Mineral Recovery Research Articles

Study of chalcopyrite flotation in the presence of illite using a design of experiments approach

AbstractThe interaction between chalcopyrite and illite particles was analysed using ζ-potential measurements and flotation tests. Statistically designed tests were used to examine the factors controlling flotation (frother concentration, dispersant concentration, froth height, airflow rate and amount of clay). Furthermore, the significance levels of the impacts of these factors on responses (chalcopyrite grade/recovery, pyrite grade/recovery, dynamic froth stability and mean bubble diameter) were determined. Chalcopyrite and pyrite ζ-potentials were measured in the presence of illite. The addition of 15% illite to the chalcopyrite, especially between pH 11 and 12, shifted the ζ-potential values closer to that of pure illite, indicating complete surface coating of chalcopyrite with illite. In the flotation experiments, better results were obtained in terms of chalcopyrite grade at a low airflow rate and a high froth height. With increasing froth height there was a decline in the gangue mineral recovery as the residence time of the froth increased. The most significant factor increasing pyrite recovery was the amount of clay. Although illite is considered to be the least problematic clay mineral for flotation, as reported in the literature, an illite content of as low as 5% in the ore decreased chalcopyrite grade by 3.83%. While K and Na contents of 4% were detected after flotation without the addition of illite, their abundance increased to 5.7% after the addition of illite.

Effect of casein to fat ratio of camel milk on solids losses in cheese whey and their recovery in camel milk cheese

Three sets of camel milk were standardised at different casein/fat ratios [0.73 (set A, control), 0.60 (set B) and 0.90 (set C)] using skim milk and cream separated from camel milk. The milk was coagulated using camel chymosin and cheese was prepared. The whey (AW, BW and CW) and cheese samples (AC, BC and CC) from respective milk samples A, B and C, were analysed for composition and colour. Cheese whey with higher losses in solids and minerals (AW and BW) had higher L∗ value, whiteness index and lower total colour difference (ΔE) compared with CW. Camel milk cheese CC had higher solid and mineral recovery resulting in higher cheese yield as compared with other experimental cheeses. The results indicated that standardising camel milk to 0.90C/F led to higher cheese yield and lower mineral and solids losses in whey.

A pilot-plant for the selective recovery of magnesium and calcium from waste brines

The problem of brines disposal has raised great interest towards new strategies for their valorisation through the recovery of minerals or energy. As an example, the spent brine from ion exchange resins regeneration is often discharged into rivers or lakes, thus impacting on the process sustainability. However, such brines can be effectively reconcentrated, after removal of bivalent cations, and reused for the resins regeneration. This work focuses on developing and testing a pilot plant for selective recovery of magnesium and calcium from spent brines exploiting a novel proprietary crystallization unit. This is part of a larger treatment chain for the complete regeneration of the brine, developed within the EU-funded ZERO BRINE project. The pilot crystallizer was tested with the retentate of the nanofiltration unit processing the spent brine from the industrial water production plant of Evides Industriewater B.V. (Rotterdam, The Netherlands). Magnesium and calcium hydroxide were selectively precipitated by adding alkaline solution in two consecutive steps and controlling reaction pH. Performance was assessed in terms of recovery efficiency and purity of produced crystals, observing in most investigated cases a recovery of about 100% and 97% and a purity above 90% and 96%, for magnesium and calcium hydroxide, respectively.

Challenges and opportunities for development of the Vietnam mineral processing in the XXI century

Mineral mining and processing Industry of Vietnam is facing a number of huge challenges at present, but there are also great opportunities for its growth in the future. Mineral processing plants need to make breakthrough improvements in the process designing, technology and equipment utilisation in order to meet requirements of the new era. These challenges force our miners and mineral processing operators to constantly make efforts in researches and to bring best solutions to improve plant operations to ensure the requirements of safety, market demands, product quality, sustainable development and environmental friendliness. Specifically, the issues that need to be addressed urgently are capacity and quality of the workforce, tailings treatment, fine particle processing, ores of low washability, recovery rate increase and maximisation of recoverable valuable minerals, environmental issues and workplace safety monitoring and control, maximasation of production efficiency and reduction of operating costs. This report presents the current key challenges of the mining and mineral processing industry in order to help professionals and policy makers in the field of mineral mining and processing to bring rational directions for action initiate appropriate studies and improve management methods; to help mineral processing plants in improving the production efficiency and recovery of valuable minerals; to reduce operating costs and to become environmentally friendly and to develop sustainably.

