Mineral texture is a critical factor which controls ore variability and is an important attribute in geometallurgy. In relation to downstream processes, it affects the fracture pattern during breakage, where rock strength is inherently a function of mineral texture. Because of the subjective nature of mineral texture, it has not been easy to quantify, especially in the context of a measurement suitable for use in geometallurgical programmes. The aim of this paper is to present the first steps in developing a 3D mineral texture quantification method for drill core and to assess its sensitivity to differences in rock strength using a case study. The methodology includes classifying the textural information using the 3D grey level co-occurrence matrices (GLCM) and X- ray computed tomography (XCT) coupled method. Rock strength tests were performed using the split Hopkinson pressure bar (SHPB). The case study investigates a heterogeneous polymetallic sulphide deposit and a homogeneous shale subdivided into three 'mineral textural types'. The variability is largely captured by the GLCM matrices, and preliminary trends can be observed where the shale is finer grained and has a higher yield strength in comparison with the coarser grained polymetallic sulphide ore.

Turbulence is an important factor that affects flotation performance, which needs to be incorporated into flotation models. However, the measurement of turbulence in industrial flotation cells is difficult because of the highly abrasive and aggressive slurry environment. This has made the development and validation of models incorporating turbulence difficult. The development of a measurement methodology based on the piezoelectric vibration sensor (PVS) has enabled the measurement of kinetic energy fluctuation in flotation cells. In the study presented in this paper, the PVS was first applied to a sugary water-air two phase mixture in a 3 m pilot flotation cell, and then to a Metso 3 m flotation test rig with magnetite/silica slurry and air, to collect turbulence data. An orthogonal experimental design was used for both sets of tests, with different impeller speeds, air flow rates, cell level (aspect ratio) and sugar concentration (viscosity) as input hydrodynamic parameters. From the measurement data collected in the two cells, the volume of the turbulence zone could be modelled; from this, the turbulence distribution in the flotation cells could be predicted. The models were validated by comparing the predicted with the experimental results.

Acid rock drainage (ARD) characterisation and prediction protocols, comprising geochemical static, kinetic and biokinetic tests, sometimes fail to adequately assess the ARD potentials of sul dic mine wastes. Several authors have partly linked this shortfall to the insu cient use of mineralogical and textural analyses. Mineral liberation and association data may inform the interpretation of the results of standard ARD tests and this study assesses these parameters for Fe-sul de minerals in the feed material for humidity cell (meso-scale), static and biokinetic (micro-scale) tests. Results show that the dominating textural parameters on the mesoand micro-scales are association and liberation, respectively.

Mixtures of collectors have been widely used for many years in sulphide flotation, and a range of performance benefits have been reported for many different systems. The combinations of collector types have varied, as have the ratios that have been used. Synergistic effects have been obtained (greater than the sum of the parts) and in some cases the mechanisms of this improved behaviour have been identified. These benefits have been attributed to increased carrying capacity of the froth phase, faster kinetics, and more successful recovery of middling or coarse particles. It is the interaction between the various components of the mixed collector system, rather than the individual main effects, that dominate the performance benefits. The process benefits include increased paymetal recoveries and grades – as well as increased rates of recovery whilst using lower dosages of reagents. Various mechanisms have been reported and are discussed. These have been shown to affect different composition/liberation classes and sizes of mineral particles. In recent years, automated quantitative mineralogy and surface analysis technology such as ToF-SIMS have enabled the development of better information, to establish what aspect of the process has been affected. This has been successful mostly for use in a diagnostic capacity. Candidate selection for the mixed collector suite is presently based on experience and contextual knowledge. Predictive properties from these systems are a desirable future goal. Currently optimum combinations are preferably identified experimentally at laboratory scale prior to any plant trial. It is recommended that such laboratory work be performed using a factorial design with replicates and quality controls, such as may be delivered from High-Confidence Flotation Testing. The purpose of this paper is to summarise and review current theory and practice in the usage of mixtures of collectors in sulphide flotation – both in the application and in research in order to develop insights and guidelines to develop a methodology for use in a predictive capacity. A case study demonstrating this approach will be published at a later date.

