C.T.S.G. Alembic

The separation of salts from aqueous solutions is a critical process in various industrial applications, including water treatment and chemical production. Traditional methods like reverse osmosis cannot reach saturation level of the salt, and result in the rejection of streams with high salt concentrations to the sea, prompting the search for more sustainable and efficient alternatives. We have found that thermoresponsive polymers offer a promising solution due to their ability to undergo phase transitions at specific temperatures, enabling the extraction of water from aqueous salt solutions at lower temperature, and recovery of the polymer by phase splitting at higher temperature. Essentially, such liquid-liquid extraction (LLX) with thermally induced phase splitting (TIPS) may offer regeneration at mild temperature swings that may be reached with heat pumps, thus offering separation and recovery of water and salts with lower energy requirements.

We aim to use polymers with a lower critical solution temperature (LCST)—the critical temperature below which the components of a mixture are miscible for all compositions. Combined with aqueous salt solutions, they do split in two phases: a salt-rich phase and a polymer-rich phase, and water is transferred to the polymer-rich phase. After splitting the salt-rich phase and the polymer-rich phase, the polymer is recovered by increasing the temperature to above the LCST, so that a new phase split is realized. What we need to further investigate in such TIPS is how we can obtain clean water, free of polymer. For this, we need to closely examine the liquid-liquid equilibria at multiple temperatures, and measure how much polymer is still in the water phase, and how much water is in the polymer phase.

This project focuses on the experimental investigation of thermally induced phase splitting (TIPS) for polymer recovery. The aim is to understand the phase behavior of various polymer-salt-water mixtures at different temperatures, and to investigate the usefulness of the Non-Random Two-Liquid (NRTL) model and if needed more complex models (polymer-NRTL and/or polymer-electrolyte-NRTL) or even another model to describe the phase behavior observed in these systems.

Assignment

The assignment includes experimental work and theoretical modeling to study the TIPS process. The main tasks are outlined below:

• Conduct a literature review on thermoresponsive polymers, their applications in liquid-liquid extraction (LLX), and the mechanisms of thermally induced phase splitting (TIPS).
• Perform thermally induced phase splitting experiments at multiple temperatures using polymer rich phases obtained from LLX, assessing the efficiency of temperature swings in polymer recovery.
• Analyze the experimental results and model the phase behavior design a practical TIPS process.
• Compile all research findings into a comprehensive report summarizing experimental methods, results, and analysis of TIPS for polymer recovery.
• Prepare a colloquium presentation summarizing the project outcomes, challenges faced, and future research recommendations based on the findings.

Contact info:​​​​​​​

Supervision:
Prof. dr. ir. Boelo Schuur - B.schuur@utwente.nl
​​​​​​​Prof. dr. ir. Gerrald Bargeman

Daily supervisor:
Gabriela Pulido / PhD student