A biosurfactant-producing and iron-oxidizing mixotrophic bacterium as an environmentally friendly reagent for eco-green flotation of Indonesian complex Pb-Zn ores

In an effort to find new sources of reagents for flotation in mineral processing, local microorganisms originating from the surrounding mining areas and surrounding areas were tested to be alternative bioreagents. The bacterium Alicyclobacillus sp. (a new local bacterial strain) was chosen because of its easy growth and no biological risk, and its capability to oxidize iron and sulfur and produce biosurfactants. Batch experiments were conducted to study the effect of bacterial adaptation to minerals on bioflotation performances evaluated by the contact angle measurement of galena, sphalerite, and silica at various pHs. Furthermore, laboratory-scale experiments with the Denver flotation cells were conducted to investigate the effect of pH, bioreagent concentration and conditioning time on mineral grade and recovery. The results showed that the bacterium had a high recovery of Pb (90.21%) and Zn (80.83%) with grades of 4.82% and 8.91%, respectively. Although these results were lower than the collectors adopted by the industry (based on our flotation performance using conventional flotation reagents), the bacterium had the potential to be used in the future for mineral flotation as an alternative eco-friendly reagent, presenting as biodegradable, ecologically sustainable reagents.

Coal flotation in a low-rank carbonaceous mineral using 3-phenyl-1-propanol as a collector reagent

In the present work, 3-phenyl-1-propanol is proposed as a new collector for coal flotation in a low-rank carbonaceous mineral containing 2.0% of carbon and basic groups predominantly on the surface. Hydroxyl and carbonyl groups, as well as unsaturated carbon chains, were identified by FT-IR. Microflotation tests were conducted to evaluate and compare the effectiveness of the collector proposed with the one obtained using kerosene, diesel and 1-butylamine. Results show that the highest coal recovery is obtained with 3-phenyl-1-propanol. Mineral has a negative zeta potential in the pH range 2–13, but it does not show an isoelectric point. Furthermore, the zeta potential is modified by the collector. After conditioning, signals corresponding to the collector were identified in the mineral surface by FT-IR. A Box-Behnken experimental design was used for optimization of mineral Recovery and Clean Coal Recovery by flotation. Results showed that pH has not a significant effect on the mineral Recovery, however flotation time and volume of 3-phenyl-1-propanol have a significant direct effect. Optimal conditions for mineral Recovery were pH 8.5 and 84.5 µL of collector for 0.5 g of mineral. For Clean Coal Recovery; pH, flotation time and volume of 3-phenyl-1-propanol have a significant effect. Optimal conditions were pH 4.0, flotation time 2.5 min and 87.9 µL of collector for 0.5 g of mineral.

Computing single-particle flotation kinetics using automated mineralogy data and machine learning

Studies of flotation kinetics are essential for understanding, predicting, and optimizing the selective recovery of minerals and metals through flotation. Recently, much effort has been made to use intrinsic ore properties to model flotation behavior. Particle-based characterization methods, e.g. SEM-based image analysis, have enabled much of this development. However, currently available methods for studies of flotation kinetics can not accommodate single-particle data, resulting in incomplete use of data that is readily available today. In this contribution, a method is introduced to apply kinetic flotation models to individual particles. This method, based on lasso-regularized multinomial logistic regression, allows for an in-depth understanding of particle flotation behavior as a function of all measured particle characteristics. With the proposed method, the joint influences of particle size, shape, as well as modal and surface compositions on the recovery of individual particles can be taken into unprecedented consideration. The results of the simulated particle behavior showed a very good agreement to the outcome of conventional empirical studies and follow well-described froth flotation recovery behavior.

