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By K. Amano, K. Haga, Y. Watanabe, A. Shibayama, A. Batnasan, A. Battsengel

"Apatite is an important host mineral in igneous and metamorphic rocks for production of phosphate fertilizers and phosphoric acid, and a potential source of rare earth elements (REE) production. For dissolution of REEs, sulfuric acid is better leaching reagent to develop the economical viable process for recovering of rare earth elements from apatite ore. However, the efficiency of rare earth elements dissolution in H2SO4 is about 30 % due to the formation of calcium phosphate or calcium sulfate as precipitate. On the other hands, phosphorus is mainly produced from phosphate ore. However, when treating rare earth elements containing phosphate ore, rare earth elements were discharged. Hence, development of novel apatite ore treatment process is required for effective utilization of natural resources. In this study, apatite deposit associated with REE was treated with sulfuric acid leaching and two stage precipitation by oxalic acid (C2H2O4) and magnesium chloride (MgCl2) for recovering REE and phosphorus, individually. Results showed that it can be seen the vast majority of La (87.5%), Ce (87.3 %), Pr (86.1 %), Nd (85.2 %) and Y (90.9 %) were dissolved in 1 mol/L diluted H2SO4 solution from the apatite ore. As average leaching rate of REE, over 85% of REE were leached by the condition. In the first stage precipitation using the obtained pregnant leach solution from leaching, over 90% of REE was precipitated by oxalic acid addition after controlling pH to 1 by NH4OH solution. After pH changed to 8.5, over 90% of phosphorus was recovered as precipitate by magnesium chloride addition in second stage precipitation"

Jan 1, 2018

By M. D. Amirova

Cyanide-free technology of complex copper-lead ores flotation may be improved through enlarged range of pH values, enhanced copper recovery into copper concentrates due to additional recovery of secondary copper sulfides, as well as through enhanced efficiency of lead sulfides depression in process of new flotation modifiers-based selective separation. Study of the effects of flotation modifier (of metal nature) on minerals surface conditions proved that the xanthate is practically not adsorbed on the galenite surfaces due to minerals hydrophilization. Joint effects of sodium sulfite and modifier enhance process conditions for intensive galenite depression and at the same time for effective chalcopyrite and chalcosine flotation within a large pH values range (from pH=8 to pH=10). Identified mechanisms carry inference that proposed chemical reagent treating method is very promising for selective copper-lead concentrates separation. Potential use of carbon-containing materials as zinc flotation modifier to enhancing zinc recovery in processes of lead-zinc ores treatment has been studied. In our flotation tests we used Shalkiya (South Kazakhstan) lead-zinc ores containing such impurities as carbon shales, which presence impedes the process of saleable concentrates production and gives rise to excessive consumption of flotation agents due to the xanthate adsorption on the carbon. Lead and zinc concentrates were produced by process stages as follows: ores milled to 95% Cl. -0.074 +0; lead and zinc roughing flotation and further recleaner and testing operations. Test flotation in open process cycle resulted in enhancing zinc recovery into zinc concentrates by 21.1% and increasing zinc content in zinc concentrates by 3.96% that evidences promising potentialities for use of carbon-containing products as additional zinc flotation modifier. Works were carried out under National Program 2003~2005 of fundamental researches ?Physical and Chemical Mechanisms of Interactions in Multicomponent Solid and Liquid Systems Specific for Integrated Processing of Complex Metal-Containing Minerals and Technogenic Raw Materials? and contractual Agreement 2005 Optimization of Production and Technology of Shalkiya Lead-Zinc Ores Processing at Kentau Dressing Works.

