Facile fabrication of SiO2-ZrO2/Al2O3 ceramic hollow fiber nanofiltration membrane for hot industrial wastewater treatment

Abstract

Ceramic nanofiltration (NF) membranes exhibit superior stability and can operate effectively under harsh conditions. However, the tedious fabrication processes always result in a high cost for ceramic NF membranes. In this work, SiO₂–ZrO₂/Al₂O₃ ceramic hollow fiber NF membranes are facilely fabricated. Boehmite sol only is used to create the interlayer between the support and the SiO₂–ZrO₂ separation layer. By optimizing the pore size and thickness of this interlayer, the modification process for the support is streamlined from multiple steps to a single step. Additionally, the required number of SiO₂–ZrO₂ layer coatings is substantially reduced, significantly enhancing process efficiency. Meanwhile, this work also identifies the characteristics of an appropriate interlayer that meets the requirements for effectively coating the SiO₂–ZrO₂ layer. Finally, an optimized ceramic NF membrane with a molecular weight cut-off (MWCO) of 1000 Da and an average pore size of 1.59 nm is achieved. This ceramic NF membrane reveals superior retention for most dyes and high transport for monovalent salts (retention <20 %). In the application of dye desalination for hot textile wastewater treatment, the membrane displays an excellent permeance of more than 6 LMH/bar and good selectivity for dye/salt mixture solutions at 60 °C (e.g. the separation factors for EB/NaCl, BS/NaCl, CR/NaCl, and EBT/NaCl attained 256, 872, 100 and 433, respectively). Meanwhile, the membrane exhibits outstanding hydrothermal stability and remarkable resistance to membrane fouling under harsh acid and alkali conditions, maintaining stable separation performance for dye desalination over 100 h at 60 °C.