I am a membrane researcher and sometimes expose with some formulations that the prepared membranes with same formulation and casting condition do not have same properties, specially about the pure water flux and rejection. I know that it is the common problem in the membrane fabrication world. What is the reason in your view?
Dear Foroogh,
do you still have problems with water flux? Have you checked the differences when using real media like activated sludge? In this case, the differences should be small due to more relevant cake resistances instead of membrane resistances.
Hope you have success!
Tobi
You can take advantage of this article
Poly(vinylidene fluoride-cohexafluoropropylene) (PVDF-co-HFP) Hollow Fiber Membranes Prepared from PVDF-coHFP/PEG- 600Mw/DMAC Solution for Membrane Distillation / J. APPL. POLYM. SCI. 2013, DOI: 10.1002/APP.39065, Vol. 129(6), 3304- 3313)
this problem occurs when PEG has low molecular weight and it is liquid at room temperature. In general, after casting, the solvents are evaporated, and dry porous structure is achieved. In contrast, due to liquid PEG in the matrix, the membrane cannot be fully dried. Because of that, there is a fusion of pores and a film-like structure is obtained. You can also observe a sticky nature in such films, due to PEG.
This problem also happens when we add low molecular weight PEG in the polymer to make sheet/film. To avoid this problem, you can try the high molecular weight PEG, which is completely solid at room temperature. or else, use some other material instead of that.
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