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By Tingting Li, Guodong Li, Dezhou Wei, Cong Han, Shuling Gao, Yanbai Shen

"The aim of this study is to solve the problem of tungsten leaching from scheelite concentrate using sodium hydroxide in the presence of phosphate by an autoclaving process, which is one of main development techniques for tungsten recovery. To understand the applicability and leaching performance of tungsten leaching from scheelite concentrate, the main work is to investigate the effects of leaching parameters such as initial concentrations of NaOH and Na3PO4, reaction temperature, stirring speed, liquid-to-solid ratio and reaction time on WO3 dissolution rate to obtain the optimal leaching conditions. The chemical composition and phase composition of the samples were evaluated by means of XRF and XRD. The content of WO3 in the leaching residue obtained via washing, filtering and drying was analyzed by thiocyanate spectrometric method. The optimal leaching conditions were found to be NaOH concentration of 6.76 mol·L-1, Na3PO4 concentration of 1.35 mol·L-1, reaction temperature of 180°C, stirring speed of 400 rpm, liquid-to-solid ratio of 2.0 and reaction time of 90 min. The results showed that tungsten leaching rate of 99.20% was reached under the optimal conditions. The technology exhibited superior leaching performance, which not only reduced the consumption of sodium hydroxide but also greatly decreased reaction time in comparison to a conventional autoclaving process. INTRODUCTION Tungsten is an important strategic metal, which is widely utilized in a variety of industries due to its high melting point, superior mechanical properties and heat-resistant performance [1-3]. The chief raw materials for the production of tungsten in nature are wolframite and scheelite [4, 5]. Among them, approximately two-thirds of the tungsten reserves contain scheelite deposits in the world [6, 7]. With the progressive exhaustion of high-quality wolframite resources, scheelite has become a predominant primary resource for the production of tungsten [8, 9]."

Jan 1, 2018

By S. Z. Shafaei

An experimental investigation has been carried out using a laboratory scale Denver flotation cell. For evaluation of cokeable coal of Alborze Sharghi coal washing plant, the full factorial method was used to statistically design and analyse the experiments. The 2 factorial interaction model were developed for combustible recovery and ash content as response and diesel dosage, conditioning time, feed percent solids and rotor speed as factors. Model validation and residual analysis were con-ducted and results indicated that the fitness, predictability power and residual distributions of models were good. The effect of parameters and interactions were examined and it has been demonstrated that rotor speed, solid percent and interaction between diesel dosage and solid percent were more important terms of all responses. A product with approximately 78% combustible recovery and 10% ash content was obtained at 4000gr/ton diesel fuel oil (high level), 30 sec conditioning time (low level), feed percent solids of 15% (low level) and 800 rpm rotor speed in appropriate condition.

Jan 1, 2014

By William Skinner, Jonas Addai-Mensah, Keith Quast, David Robinson, Jason Connor

A review of the laboratory- and pilot plant-scale physical separation techniques for the beneficiation of nickel (Ni) laterites shows limited efficacy. To date, the only upgrade technique adopted commercially, prior to hydrometallurgical processing of Ni laterites, is the removal of a barren, coarse size fraction in the feed by classification. In the present work we investigated two low grade (~ 1%), goethite-rich Ni laterite ores’ upgrading by magnetic separation, attritioning/coarse, (lower Ni-grade) gangue rejection and flotation techniques. Low intensity (0.1T) dry magnetic separation at ambient temperature of raw samples and those pre-heated at temperatures up to 450 °C showed evidence of pay metal Co and Mn bearing asbolane and/or lithiophorite minerals pre-concentration in the magnetic fractions. Ni distribution, however, did not show any noticeable magnetic upgrade but followed the weight distribution. Other ore pre-treatment methods (e.g., desliming and sulphidisation) followed by froth flotation with anionic and cationic reagents also led to noticeable (~35%) Ni upgrade. This is due to the deportment of Ni across several gangue host mineral phases (i.e. Fe oxide/hydroxide and a range of silicate/aluminosilicate minerals). From chemical analysis, after disaggregation of ~ 1% Ni grade feed ore, coarse (-600 + 38 µm) and fine (-38 µm) fractions of ~0.6% and 1.3% Ni grades respectively, were also produced, suggesting that a significant upgrade in Ni content can be achieved by rejecting the + 38 µm fraction with the loss of <40% of the Ni. The ore mineralogy, particularly the complexity and high number of un-liberated Ni-bearing phases, greatly compromises physical separation methods for these ores, with the possible exception of screening after disaggregation of the fines inherent in the run of mine ores.

