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Bulk ore sorting is a preconcentration method applied to bulk streams or batches of material. The effectiveness of bulk ore sorting relies on the degree of the naturally occurring in situ grade heterogeneity of an ore deposit. The blending of ore during mining and material handling degrades the in situ grade heterogeneity initially present in an orebody and reduces the potential to apply bulk ore sorting. Block and panel cave mines experience mixing from the establishment of caves to the delivery of the caved ore to concentrators. This study focused on tracking the grade heterogeneity and quantifying the impact of mixing on the sorting potential of the Cadia East panel cave mine via the reconciliation of the grade measurements performed at different locations. The results showed that the copper and gold grades were almost fully homogenized via various mixing events identified for the mine. The tracked grade heterogeneity values revealed that the mixing during material handling, which included ore blending according to mine planning, reduced the grade variability more drastically than the mixing within the caves. As the ore travelled from its original in situ location, the grade distributions gradually transformed, and the grades eventually normalized around the mean values. Only insignificant amounts of low-grade material that could have potentially been discarded were reported to the on-belt sensor located at the surface. The results of this study are significant for cave mines exploring sorting systems for preconcentration as they highlight how mixing can impact the variability in ore grades. [ABSTRACT FROM AUTHOR]

Ore grades are monitored regularly in cave mines through drawpoint sampling. Automating grade monitoring through deploying X-ray fluorescence (XRF) sensors on the buckets of production loaders has been proposed as an alternative approach to address the issues around the traditional practice of drawpoint sampling. Bucket-mounted sensors can also be employed for bulk ore sorting underground. This study is aimed at evaluating the deployment of XRF sensors on production loaders as an opportunity for grade monitoring or bulk ore sorting in caving operations. The mill feed grade prediction performances of the drawpoint sampling program and mine planning software were assessed for the Cadia East panel cave mine. The results showed that the drawpoint samples underestimated the mill feed quality during a 10-month investigation period. The cave portions with bulk ore sorting potential were linked to the extraction level layout to estimate the number of drawpoints where sensors could be situated for diverting ore and waste. Samples obtained from the mine were tested to evaluate the ability of a lab-scale proxy of a bucket-mounted XRF sensor system to measure copper and gold grades. R-squared values of 0.84 and 0.68 were achieved between the predicted and measured copper and gold grades of the samples, respectively. Sensor test results are promising in revealing the potential to utilize XRF sensors underground. Future test work is encouraged to further validate the applicability of XRF sensors in an underground mining environment. [ABSTRACT FROM AUTHOR]

Sizing High-Pressure Grinding Rolls (HPGR) requires a large quantity of material, making it not attractive and costly to be considered for new mining projects regardless of their energy consumption reduction benefits. Ongoing efforts are being made at the University of British Columbia to predict the behaviour of the HPGR using a low quantity of material on a piston-and-die press apparatus. Although the energy requirements and size reduction predictive models are already developed, there is still a need to predict the HPGR throughput on a small-scale test. This paper presents a new model to predict the HPGR throughput based on the previously developed model to predict the operational gap by using less than 2 kg of sample. The throughput model was developed using machine learning techniques and calibrated using pilot-scale HPGR tests and piston press tests. The resulting model has an R2 of 0.91 with an average prediction error of ±4.2%. The developed methodology has the potential to fill the gap of the missing throughput model. Further pilot-scale HPGR testing is required to continue validating the model. [ABSTRACT FROM AUTHOR]

• PGNAA and MR can be used simultaneously for bulk ore sorting of copper porphyries. • Integration is key for deposits with varying bornite and chalcopyrite ratio. • A greater increase in ore value is estimated when the sensors are used together. Bulk ore sorting is a preconcentration technique that may address the operational and environmental challenges of extracting low-grade ore deposits, such as copper porphyries. The technique allows for the early detection and diversion of sub-economic material by sensor-diverter systems before milling, thereby improving mill feed quality and reducing environmental impact. Grade heterogeneity in ore and sensor capability to measure grade accurately are prerequisites to applying bulk ore sorting. The technical synergy between the responses of multiple bulk ore sorting technologies can aid in taking full advantage of the grade heterogeneity existing in sorter feed while providing accurate and precise grade measurements. This study is aimed at quantitatively demonstrating the potential benefits of a conceptual strategy of integrating the responses from two sensor technologies for bulk ore sorting of copper porphyry deposits. Results show that a more significant enhancement in the Net Smelter Return (NSR) of the ore can be achieved by the simultaneous employment of the magnetic resonance (MR) and prompt gamma neutron activation analysis (PGNAA) sensors compared to the bulk ore sorting scenarios in which the sensor technologies are utilized separately. Results are encouraging and can prompt the collaboration of sensor manufacturers and mining companies to prove the actual value of the presented concept by performing on-site trials. [ABSTRACT FROM AUTHOR]

Ultra-fine cemented backfill (UCB) materials display distinctive rheological characteristics. This paper examines the rheological behaviors of UCB composited with cement and tailings that have a 80% cumulative passing size (d (80) ) of 9.72 µm. The findings were that UCB samples exhibit time-dependent non-Newtonian behaviors with a shear thinning characteristic, and both thixotropy and rheopexy properties are observed under long periods of steady-state shearing (300 s −1 shear rate). The results indicate that samples sheared at higher rates display lower apparent viscosities compared to the samples sheared at lower rates. At low shear rates (≤0.5 s −1 ), apparent viscosity increased until it reached a local peak (or two peaks) before behaving similarly to samples tested at higher shear rates. It was also found that the apparent viscosity of UCB increased consistently as the solids content was increased. Moreover, as cement content was increased, the apparent viscosity rose until it reached a peak at a cement content of 6%. The results also confirmed effects of solids concentration profiles changing over time and the cement hydration on the rheological behavior of UCB. [ABSTRACT FROM AUTHOR]

• Logistic regression and support vector machine modeling were developed for ore classification. • Principal component analysis combined with stepwise regression was used for processing XRF spectral data. • Logistic regression outperforms SVM with kernel functions especially on small sized data. The study is aimed at particle sorting at the Copper Mountain Mine using XRF. Possible applications include the rejection of barren material from mill feed, the rejection of pebbles in the SABC circuit or the recovery of valuable material from low grade stockpiles. It is recognized that XRF is a surface measurement that can detect copper but depending on several operational conditions, such as the orientation of the particle or mineral texture, the sensor spot may not see the copper. However, XRF also provides information about the concentrations of a range of elements in minerals that are associated with copper mineralization which can improve sorting. The study described herein is aimed at improving XRF sensor-based sorting by the introduction of logistics regression (LR)- and support vector machine (SVM)-based machine learning approaches. To solve the collinearity and dimensionality issues in the input variables, the authors propose a combined approach of principal component analysis (PCA) and stepwise regression to extract the significant features. The combined PCA and stepwise regression approach is novel and has shown to be very effective for dimensionality reduction of the XRF spectrum data. By applying the ROC and AUC), the LR and SVM models are compared. Results showed that the LR model with the AUC of 0.847 outperforms the SVM with kernel functions with respect to classification accuracy; especially for data sets with a small number of features. The improved classification accuracy should benefit the economic performance of the particle sorting system. [ABSTRACT FROM AUTHOR]

Conceptual bulk ore sorting studies are essential for determining a potential improvement in mine economics before undertaking on-site sensor trials. Two approaches, block modelling and drill core compositing, are applied to simulate the bulk ore sorting performance of mining operations. While one employs the grade data of a block model, the other approach utilizes composited drill core grades. This study aimed at comparing these two approaches by estimating in-situ grade heterogeneities and simulating the bulk ore sorting performances of the currently active caves of the Cadia East panel cave mine. The results show that block modelling tends to smooth the grade variability that initially exists in the drill core grade data. Particularly in the portions of the deposit where drilling is sparse or widely spaced compared to the selected block size, block modelling leads to lower grade heterogeneity and bulk ore sorting performance estimates. However, when the drill hole data is nonrepresentative of the area of interest, block modelling can predict more realistic bulk ore sorting performances compared to drill core grades. The assessments performed with the blocks and drill core composites of various sizes showed that grade heterogeneity was adversely affected by an increased sorting scale due to averaged metal grades. [ABSTRACT FROM AUTHOR]