Talc and mica are major gangue minerals in many base metal ores including sulfide ores. Talc is a naturally hydrophobic mineral, and therefore it is easily floatable. There have been many studies to overcome this problem, and depress talc with various reagents. In this study the flotation of a copper ore in the presence of talc and muscovite was studied. It was found that talc can affect copper flotation mainly via froth phase. The copper grade and recovery were affected in the presence of only 7% talc. On the other hand, muscovite influenced the pulp phase via affecting the pulp rheology. The copper flotation grade was reduced in the presence of high amount (30%) of muscovite due to the entrainment, but its effect on the copper recovery was negligible.

An integrated process modelling framework, underpinned by mineralogy, is under development at the University of Cape Town as a holistic approach towards addressing the multifaceted challenges currently faced in mining. is paper demonstrates application of this approach for the case of a polymetallic base metal sul de otation circuit. In this case study, the e ect of potential design strategies and feed ore variability on net acid producing potential of the resulting tailings is assessed. e framework is underpinned by mineralogical calculations of acid potential and neutralising potential. Application of the framework allows for the identi cation of potential opportunities towards more sustainable mining practice.

Modern Process Mineralogy has been making significant advances in methodology and data interpretation since it was assembled in the mid-1980s as a multi-disciplined team approach to obtaining mineralogical information from drill core and plant samples so as to infer the metallurgical processing requirements of that ore. This hybrid discipline consists of teams that include geologists, mineralogists, samplers, mineral processors and often others, working together. The degree of cross-training, communication and trust dictates the potential capacity of the team and it is possible to develop technical capabilities that surpass those of conventional teams. A pivotal tool for technically efficient and plant-oriented process mineralogy is, of course, the use of modern, automated laboratory technology. In these cases, process mineralogy, though associated with some capital investment, is a valuable risk reduction tool and an operations optimization tool for any mining company, not only in terms of finances but also in terms of human and intellectual capital. However, if the teams are dysfunctional and information is not interpreted correctly due to limited experience in the team or less than best practice, or it is not implemented or used, much of the value can be lost. Process Mineralogy can then be regarded as 'time consuming and expensive'. In this paper, the business value of best practice Process Mineralogy is outlined and discussed. Case studies that include 'green fields' new design applications and 'brown fields' interventions to mature operations have been selected to demonstrate the tremendous financial value that can be achieved are presented, along with those where costly disasters could have been averted. The list is not intended to be exhaustive or complete, and the reader is referred to the extensive literature available. Examples are selected for this publication specifically to illustrate the delicate balance between generating additional business value through potentially expensive mineralogical analyses and the lost opportunities of underperforming flowsheets, unanticipated losses due to high feed variance, inadequate liberation or deleterious minerals, over-reagentised circuits, or extra costs of unnecessary or underutilised equipment.

By adopting the ambitious set of seventeen Sustainable Development Goals (SDGs) incorporated into the UN’s ‘Transforming our world; the 2030 Agenda for Sustainable Development’1, the member states recognised that it was no longer ‘business as usual’. In order to achieve these goals in the time frames set, fundamental transformation of how the world lives, works and thinks is necessary. All sectors of society are needed to cooperate and work together to achieve them. Since universities, and particularly research-intensive universities, are enablers of transformation through a number of roles, their participation is critical. In particular, they provide development of new tools and technologies; build capacity through education and equipping future leaders; foster independent and critical thought-leadership; and have the convening power to stage platforms for discussion and debate by a range of stakeholders. The University of Cape Town (UCT) established the Minerals to Metals Initiative (MtM) in 2007 in recognition of the need for interdisciplinary research in minerals beneficiation. This paper discusses how this Initiative provides a platform for sustainable development through minerals and metals, and is playing a pivotal role in this area.