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

It is well known that the crushing and grinding steps in the mineral processing of ores represent a substantial proportion of total energy, cost and carbon emission in mining. For instance a recent study calculated that 36% of the energy consumed by gold and copper producing mines in Australia was attributable to comminution (Ballantyne et al, 2012). Understanding this component of a business is essential in a world seeking to lower production costs, improve earnings and reduce its carbon footprint. The issue commands the attention and support of industry leaders in the mining sector, government, equipment manufacture, engineering design and research organizations. Furthermore, several researchers have often stated that globally, comminution processes consume between 3-4% of the world?s electrical energy production (Daniel and Lewis-Gray, 2011). In 2009-10, Australia?s Federal Government Energy Efficiency Opportunity (EEO) participants in the mining sector used 336.5 PJ, representing approximately 6 percent of Australia&apos;s total energy use. It is evident that the current practices of breaking rocks in tumbling mills are relatively inefficient (Fuerstenau and Abouzeid, 2002). Research and improved engineering design has established that a range of improved blasting, crushing and grinding techniques and flow sheets may lower project costs and carbon footprint. These include relatively simple process flow sheet strategies such as gangue rejection or pre-concentration prior to size reduction, a better combination of grinding technologies (both current and new systems), and selection of coarser grind sizes where ore and waste mineralogy allow. Yet, despite this systematic and detailed research, the industry remains somewhat reluctant to implement these strategies. CEEC (Coalition for Eco-Efficient Comminution) was established in 2011 to support knowledge sharing and change in an area of high-energy consumption for the global mineral industry. CEEC is a not-for-profit industry company, funded by grants from world wide industry companies, whose mission is to accelerate knowledge and technology transfer in the field of energy-efficient comminution. The key benefit to the mining sector arising from CEEC?s activities will be an increase in the rate at which more energy-efficient comminution data sets, processes, and technologies are developed, demonstrated, shared and applied. This will contribute directly to the industry?s target of reducing operating costs and carbon emissions. CEEC International Ltd and JKTech Pty Ltd teamed together to facilitate the inaugural CEEC Workshop, in June 2012. The purpose of the workshop was to produce a roadmap to provide guidelines for how (1) operations can achieve best EEC practice in the short to medium term, in collaboration with vendors, engineering companies and other service providers, and (2) what R&D is needed to achieve paradigm change in EEC in the medium to long term, e.g. 75% reduction in comminution energy in 10 years.

Sep 1, 2012

By Peter J. Scales

The recovery of water for re-use in minerals processing is an important issue in the reduction of water use in mining, as is the dewatering of tailings to reduce the propensity of ?wet? tailings dams. It is common in these dewatering operations to use thickeners whereby polymeric flocculants are combined with the dilute feed to the thickener to aid sedimentation and the subsequent consolidation of particulate materials. Thickeners are the workhorses of water recovery and tailings dewatering and although the basics are well understood, there is still no ability to reliably predict the throughput and underflow density from a thickener based on traditional sedimentation tests and flux analysis. The reasons for the discrepancy between full-scale operations and predictions based on laboratory tests are numerous, including difficulties in mimicking the flocculation conditions experienced in the field and the shear conditions in the thickener. The latter effects are little understood and hard to quantify and include effects due to flocculated aggregate densification, complimentary shear and compressional effects and aggregate break-up. Developing a set of test protocols to quantify the effects of densification, shear in compression effects and aggregate breakup and the subsequent contributions of each to compressional dewatering in a thickening environment has been completed for a simple model polymer flocculated particulate suspension. The data and analysis shows that aggregate densification is a dominant contributor to the difference between observed and predicted behavior based on laboratory tests. A major consideration in the analysis is the fact that common thickener operations are permeability limited and although the various effects are all important, the one that results in the fastest water release is dominant. Of interest also are the shear rate, concentration, and time dependence of the aggregate densification process. A basic model of the process has been developed along with network yielding tests conducted using rheometry. Keywords: compressional dewatering, gravity thickening, rheometry, aggregate densification, raked batch settling

