Preparation of high flow cellulose derivative reverse osmosis membrane

Abstract

Abstract AN IMPROVED METHOD IS DESCRIBED FOR THE ROOM TEMPERATURE PREPARATION OF POROUS MEMBRANES OF CELLULOSIC DERIVATION AS, FOR EXAMPLE, ARE EMPLOYED IN REVERSE OSMOSIS SYSTEMS. THE PROCESS PROVIDES FOR A TWO-STEP PREPARATION CONDUCTED AT ROOM TEMPERATURE AND CONSISTING OF CASTING, DESOLVATION OF THE FILM AND IMMERSION IN A ROOM TEMPERATURE BATH AFTER WHICH THE MEMBRANE IS READY FOR USE. GAS PHASE DESOLVATION WITH A CONTROLLED ATMOSPHERE ENABLES (A) THE ROOM TEMPERATURE PREPARATION OF SUCH POROUS FILMS EVEN WHEN HIGHLY VOLATILE SOLVENTS FOR THE FILM MATERIAL ARE EMPLOYED AND (B) HEAT TREATMENT OF THE CAST FILM EITHER DURING OR AFTER IMMERSION IS OBVIATED. IN SPITE OF THE ELIMINATION OF THE HEAT CURING STEP, THE RESULTANT POROUS MEMBRANE CAN BE REPRODUCIBLY PREPARED BY THIS IMPROVED METHOD TO PROVIDE SALT REJECTION OF DIVALENT IONS (CALCIUM AND MAGNESIUM SALTS) OF GREATER THAN ABOUT 90 PRECENT AT A WATER FLUX OF AT LEAST ABOUT 0.7 GAL./DAY-FT.2-ATM.$P AT PRESSURES AS LOW AS 40 P.S.I. TESTS HAVE ESTABLISHED THAT OVER A PERIOD OF AT LEAST 12 MONTHS, A SLIGHT DECLINE WAS OBSERVED IN THE SALT REJECTION, BUT THE WATER FLUX REMAINED SUBSTANTIALLY UNDIMINISHED.

Inventors

• 👤 William J Ward
• 👤 Christopher H Knapp

Bibliographic Details