Gayle Morris - Academia.edu (original) (raw)

Papers by Gayle Morris

Journal of Colloid and Interface Science, Oct 1, 2008

Effective flocculation and dewatering of mineral processing streams containing colloidal clays ha... more Effective flocculation and dewatering of mineral processing streams containing colloidal clays has become increasingly urgent. Release of water from slurries in tailings streams and dam beds for recycle water consumption, is usually slow and incomplete. To achieve fast settling and minimization of retained water, individual particles need to be bound, in the initial stages of thickening, into large, high-density aggregates, which may sediment more rapidly with lower intra-aggregate water content. Quantitative cryo-SEM image analysis shows that the structure of aggregates formed before flocculant addition has a determinative effect on these outcomes. Without flocculant addition, 3 stages occur in the mechanism of primary dewatering of kaolinite at pH 8: initially, the dispersed structures already show edgeedge (EE) and edge-face (EF) inter-particle associations but these are open, loose and easily disrupted; in the hindered settling region, aggregates are in adherent, chain-like structures of EE and stairstep face-face (FF) associations; this network structure slowly partially rearranges from EE chains to more compact face-face (FF) contacts densifying the aggregates with increased settling rates. During settling, the sponge-like network structure with EE and FF string-like aggregates, limits dewatering because the steric effects in the resulting partially-gelled aggregate structures are dominant. With flocculant addition, the internal structure and networking of the pre-aggregates is largely preserved but they are rapidly and effectively bound together by the aggregate-bridging action of the flocculant. The effects of initial pH and Ca ion addition on these structures are also analyzed. Statistical analysis from cryo-SEM imaging shows that there is an inverse correlation of intra-aggregate porosity with Darcian inter-aggregate permeability whereas there is a strong positive correlation of Darcian permeability with settling and primary dewatering rate as a function of pH in suspension. Graphs of partial void contributions also suggest that it is not total porosity that dominates permeability in these systems but the abundance of larger intra-aggregate voids.

Water Research, 2008

Electrosorptive deionisation is an alternative process to remove salt ions from the brackish wate... more Electrosorptive deionisation is an alternative process to remove salt ions from the brackish water. The porous carbon materials are used as electrodes. When charged in low voltage electric fields, they possess a highly charged surface that induces adsorption of salt ions on the surface. This process is reversible, so the adsorbed salt ions can be desorbed and the electrode can be reused. In the study, an ordered mesoporous carbon (OMC) electrode was developed for electrosorptive desalination. The effects of pore arrangement pattern (ordered and random) and pore size distribution (mesopores and micropores) on the desalination performance was investigated by comparing OMC and activated carbon (AC). It were revealed from X-ray diffraction and N(2) sorption measurements that AC has both micropores and mesopores, whereas ordered mesopores are dominant in OMC. Their performance as potential electrodes to remove salt was evaluated by cyclic voltammetry (CV) and galvanostatic charge/discharge tests at a range of electrolyte concentrations and sweep rates. It is deduced that under the same electrochemical condition the specific capacitance values of OMC electrode (i.e. 133 F/g obtained from CV at a sweep rate of 1 mV/s in 0.1M NaCl solution) are larger than those of AC electrode (107 F/g), suggesting that the former has a higher desalting capacity than the latter. Furthermore, the OMC electrode shows a better rate capacity than the AC electrode. In addition, the desalination capacities were quantified by the batch-mode experiment at low voltage of 1.2V in 25 ppm NaCl solution (50 micros/cm conductivity). It was found that the adsorbed ion amounts of OMC and AC electrodes were 11.6 and 4.3 micromol/g, respectively. The excellent electrosorptive desalination performance of OMC electrode might be not only due to the suitable pore size (average of 3.3 nm) for the propagation of the salt ions, but also due to the ordered mesoporous structure that facilitates desorption of the salt. Based on the results, it was found that the development of an ordered mesoporous structure and the control of the number of micropores are two important strategies for optimising electrode material properties for electrosorptive deionisation.

