The Mn minerals are partly included in an agglomerate of goethite, muscovite/illite, and quartz. The < 2 mm fraction was treated by ultrasound for 30 s in normal water. Mineralogical and chemical analyses after ultrasound treatment showed that the Mn-minerals were largely liberated from the goethite-muscovite-illite agglomerate. Mass balance calculations show that after ultrasonic treatment the < 2 mm fraction was ? 50 % enriched in Mn and ?50 % impoverished in P.

Sep 1, 2012

By I. N. Babich

"Complex technological problems associated with the processing of mineral raw materials require the search and development of new means and ways of thinking. At present, computer cognitive graphics (CCG) are one of the most actively developing areas of new information technologies. The aim of the study was to optimize the cycle of technological evaluation of ores at all stages of geological exploration of deposits on the basis of analysis of geological sampling data using CCG. A new approach has been developed that facilitates optimization of the whole cycle of subsoil exploration. At the gold ore deposit, the results of the geological sampling data were processed by the method of constructing the CCG in the form of a histogram showing the frequency of gold extraction and the average amount of its content. Significant peaks of the metal content in the ore, exceeding the level of the average content in the ore by tens of times, have been revealed. Graphical interpretation of the parameters of mineralization reflects the uneven nature of its variability, which indicates the presence of large, rarely occurs of gold in the ore and the need to conduct studies on a sample of ore of greater mass than for ores with tiny gold. On a sample of 50 kg gold-quartz ore studies were carried out on gravity enrichment. The maximum size found in the gold concentrate was 0.07 mm. In the course of integrated tests in a gravity concentrate, gold particles up to 3 mm in size were found, which predetermined the need to include the operation of gravity before flotation. A new approach to subsoil research is protected by a patent (RU 2620823).The technological problems that arise before the researcher associated with the processing of resistant ores require the exploration and development of new means and ways of thinking. New problematic situations on complex mineral and raw materials objects are practically not amenable to resolution by existing methods. Integration of industrial and information technologies is necessary. At present, computer graphics (CG) is one of the most rapidly developing areas of new information technologies. For example, in scientific research, including in fundamental research, the accent from the illustrative function of CG (the visualization of what is already known) is increasingly shifting towards the use of computer cognitive graphics (CCG) tools (Bashlykov, 2016). The function of the CCG is to obtain a new knowledge with the help of a graphic representation - a cognitive image or at least to promote the intellectual process of the logical acquisition of this knowledge. In this study, cognitive images are used to graphically represent the distribution of valuable components in the bowels of the deposit, characterizing the state of mineral-raw materials."

Jan 1, 2018

By T. C. Sun

Two wasted activated sludges (WAS), from an industrial wastewater treatment and a sewage treatment plant respectively, and 7 collectors are used to investigate the feasibility of air flotation thickening of WAS by adding the collectors used in mineral processing. The collectors experimented include straight chain fat acids with different chain length, sodium oleate, alkyl sodium sulphonate, sodium dedecylsulfonate, and dodecylamine. The results show that the thickening efficiency varied depending on different collectors. Of the collectors experimented, dodecanoic acid and dodecylamine are best collector for thickening both sludges.

Jan 1, 2014

By D. Saramak

Investigations over the application of hybrid comminution circuits with the High-Pressure Grinding Rolls (HPGR), on the main comminution stage on the basis of the lime and cement industry, were presented in the paper. Two crushing circuits were investigated, the first HPGR-based and the other one, with conventional jaw crusher. The results presented in the article confirm that hybrid comminution circuits with the application of HPGR are innovative ones, and they assure achieving the technological and economic competitiveness in the mineral raw materials processing industry. They are much more favorable in terms of the final product fineness and capacity but insignificantly less effective about the unit energy consumption. Technological performance of conventional crushing circuit and HPGR-based one were also compared in lab scale. The circuit with HPGR application gives finer products both on crushing and grinding stages. The average particle size reduction obtained in HPGR-based circuit is as much as twice greater, comparing to the conventional crushing devices. Keywords: comminution, HPGR technology

Sep 1, 2012

By Lutz Rolf, Halit Z. Kuyumcu, Salas Cazón. Milton A.