Jan 1, 2014

By Rogerio C. Guimarães, Antonio E. C. Peres

The production of phosphate concentrates (phosphate rock) from slimes represents a challenge to the phosphate industry worldwide. In Brazil, this challenge is particularly relevant due to the consistently low P2O5 grades and the igneous origin. The first industrial experiences of producing phosphate rock from slimes (-44µm or -325#) fraction started at Arafertil, currently Bunge Fertilizantes SA, in Araxá, in the 1980.s. This production corresponds, nowadays, to 35% of the total production of concentrates in the company (830,000t/year) in a circuit consisting of desliming in 40mm microcyclones and concentration in flotation columns, corn starch and fatty acids being utilised as reagents. The performance of slimes flotation and the process control, at Bunge´s concentrator, were improved after the introduction of column flotation technology, in the first half of the nineties. The column flotation technology for slimes recovery was expanded to other Brazilian concentrators still in the nineties: Ultrafértil (Catalão - GO), Bunge (Cajati - SP), Fosfértil (Tapira - MG) and Copebrás (Catalão - GO). At present the Brazilian production of phosphate rock is approximately 4.5Mt/year, with a strong trend for a market increase. Genuinely Brazilian technology is utilised for the processing of slimes, the concentrates representing 11 to 13% of the overall production. The production of apatite concentrates from slimes was relevant to increase phosphate recovery and reduce costs, contributing to the growth of the fertilisers industry.

Jan 1, 2003

By Luis Bergh, Francisco Díaz, Isabel Panire, Juan Yianatos, Luis Vinnett

"In this paper, industrial data of residence time distribution (RTD) in mechanical flotation cells is presented, which were measured in several plants using the radioactive tracer technique. Results include mechanical flotation cells of 100 - 300 m3, which were operated with effective residence times from 2 to 7 min. Tests were developed in forced air and self-aerated cells for liquid and solids (non-floatable) per size classes. Different RTD model structures including perfect mixer, Large and Small Tanks in Series (LSTS) and by-pass flow plus perfect mixer were evaluated and compared for single cells. The actual mixing regime was related to the effective residence times and cell designs based on the model fitting. By-pass flow percentages were typically lower than 10%, therefore the perfect mixer model plus a dead time was a suitable model structure in most cases. On the other hand, the arrangement of cells in series was effective in reducing the bypass flow observed in single cells (by-pass flow percentage greater than 5%). In addition, the N perfectly mixed reactor in series model was used to represent the mixing regime along flotation banks, which were operated with mean residence times in the range of 18 - 53 min. Results showed that N tanks in series plus dead time were closer to the actual values in most cases."

Jan 1, 2014

By Tamara F. Kondrateva, Evgenia E. Savari, Galina V. Sedelnikova, Rauf Y. Aslanukov, RAS (INMI), Grigori I. Karavaiko

"The investigation is dedicated to study of biohydrometallurgical processing of refractory gold-arsenic concentrate with the large content of pyrrhotite. Sulfide concentrate of chemical constituents: 75g/t Au, 4,7g/t Ag, 6,3% As, 29,3% S, 2,3% Sb, 0,5% ? (organic) and of mineral composition, %: 11,8 arsenopyrite, 39 pyrrhotite, 12 pyrite, 2,9 antimonite and the rest – aluminosilicates, carbonates and quartz, was studied. The recovery of gold from concentrate by cyanidation is 51,2%. The rest of gold is embedded as finegraded segregation in sulfides.Sulfide oxidation process study is described. Bacterial oxidation was executed on a pilot laboratory unit using combined autotrophic bacterium: A. thiooxidans , A. ferrooxidans, Leptospirillum ferrooxidans and sulfobacillus thermosulfidooxidation, pH=1,5-2,2, t=28-32?C, oxidation time 120 hours. Pyrrhotite is the least stable sulfide mineral with electrode potential 0,45V versus arsenopyrite (0,55 V) and pyrite (0,55-0,6 V) and is oxidated primarily. Pyrrhotite oxidation is followed by large amount of elemental sulphur, which has a bad influence on cyanidation.It’s established that the rate of arsenopyrite (for the first 48 hours) from concentrate containing 39% pyrrhotite is 2-3 times as less as the rate of arsenopyrite bio-oxidation from concentrate without pyrrhotite. The arsenopyrite bio-oxidation is accelerated only after the elemental sulfur was oxidized by bacterium A. thiooxidans and elemental sulfur percentage was reduced from 6,8 to 3,9%. The bacterium concentration is increased from 2,5x107 to 2,5x109 cells/ml. Almost full oxidation of arsenopyrite (98%) and pyrrhotite (98- 99%) is finished in 120 hours. We have studied two pretreatment methods for elimination sulfur content influence on cyanidation: aeration in lime and electrochemical treatment. Such an operation enables to have supplemental oxidation of elemental sulfur and other oxygen and cyanide absorbants before cyanidation. After treatment the content of elemental sulfur was decreased from 3,9 to 2,2%, gold recovery from 90 to 96% and cyanide consumption from 16,2 to 7,2 kg/t decreases. The content of toxical rhodonite-ions in liquid phase of pulp and disinfection reagents consumption were decreased as result of elemental sulfur content in bio-oxidated product reduction."