Zeolites are potentially a robust desalination alternative, as they are chemically stable and pos... more Zeolites are potentially a robust desalination alternative, as they are chemically stable and possess the essential properties needed to reject ions. Zeolite membranes could desalinate "challenging" waters, such as saline secondary effluent, without any substantial pre-treatment, due to the robust mechanical properties of ceramic membranes. A novel MFI-type zeolite membrane was developed on a tubular α-Al 2 O 3 substrate by a combined rubbing and secondary hydrothermal growth method. The prepared membrane was characterised by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and single gas (He or N 2 ) permeation and underwent desalination tests with NaCl solutions under different pressures (0.7 MPa and 7 MPa). The results showed that higher pressure resulted in higher Na + rejection and permeate flux. The zeolite membrane achieved a good rejection of Na + (~82%) for a NaCl feed solution with a TDS (total dissolved solids) of 3000 mg·L −1 at an applied pressure of 7 MPa and 21 °C. To explore the

Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2015

Journal of Membrane Science, 2015

Journal of Membrane Science, 2011

Water recycling via treatment from industrial and/or municipal waste sources is one of the key st... more Water recycling via treatment from industrial and/or municipal waste sources is one of the key strategies for resolving water shortages worldwide. Polymer membranes are effective at improving the water quality essential for recycling, but depend on regular cleaning and replacement. Pure ceramic membranes can reduce the cleaning need and last significantly longer in the same applications while possessing the possibility of operating in more aggressive environments not suitable for polymers. In the current work, filtration using a tubular ceramic membrane (␣-Al 2 O 3 or TiO 2 ) was combined with ozonation to remove organic compounds present in a secondary effluent to enhance key quality features of the water (colour and total organic carbon, TOC) for its potential reuse.

Journal of Colloid and Interface Science, 2002

The adsorption kinetics of anionic polyacrylamide flocculant onto kaolinite clay are examined as ... more The adsorption kinetics of anionic polyacrylamide flocculant onto kaolinite clay are examined as a function of flocculant dosage and pH. Special attention has been given to the flocculation effect during the adsorption process and the resulting inhibition of further adsorption. At pH 8.5 the adsorption capacity of anionic polyacrylamide on kaolinite is low while at pH 4.5, the adsorption capacity increases. Flocculant adsorption has been shown to be related to the amount of available surface area, pH, flocculant dosage, and the resulting floc strength, which controls the rate of new surface area exposure and hence the continuation of further adsorption. At both pH 4.5 and pH 8.5, complete adsorption is achieved at low flocculant dosages and adsorption equilibrium is achieved at high flocculant dosages after 1 day. In contrast, at intermediate flocculant dosages adsorption equilibrium is not reached over a 7-day period, due to a continuously increasing surface area. C 2002 Elsevier Science (USA)

Journal of Colloid and Interface Science, 2008

Effective flocculation and dewatering of mineral processing streams containing colloidal clays ha... more Effective flocculation and dewatering of mineral processing streams containing colloidal clays has become increasingly urgent. Release of water from slurries in tailings streams and dam beds for recycle water consumption, is usually slow and incomplete. To achieve fast settling and minimization of retained water, individual particles need to be bound, in the initial stages of thickening, into large, high-density aggregates, which may sediment more rapidly with lower intra-aggregate water content. Quantitative cryo-SEM image analysis shows that the structure of aggregates formed before flocculant addition has a determinative effect on these outcomes. Without flocculant addition, 3 stages occur in the mechanism of primary dewatering of kaolinite at pH 8: initially, the dispersed structures already show edgeedge (EE) and edge-face (EF) inter-particle associations but these are open, loose and easily disrupted; in the hindered settling region, aggregates are in adherent, chain-like structures of EE and stairstep face-face (FF) associations; this network structure slowly partially rearranges from EE chains to more compact face-face (FF) contacts densifying the aggregates with increased settling rates. During settling, the sponge-like network structure with EE and FF string-like aggregates, limits dewatering because the steric effects in the resulting partially-gelled aggregate structures are dominant. With flocculant addition, the internal structure and networking of the pre-aggregates is largely preserved but they are rapidly and effectively bound together by the aggregate-bridging action of the flocculant. The effects of initial pH and Ca ion addition on these structures are also analyzed. Statistical analysis from cryo-SEM imaging shows that there is an inverse correlation of intra-aggregate porosity with Darcian inter-aggregate permeability whereas there is a strong positive correlation of Darcian permeability with settling and primary dewatering rate as a function of pH in suspension. Graphs of partial void contributions also suggest that it is not total porosity that dominates permeability in these systems but the abundance of larger intra-aggregate voids.

