Fluorosilaned-TiO ₂ /PVDF membrane distillation with improved wetting resistance for water recovery from high solid loading wastewater

Membrane distillation (MD) has emerged as an important technology for applications in industries such as seawater desalination and wastewater treatment due to its low energy requirement and theoretically low fouling propensity. However, the main obstacle to obtain high separating efficiency in MD lies on the availability of porous hydrophobic membrane that can withstand pore wetting and membrane fouling. In this work, a dual coagulation bath method was introduced to alter the membrane morphology by increasing its porosity, surface roughness as well as polymer crystallinity. To increase the membrane hydrophobicity, membrane roughness was induced by adding TiO ₂ nanoparticles. However, this has brought concomitant impacts by lowering its porosity due to the pore blocking and reducing hydrophobicity due to the presence of hydroxyl group on TiO ₂ surface. Introduction of silanized TiO ₂ modified at pH 7 gave higher contact angle (131.7±4) that could withstand the pore wetting and at the same time maintained its high permeation flux (12kg/m2.h) and excellent nutrient removal efficiency of 99.65%. Consistent flux around 6 kg/m2.h for Paper Mill Sequence Batch Reactor (PMSE) could be achieved showing that the membrane wetting and fouling resistance towards solids were good. The system efficiency was around 55% which was comparable to the pure water treatment process (50%). However, the membrane was not suitable to be used for treatment of the oil-rich Palm Oil Mill Effluent (POME) as the flux dropped from 6 to 2 kg/m2.h after 7 hours of operation with thermal efficiency dropped to 26% due to fouling phenomena.