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By Brian Hart, Liuyin Xia, Staman Dimov

The recovery of rare earth elements (REE) is fast becoming of significant interest globally. Modern research and development programs (outside China) towards the optimization of REE mineral recovery by flotation have been lacking. Due to the mineralogical nature of many hosting deposits, the separation and recovery flotation flowsheets can be very complex. As part of a research project, a selected suite of hydroxamic acid collectors (Naphthoyl, Cyclohexyl, Benzoyl, Octyl, Terta-butyl benzoyl, Salicylic) were tested in order to examine their potential for recovery and selectivity. Micro flotation tests were conducted on a feed sample, recovery and grade of the products were used to evaluate their relative flotation efficiency and selectivity and these results (flotation with the hydroxamate collectors) were compared to a phosphoric acid/sulphonate collector mix(shorten as "mixed"). In the testing, the flotation response with the hydroxamate collectors was significantly better than the "mixed" collectors on freshly ground (no slimes removed) samples. Furthermore the tests revealed that for most of the hydroxamate reagents tested, their dosage requirements to achieve recoveries at the same levels was less than that for the "mixed" reagents. Product assays show that recovery of both La and Ce is significantly better for using the salicylic hydroxamate and that Nb, Y and Zr recovery are favored by using octyl hydroxamate. These results indicate mineral flotation selectivity could be achieved by using selective hydroxamtes. Spectral fingerprinting by TOF-SIMS surface analysis has allowed for the identification of reagent species. TOF-SIMS surface analyses of grains analysis confirmed that REE bearing grains reporting to the concentrates are doing so in response to collector attachment whereas grains reporting to the tails are doing so in response to a lack of collector. The TOF-SIMS surface data bas been used to examine the factors promoting flotation stream partitioning.

Jan 1, 2014

By V. Z. Kozin, E. A. Bekchurina, P. S. Volkov, Yu. P. Morozov, A. S. Komlev

"The current sampling systems of ore flows or concentrates are based on the method of cross sections in point sampling and the method of scooping in reducing. The limited number of point samples in sampling and microsamples in reducing lead to big random and probable systematic errors. The paper defines the principles of sampling, which assure the absence of systematic errors and also provides calculation formulas of probable errors in sampling methods of cross and longitudinal sections as well as in samples preparation. The article sets the fundamental laws of sampling: the dependency of minimal mass of gross sample and number of point samples from mass of point sample in sampling from heterogeneous body; the dependency of a sample minimal mass from lumps’ size in preparation of carefully mixed samples; the dependency of point samples’ dispersion from duration of control period. The paper introduces the fundamental notions: lump variance; probable systematic error; methodical error. It also provides a solution of outstanding sample correct application in analysis results calculations. In application of automatic analyzers, mounted in material flows, the probable error connected with sampling, is calculated by the formulas for carefully mixed sampling bodies. The paper describes the developed and introduced sampling systems on the base of combined application of cross and longitudinal sections methods in sampling and preparation of samples. The advantages of this equipment are compactness, reliability, simplicity in service and operation, and for pulps it is adaptability in pipelines. Application of the developed equipment entirely excludes probable systematic error. The new systems of sampling and preparation of samples are introduced at 25 concentrating plants. Introduction of the developed systems at sampling balance points of concentrating plants allowed double reducing balance deficiency."

Jan 1, 2018

By Anuttam Patra, Romain Bordes, Andreas Fredriksson, Tommy Karlkvist, Krister Holmberg, Kota Hanumantha Rao

The present investigation aims to develop and distinguish mineral specific reagents with two functional groups for use in flotation of calcium containing minerals. For this purpose, a series of dicarboxylate-based surfactants with varying length between the carboxylate groups (one, two or three methylene groups) were synthesized. As reference, a surfactant with the same alkyl chain length but with only one carboxylate group in the polar part was synthesized. The adsorption behavior of these new reagents on pure apatite and calcite mineral surfaces was studied using Hallimond tube flotation, FTIR and ? potential measurements. The relation between the adsorption behavior of a given surfactant on a specific mineral surface and its molecular structure over a range of concentration and pH values, as well as the region of maximum recovery were established. It was found that one of the reagents, with a specific distance between the carboxylate groups, was much more selective for a particular mineral surface than the other homologues synthesized. This selective adsorption of a given surfactant to a particular mineral surface relative to other mineral surfaces as evidenced in flotation studies is substantiated by ? potential and infra-red spectroscopy data.