International Journal of Mineral Processing, 2009

Smectite suspensions, at low solids contents, are known to be naturally high in volume with diver... more Smectite suspensions, at low solids contents, are known to be naturally high in volume with diverse structural properties. The changing structural properties of smectite aqueous suspensions in the absence and presence of calcium ions were investigated using an acoustosizer and an advanced cryo-SEM technique to further understand and thereby control their environmental impact. In the absence of Ca(II) ions, smectite particles are present as a colloidally stable sol due to electrical double layer repulsion of the negatively charged platelets. The smectite network is observed to be extended throughout the suspension via clay platelets networking with an edge-edge (EE) orientation due to high basal surface repulsion. After the initial addition of Ca(II) ions, the smectite negative zeta potential reduces and the smectite platelets coagulate forming 2 µm aggregates. The platelets are randomly orientated, lettucelike, coagulated aggregates with a high presence of both edge-edge (EE) and edge-face (EF) orientations. After equilibration, the smectite platelets forming an orientated honeycomb cellular structure comprised of face-face (FF) multiply sheet aggregates. The voids in the cellular structure are larger than prior to Ca(II) addition, measured at 2-8 µm. The changing structural properties of a smectite suspension in the absence and presence of Ca(II) greatly influence smectite stability and in turn, mineral processing and/or environmental management. Adequate time is required to allow suppression of the initial swelling of the smectite, full Ca(II) exchange and platelet aggregation.

International Journal of Mineral Processing, 2002

The behaviour of polymer depressants at the talc -water interface was investigated as a function ... more The behaviour of polymer depressants at the talc -water interface was investigated as a function of ionic strength and pH. Adsorption isotherms, microflotation and electrokinetic studies were used to examine the surface interactions involved. The polymers examined were carboxymethyl cellulose (CMC) and two synthetic polyacrylamides (PAM-A and PAM-N). The adsorption of the two anionic polymers, CMC and PAM-A, on talc, and hence, talc depression, is greatest when electrostatic repulsion is minimized. At high pH values and low ionic strength, the adsorption density of the anionic polymers on talc is low whilst at either high ionic strength or low pH, the adsorption density increases; talc depression is therefore largely influenced by variations in solution conditions. The adsorption of the nonionic polymers, PAM-N, on talc is not influenced by ionic strength or pH. The polymers exhibit Langmuir adsorption behaviour with adsorption occurring on the talc face surface and, possibly, the edge surface. The adsorbed polymer layer thicknesses, calculated from electrophoretic mobility measurements, corresponded to a monolayer indicating that adsorption of the polymers onto the talc surface occurs in a flat conformation. D

Desalination and Water Treatment, 2011

A mesoporous titania (TiO2) membrane on an alumina support was successfully fabricated via the so... more A mesoporous titania (TiO2) membrane on an alumina support was successfully fabricated via the sol–gel processing method. The effects of combined ozonation and TiO2 membrane filtration on the permeate flux and permeate quality were investigated. Ozone injection into the feed water during the filtration resulted in an increase in the permeate flux within the first 0.5 h. Ozonation decreased the

