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Hydrophobic membranes for system monitoring underwater gas pipelines

Rozicka A., Kujawski W., Guarnieri V., Lorenzelli L., Vasiliev A., Filippov V.

Architecture Civil Engineering Environment

2012

Vol. 5, no. 4

99--106

The aim of this work was to prepare hydrophobic membranes as selective barriers to be applied in gas sensors. Two kinds of membranes were investigated: ceramic, modified with perfluoroalkylsilanes (C6F13C2H4Si(OEt)3 – C6 and C12F25C2H4Si(OEt)3 – C12) and formed from polydimethylsiloxane (PDMS). Inorganic membranes properties after modification were tested by determining the contact angle (CA). Membrane modified by C12 was more hydrophobic (CA=148°) compared with membrane modified by C6 (CA=135°). PDMS membranes of different thickness (75-195 μm) were formed and their properties were determined by pervaporation of water and by contact angle measurements. It was shown that water transport is inversely proportional to membrane thickness and permeability coefficient was equal to 7.3_10-15 mol m-1 Pa-1 s-1. Contact angle was equal to 104°±4°. The commercial PDMS membrane properties were tested in pervaporation of water-ethanol, water-pentane and water-hexane systems and it was found that organic compound is selectively transported through the membrane (enrichment factors were equal to 4-8, 75 and 120 for ethanol, pentane and hexane, respectively). Preferential transport of organic compounds was also discussed using Hansen’s solubility parameters.

Celem pracy było otrzymanie membran hydrofobowych, przewidzianych do zastosowań w sensorach gazowych. Zbadano właściwości membran: ceramicznych, modyfikowanych powierzchniowo perfluoroalkilosilanami: (C6F13C2H4Si(OEt)3 – C6 i C12F25C2H4Si(OEt)3 – C12) oraz membran uformowanych z poli(dimetylosiloksanu) (PDMS). Właściwości membran ceramicznych po modyfikacji charakteryzowano poprzez pomiar kąta zwilżania (CA). Membrana modyfikowana roztworem C12 (CA=148°) posiadała bardziej hydrofobowe właściwości niż membrana modyfikowana C6 (CA=135°). Uformowano membrany z PDMS o różnej grubości (75-195 μm), oznaczono kąt zwilżania dla wody oraz określono ich właściwości perwaporacyjne w kontakcie z wodą. Wykazano, że transport wody przez membranę jest odwrotnie proporcjonalny do grubości błony, a współczynnik przepuszczalności wody wynosi 7.3_10-15 mol m-1 Pa-1 s-1. Właściwości komercyjnej membrany PDMS określono w kontakcie z mieszaninami: woda-etanol, woda-pentan i woda-heksan. Wykazano przy tym, iż składnik organiczny był selektywnie transportowany przez membranę (współczynniki wzbogacenia dla etanolu, pentanu i heksanu wyniosły odpowiednio 4-8, 75 i 120). Preferencyjny transport składników organicznych zinterpretowano również, stosując współczynniki rozpuszczalności Hansena.

Treatment of phenol wastewater using pervaporation

Mielczarski S., Noworyta A., Kubasiewicz-Ponitka M., Suchecki P.

Environment Protection Engineering

2005

Vol. 31, nr 3-4

23-32

The removal of phenol from aqueous solution was studied. In this case, the separation process consisting in the vacuum pervaporation and pervaporation with inert phase (gas, water) was applied. Standard pervaporation cell (Sulzer) with modified cooling zone was used. A hydrophobic membrane PDMS (Pervatech) was applied as a separating barrier. An influence of the phenol concentration in feed on its permeate flux values and the water permeate flux values in vacuum pervaporation was studied. A linear relation between the phenol permeate flux and its concentration in the feed was observed. The fluxes of penetrants dependent on the feed temperature and the pressure applied or air flow in the permeate zone were determined. On the basis of these data the selectivity coefficients were calculaed. An increase in the temperature intensifies the separation process in each option of the pervaporation process. It was observed that the selectivity and the fluxes in the vacuum pervaporation are several times higher than in pervaporation with the inert phase.