Jan 1, 2003

By Ranjeet K. Singh

Kelsey Centrifugal Jig was found to be promising for the beneficiation of fine coal particles. The present study was aimed at in-depth understanding of the separation features of Kelsey Jig through detailed experimentation. Beneficiation of fine coal of size 150 x 300 µm was studied in a laboratory Kelsey Jig. The thickness of the ragging bed is found to be an extremely crucial parameter apart from the other process parameters such as rotational speed and pulsation frequency. A constant pulp density (25% solids) of the feed slurry was maintained in the study. The feed rate was also kept constant at 50 kg/hr dry solids. Silica sand of size -1.68+0.85 mm was used as ragging material to avoid the pegging of internal screen having an opening of 425 µm. The rotational speed was found to have significant effect on the depth of the ragging bed and its porosity, which influenced the separation performance considerably. Pulsation was identified as the key factor in stratifying the coal bed and defining the misplacement as well as ragging bed porosity, which influenced the mass yield and quality of the products. Beneficiation studies were carried out with rotational speed varying between 900-1000 rpm while pulsation frequency was kept within 850-925 rpm. In a single pass through the Kelsey Jig 7-8% (absolute) reduction in the ash content of the feed material was observed at more than 55% mass yield. High rotational speed, moderate pulsation, and low ragging bed depth favored good cleaning. A high bed depth was found to facilitate rejection of high ash materials. It was established that Kelsey Jig is effective in fine coal cleaning though a controlled operation is required in order to achieve superior performance. Keywords: enhanced gravity separator, g-force, separation performance, ragging material, coal beneficiation

Sep 1, 2012

By G. Mucsi

This paper deals with the laboratory investigation of cathode ray tube (CRT) glass based glass foam, a relatively new product so called ?Geofil bubbles?. The main process engineering material properties of raw materials, such as particle size distribution, moisture content, density and specific surface area are shown. Then the preparation of raw cathode ray tube glass waste is presented including the following steps: crushing in impact crusher, grinding in laboratory scale ball mill, mixing, pelleting and sintering. We found that it was possible to produce foam glass (with proper mechanical stability and particle density) from the investigated waste CRT glass. The material characteristics of the final product strongly depend on the sintering conditions. Optimum conditions were determined particle size fraction was found to be 4-6 mm, temperature 800 0C, residence time 7.5 min. Keywords: waste CRT glass, grinding, pelleting, sintering, glass foam

Sep 1, 2012

By Bulelwa Ndlovu, Saeed Farrokhpay, Dee Bradshaw

The effects of phyllosilicate minerals on the flotation performance and froth stability of a copper ore was investigated. It was found that various phyllosilicate minerals affect the copper recovery differently however they all caused the flotation grade to be reduced. The effect of different phyllosilicate minerals on the froth stability followed the order of talc >> montmorillonite > muscovite > kaolinite > illite. The results demonstrated that there could be a relationship between the deleterious effect of phyllosilicate minerals on the flotation and froth stability. Talc and montmorillonite have both shown the highest effect on the flotation recovery and grade as well as froth stability. On the other hand, illite has the least effect on the both flotation performance and froth stability. Kaolinite and muscovite also affected the copper flotation grade (but not the recovery) while they also affected the froth stability. Therefore it is possible to control the flotation performance when phyllosilicate minerals are present via monitoring and controlling froth stability which needs to be investigated further.

