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David A. Beattie - One of the best experts on this subject based on the ideXlab platform.
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sericite chalcocite mineral particle interactions and hetero aggregation sliming mechanism in aqueous media
Chemical Engineering Science, 2009Co-Authors: Jonas Addaimensah, David A. BeattieAbstract:Abstract Attractive particle interactions which lead to hetero-aggregation or “sliming” of gangue and valuable mineral particles are encountered in a number of hydrometallurgical and flotation processes. Sliming leads to poor recovery of the valuable, hydrophobic minerals and high recovery of hydrophilic gangue particles in flotation concentrates. In the present work, the influence of interfacial chemistry and dispersion conditions on particle interactions which underpin the mechanism of hetero-aggregation between sericite and chalcocite particles was investigated in the pH range 5–9 at 23 °C. Hetero-aggregation is shown to occur under aqueous dispersion conditions where the fluid Shear rate was high and the individual chalcocite and sericite particles were negatively charged, as shown by the electrokinetic potential data. Continuous flow particulate adsorption and rheological studies revealed that the hetero-aggregation behaviour was strongly pH and oxidative environment dependant. Sliming was greater at lower than higher pH and under air saturation than N 2 gas purge. The unexpected hetero-aggregation is ascribed to chalcocite (Cu(I) 2 S) surface oxidation and dissolution which accentuated with decreasing pH and Cu (II) ion hydrolysis effect. Specific adsorption of Cu (II) complexes onto the mix minerals’ surfaces had a striking impact on the interfacial chemistry, reflecting significantly enhanced dispersion Shear Yield Stress. The attractive particles’ interactions are believed to be due to a combination of Cu(II)-mediated mechanisms including: electrostatic-charge patch attraction, van der Waals attraction, adsorbed ion–particle bridging, surface nucleation and cementation. Sliming mitigation was demonstrated by the use of N 2 gas and higher pH, as evidenced by markedly lower sericite–chalcocite dispersion Shear Yield Stress and greatly reduced particulate adsorption behaviour.
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Sericite–chalcocite mineral particle interactions and hetero-aggregation (sliming) mechanism in aqueous media
Chemical Engineering Science, 2009Co-Authors: Jonas Addai-mensah, David A. BeattieAbstract:Abstract Attractive particle interactions which lead to hetero-aggregation or “sliming” of gangue and valuable mineral particles are encountered in a number of hydrometallurgical and flotation processes. Sliming leads to poor recovery of the valuable, hydrophobic minerals and high recovery of hydrophilic gangue particles in flotation concentrates. In the present work, the influence of interfacial chemistry and dispersion conditions on particle interactions which underpin the mechanism of hetero-aggregation between sericite and chalcocite particles was investigated in the pH range 5–9 at 23 °C. Hetero-aggregation is shown to occur under aqueous dispersion conditions where the fluid Shear rate was high and the individual chalcocite and sericite particles were negatively charged, as shown by the electrokinetic potential data. Continuous flow particulate adsorption and rheological studies revealed that the hetero-aggregation behaviour was strongly pH and oxidative environment dependant. Sliming was greater at lower than higher pH and under air saturation than N 2 gas purge. The unexpected hetero-aggregation is ascribed to chalcocite (Cu(I) 2 S) surface oxidation and dissolution which accentuated with decreasing pH and Cu (II) ion hydrolysis effect. Specific adsorption of Cu (II) complexes onto the mix minerals’ surfaces had a striking impact on the interfacial chemistry, reflecting significantly enhanced dispersion Shear Yield Stress. The attractive particles’ interactions are believed to be due to a combination of Cu(II)-mediated mechanisms including: electrostatic-charge patch attraction, van der Waals attraction, adsorbed ion–particle bridging, surface nucleation and cementation. Sliming mitigation was demonstrated by the use of N 2 gas and higher pH, as evidenced by markedly lower sericite–chalcocite dispersion Shear Yield Stress and greatly reduced particulate adsorption behaviour.
Shizhu Wen - One of the best experts on this subject based on the ideXlab platform.
