Sodium oleate (NaOl) has been widely used as a collector for the scheelite flotation. However, low selectivity of NaOl and large amount of sodium silicate (SS) needed remain tough problems. In this study, octyl hydroxamic acid (HXMA-8) was used as an associate collector with NaOl in scheelite flotation. The flotation tests showed that a novel reagent scheme, i.e., a lower dosage of SS (300 mg/L) and mixed collectors of HXMA-8 + NaOl (total concentration 4.5 × 10 mol/L, preferred mass ratio of 1:2) achieved the selective separation of scheelite from calcite. Zeta potential measurements indicated that the depressant, SS, adsorbed more strongly on calcite surface than on scheelite surface. HXMA-8 adsorbed significantly on scheelite surface either in the absence or presence of SS by chemical bonding between oxygens of HXMA-8 and surface metal ions. NaOl also adsorbed on both mineral surfaces by chemisorption, but the adsorption on calcite surface was influenced adversely by the presence of SS.
The adsorption behaviour of natural zeolite (clinoptilolite) has been studied in order to determine its applicability in treating acid mine drainage (AMD) containing 400, 20, 20 and 120 mgl of Fe , Cu , Mn and Zn respectively. Tests to determine both the rate of adsorption and the uptake at equilibrium were performed under batch conditions from single and multi-component solutions. The optimum conditions for the treatment process were investigated by observing the influence of pH levels, the presence of competing ions, varying the mass of zeolite and thermal modification of the natural zeolite (calcination and microwaves). The adsorption studies showed rapid uptake in general for the first 40 mins, corresponding to ∼ 80% total removal. After this initial rapid period, the rate of adsorption decreases. According to the equilibrium studies, the selectivity sequence can be given as Fe > Zn > Cu > Mn , with good fits being obtained using Langmuir and Freundlich adsorption isotherms. Preliminary tests using AMD samples from Wheal Jane Mine, UK, showed that natural zeolite has great potential as an alternative low cost material in the treatment of acid mine drainage.
The similar flotability of scheelite, fluorite, and calcite resulted in the difficult separation by flotation. This work revealed the effect of water glass on the flotation of scheelite by FTIR and the wettability change of the usual cleavage plane, and proved that water glass inevitably influenced the flotation of tungsten minerals to a large extent in traditional fatty acid flotation process. A new collector, lead complexes of benzohydroxamic acid, was found to be selective for the separation of scheelite and calcium minerals with little water glass. Hence a novel flotation process was developed for the recovery of tungsten minerals in Shizhuyuan Mine in China. Normal temperature flotation of tungsten minerals was developed to instead of the classical “Petrov's process” for scheelite-calcite-fluorite type ores. Compared with the traditional process, the recovery was improved by almost 10% and the grade of scheelite concentrate was above 55%. The disappearance or decreasing of water glass contributed to improving the recovery of tungsten and the circulation of water and reagents.
Flotation is the most effective solution, both technologically and economically, when upgrading iron concentrates. Research regarding iron ore flotation began in 1931, demonstrating that reverse cationic flotation is a very efficient method for beneficiating oxidised iron ores. This method can also be applied to reduce the silica content in magnetite concentrates obtained using wet low-intensity magnetic separation. Several studies describing the processing of iron ores via reverse cationic flotation are reviewed. The predominate role of the pulp mineralogy, as well as the type and molecular structures of the collectors and depressants, on flotation is discussed critically. The results concerning the role of the silicate mineralogy on the choice of reagents and flotation processes are also discussed. Further development of the reverse cationic flotation of iron ores requires a more detailed consideration of the nature of iron-bearing gangue minerals and the application of original approaches for the selective removal of these species.
This paper provides an overview of the various processes used in the recovery of platinum group metals (PGMs) from spent catalysts. PGM recovery is interesting due to their vast industrial applications and high market prices. From the use of renewable resources and environmental protection viewpoints, recycling of PGMs receives wide concerns as the amounts of spent catalyst increases dramatically. PGM recovery from spent catalysts is a challenge due to the fact that spent catalysts are diverse and complex in terms of material and component makeup as well as the original catalyst's manufacturing processes. The state of the art recovery of PGMs from spent catalysts by pyrometallurgy and hydrometallurgy techniques is highlighted and existing advantages and disadvantages of these techniques are analyzed in this paper. This review also pointed out that the promising processes of PGM recovery are economical, environmentally friendly and large-scale means.