An iterative hybrid performance improvement approach integrating artificial neural network modelling and Pareto genetic algorithm optimisation was developed and tested. The optimisation procedure, code named NNREGA , was tested for tuning pilot scale Continuous Variable Discharge Concentrator (CVD) in order to simultaneously maximise recovery and upgrade ratio of gold bearing sulphides from a polymetallic massive sulphide ore. For the tests the CVD was retrofitted during normal operation on the flotation tailings stream. On the basis of mineralogical data showing strong pyrite-gold association in the flotation tailings, iron assays were used as an indicator of CVD performance on recovery of gold bearing sulphides. Initially, 17 pilot scale statistically designed tests were conducted to assess metallurgical performance. The Matlab 2010a software was used to train and simulate back propagation ANNs on experimental results. Regression models developed from simulation data were used to formulate the objective functions used to optimise the CVD using the NSGA-II genetic algorithm. Results show that the NNREGA procedure provides an efficient way of exploring the design space to learn the relationship between interacting variables and outputs and is capable of generating the operating line, which is a non-dominated recovery/grade line. The paper forms a basis for future work aiming to model and scale up processing equipment. [ABSTRACT FROM AUTHOR]

A method for determining the minimum practical energy for comminution was developed and is presented in this paper. An objective of the method was to determine experimentally the energy-breakage relationship for a wide size range in order to evaluate the energy performance of both crushing and grinding processes using one energy benchmarking value. Single-particle compression breakage, referred to in the field of comminution as one of the more efficient forms of mechanical comminution, was the basis for a test regimen to characterize the energy-breakage properties of ores. Existing models for impact breakage were found to be valid for single-particle compression breakage when used in a modified form. A key parameter of the adopted model, the threshold energy, was also investigated for three ore types and a range of particle sizes. The energy performance of comminution processes at a Canadian mining operation was determined by comparing the determined minimum practical energy, using the new method, with actual site specific energy requirements. In order to evaluate the energy performance of different crushing and grinding technologies, the proposed energy benchmarking method was used to compare the energy performance of alternative comminution flowsheets. [ABSTRACT FROM AUTHOR]

• Nine influential factors were integrated in a mathematical framework based on fractal modelling approach. • The influence of various factors on the ore sortability were investigated. • Factors of significant influence were identified. The uptake of bulk ore sorting technology is hindered by little knowledge in assessing its applicability for certain mine operation. The applicability of the bulk ore sorting technology, referred to as 'sortability', is a multi-folded concept and is influenced by many factors. Researchers have investigated the influence of some of the various factors, but few have done this in a holistic perspective and in a quantitative manner. In this research, nine influential factors of ore sortaibility were integrated in a mathematical framework based on fractal modelling approach. Box-Behnken design was applied and 130 block cave mine operations were hypothesized under different values of the factors. The influence of the factors on the ore sortability were investigated and factors of significant influence were identified. Results showed that ore property, sorting efficiency, metal price, processing cost and operation scale were the most significant factors in affecting the sortability for a mine operation. The research is intended to improve the understanding on the bulk ore sortability for mine productions under different conditions, and to provide a holistic perspective for applying the bulk ore sorting technology. [ABSTRACT FROM AUTHOR]

Abstract: The contamination of groundwater with arsenic is a serious health issue in many parts of the world. Although iron has been shown to be effective at removal of arsenic from water, there has been no research to assess the feasibility of using natural iron oxide minerals for water treatment. The successful treatment of water to remove arsenic requires an understanding of arsenic chemistry and the physical–chemical interactions between arsenic and iron oxide minerals. A study was conducted to evaluate hematite, magnetite, goethite and iron rich laterite soil as arsenic adsorbents. Electroacoustic measurements were conducted to assess the nature of arsenic adsorption. Results showed that arsenic adsorption occurred over the entire pH range tested (pH 4–11). The isoelectric point shifted due to arsenic adsorption and this is a strong evidence of specific ion adsorption. This was supported by leaching tests that indicated strong attachment of arsenic to the surface of iron oxide minerals. Adsorption tests showed that iron rich laterite was most effective for arsenic removal, followed by goethite, magnetite and hematite. This was attributed to the higher specific surface area of the respective minerals. The study also demonstrates a simple water treatment method involving the use of low cost natural ironoxide minerals for arsenic removal to meet drinking water standards. Treatment of 100 mL of water containing 20 ppm arsenic with 5 g of laterite reduced the arsenic level down to 10 ppb within a period of 10 min. [Copyright &y& Elsevier]

Highlights: [•] Stirred milling kinetics was studied on the siliceous goethitic nickel laterite. [•] The breakage behaviour was evaluated with respect to sample mass, element, and minerals. [•] The effect of selective grinding was evaluated by three methods. [•] The effect of grinding time, feed size, and product size on selective grinding was evaluated. [Copyright &y& Elsevier]

Abstract: The contamination of groundwater with arsenic is a serious health issue in many parts of the world. Although iron has been shown to be effective at removal of arsenic from water, there has been no research to assess the feasibility of using natural iron oxide minerals for water treatment. The successful treatment of water to remove arsenic requires an understanding of arsenic chemistry and the physical–chemical interactions between arsenic and iron oxide minerals. A study was conducted to evaluate hematite, magnetite, goethite and iron rich laterite soil as arsenic adsorbents. Electroacoustic measurements were conducted to assess the nature of arsenic adsorption. Results showed that arsenic adsorption occurred over the entire pH range tested (pH 4–11). The isoelectric point shifted due to arsenic adsorption and this is a strong evidence of specific ion adsorption. This was supported by leaching tests that indicated strong attachment of arsenic to the surface of iron oxide minerals. Adsorption tests showed that iron rich laterite was most effective for arsenic removal, followed by goethite, magnetite and hematite. This was attributed to the higher specific surface area of the respective minerals. The study also demonstrates a simple water treatment method involving the use of low cost natural ironoxide minerals for arsenic removal to meet drinking water standards. Treatment of 100 mL of water containing 20 ppm arsenic with 5 g of laterite reduced the arsenic level down to 10 ppb within a period of 10 min. [Copyright &y& Elsevier]

Abstract: Increasing energy efficiency and reducing water consumption are two of the key requirements in moving toward a more sustainable mining industry. This paper demonstrates a method of determining the lowest energy option for a mine/mill water system network. The method uses a linear programming algorithm to compare different possible combinations of supplying water to mine and mill consumers. First, a site water balance is determined and then every major water consumer and source is specified. Water sources may require pumping, cooling and/or treatment before the water meets the specifications of the water consumer. The amount of energy required for each water source to supply each consumer is calculated and then the model is solved to minimize power consumption. An example is used to illustrate the method. [Copyright &y& Elsevier]

• The developed fractal model was validated on mine production data. • The multifractal model was proposed for bulk ore sortability assessment. • The multifractal model was more accurate in predicting the sorting results and assessing ore sortability. A previous study demonstrated the theoretical development of a model for assessing bulk ore sortability. However, the model has not been validated with many cases. In this study, the developed model was validated using the production data from 232 draw points in a block cave copper mine. For each draw point, sorting results and mine economics were predicted using fractal modelling and compared with results based on actual data analysis. The statistical error was measured for the fractal model predictions of feed grade, mass yield, pre-concentrate grade, metal recovery, and NSR with and without bulk ore sorting. An optimised approach was developed using multifractal modelling; two sets of fractal parameters were determined to characterise the metal distribution in high- and low-grade ranges. The results showed that the multifractal model was more accurate than the fractal model in predicting the sorting results and assessing ore sortability. [ABSTRACT FROM AUTHOR]