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Structure factor of electrorheological fluids in compressive flow
Smart Materials and Structures, 2010Co-Authors: Yu Tian, Yonggang Meng, Xuli Zhu, Jile Jiang, Shizhu WenAbstract:This paper examines the chain structure factor evolution of electrorheological (ER) fluids in compressive flow. The Yield strength of ER fluids was modeled based on a single pair electrostatic interaction between particles and the structure factor, which includes all the effects except the single pair electrostatic interaction between particles presented by the local electric field strength between particles. Both the mechanical and electrical properties of ER fluids in compressive flow have been experimentally determined. The nominal Shear Yield Stress of the ER fluid in compressive flow was derived by assuming that it was a transformed Shear flow of a Bingham fluid. The single pair particle interaction strength is related to the measured electric current, which reflects the local electric field strength between particles. The structure factor evolution in compressive flow was derived by comparing the nominal Shear Yield Stress and the single pair particle interaction strength. As expected, the calculated structure factor increased significantly using this method, much higher than that described by the many-body effect and the difference of dipole–dipole interaction and multi-dipole interaction between particles. Direct mechanical contacts and frictional forces between particles are thought to contribute significantly to the high structure factor and nominal Shear Yield Stress of the ER fluid in compressive flow. This behavior might be similar in magnetorheological (MR) fluids.
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Electrorheological fluid under elongation, compression, and Shearing.
Physical review. E Statistical nonlinear and soft matter physics, 2002Co-Authors: Y Tian, Y Meng, H Mao, Shizhu WenAbstract:Electrorheological (ER) fluid based on zeolite and silicone oil under elongation, compression, and Shearing was investigated at room temperature. Dc electric fields were applied on the ER fluid when elongation and compression were carried out on a self-constructed test system. The Shear Yield Stress, presenting the macroscopic interactions of particles in the ER fluid along the direction of Shearing and perpendicular to the direction of the electric field, was also obtained by a HAAKE RV20 rheometer. The tensile Yield Stress, presenting the macroscopic interactions of particles in the ER fluid along the direction of the electric field, was achieved as the peak value in the elongating curve with an elongating Yield strain of 0.15-0.20. A Shear Yield angle of about 15 degrees -18.5 degrees reasonably connected tensile Yield Stress with Shear Yield Stress, agreeing with the Shear Yield angle tested well by other researchers. The compressing tests showed that the ER fluid has a high compressive modulus under a small compressive strain lower than 0.1. The compressive Stress has an exponential relationship with the compressive strain when it is higher than 0.1, and it is much higher than Shear Yield Stress.
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Electrorheology of a zeolite/silicone oil suspension under dc fields
Journal of Applied Physics, 2001Co-Authors: Yu Tian, Yonggang Meng, Shizhu WenAbstract:The electrorheology of electrorheological (ER) fluids based on zeolite and silicone oil under dc fields was investigated at room temperature. ER fluids with volume fractions of 27% and 30% were prepared and tested. When a 5 kV/mm dc field was applied, Shear Yield Stress of 26.7 kPa was obtained for the latter. The ER fluid with a higher volume fraction of zeolite had a higher current density and a higher Shear Yield Stress under the same electric field. Compared with other ER fluids based on zeolite particles with low Shear Yield Stress, the zeolite employed by us was found to have high dielectric constant and conductivity. The high permittivity mismatch and the high conductivity mismatch of the components of the fluids were considered responsible for the high Shear Yield Stress.
Yu Tian - One of the best experts on this subject based on the ideXlab platform.
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Structure factor of electrorheological fluids in compressive flow
Smart Materials and Structures, 2010Co-Authors: Yu Tian, Yonggang Meng, Xuli Zhu, Jile Jiang, Shizhu WenAbstract:This paper examines the chain structure factor evolution of electrorheological (ER) fluids in compressive flow. The Yield strength of ER fluids was modeled based on a single pair electrostatic interaction between particles and the structure factor, which includes all the effects except the single pair electrostatic interaction between particles presented by the local electric field strength between particles. Both the mechanical and electrical properties of ER fluids in compressive flow have been experimentally determined. The nominal Shear Yield Stress of the ER fluid in compressive flow was derived by assuming that it was a transformed Shear flow of a Bingham fluid. The single pair particle interaction strength is related to the measured electric current, which reflects the local electric field strength between particles. The structure factor evolution in compressive flow was derived by comparing the nominal Shear Yield Stress and the single pair particle interaction strength. As expected, the calculated structure factor increased significantly using this method, much higher than that described by the many-body effect and the difference of dipole–dipole interaction and multi-dipole interaction between particles. Direct mechanical contacts and frictional forces between particles are thought to contribute significantly to the high structure factor and nominal Shear Yield Stress of the ER fluid in compressive flow. This behavior might be similar in magnetorheological (MR) fluids.
