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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]

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]

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: 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]

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]

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]

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]

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]

The technique of mixing mine waste rock and tailings for disposal has the potential to avoid the problems of acid rock drainage and tailings liquefaction. This paper presents a rational basis for the design of mixtures based on particle packing theory and laboratory investigations. Mixtures were conceptualized using a particle model that allows mixture design and interpretation of behaviour. Laboratory investigations included examination of tailings rheology, mixture trials, and compressibility testing of waste rock, tailings, and mixtures of waste rock and tailings. Results indicate that mixture design governs mixture structure, and consequently also compressibility behaviour. A method is presented to predict mixture compressibility from mixture ratio and the properties of the parent waste rock and tailings. The study provides theory for the design and evaluation of mixtures as a mine waste disposal technique and demonstrates that the design of geotechnical properties is possible for homogeneous mixtures of mine wastes at the laboratory scale. [ABSTRACT FROM AUTHOR]