Construction of TiO₂-ZrO₂ composite nanofiltration membranes for efficient selective separation of dyes and salts

The ceramic nanofiltration (NF) membrane exhibits excellent potential for textile wastewater treatment due to its efficient selective separation of dyes and salts. In this study, a high-performance TiO₂-ZrO₂ composite nanofiltration membrane was fabricated via a sol–gel method. Stable sols with an average particle size of approximately 2 nm were obtained. The addition of TiO₂ effectively inhibits the phase transformation of ZrO₂ during heat treatment, thus improving the integrity and ensuring separation accuracy of the membrane. Moreover, an optimal balance between membrane integrity and thickness was achieved, promoting efficient selectivity towards dyes and salts. The optimized NF membrane exhibited a MWCO of 1 kDa, a membrane thickness of 100 nm, and pure water permeance of 44 L∙m⁻²∙h⁻¹∙bar⁻¹. Additionally, the NF membrane demonstrated exceptional performance in dye/salt separation as evidenced by rejection rates exceeding 97.71% for Reactive Blue 19 while maintaining rejections below 5% for NaCl/Na₂SO₄ solutions. A stable permeance of 21.65 L∙m⁻²∙h⁻¹∙bar⁻¹ was achieved during the separation process. In conclusion, this study presents a high-performance ceramic NF membrane which exhibits significant potential for treating dye/salt containing wastewater.