Innovative strategies for enhancing gas separation: Ionic liquid-coated PES membranes for improved CO2/N2 selectivity and permeance

As a cost-effective advancement in membrane technology, this study investigates the impact of PEG additive and CBT on the structural, stability, and gas permeance properties of PES-coated membranes, utilizing 1-dodecyl-3-methylimidazolium chloride ionic liquid ([DDMI][Cl] IL) as a carrier liquid. BET and FT-IR analyses highlight the significant enhancement in performance through the immobilization of pores with [DDMIM][Cl] IL. The investigation focuses on PES-M5-coated membranes, revealing excellent stability in finger-like pore structures prepared through direct immersion and nitrogen pressure immobilization. PES-M5-coated membranes with [DDMIM][Cl] IL via direct immersion experience lower weight loss than those coated using nitrogen pressure, with critical pressures at 1.4 and 1.25 bar, respectively. The study identifies PES-coated membranes, particularly PES-M25 (20.88 GPU) with macro-void pores and PES-M5 (29 GPU) with finger-like pores, exhibiting the highest CO2 permeance and CO2/N2 selectivity. As a cost-effective advancement in membrane technology, ionic liquids are employed in support membranes to enhance gas separation. Employing pure PES membranes with varying pore structures, created through the NIPS method, the study immobilizes [DDMI][Cl] IL in membrane pores through nitrogen pressure and direct immersion. Results underscore the successful application of porous support materials coated with ionic liquids for continuous CO2 and sulfur compound separation, showcasing competitive permeability and selectivity compared to traditional polymer membranes.

Development of Novel Electrospun Fibers Based on Cyclic Olefin Polymer

For the first time, a systematic study to investigate the electrospinnability of cyclic olefin polymer (COP) was performed. Different solvents and mixtures were tested together with different electrospinning parameters and post-treatment types to prepare bead-free fibers without defects. These were successfully obtained using a chloroform/chlorobenzene (40/60 wt.%) solvent mixture with a 15 wt.% COP polymer, a 1 mL/h polymer solution flow rate, a 15 cm distance between the needle and collector, and a 12 kV electric voltage. COP fibers were in the micron range and the hot-press post-treatment (5 MPa, 5 min and 120 °C) induced an integrated fibrous structure along with more junctions between fibers, reducing the mean and maximum inter-fiber space. When the temperature of the press post-treatment was increased (from 25 °C to 120 °C), better strength and less elongation at break of COP fibers were achieved. However, when applying a temperature above the COP glass temperature (Tg = 138 °C) the fibers coalesced, showing a mechanical behavior similar to a plastic film and a low elongation at break with a high strength. The addition of a high dielectric constant non-solvent, N,N-dimethylacetamide (DMAc), resulted in a considerable reduction in the COP fiber diameter. Based on the cloud point approach, it was found that the use of DMAc and the solvent chloroform or chlorobenzene improved the electrospinnability of COP polymer solution.

Design and optimization of a hybrid process based on hollow-fiber membrane/coagulation for wastewater treatment

Treatment of textile wastewater using ultrafiltration membranes was carried out in this study. Since membrane fouling is a major operational problem that decreases the membrane separation efficiency, wastewater was treated with polyaluminum chloride (PACl) and alum (aluminum sulfate) as coagulant to decrease the fouling of ultrafiltration membranes. PACl was selected as the best coagulant in the experiments. Also, chitosan was used as coagulant aid upon developing the hybrid process. The obtained optimum dosage of PACl coagulant was 100 mg/L, and maximum turbidity and COD removal of 35% and 66% were attained, respectively. The pretreated wastewater by coagulation was sent to ultrafiltration process for further removal of turbidity and COD. Three ultrafiltration hollow-fiber membranes made of polypropylene (PP), polyvinylidene fluoride (PVDF), and polyethersulfone (PES) were applied in this study. In general, the filtration results were evaluated for two types of samples treated under coagulation and without treatment; the results were unfavorable for the second type. The effects of transmembrane pressure (TMP) and cross velocity on membranes performance were also investigated for process optimization. The obtained results showed that PVDF membrane had the highest flux and turbidity removal, whereas the PES membrane had the highest COD removal. Also, the results revealed that turbidity and COD removal by all membranes were decreased by increasing TMP and cross velocity.

INVESTIGATION OF MECHANICAL, THERMAL, AND MORPHOLOGICAL PROPERTIES OF EPDM COMPOUNDS CONTAINING RECLAIMED RUBBER

The disposal of polymeric and hazardous materials is an important global issue. Thus, the mechanochemical reclaiming of waste EPDM rubber was carried out using disulfide oil (DSO), oily waste produced in gas refineries, as a reclaiming agent at a specific operation condition. Reclaimed rubber was characterized by crosslink density, sol-gel, and Mooney viscosity measurements. Following the study, blending of different portions of reclaimed rubber (20, 40, 60, and 80 wt%) with virgin EPDM rubber was carried out. Results showed that the addition of 60 wt% of reclaimed rubber to the virgin EPDM rubber had no adverse effect on the scorch and optimum curing time. Also, mechanical properties of revulcanized rubber improved when 40 wt% of virgin EPDM rubber was replaced with the reclaimed rubber. Scanning electron microscope and thermal gravimetric analyses of the samples revealed the effect of addition of reclaimed rubber on the rubber matrix and thermal stability of revulcanized samples, respectively. This study proposes a new route for solving the problem of disposal of the waste materials.

Synthesis, characterization and gas separation properties of novel copolyimide membranes based on flexible etheric–aliphatic moieties

The structural properties and gas permeation of a group of copolyimide membranes were investigated.