• The potential of bulk ore sorting application at a block cave mine was investigated. • The grade heterogeneity and sortability was evaluated for different mining zones. • The relationship between ore grade heterogeneity and sortability was discussed. A block cave mine operation was investigated in terms of ore grade heterogeneity and the potential of bulk ore sorting application. The grade heterogeneity within the caved material was measured for different draw points and mining zones, in terms of Distribution Heterogeneity and Fractal Dimension. The potential of bulk ore sorting was assessed by comparing the Net Smelter Return before and after a hypothetical bulk ore sorting system was implemented. Results showed that the potential of applying bulk ore sorting was influenced greatly by the heterogeneity within the mined material. A certain level of heterogeneity was necessary in considering the mine production as 'sortable'. The sortability would also vary for different mining areas depending on heterogeneity level of the production. Peripheral zones of the orebody were considered with the highest level of heterogeneity and the most significant potential of bulk ore sorting application. [ABSTRACT FROM AUTHOR]

• Error analysis was conducted on the XRF measurements of ore materials at lab-scale. • Three main types of errors were identified associated with XRF measurements. • The applicability of XRF in bulk ore sorting applications was discussed. X-Ray Fluorescence is one of the sensing technologies with potential in bulk ore sorting application. However, its reliability is often questioned since X-Ray Fluorescence does not sufficiently penetrate and errors are associated with surface measurements representing the volumetric grade. In this paper, error analysis was conducted on the XRF measurements on bulk ore materials at lab scale. Three main sources of the errors were identified, termed as instrumental error, heterogeneity error and the sampling error. Among the errors, the heterogeneity error was identified as the most significant due to its irrelevance with measuring the concentration and the unpredictability of that value. The influence of the errors on the conventional linear regression approach was investigated in terms of the sorting results and economics. Results showed that the linear regression approach was expected suitable for cases when sufficient analysis interval time could be ensured. It this was allowed for, the applicability of XRF in the bulk ore sorting was fundamentally justified. [ABSTRACT FROM AUTHOR]

• Receiver Operating Characteristic (ROC) was applied in ore classification for bulk ore sorting. • ROC approach was found to result in more accurate classification compared to SLR. • Economics performance was enhanced by ROC approach compared to that of SLR. As high grade deposits become depleted, the mining industry is challenged by mining lower grades that require the use of non-selective bulk mining methods. Bulk ore sorting can reduce the dilution of the mined ore thereby preventing costly processing of low grade waste while improving the quality of material reporting to the processing plant. X-Ray Fluorescence (XRF) is one of the sensing technologies used for bulk ore sorting. The grade of the bulk material is predicted based on XRF measurement that is correlated to a grade using a calibrated algorithm. The effectiveness of XRF bulk sorting depends on the accuracy of the grade classification of the scanned material. False classification is attributed to poor performance of the sorting algorithm to correlate the measurements with the assay grades. The paper presents an approach to analyze XRF measurements that reduce misclassification of material. Receiver Operating Characteristic (ROC) was applied as the tool in classification of bulk materials. The performance of this approach was compared to conventional sorting algorithm, namely, simple linear regression (SLR), where XRF responses was linearly correlated to the assay grades. The ROC approach was found to result in more accurate classification and enhanced economics performance of the bulk ore sorting system. [ABSTRACT FROM AUTHOR]

• A bulk ore sorting model was developed for sortability assessment. • Metal distribution within ore deposits was recognized as a fractal structure. • The optimum cut-off grade was determined based on model calculations. Bulk ore sorting (BOS) has the potential to reduce processing costs and improve mine economics. A factor that impedes its acceptance is the lack of a method to assess ore amenability to sorting. In this study, a fractal model of metal distribution was used to assess an ore's bulk sortability. A BOS model was developed where metal distribution properties were characterised, optimum cut-off grade for sorter operation was determined, and economic potential of BOS was evaluated. For the developed model, the metal distribution within the ore deposits was recognised as a fractal structure. Two parameters were introduced, namely the grade factor and fractal dimension, to quantitatively characterise ore properties in terms of grade magnitude and heterogeneity. The mass balance of the sorter operation was modelled as a function of the characterised ore properties and the optimum cut-off grade was determined based on model calculations. The economic potential of BOS was evaluated in terms of the net smelter return and compared with that when no BOS was implemented. Based on the developed model, the bulk ore sortability of different ore properties was assessed with a hypothetical underground copper mine. The developed BOS model provided a powerful tool for ore sortability assessment and is expected to encourage academic research and industrial practices of BOS. [ABSTRACT FROM AUTHOR]

[Display omitted] • 27 laboratory HIG5 grinding tests are performed for modelling the influence of operational variables. • Stress analysis is applied for understanding laboratory variables' correlation with their production level. • Correlation factors are determined based on empirical fitting with production data. • Laboratory models are calibrated for predicting and improving large-scale mill performance. As a fine and ultrafine grinding technology, the High Intensity Grinding (HIG) Mill is relatively new and there is opportunity to improve its performance by adjusting operational conditions. A laboratory HIG5 mill is commonly used for HIG mill sizing and scale up, however the clear correlation between the operational variables of laboratory mill to their production level is somewhat lacking. This paper presents a stress-based approach for predicting and improving large-scale HIG mill performance. A total of 27 experimental tests were performed with a HIG5 mill over a range of operational variable set points, including media density, media filling level, feed solid content, mill speed and flow rate. The influence of the variables on product size, mill operating power and specific grinding energy was characterized via multivariable linear regression modelling. Based on theoretical stress analysis and empirical calibration with available survey data, the model derived from laboratory testing was calibrated to predict the operation of the commercial HIG1600 mill. An approach was proposed for determining the effect of operational variables using a HIG5 that can be directly applied to reduce energy consumption at a given mill feed rate and product size target for the production scale mill. Results demonstrated that the stress-based approach integrated with laboratory testing can be used for predicting and improving large-scale HIG mill performance. [ABSTRACT FROM AUTHOR]

Both shear and flocculation have a significant influence on the rheological behavior of tailings, especially the yield stress. In the two-step flocculation process, the above two kinds of actions exist at the same time, and they influence each other. In order to explore the change rule of the yield stress and its internal causes, a two-step flocculation process of the iron ore fine tailings with different shear conditions in the four different phases was designed. In the primary flocculation phase, tailing particles combined with the primary flocculant and formed a primary floc network structure. In the primary broken phase, shear destroyed the primary floc network structure and decreased the average floc size, so the shear-dependent yield stress, the floc strength factor, and the fractal dimension decreased. In the secondary flocculation phase, broken floc combined with the secondary flocculant and produced a more compact floc network structure which had a better shear resistance. Therefore, in the secondary broken phase, with the increase of shear, the decrease of yield stress, the floc strength factor, and fractal dimension were less obvious than that in the primary broken phase. In both two broken phases, the yield stress of the secondary flocculating slurry was always higher than that of the primary flocculating slurry, but with the increase of shear, the difference became smaller. The floc strength and fractal dimension also showed the same rule. The internal reasons for the stronger shear resistance of the secondary flocculating slurry were the increase of the number of binding sites, the electric neutralization between the two flocculants, and the steric hindrance effect of the flocculants. [ABSTRACT FROM AUTHOR]

