title: The Use of Solubility Parameters to Select Membrane Materials for Pervaporation of Organic Mixtures

authors: Buckley-Smith, Marion

subjects: pervaporation

abstract: Pevaporation is a method for separating volatile components from liquid mixtures at ambient temperatures. The paint processing industry uses Hansen solubility parameters (HSP) to indicate polymer solubility. The potential of this method to predict solvent-polymer affinity was investigated for screening potential membrane materials for the pervaporation of a model solution containing linalool and linalyl acetate (major components of lavender essential oil), in ethanol. 

Published HSP values were collated for various polymers, and statistically analysed to determine variations in HSP values for polymer species. An investigation of published research into pervaporation of organic/organic binary solutions separated by homogeneous membranes indicated that the solvent whose HSP value was closest to that of the polymer would preferentially permeate. This relationship did not always hold for halogenated solvents or aqueous/organic solutions. Conflicting literature regarding the relationship between solvent uptake by polymers and HSP relative energy differences was resolved using a logarithmic relationship between these two parameters. 

The following membranes were selected, using their HSP to indicate their potential to interact with lavender oil components: Polyamide (PA: 26.9 micro;m), Polycarbonate (PC: 20.5 micro;m), Poly(ether imide) (PEI: 29.2 micro;m), Poly(ether sulphone) (PES: 27.6 micro;m), Polyethylene (HDPE: 10 micro;m, LDPE: 13-30 micro;m), Polyimide (PI: 30.0 micro;m), Poly(methyl methacrylate) (PMMA: 50 micro;m), Polypropylene (PP: 15.9 micro;m), and Poly(tetrafluoro ethylene) (PTFE: 26.7 micro;m). The HSP (dispersive, polar  hydrogen bonding components) for each membrane were calculated using the mean value obtained from swelling experiments, group contribution (calculated using Hoftyzer-Van Krevelen, Hoy and Beerbower methods), refractive indices (dispersive component), dielectric constants (polar component), and published HSP values. 

Pervaporation experiments investigated the effect of membrane thickness, process temperature, permeate pressure, impinging jet heights, feed flow rates and concentrations, and pre-soaking the membrane; on flow rate and selectivity in a polyethylene membrane. Membrane thickness was the dominant factor in membrane selectivity; the thinnest membranes (11.3-14.8 micro;m) had much poorer selectivity than membranes gt;24.7 micro;m. Temperatures between 22-34ordm;C, permeate pressure lt;10 kPa, impinging jet heights between 0.36-3.36 mm, feed flow rates between 541-1328 mL/min and concentrations between 1.78-6.01 % v/v of linalool and linalyl acetate in ethanol did not significantly affect selectivity. Flow rates increased with operating temperature, permeate pressure, and impinging jet heights. However, feed flow rate and concentration had no effect on membrane flux rate. Pre-soaking the membrane reduced the time to reach steady-state. 

Selected membranes were further investigated under standard operating conditions (permeate temperature 30ordm;C, permeate pressure lt;10 kPa, impinging jet height 1.36 mm, feed flow rate 804 mL/min and feed concentration of 5% v/v of linalool and linalyl acetate in ethanol). PMMA completely disintegrated in feed solution, and PC was too brittle to make an effective homogeneous membrane. PA, PC, PEI and PTFE had the highest efficiency (selectivity x flow rate) in their homogeneous form. However, PEI, PI and PTFE had the greatest selectivity, thus further trials should be done to improve stability and flow rates through these membranes. 

Pervaporation selectivity did not always follow trends predicted by HSP. Although polymers such as PA, PEI, PES, and PI preferentially permeated linalool as predicted, PC, PP and PTFE did not preferentially permeate linalyl acetate. This may have been due to the difference in size and diffusivity of these molecules (linalyl acetate, the larger molecule, did not follow the sorption selectivity predictions), or reliability of literature HSP values and those calculated by group contribution. 

This research shows that HSP is a good screening method for pervaporation membranes, especially where the molecules being separated are of comparable size. Polymers that have HSP close to the desired component and not to other components tend to have the best selectivity and flux characteristics. However, diffusion is an important factor, and is not completely accounted for by HSP. 