Barriers and enablers of technology adoption in the mining industry

Technological innovations are recognised to directly contribute to sustained competitive advantage. They are particularly relevant in the mining sector, which deals with challenges of depleting access to resources and which urgently needs new solutions to remain sustainable and competitive. Technological innovations help mining firms reduce costs, lessen environmental impact, increase production and improve mineral recovery. Understanding barriers and enablers to technology adoption is important for the success of technology implementation efforts and sustainability of the mining sector. Previous studies on technology adoption have focused mainly on organisations in the manufacturing and service sectors. However, limited literature exists focusing on barriers to and enablers of technology adoption in the mining sector. Using data from 28 interviews with mining experts, this study identified five environmental- and four organisational-level barriers to technology adoption in mining. It also uncovered five enablers to overcome these barriers to achieve more successful technology adoption outcomes. In addition, two policy implications are proposed for mining firms to improve their technology adoption outcomes: (1) development of organisational norms and practices aligned with the culture of innovation and (2) development of sustainable practices to collaborate with external stakeholders. Future research directions to overcome the barriers and capitalise on the opportunities are also discussed.

Stability analysis of roadside backfill body at gob-side entry retaining under combined static and dynamic loading

The applications of gob-side entry retaining (GER) techniques tends to increase over time as it can increase the minerals recovery rate and reduce the output of the waste. In the literature, only the performance of the roadside backfill body (RBB) at gob-side entry retaining under static loading has been investigated. However, failure mechanisms of the RBB under dynamic loading with various roof cutting angles have not been addressed. This study presented an numerical simulation of the fracture propagation and distribution in the roadside backfill body along the gob-side under combined static and dynamic loadings using the Trigon model built in UDEC (Discrete element methods) software. The influence of the roof cutting angles on the behavior of the RBB was also discussed. The input parameters were determined by back analysis with the field data. Results of the model show that static loading is a bigger contributor to the failure of the RBB compared to the dynamic loading. Several clear fractures were observed at top left and bottom right of the RBB and the fracture was more intensive at top left. In addition, it was found that if the roof cutting angle is 70°, the influence of the dynamic loading on the RBB is minimum, and the area and severity of the shearing failure in the RBB is minimum as well. As a result, it was determined the optimal roof cutting angle was 70° and a combined support measure of “roof cutting + roof support above RBBs + RBB reinforcement” is proposed. The application of roof cutting in gob-side entry retaining (RCGER) techniques in the Lingzhida coal mine indicates that deformation of the surrounding rocks can be effectively controlled.

Sustainable brine management from the perspectives of water, energy and mineral recovery: A comprehensive review

Desalination activities around the world are increasing as a result of water scarcity. The discharge of brine from desalination processes poses a significant threat to the environment. Large amounts of water, energy and minerals remain unexploited and are wasted in brine discharged from desalination plants. Due to more stringent environmental regulations and the need for more cost-effective desalination processes, sustainable brine management is critical for the utilization of these untapped resources within brine. In this review, current environmental regulations from different regions around the world were highlighted and compared. Various technologies and processes from the perspective of water, energy and mineral recovery have been discussed with the aim of achieving sustainable brine management. The advantages and disadvantages of these technologies have also been analyzed. Various case studies were provided at laboratory, pilot and industrial scale levels. The outlook and insight provided in this review will contribute to achieving sustainable brine management.