Jan 1, 2014

By L. W. Luo

Zeolite in some regions or countries of the world have been the subjects of materials for environmental remediation involving the use of removal to heavy metal ions and some organic pollutant as a sorbent because of its capacious ions exchange and huge surface area. This article addresses the equilibrium and kinetics for manganese adsorption using zeolite modified by hexadecyl trimethyl ammonium bromide (HTMAB) as a sorbent material over a range of pH between 3.4~7.2 with eight different Mn(?) solution concentrations. PHzpc (pH of zero point charge) of the sorbent was examined according to the method proposed by Tripathy and Kanungo, and a value of 6.91 was obtained. The experimental data fit langmuir?s model for the majority of pH and Mn(?) solution concentrations tested (0.92<R2<0.97). The maximal adsorption capacity, qm ascending with pH between 3.4~7.2, rise from 15.01mg?g-1 at 3.4 to 19.46 mg?g-1 at 7.2. Besides, the constant of Freundlich Kf have the same trend with qm, increases with pH ascending. And the sorption intensity, represented by parameter 1/n in Freundlich?s model, is favorable in entire range of metal ions concentration studied. Finally, kinetics data accurately fit to pseudo-second order which indicate that there must be sorption of Mn(?) behavior occurring on inner-sphere of the sorbent.

Jan 1, 2014

By N. D. Ilankoon

"The use of thiosulfate as an alternative lixiviant for cyanide to treat complex refractory ores followed by the use of ion exchange resins (IX resins) for gold recovery has become an industrial reality. In this study, polyethylenimine (PEI) coated iron oxide magnetic nanoparticles (MNPs) were used to recover gold from the leaching solutions that consist of calcium thiosulfate, copper and gold. The gold loaded MNPs were easily separated from the solution using an external magnetic field. Proposing a novel adsorbent with characteristically easy solid-liquid separation, to recover gold from synthetic thiosulfate leaching solutions and gold elution and reuse of MNPs were the main objectives of this study. Adsorption isotherm studies revealed that the data fitted both Langmuir and Freundlich isotherm models equally well. The maximum adsorption capacity was 18.5 mg/g at pH 8 and 50?C. According to thermodynamic studies the physisorption process was exothermic and spontaneous. Gold and copper elution, and the regeneration and reuse of the nanoparticles were investigated and promising results were obtained. Different elution systems comprising sulfites, chlorides, glycine, EDTA (ethylenediaminetetraacetic acid) and sodium hydroxide were considered. Among them, EDTA for copper elution and NaOH for gold elution were the most efficient eluants. Regeneration and reuse studies revealed that the MNPs can be used for several cycles without significant performance loss. INTRODUCTION Although cyanidation has been used for gold leaching for more than 100 years, some major drawbacks associated with cyanidation have led to a quest for alternative lixiviants for gold leaching. Cyanide is ineffective in treating carbonaceous refractory ores as gold cyanide complex is adsorbed onto the native carbon in the ore itself known as preg-robbing. On the other hand environmental concerns associated with cyanidation drives the need for environmental friendly alternatives for cyanide. As of today, thiosulfate is known to be the most extensively studied and most promising alternative lixiviant for cyanide in both technical and environmental perspectives (Aylmore and Muir 2001, Oraby 2009)."

Jan 1, 2018

By C. A. Perez

Estimation of rock composition in mineral plants is important to determine rock size and grindability which in turn may improve control of the grinding process. Variations in ore grindability and size distribution directly affects mills power consumption and throughput. Therefore, it is desirable to develop new tools to estimate rock lithological composition. In this paper, a new method for lithological classification based on machine vision is proposed. The method is based on a single video camera and employs information about texture using several different spatial scales. Texture information is extracted from rock images using Gabor filters that can be adjusted at different spatial scales and orientations. After feature extraction, rock images are classified using support-vector machine (SVM). The method was tested on a database containing sub-images of 64x43 pixels of five ore types as follows: massive sulphide (MS), disseminated sulphide (DS), net textured (NT), gabbro (G), and peridotite (P). These ore types were assigned to three grindability classes: soft (MS), medium (DS and NT) and hard (G and P). The database was divided in 2 subsets for training, cross validation, and for test. Classification accuracy is compared with previously published results on a dataset with three different classes of rocks according to their hardness. Results show that our proposed method reached significant improvements (between 13%-20%) in classification accuracy relative to previously published results. Keywords: rock classification, lithological classification, grindability estimation, Gabor feature extraction, texture features

