Linda Botha - Academia.edu (original) (raw)
Papers by Linda Botha
The Canadian Journal of Chemical Engineering, 2018
† This article has been accepted for publication and undergone full peer review but has not been ... more † This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process, which may lead to differences between this version and the Version of Record. Please cite this article as
Chemosphere, 2018
Polymer-driven flocculation and dewatering of mature fine tailings (MFT) is critical to improve t... more Polymer-driven flocculation and dewatering of mature fine tailings (MFT) is critical to improve their consolidation. MFT flocculation and dewatering depends on the size of the suspended clay particles, and on the composition and properties of the liquid in which they are dispersed. The effect of water chemistry on the polymer-particle dynamics is nontrivial, particularly for non-spherical, polydisperse particles such as natural clays. In this study, we used a response surface methodology to systematically assess the impact of Na and Ca concentration and anionic polyacrylamide dosage in the flocculation and dewatering of MFT. We observed a beneficial synergistic effect between Ca concentration and polyacrylamide dosage, although excess of Ca may reduce polyacrylamide activity. In addition, we investigated the impact of clay particle size on MFT flocculation. Polyacrylamide did not flocculate MFT fractions where the fine clay particles (<2 μm) represented most of the population. Go...
The Canadian Journal of Chemical Engineering, 2015
It is hard to treat fine tailings resulting from oil sands extraction processes. No current fine ... more It is hard to treat fine tailings resulting from oil sands extraction processes. No current fine tailings treatment technology can completely eliminate tailings ponds, despite considerable efforts to address the slow settling of fines and to facilitate the consolidation of sediments. Some treatments use coagulants and coarse solids to form composite or consolidated tailings; others use polymer flocculants. The performance of polymer flocculants is evaluated empirically, with fine tailings often being considered as a black box. Some fundamental studies use single clay systems, such as kaolinite suspended in water, as models to evaluate the performance of polymer flocculants. While it is easier to relate polymer performance to specific conditions in these simpler systems, it is difficult to translate these results to the treatment of the much more complex tailings environment. For the rational design of polymer flocculants, one must understand the interactions between polymers and the several components in tailings. With this information in hand, one can optimize the molecular structure of polymer flocculants to treat oil sands tailings efficiently. In this review, we summarize the published research on flocculation performance within the context of complex fine tailings systems. Furthermore, we describe the compositional complexity of mature fine tailings to help the design of more representative model tailings systems.
Macromolecular Reaction Engineering, 2015
Macromolecular Reaction Engineering, 2015
The effect increasing ethylene incorporation on the development of commercial heterophasic ethyle... more The effect increasing ethylene incorporation on the development of commercial heterophasic ethylene propylene copolymers (HEPCs) was previously evaluated in terms of particle morphology, chemical composition, crystallinity, and microstructure. These polymers were obtained from a commercial gas-phase process and enabled the visualization of the early development of the copolymer phase while including the effects of large-scale production processes on the resulting polymer properties. Based on the ethylene-dependent changes observed for the HEPCs as well as some semi-crystalline TREF fractions, further variable temperature solid-state 13 C NMR experiments were done to observe temperature-dependent shifts in localised mobility within the bulk samples during a heating/melting profile. From these experiments, the development of amorphous polypropylene signals was observed with increasing temperature, which could indirectly be related to the introduction of ethylene defects. It was also observed that polypropylene components with high rigidity remained at high temperatures for the HEPCs but not for the homopolymer. T 1 r experiments were used to differentiate between changes in crystalline and non-crystalline phases based on ethylene incorporation as well as during melting. In this publication, the observations from the perspective of the solid-state analyses are outlined and placed in the context of the evolution of microscopic, chemical, microstructural, and mechanical properties.
