CE
C.H.J. Elpenhof
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Evaluating the electrochemical properties and behaviour of copper/cobalt minerals
Using Cyclic Voltammetry and Electrochemical Quartz Crystal Microbalance techniques
Mining projects around the world face a significant challenge to reduce their footprint and be more environmentally friendly. Research has shown that mineral processing is of major influence, due to the use of heavy chemicals that are both expensive and polluting. Currently, electrowinning (the electrodeposition of metals) is only used in the last purification step of the process. So far, the majority of the studies on cobalt have focused on non-electrowinning possibilities. Therefore, it is of interest to investigate the electrochemical behaviour within different environments to obtain more information and gain a better understanding. This thesis focuses on the electrochemical behaviour and deposition of cobalt-bearing minerals, which will be evaluated with the help of cyclic voltammetry (CV) and the electrochemical quartz crystal microbalance (EQCM). These techniques use the help of multiple variable input parameters, which will be investigated and compared to gain the optimised condition to perform the experiments. Furthermore, the sensitivity of the techniques to different input parameters and different solutions will be investigated. This is done to investigate what the origins are for the differences in the electrochemical behaviour of copper-cobalt minerals in aqueous solutions using analytical, synthetic and real ores, and to find a correlation between the obtained results using the graphs generated using CV and EQCM-techniques. This is done to investigate to possibilities using selective electrowinning, meaning the electrodeposition of multiple elements within the same electrolyte solution. Based on a review of the literature, the experimental setup used for the experiments will be discussed to gain better understanding of the specialised equipment and corresponding software. Cobalt chloride, cobalt sulphate and copper sulfate solution will be evaluated first, after which two synthetic cobalt-bearing minerals containing iron will be tested. With the help of CV, the electrochemical behaviour, e.g. redox- reactions, can be analysed. Using the EQCM, accurate measurements of the mass change per unit area of the electroplated cobalt will be recorded. Synthetic minerals will be used to discover how much can be recovered using this technique. Finally, six samples from the Democratic Republic of Congo (DRC) will be evaluated to obtain the same data as for the synthetic minerals. For this QEMSCAN data is used to evaluate the mineral composition. Analysis of the results demonstrated that under different circumstances in different environments, similar electrochemical behaviour and the occurrence of copper, iron and/or cobalt deposition is observed. However, for special cases these reactions do not occur. This difference can be explained by a varying mineralogy, where bornite and chalcopyrite have a positive effect on the electrochemical activity. Regarding the shape of the voltammogram, the number of electrons involved in the reaction has the largest influence. Furthermore, alkaline conditions have a positive effect on the electrodeposition of cobalt. No overall correlation has been found between the samples. For all experiments similar reactions and electrochemical activity is observed regarding the peak potentials and within the same environment, correlations can be found. Recommendations for further research are to investigate the influence of changes to parameters such as temperature, magnetic field and impurities on the electrochemical behaviour of the reaction and changes in the yield of electrodeposited material, to generate more data to validate and calibrate the characteristic potentials that can be used for selective electrowinning and to gather more data of the selective electrowinning experiments in terms of additional (rare) elements, such as lithium.
...
Mining projects around the world face a significant challenge to reduce their footprint and be more environmentally friendly. Research has shown that mineral processing is of major influence, due to the use of heavy chemicals that are both expensive and polluting. Currently, electrowinning (the electrodeposition of metals) is only used in the last purification step of the process. So far, the majority of the studies on cobalt have focused on non-electrowinning possibilities. Therefore, it is of interest to investigate the electrochemical behaviour within different environments to obtain more information and gain a better understanding. This thesis focuses on the electrochemical behaviour and deposition of cobalt-bearing minerals, which will be evaluated with the help of cyclic voltammetry (CV) and the electrochemical quartz crystal microbalance (EQCM). These techniques use the help of multiple variable input parameters, which will be investigated and compared to gain the optimised condition to perform the experiments. Furthermore, the sensitivity of the techniques to different input parameters and different solutions will be investigated. This is done to investigate what the origins are for the differences in the electrochemical behaviour of copper-cobalt minerals in aqueous solutions using analytical, synthetic and real ores, and to find a correlation between the obtained results using the graphs generated using CV and EQCM-techniques. This is done to investigate to possibilities using selective electrowinning, meaning the electrodeposition of multiple elements within the same electrolyte solution. Based on a review of the literature, the experimental setup used for the experiments will be discussed to gain better understanding of the specialised equipment and corresponding software. Cobalt chloride, cobalt sulphate and copper sulfate solution will be evaluated first, after which two synthetic cobalt-bearing minerals containing iron will be tested. With the help of CV, the electrochemical behaviour, e.g. redox- reactions, can be analysed. Using the EQCM, accurate measurements of the mass change per unit area of the electroplated cobalt will be recorded. Synthetic minerals will be used to discover how much can be recovered using this technique. Finally, six samples from the Democratic Republic of Congo (DRC) will be evaluated to obtain the same data as for the synthetic minerals. For this QEMSCAN data is used to evaluate the mineral composition. Analysis of the results demonstrated that under different circumstances in different environments, similar electrochemical behaviour and the occurrence of copper, iron and/or cobalt deposition is observed. However, for special cases these reactions do not occur. This difference can be explained by a varying mineralogy, where bornite and chalcopyrite have a positive effect on the electrochemical activity. Regarding the shape of the voltammogram, the number of electrons involved in the reaction has the largest influence. Furthermore, alkaline conditions have a positive effect on the electrodeposition of cobalt. No overall correlation has been found between the samples. For all experiments similar reactions and electrochemical activity is observed regarding the peak potentials and within the same environment, correlations can be found. Recommendations for further research are to investigate the influence of changes to parameters such as temperature, magnetic field and impurities on the electrochemical behaviour of the reaction and changes in the yield of electrodeposited material, to generate more data to validate and calibrate the characteristic potentials that can be used for selective electrowinning and to gather more data of the selective electrowinning experiments in terms of additional (rare) elements, such as lithium.