Sep 1, 2012

By Liu Jie

Refractory iron ore deposits in China have various genesis and complicated types, the nature of which is poor, fine-disseminated and complex. Therefore, refractory iron ore could scarcely be separated and utilized by traditional mineral processing technology at present. It is necessary to explore deep reduction technology to change the characteristics of refractory iron ore and to use effectively the iron resource. And deep reduction technology is that on the condition of higher reduction temperature than that of magnetic roasting and stronger reducing atmosphere, the iron oxides from iron ore was reduced to metallic iron particle that is easy to dissociate. And then production from deep reduction is easily separated by magnetic separation and iron powder production was obtained finally. Deep reduction technology for Lingyang iron ore from Jilin, China, as the refractory iron ore, was studied in this paper. The influences of such main factors as reduction temperature, time and coal content were investigated. The results showed that the Metallization rate of reduction product was up to more than 90% under optimum conditions, and then higher iron grade and recovery of reduction iron powder were obtained from subsequent magnetic separation. Furthermore, the deep reduction mechanism in the system was studied by the means of XRD and SEM analysis for reduction production and Physical Chemistry of Metallurgy. Analytical results indicated that during deep reduction, the size of iron particle from deep reduction materials was increasing as reduction temperature rising and reduction time extending. The growth of metallic iron particle from deep reduction production was divided into such three stages as reduction nucleation, deep reduction and growth of metallic iron particle.

Sep 1, 2012

By S. Narra, M. Nelles, I. Eickhoff, S. Teitge

"The aim of the research is to develop a holistic process flow for the recycling of glass fibres from glass reinforced plastics (GRP) and carbon fibres from carbon fibre reinforced plastics (CFRP), wherein the dissolution of the fibre epoxy resin matrix, separation of fibre fractions and their renewed material use is intended. In clear distinction to the previous research and development projects, the aim here is to recycle complex composite structures such as dismantled/disused wind turbine rotor blades and end-of-life composite wastes. In the course of the study, mechanical, hydrothermal and thermal processes and their combined procedures will be developed. As the fibre length is a decisive quality criterion in the recycling of composite materials, the further focus of the study will be the development of upstream and downstream material processing, in which the fibres are retained in their original form. The evaluation of the recycled fibres obtained is based on the elemental composition, measurement and morphological evaluation of individual filaments by scanning electron microscope (SEM), micro tensile tests on single fibres and their comparison to virgin fibres. The resulting process water is analysed by gas chromatography and mass spectroscopy (GC-MS) and a potential recirculation is determined. In cooperation with companies from the composite processing industry as well as recycling companies, a return of the recycled fibres to the known manufacturing process will be examined and an energetic and economic evaluation of the overall process will be carried out. Ambitious aim of the study is to achieve an actual recycling instead of the present downcycling or the energetic utilization. INTRODUCTION As global warming increases, so does the awareness of consumption and production of energy. To counteract the effects of global warming, renewable energy has been increasingly used during the last two decades, not only in Germany, but worldwide. Both, hydropower and wind energy, hereby play a fundamental role. After the end of their useful life of 20 to 30 years, the wind turbines (WTs) are being dismantled. Due to their foundations and tower segments, their recycling rate hereby exceeds 90% by mass. So far, the resulting rotor blade waste played a minor role accounting for only 2 - 3 weight-% of the total plant. Rotor blades of modern wind turbines are made of glass and carbon fibers, which are embedded in an epoxy or polyester resin matrix, balsa wood, PU or PET foams as fillers as well as various paints and coatings. These wastes currently end up in waste incineration or are sold to non-European countries."