Macromolecular Symposia, 2012
Impact polypropylene copolymers (ICPs) have complex microstructures compared to homo-or random co... more Impact polypropylene copolymers (ICPs) have complex microstructures compared to homo-or random copolymers of propylene. Standard analytical techniques are unable to unpack the complex structure of impact copolymers, hence the need to fractionate the material. The investigation of poly(propyleneethylene) block copolymers was conducted in order to understand the copolymer composition and the role of particular components by fractionation. Temperature rising elution fractionation (TREF) was used for fractionation of ICPs which involves breaking up the polymer into small fractions that can be analysed further to give more understanding on the complex microstructures. Two ICP samples (ICP1 and ICP2) with different physical properties were fractionated. The bulk samples as well as the resulting fractions were further analysed using DSC, FTIR and DMA. Below 0 8C, the DMA results of the bulk sample with high ethylene content (ICP1) showed both low storage modulus and stiffness which is in line with expectations. However, it was interesting to note that above 0 8C the trend was reversed, thus ICP2 with low ethylene content had lower storage modulus and stiffness. The DSC and FTIR results of the fractions of the two samples revealed different or inhomogeneous distribution of ethylene content between the samples which explained differences in mechanical properties. The findings emphasize the contributions of phase separation and compatibility between the rubber and the matrix towards physical and mechanical properties.
European Polymer Journal, 2013
By submitting this dissertation, I declare that the entirety of the work contained herein is my o... more By submitting this dissertation, I declare that the entirety of the work contained herein is my own, original work, that I am the owner of the copyright thereof (unless to the extent explicitly otherwise stated) and that I have not previously in its entirety or in part submitted it for obtaining any qualification.
Minerals Engineering, 2017
We synthesized a series of hyperbranched functional polyethylene (HBfPE) flocculants with functio... more We synthesized a series of hyperbranched functional polyethylene (HBfPE) flocculants with functional group contents ranging from 30 and 50 mol%, and used them to flocculate oil sands mature fine tailings (MFT). MFTs (diluted to a concentration of 20 wt%) treated with the novel HBfPE had higher settling rates, lower capillary suction time (CST), and lower turbidity than when treated with a reference polyacrylamide (PAM). Within the HBfPE series, the settling performance improved when the functional group content in the copolymer increased. When combined with centrifugation, the HBfPE flocculants generated sediments with higher solids contents than PAM within a shorter centrifugation time. This may be attributed to the tendency of HBfPE to form smaller flocs that compact more tightly than PAM. Floc development for HBfPE and PAM was compared with focused beam reflectance measurement (FBRM). While floc formation with HBfPE and PAM was similar, it required significantly less mixing energy for optimal performance, due to the significantly lower molecular weight (<10,000 g/mol) of HBfPE.
The Canadian Journal of Chemical Engineering, 2018
† This article has been accepted for publication and undergone full peer review but has not been ... more † This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process, which may lead to differences between this version and the Version of Record. Please cite this article as
Chemosphere, 2018
Polymer-driven flocculation and dewatering of mature fine tailings (MFT) is critical to improve t... more Polymer-driven flocculation and dewatering of mature fine tailings (MFT) is critical to improve their consolidation. MFT flocculation and dewatering depends on the size of the suspended clay particles, and on the composition and properties of the liquid in which they are dispersed. The effect of water chemistry on the polymer-particle dynamics is nontrivial, particularly for non-spherical, polydisperse particles such as natural clays. In this study, we used a response surface methodology to systematically assess the impact of Na and Ca concentration and anionic polyacrylamide dosage in the flocculation and dewatering of MFT. We observed a beneficial synergistic effect between Ca concentration and polyacrylamide dosage, although excess of Ca may reduce polyacrylamide activity. In addition, we investigated the impact of clay particle size on MFT flocculation. Polyacrylamide did not flocculate MFT fractions where the fine clay particles (<2 μm) represented most of the population. Go...
The Canadian Journal of Chemical Engineering, 2015
It is hard to treat fine tailings resulting from oil sands extraction processes. No current fine ... more It is hard to treat fine tailings resulting from oil sands extraction processes. No current fine tailings treatment technology can completely eliminate tailings ponds, despite considerable efforts to address the slow settling of fines and to facilitate the consolidation of sediments. Some treatments use coagulants and coarse solids to form composite or consolidated tailings; others use polymer flocculants. The performance of polymer flocculants is evaluated empirically, with fine tailings often being considered as a black box. Some fundamental studies use single clay systems, such as kaolinite suspended in water, as models to evaluate the performance of polymer flocculants. While it is easier to relate polymer performance to specific conditions in these simpler systems, it is difficult to translate these results to the treatment of the much more complex tailings environment. For the rational design of polymer flocculants, one must understand the interactions between polymers and the several components in tailings. With this information in hand, one can optimize the molecular structure of polymer flocculants to treat oil sands tailings efficiently. In this review, we summarize the published research on flocculation performance within the context of complex fine tailings systems. Furthermore, we describe the compositional complexity of mature fine tailings to help the design of more representative model tailings systems.
