Periodic Reporting for period 2 - TUNEMEM (Externally Tuneable Separations for Membrane Reactors)
Berichtszeitraum: 2017-02-01 bis 2018-02-28
I will develop an all new type of reactor for pharmaceutical and chemical process applications – the ‘tuneable membrane reactor’. These contain ground-breaking conducting polymer composite membranes that will allow in-situ tuning of the molecular selectivity for both neutral and charged species through them. This is revolutionary: current state-of-the-art membranes can be electrically tuned for charged species only. The action is timely, developing a new technology that can give the EU a competitive advantage for our declining pharmaceutical and (petro)chemical manufacturing base and builds on my recent research innovations.
To do this, my team of 3 PDRAs, 3 PhDs and I will develop unique stable polymer-polymer acid-nanoparticle composite membranes that can be externally electrically tuned to different pore sizes and/or molecular selectivity, uniquely tuning for neutral and charged species. We will characterise the chemical, physical and transport mechanisms responsible for the membrane tuneablity and relate these to transport models. We will then determine the feasibility of applying these unique tuneable membranes into membrane reactors, to allow in-situ external control of two key reactor parameters currently not possible: (1) Membrane fouling - membrane pore size/free volume and charge will be changed by applied potential allowing the fouling layer to be pushed off/through the membrane. (2) Precise external control of the reactant and product spectrum in the reactor by modifying species retention. By doing this, these tuneable membranes can be used to control the reaction rate, emissions and catalyst retention to maximise reaction rate and selectivity. This increases energy efficiency and emission control, helping the EU 20-20-20 environmental targets to be met. The overall impact applies beyond the action – we will be able to increase the control of membrane separations used worldwide, helping industries including food, water, healthcare and chemicals.
To do this, the hypothesis I am looking to test in TUNEMEM is: Can stable, robust and predictably tuneable conducting polymer membranes be synthesised and then applied in chemical and biochemical reactors in both aqueous and organic reaction systems to control fouling and active catalyst recovery, reaction rates, and product quality (selectivity and yield)?
Objectives: corresponding to the four work packages (WPs).
1. To develop and characterise novel ultrafiltration and nanofiltration range large acid doped PANI composite and/or mixed matrix membranes that, unlike any other membranes, can produce a predictable and repeatable change in molecular weight cut-off under external electrical stimulation for electrically neutral species that is stable over an extended period of operation in both organic and aqueous reaction systems.
2. To characterise and mathematically describe the mass transfer mechanisms and fouling of electrically tuneable membranes. This will provide the first mathematical and mechanistic description of the electrically tuneable mass transport mechanisms and fouling/removal mechanisms for these types of conducting polymer membranes compared to conventional polymer membranes.
3. To determine the feasibility of these unique tuneable membranes to control the fouling, reaction rate, and catalyst activity in homogeneous catalysed extractive membrane reactors to maximise the reaction rate, production rate (membrane flux), catalyst retention and catalyst lifetime in both organic solvent and aqueous reaction systems. With objective 4 we invent a new reactor type: ‘tuneable membrane reactors’.
4. To determine the feasibility of these unique tuneable membranes to control the fouling, reaction rate, and catalyst activity in enzyme catalysed extractive membrane reactors to maximise the reaction rate, production rate (membrane flux), catalyst retention and catalyst lifetime in aqueous reaction systems.
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To do this, my team of 3 PDRAs, 3 PhDs and I will develop unique stable polymer-polymer acid-nanoparticle composite membranes that can be externally electrically tuned to different pore sizes and/or molecular selectivity, uniquely tuning for neutral and charged species. We will characterise the chemical, physical and transport mechanisms responsible for the membrane tuneablity and relate these to transport models. We will then determine the feasibility of applying these unique tuneable membranes into membrane reactors, to allow in-situ external control of two key reactor parameters currently not possible: (1) Membrane fouling - membrane pore size/free volume and charge will be changed by applied potential allowing the fouling layer to be pushed off/through the membrane. (2) Precise external control of the reactant and product spectrum in the reactor by modifying species retention. By doing this, these tuneable membranes can be used to control the reaction rate, emissions and catalyst retention to maximise reaction rate and selectivity. This increases energy efficiency and emission control, helping the EU 20-20-20 environmental targets to be met. The overall impact applies beyond the action – we will be able to increase the control of membrane separations used worldwide, helping industries including food, water, healthcare and chemicals.
