Facile preparation of antifouling Ti3C2Tx MXene membrane intercalated with ultrathin α-Co(OH)2 LDH nanosheets for selective dye/salt separation

Abstract

Nanofiltration (NF) membranes, characterized by the prominent permeability and selectivity, hold significant promise for textile wastewater treatment. A systematic optimization of the layered structure and surface properties of MXene-based NF membrane is essential to improve their dye/salt separation efficiency and operational stability. In this work, a highly efficient dye desalination and antifouling electroneutral MXene-based NF membrane was engineered via intercalating two-dimensional (2D) hydrophilic α-Co(OH)₂ nanosheets within MXene nanosheets. The modification of amino and carboxyl groups from ammonium acetate (AA) molecules onto the MXene nanosheets surface can impart the MXene membrane with electroneutral properties. The optimal AA-MX@LDH-1 membrane demonstrated removal efficiency exceeding 95 % for dyes such as congo red (CR, 99.9 %), methyl blue (MB, 95.7 %), and rhodamine B (RhB, 99.2 %), with a maximum water permeability of 50 L·m⁻²·h⁻¹·bar⁻¹. Meanwhile, the composite membrane exhibited ultra-low rejection for salts in the mixture of RhB and salts, with a selectivity factor up to 242.2 for RhB/NaCl, 120.8 for RhB/Na₂SO₄,194.8 for RhB/MgCl₂ and 162.7 for RhB/MgSO₄, respectively. Additionally，the membrane showed remarkable antifouling capabilities with a 98.1 % flux recovery ratio. This work highlights the significant potential of the novel MXene-based membrane with high dye rejection and salt ion permeability for effective separation of dye/salt mixtures in the textile industry, providing a promising direction for the development of high-performance MXene-based membranes.