Sep 1, 2012

By F. Karakas

In this investigation, one of the most energy consuming stage of the cement manufacturing process, grinding stage, was studied. The aim of the study is to reduce the energy consumption. Optimum operating parameters were determined. Experimental studies were performed at three differ-ent stages. Grinding of limestone, clay and marl which are the main components of the cement, to approximately below 90 microns, was the first stage of the cement grinding. At this stage, effect of feed size and ball charge were investigated. At the second stage, the Bond work index of clinker and additives (slag, trass, limestone and gypsum) was found separately. After forming composite cement with clinker and additives, the Bond work index of this mixture was also determined, thus the results of separate grinding and grinding of mixture were compared. The Bond work index of mixture was found as 13.59 kWh/t, while the arithmetic mean of the Bond work index values of components was 14.90 kWh/t. Finally, clinker and additives (slag, trass, limestone and gypsum) were ground under the same conditions. At this stage, laboratory type of ball mill was used in order to understand grinding characteristics of the cement components. As a result of the experiments, it was found that energy consumption for the grinding will be lowered if the mills with 38 % ~ 40 % ball charge are used in the cement grinding. Moreover, grinding with mixture of clinker and additives gave better results than separate grinding of these components in terms of energy consumption.

Jan 1, 2014

By Herman D. Mendoza

A rapid recovery/recycling process was introduced utilizing the surface-chemical properties of finely dispersed mercury and alumina (Al2O3) fibers in aqueous environment. The conventional method of amalgamation or .ball milling. involves the mixing of a substantial amount of mercury to collect free gold during the grinding stage. In effect, a portion of the mercury is transformed into minute droplets that readily float and disperse in the amalgamation effluent. The fine droplets of mercury in the dispersion readily attached onto the positively charged macroscopic alumina fibers (i.e. = pH 9.8) at conditions pH 3 to 10. When an effluent from settling procedure after an amalgamation-grinding stage is passed through a column-bed packed with alumina fibers, maximum collection of negatively charged finely dispersed mercury occurred at pH 3 to 6. The collection/attachment efficiency was 99.5%. The collected droplets of mercury, which are left in the column-bed of alumina fibers, were subsequently rinsed with alkaline solution at pH 10 to 11.5. At these conditions, both mercury and alumina fibers carry negative surface potentials and resulted in the partial detachment of mercury from the alumina fibers. The detachment efficiency was only 30-35%. The attachment/detachment mechanisms in this study were analyzed using the DLVO theory.

Jan 1, 2003

By X. Q. Cao

As the second largest phosphate resource in the world, Chinese phosphate ores generally grades with low of P2O5. The presentation of beneficiation test on the low grade of phosphate rock in this paper may be used for a reference for development and utilization of the similar reserves. The ore is a marine sedimentary phosphate rock containing low grade of P2O5 and high content of MgO and R2O3; The banded structure shows its suitability for heavy medium separation. The laboratory heavy liquid testing results indicate that as specific gravity of the heavy liquid is 2.85 g/cm3, a rougher concentrate assaying 28.71% P2O5 could be obtained while the rougher tailings contain only 4.47% P2O5. When the combined process with heavy liquid separation followed by direct & re-verse flotation is employed to treat the feed containing 21.15% P2O5, 3.79% MgO, 1.86% Fe2O3, 3.66% Al2O3, 23.75% A.I, and specific gravity of heavy liquid is 2.84 g/cm3, the optimum mesh of grind is 67.5% minus 200 mesh, a phosphate concentrate contained 32.51% P2O5, 0.48% MgO, 0.81% Fe2O3, 1.69% Al2O3 can be produced at a yield of 55.24%. The concentrate P2O5 recovery is 85% with which quality comply with the Class A specifications for production of phosphate fertilizer.