To do this, the hypothesis I am looking to test in TUNEMEM is: Can stable, robust and predictably tuneable conducting polymer membranes be synthesised and then applied in chemical and biochemical reactors in both aqueous and organic reaction systems to control fouling and active catalyst recovery, reaction rates, and product quality (selectivity and yield)?
Objectives: corresponding to the four work packages (WPs).
1. To develop and characterise novel ultrafiltration and nanofiltration range large acid doped PANI composite and/or mixed matrix membranes that, unlike any other membranes, can produce a predictable and repeatable change in molecular weight cut-off under external electrical stimulation for electrically neutral species that is stable over an extended period of operation in both organic and aqueous reaction systems.
2. To characterise and mathematically describe the mass transfer mechanisms and fouling of electrically tuneable membranes. This will provide the first mathematical and mechanistic description of the electrically tuneable mass transport mechanisms and fouling/removal mechanisms for these types of conducting polymer membranes compared to conventional polymer membranes.
3. To determine the feasibility of these unique tuneable membranes to control the fouling, reaction rate, and catalyst activity in homogeneous catalysed extractive membrane reactors to maximise the reaction rate, production rate (membrane flux), catalyst retention and catalyst lifetime in both organic solvent and aqueous reaction systems. With objective 4 we invent a new reactor type: ‘tuneable membrane reactors’.
4. To determine the feasibility of these unique tuneable membranes to control the fouling, reaction rate, and catalyst activity in enzyme catalysed extractive membrane reactors to maximise the reaction rate, production rate (membrane flux), catalyst retention and catalyst lifetime in aqueous reaction systems.
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1. Summary for Publication – Achievements of the Project
a) Summary of the context and overall objectives of the project (For the final period, include the conclusions of the action)
The overall aim of the project is to develop polyaniline (PANI) based membranes and characterise them for electrically tuneable membrane performance in combination with chemo-catalysed and enzymatic reaction systems . To make PANI membranes electrically conductive, these membranes are doped with acids so that non-conductive emeraldine base form of PANI can be converted to electrically conductive emeraldine salt form. The performance of these conductive membranes can be controlled by modifying the doping acid and solution composition. There are two aims of this project:
1) To study the effect different doping acids (Low and high molecular weight acids (LMAD & HMAD) and doping temperatures on the performance of PANI based membranes. The project results showed that the rate of doping of HMAD is much slower than the LMAD that could be attributed to the hindrance in diffusion of HMAD but this diffusion rate can be enhanced by increasing the temperature of doping process. This work will provide systematic information for proper selection of dopants and doping conditions and their effect of electrical tuneability
2) To study the effect of solution composition: different solvents and low molecular weight additives. Results have revealed a correlation between these additives and membrane properties: co-solvents and additives can be used to control the morphology and separation performance, including electrically tuneable selectivity, allowing these membranes to be more predictably designed. This work will detail the membrane synthesis parameters that can influence the molecular structure of membranes prepared with non-solvent induced phase inversion (NIPS) method.
b) Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far (For the final period please include an overview of the results and their exploitation and dissemination)
• Effect of polymerisation temperature
Polymerisation temperature plays a crucial role in the oxidative chemical polymerisation of PANI and it is known to influence the mechanical, chemical and electrical properties of PANI. However, the relationship between polymerisation temperature and electrical tuneability of membrane is still ambiguous. In this view, we performed a systematic study of the effect of polymerisation temperature on the properties of PANI membranes and its impact on the electrical tuneability. PANI was synthesised via chemical oxidative polymerisation at different polymerisation temperatures (5°C, 15°C and 25°C). The results showed that the lower polymerisation temperature of 5°C and 15°C formed membranes with improved mechanical properties, electrical conductivity and fewer macrovoids, compared to higher polymerisation temperatures. In terms of membrane performance and electrical tuneability, the doped PANI membranes showed the highest MWCO (> 6 KD (kilo Dalton) at zero applied potential), irrespective of polymerisation temperature. Membranes prepared from powder synthesised at 15°C showed the greatest decrease in permeance (30.8 %) and MWCO (down to 2.8 KD) under the applied potential. This may be attributed to movement of acid dopants or dopants steric position in the polymer structure that would slightly swell the polymer chains. The greater tuneability was found to be related to the membranes with relatively higher electrical conductivity. This work has been published.