Bauxite residue (red mud) is a solid waste produced in the process of alumina extraction from bauxite. More than 70 million tons of bauxite residue is generated annually. Presently, it is stored on land or in the ocean near alumina refineries. However, its high alkalinity is a potential pollution to water, land and air of close proximity. Meanwhile high costs are associated with the large area of land needed for storage of the residue. China is amongst the major producers of alumina in the world. There are some differences between the residues from China and other countries due to differences in ore type and production processes. Significant achievements in treatment and utilization of bauxite residues have been obtained in China in the last decade. In this paper, the properties of bauxite residues generated in China are analyzed and significant aspects to treat and utilize residues from the sintering process and the Bayer process are introduced (e.g., storage, preparation of building materials, application in environmental materials, and recovery of valuable elements). Problems associated with the commercial application of these research achievements are considered.
Experimental studies of flotation of quartz particles, under various conditions and cells (setups), are presented. Pure and well-characterized quartz samples were treated with a commercial alkyl ether monoamine as flotation collector with bubbles in various sizes: coarse bubbles (400–800 μm); nanobubbles (200–720 nm); and their mixtures. The nanobubbles were generated by selective separation from microbubbles, which are formed together after depressurizing-cavitation of the saturated water in air (as in pressure flotation or dissolved air flotation), at 66.1 psi saturation pressure. Flotation with single nanobubbles was not effective due to their very low lifting power or practically nil buoyancy. Yet, size-by-size flotation recoveries with coarse plus nanobubbles, compared with coarse bubbles, enhanced by 20–30 % the very fine quartz fractions by 20–30% (8–74 μm; Sauter diameter—D ) and slightly lowered the recoveries of coarse particles (67–118 μm; D diameter). Flotation of quartz samples (composites) having wide particle size distribution and results in a mechanical cell validated the overall recovery enhancement of the fines. Fine particle capture (nanobubbles enhanced the contact angle of quartz) and aggregation of the quartz ultrafines (proved with micrographs) by the nanobubbles are the main mechanisms responsible for the higher recoveries. The effect on flotation of the coarser quartz fractions, at bench scale, may be explained in terms of a reduced rising velocity of the coarse bubbles, in the presence of nanobubbles, decreasing the degree of bubble carryover. It is expected that the use of collector-coated nanobubbles (tailor-made “bubble-collectors” and flocculants) will broaden options in fine mineral flotation. The future sustainable forms (cheaply produced) of nanobubble generation on a large scale and their injection in cells are envisaged.
Calcite, in most cases, is the major gangue mineral found in scheelite ores. It is difficult to separate scheelite and calcite due to the similarities in their formation properties. In this study, it was found that scheelite and calcite can be floated using fatty-acid collector oxidized paraffin soap in the pH regions of 8–11 and 6–12, respectively. The effects of sodium hexametaphosphate (SHMP), tanning extract, starch and acidified water glass (AWG) as depressants of calcite have been studied. The AWG was the appropriate depressant without imposing obvious adverse effects on scheelite flotation. In order to prove the validity of the findings, flotation of both mixed mineral (1:1 scheelite:calcite) and real ore were conducted as well as zeta potential measurements.
A high nickel grade ferronickel was produced from laterite ore using the selective reduction-wet magnetic separation process, with the addition of sodium sulfate (Na SO ). The ferronickel concentrate assaying 9.87% Ni, with a nickel recovery of 90.90% can be obtained, when laterite ore was reduced at 1200 °C for 50 min with the addition of 10 wt.% Na SO and 2 wt.% coal. Based on the results of the X-ray Diffraction, Scanning Electron Microscopy, and Energy Dispersive X-ray Spectroscopy analyses, the thermal decomposition and reduction reaction of Na SO were carried out. Sodium oxide from the thermal decomposition of Na SO reacted with silicate minerals to form nepheline. The formation of the molten phase accelerated the migration rate of the metallic particles and suppressed the reduction of the ferrous minerals in the weak reduction atmosphere. Sulfur reacted with metallic iron to form troilite, thereby facilitating the aggregation of ferronickel particles to form bigger particles.
