Poly(vinylidene fluoride) (PVDF) and its derivative copolymer PVDF-graft-poly(methacrylic acid) (PVDF-g-PMAA) were blended to prepare pH-responsive membranes. The effects of the following factors on stimuli-responsive membrane performance were systematically examined: (1) amount of PVDF-g-PMAA additives, (2) extent of purification, (3) concentration of polymer, (4) addition of poly(ethylene glycol) (PEG), and (5) type of solvent. Field-emission scanning electron microscopy (FESEM), contact angle goniometry, atomic force microscopy (AFM), attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), flux and solute rejection performance were used to characterize our fabricated membranes. We found that partially purified PVDF-g-PMAA membrane contains more surface PMAA than the purified one (purified signifies that excess unreacted species were removed). In addition, a much higher flux performance and pH-responsive coefficient were found for the partially purified PVDF-g-PMAA membranes; consequently, membranes were only partially purified throughout our work. The flux of the pH-responsive membranes is dramatically increased by decreasing the polymer concentration from 18wt% to 15wt% and by adding PEG and PVDF-g-PMAA. We could create a tunable broad range flux from ~ 1 to 1200L/m2h by adjusting the polymer concentration, adding PEG and PVDF-g-PMAA, and using different solvents. Our tunable approach has great potential for various applications (e.g., water treatment and food processing).
Financed by the National Centre for Research and Development under grant No. SP/I/1/77065/10 by the strategic scientific research and experimental development program:
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