Pressure effect during the formation of a selective layer on the structure and performance of dynamic composite membranes for pervaporation

Composite membranes for pervaporation were prepared by forming a selective layer based on cross-linked polyvinyl alcohol (PVA) on the porous membrane-substrate surface in the dynamic mode (via PVA solution ultrafiltration). It was found that the pressure growth results in increasing the thickness of the composite membrane selective layer. Composite membrane contact angle, flux, water content in permeate in ethanol/water (mass ratio 90/10) pervaporation were revealed to have maximum values at 3–4 atm depending on the PVA concentration in the feed solution. It was shown that the revealed dependence of the contact angle, selectivity, and permeability on the pressure of the selective layer formation is due to the compaction of the polymer matrix-substrate under the action of the transmembrane pressure and its relaxation after pressure release. When using elevated pressures (more than 3–4 atm), the relaxation of the polymer matrix causes the microdefect to form as a result of deformation of the selective layer.