Research and development into the application of machine vision in froth flotation systems has continued since its introduction in the late 1980s. Machine vision is able to accurately and rapidly extract froth characteristics, both physical (e.g. bubble size) and dynamic (froth velocity) in nature, from digital images and present these results to operators and/or use the results as inputs to process control systems. Currently, machine vision has been implemented on several industrial sites worldwide and the technology continues to benefit from advances in computer technology. Effort continues to be directed into linking concentrate grade with measurable attributes of the froth phase, although this is proving difficult. As a result other extracted variables, such as froth velocity, have to be used to infer process performance. However, despite more than 20 years of development, a long-term, fully automated control system using machine vision is yet to materialise. In this review, the various methods of data extraction from images are investigated and the associated challenges facing each method discussed. This is followed by a look at how machine vision has been implemented into process control structures and a review of some of the commercial froth imaging systems currently available. Lastly, the review assesses future trends and draws several conclusions on the current status of machine vision technology.
The utilization of abundant low-grade iron ores is potentially important to many countries in the word, especially to China. These iron ores contain many detrimental impurities and are difficult to upgrade to make suitable concentrates for the blast furnace. In this paper, the beneficiation of a low-grade hematite ore fines containing carbonates with magnetization roasting and magnetic separation was proposed and studied. The hematite and siderite are almost completely converted into magnetite by 8 wt% coal at roasting temperature of 800 °C for 8 min. Under the optimized conditions, a high grade magnetic concentrate containing 65.4 wt% iron with an iron recovery of 92.7% was achieved. Meanwhile, the effects of roasting temperature, reaction time and coal to ore ratio on the magnetic properties of roasted materials were investigated using a vibration sample magnetometer (VSM). The results show that the magnetic susceptibility and magnetism saturation of hematite ore can be highly increased due to the selective conversion of hematite and siderite into magnetite caused by magnetization roasting which facilitates their separation from non-magnetic minerals.
The froth phase is one of the main components of froth flotation as it defines both the quality of the end product and overall efficiency. The performance of the froth depends on a number of sub-processes that interact in very complex ways, and it is a great research challenge to explicitly name the role of each of these sub-processes. This paper provides a summary of recent studies of flotation froths. The key physical processes operating in the froth are reviewed, and their effect on the behaviour of froth is discussed. The findings in the literature relevant to froth stability are also highlighted in the context of flotation froths. ► This paper provides a summary of recent studies of flotation froths. ► The key physical processes operating in the froth are reviewed. ► The findings in the literature relevant to froth stability are also highlighted.
Red mud is a solid waste produced in the process of alumina production from bauxite following the Bayer process. More than 4 million tons of red mud is generated annually in India only. Presently, it is stored or dumped on land, or in the oceans near alumina refineries. However, its high alkalinity is a potential pollution to threat water, land and air. While high costs are associated with the large area of land required for storage of the residue. India is amongst the major producers of alumina in the world. There are some differences in mineralogical composition between the residues from India and other countries due to the difference in the ore type in its production processes. Significant achievements in treatment and utilization of red mud have been obtained in India in the last decade. In this paper, the various proposals for the utilization of red mud generated in India are presented. Similarly, the drawbacks associated with these potential commercial applications of red mud are discussed. Graphical presentation of red mud from generation to application. ► A brief presentation on the resources and utilization of red mud in India and world. ► Various methods for the utilization of red mud in focus to industrial aspects. ► Various approaches in bulk and powder utilization open up the possibilities.
The last few decades have seen major advances in instrumentation and technology, and simplifications and modifications of new flotation plant designs. This has allowed for significant developments in process control. In particular, the development of base level process control (control of pulp levels, air flowrates, reagent dosing, etc.) has seen significant progress. Long-term, automated advanced and optimising flotation control strategies have, however, been more difficult to implement. It is hoped that this will change as a result of the development of new technologies such as machine vision and the measurement of new control variables, such as air recovery. This review looks at each of the four essential levels of process control (instrumentation, base level flotation control, advanced flotation control and optimising flotation control) and examines current and future trends within each sub-level. ► Literature of instrumentation used in flotation control. ► A review of base-level (regulatory) process control in froth flotation processes. ► A review of stabilising flotation control, and optimising flotation control methods. ► Review of implementation of ‘newer’ technologies into flotation process control including machine vision and froth stability.
