Enhancement in permeation and antifouling properties of PVC ultrafiltration membranes with addition of hydrophilic surfactant additives: Tween-20 and Tween-80

The effects of Tween-20 and Tween-80 as hydrophilic and non-ionic surfactants on morphology, mechanical and separation efficiency of PVC ultrafiltration membranes was studied widely. The membranes were fabricated via phase inversion method and different percentages of Tween-20 and Tween-80 from 1 wt% to 7 wt% was added to casting polymeric solution. Ultrafiltration of pure water and BSA, as the foulant, was done at the operating pressure of 2 bar. The results indicated great changes in morphology, and the membrane became more porous with macro-voids in the sub-layer, due to miscibility of surfactants with non-solvent and thermodynamic instability of the casting solution. The fabricated membranes have more hydrophilic surface and water contact angle has decreased from 70° for PVC membrane to 55° to 58° for the ones with 7 wt% Tweens. Pure water flux increased continuously with Tween addition because of higher surface hydrophilicity and more porosity. In addition, the membranes showed much better fouling resistance and were able to recover their water flux after three filtration cycles acceptably. PVC/7 wt% Tween-20 and PVC/7 wt% Tween-80 membranes showed 33% and 28% better flux recovery ratio compared to bare PVC membrane, respectively. Slight reduction in BSA rejection was observed, which was not very significant to affect the whole efficiency of the prepared membranes. The membranes have lower mechanical resistance due to more porous structure. Water flux and recovery ratio of the PVC/Tween-20 membranes were slightly higher than that of the PVC/Tween-80 membranes which can be due to more instability in thermodynamic of casting solution.