Desalination, 2008

The electrosorptive deionisation process has been investigated to develop the technology into a s... more The electrosorptive deionisation process has been investigated to develop the technology into a system for desalination. Experiments have been conducted in a reactor system and it has been found that the activated carbon has some deionisation capacity due to its very high adsorption capacity and conductivity, so it can be used as an alternative electrode material. Surface modifications have been made to the activated carbon material, including alkaline treatment and loading of titanium dioxide nanoparticles. The specific surface areas (BET), average pore size and total pore volume were analysed by surface area and porosity analyzer. The modified electrode material demonstrated enhanced electrosorption capacity and reduced physical sorption at the pores, so desorption is more efficient. An innovative approach for desorption of the saturated activated carbon electrodes has been tried using ultrasonic vibration and increased temperature, the results of regeneration in water, aided by ultrasonic at 20°C and 50°C are presented as well. Cyclic voltammetry experiments at various scan rates were conducted using a potentiostat to analyse the electrical double-layer capacitance of the activated carbon materials. This preliminary study demonstrated that activated carbon granules have the potential to be cost-effective electrode materials for desalting brackish water. The improvement of the electrosorption efficiency can be achieved by surface modification by chemicals and metal oxide nanoparticles such as TiO 2 .

Colloids and Surfaces A: Physicochemical and Engineering Aspects, 1999

A microgel particle is a cross-linked latex particle which is swollen by a good solvent. Particle... more A microgel particle is a cross-linked latex particle which is swollen by a good solvent. Particle swelling is intrinsically related to the nature of the interaction between the polymer and continuous phase. Microgel particles based on PNP [PNP=poly(N-isopropylacrylamide)] are particularly interesting since the parent homopolymer undergoes a coil-toglobule transition in water when the temperature increases above 32°C. In this work, PCS (photon correlation spectroscopy) and SANS (small-angle neutron scattering) are employed in a complementary manner to study the environmentally induced de-swelling of PNP particles. Further, we show that particle de-swelling may be induced at room temperature by addition of alcohols or excluded free polymer (i.e. non-adsorbing free polymer) to the continuous phase. (The extents of particle de-swelling observed using these additives are similar to those achieved by heating the pure microgel particles in water above 32°C.) Particle de-swelling in the presence of added alcohol or free polymer arises from ''co-non-solvency'' and osmotic de-swelling effects, respectively.

Colloids and Surfaces A: Physicochemical and Engineering Aspects, 1999

The influence of pH and surface chemical state on rheological behaviour was investigated for vari... more The influence of pH and surface chemical state on rheological behaviour was investigated for variations of silicaand alumina-coated, aluminium-doped titania pigment suspensions. The variation in rheological properties correlates with the change in the pigment surface properties, determined from electrophoresis measurements, atomic concentrations, chemical states and modified Auger parameters derived from X-ray photoelectron spectroscopy ( XPS). Pigment suspensions exhibited a maximum yield stress and viscosity at or near the isoelectric point (iep). At a pH where the magnitude of the zeta potential of the titania pigment is high, a low-viscosity, dispersed suspension was obtained. The pH of the maximum yield value of the pigment suspension increases with increasing aluminium hydroxyl group density and decreases with increasing silicon hydroxyl group density. Low-viscosity pigment dispersions were obtained with increasing aluminium surface concentration and further reduced with an increase in the silicon surface concentration. Pigment particle attractions are chiefly dictated by van der Waals forces and heteroaggregation. The pigment aggregate strength therefore depends upon the Hamaker constant of the heterogeneous pigment based on the proportion of the respective surface groups. * Corresponding author. Tel: +61 8 8302 3694; on the rheology of pure titania [2,3] and titania Fax: +61 8 8302 3683. paint formulations [4] there has been little work 0927-7757/99/$ -see front matter

Carbon, 2009

Capacitive deionization (CDI) represents an alternative process to remove the ions from the brack... more Capacitive deionization (CDI) represents an alternative process to remove the ions from the brackish water. In this study two series of ordered mesoporous carbons (OMCs) that demonstrated the potential use for capacitive desalination have been synthesized by a modified sol-gel process involving nickel salts. It was shown that the preferred formation of crownether type complexes between nickel ions and triblock copolymers resulted in higher BET surface area and smaller mesopores. As the electrode materials for CDI, OMC obtained by the addition of NiSO 4 AE 6H 2 O exhibited best electrochemical performance compared with other OMCs and a commercial activated carbon either in 0.1 M NaCl solution or in 0.0008 M NaCl solution, plus the amount of adsorbed ions measured by a flow through apparatus reached 15.9 lmol g À1 and the ions could be fully released into the solution.