Jan 1, 2018

By Ye Chen, Jianhua Chen, Meng Liu, Yuqiong Li, Xiao Mu, Cuihua Zhao

"Sulfidization-amine is the most effective method for the recovery of smithsonite (ZnCO3), however the interface interaction details remain unclear. The sulfidization-amine flotation mechanism of smithsonite has been studied by Density Functional based Tight Binding (DFTB+) method in this paper. The slab model of ZnCO3 (101) surface was built and the adsorptions of a monolayer of HS- and S2- ions were conducted to model the sulfidization effect on the ZnCO3 (101) surface adsorption. DDA hardly interacts with the hydrated ZnCO3 (101) surface. Under the low concentration of Na2S, HS- ions form a Zn-SH-SH structure on the ZnCO3 (101) surface, which hinders the interaction between DDA and surface Zn atoms. Under the high concentration of Na2S, a layer of ZnS is formed on ZnCO3 (101) surface, which is favorable for the adsorption of DDA on the surface. This is consistent with the flotation practice where smithsonite flotation requires a large amount of sodium sulfide. The results could provide a microscopic investigation into the sulfidization-amine flotation mechanism of smithsonite.INTRODUCTIONSmithsonite (ZnCO3) is an important and typical oxide mineral of zinc. It is a semi-soluble salt mineral with a solubility product constant of 1.46 × 10-10 (Weast, 1973). The most common and effective method to recover oxidized zinc ores is froth flotation (Caproni et al., 1979; Pereia and Peres, 2005; Kashani and Rashchi, 2008). It is well known that the flotation of oxidized zinc minerals is much more difficult than the flotation of zinc sulphide minerals (Hosseini and Forssberg, 2007).The recovery of zinc oxide ores with poor floatability attracts more and more attention due to the depletion of easy-recovered of zinc sulfide ores.Sulfidization-amine flotation, which using Na2S as sufidizing agent and amine as collector (Mckenna et al., 1949; Rey, 1954; Abramov, 1961; Rey, 1979; Hosseini and Forssberg, 2007). This method is the most successful technology used for zinc oxide minerals flotation in large-scale industrial applications since it was invented in the 1950s (Önal et al., 2005; Pereira and Peres, 2005). There have been numerous experimental researches on the sulfidization-amine flotation of smithsonite. Shi et al., (2013) studied solution chemistry of smithsonite flotation system. Feng and Wen (2017) studied the formation of zinc sulfide species on smithsonite surfaces and its response to flotation performance. Wu et al., (2017) investigated the sulfidization behavior of smithsonite with the use of zeta potential, inductively coupled plasma (ICP), scanning electron microscope (SEM), and X-ray photoelectron spectroscopic (XPS). Their measurement results confirms the chemisorption of sulfur ions and the formation of ZnS film on the smithsonite surface after Na2S treatment, however the influence of HS- ions on the surface and the influence of sulfidization on the amine adsorption have not been discussed."

Jan 1, 2018

By E. Alldén Öberg

In 2004, LKAB decided to start a basic engineering study in expanding its existing production lines at the Malmberget mine site. It was expected that some of the production lines would become bottlenecks with reference to capacity. In this study, the sorting plant is examined and the results show that several unit operations will be limiting under current operating conditions. An additional purpose with the study was to investigate how replacement of some machines would influence performance and if production plans for the coming years might be achieved. Steady-state simulations using the software Modsim? were extensively used to study process performance for different operating conditions, such as iron content and size distribution in run-of-mine ore. Model parameters were derived from pilot plant data and when possible from ex-isting circuits. A complication for the simulations was the lack of relevant data and therefore some of the initial results were only indicative. The result shows that installation of new screens would give a much better operation, but also new crushers would be an improvement. This, since they can be run with full crusher chamber and tighter CSS. During 2007, most of the proposed remedies were implemented and the result is that the bottle-necks are gone, and the grades and material balances are even better than what was envisioned from the simulations.

Jan 1, 2014

By M. E. Taranenko, V. A. Krivonosov, S. A. Nemykin

"In concentrating production energy-consuming power installations are wide used, the most powerful of them are the wet autogenous grinding mill operating in closed circuit with a spiral classifier. The analysis of the current state of the automation of the grinding process shows that the reserves for maximizing productivity and minimizing electricity consumption have not yet been exhausted on the existing process equipment. Usage of the achievements of the modern management theory reveals an opportunity for further optimizing of the grinding process. The purpose of the research is to develop an automated control system of complex ""the mill-classifier"" to conduct the grinding process in the most operating efficiency, ensuring the maximization of productivity and minimization of specific electricity consumption. The main idea of this work is to study the specific features of the ore grinding process and creation on this basis of automated control system complex ""mill-classifier"" which allows to find and to maintain the optimal mode of grinding based on identification of the current object parameters, observance and regulating of the object state coordinates. Research methods. We used the methods of system analysis, mathematical statistics, modern automated control theory, theory of systems identification, optimal control, modelling of dynamic processes. Developed scientific provisions: - identification algorithm of the loading sub-system management object of complex ""mill - classifier"" allowing to obtain the unbiased estimators of its parameters according to the data of normal object exploitation; - observing device, which differs from the classic version of the observer Luenberger with possibility of estimating not only the state coordinates of the control object, but also the low-frequency perturbation component; - automated system stabilizing the active power of the grinding mode on the basis of a states controller with Luenberger observer; - structure of the software and hardware that implements the developed models, algorithms, methods of control, management and optimization in the framework of the automation of grinding."