The minerals industry is currently facing numerous multifaceted challenges spanning the techno-economic, environmental and social spheres. The adoption of sustainability thinking is a holistic approach to addressing these challenges and their relative interactions, rather than just focusing on individual units and processes. The ability to do so requires an integrated modelling framework underpinned by mineralogy, so that the effect of ore complexity and variability on one or more of these factors can be simultaneously evaluated and optimised. This study focuses on the steps towards the development of an integrated framework using a case study of a poly metallic sulfide ore flotation circuit. A unique ore specific element to mineral conversion recipe (EMC) was developed and validated, and after subsequent mass balancing across the circuit allowed the calculation of mineral grade and recovery throughout. By application of a set of mineral mass distribution functions across the circuit, and including a simple mineral-based model for the determination of tailings ARD potential, the integrated framework is used for scenario analysis. Two different scenarios are presented: the first considering the balance between improving copper concentrate product quality at the expense of increasing tailings ARD potential, and the second considering the effect of feed ore variability on tailings ARD potential. The framework provides a conceptual starting point for a new approach to traditional process mineralogy studies to start practising sustainability thinking.

In previous study, the selective separation of enargite from complex ore samples in a batch flotation system under controlled pulp potential was investigated (Tayebi-Khorami et al., 2017b). It has been found that it is possible to make a separation between enargite and the other copper minerals in a real ore system using pulp potential control. In this study, the effect of the surface chemistry on the floatability of enargite and pyrite in complex ore systems were investigated. Based on flotation behaviour, EDTA (Ethylenediaminetetraacetic acid) extraction, pulp potential measurement and pure mineral study, it was found that the galvanic interactions between sulphide minerals, and, pulp potential conditions, determined the flotation performances of the ore samples. It was also concluded that enargite had the lowest rest potential compared to the other sulphide minerals, which caused strong galvanic interaction between enargite and pyrite. This study has an important implication in sulphide flotation where enargite is present in the ore samples.

The AMIRA P9 model has floatability (P) as the ore property which is considered to remain constant in different flotation cell sizes under different hydrodynamic conditions. However, in this study increasing the power input increased the P value, especially in finer particle size classes (below 75 pm). Acceptable explanations for the floatability variations, as a result of hydrodynamic condition variations in the flotation cells, have been sought by looking at the literature and the results obtained in this study were published in part one of this manuscript. To improve the accuracy of the AMIRA P9 flotation model in predicting flotation rate constant (k) and to improve the consistency of ore property, measurable and appropriate turbulence parameters were sought to be incorporated into the model. Therefore, two dimensionless turbulence parameters ae and EVF, derived from practical measurements, were formulated and introduced to the AMIRA P9 model. The modified ore floatability parameter, P", was demonstrated to be a more consistent characterisation of the ore property than P and both the accuracy and precision of the k prediction improved for a variety of hydrodynamic conditions of flotation cells. (C) 2016 Elsevier Ltd. All rights reserved.

Recent research has demonstrated promising results showing the possibility of separating arsenic-copper sulphides from other copper minerals by controlling the potential of the flotation pulp. Most of these studies were conducted on single mineral systems, and the selective removal of arsenic-copper minerals in real ore systems is not well understood, particularly, the effects of mineralogical properties such as liberation and mineralogical association.In this study, two distinct ore samples, termed low arsenic sample (LAS) and high arsenic sample (HAS) were selected from the Tampakan copper-gold deposit in the Philippines, providing a range of arsenic levels. The selective separation of enargite from other copper sulphide minerals in a rougher flotation system under controlled pulp potential was investigated for both samples.

In line with the principles of cleaner production, the removal of monazite via reverse flotation was investigated with a view to reducing the radioactivity of a heavy mineral sands waste stream. Another benefit was to create a potential REE by-product from the Namakwa Sands operation in South Africa. Understanding the mineralogy of the zircon waste stream was essential owing to the cemented nature of the deposit and the potential impact of surface coatings on the flotation performance. SEM, QEMSCAN and optical microscopy showed that amorphous SiO2 was the most abundant surface coating associated with both monazite and zircon, which is likely to constitute a major challenge in achieving flotation selectivity. A D-optimal statistical screening design was applied to find the most relevant flotation parameters and a full factorial design to find the optimal flotation conditions. The most promising results showed that monazite could be successfully removed from the zircon waste with an oleate collector at pH 10. The selectivity was found to be highly dependent on pH, With no selectivity at pH 9 and no mineral flotation at pH 11. Further work is recommended to confirm and optimise these conditions and test them on a larger scale. (C) 2016 Elsevier Ltd. All rights reserved.