Mineral bioflotation optimization: Comparison between artificial neural networks and response surface methodology

The present work studied the fundamental of polynomial modeling and artificial neural network (ANN) techniques applied to the bioflotation of apatite, calcite and dolomite using the Rhodococcus opacus biosurfactant. Both techniques were used to model the bioflotation process and optimize some bioflotation parameters (pH and biosurfactant concentration). A full quadratic model optimized with genetic algorithm (GA) and a three-layer feedforward neural network were used to describe the mineral recovery. Different training algorithms and activation functions were tested to gather to an ANN with the best generalization capacity. Although the variation of the sigmoid activation function did not lead to a considerable change in the robustness of the ANN, the use of standard numerical training algorithms produced ANN models with better accuracy. ANN models demonstrated higher adequacy to describe and predict the mineral recovery than polynomial models. For all mineral studied, mineral recovery increased for a more acidic medium and for a higher biosurfactant concentration (BC). BC exhibited a higher effect on mineral recovery than pH, showing pH an increasing effect on mineral recovery as the optimal BC values were approached. Rhodococcus opacus biosurfactant demonstrated to be a promising solution for the separation of carbonate gangue minerals from phosphate ores.

The Use of Mining Tailings as Analog of Rare Earth Elements Resources: Part 1 – Characterization and Preliminary Separation

ABSTRACT The rapid depletion of high-grade rare earth elements (REE) resources implies that future supplies may be augmented with low-grade ores, mining tailings and other unconventional resources to meet cutoff grades and subsequently supply demands. In this work, detailed characterization of tailings from a copper processing plant was carried out to expand the knowledge of their chemical and mineralogical characteristics for REE recovery. The results showed that the REE are mainly mineralized as bastnäsite, monazite, and stetindite, along with uncommon minerals, such as brannerite, stillwellite, and florencite, for which there is limited processing data. In a preliminary effort to recover the REE, the tailings were subjected to gravity, magnetic, and froth flotation separation. Over 90% REE recovery was achieved via froth flotation, whereas magnetic and gravity separation tests recovered up to 86% and 54% REE, respectively. The results from this study suggest that, with systematic optimization studies, REE recovery and upgrade could be enhanced, with significant efforts of minimizing the recovery of key gangue minerals, such as goethite, hematite, and quartz. Overall, the study confirms that the tailings used in this work could be regarded as unconventional REE resources subject to tactical development and optimization of beneficiation methods.

Challenges Related to the Processing of Fines in the Recovery of Platinum Group Minerals (PGMs)

In order to increase the recovery of PGMs by flotation, it is necessary to optimise the liberation of the key minerals in which the platinum group elements (PGEs) are contained which include sulphides, arsenides, tellurides, and ferroalloys among others, while at the same time ensuring the optimal depression of gangue minerals. In order to achieve this, comminution circuits usually consist of two or three stages of milling, in which the first stage is autogeneous, followed by ball milling. Further liberation is achieved in subsequent stages using ultra-fine grinding. Each comminution stage is followed by flotation in the so-called MF2 or MF3 circuits. While this staged process increases overall recoveries, overgrinding may occur, hence creating problems associated with fine particle flotation. This paper presents an overview of the mineralogy of most of the more significant PGM ores processed in South Africa and the various technologies used in comminution circuits. The paper then summarises the methodology used in flotation circuits to optimise recovery of fine particles in terms of the collectors, depressants, and frothers used. The effect of entrainment, slimes coating, changes in rheology caused by the presence of a significant amount of fines and of chromite recovery is addressed.

The effect of screen versus cyclone classification on the mineral liberation properties of a polymetallic ore

The heuristic of a constant liberation by size independent of the degree of comminution has been established as a robust assumption over time. Therefore, when assessing the comminution circuit performance, achieving a final target P80 size at the lowest possible energy and cost seems to be the only concern. The introduction of higher capacity fine screening to replace hydrocyclones challenges this fixed approach due to the inherent difference in classification principles between the technologies. The impact of classification efficiency and mode on the liberation properties of a polymetallic ore ground in a production ball mill circuit are presented. It was found that the liberation properties remained constant across the comminution device but were significantly different across the circuit. The circuit closed with screens was found to improve the coarse particle liberation in comparison to the hydrocyclones. The liberation data is presented and implications for circuit performance are discussed. It is postulated that the assessment of comminution circuit design and performance should be based on the ultimate objective, recovery of the valuable minerals, and thus be based on the ore- and process-specific recovery window, not on a fixed ‘grind size’.