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ER fluid based on zeolite and silicone oil with high strength
Materials Letters, 2001Co-Authors: Yu Tian, Yonggang MengAbstract:An ER fluid based on zeolite and silicone oil with high Shear Yield Stress was reported in this paper. Different from traditional mixing process in preparing ER fluid, a post-oven process technique was introduced in the preparing of ER fluid. After microwave dealing with the mixed fluid, the Shear Yield strength of the ER fluid increased. Testing results showed that Shear Yield Stress of the ER fluid over 20 kPa when 5 kV/mm electric field (dc) was applied had been accessed.
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Electrorheology of a zeolite/silicone oil suspension under dc fields
Journal of Applied Physics, 2001Co-Authors: Yu Tian, Yonggang Meng, Shizhu WenAbstract:The electrorheology of electrorheological (ER) fluids based on zeolite and silicone oil under dc fields was investigated at room temperature. ER fluids with volume fractions of 27% and 30% were prepared and tested. When a 5 kV/mm dc field was applied, Shear Yield Stress of 26.7 kPa was obtained for the latter. The ER fluid with a higher volume fraction of zeolite had a higher current density and a higher Shear Yield Stress under the same electric field. Compared with other ER fluids based on zeolite particles with low Shear Yield Stress, the zeolite employed by us was found to have high dielectric constant and conductivity. The high permittivity mismatch and the high conductivity mismatch of the components of the fluids were considered responsible for the high Shear Yield Stress.
Yonggang Meng - One of the best experts on this subject based on the ideXlab platform.
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Structure factor of electrorheological fluids in compressive flow
Smart Materials and Structures, 2010Co-Authors: Yu Tian, Yonggang Meng, Xuli Zhu, Jile Jiang, Shizhu WenAbstract:This paper examines the chain structure factor evolution of electrorheological (ER) fluids in compressive flow. The Yield strength of ER fluids was modeled based on a single pair electrostatic interaction between particles and the structure factor, which includes all the effects except the single pair electrostatic interaction between particles presented by the local electric field strength between particles. Both the mechanical and electrical properties of ER fluids in compressive flow have been experimentally determined. The nominal Shear Yield Stress of the ER fluid in compressive flow was derived by assuming that it was a transformed Shear flow of a Bingham fluid. The single pair particle interaction strength is related to the measured electric current, which reflects the local electric field strength between particles. The structure factor evolution in compressive flow was derived by comparing the nominal Shear Yield Stress and the single pair particle interaction strength. As expected, the calculated structure factor increased significantly using this method, much higher than that described by the many-body effect and the difference of dipole–dipole interaction and multi-dipole interaction between particles. Direct mechanical contacts and frictional forces between particles are thought to contribute significantly to the high structure factor and nominal Shear Yield Stress of the ER fluid in compressive flow. This behavior might be similar in magnetorheological (MR) fluids.
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ER fluid based on zeolite and silicone oil with high strength
Materials Letters, 2001Co-Authors: Yu Tian, Yonggang MengAbstract:An ER fluid based on zeolite and silicone oil with high Shear Yield Stress was reported in this paper. Different from traditional mixing process in preparing ER fluid, a post-oven process technique was introduced in the preparing of ER fluid. After microwave dealing with the mixed fluid, the Shear Yield strength of the ER fluid increased. Testing results showed that Shear Yield Stress of the ER fluid over 20 kPa when 5 kV/mm electric field (dc) was applied had been accessed.