Turbulence is an important factor that affects flotation performance, which needs to be incorporated into flotation models. However, the measurement of turbulence in industrial flotation cells is difficult because of the highly abrasive and aggressive slurry environment. This has made the development and validation of models incorporating turbulence difficult. The development of a measurement methodology based on the piezoelectric vibration sensor (PVS) has enabled the measurement of kinetic energy fluctuation in flotation cells. In the study presented in this paper, the PVS was first applied to a sugary water-air two phase mixture in a 3m3 pilot flotation cell, and then to a Metso RCS 3m3 flotation test rig with magnetite/silica slurry and air, to collect turbulence data. An orthogonal experimental design was used for both sets of tests, with different impeller speeds, air flow rates and cell level (aspect ratio) as input hydrodynamic parameters. From the measurement data collected in the two cells, the volume of the turbulence zone could be modelled; from this, the turbulence distribution in the flotation cells could be predicted. The models were validated by comparing the predicted with the experimental results.

The deleterious effects of clays on flotation performance are widely acknowledged but the mechanisms involved are not clearly established. Moreover, the concentrations beyond which clay minerals become problematic are not clearly defined. One major parameter is the difference between swelling and non swelling clays which is evaluated in this study. The ore slurry pulp rheology and froth stability were monitored in the absence and presence of different clay minerals. It was found that swelling clays can adversely affect the flotation performance mainly via adsorbing water which changes the rheology and froth stability, reducing both flotation grade and recovery. Non-swelling clays had a lower effect on the rheology. Kaolinite increases the froth stability and reduces the flotation grade but illite showed the least effect on the flotation performance in this study. The potential mechanisms and critical concentrations are discussed. (C) 2016 Elsevier Ltd. All rights reserved.

Recoverable economic copper sulphide minerals such as chalcopyrite, bornite, chalcocite and covellite often occur together in varying proportions in the major copper-bearing ores, and have individual flotation requirements and characteristics. Pyrite also occurs in these ores to varying extents as the sulphide gangue, and is problematic because of its natural tendency to float quickly and easily. In a bulk sulphide float, selectivity against pyrite is desirable, particularly if it does not host other paymetals such as gold or silver. At the same time it is a requirement to float all of the copper sulphides despite their electrochemical differences. The electrochemistry and semiconductor properties of these minerals are reviewed, together with implications for flotation with and without collector addition. Mixed collector systems for the improved flotation of these sulphides are proposed as a solution. The use of xanthate and dithiophosphate in the collector suite allows the co-existence of dixanthogen and free dithiophosphate radical because the latter has a higher redox potential requirement than xanthate to oxidize to the dithiolate. Because some of these minerals require dixanthogen, and others, free thiolate, to generate surface hydrophobicity, a bulk flotation of all the species becomes possible in the overlapping area of Eh and pH between the two dithiolate equilibrium lines on the Pourbaix Diagram. The arsenic-signature copper minerals are added to the study, since many copper operations encounter arsenic as a penalty element in the saleable concentrate. It is shown that the addition of arsenic to the copper and iron sulphides alters the semiconductor and electrochemistry properties, and in turn, its flotation characteristics. The degree of mineral association and liberation between these minerals can be a complicating factor due to textural associations, and should also be considered in the process as a next step.