Jan 1, 2014

By Chao Li, Kym Runge, Saeed Farrokhpay, Dee Bradshaw

"It is well known that froth phase has a controlling influence on the overall flotation performance. Froth recovery is expected to be affected by froth transportation behaviour. The latter has been represented by different volume balance and energy balance based models. In froth transportation models based on a volume balance, the froth phase is divided into different zones. The total froth residence time is the sum of the time spent in each zone and is dependent on the cell geometry, bubble burst rate and the position that bubbles enter into the froth phase. Alternatively, the froth transportation model based on an energy balance treats the froth phase as a block. In this model, froth height above the concentrate lip is being predicted by minimising the energy of the system which is dependent on the froth geometry, froth stability and froth rheology. The froth height can be used to calculate the froth efficiency of delivering mineralized bubbles from the pulp to the concentrate lip. This paper critically analyses the current models of froth transportation in flotation, and examines the limitations of these models. The importance of froth rheology, which is the resistance to the froth flow towards the discharging weir, in determining froth transportation, is also highlighted."

Jan 1, 2014

By l. Bokányi

The Tóth adsorption isotherm-model was derived and has been widely used for the inhomogeneous solid surfaces. The three-parameter isotherm incorporates the effect of the interaction between the adsorbed substances as well. All classic isotherms can be clearly derived from this one. Bio sorption is the sequestering of dissolved components, i.e. metals from aqueous environment by living or dead biomass. The mechanism of the bio sorption is rather complex and predominantly refers to the affinity of the chemical functional groups: acetoamido groups of chitin, structural polysaccharides, amino and phosphate groups in nucleic acids, amino, amido sulfhydryl and carboxyl groups in proteins, hydroxyls in polysaccharides, sulphates, etc. towards the soluted substances, i.e. heavy metal ions. The physisorption, as well as the micro precipitation also play a role in the bio sorption mechanism. The description of such a complex process can be done by a model reflecting this complexity. According to our experimental results obtained using algae and immobilised algae for the sorption of heavy metal cations, the most appropriate model for such a description is the Tóth-isotherm, the parameters of which can be interpreted. Flotation process is also a very complex one, the overall result of which depends on the partial results of many micro processes and parameters. The particle interaction which very often takes place in the flotation systems makes the phenomenon even more complex. The flotation kinetic model with particle interaction was already introduced by author in 1994 and further developed in 2000. In this paper based on the experimental results obtained with metallic particles in case of recycling flotation the applicability of the Tóth-equation as an alternative flotation kinetic model for the systems with particle interaction is proved. The applicability of Tóth-model in mineral processing demonstrates again its universal character and the great talent of the late József Tóth, great Hungarian chemist. Keywords : Toth isotherm, biosorption, Langmuir, Freundlich

Sep 1, 2012

By S. Kelebek, M. Davidson

"Flotation tests were conducted on a mixed copper ore sample containing bornite and malachite with trace quantity of other secondary copper minerals. The bornite component was very floatable, in sharp contrast to poor flotation characteristics of other copper minerals. A Box-Behnken experimental design methodology was used to study effects of three main reagents, namely potassium amyl xanthate (PAX), hydroxamate (Cytec 6494) and diethylenetriamine (DETA). Pine oil, as a frother, was used at a fixed concentration. Three main models constructed using a statistical software included malachite recovery, overall copper recovery, and copper grade. Bornite recovery was not modelled as its recovery was consistently over 99 % in the presence of hydroxamate and PAX. In each model, the hydroxamate dosage was the dominant parameter (at 95% significance level) determining the recovery of main components including that of gangue, which manifested itself by lowering the copper grade of the concentrate. In comparison, PAX was effective only at 90% significance level. DETA did not affect the overall recovery of copper or malachite significantly, but appeared to cause a significant decline in the concentrate grade, especially when used simultaneously with hydroxamate. Various quadratic models developed for the flotation system investigated are presented."