• Even with the ideal conditions, bulk ore sorting may not be applicable. • Metal losses limit the value associated with bulk ore sorting. • Good correlation between copper and gold is required for effective ore sorting. Bulk ore sorting may add significant value to block and panel cave mines where processing feed grades are constrained by limited grade selectivity. The Cadia East gold-copper mine is a panel caving operation utilizing two different on-belt bulk ore sensors to evaluate the potential benefits of the technology. To date, there is limited reported work addressing the applicability of bulk ore sorting systems at a caving mine, where two commodities drive the economics. This indicative study is aimed at investigating the importance of various key factors on the bulk ore sorting potentials of the active and future panel caves of the Cadia East mine. Results show that for only one active cave of the mine, bulk ore sorting may be applied in the ideal scenario where grades are not affected negatively by mixing and the sorting takes place at maximum efficiency. As a general trend for all the caves, when the sorting cut-off grade is increased beyond a certain threshold, a sharp decline is observed in the sorting potentials due to the significant amounts of gold and copper deporting to the sorter rejects. In the case of a significant drop in metal prices, bulk ore sorting may only provide an opportunity to improve cave economics marginally. Results obtained by investigating the spatial change in sorting potential show that the portions of the caves with low metal grades are favourable for bulk ore sorting. In the scenario where bulk ore sorting is focused on low-grade portions, it is demonstrated that improvements in the economics of the future caves may additionally be achieved. However, as the low-grade portions represent a very small volume in the orebody, applying ore sorting on the plant conveyor may not be viable. [ABSTRACT FROM AUTHOR]

To support the transformation to clean low carbon technologies, there is a demand for critical metals such as nickel. Awaruite is a less common nickel-bearing mineral with unique properties and responses to mineral separation. This paper presents the findings of a flotation study to recover awaruite from the Baptiste ultramafic deposit, located in central British Columbia, Canada. Nickel recoveries of up to 65% at the rougher stage were obtained with xanthate as a collector at a pH level of 4.5. Awaruite flotation was shown to be highly dependent on the slurry pH. At weakly acidic conditions, the awaruite surface is activated through the dissolution of the passivation layer formed during grinding in alkaline conditions. Desliming was shown to reduce the acid consumption required to maintain the pH, probably by removing the highly reactive serpentine slimes generated during grinding. Rougher, followed by cleaner stages of flotation, showed that a high-grade concentrate can be produced with up to 45% nickel, 1.3% cobalt, 0.7% copper and negligible concentrations of penalty elements, such as arsenic, lead, and selenium, among others. A nickel flotation concentrate from an awaruite deposit is a promising feedstock for not only stainless-steel production but also for clean energy technologies. [ABSTRACT FROM AUTHOR]

• Conjugate Anvil Hammer Mill (CAHM) was studied using experimental piston-die testing. • The semi-confined and confined compression were compared. • Higher energy efficiency of CAHM compression breakage was found compared to HPGR. The Conjugate Anvil Hammer Mill (CAHM) was identified as a novel energy efficient technology by the Canadian Mining Innovation Council that has the potential to replace conventional crushers and Semi-Autogenous Grinding (SAG) mills. Discrete Element Method (DEM) modelling showed that the CAHM requires significantly less energy in comparison to existing comminution technologies including High Pressure Grinding Rolls (HPGR). However, experimental evidence was required to validate this potential and to address operational questions. In order to evaluate the CAHM, piston-die testing was conducted to represent the comminution conditions in the CAHM for comparison to the HPGR. Three piston-die conditions were tested including low pressure semi-confined compression as generated in the CAHM, low pressure confined compression, and high pressure confined compressions as generated in the HPGR. The particle breakage was investigated and compared in terms of applied force, energy consumption, product particle size reduction and particles' surface area generation. Results showed that the CAHM test apparatus required a much lower force and produced a finer product particle size distribution and higher surface area when compared to low pressure confined compression. When compared to high pressure confined compression (HPGR), up to 37% and 22% energy savings were achieved by the CAHM for a soft gold ore and a harder copper ore, respectively. The results demonstrated that the CAHM technology has potential to improve energy efficiency in the comminution process. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • With anionic or nononic polymer as primary flocculant, two-step flocculation was used for iron fine tailings treatment. • Better flocculation effect was achieved with the single nononic flocculant, but a higher water recovery rate was obtained with anionic primary flocculant. • Broken flocs produced by anionic flocculant had larger strength factors and a more significant reversibility with the appropriate amount of the cationic flocculant and they also achieved a higher total water recovery rate. • Flocs size distributions were measured and strength factor and recovery factor were calculated for mechanism study. • The flocculation mechanism involves polymer bridging and charge neutralisation. Abstract Dewatering of fine tailings is one of the major challenges faced by the mining and mineral processing industries worldwide. In order to facilitate the separation of released water and solid sediments, different kinds of polymeric flocculants and their combinations have been widely used. A two-step flocculation experiment using two separate primary flocculants in alkaline environment was carried out in this study. The underflow concentration of the two-step flocculation process was higher than that of any single flocculant. Compared to the widely-used flocculation process with a single polymer flocculant, this two-step process could not only significantly improve the total water recovery rate of the slurry, it could also produce a full re-growth of flocs. The first part of the study compared the effects of adding 2 different flocculants to the slurry under alkaline conditions: a non-ionic flocculant, and an anionic flocculant. Compared to the anionic flocculant, the addition of the non-ionic flocculant resulted in a more compact structure and a higher strength by bridging. Conversely, after shear disruption and the addition of the cationic flocculant to the slurry, the re-aggregating broken flocs produced by the anionic flocculant in the first step resulted in a higher reversibility, the formation of a closer and more complex floc structure, and consequently a higher total water recovery rate. This was achieved by drastically re-aggregating broken flocs through the addition of a cationic flocculant that neutralized the charge of the slurry, which in turn is an indication of significant reversibility of the floc break-up process. The dosage of the secondary flocculant had an optimal value to achieve the maximum total water recovery rate. If the dosage exceeded the optimal value, the interaction between the flocculant molecules adsorbed on the same floc occured, which hindered the re-aggregation of flocs and even reduced the secondary water recovery of the slurry. [ABSTRACT FROM AUTHOR]

The productivity of milling circuits is sensitive to the size of mill feed. Uncertainty about the size of caved ore presents unique challenges to forecasting and controlling mill throughput rates. Part I of this paper showed how fragmentation size and hang-up frequency relate to geology, proximity of drawpoints to the cave boundary and the height of draw at the New Afton mine. The second part, presented here, investigates the impact of varying caved fragment size on mill performance. Analysis of historical mine and mill data showed that mill feed size and subsequently mill throughput are sensitive to the areas being mucked within the cave. Fragmentation measurements of drawpoint muck, comminution tests and calibrated mill models were used to assess the impact of variations in feed size and hardness on New Afton mill performance. Image-based size analyses of drawpoint muck and comminution tests showed that coarser material generally contained harder rock. [ABSTRACT FROM AUTHOR]

Block and panel caving mines are increasingly being proposed for the excavation of massive ore-bodies located at depth. The lack of selectivity associated with the mining methods results in both ore and waste being caved and transported through material handling systems to the surface for processing and waste rock disposal. Sensor-based sorting systems provide an opportunity to automate the discrimination between ore grades and rock types, providing an enhanced level of selectivity for ore control and thereby improving mine productivity. To evaluate the potential to add value to a caving operation, a sensor-based ore sorting study, incorporating bulk and particle sorting systems, was carried out for the New Afton block cave mine. Results showed that rock from the copper-gold porphyry deposit is amenable to prompt gamma neutron activation analysis, and to X-ray fluorescence sensors. A conceptual flowsheet, where both technologies are used as separate unit operations, was evaluated. Test samples of varying copper head grades allowed an ore value calculation method to be developed based on the integration of continuous bulk sorting and particle sorting. The calculation method can be applied to block models of a future cave at New Afton and used to evaluate the change in the economic footprint. It was found that the concept demonstrated an improvement in the net smelter return of excavated material. [ABSTRACT FROM AUTHOR]