Journal of Colloid and Interface Science, Oct 1, 2008

Effective flocculation and dewatering of mineral processing streams containing colloidal clays ha... more Effective flocculation and dewatering of mineral processing streams containing colloidal clays has become increasingly urgent. Release of water from slurries in tailings streams and dam beds for recycle water consumption, is usually slow and incomplete. To achieve fast settling and minimization of retained water, individual particles need to be bound, in the initial stages of thickening, into large, high-density aggregates, which may sediment more rapidly with lower intra-aggregate water content. Quantitative cryo-SEM image analysis shows that the structure of aggregates formed before flocculant addition has a determinative effect on these outcomes. Without flocculant addition, 3 stages occur in the mechanism of primary dewatering of kaolinite at pH 8: initially, the dispersed structures already show edgeedge (EE) and edge-face (EF) inter-particle associations but these are open, loose and easily disrupted; in the hindered settling region, aggregates are in adherent, chain-like structures of EE and stairstep face-face (FF) associations; this network structure slowly partially rearranges from EE chains to more compact face-face (FF) contacts densifying the aggregates with increased settling rates. During settling, the sponge-like network structure with EE and FF string-like aggregates, limits dewatering because the steric effects in the resulting partially-gelled aggregate structures are dominant. With flocculant addition, the internal structure and networking of the pre-aggregates is largely preserved but they are rapidly and effectively bound together by the aggregate-bridging action of the flocculant. The effects of initial pH and Ca ion addition on these structures are also analyzed. Statistical analysis from cryo-SEM imaging shows that there is an inverse correlation of intra-aggregate porosity with Darcian inter-aggregate permeability whereas there is a strong positive correlation of Darcian permeability with settling and primary dewatering rate as a function of pH in suspension. Graphs of partial void contributions also suggest that it is not total porosity that dominates permeability in these systems but the abundance of larger intra-aggregate voids.

Water Research, 2008

Electrosorptive deionisation is an alternative process to remove salt ions from the brackish wate... more Electrosorptive deionisation is an alternative process to remove salt ions from the brackish water. The porous carbon materials are used as electrodes. When charged in low voltage electric fields, they possess a highly charged surface that induces adsorption of salt ions on the surface. This process is reversible, so the adsorbed salt ions can be desorbed and the electrode can be reused. In the study, an ordered mesoporous carbon (OMC) electrode was developed for electrosorptive desalination. The effects of pore arrangement pattern (ordered and random) and pore size distribution (mesopores and micropores) on the desalination performance was investigated by comparing OMC and activated carbon (AC). It were revealed from X-ray diffraction and N(2) sorption measurements that AC has both micropores and mesopores, whereas ordered mesopores are dominant in OMC. Their performance as potential electrodes to remove salt was evaluated by cyclic voltammetry (CV) and galvanostatic charge/discharge tests at a range of electrolyte concentrations and sweep rates. It is deduced that under the same electrochemical condition the specific capacitance values of OMC electrode (i.e. 133 F/g obtained from CV at a sweep rate of 1 mV/s in 0.1M NaCl solution) are larger than those of AC electrode (107 F/g), suggesting that the former has a higher desalting capacity than the latter. Furthermore, the OMC electrode shows a better rate capacity than the AC electrode. In addition, the desalination capacities were quantified by the batch-mode experiment at low voltage of 1.2V in 25 ppm NaCl solution (50 micros/cm conductivity). It was found that the adsorbed ion amounts of OMC and AC electrodes were 11.6 and 4.3 micromol/g, respectively. The excellent electrosorptive desalination performance of OMC electrode might be not only due to the suitable pore size (average of 3.3 nm) for the propagation of the salt ions, but also due to the ordered mesoporous structure that facilitates desorption of the salt. Based on the results, it was found that the development of an ordered mesoporous structure and the control of the number of micropores are two important strategies for optimising electrode material properties for electrosorptive deionisation.

