High performance and commercially attractive mixed-matrix membranes were developed for H₂/CO₂ separation via a scalable hollow fiber spinning process. Thin (~300 nm) and defect-free selective layers were successfully created with a uniform distribution of the nanosized (~60 nm) zeolitic-imidazole framework (ZIF-8) filler within the polymer (polybenzimidazole, PBI) matrix. These membranes were able to operate at high temperature (150 °C) and pressure (up to 30 bar) process conditions required in treatment of pre-combustion and syngas process gas streams. Compared with neat PBI hollow fibers, filler incorporation into the polymer matrix leads to a strong increase in H₂ permeance from 65 GPU to 107 GPU at 150 °C and 7 bar, while the ideal H₂/CO₂ selectivity remained constant at 18. For mixed gas permeation, there is competition between H₂ and CO₂ transport inside ZIF-8 structure. Adsorption of CO₂ in the nanocavities of the filler suppresses the transport of the faster permeating H₂ and consequently decreases the H₂ permeance with total feed pressure down to values equal to the pure PBI hollow fibers for the end pressure of 30 bar. Therefore, the improvement of fiber performance for gas separation with filler addition is compromised at high operating feed pressures, which emphasizes the importance of membrane evaluation under relevant process conditions.

The strong saline water intrusion in the North Branch of the Yangtze Estuary threatens the freshwater supply of the region in winter half year. Strong northerly winds have been identified as a factor increasing saline water intrusion. However, there are few studies on this subject, and the mechanisms of winds influencing saline water intrusion are still unclear. In the present contribution, we investigate the variation trend of strong wind events during cold outbreaks in winter half year and their correlation with saline water intrusion in the North Branch, together with the processes and mechanism of strong winds increasing saline water intrusion, based on observations and an analytical salt water intrusion model. The results indicate that the strong northerly and northeasterly wind events and saline water intrusion in the North Branch have similar variation trends in 1994–2008, both being relatively weak in the 1990s but being intensified dramatically after 1999. The significant correlation between these two trends suggests that the increase in strong wind events may be one of the factors inducing the enhanced saline water intrusion. Observations and model output show that the strong northerly and northeasterly winds can induce dramatic water level setup, increase of flood-tide current velocities, decrease of ebb-tide velocities, and decrease of freshwater inflow into the North Branch. These changes in combination cause the enhanced intensity of saline water intrusion. The Ekman transport from remote winds results in water level setup at the estuary mouth pumping more seawater into the North Branch, which should be a dominant mechanism inducing the change in hydrodynamics and increase of saline water intrusion.

The preparation and performance of mixed matrix membranes (MMMs) based on polybenzimidazole (PBI) and ZIF-8 nanoparticles of different average sizes (50, 70 and 150 nm) as filler are reported. MMMs containing 10 and 20 wt% of ZIF-8 were tested for H₂/CO₂ separation (pre-combustion CO₂ capture) at 150 °C and feed pressures from 3 to 6 bar. The addition of ZIF-8 resulted in a clear improvement in membrane performance. Embedding 20 wt% of ZIF-8 resulted in a H₂ permeability increase of six times and the H₂/CO₂ selectivity increased nearly by 55% compared to the bare PBI polymer membrane. Both permeability and selectivity improved as the filler size increased, due to the lower degree of agglomeration of the largest particles, that may be less active owing to their smaller external surface area. MMMs synthesized using dry 150 nm ZIF-8 filler showed a better performance than those containing wet filler. Apart from agglomeration concerns favoring wet filler handling as evidenced by infrared characterization, the MMM preparation with wet filler is simpler than with dry filler. Finally, the reproducibility of the membranes was confirmed by a European interlaboratory Round Robin test involving three different institutions.