Jan 1, 2014

By Brochot. Stephane, Manuel Gonzalez Fernandez

"HPGR (High-Pressure Grinding Rolls) is widely used today for grinding of various kinds of ores such as iron ore or base and precious metal ores. It can be used as first stage of grinding replacing tertiary crusher and SAG mill, but also as regrinding stage to enhance mineral liberation. In addition to better energy efficiency, the advantage of HPGR is to produce much more internal particle fractures allowing faster leaching as it has been demonstrated for some gold ores. This grinding mode of compression and fracture generation also promotes mineral liberation without overgrinding. Mineral processing modelling and simulation associated to detailed ore characterization constitute a powerful tool for plant design and optimization. The mathematical models of the units of operations (grinding and separation) have to reproduce the mineral deportment for which the mineral liberation plays a central role. The present paper is focused on the HPGR modelling with the objective of plant optimization or advanced design from pilot plant tests. The traditional approach of the population balance linked to the energy dissipation and the residence time distribution is generalized in association with a mineral liberation model. The effect of the specific HPGR breakage matrix and grinding function on the mineral liberation rate is discussed and compared to the tumbling mill. The implementation of this mathematical model into a plant simulation tool is illustrated by the example of the optimization of an iron ore concentrator."

Jan 1, 2014

By Achilles Dutra, Everton Santos, José Oliveira

The beneficiation of phosphate ores by froth flotation is the most efficient process used to separate apatite from gangue minerals like calcite, dolomite and quartz. However, the similarity of surface properties between apatite and calcite generally lead to non-selective adsorption of reagents, rendering the selective separation of these minerals a worldwide problem. The phosphate deposit of Itataia, State of Ceará, Brazil, studied in the present work, presents a complex mineralogical composition having uranium associated with the apatite mineral. The main gangue minerals are calcite and quartz. The bulk flotation of apatite and calcite with anionic collectors in an alkaline medium followed by the selective flotation of calcite at pH 5.5 using phosphoric acid as well as citric acid as depressant have been suggested for this ore. This paper presents the results of contact angle measurements obtained using jojoba oil, a natural reagent composed mainly of gadoleic acid (C20:1) and long-chain fatty alcohols (eicosenol and docosenol), as an alternative collector for the selective separation of apatite and calcite minerals. The hydrophobicity studies were carried out using a computer controlled contact angle goniometer. Additionally, the collector adsorption was evaluated via electrophoretic mobility and FTIR measurements. The results indicated that a high selectivity can be obtained by using jojoba oil as collector in a slightly acid pH range, without the use of depressant. The best results were achieved with a jojoba oil concentration of 200 mg.L-1 at pH 6.5, where the apatite was fully hydrophilic and calcite showed a high hydrophobicity (? > 60 º).

Jan 1, 2014

By M. A. Hampton

The surface oxidation of sulfide minerals in aqueous solutions is an important sub-process in sulfide flotation and hydrometallurgy, but a full understanding of the oxidation process and products is still lacking. Many oxidation pathways and products involving elemental sulfur, metal polysulfide, metal-deficient sulfide and sulfate have been proposed, confirmed and argued. In this paper we provide further insight into the surface electrochemical behaviour of galena in aqueous solutions. For this research we have developed a novel experimental system, that combines chronoamperometry and AC-mode AFM surface imaging, which allows for in-situ, synchronized electrochemical control and examination of oxidative surface morphology. At pH4, the morphology of elemental sulfur (detected by ex-situ Cryo-XPS) formed on the oxidizing galena surface depends on the electrochemical potential pathway. In multi-step chronoamperometry (i.e. four potential steps from 0 mV to + 350 mV) the sulfur forms as nanoscopic domains, whereas in single-step chronoamperometry (i.e. one potential step from 0 mV to + 350 mV) sulfur forms as a heterogeneous layer. In each case the oxidation is controlled so that the number of electrons (coulombs) passed per unit area is the same, therefore the amount of sulfur produced is also the same. The differences in morphology with electrochemical potential pathway are explained using a nucleation and growth model. The formation of sulfur on the surface increased both advancing and receding contact angle of galena, but the morphological changes induced by different electrochemical potential pathways did not significantly alter the hydrophobicity of the surface. Keywords: galena, lead sulfide, oxidation, Atomic Force Microscopy, electrochemistry, collectorless flotation, hydrophobic