Recommendations for further research include: carrying out pervaporation analyses of selected polymers using pure lavender essential oil; modifying polymers to form asymmetric or composite membranes with improved permeation characteristics; and potential use of thin channel inverse gas chromatography to determine a more accurate HSP which includes diffusivity.

text: The Use of Solubility Parameters to Select Membrane Materials for Pervaporation of Organic Mixtures Pevaporation is a method for separating volatile components from liquid mixtures at ambient temperatures. The paint processing industry uses Hansen solubility parameters (HSP) to indicate polymer solubility. The potential of this method to predict solvent-polymer affinity was investigated for screening potential membrane materials for the pervaporation of a model solution containing linalool and linalyl acetate (major components of lavender essential oil), in ethanol. 

Published HSP values were collated for various polymers, and statistically analysed to determine variations in HSP values for polymer species. An investigation of published research into pervaporation of organic/organic binary solutions separated by homogeneous membranes indicated that the solvent whose HSP value was closest to that of the polymer would preferentially permeate. This relationship did not always hold for halogenated solvents or aqueous/organic solutions. Conflicting literature regarding the relationship between solvent uptake by polymers and HSP relative energy differences was resolved using a logarithmic relationship between these two parameters. 

The following membranes were selected, using their HSP to indicate their potential to interact with lavender oil components: Polyamide (PA: 26.9 micro;m), Polycarbonate (PC: 20.5 micro;m), Poly(ether imide) (PEI: 29.2 micro;m), Poly(ether sulphone) (PES: 27.6 micro;m), Polyethylene (HDPE: 10 micro;m, LDPE: 13-30 micro;m), Polyimide (PI: 30.0 micro;m), Poly(methyl methacrylate) (PMMA: 50 micro;m), Polypropylene (PP: 15.9 micro;m), and Poly(tetrafluoro ethylene) (PTFE: 26.7 micro;m). The HSP (dispersive, polar  hydrogen bonding components) for each membrane were calculated using the mean value obtained from swelling experiments, group contribution (calculated using Hoftyzer-Van Krevelen, Hoy and Beerbower methods), refractive indices (dispersive component), dielectric constants (polar component), and published HSP values. 

Pervaporation experiments investigated the effect of membrane thickness, process temperature, permeate pressure, impinging jet heights, feed flow rates and concentrations, and pre-soaking the membrane; on flow rate and selectivity in a polyethylene membrane. Membrane thickness was the dominant factor in membrane selectivity; the thinnest membranes (11.3-14.8 micro;m) had much poorer selectivity than membranes gt;24.7 micro;m. Temperatures between 22-34ordm;C, permeate pressure lt;10 kPa, impinging jet heights between 0.36-3.36 mm, feed flow rates between 541-1328 mL/min and concentrations between 1.78-6.01 % v/v of linalool and linalyl acetate in ethanol did not significantly affect selectivity. Flow rates increased with operating temperature, permeate pressure, and impinging jet heights. However, feed flow rate and concentration had no effect on membrane flux rate. Pre-soaking the membrane reduced the time to reach steady-state. 

Selected membranes were further investigated under standard operating conditions (permeate temperature 30ordm;C, permeate pressure lt;10 kPa, impinging jet height 1.36 mm, feed flow rate 804 mL/min and feed concentration of 5% v/v of linalool and linalyl acetate in ethanol). PMMA completely disintegrated in feed solution, and PC was too brittle to make an effective homogeneous membrane. PA, PC, PEI and PTFE had the highest efficiency (selectivity x flow rate) in their homogeneous form. However, PEI, PI and PTFE had the greatest selectivity, thus further trials should be done to improve stability and flow rates through these membranes. 

Pervaporation selectivity did not always follow trends predicted by HSP. Although polymers such as PA, PEI, PES, and PI preferentially permeated linalool as predicted, PC, PP and PTFE did not preferentially permeate linalyl acetate. This may have been due to the difference in size and diffusivity of these molecules (linalyl acetate, the larger molecule, did not follow the sorption selectivity predictions), or reliability of literature HSP values and those calculated by group contribution. 

