Effects of Pore Additives on Deep Eutectic Solvent Immobilization for CO₂/N₂ Gas Separation Using Supported Deep Eutectic Solvent Membranes

Abstract

This work analyses the effect of two different pore additives focusing on polyethylene glycol (PEG) and lithium chloride (LiCl) at different concentrations on the immobilization of a deep eutectic solvent (DES) in a polyvinylidene fluoride-co-polytetrafluoroethylene (PVDF-co-PTFE) membrane. Two compounds were chosen to synthesized the DES; choline chloride as halide salt and ethylene glycol as a hydrogen bond donor.  The DES was impregnated onto the membrane pores by applying a vacuum-based technique. The membranes were prepared via phase inversion by means of immersion precipitation. For characterization purposes, scanning electron microscopy (SEM-EDX) was used to analyse the morphology of the supported- DES-membranes together with energy dispersive X-ray spectrometry. The gravimetric method was applied to calculate the porosity, while the membrane performance for carbon dioxide (CO₂) permeation and separation was assessed to determine the capability of the DES-impregnated membrane. The outcomes demonstrating that the highest loading of DES in the membrane support was obtained when 3 wt% PEG was added into the polymer solution with a porosity of 70.5%. The CO₂ permeability and the CO₂/N₂ selectivity achieved using the synthesized membrane are 2.81 x 10⁶ barrer and 3.46, respectively, when working with a transmembrane pressure of 1.1 bar and a temperature of 25ᵒC at 200 cm³ /min of gas flow rate. The results showed that additional of PEG as a pore additives able to load the highest DES in the membrane pore and resulted the best CO₂ permeability and the CO₂/N₂ selectivity.