Sep 1, 2012

By Fatemeh Saeidi, Malcolm S. Powell, Mohsen Yahyaei

In order to deal with the problems of existing comminution models a new approach towards the development of mechanistic models has been made so as to better understand the physics of milling processes and environments. Despite enormous improvement in this field a comprehensive study of rock breakage characterisation, appropriate for use in these types of models, is still scarce. This paper reviews the existing models of comminution according to ore characterisation techniques and parameters. The authors have looked into the existing testing methods and their applied mechanisms of breakage, using standard test results available at the JKMRC. The study includes classifying testing devices such as the drop weight tester, rotary breakage tester, slow compression, and piston and die based on the few major fundamental mechanisms of breakage that are experienced by rocks in the breakage process. The paper compares the range of particle size and energy utilisation, applied strain rates and loading mechanisms for the equipment. The product size distributions from the various equipment is compared for equivalent input energies, various loading rates but the same level of energy intensity, a broad range of energy including low energy utilisation and fines generation rate for equivalent specific energy input. The results clearly show that the outcomes and conclusions on competence and energy for breakage are a function of the test method that is applied. In ongoing work, it is proposed to investigate common tests that can be applied to characterising ores in a manner suited to modelling a range of comminution devices.

Jan 1, 2014

The air recovery from a flotation cell is the fraction of inlet air which overflows the weir as un-broken bubbles. The air recovery is an important factor in froth phase phenomena; such as gangue entrainment and froth recovery. Increasing the air recovery, results in a higher recovery of attached mineral particles. Air recovery can be measured experimentally on plant using image processing of the top surface of an overflowing froth. The air recovery is directly linked to froth stability and the bursting rate of the bubbles at the froth surface, making it very difficult to predict. Experimental results show a very strong correlation between the superficial velocity of the inlet air and the superficial velocity of the air leaving the cell through the froth surface due to bursting, calculated from the experimentally measured air recovery. This correlation holds over multiple banks from different plants. Development of a power law equation around the inlet air velocity and the bubble solids loading on the froth surface allows the superficial air velocity through the top surface of the froth to be predicted, and from this the air recovery. This model is valid for use when operating beyond the peak in air recovery.

Jan 1, 2014

By David De Klerk, Maximilian Richter, Thirunavukkarasu Pathmathas, Indresan Govender

We consider the average power dissipation distribution for dense granular flows of an idealised mono-sized charge (5 mm glass beads) in a 300 mm diameter tumbling mill operated in the cascading-to-cataracting Froude regime. By combining the inherent frictional nature of particles within a dense flow regime and noting that tumbling mills are typically characterised by collisional and turbulent stresses, we derive the power dissipation distribution for athermal boundary conditions. The input data to the model (velocity, solids concentration, pressure and flow depth) are obtained directly from non-invasive measurement using a nuclear imaging technique: Positron Emission Particle tracking (PEPT). The power dissipation due shear stresses is shown to be the dominant mode of dissipation in the tumbling mill with up to two orders of magnitude difference between pressure induced dissipation and shear.