Developing practical measurement methodologies to characterise hydrodynamic conditions of flotation cells of any size, and the provision of useful data for flotation modelling, are a challenge. In this study, several measurement instruments such as a power meter, hot-wire anemometer, bubble sizer, air flow meter and viscometer were used to characterise the hydrodynamic condition inside two different flotation cells (5 L and 60 L) making it possible to compare the hydrodynamic conditions of a 5 L (lab scale) cell with a 60 L (pilot scale) flotation cell. As a result, power input, energy dissipation rate, turbulent kinetic energy, bubble size and air flow parameters were obtained for 12 different hydrodynamic conditions in the cells.It has been assumed that P (ore floatability) in the AMIRA P9 model remains constant over a wide range of bubble surface area flux (S-b) regardless of the amount of power introduced into a flotation cell. Therefore, increasing the impeller speed in the cell does not have any effect on the P value if P is the true ore property. However, flotation test work was conducted in the above mentioned different hydrodynamic conditions in both cells, and shows that by increasing the power input the P value is also increased, especially for particle size classes below 75 mu m in both cells. P, in its current form, cannot therefore be the true ore property and is influenced by cell hydrodynamics. It should be mentioned that the current AMIRA P9 model still remains a useful model to simulate a plant operation under some circumstances not far from its original design state. However, in order to improve the scale up capability from lab scale flotation tests, it is necessary to incorporate the measured hydrodynamic parameters into the AMIRA P9 model. (C) 2016 Elsevier Ltd. All rights reserved.

Early integration of sustainability decisions and mineralogical attributes into the design of minerals processing units offers potential for reducing environmental impacts at mining and processing sites. The objective of this study is to demonstrate how the integration of sustainability indicators and mineralogical attributes could be achieved in developing an integrated modelling framework of a magnetic separator. A magnetic separator unit model based on existing literature was developed to include process stream mineralogical data and to output sustainability indicators. The overall sustainability of processing three ore types (low, medium and high grade iron ore) was evaluated using the developed model. Novel measures for evaluating magnetic separation (Grade Recovery Deviation Index (GRDI)) and energy efficiency (Rotational Energy Transfer Efficiency (RETE)) that incorporate the use of ore characteristics were developed in this study. These measures were used to calculate the separation and energy efficiency sustainability indicator ratings. In total eleven magnetic separator sustainability indicators were identified. Each indicator was assigned a weighting value out of 10 based on its importance. Of the 11 sustainability indicators identified; safety, reliability, Carbon dioxide (CO2) emissions, water use, noise and job creation ratings did not vary with changing mineralogical attributes of the feed ore. GRDI, RETE, electricity cost, particle emissions and waste generation ratings were observed to be dependent on the ore characteristics and therefore their values varied with different feed ore grades. The Analytic Hierarchy Process (AHP) and Weighted Sum Method (WSM) methods were applied to the sustainability indicator ratings and weightings to evaluate an overall sustainability cardinal score of processing a particular ore feed. Results of this study demonstrate the dependence of overall process sustainability indicators on feed ore mineralogical attributes. The results also provide an indication of the effect of ore variability (typical within a single deposit) on sustainability indicators. (C) 2016 Elsevier Ltd. All rights reserved.

The success of any scale up process is dependent on how well the small scale test work represents the conditions of the larger scale and how well the predictive model captures the key contributors to the process. The AMIRA P9 flotation model was developed by the P9 team over a number of years (Gorain, 1997; Gorain et al., 2006). It has been widely used and generated significant value for many operations by assisting the decision making process through simulations of process changes and for flotation scale up predictions. This model assumes that the parameter P (ore floatability) remains constant over a wide range of surface area flux measurements (Sb) regardless of the amount of power introduced into the flotation cell. As a focus of this research, flotation test work was conducted at different hydrodynamic conditions in 5 and 60L cells to challenge this assumption. Increasing the power input increased the P value especially in finer particle size classes (−75μm) in both cells demonstrating that P is not a true ore property because it is influenced by the cell hydrodynamics. To improve the accuracy of the AMIRA P9 flotation model in predicting the flotation rate constant (k) and to improve the consistency of the ore property in the model, measurable and appropriate turbulence parameters were sought to be incorporated into the model. Dimensionless turbulence parameters that could be obtained directly from measurements, ӕ (characterizing turbulence intensity, bubble size and viscosity) and EVF (characterizing the effective volume in flotation where majority of collision and attachment occurs) were formulated and introduced to the AMIRA P9 model. The consistency of P″ (the updated floatability component) as a more consistent ore property was improved which enhanced the flotation rate constant prediction for a variety of hydrodynamic conditions of the 60L flotation cell. Further work is recommended to test the model for continuous rather than batch processing, in larger cells that are more similar to industrial cells and to further improve the accuracy and precision of predictions of the behaviour of coarse particles.