• In-situ fouling control
Despite of the extensive amount of work on developing high performance membranes, fouling remains an obstacle to wide-spread of membrane technology. In view of this, an in-situ method of fouling control is desperately needed. In this work, a simple, scalable method for fabricating electrically tuneable polyaniline (PANI) composite membranes with improved fouling-resistant was developed. Composite membranes were prepared using a different loadings of extended graphite (EG), in to a mixture of PANI and poly(2-acrylamido-2-methyl-1-propanesulfonic-acid) or PAAMPSA. These membranes showed an increase in permeability and MWCO under the applied potential in the PEG cross-flow filtrations, with the 50wt% membrane showing the greatest increase at 30 V. The composite membranes successfully removed the BSA (bovine serum albumin) fouling layer when voltage was applied to the fouled membranes and showed a flux recovery ratio (FRR) of 80%. Extended cross-flow filtrations of these membranes, using PEG mixture (< 6 kD) and BSA solution, have also confirmed the membrane fouling removal and electrical tuneability. This work has been presented at IMSTEC 2017, Australia and will soon be submitted for publication.
• Effect of different acid dopants
As explained above in section (a), that doping of PANI based membranes is important for its performance and life time. Thus, it is of significant importance to study the range of parameters effect this process. In this work, we investigate for the first time the electrical tuneability of PANI membranes doped with different LMAD and HMAD and at different doping temperatures (25oC and 80oC). It was found that a greater doping level was achieved at higher doping temperatures with HMAD compared to a room temperature doping process. Moreover, the HMAD doping process at 80oC was completed in shorter time compared to 25oC. Doping with LMAD showed no difference in doping levels with temperature. Membranes synthesised with HMAD were more stable that those doped with LMAD. In terms of the electrical tuneability of the PANI membranes showed a change in permeability and MWCO under applied potential that was dependent on the acid dopant and doping temperatures. Overall, this work helps to further open a “smart” window for the production of more universally applicable electrically tuneable membranes. This work is in preparation stage for publication.
• Effect of solution composition: different solvents and low molecular weight additives
As explained above in section (a), that the change in composition of the polymer casting solution, casting conditions and/or precipitation conditions can directly influence the membrane performance. In this work, the preparation of conductive polyaniline membranes was studied to understand the effect of polymer concentration, different co-solvents, evaporation time and low molecular weight additive on the structure and interactions of PANI chains in solution form and consequently PANI-membrane material characteristics and separation performance. Results have revealed a correlation between these additives and membrane properties: co-solvents and additives can be used to control the morphology and separation performance, including electrically tuneable selectivity, allowing these membranes to be more predictably designed.
• PANI for OSN applications:
The PANI membranes were doped with two polyacids, namely poly(4-styrenesulfonic acid) (PSSA) and poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (PAMPSA), and were compared with a small acid (HCl) doped PANI membrane. The polyacid doped membranes, PANI-PSSA and PANI-PAMPSA, obtained dense structures with increased hydrophilicity due to strong intermolecular interactions between the PANI and the polyacids. Stability tests showed that the PANI-PSSA and PANI-PAMPSA were stable in a wide range of polar and nonpolar solvents, while the undoped PANI and PANI-HCl had poor stability in these solvents. The swelling degree and permeance of the doped membranes decreased with the increase of the dopant molecular weight. The PANI-PAMPSA membrane exhibited a molecular weight cut-off (MWCO) in the NF range of 400 g mol–1 in methanol and isopropanol, while the PANI-HCl and PANI-PSSA membranes were in the UF range.