Jan 1, 2014

By T. Wang

A new kind of mixed chelate collector was prepared in order to separate gangue (mainly quartz) and iron minerals efficiently during room temperature. The collector was was composed of two chelate collectors DES and DA. Floatation tests were carried out under 28?C with mixed magnetic concentrates of Donganshan sintering plant, and optimal test conditions were obtained, in which a direct floatation was undertaken and then a close circuit reverse floatation tests ( one roughing, one cleaning, and two scavenging), and a result of Fe grade of siderite concentrate 36.49%, Fe recovery of siderite concentrate 10.65%, Fe grade of final concentrate 66.27%, Fe recovery of final concentrate 78.25%, and Fe grade of tailing 16.22% was gained. Fourier Transform Infrared (FTIR) Spectra and Zeta potential of siderite and quartz adsorbed the DES and DA collectors before and after were measured in order to analyze the reaction between the collector and minerals. Furthermore, Molecule electronegativity of DES and DA was calculated by Electronegativity Proportionality Principle (EPP). Results showed that DES molecules have five active adsorbing sites and their molecule electronegativity was stronger while DA molecules have three active adsorbing sites, which all make the mixed collector has efficiently collecting performance. Zeta potential results of Quartz and siderite showed that at pH 11.5 both kinds of particles charged negative and at this pH value the mixed collector were mainly anionic collectors which indicate that electrostatic adsorption does not exist at this situation. FTIR results showed that characteristic peaks of the mixed collector changed before and after adsorption with the minerals, which means that there exists chemical adsorption or hydrogen bonding.

Jan 1, 2014

By D. Izerdem, S. L. Ergun

"Beneficiation of the finely disseminated valuable minerals has been an important issue in the mineral processing field for decades. Treatment of the fine materials becomes difficult with using traditional gravity concentration equipment. To investigate particles behavior in a commonly used conventional gravity concentration equipment, a comprehensive study was undertaken in a plant, which only consists spiral concentrators as concentration units. Spiral concentrators require relatively coarse material to effectively concentrate valuables as well as offering greater simplicity for especially higher grade feeds. In the current work, chromite ore (d80 = 290 µm) was treated using spiral concentrators and the performance of spiral concentrators was examined. The design of the separation circuit comprised of rougher, cleaner and scavenger stages. The resultant fractions produced by each separation unit and feed samples were analyzed to identify the particle sizes, mineral liberations and chromite content. Grade and recovery comparisons were presented in size-by-size manner and the separation tendency of the particles were determined in varying feed rate conditions. The overall results indicated valuable mineral loss of the plant and alternative suggestions were pointed to reach the target values.INTRODUCTION Spiral concentrators are simple low energy consuming devices, which are generally used for pre-concentration of the minerals. They are cost efficient equipment separating minerals mainly based on density differences of the minerals. The adjustable splitters remove the concentrate as the remaining stream continues to move down the spiral. Separation on a spiral is achieved through a combination of forces that act on particles as they move down the trough of the spiral. The main forces known to act on the particle on a spiral are the gravitational force, centrifugal force, hydrodynamic drag and Bagnold force (Atasoy and Spottiswood, 1995; Burt, 1984). Since the classification in a spiral concentrator depends on particle specific gravity and size, the operation of spirals can be analyzed using size recovery or partition curves (Bazin et al., 2014). Spiral concentrators possess multiple design parameters for a variety of applications. The design parameters that govern the performance of the spiral can be identified as the diameter, number of turns, slope, pitch and the profile of the trough. For an efficient separation on a spiral concentrator, the properties of the slurry flowing on a spiral, ore texture, percent solids and flow rate play important roles."

