Novel Sandwich-Structured Hollow Fiber Membrane for High-Efficiency Membrane Distillation and Scale-Up for Pilot Validation

Abstract

Hollow fiber membranes were produced from a commercial polyvinylidene fluoride (PVDF) polymer, Kynar HSV 900, with a unique sandwich structure consisting of two sponge-like layers connected to the outer and inner skin layers while the middle layer comprises macrovoids. The sponge-like layer allows the membrane to have good mechanical strength even at low skin thickness and favors water vapor transportation during vacuum membrane distillation (VMD). The middle layer with macrovoids helps to significantly reduce the trans-membrane resistance during water vapor transportation from the feed side to the permeate side. Together, these novel structural characteristics are expected to render the PVDF hollow fiber membranes more efficient in terms of vapor flux as well as mechanical integrity. Using the chemistry and process conditions adopted from previous work, we were able to scale up the membrane fabrication from a laboratory scale of 1.5 kg to a manufacturing scale of 50 kg with consistent membrane performance. The produced PVDF membrane, with a liquid entry pressure (LEPw) of >3 bar and a pure water flux of >30 L/m2·hr (LMH) under VMD conditions at 70–80 °C, is perfectly suitable for next-generation high-efficiency membranes for desalination and industrial wastewater applications. The technology translation efforts, including membrane and module scale-up as well as the preliminary pilot-scale validation study, are discussed in detail in this paper.

A A Novel Poly (vinylidene) Fluoride/TiO2/Spent Bleaching Earth for Enhancing Hydrophilic Hollow Fibre Membrane

“…The spongy structure permits the membrane to exhibit good mechanical robustness even when the thickness is low. Additionally, it supports the transmission of mass in water [38,39].…”

“…The spongy structure permits the membrane to exhibit good mechanical robustness even when the thickness is low. Additionally, it supports the transmission of mass in water[38,39].The characteristics and pore size of the membrane surface play a key role in influencing the selectivity and performance of the HF membrane[40,41]. The surface structure depicted in Figure5(a.3) and (b.3) of the HF membrane illustrates the pore structures' formation resulting from the phase inversion process[35].…”

Scale Up and Validation of Novel Tri-Bore PVDF Hollow Fiber Membranes for Membrane Distillation Application in Desalination and Industrial Wastewater Recycling

“…In the present study, PVDF was employed as the base material due to its versatility, hydrophobicity, and resistance to a wide range of chemical reagents [22,33] for fabrication of novel tri-bore hollow fiber membranes (TBHF). The rationale behind using PVDF TBHF membranes for MD applications is that the tri-bore structure previously developed by Hua et al [34], Lu et al [35], and Luo et al [36] of Prof. Chung's group was expected to provide higher mechanical strength, higher liquid entry pressure (LEP w ) and more surface area per unit volume compared to single-bore hollow fiber membranes [37], leading to higher efficiency. The strategy involves adapting the lab-scale conditions previously developed and optimizing them for a large industrial-scale membrane fabrication unit.…”

Advanced Membrane Technologies for Wastewater Treatment and Recycling

“…Half of the published papers in this Special Issue focused on membrane fabrication and modification, with new strategies developed to improve membrane separation [ 1 , 2 , 3 , 4 ], permeability [ 5 , 6 , 7 ], and anti-fouling properties [ 8 , 9 ] by fabricating the membrane structure or surface properties. For example, Fang et al [ 1 ] fabricated a loose nanofiltration membrane by integrating blending and interfacial coordination strategies; this resulted in a membrane with good pure water flux, dye rejection, and salt penetration.…”