Extraction of Bio-based Organic Acids using Supported Liquid Membranes with Novel Solvents

Student thesis: Phd


Novel green solvents and supported liquid membranes were studied for the recovery of bio-based organic acids from model fermentation broths. As fundamental building blocks for the chemical industry, the production of organic acids from renewable feedstock have been broadly developed. Among them, succinic acid, levulinic acid, and fumaric acid have been highlighted as leading representatives. Nevertheless, their downstream separation and purification still require further research to build a suitable green production route. This turns the development of environmentally-friendly extractants as well as efficient separation methods into priority key research areas for bio-separations. The growing number of available green solvents, such as ionic liquids, eutectic solvents, and bio-based solvents, makes unbearable the experimental screening process to find the most appropriate extractant. In this work, the molecular interactions driving the overall extraction performance for the organic acids were systematically analysed. Experimental measurements of the liquid-liquid extraction and solid-liquid equilibria, as well as thermodynamic modelling using the quantum chemistry-based COSMO-RS method, were carried out. Organic acids extraction yields and solubilities, systems excess energies, activity coefficients, and energies of solutions are reported. The combination of structurally different acids and extraction solvents arise complex interactions; however, hydrogen bonding showed to determine the overall behaviour. As a result, a straightforward selection guide was developed based on the organic acids partition coefficients in the extractant/water system, ln(K), system's water affinity, ln(y), and separation process spontaneity, G. Furthermore, the dissolution process of the organic acids in green solvents displayed an endothermic and spontaneous process with an enthalpy-entropy compensation effect. The separation is driven by the new and stronger interactions formed, increasing the order of the systems. The state-of-the-art on sustainable applications of liquid membrane technology was thoroughly reviewed. Despite its high potential to replace conventional liquid-liquid extraction processes, some operational issues must be overcome and better predictive models developed. The feasibility of green-supported liquid membranes for succinic acid recovery was explored. As suggested by previous results, the solvent-phase affinities became key in the extraction performance. Experimental extractions were carried out to assess the effect of the green solvents and receiving phase. Commercial polyvinylidene fluoride (PVDF) porous membranes were impregnated with four different green solvents: the eutectic solvents DL-menthol:OctA and N4444Cl:OctA, the bio-based solvents eucalyptol, and the ionic liquid [C4pyrr][Tf2N]. The acid recovery for all liquid membranes was 50%, 51% and 59% with pure water and alkaline aqueous solutions of 0.1M and 0.5M NaOH in the stripping phase, respectively. It was found that extraction yield indeed depends on the pH of the stripping phase and that the solute permeation rate depends on the extraction solvent. For the first time, a permeability model based on experimental data and activity coefficients computed using the COSMO-RS method was developed. Moreover, the novel Permeability Activity-Based Linear Operation (PABLO) method was developed and proposed to determine the theoretical stages number and mass transfer area in a countercurrent cascade extraction system. Overall, this thesis comprehensively covers two research needs for the bioseparations of key building blocks. The contributions will certainly enhance the development and design of green production routes, boosting the next generation of sustainable chemicals and biorefinery industries.
Date of Award1 Aug 2023
Original languageEnglish
Awarding Institution
  • The University of Manchester
SupervisorPatricia Gorgojo (Supervisor), Maria Gonzalez Miquel (Supervisor) & Aurora J. Cruz-Cabeza (Supervisor)


  • Eutectic solvent
  • Ionic liquid
  • Process design
  • Biorefinery
  • Organic acid
  • Green solvent
  • Supported liquid membrane

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