As an experimental study, the research in this paper was conducted to illustrate the influence of solids content and composition of cemented paste backfill (CPB) on the material's rheological and mechanical characteristics. A new type of CPB was used in this research, which was composed of waste rock as coarse aggregates, fly ash as fines, lime slag as activator proportions and ordinary Portland cement as binder. The mechanical strength of CPB improved significantly with an increase in the solids content, but the workability decreased because the water content decreased. When the solids content was 75% by weight (wt.%), the slump value was 165 mm, which met the requirement for pumping. At a solids content of 75%, the CPB also had an unconfined compressive strength (UCS) of 1.83 MPa, tensile strength of 0.401 MPa, and Poisson's ratio of 0.136 at a curing time of 28 days. Increasing the fly ash proportion caused the workability and mechanical strength of the CPB to increase until they reached maximum values, at which point subsequent increases caused the values to decrease. The workability of CPB reached its peak when fly ash proportion was 35 wt.%, and the mechanical strength reached its peak at 45 wt.%. The workability of CPB decreased as the lime slag proportion increased. The strength of CPB also increased with an increase in the lime slag proportion, however, only until it reached 12 wt.%, at which point the strength began to decline. The addition of more cement resulted in much better mechanical performance of the CPB samples, especially with longer curing times. However, workability of CPB increased as cement portion increased in the range of 0% to 2.5%, before decreasing over the range of 2.5%–5.0%. [ABSTRACT FROM AUTHOR]

Using a cluster of pebbles to generate clumps is a common procedure to explore granular particles' micro- or macro-scale mechanical responses in DEM simulations. The struggle is to balance the number of pebbles and the shape accuracy of generated clumps compared to the original particles. A low-cost multi-image-based method is adopted in this paper to extract 3D triangular networks of original particles. A voxel-based clump generation method, namely V-CLUMP, is developed to generate clumps based on triangular networks. The operations, such as gradual discretization, surface cell optimization, and candidate pebble hollowing out, are proposed to improve the accuracy and efficiency of clump generation. The ideal of corner preserving is also adopted, and a novel image-based method to detect corners and ridges of particles or clumps is proposed in this paper. Clumps for four idealized geometrical shapes and five quintessential particles are generated using the V-CLUMP. The parameters, including the number of pebbles, volume, projection area, sphericity, roundness, and roughness, are used to evaluate the performance of the clump generation method proposed in this study. The result shows that the absolute value of the errors for most generated clumps with 30 to 120 pebbles in macro-scale descriptors, i.e., volume, projection area, and sphericity, are less than 6%. A better result of meso- and micro- descriptors, i.e., roundness and roughness, can be obtained by selecting optimum clump generation parameters. The code takes less than one second to a few minutes, within the acceptable limits. However, pebble hollowing out and corner detecting are still time-consuming, and more efficient algorithms are needed to improve the performance of the operations. [ABSTRACT FROM AUTHOR]

Adsorption with activated carbon (AC) is an important method for the treatment of heavy metal wastewater, but there are still certain challenges in the separation and reuse of activated carbon. The preparation of magnetic activated carbon (MAC) by modifying AC is one of the effective means to realize the separation of AC from solution after the adsorption process. In this work, lignite and poplar leaves were used as raw materials for co-pyrolysis, and the co-pyrolysis char was activated and modified to prepare MAC. The structure and properties were characterized by VSM, N2 adsorption, SEM, XRD, and FT-IR. At the same time, the adsorption performance of MAC on wastewater containing Pb and Cd ions was studied. The results show that the prepared MAC contains Fe3O4, and the saturation magnetization (Ms) of the MAC is 13.83 emu/g; the specific surface area of the MAC is 805.86 m2/g, and the micropore volume is 0.23 cm3/g; the MAC exhibited a good porous structure. When the pH value of the solution was 5, the adsorption time was 120 min, the dosage of MAC was 4 g/L, the initial concentration of Pb ion solution was 50 mg/L, and that of Cd ion solution was 25 mg/L, and the adsorption temperature was 30 °C, the adsorption efficiency of Pb, Cd ions were 84.40 and 78.80%, respectively, and the adsorption capacities were 10.55 and 4.93 mg/g, respectively. The adsorption of Pb and Cd ions by MAC conforms to the Langmuir adsorption model, which is a monolayer adsorption. The adsorption process is mainly chemical adsorption, which can be better described by the pseudo-second-order model. The adsorption thermodynamic analysis showed that the adsorption of Pb and Cd ions by MAC was a spontaneous reaction, and the higher the temperature, the stronger the spontaneity. [ABSTRACT FROM AUTHOR]

The combined hydrometallurgical and pyrometallurgical process is an innovative method for recycling spent batteries. This process includes a carbothermic reduction step that reduces the valence of valuable metals in the batteries, facilitating subsequent leaching, which is a crucial stage in the recycling process. Additionally, the use of new carbon materials in electrode materials for ternary lithium batteries, referred to as LIBs, is increasing. These materials typically have high porosity and a large specific surface area. In this study, two types of nanoporous carbon (NC) commonly used in electrodes, namely Al-PCP-800 and ZIF-8–800, were prepared to investigate their effects on the carbothermic reduction stage of recycling spent batteries. The carbothermal reduction reactions of spent LIBs powder mixed with activated carbon and the two types of NC were examined using a thermogravimetric balance (TG/DTG). Kinetic characteristics were calculated in the interval of maximum weight loss rate using five kinetic models: VM, RPM, URCM, KAS, and FWO. The kinetic analysis revealed that the KAS and FWO models, which exhibited higher correlation coefficients, more accurately described the carbothermic reduction reactions. TG analysis showed that the sample mixed with 25 % ZIF-8–800 achieved the lowest temperature at the weight loss peak for the maximum weight loss rate, 769°C at a heating rate of 20 °C/min. Additionally, the reaction activity of NC with the positive material in the spent LIBs powder was stronger than that of activated carbon. Among the models, the sample mixed with 25 % ZIF-8–800 exhibited the lowest activation energies, recorded at 171.83, 28.48, 122.22, 199.49, and 143.45 kJ/mol, respectively. XRD and XPS characterizations of the roasted products from the spent LIBs powder mixed with the three carbon materials at various roasting end temperatures demonstrated that the cathode materials initially decomposed into Mn 3 O 4 , NiO, CoO, Li 2 O, and Li 2 CO 3. At higher temperatures, Mn 3 O 4 , NiO, and CoO were further reduced to MnO, pure metallic Co, and pure metallic Ni, respectively. The sample mixed with ZIF-8–800 showed the most substantial reduction of metallic elements, with the relative contents of pure metallic Ni, pure metallic Co, and low-valent Mn elements reaching 5.50 %, 4.41 %, and 71.29 %, respectively, at a final roasting temperature of 800 °C. Therefore, NC demonstrated greater reactivity in the reduction reactions with the cathode material in the spent LIBs powder, ranking in the order of ZIF-8–800 > Al-PCP-800 > activated carbon. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: In many countries, such as Brazil, Colombia, Ecuador, Indonesia, Venezuela and Zimbabwe, amalgamated tailings are leached with cyanide to recover remaining gold. This paper describes a recently completed study conducted at seven gold processing centers in Portovelo-Zaruma, Southern Ecuador, which involved consultation with local miners. The objective of the study was to understand the behaviour of mercury (with a focus on mercury loss) in artisanal gold mining operations through the evaluation of two cyanidation processes (Merrill-Crowe and Carbon-in-pulp), using a participatory approach. In order to assess the kinetics of mercury dissolution in cyanide, a bottle roll test was conducted in the laboratory. In the Merrill-Crowe cyanidation process, an average of 24.2% of metallic mercury was determined to be trapped at the bottom of the agitation tanks; 33.1% of mercury is lost in association with solid material and 11.7% is lost in solution. Approximately 31.0% of mercury in solution is sent to the zinc precipitation cells from which 27.8% is precipitated on the zinc shavings, with 3.23% remaining in solution. The mercury precipitated on to the zinc is lost to the atmosphere when the shavings are burned at 900 °C. In the Carbon-in-pulp (CIP) leaching system, 11.2% of the mercury is lost with the solid tailings; 31.6% of the mercury is associated with fine particles in suspension and 50.8% is likely dissolved. About 2.68% is trapped at the bottom of the tank and 3.72% is absorbed by the activated carbon. The bottle roll test revealed that mercury dissolution is directly proportional to cyanide concentration. At 10 g/ton of cyanide, approximately 42% of mercury was leached, whereas all gold was solubilized. During this study, miners recognized the risk associated with the cyanidation of mercury-rich tailings, and were aware of how much mercury is discharged to local streams and to the atmosphere. The active participation of miners in this study has led to the strengthening of their knowledge and awareness of mercury contamination, and has enhanced their understanding of the nature of the problem, as well as the weaknesses and strengths of the system they operate. [Copyright &y& Elsevier]

