Study of CO2 adsorption onto poly(1–vinylimidazole) using quartz crystal microbalance and density functional theory methods

Technological advancements in the use of ionic liquid- membrane systems for CO2 capture from biogas/flue gas - A review

Carbon capture has become a very important method for curbing the problems associated with the release of carbon dioxide into the atmosphere, which in turn has detrimental effects on the planet and its inhabitants. Ionic liquids and membrane separation have been explored in this review paper as effective means of capturing carbon dioxide. An innovative approach to CO₂ capture is the use of Ionic liquids (ILs) since they exhibit certain significant traits such as good stability (thermal, mechanical and chemical), inflammability and high absorptive capacities. Ionic liquids (ILs) are widely regarded as nontoxic substances. Viscosity and thermal degradation of ILs at temperatures slightly above 100 °C are the major disadvantages of ILs. Membrane separation is a technique used for the effective separation of substances by materials bearing holes in a continuous structure. Membrane technology has gained significant improvements, over the years. Several ILs and membrane systems were considered in this work. Their weaknesses, strengths, permeability, selectivity, operating conditions and carbon capture efficiencies, were all highlighted in order to gain a good perspective on ways by which the individual systems can be improved upon. The study considered several polymer-Ionic liquid hybrid materials as viable options for CO₂ capture from a post-combustion process. Different ILs were scrutinized for possible integration in membranes by taking full advantage of their individual properties and harnessing their tune-able characteristics in order to improve the overall carbon capture performance of the system. Several options for improving the mechanical, chemical, and thermal stabilities of the hybrid systems were considered including the use of cellulose acetate membrane, nanoparticles (graphene oxide powder) alongside potential ionic liquids. Doping membranes with ILs and nanoparticulates such as graphene oxide serves as a potential method for enhancing the CO₂ capture of membranes and this review provides several evidences that serve as proofs for this concept.

Measurement of isosteric heat of gas adsorption and Brunauer-Emmett-Teller (BET) surface area using a quartz crystal microbalance

The study of gas adsorption on a solid surface evaluates the affinity between sorbate gas and sorbent substrate and factors that contribute to this. This paper presents a test platform for adsorption experiments of various gases on various solid surfaces. Controlled environmental conditions enable investigations in materials surface science and increase the consistency among adsorption data. The system utilizes a quartz crystal microbalance to perform gravimetric analysis of deposition and adsorption, enabling investigation of the interaction of gaseous molecules with solid surfaces. In this study, a quartz crystal microbalance as gas adsorption detector was integrated with an environmental chamber to create a versatile tool for gas adsorption experiments on thin films. Experimental operation of this apparatus was demonstrated via acquisition of the adsorption isotherms of cyclohexane vapor on a gold surface at 55 and 70 °C. The result indicated International Union of Pure and Applied Chemistry Type II adsorption. Consequentially, application of the Brunauer-Emmett-Teller model to the isotherm data subject to predefined criteria for linear region selection yielded a surface area of the sorbent of 0.53 cm² at 55 °C. From the monolayer region of the isotherms, the isosteric heat of adsorption of the cyclohexane vapor on gold was calculated to be 37 kJ mol^-1.

Carbon dioxide adsorption onto modified polyvinyl chloride with ionic liquid

To modify polyvinylchloride membranes for carbon dioxide gas separation, six polyvinyl chloride-g-polyionic liquid ionomers such as polyvinylchloride-g-poly1-vinyl-3-hexylimidazolium bromide (PVC-g-P[VHIm][Br]), polyvinylchloride-g-poly1-vinyl-3-hexylimidazolium thiocyanate (PVC-g-P[VHIm][SCN]), polyvinylchloride-g-poly1-vinyl-3-hexylimidazolium tetrafluoroborate (PVC-g-P[VHIm][ BF4]), polyvinylchloride-g-poly1-vinyl-3-octylimidazolium bromide (PVC-g-P[VOIm][Br]), polyvinylchloride-g-poly1-vinyl-3-octylimidazolium thiocyanate (PVC-g-P[VOIm][SCN]) and polyvinylchloride-g-poly1-vinyl-3-octylimidazolium tetrafluoroborate (PVC-g-P[VOIm][ BF4]) were synthesized. The polyvinyl chloride-g-polyionic liquid ionomers were characterized using elemental analyzer (CHN) and Fourier transform infrared spectroscopy (FTIR) techniques. CO2 adsorption onto these ionomers was measured by quartz crystal microbalance (QCM) and the experimental data were correlated by the sorption model. The parameters obtained imply that CO2 adsorption has an exothermic and physisorption nature. Also, the investigations point to that the PVC-g-P[VHIm][SCN] has better performance for CO2 separation.

Obtainment and Characterization of Hydrophilic Polysulfone Membranes by N-Vinylimidazole Grafting Induced by Gamma Irradiation

Polysulfone (PSU) film and N-vinylimidazole (VIM) were used to obtain grafted membranes with high hydrophilic capacity. The grafting process was performed by gamma irradiation under two experiments: (1) different irradiation doses (100-400 kGy) and VIM 50% solution; (2) different concentration of grafted VIM (30-70%) and 300 kGy of irradiation dose. Characteristics of the grafted membranes were determined by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), contact angle, swelling degree, desalination test, thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Both experiments indicated that the absorbed dose 300 kGy and the VIM concentration, at 50% v/v, were effective to obtain PSU grafted membranes with 14.3% of grafting yield. Nevertheless, experimental conditions, 400 kGy, VIM 50% and 300 kGy, VIM 60-70% promoted possible membrane degradation and VIM homopolymerization on the membrane surface, which was observed by SEM images; meanwhile, 100-200 kGy and VIM 30-50% produced minimal grafting (2 ± 0.5%). Hydrophilic surface of the grafted PSU membranes by 300 kGy and VIM 50% v/v were corroborated by the water contact angle, swelling degree and desalination test, showing a decrease from 90.7° ± 0.3 (PSU film) to 64.3° ± 0.5; an increment of swelling degree of 25 ± 1%, and a rejection-permeation capacity of 75 ± 2%. In addition, the thermal behavior of grafted PSU membranes registered an increment in the degradation of 20%, due to the presence of VIM. However, the normal temperature of the membrane operation did not affect this result; meanwhile, the glass transition temperature (T_g) of the grafted PSU membrane was found at 185.4 ± 0.5 °C, which indicated an increment of 15 ± 1%.