Aim of experimental investigations was the mathematical description of the abrasion process running with a single particle stress. This is on the one hand the basis for the physical interpretation of the process, on the other hand the base for the simulation of abrasion processes carried out in technical scale. With this investigation for the first time the influence of the particle shape changing with increasing abrasion progress was quantitatively described. This influence affects itself particularly strongly on break-fresh particles up to an abrasion degree of approximately 10 to 20%. This is for the description of technical processes the most interesting area.

Jan 1, 2003

By David Dreisinger

"The leaching of base and precious metal ores and concentrates continues to progress in both laboratory study and industrial application. These developments are being driven by the need to respond to difficult ores and concentrates that are not amenable to conventional treatment. In many cases alternatives are being developed to conventional treatment (e.g. Pyrometallurgy) for technical and economic reasons.In this paper, a brief general review of some new developments in leaching will be followed by a more detailed explanation of three process developments that have either been industrially applied or are expected to be applied in a short time frame. The three processes to be reviewed in detail are the Mt. Gordon Copper Process, the Anglo American Corporation/University of British Columbia Copper Process and the PLATSOL Process. These leaching processes operate at low (90°C), medium (150°C) and high (220°C) temperature and are successful in quickly and completely extracting metal values from ores and concentrates.INTRODUCTIONThe process of leaching is widely used in hydrometallurgy to selectively recover a metal of interest from an ore or a concentrate. Leaching and by extension hydrometallurgy is well established in the recovery of copper (copper heap leach ? SX-EW), nickel (Moa Bay and Caron process), zinc (roast ? leach ? electrowin and zinc pressure leach), gold (cyanidation) and uranium (acid sulfate leach). Of course this success extends to many of the metals found in nature. Recently, the importance of hydrometallurgy appears to be increasing with hydrometallurgy viewed as an attractive alternative to both traditional mineral processing and conventional smelting/converting/refining. This increasing interest has led to intensive study and increasing application. Selected developments include:Copper ? the Mt. Gordon process and new concentrate processes such as INTEC, Activox, CESL, Dynatec, Total Pressure Oxidation, MIM Albion, BioCop, and the AAC/UBC Process.Nickel ? Voisey Bay process for hydrometallurgical treatment of Voisey Bay concentrate, HPAL processing of laterites at Murrin Murrin, Bulong and Cawse, atmospheric leaching of laterites, heap bioleaching of nickel sulfides by Titan Resources (Australia).Zinc ? establishment of zinc leach, solvent extraction and electrowinning technology for treatment of the Skorpion deposit in Namibia, new developments in atmospheric and pressure leaching, the Hydrozinc process.Gold ? development of a number of thiosulfate leaching processes for recovery of gold from refractory carbonaceous ores or concentrates."

Jan 1, 2003

By J. K. Qu

As one of the key inorganic chemical industries, the chromate chemical industry has spawned extensively public concerns due to the resulted environmental pollution. The cleaner production technology for chromium compounds bases on sub-molten salt medium developed by the Institute of Process Engineering, Chinese Academy of Sciences has greatly decreased the reaction temperature and energy consumption, significantly in-creased the utilization ratio of the chromium element, and successfully achieved the comprehensive utilization of chromite resources and zero emission of chromium-containing residue. The separation process of production is the most important components in the cleaner technology. In this work, we studied two parts: the first is the removal of SiO2, Al3+ from the system and the recycling utilization of alkali metal medium through adding Ca(OH)2 and CaO; the second is to get more pure K2CrO4 crystalloid and remove K2CO3 from KOH solution through evaporation to prepare raw material for manufacturing Cr2O3 and get 50%(wt) KOH. The results obtained show that Ca(OH)2 can remove Al3+ more than CaO and has lower caustic ratio than CaO when they were added 110% of theoretic quantity. The optimal pure K2CrO4(96%) can be gained at 45 Celsius degree in 30% KOH solution and K2CO3 in 50% KOH solution could be decreased to 3.5%(wt) at 40 Celsius degree. And then K2CO3 can be causticized with adding Ca(OH)2 to recycle potassium alkali. The impure material can be re-moved and suitable raw material for manufacturing Cr2O3 can be gotten and reaction medium can be also recycled in this process technology, realizing cleaner production effectively.