Abstract: Worldwide, the environmental impacts of artisanal and small-scale gold mining (ASGM) are extensive. Annual losses from mercury, which is used to amalgamate gold, are in the range of 1000 tonnes, and at advanced sites, there is the additional threat of cyanide contamination. Recent developments in The Brazilian Amazon, an area populated by 200,000 small-scale gold miners, have the potential to reduce these impacts considerably. In the locality of Garimpo Ouro Roxo, miners are presently using amalgamation and cyanidation in vat-leaching. Each cycle typically recovers 50% of the gold and lasts 20 days (per tank), consuming around 3300 kg NaCN/month. A new process has been developed and implemented in a pilot plant in this area, involving gravity concentration followed by cyanidation in a ball mill. Concentrate leaching is conducted with a PVC capsule filled with activated carbon inserted in the cyanide solution in the mill. The cycle takes less than 24 h and recovers up to 98% of the gold in the concentrate. The main advantages of wide adoption of this method, apart from a reduced gold recovery cycle and improved recovery, include possible phase out of amalgamation altogether, and marked reductions in cyanide consumption (from current 22,000 kg–980 kg annually). [ABSTRACT FROM AUTHOR]

Abstract: Artisanal small-scale gold miners (ASM) occasionally employ whole ore amalgamation by adding mercury into ball mills to recover gold. In this process, 25–30% of the mercury added is lost to the environment. It is also inefficient less than 30% of gold is recovered. Amalgamation, followed by cyanidation, has been observed at many artisanal mining sites. This combination poses additional environmental and health consequences. Tests with ore samples from Talawaan, North Sulawesi, Indonesia indicate the possibility of replacing mercury by cyanidation in the ball mill, reaching gold extraction of 93% in 6h of leaching. The gold in the Indonesian ore sample is fine and less than 8% of gold recovery was obtained with gravity concentration of the ore ground 80% below 0.25mm, which is a reasonably fine grain size for artisanal gold operations. Replacing mercury addition with cyanidation in ball mills was implemented in one artisanal gold mining operation in Portovelo, Ecuador, achieving 95% of gold extraction in 8h of mill leaching. This technique demonstrated a drastic improvement in gold recovery. It was found to be a simple, inexpensive technique well accepted by local miners. The results from laboratory and field tests are promising; however a thorough investigation into the socio-economic and environmental aspects of this presented alternative must be conducted prior to introduction. [Copyright &y& Elsevier]

• Modified Hardgrove test to predict the Bond Ball Mill Work Index (BBMWI). • Predicts the BBMWI using 30 cm3 (∼40 to 60 g) of −3.35 + 0.600 mm samples. • Simpler execution, quick turn-around time, requiring less operator training. • The proposed test predicts the BBMWI with less than 4% prediction error. • A low cost option to geometallurgical studies and other which few mass is available. Grinding ores in conventional ball mills demands high energy consumption, resulting in relatively high operating costs in a typical mineral processing industrial plant. Whether in the initial stages of a mining project or during its operation, conducting tests to determine the processing circuit's energy consumption throughout the life of mine is necessary in order to reduce such high operating costs. Traditional tests used to determine the energy consumption in grinding, like the Bond Ball Mill test, are relatively time-consuming and require significant amounts of sample, e.g., 8–10 kg, which is not always available in the initial stages of a mineral project or geometallurgical studies. Several authors have developed simplified tests to predict ball mill's energy consumption, typically using the Bond Ball Mill Work Index (BBMWI) as a reference. One option requiring less mass is the Hardgrove mill, traditionally used in the laboratory to determine the energy required to grind coal in roller mills. This test requires 50 g of sample, and the result is based on the amount of fines at the end of grinding to a fixed time. The present study used a modified Hardgrove test to predict the BBMWI. This test involves the measurement of the torque, uses a fixed sample volume with different particle feed sizes from the Hardgrove standard, and determines the specific energy related to the percentage of product passing through the closing size screen of the Bond test, defined as the size specific energy. The results indicated that for a set of 13 samples with the 150 µm closing screen, the average error associated with the predicted BBMWI is within ±2.3%. Further results indicate an error of ±3.1% for 20 samples with the 106 µm closing screen. The correlations presented here are proposed to be validated and/or adjusted for different ores and mines. The proposed test is thus suitable for geometallurgical studies and other applications where relatively small samples are available. In addition, this is a low-cost test, has a quick turn-around time, it is simple to conduct and does not require the handling of heavy loads by operators. [ABSTRACT FROM AUTHOR]

Mineralogical controls on waste-rock weathering rates are important for mine water quality predictions, as the reactivity of minerals is impacted not only by its chemical composition, but also by its texture, arrangement, and association. In this study, seven-year on-site field barrel kinetic tests were conducted with different types of waste rock from the Antamina mine, Peru. Quantitative automated mineralogy was applied to characterize mineral texture, liberation, and association during weathering and used to examine mobilization and attenuation mechanisms. The weathering of reactive intrusive waste rock with low neutralization potential led to mobilization of Cu, Fe, and Zn, and was associated with >75% liberated Fe-, Cu-, or Zn-bearing sulfide minerals and galvanic coupling of pyrite with chalcopyrite and sphalerite. In contrast, the mobilization of Cu, Fe, and Zn was less effective in skarn waste rock types with high neutralization potential, where <70% Cu-, Fe-, and Zn-bearing sulfide minerals were liberated and passivation of pyrite surfaces occurred. Finally, waste rock weathering and drainage quality trends were simulated using a reactive transport model, and calibration of sulfide dissolution rates quantitatively affirmed the observed changes in mineralogical waste rock associations and liberation. This study thus demonstrates that accounting for mineralogical parameters using automated mineralogy may improve practical predictive models for mine waste water management. Image 1 • Integrated mineralogical and geochemical analyzes from a long-term kinetic field barrel monitoring program. • Characterization of waste rock reactivity using quantitative automated mineralogy and drainage quality data. • Reactive transport modeling of geochemical and mineralogical controls on long-term drainage composition. • Drainage chemistry is affected by waste rock mineral arrangements in addition to bulk geochemical composition. [ABSTRACT FROM AUTHOR]

Thickened tailings deposition technology can form a stack with a certain slope by depositing high-concentration tailings slurries to reduce the footprint of tailings storage facilities and water consumption. Thickened tailings slurries exhibit complex non-Newtonian behaviors. Predicting the beach profile evolution of thickened tailings is important for the tailings storage facility design and management. A novel governing differential equation (GDE) derived from the lubrication theory is proposed in this work to capture laws of beach profile formation. Experimental data from three-dimensional laboratory-scale flume tests are analyzed using the proposed GDE. The GDE avoids the discrepancy from an inappropriate coordinate system, which exists in some state-of-the-art models and exhibits higher accuracy when predicting the beach shape near the toe of a preexisted layer. Compared with the Herschel–Bulkley (H–B) model, the Zhang's equilibrium rheological model is preferred to determine the static yield stress, which leads to the accurate estimation of the stack profile in single- and multilayer thickened tailings depositions. The in-situ beach profile of thickened tailings is predicted using a numerical technique. A case study is included to demonstrate that the prediction based on the proposed GDE is consistent with the field measurement. The beach profile prediction of thickened tailings considering thixotropy is also discussed in this study. Results indicated that the decrease of yield stress along the flow path due to thixotropy leads to the concave beach shape of thickened tailings. • The governing differentiating equation to predict beach profile is proposed. • A modified method to predicting the field beach profile is established. • Thixotropy causes the concave beach shape for thickened tailings deposition. [ABSTRACT FROM AUTHOR]