In addition, the tuneability studies of the PANI-PAMPSA OSN membranes were performed with an electrically connected cross-flow filtration setup developed by our research group. During the working period we have developed stable organic solvent nanofiltration (OSN) membranes made of PANI doped with PAMPSA that are electrically conductive. These membranes overcome key issues with current tuneable membranes: molecular weight cut off (MWCO) limited to the UF-range and lack of in-filtration durability. The developed membranes were solvent stable, reusable, had a denser structure and lower MWCO. For the tuneability investigation, when applying an electrical potential (20 V) in a custom-made cross-flow membrane cell, an increase in MWCO and permeance) was observed. These results show that this simple in-situ doping method with heat treatment can produce promising and stable PANI membranes, for OSN processes in different solvents, with the distinctive feature of in-situ performance control by applying external electrical potential.
• PANI for adsorption applications:
PANI-PAMPSA adsorbent was synthesized by matrix polymerization of aniline in the presence of PAMPSA. Morphological and physicochemical properties of PANI-PAMPSA were characterized by FESEM, FTIR, XRD, nitrogen adsorption/desorption and zeta potential measurement. Adsorption properties were evaluated using Methylene blue (MB) and Rose bengal (RB) as model dyes. The results showed that PANI-PAMPSA obtained a well-defined porous structure with a specific surface area (126 m2 g−1) over 10 times larger than that of the emeraldine base PANI (PANI-EB) (12 m2 g−1). The maximum adsorption capacities were 466.5 mg g−1 for MB and 440.0 mg g−1 for RB, higher than any other PANI-based materials reported in the literature. The FTIR analysis and zeta potential measurement revealed that the adsorption mechanisms involved π-π interaction and electrostatic interaction. The adsorption kinetics were best described by a pseudo-second-order model, and the adsorption isotherms followed the Langmuir model. The thermodynamic study indicated that the adsorption was a spontaneous endothermic process. For large-scale applications, this adsorbent can be used in a combined adsorption-filtration process, or be used as adsorptive membranes. This work not only presented a promising PANI adsorbent for organic dyes, but also shed some light on the development of other conducting polymer-based adsorbents for wastewater treatment.
• Fabrication and characterization of chemically cross-linked poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (PAMPSA) PANI membranes
The produced PANI-PAMPSA membranes with ultrafiltration properties have also been chemically cross-linked using DCX (α,α′-Dichloro-p-xylene). The chemical cross-liking was chosen because it does not affect the electrical conductivity of the polyaniline backbone and the chemical bond is formed with the amine nitrogen on PANI. The imine nitrogen of polymer which is also the site for doping is not involved in the cross-linking process and therefore the conductivity is potentially retained. Results showed that the cross-linking agent successfully confer high chemical stability to the PANI PAMPSA membranes but the chemical treatment has not affected the MWCO of the membrane which remain in UF range. These chemical treated membranes have potential promising application in the concentration of liquid mixtures where common UF membranes have no chemical resistance.
• Fabrication and characterization sulfonated polyaniline membranes
Polyaniline derivatives have been extensively studied for their facile chemistry and use in various application for their easy of synthesis, thermal stability and conductivity properties. Sulfonated polyaniline (S-PANI) has been synthetized and used to prepare self-doped membranes and in this way avoiding the doping/de-doping step previously reported to fabricate tuneable membranes. Membranes have been fabricated using an established method and then further treated via chemical and thermal cross-linking. The produced S-PANI membranes showed ultrafiltration properties with a limited solvent stability (unstable in harsh polar aprotic solvents such as DMF and DMAc). Chemical cross-linking successfully improved the chemical stability of the S-PANI membranes in harsh solvents over a long period of time (up to two months) whereas thermal treatment had no effect on the fabricated membranes.
• Enzyme reaction systems benchmarked in batch with conventional membranes
Commercial nanofiltration membranes (PURAMEM and DURAMEM) based on polyimide have been tested for their performances in combination with an enzymatic reaction system: kinetic resolution of 1-phenyl ethanol using free lipase. Two membranes PS600 and D500 were used with toluene and ethyl acetate as their respective solvents. PS600 and toluene yielded better results as compared to D500 including conversions greater than 40% in all the three runs, low levels of fouling, a high stability in the reaction mixture and enzyme rejections of greater than 90% in all runs. The study demonstrated that membranes could be effectively use to retain the enzyme and reuse it in a semi-continuously operated membrane reactor.