Jan 1, 2018

By Markus Dammers, Christopher Robben, Hermann Wotruba, Christian Schropp

"In most underground mining processes the entire extracted ore is transported from underground workings to surface processing plants for separation of valuable minerals and gangue material. Most of the transported material consists of barren rock with negligible metal content, especially for low grade deposits, such as in the copper or gold metal ore mining. Increasing mining depths result in higher costs for transportation and hoisting. Therefore, rejecting waste rock as soon as possible from the material stream gains importance. The concept of resource to product integration in the form of earliest waste rejection in combination with subsequent backfilling follows the philosophy of ‚leaving waste underground?. Implementing mineral processing underground can lead to less required mass movement to surface, hence reducing transportation and hoisting costs. At the same time, rejected waste can be used as backfill to increase extraction rates by reducing pillar volumes. In the mill, a stable high grade feed leads to decreased specific operating and investment costs as well as increased productivity and recovery. These effects as a whole have a large potential to reduce cut-off grades so that resources can be turned into reserves. Within the I²Mine (Innovative Technologies and Concepts for the Intelligent Deep Mine of the Future) project of the European FP7, investigations are carried out by the Unit of Mineral Processing of RWTH Aachen University, the Institute of Mining Engineering I and TOMRA Sorting Solutions | Mining. One aim of the cooperation is to develop new concepts for a comprehensive integration of near-to-face processing in combination with backfill into the overall underground mining process. Effects on up-, down- and side-streams are investigated to prove the potential of resource to product integration in comparison to common underground mining systems and processing methods."

Jan 1, 2014

By A. Wieniewski

The observed progress in technology of non-ferrous ores enrichment and condition of machines and equipment in the ores concentrators on the one hand have brought a possibility and on the other resulted in necessity for introduction of modernization actions. Positive results of investigations into influence of chemical modification of selected products of enrichment process on copper ores enrichment results gave possibility for implementation of chemical-flotation technologies of ores enrichment. The substantial development in flotation machines structure has contributed to modernization of flotation process resulting in increase of enrichment efficiency. The paper presents the idea and results of chemical modification of difficult in enrichment semi-products in the technology of copper ores enrichment and the results obtained after application of the modernised technology. The structure of large-volume flotation machines used in various stages of flotation and current situation in modernization of flotation process in copper ores concentrators are also described. The paper presents industrial-scale results of flotation after application of modified flotation reagents of collector group. Introduction of modifiers into the widely used xanthates resulted in increase of copper recovery in concentrate.

Jan 1, 2014

By C. Dorfling, P. Albertyn

"Hydrometallurgical recovery of metals from printed circuit board waste typically involves multiple leaching stages; conventionally, base metals dissolution by mineral acids is followed by leaching of gold using cyanide or halide based lixiviants. Alternative lixiviants for gold leaching can reduce the potential hazardous nature of operation. The aim of this study was to investigate the feasibility of using thiosulfate as lixiviant for gold leaching from waste printed circuit boards. Batch leaching tests were performed to investigate the effects of thiosulfate concentration (0.1 – 0.2 M), ammonium concentration (0.2 – 0.4 M), pH (9 – 10.5), solids content (25 – 50 g/L), and copper content of the feed material on the gold leaching behavior. The concentrations of metals in liquid samples were determined by means of inductively coupled plasma atomic emission spectroscopy, and high pressure liquid chromatography was used to evaluate thiosulfate degradation/consumption. The ratio of thiosulfate to ammonia was found to have the most significant effect on the extent of gold leaching, with the best gold extraction observed at a ratio of 0.5 mole thiosulfate per mole ammonia. The lower pH range of 9 – 9.5 generally produced better Au leaching, while low copper extraction during the first stage base metal leaching stages has proven to be detrimental to gold leaching from the residue. Thiosulfate degradation/consumption increased and gold extraction decreased with higher residual copper in the feed. An optimum gold extraction of 78.5 % from base metal leach residue was achieved with 0.2 M thiosulfate, 0.4 M ammonia, and 0.02 M cupric ions at 25°C in the pH range 9 – 9.5.INTRODUCTION Background and Aim The recycling of e-waste is becoming increasingly important as it provides certain economic benefits apart from the obvious environmental benefits. Printed circuit boards (PCBs) are found in most forms of e-waste and contain especially high concentrations of base and precious metals. Hydrometallurgical processes are often considered for the recovery of valuable metals from PCBs; these processes normally implement several leaching stages to selectively recover certain metals."

