Hydroxypropyl methacrylate thin film coating on polyvinylidene fluoride hollow fiber membranes via initiated chemical vapor deposition

Abstract

Thin films of hydroxypropyl methacrylate (HPMA) were grown on polyvinylidene fluoride (PVDF) hollow fiber membranes via initiated chemical vapor deposition (iCVD), utilising di-tert-butyl peroxide as radical initiator. This method was able to completely coat PVDF membranes, producing uniform deposition of hydrophilic HPMA of 50 nm and 100 nm thickness on the membrane surface. The deposition of HPMA layer has been evidenced from the microscopy images and Fourier transform infra-red spectra. The HPMA coated membranes exhibited significantly improved surface hydrophilicity as reflective from the reduction in water contact angle from 78.1° to 23.6° meanwhile the membrane surface roughness was reduced with the thin film coating. The separation performance of HPMA-PVDF membranes was evaluated in the treatment of in-house prepared synthetic aerobically-treated palm oil mill effluent (AT-POME), which consists of lignin and tannic acid (TA). 100HPMA-PVDF membranes exhibited improved membrane flux and rejection of 50.8L/m2h and 83.1%, respectively. Additionally, 100HPMA-PVDF membrane maintained stable high permeation and rejection properties after four filtration cycles, due to its greatly improved surface hydrophilicity and reduced surface roughness. The studies open possibilities for highly controlled surface modification of membranes using low temperature iCVD methods to tailor the membrane selective layer.