..
a) Summary of the context and overall objectives of the project (For the final period, include the conclusions of the action)
The overall aim of the project is to develop polyaniline (PANI) based membranes and characterise them for electrically tuneable membrane performance in combination with chemo-catalysed and enzymatic reaction systems . To make PANI membranes electrically conductive, these membranes are doped with acids so that non-conductive emeraldine base form of PANI can be converted to electrically conductive emeraldine salt form. The performance of these conductive membranes can be controlled by modifying the doping acid and solution composition. There are two aims of this project:
1) To study the effect different doping acids (Low and high molecular weight acids (LMAD & HMAD) and doping temperatures on the performance of PANI based membranes. The project results showed that the rate of doping of HMAD is much slower than the LMAD that could be attributed to the hindrance in diffusion of HMAD but this diffusion rate can be enhanced by increasing the temperature of doping process. This work will provide systematic information for proper selection of dopants and doping conditions and their effect of electrical tuneability
2) To study the effect of solution composition: different solvents and low molecular weight additives. Results have revealed a correlation between these additives and membrane properties: co-solvents and additives can be used to control the morphology and separation performance, including electrically tuneable selectivity, allowing these membranes to be more predictably designed. This work will detail the membrane synthesis parameters that can influence the molecular structure of membranes prepared with non-solvent induced phase inversion (NIPS) method.
b) Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far (For the final period please include an overview of the results and their exploitation and dissemination)
• Effect of polymerisation temperature
Polymerisation temperature plays a crucial role in the oxidative chemical polymerisation of PANI and it is known to influence the mechanical, chemical and electrical properties of PANI. However, the relationship between polymerisation temperature and electrical tuneability of membrane is still ambiguous. In this view, we performed a systematic study of the effect of polymerisation temperature on the properties of PANI membranes and its impact on the electrical tuneability. PANI was synthesised via chemical oxidative polymerisation at different polymerisation temperatures (5°C, 15°C and 25°C). The results showed that the lower polymerisation temperature of 5°C and 15°C formed membranes with improved mechanical properties, electrical conductivity and fewer macrovoids, compared to higher polymerisation temperatures. In terms of membrane performance and electrical tuneability, the doped PANI membranes showed the highest MWCO (> 6 KD (kilo Dalton) at zero applied potential), irrespective of polymerisation temperature. Membranes prepared from powder synthesised at 15°C showed the greatest decrease in permeance (30.8 %) and MWCO (down to 2.8 KD) under the applied potential. This may be attributed to movement of acid dopants or dopants steric position in the polymer structure that would slightly swell the polymer chains. The greater tuneability was found to be related to the membranes with relatively higher electrical conductivity. This work has been published.
• In-situ fouling control
Despite of the extensive amount of work on developing high performance membranes, fouling remains an obstacle to wide-spread of membrane technology. In view of this, an in-situ method of fouling control is desperately needed. In this work, a simple, scalable method for fabricating electrically tuneable polyaniline (PANI) composite membranes with improved fouling-resistant was developed. Composite membranes were prepared using a different loadings of extended graphite (EG), in to a mixture of PANI and poly(2-acrylamido-2-methyl-1-propanesulfonic-acid) or PAAMPSA. These membranes showed an increase in permeability and MWCO under the applied potential in the PEG cross-flow filtrations, with the 50wt% membrane showing the greatest increase at 30 V. The composite membranes successfully removed the BSA (bovine serum albumin) fouling layer when voltage was applied to the fouled membranes and showed a flux recovery ratio (FRR) of 80%. Extended cross-flow filtrations of these membranes, using PEG mixture (< 6 kD) and BSA solution, have also confirmed the membrane fouling removal and electrical tuneability. This work has been presented at IMSTEC 2017, Australia and will soon be submitted for publication.
• Effect of different acid dopants
As explained above in section (a), that doping of PANI based membranes is important for its performance and life time. Thus, it is of significant importance to study the range of parameters effect this process. In this work, we investigate for the first time the electrical tuneability of PANI membranes doped with different LMAD and HMAD and at different doping temperatures (25oC and 80oC). It was found that a greater doping level was achieved at higher doping temperatures with HMAD compared to a room temperature doping process. Moreover, the HMAD doping process at 80oC was completed in shorter time compared to 25oC. Doping with LMAD showed no difference in doping levels with temperature. Membranes synthesised with HMAD were more stable that those doped with LMAD. In terms of the electrical tuneability of the PANI membranes showed a change in permeability and MWCO under applied potential that was dependent on the acid dopant and doping temperatures. Overall, this work helps to further open a “smart” window for the production of more universally applicable electrically tuneable membranes. This work is in preparation stage for publication.