Jan 1, 2018

By Leena Vesa, Antti Remes

Design of thickeners is based on laboratory test work, characterizing the material and determining the optimal reagents, dosages and settling regimes. Several methods for dimensioning plant scale equipment exist. Kynch and Talmage-Fitch design procedures has been applied widely for a long time. Nowadays, besides them, a dynamic laboratory test work is applied for design of high rate thickeners. In that the laboratory unit is operated with known solids load per area, feed and flocculation conditions and with raking of the underflow. All these test methods afford useful data for setting up and calibrating a dynamic simulation model of a plant scale thickener. This paper presents a flocculation kinetics based dynamic thickener simulation model and a procedure to calibrate the model parameters. With the model, the underflow stream composition can be simulated over time as a function of the thickener operating parameters, which are: the feed rate and composition, underflow pumping rate, flocculant dosage and dilution of the feed. In addition, the model incorporates calculation of the slurry bed level, the cone pressure, the yield stress and the rake torque. Such a dynamic modeling scheme enables setting up simulation aided operator trainings and developing and testing of advanced control strategies, for example. The unit model can be integrated as a part of concentrator-wide flow sheet simulation model as well. Here, calibration of the kinetic flocculation model based on a laboratory test case data and further the operation of a simulated plant scale thickener are presented.

Jan 1, 2014

By Kaioeng Wang, Qi Liu, Yahui Xiang

"In the differential metal sulfide ore flotation it is desirable to replace the toxic inorganic depressants with environmentally benign chemicals. Chitosan, as a natural and non-toxic polymer, has been proven to be an efficient depressant for chalcopyrite while allowing galena to be floated by xanthate collectors. However, the poor solubility of chitosan limits its potential applications as the flotation could only be carried out at about pH 4 where chitosan is soluble. A carboxymethyl derivative of chitosan, named N-carboxymethyl chitosan (N-CMC), was synthesized by substituting the amino groups of chitosan with carboxymethyl groups. The substitution significantly improved the solubility of chitosan. The structure of N-CMC was studied and compared with chitosan via Fourier transform infrared spectroscopy (FTIR). Flotation tests were performed on single minerals and mineral mixtures (with weight ratio of 1:1) with the addition of appropriate amount of potassium ethyl xanthate (KEX) and N-CMC. The solution pH was varied from neutral to alkaline. The flotation concentrates and tailings were collected and analysed for the contents of copper and lead. FTIR measurements showed that new peaks of C=O stretching of -COOH and N-H deformation of -NH- appeared in N-CMC, which indicated that the carboxymethyl groups were introduced and the amino groups were the sites for the substitution. Flotation results indicated that N-CMC could depress either chalcopyrite or galena depending on the pH. The results were not affected by the sequence of KEX and N-CMC addition. Therefore, N-CMC is potentially useful in Cu-Pb sulfide separation following a bulk Cu-Pb flotation. The N-CMC was also found to have surface cleaning functions, and was able to remove contaminating copper ions from galena surfaces. Therefore, its application in sulfide ore flotation is expected to be more robust than the original chitosan."

Jan 1, 2014

By Crasta Jeason, T. Sreenivas, M. Narasimha

The subtle nature of the flow inside the hydrocyclone has encouraged development of mathematical models for predicting its performance, which are widely used in simulation of comminution circuits. But most of the models available are based on single average feed density. But the feed to hydrocyclone classifier is generally mixture of particles of different densities. This effect of varying density of feed particles on performance of hydrocyclone has been reported in literature. Further investigation of the effect of multi component feed on the performance of hydrocyclone is the objective of this work. This work involves experimental work to study multicomponent behaviour in various size cyclones. The performance of hydrocyclone for feed mixture of magnetite and quartz has been studied. The effect of presence of magnetite, a high density material on efficiency of separation of quartz has been analysed. It was observed that the effect of component interaction increases with feed solids concentration leading to an increased cut-size for a given optimum cyclone conditions. Based on the multi-component exiperiments available in literature, a concept for modeling the performance of hydrocyclones is proposed. A set of semi-empirical model equations for cut-size, sharpness of separation are presented. An attempt to validate the new hydrocyclone model on multi-component behaviour is made.

Jan 1, 2014