Catalytic upcycling paper sludge for the recovery of minerals and production of renewable high-grade biofuels and bio-based chemicals

Paper sludge is a solid waste by-product abundantly produced in the paper industry and contains fine minerals and lignocellulosic biomass. In this contribution, the ex-situ catalytic fast pyrolysis of paper sludge with a high mineral content of ca. 71 wt% is reported for the first time and demonstrated in a pilot-scale unit (feeding rate of 11.3 kg h−1) using a granular Na2CO3/γ-Al2O3 catalyst (loading of 650 g) to produce a high-grade bio-oil at a fast pyrolysis temperature of 475 ± 5 °C (pre-screened using a pyroprobe) and a catalytic upgrading temperature of 500 °C. Besides, > 99 wt% minerals in the paper sludge could be recovered, including paper fillers such as CaCO3 (major) and talc. The bio-oil obtained at a carbon yield of 21 C.% has a low oxygen content of 3.2 wt%, a low total acidity number of 5.2 mg KOH g−1, low H2O content of 0.7 wt%, and a high higher heating value of 40.9 MJ kg−1. It consists of value-added bio-based chemicals such as paraffins, olefins, and low molecular weight aromatics. The results demonstrate that the use of paper sludge to recover minerals and to obtain fuels and chemicals using ex-situ catalytic pyrolysis is technically feasible at a pilot plant scale, which will be of importance for the development of future bio-based economy.

Nano-Silica based mineral flotation frother: Synthesis and flotation of Platinum Group Metals (PGMs)

We report the synthesis and application of nanomaterials in the field of mineral processing. Nanotechnology is a potentially disruptive technology with a huge potential to open up new avenues of enhancing mineral recovery and grades in the domain of mineral froth flotation. In this investigation a solid, nano-silica (NS) based frother was synthesized using the sol–gel method for test works involving Platinum Group Metals (PGMs) and associated base metals. The nano flotation reagent was characterized using Fourier Transform Infrared Spectroscopy for chemical structure analysis (FTIR), Powder X-Ray Diffraction (P’XRD) for structural analysis and Field Emission Scanning Electron Microscopy (FESEM) for surface morphology and particle size distribution, Energy Dispersive Spectroscopy (EDS) for elemental analysis. X-ray fluorescence (XRF) was used for mineral assaying after flotation. The generated nano-silica had an average particle size distribution of 35–41 nm. The flotation performance of the nano-frother was benchmarked with a commercial conventional frother (SasFrother). At an optimum nano-frother dosage of 20 g/t a recovery of 73.8%, 77.0%, 84.0% and 78.2% platinum, palladium, nickel and copper respectively was realized. However, the associated grades were lower when compared with the conventional frother. On the other hand, increasing nano-silica dosage above the optimal dosage resulted in a reduction of the actual recovery for all the metals. Interestingly, the dosage requirement for the nano-frother required for optimal mineral recover was much lower than that of the conventional frother. Based on these findings, opportunities at nano scale can proffer numerous novel materials with exceptional properties for application in mineral froth flotation.

Preconcentration of Low-Grade Ta–Nb Deposit Using Physical Separation Methods

Ore from the Jinzhulong Ta–Nb deposit was processed using a combination of gravity concentration and magnetic separation to upgrade the columbite–tantalite fines. Two flowsheets, namely for gravity concentration–magnetic separation (the conventional flowsheet) and magnetic separation–gravity concentration (the novel flowsheet), are proposed herein, and the factors affecting the performance of gravity/magnetic separation were studied to optimize the flowsheets. Compared with the conventional flowsheet, the novel flowsheet was more effective for columbite–tantalite beneficiation and beneficial to the comprehensive recovery of nonmetallic minerals. In the novel flowsheet, the sample is ground to size of P80 = −74 μm then fed into a combination of a low-intensity wet drum magnetic separator and pulsating high-gradient magnetic separator to reject nonmagnetic gangue minerals while preconcentrating the paramagnetic columbite–tantalite; the high-gradient magnetic separation concentrates were screened into three size fractions and further upgraded by gravity concentration. The enrichment ratios for Ta2O5 and Nb2O5 were 403.8 and 385.6, respectively.