• A small-scale locked-cycle piston press test to provide design information closed-circuit HPGR. • The test ware inspired by the Bond ball mill grindability test. • Piston Work Index describes the samples' resistance to HPGR comminution. • The test results were within ± 20% range of HPGR tests for a fine feed. The increased energy efficiency of HPGR-based circuits as an alternative to AG/SAG mill circuits has been well established. However, assessing the HPGR technology involves pilot-scale testing requiring large samples, which is expensive and may be prohibitive, particularly for early-stage projects. As a result, the uptake of HPGR technology has been slow, emphasizing the need for small-scale tests for sizing and selection. A reliable small-scale test for preliminary HPGR circuit design is essential in garnering the mining industry's interest in the broader adoption of HPGRs. Inspired by the Bond ball mill grindability test, a small-scale locked-cycle piston press test was developed to estimate the circulating load and circuit-specific energy consumption for closed-circuit HPGR operation. The test introduces the Piston Work Index, which describes the ore samples' resistance to HPGR comminution and can be subsequently used to estimate the HPGR circuit-specific energy consumption. The test results indicated that the circuit-specific energy and circulating load obtained from the small-scale piston press test were within the ± 20% range of the locked-cycle pilot scale HPGR tests for a fine feed representing quaternary stage HPGR application. [ABSTRACT FROM AUTHOR]

• A image-based method is proposed to estimate the 3D Wadell roundness of particle. • An alternative strategy to estimate roundness from other shape descriptors is tried. • The image-based roundness estimation method is suitable for various shapes. Wadell roundness is a general particle shape descriptor used in many fields, such as mining engineering, civil engineering, and geotechnical engineering. Initially, Wadell roundness was defined as two-dimensional, and now it has been generalized to three-dimensional. This study proposes a novel image-based method using topographic analysis to estimate the three-dimensional Wadell roundness of irregular particles. And an alternative strategy to estimate 3D Wadell roundness from other shape descriptors is further proposed. The effect of mesh density on 3D Wadell roundness is quantitatively analyzed. In addition, the relationships between 3D Wadell roundness and eleven shape descriptors, including 2D Wadell roundness and the other ten 1D, 2D, and 3D shape descriptors, are discussed. Finally, the computation time of the 3D Wadell roundness estimation algorithm proposed in this study is recorded to evaluate the algorithm's efficiency. The results show that the 3D Wadell roundness estimation algorithm is robust and can be used for idealized geometries and realistic particles of various shapes. The mesh density of particles significantly influences the 3D Wadell roundness. It proved difficult to predict the 3D Wadell roundness from the eleven shape descriptors mentioned in this study. The 3D Wadell roundness estimation algorithm can be finished in a few minutes, potentially using the algorithm in rock shape analysis and mechanics responses investigation. [ABSTRACT FROM AUTHOR]

Abstract Strain rate has drawn great research attention in the area of material mechanics. However, thus far the effects of strain rate on the breakage characteristics of rocks or mineral particles were seldom studied. The applied strain rate is one of the key factors causing the variation in breakage environment, and hence the understanding of strain rate's effect on particle breakage is important to the development of a generic breakage model that isolates the rock properties from the breakage environment. This study systematically investigated the characteristics of single particle breakage at different strain rates. The rock samples from four narrow size fractions were used for carrying out impact and compression tests at variable energy input levels. The energy-size reduction relationships for impact and compression breakage were developed, respectively, and the appearance functions for these two breakage mechanisms were also developed based on previous and current work. The results suggest that the sample breaks easier at lower strain rates and the significance of the particle size effect strongly depends on the strain rate. It is demonstrated that the strain rate has an important influence on the progeny size distribution, but the significance of this influence reduces as the energy input increases. It is also found that the sample breaks with a higher energy efficiency at lower strain rates. The strain rate may affect the initiation and propagation of the cracks originate from small flaws and hence results in the difference in the breakage characteristics. Graphical abstract Unlabelled Image Highlights • The sampled ore breaks easier and more energy efficiently at low strain rates • The significance of particle size effect strongly depends on strain rate • Strain rate has a considerable influence on the progeny size distribution • Strain rate is likely to affect the propagation of cracks from small flaws [ABSTRACT FROM AUTHOR]

XRF bulk sorting is put forward as a credible intender for pre-concentration methods in mining. This paper presents a preliminary study employing a bench-scale approach to calibrate XRF surface sensing to a target concentration of interest related to its volume so as to assess the feasibility of a case barren copper ore “slots” to bulk sorting. Firstly, various top sizes, along with different operators and specimens’ weight/volumes, were examined to quantify the minimum readings needed (MRN) for XRF spot scanning at this scale. Multiple linear regression with a correlation coefficient of 0.921 was validated to be a reliable algorithm for calibrating XRF surface response to Cu volumetric concentration, owing to its consideration of elemental interacts. With the aid of graphical representations of calibrated data on recovery/grade curves, cut-off grade of 0.23% was chosen to enable 30% mass below the threshold to be discarded as waste and the remainder to go for further processing. [ABSTRACT FROM AUTHOR]

[Display omitted] • Acid surface pretreatment reinforced the flotation separation of ilmenite pre-absorbed by reagents. • Acid surface pretreatment increased distribution densities of main elements on ilmenite surfaces. • Original Fe and new Ti sites appeared on ilmenite surfaces after acid surface pretreatment. • Original Ca and Mg sites were unfound after acid surface pretreatment. Minerals in the unqualified ilmenite concentrate collected by flotation reagents appeared the similar surface hydrophobicity and floatability. In this work, acid surface pretreatment was applied to improve the difference in surface properties of ilmenite and gangue minerals pre-absorbed by reagents. Microflotation experiments showed that after ilmenite and titanaugite were treated with high concentrations of NaOL followed by acid surface pretreatment, their recovery differences increased from around 45% to stable 80% regardless of the collector dosage later. AFM and XPS analyses revealed that acid surface pretreatment strengthened the distribution densities of original Fe and new Ti sites and the strengths chemisorbed NaOL onto ilmenite surfaces, while it dissolved intrinsic Ca and Mg sites on titanaugite surfaces. These changes increased the differences in surface hydrophobicity and NaOL adsorption on ilmenite and titanaugite surfaces, which was certified by contact angle and zeta potential. Compared to conventional separation methods, the best result was obtained after rougher flotation concentrate was treated with acid surface pretreatment and three cleaning flotation stages, producing a concentrate with a TiO 2 grade of 47.68% and a TiO 2 recovery of 26.66%. Taken together, acid surface pretreatment is a potential and novel method to reinforce the separation of ilmenite flotation. [ABSTRACT FROM AUTHOR]

• Nickel recovery increases at higher magnetic field strengths. • Magnetic separation recovers over 90% of the magnetic nickel. • Nickel losses are associated with fine and very fine awaruite. In this work, a research study, focused on the recovery of awaruite, was conducted on a representative sample from the Baptiste deposit to evaluate magnetic separation over a range of magnetic field strengths. The Baptiste deposit is a unique nickel deposit containing awaruite, a high-density ferromagnetic nickel–iron alloy. The evaluation included semi-batch and continuous pilot scale tests, employing wet magnetic drums at two different grind sizes. The samples were characterized using techniques including chemical composition analysis, Davis tube testing, and automated mineral analysis. The results showed promising magnetic nickel recoveries, in the range of 92% to 96%. The development of the Baptiste deposit will benefit from a sound scientific understanding of the process solution. [ABSTRACT FROM AUTHOR]

