Facile fabrication of hierarchical PVDF/Mg–Al LDH/chitosan membrane for textile wastewater remediation: role of LDH in anchoring chitosan

Layered double hydroxides (LDHs), as two-dimensional nanomaterials with abundant hydroxyl groups and unique layered structures, have been shown to be promising candidates to improve membrane properties for enhancing textile wastewater remediation. In this study, a PVDF/Mg–Al LDH membrane was prepared through a non-solvent-induced phase separation method, and then the hierarchical PVDF/Mg–Al LDH/chitosan membrane was fabricated through a facile filtration process. The resulting optimized membrane demonstrated an acceptable water permeance (2.3 L m −2 h −1 bar −1 ) and excellent separation efficiency for mixtures of dye and salt (i.e., rejections of 99.9 % for Congo red, 100 % for Methyl blue, and <20 % for NaCl). Notably, the separation factor of the PVDF/Mg–Al LDH/chitosan membrane for Congo red/NaCl reached up to 1934, surpassing most membranes reported in the literature. In addition, the hybrid membrane demonstrated outstanding antifouling performance (flux recovery ratio of 92.68 % for Methyl blue and 90.31 % for Congo red), and high stability under acidic and alkaline conditions. Characterization results and mechanism analysis indicate that the Mg–Al LDH nanoparticles not only improved the membrane's hydrophilicity and modulated its structure, but also played a structural bridging role within the membrane to anchor chitosan through hydrogen bonding. Mechanistic studies confirm that the size-sieving and Donnan effects were responsible for the separation of dyes and salts. This study unveils the structural bridging role of Mg–Al LDH within the membrane and provides new insights into the facile fabrication of hybrid membranes for efficient textile wastewater remediation.