Modelling of Coupled Hydro-Thermo-Chemical Fluid Flow through Rock Fracture Networks and Its Applications

Most rock masses contain natural fractures. In many engineering applications, a detailed understanding of the characteristics of fluid flow through a fractured rock mass is critically important for design, performance analysis, and uncertainty/risk assessment. In this context, rock fractures and fracture networks play a decisive role in conducting fluid through the rock mass as the permeability of fractures is in general orders of magnitudes greater than that of intact rock matrices, particularly in hard rock settings. This paper reviews the modelling methods developed over the past four decades for the generation of representative fracture networks in rock masses. It then reviews some of the authors’ recent developments in numerical modelling and experimental studies of linear and non-linear fluid flow through fractures and fracture networks, including challenging issues such as fracture wall roughness, aperture variations, flow tortuosity, fracture intersection geometry, fracture connectivity, and inertia effects at high Reynolds numbers. Finally, it provides a brief review of two applications of methods developed by the authors: the Habanero coupled hydro-thermal heat extraction model for fractured reservoirs and the Kapunda in-situ recovery of copper minerals from fractures, which is based on a coupled hydro-chemical model.

Enhancing flotation separation of chalcopyrite and magnesium silicate minerals by surface synergism between PAAS and GA

Separation effects of sodium polyacrylate (PAAS) and gum Arabic (GA) on flotation of chalcopyrite and magnesium silicate minerals using potassium butyl xanthate (PBX) as collector were investigated by micro-flotation experiments, zeta potential, Infrared spectral (IR), SEM–EDS, XPS analysis and copper sulphide ore beneficiation test. The micro-flotation experiments and zeta potential measurements showed that combined depressant consisting of PAAS and GA could efficiently reduce the recoveries of mixed minerals of serpentine and talc more than 25%, while that of chalcopyrite remained above 70% at pH 9.2. Infrared spectral (IR), SEM–EDS and XPS analysis showed that PAAS chemically reacted with Mg on the surface of serpentine, while GA adsorbed on talc surface mainly via physical interaction and hydrogen bond may also play a role. Surface synergism between PAAS and GA was investigated by turbidity test and its depression mechanism was proposed. The technology feasibility of using PAAS and GA to improve the copper sulphide ore flotation performance was verified through artificial mixed ore flotation and laboratory closed-flotation operation.

Stabilization of heavy metals loaded sewage sludge: Reviewing conventional to state-of-the-art thermal treatments in achieving energy sustainability

Sewage sludge has long been regarded as a hazardous waste by virtue of the loaded heavy metals and pathogens. Recently, more advanced technologies are introduced to make use of the nutrients from this hazardous sludge. Successful recovery of sludge’s carbon content could significantly convert waste to energy and promote energy sustainability. Meanwhile, the recovery of nitrogen and trace minerals allows the production of fertilizers. This review is elucidating the performances of modern thermal treatment technologies in recovering resources from sewage sludge while reducing its environmental impacts. Exhaustive investigations show that most modern technologies are capable of recovering sludge’s carbon content for energy generation. Concurrently, the technologies could as well stabilize heavy metals, destroy harmful pathogens, and reduce the volume of sludge to minimize the environmental impacts. Nevertheless, the high initial investment cost still poses a huge hurdle for many developing countries. Since the initial investment cost is inevitable, the future works should focus on improving the profit margin of thermal technologies; so that it would be more financially attractive. This can be done through process optimization, improved process design as well as the use of suitable co-substrates, additives, and catalyst as propounded in the review.