[Display omitted] • A comparison was made to understand the key factors in co-pyrolysis. • Analyze the effect of co-pyrolysis on the composition of pyrolysis gas and tar. • The optimal experimental conditions for activation modification were determined. • Magnetic activated carbon exhibits better adsorption and magnetic properties. Activated carbon plays an important role in the field of wastewater treatment due to its excellent adsorption, but improving the recovery and utilization efficiency of activated carbon is a major challenge for its application. In this study, lignite (LC) and poplar leaves (PL) were used as raw materials to prepare magnetic activated carbon (MAC) by co-pyrolysis and char activation modification. The adsorption performance of the product was studied. The results showed that with different blending ratios of LC and PL, a large amount of alkali metal oxides contained in PL had different promoting effects on the pyrolysis of LC. When the mass ratio of LC to PL in the mixture was 3:2, the experimental value of hydrocarbons in the obtained tar reached 53.00%, which was 7.20% higher than the calculated value. The optimal preparation conditions of MAC were determined. Under the conditions of activation temperature of 700 °C, activation time of 2 h, ZnCl 2 mass fraction of 30%, impregnation liquid–solid ratio of 3:1 and impregnation time of 16 h, the activated carbon exhibits a relatively desirable performance. The obtained products were characterized by VSM, XRD, FT-IR, N 2 adsorption and SEM. As a result, the obtained MAC exhibits a better porous structure and higher specific surface area, and Fe 3 O 4 was observed on the surface of the MAC. The adsorption performance of coking wastewater by MAC was studied. We demonstrate that the prepared MAC could effectively adsorb organic matter in wastewater. After MAC was used to adsorb the coking wastewater for 3 h, the COD concentration in the wastewater decreased from 280 to 60 mg/L, and the MAC could be effectively recovered by magnets after adsorption. [ABSTRACT FROM AUTHOR]

• Awaruite has unique characteristics compared to other nickel minerals. • Awaruite has higher magnetic susceptibility than magnetite. • Magnetic and gravity separation are feasible methods of awaruite concentration. Nickel is an important component of stainless steel and a wide range of applications which are critical for the transition to clean energies including electric vehicle batteries. Awaruite is a native nickel–iron alloy that has gained interest as a possible new economic source of nickel. In the last decades, there have been discoveries of awaruite, mostly with more significant amounts of nickel sulphides, that have demonstrated the potential for awaruite to contribute to the economics of a deposit. This study is focused on the very large Baptiste deposit in central British Columbia, Canada where awaruite is the primary nickel mineral. Most of published data on awaruite are focused on geology, and important fundamental physiochemical properties have still not been determined. These properties are fundamental for the set-up of a flowsheet that will enable its large-scale processing. The limited information available of this nickel–iron alloy can be complemented with the available information of a synthetic alloy with the same elemental composition. The synthetic awaruite alloy has demonstrated remarkable magnetic properties, and based on those properties, it was named permalloy. In this study, physicochemical properties of native and synthetic awaruite were measured including chemical composition, crystallographic structure, and magnetic properties. The native awaruite composition from the Baptiste deposit averages 77.3 % nickel, 21.0 % iron, 1.1 % cobalt and 0.6 % copper. Natural and synthetic awaruite have the same crystallographic characteristics and similar ferromagnetic behaviour. The measured initial volumetric magnetic susceptibility for native awaruite was 14.4 and the saturation magnetization was 750 kA/m. Awaruite has the potential to be concentrated in a unique and valuable nickel concentrate of distinctive characteristics including its very high nickel content, which lowers both the downstream costs and the carbon intensity. Furthermore, the negligible content of sulphur and penalty trace elements, such as mercury, antimony, and arsenic in a potential awaruite concentrate, minimizes the costs of refining it. The physicochemical data in this study provides information to reliably set up a mineral processing flowsheet, which is discussed in this work. [ABSTRACT FROM AUTHOR]

A new comminution technology that can reduce energy consumption when compared to traditional grinding of rock is presented. The process is based on pulverization driven by transcritical CO 2 cycles, resulting in tensile fracture inside the particle rather than compression from outside. Tensile strength of many rocks is approximately 10 times lower compared to compressive strength offering significant potential for saving energy. In this apparatus, comminution can occur over multiple cycles to enhance rock breakage without extracting and refeeding rock between cycles. The test rig depicts test conditions to capture and to recycle the CO 2. Limestone is utilized as an example material in a lab-scale experimental apparatus. Within the apparatus, the temperature and pressure are raised to supercritical conditions. A rapid release of the CO 2 into a decompression chamber results in an expansion of supercritical CO 2 inside the pores and fractures rock from tension instead of compression. Results show a significant fraction of the limestone is comminuted in three consecutive CO 2 pressure cycles. A majority of the resulting particles exhibit larger fragments from 5 mm to 13.2 mm. 6.2% of the feed material was directly transferred to fine material <300 μm without many intermediate progeny particles. Initial results indicate a larger ratio of the pressure before and after burst, and longer soak times aid pulverization. A single rock is also analyzed, where it is noted that breakage occurs along visible fractures, and this behavior is noted over consecutive cycles. [Display omitted] • Supercritical carbon dioxide migrates into pore structure • Rapid depressurization causes gas expansion and fracture via tensile forces • Generating direct tensile forces offers potential for energy saving • Pressure before and after expansion and soak time influence fracture • Comminution advances with further supercritical CO2 cycles [ABSTRACT FROM AUTHOR]

[Display omitted] • Awaruite passivates in neutral and alkaline media. • Awaruite readily floats in acidic media with xanthate. • Xanthate chemisorbs and oxidizes at the awaruite surface in acidic media. Awaruite is a native nickel–iron alloy (Ni 3 Fe), found in serpentinized ultramafic rocks, that has gained interest as a possible source of nickel. FPX Nickel is advancing a very large awaruite deposit in central British Columbia, Canada, on which this work is based. To date there is limited information available regarding the flotation conditions to selectively concentrate awaruite from gangue minerals in serpentinite ores. The aim of this work was to investigate the floatability of awaruite in different solution conditions with a xanthate collector. Awaruite readily floated in acidic solution with a xanthate collector but not in neutral and alkaline solutions. Voltammograms on awaruite indicated that the alloy shows an active passive transition behaviour in acidic solution and passive behaviour in neutral and alkaline solutions. The passivation layer formed in neutral and alkaline solutions showed to inhibit the interaction between xanthate and awaruite surface. Infrared spectra on awaruite showed the presence of xanthate compounds attached to the surface in acidic condition at potentials higher than the reversible potential of xanthate/dixanthogen. Based on experimental results, it was postulated that xanthate chemisorbs on awaruite and then it oxidizes to form dixanthogen. Also, it was demonstrated that when passivated, awaruite quickly activates in acidic solution, good flotation performance was achieved with 10 min of conditioning, and similar performance was obtained after 30 min of conditioning. This work serves as a confirmation that is possible to float awaruite using xanthate, a well-known collector that offers selectivity over oxides and silicate minerals, which are the main gangue minerals in serpentinite ores. [ABSTRACT FROM AUTHOR]

• A novel zone settling velocity function was proposed. • Vesilind function underestimates the settling velocity at high solids concentrations. • The inverse problem by SBSC herein produces an excellent prediction of ZSV at high solids concentrations. • The concentration profile at infinite time was calculated. Relationship between solids zone settling velocity (ZSV) and concentration is of importance in solid-flux theory used in the design and operation of thickeners. A reliable characterization of relationship between ZSV and concentration relying on a single batch settling curve (SBSC) remains necessary and challenging. In this study, a novel ZSV function considering both maximum settling velocity and maximum packing fraction is proposed. The comparison between the novel function and some state-of-the-art ZSV functions indicates that the former shows preferable performances in predicting the batch settling phenomena. The inverse problem to determine ZSV function from SBSC is carried out and the obtained ZSV function performs well in simulating sedimentation without compression. Finally, sedimentation with compression is discussed based on the novel ZSV function. [ABSTRACT FROM AUTHOR]