Polymers with high permeability and strong size-sieving ability are needed for H2/CO2 separation at temperatures ranging from 100 to 300 °C to enable an energy-efficient precombustion CO2 capture process. However, such polymers usually suffer from a permeability/selectivity tradeoff, that is, polymers with high permeability tend to exhibit a weak size-sieving ability and thus low selectivity. Herein, we demonstrate that carbonization of a suitable polymer precursor (i.e., polybenzimidazole or PBI) generates microcavities (leading to high H2 permeability) and ultramicroporous channels (leading to strong size-sieving ability and thus high H2/CO2 selectivity). Specifically, carbonization of PBI at 900 °C (CMS@900) doubles H2 permeability and increases H2/CO2 selectivity from 14 to 80 at 150 °C. When tested with simulated syngas-containing equimolar H2 and CO2 in the presence of water vapor for 120 h, CMS@900 exhibits stable H2 permeability of ≈36 barrer and H2/CO2 selectivity of ≈53 at 150 °C, above Robeson’s 2008 upper bound and demonstrating robustness against physical aging and CO2 plasticization.

Polymers with a strong size-sieving ability and superior H2/CO2 selectivity are of great interests for pre-combustion CO capture at 100 °C or above. Polyimides (such as Matrimid® and 6FDA-durene) have been cross-linked using diamines and show superior H2/CO2 selectivity. However, these cross-linked polymers cannot be used for the pre-combustion CO2 capture because of the lack of thermal stability at 100 C. Herein we demonstrate that commercial P84™ can be chemically cross-linked using 1,4-butanediamine (BuDA) to achieve robust H2/CO2 separation properties at 100 °C to 150 °C. The cross-linked P84 were thoroughly evaluated using Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). The effects of the cross-linking time on the physical properties and H2/CO2 separation properties at various temperatures were determined and interpreted using a free volume model. An exemplary sample based on P84 crosslinked by BuDA for 6 h exhibits a H2 permeability of 47 Barrers (1 Barrer = 3.35 × 10−16 mol m/m2·s·Pa) and H2/CO2 selectivity of 14 at 100 °C, which is on the Robeson’s upper bound, indicating their potential for practical applications.

Asymmetric polyethersulfone (PES) nanofiltration membranes were prepared via phase inversion technique. PES polymer, Brij 58 as surfactant additive, polyvinylpyrrolidone (PVP) as pore former and 1-methyl-2-pyrrolidone (NMP) as solvent were used in preparation of the casting solutions. Distillated water was used as the gelation media. The scanning electron microscopy (SEM) images and measurements of contact angle (CA) and zeta potential were used to characterize the prepared membranes. Also performance of the membranes was examined by determining the pure water flux (PWF) and pharmaceuticals rejection. The addition of Brij 58 to the casting solution resulted in formation of the membranes with higher thickness and more porous structure in the sublayer in comparison with the net PES membrane. The surface hydrophilicity of the membranes was remarkably enhanced via the presence of Brij 58 in the casting solution, so that, the contact angel diminished from 74.7° to 28.3° with adding 6 wt. % of Brij 58 to the casting solution. The addition of Brij 58 to the casting solution resulted in formation of the membranes with superior PWF and higher rejection of amoxicillin and ceftriaxone in comparison with the pure PES membrane.

No abstract

Nowadays, antibiotics such as amoxicillin have been entered in water bodies. Nanofiltration has been proposed as an attractive technology for removal of antibiotics from aquatic environment instead of conventional wastewater treatment. In this paper, novel asymmetric flat sheet nanofiltration membranes were prepared via immersion precipitation technique and by using the poly(ethersulfone)/Brij®S100/Poly(vinylpirrolidone)/1-methyl-2-pyrolidone casting solutions. The effect of addition of Brij®S100 as a non-ionic surfactant additive as well as concentration of poly (ethersulfone) on morphology, wettability, pure water flux and rejection of amoxicillin were studied using the scanning electron microscopy, water contact angle apparatus and experimental set-up. The results indicated that the addition of Brij®S100 to the casting solutions resulted in the formation of membranes with higher hydrophilicity and relatively noticeable rejection of amoxicillin up to 99% in comparison with unmodified poly(ethersulfone) membrane. Contrary to amoxicillin rejection, pure water flux was decreased when higher poly(ethersulfone) concentration was employed.