This research shows that HSP is a good screening method for pervaporation membranes, especially where the molecules being separated are of comparable size. Polymers that have HSP close to the desired component and not to other components tend to have the best selectivity and flux characteristics. However, diffusion is an important factor, and is not completely accounted for by HSP. 

Recommendations for further research include: carrying out pervaporation analyses of selected polymers using pure lavender essential oil; modifying polymers to form asymmetric or composite membranes with improved permeation characteristics; and potential use of thin channel inverse gas chromatography to determine a more accurate HSP which includes diffusivity.

year: 2006

title: Using the framework for design alternatives and variants

authors: Bowen, Judy

subjects: computer science

abstract: This paper presents a framework for considering multi-team, multi‐disciplinary design of interactive systems in a structured manner. IT practitioners can read the paper to gain a deeper understanding and new perspectives of interaction design processes.

text: Using the framework for design alternatives and variants This paper presents a framework for considering multi-team, multi‐disciplinary design of interactive systems in a structured manner. IT practitioners can read the paper to gain a deeper understanding and new perspectives of interaction design processes.

year: 2019-02

title: Tangihanga: Through the eyes of young Maori women

authors: Wihongi, Hemaima

subjects: tangihanga

abstract: Tangihanga describes the Māori customary way of approaching death. The aim of this research is to explore the tangihanga experiences of young Māori women. The meanings they create, the learning they experience, and the social relationships they negotiate whilst at tangihanga are of interest. The contribution that tangihanga makes to mediating bereavement, grief and loss will also be investigated. This research seeks to broaden the understanding around the practices, beliefs and meanings that are associated with the processes of Tangihanga as experienced by young Māori women.
This study interviewed young Māori women between the ages of eighteen to twenty four. Face to face interviews were carried out with the use of a semi-structured interview schedule. The interviews provided access to the participant‟s experiences and understanding of tangihanga and the customary practices that are associated with it.
The findings from this study support the notion that the tangihanga is a fundamental event for Māori. The participants found tangi to be a place where their relationships within both their immediate and extended whānau were strengthened. This setting allowed the young women to express their grief in an open and supportive environment surrounded by their whānau. The tangi also provided a place of learning for the young women as they learned about the tikanga and kawa or customary practices in relation to tangihanga. This learning occurred in a number of ways; by observation, through participation and the receiving of instruction from older family members. Thus the tangi provided the opportunity for the transfer of cultural knowledge between generations. These findings suggest that the tangi plays an important role in young women‟s lives as it provides them with access to Māori communities and cultural learning. The challenge for us today is to ensure that these opportunities continue to occur for young Māori women.

text: Tangihanga: Through the eyes of young Maori women Tangihanga describes the Māori customary way of approaching death. The aim of this research is to explore the tangihanga experiences of young Māori women. The meanings they create, the learning they experience, and the social relationships they negotiate whilst at tangihanga are of interest. The contribution that tangihanga makes to mediating bereavement, grief and loss will also be investigated. This research seeks to broaden the understanding around the practices, beliefs and meanings that are associated with the processes of Tangihanga as experienced by young Māori women.
This study interviewed young Māori women between the ages of eighteen to twenty four. Face to face interviews were carried out with the use of a semi-structured interview schedule. The interviews provided access to the participant‟s experiences and understanding of tangihanga and the customary practices that are associated with it.
The findings from this study support the notion that the tangihanga is a fundamental event for Māori. The participants found tangi to be a place where their relationships within both their immediate and extended whānau were strengthened. This setting allowed the young women to express their grief in an open and supportive environment surrounded by their whānau. The tangi also provided a place of learning for the young women as they learned about the tikanga and kawa or customary practices in relation to tangihanga. This learning occurred in a number of ways; by observation, through participation and the receiving of instruction from older family members. Thus the tangi provided the opportunity for the transfer of cultural knowledge between generations. These findings suggest that the tangi plays an important role in young women‟s lives as it provides them with access to Māori communities and cultural learning. The challenge for us today is to ensure that these opportunities continue to occur for young Māori women.

year: 2013