In the mining industry, sampling is an essential feature for the characterization of the material when all available material cannot be examined and only a small fraction of the total is evaluated. This study addresses how the minimum number of samples required to obtain a statistically accurate answer. This is important since less sample measurement save time and money. The sample size is related to the homo- and heterogeneity of a rock sample, where the sample size of a homogeneous material is smaller than a heterogeneous material. Many types of research is carried out on the sampling theory, but it is hard to create a formula to determine the sample size beforehand based on a rate of heterogeneity. The homogeneity percentage is not linked to the sample size, but with a spatial elemental distribution, this can be possible. However, further research is needed in order to answer the question more exact for a situation that is more complex. This study first mentions several definitions of homogeneity, second their origin within geology is evaluated. Last this is calculated with theoretical models to explore the minimum sample size required. The project evaluates how the sample size changes when homogeneity, heterogeneity and spatial distribution of the grade varies within a rock image. It is done with the help of an image analysis tool which creates a homogeneity curve, the mean and standard deviations for an increasing sample size. The standard deviations are used to generate answer within different levels of confidence for certain margins of error.
Also, the variogram is used to determine the spatial correlation of the sample and interpolation is made using a general kriging method. Multiple images are evaluated with different rates of homogeneity, the number of elements and their spatial distribution. This study proofs generating more samples increases the accuracy of the characterization. With a lower target grade, the sample size will increase and also with an increasing image or grid size the number of samples will decrease. The variogram gives a first impression of the homogeneity since a smaller range and sill indicates more homogeneous material. ...
Also, the variogram is used to determine the spatial correlation of the sample and interpolation is made using a general kriging method. Multiple images are evaluated with different rates of homogeneity, the number of elements and their spatial distribution. This study proofs generating more samples increases the accuracy of the characterization. With a lower target grade, the sample size will increase and also with an increasing image or grid size the number of samples will decrease. The variogram gives a first impression of the homogeneity since a smaller range and sill indicates more homogeneous material. ...
In the mining industry, sampling is an essential feature for the characterization of the material when all available material cannot be examined and only a small fraction of the total is evaluated. This study addresses how the minimum number of samples required to obtain a statistically accurate answer. This is important since less sample measurement save time and money. The sample size is related to the homo- and heterogeneity of a rock sample, where the sample size of a homogeneous material is smaller than a heterogeneous material. Many types of research is carried out on the sampling theory, but it is hard to create a formula to determine the sample size beforehand based on a rate of heterogeneity. The homogeneity percentage is not linked to the sample size, but with a spatial elemental distribution, this can be possible. However, further research is needed in order to answer the question more exact for a situation that is more complex. This study first mentions several definitions of homogeneity, second their origin within geology is evaluated. Last this is calculated with theoretical models to explore the minimum sample size required. The project evaluates how the sample size changes when homogeneity, heterogeneity and spatial distribution of the grade varies within a rock image. It is done with the help of an image analysis tool which creates a homogeneity curve, the mean and standard deviations for an increasing sample size. The standard deviations are used to generate answer within different levels of confidence for certain margins of error.
Also, the variogram is used to determine the spatial correlation of the sample and interpolation is made using a general kriging method. Multiple images are evaluated with different rates of homogeneity, the number of elements and their spatial distribution. This study proofs generating more samples increases the accuracy of the characterization. With a lower target grade, the sample size will increase and also with an increasing image or grid size the number of samples will decrease. The variogram gives a first impression of the homogeneity since a smaller range and sill indicates more homogeneous material.
Also, the variogram is used to determine the spatial correlation of the sample and interpolation is made using a general kriging method. Multiple images are evaluated with different rates of homogeneity, the number of elements and their spatial distribution. This study proofs generating more samples increases the accuracy of the characterization. With a lower target grade, the sample size will increase and also with an increasing image or grid size the number of samples will decrease. The variogram gives a first impression of the homogeneity since a smaller range and sill indicates more homogeneous material.