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Electrorheology of a zeolite/silicone oil suspension under dc fields
Journal of Applied Physics, 2001Co-Authors: Yu Tian, Yonggang Meng, Shizhu WenAbstract:The electrorheology of electrorheological (ER) fluids based on zeolite and silicone oil under dc fields was investigated at room temperature. ER fluids with volume fractions of 27% and 30% were prepared and tested. When a 5 kV/mm dc field was applied, Shear Yield Stress of 26.7 kPa was obtained for the latter. The ER fluid with a higher volume fraction of zeolite had a higher current density and a higher Shear Yield Stress under the same electric field. Compared with other ER fluids based on zeolite particles with low Shear Yield Stress, the zeolite employed by us was found to have high dielectric constant and conductivity. The high permittivity mismatch and the high conductivity mismatch of the components of the fluids were considered responsible for the high Shear Yield Stress.
Peter J Scales - One of the best experts on this subject based on the ideXlab platform.
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variability of Shear Yield Stress measurement and implications for mineral processing
20th International Seminar on Paste and Thickened Tailings 2017 16-18 June Beijing, 2017Co-Authors: A Knight, Peter J Scales, Fiona Sofrà, Anthony D. Stickland, Daniel R. Lester, Richard BuscallAbstract:At high concentrations, mineral tailings exhibit solid-like behavior up to a critical Shear Stress, the Shear Yield Stress , which must be exceeded before flow may occur. The magnitude of has a significant influence upon a wide range of important mineral processing operating parameters, including pipeline pressure gradient, thickener operation and tailings beach slope, for example. Although the concept of a critical Shear Stress is a simple and convenient engineering metric, in practice the transition from solid to fluid-like behavior is much more complicated, resulting in a range of apparent Yield Stress values that vary with the applied Shear conditions. For example, in constant rate or flow start-up rheological testing, the peak Stress (one measure of ) can more than double depending on the applied strain rate. In constant Stress tests, there is a range of Stress over which the slurry exhibits solid behavior over short timescales, but may Yield and flow on much longer timescales. Other methods for Yield Stress determination, such as extrapolation from steady-state Stress versus rate data, the onset of non-linearity in oscillatory flows or slump testing can generate an even broader range of Yield Stress values. Whilst it is neither practical nor desirable to incorporate such complex Yielding behaviour into basic models of engineering operations, it is of paramount importance to use an appropriate measure of Shear Yield Stress for a given application. The time and rate dependencies of the selected measurement method must match the time and rate conditions of the intended application. Failure to do so can introduce significant errors with attendant design, operation and cost implications. The present work takes recent insights into the Shear rheology of minerals tailings and discusses appropriate measurement techniques for a range of processing applications, including beach slope and pipeline pressure drop prediction, as well the implications of using inappropriate measurement techniques. Rheological measurements of a model system are used to demonstrate the variability of the apparent Yield Stress with measurement technique. Comparisons with model values of pipeline pressure drop and beach slope are used to demonstrate the scale-up implications of using inappropriate rheological data.
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Variability of Shear Yield Stress – measurement and implications for mineral processing
Proceedings of the 20th International Seminar on Paste and Thickened Tailings, 2017Co-Authors: A Knight, Peter J Scales, Fiona Sofrà, Anthony D. Stickland, Daniel R. Lester, Richard BuscallAbstract:At high concentrations, mineral tailings exhibit solid-like behavior up to a critical Shear Stress, the Shear Yield Stress , which must be exceeded before flow may occur. The magnitude of has a significant influence upon a wide range of important mineral processing operating parameters, including pipeline pressure gradient, thickener operation and tailings beach slope, for example. Although the concept of a critical Shear Stress is a simple and convenient engineering metric, in practice the transition from solid to fluid-like behavior is much more complicated, resulting in a range of apparent Yield Stress values that vary with the applied Shear conditions. For example, in constant rate or flow start-up rheological testing, the peak Stress (one measure of ) can more than double depending on the applied strain rate. In constant Stress tests, there is a range of Stress over which the slurry exhibits solid behavior over short timescales, but may Yield and flow on much longer timescales. Other methods for Yield Stress determination, such as extrapolation from steady-state Stress versus rate data, the onset of non-linearity in oscillatory flows or slump testing can generate an even broader range of Yield Stress values. Whilst it is neither practical nor desirable to incorporate such complex Yielding behaviour into basic models of engineering operations, it is of paramount importance to use an appropriate measure of Shear Yield Stress for a given application. The time and rate dependencies of the selected measurement method must match the time and rate conditions of the intended application. Failure to do so can introduce significant errors with attendant design, operation and cost implications. The present work takes recent insights into the Shear rheology of minerals tailings and discusses appropriate measurement techniques for a range of processing applications, including beach slope and pipeline pressure drop prediction, as well the implications of using inappropriate measurement techniques. Rheological measurements of a model system are used to demonstrate the variability of the apparent Yield Stress with measurement technique. Comparisons with model values of pipeline pressure drop and beach slope are used to demonstrate the scale-up implications of using inappropriate rheological data.