Jan 1, 2014

Electrochemical behaviors of synthetic and natural enargite in buffer solutions have been investigated using open circuit potential, stationary polarization and cyclic voltammetry as functions of solution pH, scan direction, scan range, scan rate and dissolved O2. The results indicate that the electrochemical behaviors of synthetic and natural enargite are very similar; solution pH, scan direction, scan range and scan rate have remarkable effects on the electrochemical behavior of enargite while dissolved O2 has little effect on the electrochemical behavior of enargite. The potential range in which enargite possesses the ability of passivation is from ?0.9 V to + 0.83 V vs. SCE. Enargite is most stable in neutral and alkaline solution around potential ?0.2 V vs. SCE. The main oxidation products on enargite surface in alkaline solution are Cu(OH)2 while the potential imposed on it is within the range of ?0.2 V to 0.33 V vs. SCE and Cu(OH)2 + S0while the potential applied is higher than 0.52 V vs. SCE.

Jan 1, 2014

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 S. H. He

This paper focuses on the influence of pulp oxygen content on the separation of pentlandite and pyrrhotite contained in two different process streams in the Clarabelle Mill, operated by VALE INCO. The two process streams are (i) the scavenger cleaner feed, the product of regrinding the thickened, scavenged concentrate and the B cleaned tail produced from treating the non-magnetic fraction of the milled run of mine ore, and (ii) the magnetic concentrate which is the magnetic fraction of the milled run of mine ore. In the Clarabelle Mill, sulphite (SO32-) and TETA (triethylenete-tramine) are together used to selectively depress pyrrhotite from pentlandite. These depressants pre-ferentially decompose collector and/or sulphur enriched species at the pyrrhotite surface, an appar-ently essential mechanism in pyrrhotite depression from the scavenger cleaner feed stream. Selectivity in depression may originate from differences in the electrochemical rest potential of pyrrhotite and pentlandite. As both minerals are susceptible to oxidation, aeration in conditioning and flotation plays a key role in selective flotation. Important differences in the flotation behavior of pentlandite and pyrrhotite from the magnetic concentrate and the scavenger cleaner streams are highlighted in

Jan 1, 2014

By M. J. Lottering

Gold deposits in South Africa are invariably associated with uranium bearing minerals. Although it is low grade uranium by international standards, averaging around 0.3 kg U3O8 per ton of ore, recovery of uranium as a by-product improves the overall economics of gold extraction. Moreover, the current high uranium prices as well as increased demand due to renewed interest in nuclear power provide significant incentives for dedicated uranium production. An understanding of the uranium leaching response to changes in operating conditions is an important first step to-wards optimisation of uranium recoveries. In South African acid leaching plants, uranium dissolutions higher than 90% are difficult to achieve, and the chemical origin of this limit is not clear. To study leaching behaviour, an important consideration is the mineralogical characteristics of the ores. Typically, a diagnostic leaching approach can be followed. In this paper, a mineralogy-leachability explanation is presented to rationalise the difficulty in exceeding 90% dissolution from low grade uranium ores on the basis of a simple diagnostic leaching method. It was found that brannerite was the main reason for the existence of a dissolution limit in Witwatersrand ore and that chemical liberation was more effective to increase end dissolution compared to physical liberation. The findings from these investigations will form guidelines for developing economically viable flow sheets for improved uranium recovery, at least in a South African (Witwatersrand) context.

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 S. Castro

Molybdenite flotation is strongly depressed at pH higher than 9.5 in the flotation of Cu-Mo ores in sea water. Chemically sea water contains mainly Na+ and Cl- ions, but also some secondary ions, such as SO42-, Mg2+; Ca2+, HCO3-; etc., which are not necessarily indifferent for the flotation of molybdenite. The natural floatability of molybdenite in sea water and in NaCl solutions containing different secondary ions is investigated by micro-flotation tests. The tests indicate that the floatability of molybdenite in alkaline media in 0.6 M NaCl solutions is not affected by the presence of anions, such as, SO42- and HCO3-, at concentrations similar to those occurring in sea water. However, a strong depression of molybdenite at pH ranging from 9.5-10.0, is produced by the alkaline earth metal cations (Ca2+ and Mg2+ ions), dissolved in distilled water or in 0.6M NaCl solutions. It was found that effect of Mg2+ions is significantly stronger than Ca2+ ions. Effect of both ions is attributed to hydrolysis and adsorption of MOH+ hydroxy-complexes. This is followed by subsequent precipitation of hydrophilic colloidal hydroxides at the molybdenite/solution interface, and in bulk solution.

Sep 1, 2012