Zeolites are potentially a robust desalination alternative, as they are chemically stable and pos... more Zeolites are potentially a robust desalination alternative, as they are chemically stable and possess the essential properties needed to reject ions. Zeolite membranes could desalinate "challenging" waters, such as saline secondary effluent, without any substantial pre-treatment, due to the robust mechanical properties of ceramic membranes. A novel MFI-type zeolite membrane was developed on a tubular α-Al 2 O 3 substrate by a combined rubbing and secondary hydrothermal growth method. The prepared membrane was characterised by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and single gas (He or N 2 ) permeation and underwent desalination tests with NaCl solutions under different pressures (0.7 MPa and 7 MPa). The results showed that higher pressure resulted in higher Na + rejection and permeate flux. The zeolite membrane achieved a good rejection of Na + (~82%) for a NaCl feed solution with a TDS (total dissolved solids) of 3000 mg·L −1 at an applied pressure of 7 MPa and 21 °C. To explore the

Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2015

Journal of Membrane Science, 2015

Journal of Membrane Science, 2011

Water recycling via treatment from industrial and/or municipal waste sources is one of the key st... more Water recycling via treatment from industrial and/or municipal waste sources is one of the key strategies for resolving water shortages worldwide. Polymer membranes are effective at improving the water quality essential for recycling, but depend on regular cleaning and replacement. Pure ceramic membranes can reduce the cleaning need and last significantly longer in the same applications while possessing the possibility of operating in more aggressive environments not suitable for polymers. In the current work, filtration using a tubular ceramic membrane (␣-Al 2 O 3 or TiO 2 ) was combined with ozonation to remove organic compounds present in a secondary effluent to enhance key quality features of the water (colour and total organic carbon, TOC) for its potential reuse.

Journal of Colloid and Interface Science, 2002

The adsorption kinetics of anionic polyacrylamide flocculant onto kaolinite clay are examined as ... more The adsorption kinetics of anionic polyacrylamide flocculant onto kaolinite clay are examined as a function of flocculant dosage and pH. Special attention has been given to the flocculation effect during the adsorption process and the resulting inhibition of further adsorption. At pH 8.5 the adsorption capacity of anionic polyacrylamide on kaolinite is low while at pH 4.5, the adsorption capacity increases. Flocculant adsorption has been shown to be related to the amount of available surface area, pH, flocculant dosage, and the resulting floc strength, which controls the rate of new surface area exposure and hence the continuation of further adsorption. At both pH 4.5 and pH 8.5, complete adsorption is achieved at low flocculant dosages and adsorption equilibrium is achieved at high flocculant dosages after 1 day. In contrast, at intermediate flocculant dosages adsorption equilibrium is not reached over a 7-day period, due to a continuously increasing surface area. C 2002 Elsevier Science (USA)

Journal of Colloid and Interface Science, 2008

Effective flocculation and dewatering of mineral processing streams containing colloidal clays ha... more Effective flocculation and dewatering of mineral processing streams containing colloidal clays has become increasingly urgent. Release of water from slurries in tailings streams and dam beds for recycle water consumption, is usually slow and incomplete. To achieve fast settling and minimization of retained water, individual particles need to be bound, in the initial stages of thickening, into large, high-density aggregates, which may sediment more rapidly with lower intra-aggregate water content. Quantitative cryo-SEM image analysis shows that the structure of aggregates formed before flocculant addition has a determinative effect on these outcomes. Without flocculant addition, 3 stages occur in the mechanism of primary dewatering of kaolinite at pH 8: initially, the dispersed structures already show edgeedge (EE) and edge-face (EF) inter-particle associations but these are open, loose and easily disrupted; in the hindered settling region, aggregates are in adherent, chain-like structures of EE and stairstep face-face (FF) associations; this network structure slowly partially rearranges from EE chains to more compact face-face (FF) contacts densifying the aggregates with increased settling rates. During settling, the sponge-like network structure with EE and FF string-like aggregates, limits dewatering because the steric effects in the resulting partially-gelled aggregate structures are dominant. With flocculant addition, the internal structure and networking of the pre-aggregates is largely preserved but they are rapidly and effectively bound together by the aggregate-bridging action of the flocculant. The effects of initial pH and Ca ion addition on these structures are also analyzed. Statistical analysis from cryo-SEM imaging shows that there is an inverse correlation of intra-aggregate porosity with Darcian inter-aggregate permeability whereas there is a strong positive correlation of Darcian permeability with settling and primary dewatering rate as a function of pH in suspension. Graphs of partial void contributions also suggest that it is not total porosity that dominates permeability in these systems but the abundance of larger intra-aggregate voids.