Jan 1, 2018

By Rasool Hejazi

The feed to Chadurmalu iron ore concentrator plant is a mixture of magnetite and haematite iron ore with a Fe/FeO ratio of about 8. The feed to plant, after grinding via wet SAG mill, is pre-separated by wet low intensity magnetic separator. Magnetic product is conducted to magnetite processing circuit for producing magnetite concentrate, and nonmagnetic product is directed to haematite processing circuit. Due to surface oxidization of magnetite particles and a decrease in magnetic attraction properties, significant amount of these particles are misled to tailing which results in decreasing the efficiency of haematite processing circuit. This problem can be remedied by using magnetic drum separator with more magnetic intensity and/or gradient. In this paper, the replacement of LIMS separators with wet medium intensity magnetic separators with a field intensity of 3800 gauss on drum surface (MIMS) have been suggested and considered as the most suitable solution to prevent the loss of magnetite particles. The results of carried out investigations with replacement of drum separators in industrial scale, showed that utilizing MIMS in magnetite processing circuit resulted in increasing final concentrate weight recovery on average by 2.59%, without any adverse effect on the concentrate quality; decreasing the magnetite content in the feed to high gradient magnetic separator (HGMS) by about 3.5%; decreasing the feed to floatation part by about 7% and consequently decreasing consumption of chemical reagents; increasing Fe/FeO ratio of the feed to plant. Keywords: iron ore, medium intensity magnetic separator, haematite, Chadurmalu

Sep 1, 2012

By C. Y. Wang

Anodic reaction mechanism of complicated antimony-lead concentrate in Slurry Electrolysis has been investigated by the anodic polarization curves determined under various conditions. The main reactions on the anode are the oxidation of FeCln (2-n), though the oxidation of jamesonite particle on the anode can occur during the whole process, it is less. With the help of mineralogy study and relevant tests, the leaching reaction mechanism of jamesonite and gudmundite during Slurry Electroly-sis has been ascertained also. Because of the oxidation reaction of FeCl3 produced by antimony-lead concentrate itself, the non-oxidation complex acid dissolution of jamesonite, the oxidation complex acid dissolution of gudmundite, and the oxidation of air carried by stirring, the leaching ratio of antimony reaches to about 35% when using HCl-NH4Cl solution to leach antimony-lead concentrate directly. So given the theoretical electric quantity, which to oxide antimony in Slurry Electrolysis, all of antimony, lead and iron, which contained in antimony-lead concentrate, are leached.

Jan 1, 2014

By Matti Kongas, Kari Saloheimo, Antti Remes

"The paper studies the control performance of the flotation process as a function of the measurement accuracy and sampling frequency of an on-stream XRF analyzer, using a simple dynamic model. An additional aim is to assess how the economical result of a mineral flotation process depends on the quality of process control based on the on-line elemental assays.An on-stream XRF analyzer measures the concentrations of slurry lines in a continuous cycle from several process points. The control performance depends on the analytical accuracy and sampling frequency of the concentration measurement. With a long cycle time, the state of the process changes before a new measurement becomes available. With short measurement times the statistical variance of the counted X-ray pulses increases, increasing the random error in the analysis. In addition, the measurement accuracy depends on the concentration of the component to be measured from the slurry.To quantify the effect of analysis error and frequency to process control, a simple dynamic process model is created in the Matlab environment. Data from a copper flotation circuit is used as a test case. The process model comprises a first order reaction equation and the grade-recovery -relationship estimated from process data. The control was modeled using the control strategies implemented into a rule based advanced control system.The economical performance of the control was studied by calculating the overall net smelter return at various analyzer parameter combinations. The economical performance of the process declines strongly when the sampling cycle is increased. In studied case the sample measurement time did not have a significant effect on the results. The economical performance of the simulated process corresponds to an almost uncontrolled process when sampling cycles longer than 40 min are applied."