The present understanding of the surface chemistry of acidic ferric sulphate dissolution of chalcopyrite is critically reviewed with regard to hindered dissolution and how the hydrometallurgical limitations, especially for microbial heap leaching operations, might be overcome. In particular the surface science investigations of what surface phases might be responsible for hindered dissolution are reviewed. Some other mechanistic issues are also considered which require further investigation. The possible phase candidates for hindered dissolution are examined, with most discussion focussed on elemental sulphur and jarosites. Phases such as polysulphides are rejected as candidates. The physical reality of metal-deficient sulphides is also questioned. A conceptual 4-stage model is proposed which explains all the general dissolution behaviour that is widely observed, i.e. of an induction period and a parabolic rate curve that may or may not be followed by linear rate behaviour. The general conclusion is that thick over-layers of sulphur cause the initial parabolic behaviour, and a thin systemic sulphur layer is responsible for the rate-limiting step, even in the linear region. Depending upon solution conditions, either unhindered near linear dissolution may occur, or jarosite precipitation that will cause a second parabolic region. Sulphur formation remains a systemic phase in the context of heap bioleaching but is not a problem of any consequence for mixed culture systems unlike jarosites. Suggestions are made as to a low-cost jarosite precipitation pond for iron removal and advantages that could result.
The significant coagulation delay and poor strength performance of cemented paste backfill (CPB) are two of the biggest challenges faced by the backfilling system in Chihong mine. These factors significantly affect the mining and backfill cycle. Hence, CPB property tests (e.g., slump, coagulation, and strength) were conducted to investigate the influence of different cement types and mixing water qualities (tailings pore water and distilled water). Results of the tests for slump, initial coagulation time (ICT), and unconfined compressive strength (UCS) of the CPB samples are as follows: (i) slump variation of different CPB samples is insignificant. (ii) The ICT changing trends of the CPB samples are in line with the ICT of their mixing cement slurry. In addition, zinc ions in the tailings pore water are detrimental to CPB coagulation. (iii) Cement has an obvious influence on the UCS of CPB, and water quality barely affects the UCS of CPB. These results indicate that cement choice and water chemical components are important factors in CPB design and mine operations.
Reverse anionic flotation of carbonate-containing iron ores is quite a challenging process. Studies on this ores conducted in many laboratories or beneficiation plants have obtained poor concentrate grades and separation between quartz and iron minerals, even when valuable minerals are adequately liberated. The presence of carbonate minerals, such as siderite, causes a detrimental effect on quartz flotation recovery (froth product) and separation selectivity between quartz and iron minerals. In this work, the effect of carbonate minerals on quartz flotation from iron mineral was investigated using sodium oleate as collector, starch and calcium as regulators. Microflotation, adsorption, PHREEQC calculation, and Fourier transform infrared spectroscopy (FTIR) measurements were conducted in the investigation. Carbonate minerals (i.e., siderite and dolomite) adversely affected the floatability of quartz and separation between quartz and hematite. Starch dosage experiment results clearly showed that the reduction of quartz recovery in the presence of carbonate minerals was mainly related to starch. In addition, mineral dissolution and sodium carbonate dosage experiments evidently exhibited that CO dissolved species of carbonate minerals passively affected quartz flotation recovery. By contrast, both starch and CO dissolved species of carbonate minerals adversely affected the flotation recovery. FTIR showed that the strong drop-off in quartz recovery in the presence of carbonate minerals was due to the adsorption of CaCO precipitations on quartz surfaces and further their interaction with starch molecules. The appearance of CaCO precipitations was caused by reaction of Ca from the hydrolysis of CaCl and CO dissolved species of carbonate minerals. To decrease the passive effect, a potential strategy to improve the flotation performance of iron ores that contain carbonate minerals at strong alkaline pH is suggested to remove carbonate minerals before separation between hematite and quartz.