Jan 1, 2014

By L. O. Filipov, N. E. Menad, A. Geneyton

"Zeta potential of synthetic monazites presenting various compositions were measured to investigate the effect of the main lanthanides substitutions on electrophoretic mobility and resulting IEP. The measurements are performed in a CO2 depleted and enriched solutions showing both reduced influence of monazite chemistry and strong influence of ions resulting from the solubilization and dissociation of CO2. The influence of oleic acid on the electrophoretic mobility of those monazites was also investigated. The influence of pH on oleate adsorption was studied using a bubble/particle adhesion system. Adhesion strength measurements were performed on pure synthetic monazite-(Ce) and monazite-(La). An extensive thermodynamic model of monazite in water was developed to highlight correlations between lanthanides hydroxides/carbonates species concentrations in the bulk solution and oleate adsorption. Based on electrophoretic measurements, advanced thermodynamic consideration and adhesion measurements, further details of the oleate adsorption model on monazite surface were proposed.INTRODUCTION Electrophoretic and potentiometric data on monazite and, a fortiori, other rare earth semi-soluble salts such as bastnaesite are extremely erratic (Chelgani et al. 2015). The isoelectric points measured with electrophoretic mobility methods range from 4.7 to 6.5 although sporadic data indicates an IEP (isoelectric point) far from that range. Different explanations are proposed in the literature to explain the IEP variability notably the numerous chemical substitutions that frequently occurred within monazite crystal lattice (Chelgani et al. 2015). Based on lanthanides speciation diagram, several authors highlighted the influence of specific lanthanide species on the flotation performance of rare earth semi-soluble salts when carboxylate or hydroxamate collectors are used. Although lanthanides ions have a great affinity for carbonates groups (Kragten et Decnop-Weever 1987), lanthanide (hydrogen) carbonates were not implemented in speciation diagrams. In this work, an advanced thermodynamic model is proposed to highlight correlation between flotation performance and lanthanide species predominance but also concentrations. Qualitative measurement of the monazite surface hydrophobicity are performed through tests of adhesion of coarse monazite particles onto bubbles. Since flotation and microflotation technics are highly influenced by hydrodynamic parameters, this method was investigated to obtain a sharp contrast between appropriate and inappropriate pH conditions. This paper is to investigate 1) the effect of lanthanides substitution on monazite surface properties through zeta potential measurements, 2) the mechanism of adsorption of carboxylates on monazite surfaces and 3) the effect of CO2 on monazite surface properties and carboxylates adsorption."

Jan 1, 2018

This study examines the surface alteration and flotation behaviour of synthetic moncheite, PtPd(BiTe)2, in the presence of pentlandite. The telluride minerals contribute around 20% ~ 30% and up to 45% of the PGM present in the Platreef ore and are considered to be slow floating as there is evidence of these minerals reporting to the tailings. It was proposed that oxidation products from other minerals and grinding media would affect the mineral surface composition and floatability thereby causing inadvertent depression of moncheite due to precipitating ions. ToF-SIMS analyses (time of flight secondary ion mass spectrometry) was used to characterise the mineral surface as well as the extent of surface alteration. Microflotation was used to deter-mine the hydrophobicity of the synthetic minerals. Conditioning of moncheite in the presence of pentlandite reduced the flotation response of the + 38 -106µm size fraction from > 99% to 56%. This was due to pentlandite dissolution products (iron and nickel hydroxy species) which formed overlayers on the mineral surfaces thereby inhibiting the adsorption of collector. In addition, further grinding of these samples, with and without pentlandite conditioning showed a negative effect on recovery due to the fineness of the particle size distribution and there was no advantage gained from any possible exposure of fresh sites in the sample.

