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Polydimethylsiloxane (PDMS) membrane has attracted increasing attention due to its potential application in separating organic-organic liquid mixtures and removing volatile organic compounds from water and soil. However, solvents like n-hexane, n-heptane and others are generally used in large amounts during its traditional preparation process. This study aimed to provide a low-pollution and highefficiency preparation method using water as a solvent in the presence of surfactant (dodecylbenzene sulfonic acid, DBSA). Comparisons between the membranes prepared separately with the traditional method and the green method were conducted by scanning electron microscopy (SEM), atomic force microscopy (AFM), attenuated total reflection Fourier transform infrared (FTIR-ATR) spectroscopy and pervaporation (PV) experiments. The results showed that they performed basically the same in the first three aspects but displayed markedly different characteristics in the PV experiments. The separation factors of the PDMS membranes prepared using the green method for separating 1.5 wt% n-butanol aqueous solution at 55 °C increased by 30-53% relative to those of membranes prepared using the traditional method, while the total flux only decreased by 7-10%. These performance improvements resulted from the shortening of evaporation time induced by the decrease of n-hexane content. Further, this hypothesis was confirmed by the performance of membranes prepared using the green method, from angles of crosslinking density, water contact angle and swelling degree (SD). Comparison with previous reports on PV performance of PDMS membranes implied that the green method was not only environmentfriendly and economically competitive but also led to enhanced PV performance.

Natural gas, in its migration from source rocks to release zones may travel a long distance and change the geochemical characteristics of the rocks which it flowed through. In order to study the geochemical evidence of the natural gas migration, 24 samples were taken from different natural gas migration zones in the Ordos Basin, China. Five samples of them are from natural gas release zones (dark sandstone samples), 17 samples are from bleaching zones (bleaching sandstone samples), and two samples are from non-release zones (background samples). These samples were analyzed by organic and inorganic geochemical methods. The results of GC traces and ICP-MASS indicate that three zones show different organic and inorganic geochemical characteristics. Natural gas migration and releasing may be recognized by the geochemical evidences.

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