Porous membranes for high pressure filtration

A method for purifying a fluid containing at least one contaminant, said method comprising the steps of:

• (I) providing a fluid containing at least one contaminant;
• (II) providing a flat membrane (membrane (PSP)) comprising at least one porous layer (layer (PSP)), wherein the layer (PSP) is obtained from a composition (C) comprising at least one aromatic sulfone polymer (polymer (SP)) in an amount from 7 to 60 wt. %, at least one polyphenylene polymer (polymer (PP)) in an amount of 4 to 30 wt. % and a remaining amount up to 100 wt. % of said composition (C) being provided by at least one solvent (medium (L));
• (III) contacting said fluid containing at least one contaminant and said membrane (PSP) by applying a pressure higher than 1 bar to said fluid;
• and
• (IV) recovering a fluid free from said at least one contaminant,
• wherein
• said polymer (PP) comprises at least about 10 mole percent, based on 100 moles of polymer (PP), of repeat units (Rpm) represented by the following formula:
• and at least about 10 mol percent repeat units (Rpp) represented by the following formula:
• wherein
• R1, R2, R3, R4, R5, R6, R7, and R8 are each independently selected from the group consisting of hydrogen, alkyl, aryl, alkoxy, aryloxy, alkylketone, arylketone, fluoroalkyl, fluoroaryl, bromoalkyl, bromoaryl, chloroalkyl, chloroaryl, alkylsulfone, arylsulfone, alkylamide, arylamide, alkylester, arylester, fluorine, chlorine, and bromine and
• wherein said membrane (PSP) is characterized by:
• a tensile modulus, measured according to ASTM D638 type V, of at least 235 MPa,
• a gravimetric porosity comprised between 5% and 90%, and
• a ratio between the tensile modulus as defined above and gravimetric porosity higher than 310 MPa.