Jan 1, 2014

By Yu. Gurevich, M. Teremova, I. Prokopev, A. Razvjaznaya, N. Algebraistova

"The objective of this work is the scientific justification and development of efficient and environmentally-friendly method of bulk concentrate preparation for selection with application of microbiological practices. This research suggests to apply Pseudomonas Japonica bacterial culture to the bulk concentrate before the selection circuit in order to clear the surface of sulphides from the xanthate skin. It is also suggested to apply bacterial consortium Ochrobactrum ?nthropi and Pseudomonas aeruginosa JCM 5962 for desorption of diesel residual concentrations. High-efficient and environmentally friendly method of copper-molybdene and lead-zinc bulk concentrate selection was developed based on theoretical and experimental research work with application of microbiological practices. In comparison with conventional methods (steaming, sodium sulphide washing) the above suggested bio-technological method of bulk concentrate preparation before selection cycle will allow to reduce material and power expenditures, and it is also environmentally friendly. INTRODUCTION High-efficient selection of sulphide bulk concentrate is gained exclusively after collecting agent is removed from mineral surface. Therefore, the problem of bulk concentrate preparing before the selection cycle is acute, since the further technological parameters of the subsequent separation depends on the effectiveness of pulp preparation. Existing traditional ways of bulk concentrate preparation. such as washing or steaming, are characterized by high energy and material costs in industrial conditions [1,2]. The microbiological treatment before separation of the bulk concentrate into different kind of concentrates appear one of perspective processes for treatment of bulk concentrates [3,4]. At the present time, the world practice of processing mineral raw materials demonstrates the wide application of technologies using microorganisms: bacterial leaching and oxidation, purification of industrial wastewater. This is due to the fact that biotechnological methods are environmentally safe, low-cost, and suitable for refining complex ores and raw materials of industrial origin."

Jan 1, 2018

By J. Leite

In a small-scale mining in Brazil?s northeast, scheelite were exploited since 1940?s using a traditional gravity concentration flowchart (composed by jigs and shacking tables) that operates with low efficient for fine particles. Tailing of this plant was submitted to chemical, mineralogical and size characterization. Results pointed 50% smaller than 74µm with a grade of 0.11% WO3. The particle?s size is an important operational variable to heighten recuperation by shacking tables. Tests using Falcon SB40 centrifuge concentrators and shacking table were realized, optimizing their operational variables. Based on the tests results a new flowchart was proposed for concentrating and tailings recovery.

Sep 1, 2012

By S. Gaydardzhiev

Laboratory batch tests having preliminary and orientation character aiming at improvement of the molybdenum flotation at Ellatzite copper processing plant in Bulgaria have been conducted. The following technological parameters have been screened to study their influence on the grade and recovery of copper and molybdenum during the rougher flotation stage: flotation pulp density, pH, addition of secondary collector and replacement of MIBC by pine oil as a frother. The results have shown that slightly better grade/recovery figures could be obtained for both copper and molybdenum at lower flotation pulp densities. The addition of kerosene has improved the recovery of molybdenum however, on the expense of that of copper. The effects from pH variation and the replacement of MIBC by pine oil as a frother have been almost negligible.

Sep 1, 2012

By X. Xu

This paper presents the research on comprehensive recovery of copper, gold, silver and iron from tailings from high-intensity magnetic separation in Tonglushan Mine. By comparison of experimental results of three flowsheets?regrinding of tailings-conventional sulphidizing flotation, water heating enhanced sulphidizing flotation and acid leaching-sulphidizing precipitation flotation, it is concluded that regrinding of tailings-conventional sulphidizing flotation flowsheet has the best economical and technical performance and practicability. Regrinding and using the mixture of sodium hydroxamate and sodium xanthate are two of the notable technical characteristics of this best flowsheet. The system for comprehensive recovery of tailings has been put into production. It not only can recover the valuable minerals from tailings in Tonglushan Mine, but also can reduce the environmental pollution, resulting great economic and social benefit.

Jan 1, 2014

By J. H. Zhang

An atomic force microscope has been used to measure the forces acting between two silica and two rutile surfaces in the presence and absence of cationic surfactants, CnTACl (n = 12~18). The forces measured in the absence of surfactant can be fitted to the DLVO theory. At short separations, however, the silica surfaces exhibited repulsive hydration forces, while the rutile surfaces did not. On the other hand, the forces measured in the presence of the cationic surfactants show long-range attractions that are larger than the van der Waals forces. The long range attractions are the strongest at of the point of charge neutralization (p.c.n.), which decreases with increasing surfactant chain length. The possible origin of the long-range attraction has been tested in view of the charged-patch model of Miklavic et al. (1994). However, the sizes of the patches back-calculated from the model were much larger than those the patches (or hemi-micelles) determined experimentally and reported in the literature. It is, therefore, suggested that the long-range attractions observed in the present work are due to the structural response of the water molecules in the vicinity of hydrophobic surfaces.

Jan 1, 2014