SURFACE CHEMICAL REACTION TECHNIQUES FOR ULTRATHIN COMPOSITEMEMBRANES

MEMBRANE DIFFUSION IS AN INHERENTLY SLOW PROCESS. CONSEQUENTLY, MEMBRANE-BASED SEPARATION PROCESSES CAN ONLY BE ECONOMICALLY VIABLE IF EXTREMELY THIN, DEFECT-FREE MEMBRANES ARE USED. THIN-FILM COMPOSITE MEMBRANES WITH A PERMSELECTIVE LAYER THICKNESS DOWN TO ABOUT 0.5 MUM CAN BE MADE BY PRESENTLY AVAILABLE TECHNIQUES. THE GOAL OF THIS PROGRAM IS TO DEVELOP THE TECHNOLOGY FOR MAKING INDUSTRIAL-SCALE COMPOSITE MEMBRANES WITH A PERMSELECTIVE LAYER THICKNESS OF 0.1 MUM OR BELOW. THE MEMBRANES WILL BE MADE BY SOLUTION COATING AN ELASTOMERIC POLYMER MATERIAL ONTO A MICROPOROUS SUPPORT. THE UPPER SURFACE OF THE COATED LAYER WILL THEN BE CONVERTED TO A GLASSY CROSSLINKED ZONE BY SURFACE TREATMENT WITH A REACTIVE ORANGIC SPECIES. THE RESULT WILL BE A ZONE OF THICKNESS LESS THAN 0.1 MUM WITH GREATLY ENHANCED SELECTIVITY. BECAUSE THE GLASSY LAYER IS SO THIN, THE FLUX WILL ALSO BE VERY HIGH COMPARED WITH THAT OF A STANDARD COMPOSITE MEMBRANE WITH A GLASSY PERMSELECTIVE LAYER.