Applying wind turbines to create renewable energy is used by many companies around the world. However, in the mining industry, only two projects use wind energy. In the mining industry, energy consumption can be up to twenty-five megawatts per tonne of produced material. The main reason is the use of fossil fuel for generators in off-grid situations.
This paper evaluates the benefits of wind power for mining operations and the benefits of the Delft Offshore Turbine (DOT) type wind turbine compared to other turbines. Using the DOT type wind turbine, wind energy can be used for three different applications, namely: 1) generation of electricity, 2) direct hydraulic power and 3) direct dewatering.
Different areas in the world are then analysed on the aspects: 1) soil strength, 2) elevation or relief of the terrain and 3) the wind velocities. A case study is performed for the most suitable area in the world: Australia. Next the best-chosen location is divided into smaller regions, where the same evaluation is applied. A case study was conducted on a favourable area, calculating various cost and CO2 reduction scenarios based on simulated wind speeds.
The DOT type turbine can provide electricity, which costs 23 to 44 US$/MWh. Compared to a 1-MW diesel generator, in the best-case scenario, a wind farm generating 25 MW per hour, can save $4200/hour. Overall, implementing the DOT at the right location, can 1) remove polluting diesel generators from mining operations, 2) save energy costs up to $4200/hour and 3) reduce CO2 emissions up to 770 kilograms per MW per hour. ...
This paper evaluates the benefits of wind power for mining operations and the benefits of the Delft Offshore Turbine (DOT) type wind turbine compared to other turbines. Using the DOT type wind turbine, wind energy can be used for three different applications, namely: 1) generation of electricity, 2) direct hydraulic power and 3) direct dewatering.
Different areas in the world are then analysed on the aspects: 1) soil strength, 2) elevation or relief of the terrain and 3) the wind velocities. A case study is performed for the most suitable area in the world: Australia. Next the best-chosen location is divided into smaller regions, where the same evaluation is applied. A case study was conducted on a favourable area, calculating various cost and CO2 reduction scenarios based on simulated wind speeds.
The DOT type turbine can provide electricity, which costs 23 to 44 US$/MWh. Compared to a 1-MW diesel generator, in the best-case scenario, a wind farm generating 25 MW per hour, can save $4200/hour. Overall, implementing the DOT at the right location, can 1) remove polluting diesel generators from mining operations, 2) save energy costs up to $4200/hour and 3) reduce CO2 emissions up to 770 kilograms per MW per hour. ...
Applying wind turbines to create renewable energy is used by many companies around the world. However, in the mining industry, only two projects use wind energy. In the mining industry, energy consumption can be up to twenty-five megawatts per tonne of produced material. The main reason is the use of fossil fuel for generators in off-grid situations.
This paper evaluates the benefits of wind power for mining operations and the benefits of the Delft Offshore Turbine (DOT) type wind turbine compared to other turbines. Using the DOT type wind turbine, wind energy can be used for three different applications, namely: 1) generation of electricity, 2) direct hydraulic power and 3) direct dewatering.
Different areas in the world are then analysed on the aspects: 1) soil strength, 2) elevation or relief of the terrain and 3) the wind velocities. A case study is performed for the most suitable area in the world: Australia. Next the best-chosen location is divided into smaller regions, where the same evaluation is applied. A case study was conducted on a favourable area, calculating various cost and CO2 reduction scenarios based on simulated wind speeds.
The DOT type turbine can provide electricity, which costs 23 to 44 US$/MWh. Compared to a 1-MW diesel generator, in the best-case scenario, a wind farm generating 25 MW per hour, can save $4200/hour. Overall, implementing the DOT at the right location, can 1) remove polluting diesel generators from mining operations, 2) save energy costs up to $4200/hour and 3) reduce CO2 emissions up to 770 kilograms per MW per hour.
This paper evaluates the benefits of wind power for mining operations and the benefits of the Delft Offshore Turbine (DOT) type wind turbine compared to other turbines. Using the DOT type wind turbine, wind energy can be used for three different applications, namely: 1) generation of electricity, 2) direct hydraulic power and 3) direct dewatering.
Different areas in the world are then analysed on the aspects: 1) soil strength, 2) elevation or relief of the terrain and 3) the wind velocities. A case study is performed for the most suitable area in the world: Australia. Next the best-chosen location is divided into smaller regions, where the same evaluation is applied. A case study was conducted on a favourable area, calculating various cost and CO2 reduction scenarios based on simulated wind speeds.
The DOT type turbine can provide electricity, which costs 23 to 44 US$/MWh. Compared to a 1-MW diesel generator, in the best-case scenario, a wind farm generating 25 MW per hour, can save $4200/hour. Overall, implementing the DOT at the right location, can 1) remove polluting diesel generators from mining operations, 2) save energy costs up to $4200/hour and 3) reduce CO2 emissions up to 770 kilograms per MW per hour.