Hi everybody
I fabricated bare PVDF ultra membrane by using 16% PVDF, 1% PVP, 83% NMP.
I did fouling test by using cross flow system as:
1- initially for 30 min run the membrane at 2 bar (for washing)
2-then reduced the 2 bar to 1 bar, and run the membrane for more 30 min with pure water and measured the flux
3-then I run for another 30 min with foulant (bovine serum albumin)
4- For 30 min run membrane for cross washing with pure water
5- and then run again the membrane with pure water and take the flux
But at stage 5, the flux of pure water is higher than the flux which measured at step 2. What could be the reason?
Because, according to the literatures, after fouling and cross washing membrane, the water recovery for bare PVDF should be 50-60%. But unfortunately, the flux increased in step 5 as compared to step 2...
Can someone tell me how can solve this problem????
Thanks
Hi Dear Farid
Actually I repeated the fabrication of bare membrane and also run it number of times. But still the same issue happened....
Is there some things wrong with my methodology????
I will be so thankful if you could help me????
Regards
Hi Alireza. It is possible that something inside the bovine serum albumin is reacting with the membrane and degrading the membrane walls and pores. In order to check this supposition, check the membrane dry weight after the treatment with the solution, you can do this in a beaker. If this is the problem, you need a pretreatment of the bovine serum albumin before the ultrafiltration process.
Dear Mario
Thanks a lot for ur suggestion. I will be thankful if you give ur suggestion once more. I used bovine serum albumin for fouling test.
In order to check the supposition shall I do as:
1- first cut and select two pieces of bare membrane with same size which could use for fouling test
2- dry one of selected membrane and take it's weight before fouling testing with bovine serum albumin
3- with another one, first do fouling test, and after back wash, dry it and take it's weight
possibly the the weight of the membrane after fouling test with bovine serum albumin will be lower than that before fouling test.
Is it correct? is above method correct?
Moreover, If bovine serum albumin is the problem, can kindly suggest me that how can pretreat the Albumin...Can kindly tell me the methode that can I follow it to treat bovine serum albumin???
I am so thankful
with all regards
Dear Alireza, the above method is correct. Nevertheless, Other easier method is to take a piece of membrane, wash and dry the piece, take the weight, put the piece in a beaker with the solution for 24 hours, remove the membrane piece, wash and dry again and take the final weight. If the supposition is correct, the final weight is lower than the original weight.
I am not sure about the pretreatment, first is necessary understand the causes of the problem, maybe the pH is extremely high or low. In this case, a neutralization could help. maybe a previous filtration could remove the undesirables components.
Good Luck and contact me if I could help you with anything else.
Dear Mario
Really thanks a lot for your time, concentration and kind response
I will try your suggestion, and will contact you if still I faced problem.
Once more, I am really thankful
With all regards
Another possibility is that your first water measurement was low because of capillary pressure issues. If this is truly a hydrophobic (PVDF) UF membrane 2 bar is not sufficient for water to enter membrane pores. When you did teh BSA experiment, you changed the surface tension.filtration
Typically commercial membranes are sold with a humectant that helps with the capillary pressure issue. Perhaps you did not consider this when you did the fabrication yourself
Sudhir, I would agree with your suggestion. After casting the PVDF UF membrane, it should either be treated with a 20% glycerin solution or remain submegered in water. The fact is that, BSA is not such a powerful foulant. With little effort, it can be washed off the surface and the permeability will be restored. There are some who suggest that the UF membranes naturally lose permeability after the first use and full flux restoration is not to be expected. They explain that the pores collapse, but that's not been my experience. With the correct cleaning material, the water flux should be restored 100%. Alternative foulants could be IgG and/or certain surfactants which may have a lasting affinity for the membrane.
Dear Kulkarni
Thanks a lot for ur suggestion
Regards
Dear Craig
Thanks a lot for ur time and concentration... I will also consider and try ur suggestion ....
Regards
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