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The Influence of Surface Chemistry on the Rheology and Flow of Flocculated Particulate Suspensions
Mineral Processing and Extractive Metallurgy Review, 2000Co-Authors: Peter J Scales, Stephen B Johnson, P C KapurAbstract:The role of the surface chemistry of particles in controlling the rheology of flocculated particulate suspensions is discussed. The case is developed for the measurement of the Shear Yield Stress of a suspension of alumina particles and a theoretical interpretation of the Yield Stress is presented which is able to describe the effect of particle size distribution, solid loading, pH and hence, electrokinetics of the suspension. Scaling of the data to the maximum Yield Stress at a given volume fraction provides a means of removing particle size and volume fraction related effects and gives information as to the mode of failure in Yielding of suspensions and the mode of action of molecular additives.
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the binding of monovalent electrolyte ions on α alumina ii the Shear Yield Stress of concentrated suspensions
Langmuir, 1999Co-Authors: Stephen B Johnson, Peter J Scales, George V Franks, Thomas W HealyAbstract:The Shear Yield Stress properties of α-alumina suspensions have been investigated as a function of pH and different monovalent electrolyte types and concentrations. The results have then been compared with complementary electrokinetic studies of α-alumina under analogous suspension conditions. Over the entire pH range at an electrolyte concentration of 1.0 mol dm -3 , the Shear Yield Stress is shown to decrease in the sequence Li + > Na + > K + > Cs + , showing that the strength of the interparticle network decreases in the same order. In addition, use of the Shear Yield Stress model of Scales et al. 1 indicates that the interparticle separation in the presence of these species decreases in the sequence Cs + > K + > Na + > Li + . These findings are consistent with the water structure making-structure breaking model of Gierst et al. 2 and Berube and de Bruyn, 3 which predicts that an entropic attraction will exist between ions and surfaces that promote similar ordering effects in their local aqueous environments. By contrast, almost identical Shear Yield Stress versus pH results are obtained in the presence of Br - , Cl - , I - , and NO 3 - over the entire range of electrolyte concentrations investigated. The interparticle separation is similarly found to be the same in those cases. These results cannot be predicted using the water structure making-structure breaking model, and do not allow the mechanism of anion-surface association to be conclusively resolved.
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the electrokinetic and Shear Yield Stress properties of kaolinite in the presence of aluminium ions
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 1999Co-Authors: Stephen B Johnson, David R Dixon, Peter J ScalesAbstract:Abstract The electroacoustic ζ potential and Shear Yield Stress ( τ y ) properties of kaolinite suspensions have been examined over a wide range of pH conditions and Al(III) concentrations. At zero or low Al(III) concentrations, the ζ potential data are dominated by the silica-like kaolinite face, while the corresponding τ y data show the characteristics of pH-dependent face and edge interactions. As the Al(III) concentration is raised, all ζ potential data become increasingly more positive, the electrokinetic isoelectric point progressively shifts to higher pH, and the τ y versus pH data change systematically from kaolinite-like to alumina-like behaviour. These findings are indicative of the adsorption of Al(III)-based hydrolysis products, as is predicted by the adsorption model of James and Healy, J. Colloid Interface Sci., 40 (1972) 65. A comparison of the properties of partially Al(III)-coated kaolinite particles in the presence of Cl − and SO 4 2− shows that the ζ potential results are more negative and the Shear Yield Stress data are lower for the kaolinite–Al(III)–SO 4 2− system. These results can be rationalised in terms of the extent of surface coverage by Al(III) hydrolysis products and anion adsorption on the surface-adsorbed Al(III)-based precipitates.