International Journal of Mineral Processing, 2009

Smectite suspensions, at low solids contents, are known to be naturally high in volume with diver... more Smectite suspensions, at low solids contents, are known to be naturally high in volume with diverse structural properties. The changing structural properties of smectite aqueous suspensions in the absence and presence of calcium ions were investigated using an acoustosizer and an advanced cryo-SEM technique to further understand and thereby control their environmental impact. In the absence of Ca(II) ions, smectite particles are present as a colloidally stable sol due to electrical double layer repulsion of the negatively charged platelets. The smectite network is observed to be extended throughout the suspension via clay platelets networking with an edge-edge (EE) orientation due to high basal surface repulsion. After the initial addition of Ca(II) ions, the smectite negative zeta potential reduces and the smectite platelets coagulate forming 2 µm aggregates. The platelets are randomly orientated, lettucelike, coagulated aggregates with a high presence of both edge-edge (EE) and edge-face (EF) orientations. After equilibration, the smectite platelets forming an orientated honeycomb cellular structure comprised of face-face (FF) multiply sheet aggregates. The voids in the cellular structure are larger than prior to Ca(II) addition, measured at 2-8 µm. The changing structural properties of a smectite suspension in the absence and presence of Ca(II) greatly influence smectite stability and in turn, mineral processing and/or environmental management. Adequate time is required to allow suppression of the initial swelling of the smectite, full Ca(II) exchange and platelet aggregation.

International Journal of Mineral Processing, 2002

The behaviour of polymer depressants at the talc -water interface was investigated as a function ... more The behaviour of polymer depressants at the talc -water interface was investigated as a function of ionic strength and pH. Adsorption isotherms, microflotation and electrokinetic studies were used to examine the surface interactions involved. The polymers examined were carboxymethyl cellulose (CMC) and two synthetic polyacrylamides (PAM-A and PAM-N). The adsorption of the two anionic polymers, CMC and PAM-A, on talc, and hence, talc depression, is greatest when electrostatic repulsion is minimized. At high pH values and low ionic strength, the adsorption density of the anionic polymers on talc is low whilst at either high ionic strength or low pH, the adsorption density increases; talc depression is therefore largely influenced by variations in solution conditions. The adsorption of the nonionic polymers, PAM-N, on talc is not influenced by ionic strength or pH. The polymers exhibit Langmuir adsorption behaviour with adsorption occurring on the talc face surface and, possibly, the edge surface. The adsorbed polymer layer thicknesses, calculated from electrophoretic mobility measurements, corresponded to a monolayer indicating that adsorption of the polymers onto the talc surface occurs in a flat conformation. D

Desalination and Water Treatment, 2011

A mesoporous titania (TiO2) membrane on an alumina support was successfully fabricated via the so... more A mesoporous titania (TiO2) membrane on an alumina support was successfully fabricated via the sol–gel processing method. The effects of combined ozonation and TiO2 membrane filtration on the permeate flux and permeate quality were investigated. Ozone injection into the feed water during the filtration resulted in an increase in the permeate flux within the first 0.5 h. Ozonation decreased the