Jan 1, 2003

By Scott C. Brown, Brij M. Moudgil, Ivan U. Vakarelski

The manipulation of the apparent hydrophobicity of particlute surfaces is necessary to achieve optimal selectivity in flotation processes. Previously a number of works have investigated the role of microscale surface and particulate morphologies on chemically modified substrates. These works have suggested that microscale surface asperities lead to an increase in flotation efficiency by assisting in the rupture of wetting films. Yet, in mineral processing the presence of surface asperities may lead to a reduction in flotation. The reason for this may-in part-be due to the presence of nanoscale irregularities at the interface. In this work, it is proposed that the presence of roughness at the nanoscale may have a dominant impact on the apparent hydrophobicity of mineral surfaces during flotation. It is suggested that as inter-asperity seperation distances are reduced capillary effects are enhanced for high energy mineral surfaces leading to the formation of liquid domains, which adversely impact hydrophobicity. In addition, as these distances approach the surfactant headgroup size obstruction of surfactant self-assembly process may occur, thereby further limiting flotation.

Jan 1, 2003

By Yimin Zhu

This paper introduces the sixteen mappings and rules of mineral flotation and the subgroup, period etc in periodic table of chemical element to provide mineral flotation workers to refer in theory and practice research. the nine mappings and rules of mineral flotation and the subgroup, period are Saline minerals including the first main groups and collectors of aliphatic acid and aliphatic amines, Minerals including the second main group elements and collector of aliphatic acid, Hydrated ion of the second main group elements and quartz flotation, The floatability of oxidized minerals including the four main group elements, Organic acid including the fifth main group elements and wolframe, tin flotation collectors, The floatability of sulfide minerals including the fifth main group elements, Inorganic compounds including the seventh main group elements and mineral flotation regulator, Oxidized minerals including the forth Subgroup elements and organic flotation agents with phosphorus and arsenic, Oxidized minerals including the fifth subgroup elements and organic floating agents including the fifth main group elements, Minerals including the first subgroup elements and CN-, Sulfide minerals including the second subgroup elements and CN-, The effect of the highest N-valency inorganic acids or salts including p area elements of the third period in mineral flotation, Oxidized minerals including transition elements of the forth period and 3# flocculating agent, The floatability of minerals including elements of the sixth period, Element area of generating compositions and the collecting theory of mineral flotation and so and. Keywords: mineral flotation, periodic table of chemical element, subgroup, period, regulator, coordination chemistry

Sep 1, 2012

By C. Tokoro

Co-precipitation of dilute toxic anions with ferrihydrite is an important removal mechanism in wastewater treatment system. Although, numerous qualitative studies have been published on removal characteristic from wastewater of dilute anions by co-precipitation treatment, detail mechanism or quantitative characteristic is not well understood. This paper discussed the co-precipitation mechanism of As(V) and Cr(VI) with ferrihydrite by comparative experiments between co-precipitation and simple adsorption. In this study, co-precipitation experiments and simple adsorption ones were distinguished closely. In the former, precipitation of hydroxides and adsorption of anions develop simultaneously, but in the latter, anions adsorb onto prepared hydroxides. Although high affinity anions for hydroxides (e.g. As(V) for ferrihydrite) showed quantitative difference of removal ratio between co-precipitation experiments and simple adsorption ones, low affinity anions (e.g. Cr(VI) for ferrihydrite) showed quantitative agreement in spite of deferent forms of ferrihydrites between them, that is, amorphous ferrihydrite was formed in co-precipitation experiments, but goethite was formed in simple adsorption ones. In order to discuss the mechanism of co-precipitation phenomena, three experimental studies have been carried out: (i) adsorption isotherm measurement in the co-precipitation experiments of As(V) or Cr(VI) with ferrihydrite, (ii) zeta potential measurement of co-precipitated or simple ad-sorbed ferrihydrite with As(V) or Cr(VI), and (iii) XRD analysis of co-precipitated As(V) for ferrihydrite. All experimental results suggested the main mechanism in co-precipitation phenomena of As(V) was not only a surface complexation (simple adsorption) but also a surface precipitation.

