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In this work, we reported a nitrogen-doped porous carbon (NPC) that was prepared from waste polyurethane (PU) foams through hydrothermal carbonization and further activation. The possible reactions occurred during the hydrothermal carbonation and activation process of waste PU were proposed based on the results of gas chromatography–mass spectrometry and thermogravimetric Fourier transform infrared. Hydrothermal carbonization significantly improved the porous structure and surface N-containing active groups on carbon. The specific surface area and the total pore volume were obtained at 1419 m2/g and 0.80 cm3/g, respectively, for porous carbon prepared under 200 °C for 6 h, which were much higher than those without hydrothermal carbonization (1100 m2/g and 0.66 cm3/g). Moreover, the nitrogen contents on the porous carbon increased from 1.4 to 2.8 wt % with the majority of pyridinic and pyrrolic N species. The saturated sulfur capacity of NPC reached as high as 205.06 mg/g, which was almost 2.5 times higher than that without hydrothermal carbonization. The desulfurization performance could be tightly related to the hierarchical porous structure and active nitrogen species on the carbon induced by hydrothermal carbonization/catalysis. Thus, our current efforts provide a facile strategy for the preparation of porous adsorbent for H2S removal with the low cost and high efficiency.

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Developing a membrane material with both high CO2 permeability and high CO2/N2 selectivity is always desired for CO2 capture, while improving the sustainability of the membrane preparation process is of equal importance. In the current work, a nanocellulose crystal (CNC) was blended with hydrophilic Pebax 1657 for CO2 separation application. The CO2/N2 separation performance of Pebax 1657/CNC hybrid membranes with up to 40 wt % CNC was evaluated by mixed-gas permeation tests under both dry and humid conditions. The humid test condition simultaneously increases CO2 permeability and CO2/N2 selectivity of all CNC/Pebax hybrid membranes compared to those under dry conditions. Introduction of only 5 wt % CNC into Pebax 1657 realizes 42 and 18% increments in CO2 permeability (305.7 Barrer) and CO2/N2 selectivity (41.6), respectively. However, further increasing the CNC loading increases the tortuosity of the membrane and results in the self-assembly of CNC in the Pebax matrix, which is observed by SEM, thus leading to both reduced gas permeability and CO2/N2 selectivity. The CO2/N2 separation results of 5 wt % CNC/Pebax locate close to Upper Bound 2008, showing its potential as a CO2/N2 separation membrane material.

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