Upscaling Preparation of Poly(Biphenyl-Trifluoroacetophenone) Hollow Fiber Loose Membranes for High-Efficiency Dye/Salt Separation

With increasing water scarcity, high-salt wastewater recovery is gaining more attention. To this end, high efficiency hollow-fiber-type loose nanofiltration (HF-LNF) membranes have recently emerged. However, most conventional polymeric membranes are limited to the laboratory stage due to material-specific complexities and low permeance. Herein, a straightforward synthesis strategy is presented for the lab-scale kilogram production of poly(biphenyl-trifluoroacetophenone) (PBT) polymer and a one-step spinning process for the pilot-scale (650 m length) PBT HF-LNF membranes. Due to the slight hydrophobicity and high molecular weight of linear PBT polymer, as well as the addition of hydrophilic additives, the thermodynamic stability becomes lower, resulting in the formation of uniform 1 nm micropores. These micropores induce selective rejections for dye (>99.9%) and salt (<5%), thereby enabling effective dye/salt deep separation. The permeance is also enhanced greatly (97.3 L m⁻² h⁻¹ bar⁻¹), approximately five times higher than most reported HF-LNF membranes and commercial nanofiltration membranes. This upscaling strategy bridges lab research and industrial production, potentially advancing HF-LNF technology.