• Effect of solution composition: different solvents and low molecular weight additives
As explained above in section (a), that the change in composition of the polymer casting solution, casting conditions and/or precipitation conditions can directly influence the membrane performance. In this work, the preparation of conductive polyaniline membranes was studied to understand the effect of polymer concentration, different co-solvents, evaporation time and low molecular weight additive on the structure and interactions of PANI chains in solution form and consequently PANI-membrane material characteristics and separation performance. Results have revealed a correlation between these additives and membrane properties: co-solvents and additives can be used to control the morphology and separation performance, including electrically tuneable selectivity, allowing these membranes to be more predictably designed.
• PANI for OSN applications:
The PANI membranes were doped with two polyacids, namely poly(4-styrenesulfonic acid) (PSSA) and poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (PAMPSA), and were compared with a small acid (HCl) doped PANI membrane. The polyacid doped membranes, PANI-PSSA and PANI-PAMPSA, obtained dense structures with increased hydrophilicity due to strong intermolecular interactions between the PANI and the polyacids. Stability tests showed that the PANI-PSSA and PANI-PAMPSA were stable in a wide range of polar and nonpolar solvents, while the undoped PANI and PANI-HCl had poor stability in these solvents. The swelling degree and permeance of the doped membranes decreased with the increase of the dopant molecular weight. The PANI-PAMPSA membrane exhibited a molecular weight cut-off (MWCO) in the NF range of 400 g mol–1 in methanol and isopropanol, while the PANI-HCl and PANI-PSSA membranes were in the UF range.
In addition, the tuneability studies of the PANI-PAMPSA OSN membranes were performed with an electrically connected cross-flow filtration setup developed by our research group. During the working period we have developed stable organic solvent nanofiltration (OSN) membranes made of PANI doped with PAMPSA that are electrically conductive. These membranes overcome key issues with current tuneable membranes: molecular weight cut off (MWCO) limited to the UF-range and lack of in-filtration durability. The developed membranes were solvent stable, reusable, had a denser structure and lower MWCO. For the tuneability investigation, when applying an electrical potential (20 V) in a custom-made cross-flow membrane cell, an increase in MWCO and permeance) was observed. These results show that this simple in-situ doping method with heat treatment can produce promising and stable PANI membranes, for OSN processes in different solvents, with the distinctive feature of in-situ performance control by applying external electrical potential.
• PANI for adsorption applications:
PANI-PAMPSA adsorbent was synthesized by matrix polymerization of aniline in the presence of PAMPSA. Morphological and physicochemical properties of PANI-PAMPSA were characterized by FESEM, FTIR, XRD, nitrogen adsorption/desorption and zeta potential measurement. Adsorption properties were evaluated using Methylene blue (MB) and Rose bengal (RB) as model dyes. The results showed that PANI-PAMPSA obtained a well-defined porous structure with a specific surface area (126 m2 g−1) over 10 times larger than that of the emeraldine base PANI (PANI-EB) (12 m2 g−1). The maximum adsorption capacities were 466.5 mg g−1 for MB and 440.0 mg g−1 for RB, higher than any other PANI-based materials reported in the literature. The FTIR analysis and zeta potential measurement revealed that the adsorption mechanisms involved π-π interaction and electrostatic interaction. The adsorption kinetics were best described by a pseudo-second-order model, and the adsorption isotherms followed the Langmuir model. The thermodynamic study indicated that the adsorption was a spontaneous endothermic process. For large-scale applications, this adsorbent can be used in a combined adsorption-filtration process, or be used as adsorptive membranes. This work not only presented a promising PANI adsorbent for organic dyes, but also shed some light on the development of other conducting polymer-based adsorbents for wastewater treatment.
