Report

Teaser, summary, work performed and final results

Periodic Reporting for period 2 - TUNEMEM (Externally Tuneable Separations for Membrane Reactors)

Teaser

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...

Summary

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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Work performed

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 memb

Final results

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.

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Website & more info

More info: http://www.darrellpattersongroup.com/TUNMEM.html.