Desalination, 2008

The electrosorptive deionisation process has been investigated to develop the technology into a s... more The electrosorptive deionisation process has been investigated to develop the technology into a system for desalination. Experiments have been conducted in a reactor system and it has been found that the activated carbon has some deionisation capacity due to its very high adsorption capacity and conductivity, so it can be used as an alternative electrode material. Surface modifications have been made to the activated carbon material, including alkaline treatment and loading of titanium dioxide nanoparticles. The specific surface areas (BET), average pore size and total pore volume were analysed by surface area and porosity analyzer. The modified electrode material demonstrated enhanced electrosorption capacity and reduced physical sorption at the pores, so desorption is more efficient. An innovative approach for desorption of the saturated activated carbon electrodes has been tried using ultrasonic vibration and increased temperature, the results of regeneration in water, aided by ultrasonic at 20°C and 50°C are presented as well. Cyclic voltammetry experiments at various scan rates were conducted using a potentiostat to analyse the electrical double-layer capacitance of the activated carbon materials. This preliminary study demonstrated that activated carbon granules have the potential to be cost-effective electrode materials for desalting brackish water. The improvement of the electrosorption efficiency can be achieved by surface modification by chemicals and metal oxide nanoparticles such as TiO 2 .

Colloids and Surfaces A: Physicochemical and Engineering Aspects, 1999

A microgel particle is a cross-linked latex particle which is swollen by a good solvent. Particle... more A microgel particle is a cross-linked latex particle which is swollen by a good solvent. Particle swelling is intrinsically related to the nature of the interaction between the polymer and continuous phase. Microgel particles based on PNP [PNP=poly(N-isopropylacrylamide)] are particularly interesting since the parent homopolymer undergoes a coil-toglobule transition in water when the temperature increases above 32°C. In this work, PCS (photon correlation spectroscopy) and SANS (small-angle neutron scattering) are employed in a complementary manner to study the environmentally induced de-swelling of PNP particles. Further, we show that particle de-swelling may be induced at room temperature by addition of alcohols or excluded free polymer (i.e. non-adsorbing free polymer) to the continuous phase. (The extents of particle de-swelling observed using these additives are similar to those achieved by heating the pure microgel particles in water above 32°C.) Particle de-swelling in the presence of added alcohol or free polymer arises from ''co-non-solvency'' and osmotic de-swelling effects, respectively.

Colloids and Surfaces A: Physicochemical and Engineering Aspects, 1999

The influence of pH and surface chemical state on rheological behaviour was investigated for vari... more The influence of pH and surface chemical state on rheological behaviour was investigated for variations of silicaand alumina-coated, aluminium-doped titania pigment suspensions. The variation in rheological properties correlates with the change in the pigment surface properties, determined from electrophoresis measurements, atomic concentrations, chemical states and modified Auger parameters derived from X-ray photoelectron spectroscopy ( XPS). Pigment suspensions exhibited a maximum yield stress and viscosity at or near the isoelectric point (iep). At a pH where the magnitude of the zeta potential of the titania pigment is high, a low-viscosity, dispersed suspension was obtained. The pH of the maximum yield value of the pigment suspension increases with increasing aluminium hydroxyl group density and decreases with increasing silicon hydroxyl group density. Low-viscosity pigment dispersions were obtained with increasing aluminium surface concentration and further reduced with an increase in the silicon surface concentration. Pigment particle attractions are chiefly dictated by van der Waals forces and heteroaggregation. The pigment aggregate strength therefore depends upon the Hamaker constant of the heterogeneous pigment based on the proportion of the respective surface groups. * Corresponding author. Tel: +61 8 8302 3694; on the rheology of pure titania [2,3] and titania Fax: +61 8 8302 3683. paint formulations [4] there has been little work 0927-7757/99/$ -see front matter

Carbon, 2009

Capacitive deionization (CDI) represents an alternative process to remove the ions from the brack... more Capacitive deionization (CDI) represents an alternative process to remove the ions from the brackish water. In this study two series of ordered mesoporous carbons (OMCs) that demonstrated the potential use for capacitive desalination have been synthesized by a modified sol-gel process involving nickel salts. It was shown that the preferred formation of crownether type complexes between nickel ions and triblock copolymers resulted in higher BET surface area and smaller mesopores. As the electrode materials for CDI, OMC obtained by the addition of NiSO 4 AE 6H 2 O exhibited best electrochemical performance compared with other OMCs and a commercial activated carbon either in 0.1 M NaCl solution or in 0.0008 M NaCl solution, plus the amount of adsorbed ions measured by a flow through apparatus reached 15.9 lmol g À1 and the ions could be fully released into the solution.