Toward effective fluorinated terpolymer-based materials for desalination with superior mechanical, chemical and anti-icing features

Abstract

For the first time poly(tetrafluorethylene-co-hexafluorpropylene-co-vinylidenfluoride) (THV) was successfully implemented to form stable planar porous membranes. This new and highly hydrophobic material was modified with biopolymer-chitosan that was used as a pristine hydrophilic additive or hydrophobized-filler with a silane-based modifier. Owing to the implementation of the vapor-induced-phase-separation method, it was possible to tune surface morphology and chemistry of final materials. Such a procedure allows to find the balance between the adjusted properties of additive chemistry (hydrophobicity) and membrane morphology (pore size, LEP, roughness) and as a consequence, control transport features in the membrane distillation process. The values of water permeate flux were boosted from 8.40 ± 0.50 kg m−2 h−1 for THV pristine membrane to 15.84 ± 0.84 kg m−2 h−1 and 38.42 ± 0.93 kg m−2 h−1 for THV modified with silane-functionalized low-molecular-weight-chitosan (THV + CSLMm) at the lowest and highest driving forces. The stability of materials in the long run (up to 60 h) without chitosan leakage was presented. A superior improvement in mechanical features, i.e., Young's modulus, was detected for modified samples. There is scarce data on THV, and therefore it is necessary to study its diverse features. Thus, anti-icing properties were evaluated, and some new correlations describing the icing process were developed, among them new relation between the time of recalescence and LEP.