Jan 1, 2014

By A. Lewis

"Thiol collectors including the xanthates and dithiophosphates have dominated the sulfide mineral processing industry for over a century. Tecflote represents completely different chemistry, without sulfur or phosphorus, and will float all sulfides and associated precious metals. As these collectors are surfactant in nature, they comprise a head group which binds to mineral surfaces, a spacer and a long hydrophobic tail. The modification of the spacer behind the head group allows for collector optimisation for different sulfide ore types and process conditions.The Tecflote surfactants have been designed to be either very selective against pyrite at the natural pH of the ore (pH 7-9) or to float all sulfides including pyrite. Depending on the ore type and the process flow sheet, the use of lime can be maintained, reduced or completely eliminated.Tecflote can be used either as a rougher collector giving good recovery and grade for the sulfide minerals or it can be used to target valuable minerals after regrind and through cleaner flotation. It has repeatedly shown to be very effective at holding onto gold through the cleaner steps. The low solubility has a significant impact on the mechanism and surface activity of the collector, resulting in a very different flotation response compared to conventional thiol collectors.INTRODUCTIONXanthate was first made in 1882 by Zeise and first used in flotation in 1924 (Keller, 2018). In 1946 Keller patented thionocarbamate as a collector, which was produced by Dow Chemicals (Keller, 2018). Later it was replaced by Dow product Z-200, while dialkylthionocarbamate was discovered by Harris et al. (Harris, 1954. No significant chemistry change to collectors has occurred since they were introduced in the mid-20th century and now that the feed grades have been declining over the last decades creating a need to find more selective collectors to extract difficult and complex ores and pushing the industry to look at other reagents."

Jan 1, 2018

By Kaiwen Liu

Activated carbon is widely used in the removal of organic and/or inorganic contaminants from waste water due to its high surface area, porous structure, and specific surface reactivity. However, in practical applications, it is difficult to recover the activated carbon completely by screening or classification. In this project,we prepared a magnetic form of activated carbon (magnetic activated carbon or M-AC) by precipitation of iron oxides on the surface of activated carbon. The M-AC can be easily separated from effluents by applying an external magnetic field, thus it can be recycled and regenerated for reuse. M-AC was characterized by X-ray diffraction (XRD), specific surface area measurement, and scanning electron microscope (SEM).XRD results show that the major phase of coated iron oxides on activated carbon is magnetite (Fe3O4). The specific surface area of activated carbon was found to be reduced after the impregnation of magnetite particles on the surface. The SEM micrograph shows the aggregation of the iron oxides on the surface of activated carbon. M-ACwas found effective in removing DETA (diethylenetriamine) species and metal ions from solutions. Cu (II) with initial concentrations from 5 ppm to25 ppm in solution is removed by more than 99% with the addition of 0.1 wt.%ofM-AC. For the removal of 25 ppm DETA species from solution, an addition of 0.5 wt.% of M-AC is required due to the larger size of the DETA molecule. Moreover, M-AC showed a good loadingproperty for nickel and gold ions from solutions. M-ACshows a better adsorption capacityover activated carbon and its potential applications in carbon-in-pulp for gold leaching and waste water treatment. Keywords: magnetic activated carbon (M-AC),diethylenetriamine (DETA),metal ion,adsorption

Sep 1, 2012

By E. Szelag

The adsorption and stabilization of mineral dispersed systems by using Pluronic copolymers with different molecular weights and EO content has been studied. The role of sequential adsorption of EO-PO copolymers and cationic surfactant (CTAB) on the carbonate particle properties and in determining the stability of their suspension was studied with particular attention to the conformation of the polymer at the solid-liquid interface. The purpose of this work was to investigate the flocculation phenomena, influence of polymer molecular size on stability of suspensions of magnesite and dolomite and the effect of addition mode of polymer and surfactant. The suspension stability measurements and the determination of sedimentation speed were carried out using an optical analyser (Turbiscan). In most of investigated cases, the biggest floccs and the fastest sedimentation were found for low concentrations of copolymers.

Jan 1, 2014