Effects of sodium salts on reduction roasting and Fe–P separation of high-phosphorus oolitic hematite ore were studied in the process of coal-based direct reduction followed by wet magnetic separation. Various parameters, including reducing temperature and time, type and dosage of sodium salts, grinding fineness of magnetic separation feed and magnetic field intensity were investigated. The results of reduction and Fe–P magnetic separation are significantly improved by the addition of sodium sulfate and borax, in comparison with those in the absence of additives. A magnetic concentrate with total iron grade of 92.7% and phosphorus content of 0.09% was obtained from an oolitic hematite ore containing 48.96% iron and 1.61% phosphorus when reduced in the presence of 7.5% sodium sulfate and 1.5% borax and wet magnetic separated under the proper conditions. The results of optical microscopy and X-ray diffraction (XRD) analyses of reduced pellet reveal that metallic iron grains exist in sizes of 10–20 μm and are associated with gangue minerals closely when reduced in the absence of sodium salts. By contrast, the oolitic structure is destroyed and metallic iron grains grow markedly to the mean size of 50 μm when reduced in the presence of sodium sulfate and borax. Sodium salts are capable of destroying the oolitic structure via reacting with gangues, enhancing the reduction of iron oxide and promoting the growth of metallic iron grains during reduction, which is beneficial for Fe–P separation of the oolitic hematite ore.
Modern digital mine planning, plant design and mineral processing operations demand detailed characterisation of the ore and plant feed. Textural parameters, such as mineral liberation size and mineral association, combine with modal mineralogy data to strongly influence mineral processing conditions and recovery. Traditionally, the measurement of these ore characteristics employed the tools of an optical microscope and/or a semi-automated SEM. These methods are time consuming, costly and frequently produce semi-quantitative results from data sets that are too small to be statistically valid. Thus, the results cannot be used reliably and effectively in digital mine planning and design. In the last 10 years, modern SEM-based quantitative mineralogy tools have advanced rapidly with increasing computer power, improved SEM hardware and the development of sophisticated image analysis methods. Texture resolutions can now be submicron and SEM measurement times have reduced to less than an hour for simple analyses, where previously they required many hours. Through image analysis, particle sections are recognised and separated, and the mineral grains within are delineated for discrete X-ray analysis to determine mineralogy. The modern tools not only increase the speed and accuracy of liberation analysis, but also enhance measurement automation. Automated standard collection assists with the setup of new ore types for routine analysis and automated elemental quantification of target minerals enables the tracking of variations in the composition of the minerals of interest. The key to success for any modern SEM-based mineral liberation analysis system is the close integration of BSE image and EDS X-ray analyses. Integration of the SEM-based quantitative mineral liberation analysis with optical microscope, dual beam systems and X-ray tomography will further enrich the analysis results and the derived user experience.
Modem digital mine planning, plant design and mineral processing operations demand detailed characterisation of the ore and plant feed. Textural parameters, such as mineral liberation size and mineral association, combine with modal mineralogy data to strongly influence mineral processing conditions and recovery. Traditionally, the measurement of these ore characteristics employed the tools of an optical microscope and/or a semi-automated SEM. These methods are time consuming, costly and frequently produce semi-quantitative results from data sets that are too small to be statistically valid. Thus, the results cannot be used reliably and effectively in digital mine planning and design. In the last 10 years, modem SEM-based quantitative mineralogy tools have advanced rapidly with increasing computer power, improved SEM hardware and the development of sophisticated image analysis methods. Texture resolutions can now be submicron and SEM measurement times have reduced to less than an hour for simple analyses,, where previously they required many hours. Through image analysis, particle sections are recognised and separated, and the mineral grains within are delineated for discrete Xray analysis to determine mineralogy. The modem tools not only increase the speed and accuracy of liberation analysis, but also enhance measurement automation. Automated standard collection assists with the setup of new ore types for routine analysis and automated elemental quantification of target minerals enables the tracking of variations in the composition of the minerals of interest. The key to success for any modem SEM-based mineral liberation analysis system is the close integration of BSE image and EDS X-ray analyses. Integration of the SEM-based quantitative mineral liberation analysis with optical microscope, dual beam systems and X-ray tomography will further enrich the analysis results and the derived user experience. (C) 2006 Elsevier B.V. All rights reserved.