Macromolecular Reaction Engineering, 2015
Macromolecular Reaction Engineering, 2015
The effect increasing ethylene incorporation on the development of commercial heterophasic ethyle... more The effect increasing ethylene incorporation on the development of commercial heterophasic ethylene propylene copolymers (HEPCs) was previously evaluated in terms of particle morphology, chemical composition, crystallinity, and microstructure. These polymers were obtained from a commercial gas-phase process and enabled the visualization of the early development of the copolymer phase while including the effects of large-scale production processes on the resulting polymer properties. Based on the ethylene-dependent changes observed for the HEPCs as well as some semi-crystalline TREF fractions, further variable temperature solid-state 13 C NMR experiments were done to observe temperature-dependent shifts in localised mobility within the bulk samples during a heating/melting profile. From these experiments, the development of amorphous polypropylene signals was observed with increasing temperature, which could indirectly be related to the introduction of ethylene defects. It was also observed that polypropylene components with high rigidity remained at high temperatures for the HEPCs but not for the homopolymer. T 1 r experiments were used to differentiate between changes in crystalline and non-crystalline phases based on ethylene incorporation as well as during melting. In this publication, the observations from the perspective of the solid-state analyses are outlined and placed in the context of the evolution of microscopic, chemical, microstructural, and mechanical properties.
Macromolecular Symposia, 2012
Impact polypropylene copolymers (ICPs) have complex microstructures compared to homo-or random co... more Impact polypropylene copolymers (ICPs) have complex microstructures compared to homo-or random copolymers of propylene. Standard analytical techniques are unable to unpack the complex structure of impact copolymers, hence the need to fractionate the material. The investigation of poly(propyleneethylene) block copolymers was conducted in order to understand the copolymer composition and the role of particular components by fractionation. Temperature rising elution fractionation (TREF) was used for fractionation of ICPs which involves breaking up the polymer into small fractions that can be analysed further to give more understanding on the complex microstructures. Two ICP samples (ICP1 and ICP2) with different physical properties were fractionated. The bulk samples as well as the resulting fractions were further analysed using DSC, FTIR and DMA. Below 0 8C, the DMA results of the bulk sample with high ethylene content (ICP1) showed both low storage modulus and stiffness which is in line with expectations. However, it was interesting to note that above 0 8C the trend was reversed, thus ICP2 with low ethylene content had lower storage modulus and stiffness. The DSC and FTIR results of the fractions of the two samples revealed different or inhomogeneous distribution of ethylene content between the samples which explained differences in mechanical properties. The findings emphasize the contributions of phase separation and compatibility between the rubber and the matrix towards physical and mechanical properties.
European Polymer Journal, 2013
By submitting this dissertation, I declare that the entirety of the work contained herein is my o... more By submitting this dissertation, I declare that the entirety of the work contained herein is my own, original work, that I am the owner of the copyright thereof (unless to the extent explicitly otherwise stated) and that I have not previously in its entirety or in part submitted it for obtaining any qualification.
Minerals Engineering, 2017
We synthesized a series of hyperbranched functional polyethylene (HBfPE) flocculants with functio... more We synthesized a series of hyperbranched functional polyethylene (HBfPE) flocculants with functional group contents ranging from 30 and 50 mol%, and used them to flocculate oil sands mature fine tailings (MFT). MFTs (diluted to a concentration of 20 wt%) treated with the novel HBfPE had higher settling rates, lower capillary suction time (CST), and lower turbidity than when treated with a reference polyacrylamide (PAM). Within the HBfPE series, the settling performance improved when the functional group content in the copolymer increased. When combined with centrifugation, the HBfPE flocculants generated sediments with higher solids contents than PAM within a shorter centrifugation time. This may be attributed to the tendency of HBfPE to form smaller flocs that compact more tightly than PAM. Floc development for HBfPE and PAM was compared with focused beam reflectance measurement (FBRM). While floc formation with HBfPE and PAM was similar, it required significantly less mixing energy for optimal performance, due to the significantly lower molecular weight (<10,000 g/mol) of HBfPE.