I am working on nanofiltration for different dyes removal. I synthesized pure pvdf membrane through immersion precipitation technique but it is quite weak (can be torn when taken in hand). Furthermore, water can easily pass through it (highly permeable) under no pressure and gives no dye removal. I am highly confused about it. I am using following methodology;
17 % PVDF and 83 % NMP was agitated in a beaker at 60oC, until getting homogeneous mixture. After that, the casting solution was placed in oven for 2 hrs for degassing. And then solution was casted on a glass plate. After casting, the glass plate was immersed in a water bath at 30oC, for 72 hrs. Finally the, membranes were dried at 30oC and stored.
Please highlight the mistake in the procedure.
Some errors:
The casting solution was placed in an oven for two hours. What is the temperature of the oven? Why not find another means to remove the trapped bubbles such as dark room or sonication.
Check if the casting machine was set to the right direction including thickness and speed.
Tunmise A. Otitoju Sir, firstly, thanks for your comments.
During my first time preparation, I placed the doped solution at 30o C overnight for degassing, but next day, my solution was spoiled as it became a jelly like substance.
I again synthesized the PVDF solution and degassed it by placing in oven for 2 hours at 60o C. But after casting, my membrane was not robust.
I have also tried sonication but it changed the composition of membrane as sonication produced some crystals in membrane. Sir, what do you suggest in these cases. Please guide me.
During degassing, you will need to make sure the lid is not fully closed/locked so that the bubbles can escape from the bottle. You may just open the lid half way.
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