• Fabrication and characterization of chemically cross-linked poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (PAMPSA) PANI membranes
The produced PANI-PAMPSA membranes with ultrafiltration properties have also been chemically cross-linked using DCX (α,α′-Dichloro-p-xylene). The chemical cross-liking was chosen because it does not affect the electrical conductivity of the polyaniline backbone and the chemical bond is formed with the amine nitrogen on PANI. The imine nitrogen of polymer which is also the site for doping is not involved in the cross-linking process and therefore the conductivity is potentially retained. Results showed that the cross-linking agent successfully confer high chemical stability to the PANI PAMPSA membranes but the chemical treatment has not affected the MWCO of the membrane which remain in UF range. These chemical treated membranes have potential promising application in the concentration of liquid mixtures where common UF membranes have no chemical resistance.
• Fabrication and characterization sulfonated polyaniline membranes
Polyaniline derivatives have been extensively studied for their facile chemistry and use in various application for their easy of synthesis, thermal stability and conductivity properties. Sulfonated polyaniline (S-PANI) has been synthetized and used to prepare self-doped membranes and in this way avoiding the doping/de-doping step previously reported to fabricate tuneable membranes. Membranes have been fabricated using an established method and then further treated via chemical and thermal cross-linking. The produced S-PANI membranes showed ultrafiltration properties with a limited solvent stability (unstable in harsh polar aprotic solvents such as DMF and DMAc). Chemical cross-linking successfully improved the chemical stability of the S-PANI membranes in harsh solvents over a long period of time (up to two months) whereas thermal treatment had no effect on the fabricated membranes.
• Enzyme reaction systems benchmarked in batch with conventional membranes
Commercial nanofiltration membranes (PURAMEM and DURAMEM) based on polyimide have been tested for their performances in combination with an enzymatic reaction system: kinetic resolution of 1-phenyl ethanol using free lipase. Two membranes PS600 and D500 were used with toluene and ethyl acetate as their respective solvents. PS600 and toluene yielded better results as compared to D500 including conversions greater than 40% in all the three runs, low levels of fouling, a high stability in the reaction mixture and enzyme rejections of greater than 90% in all runs. The study demonstrated that membranes could be effectively use to retain the enzyme and reuse it in a semi-continuously operated membrane reactor.
..
Progress beyond the state of the art and expected results until the end of the project
The development of electrically conductive membranes with in-situ control of fouling will seed a pathway and platform for the UK to be the world leader in the new paradigm of finely controlled mass transfer smart membranes for a range of chemical industries ranging from food, pharmaceuticals to chemical processing industries. This work will bring a unique prospective of membrane based separations. The in-situ control of fouling using just electrical potential, without the need for chemicals, make this project a sustainable and cheap method to clean membranes.
In addition, the project demonstrates that polyacid doping can make stable and nanoporous PANI membranes for OSN applications without the need for crosslinking. This simple approach can be used to design new classes of OSN membranes for challenging separation processes.
Secondly, a polyacid doped PANI adsorbent PANI-PAMPSA was used for dye removal for the first time. To our knowledge, PANI-PAMPSA has higher adsorption capacities than any other PANI-based materials, and is among the most effective adsorbents for dye removal (such as commercial activated carbon and chitosan). The convenient synthesis and the high adsorption capacity make PANI-PAMPSA a promising adsorbent material for wastewater treatment.
..
The development of electrically conductive membranes with in-situ control of fouling will seed a pathway and platform for the UK to be the world leader in the new paradigm of finely controlled mass transfer smart membranes for a range of chemical industries ranging from food, pharmaceuticals to chemical processing industries. This work will bring a unique prospective of membrane based separations. The in-situ control of fouling using just electrical potential, without the need for chemicals, make this project a sustainable and cheap method to clean membranes.
In addition, the project demonstrates that polyacid doping can make stable and nanoporous PANI membranes for OSN applications without the need for crosslinking. This simple approach can be used to design new classes of OSN membranes for challenging separation processes.
Secondly, a polyacid doped PANI adsorbent PANI-PAMPSA was used for dye removal for the first time. To our knowledge, PANI-PAMPSA has higher adsorption capacities than any other PANI-based materials, and is among the most effective adsorbents for dye removal (such as commercial activated carbon and chitosan). The convenient synthesis and the high adsorption capacity make PANI-PAMPSA a promising adsorbent material for wastewater treatment.
..