Chitosan-induced self-assembly of montmorillonite nanosheets along the end-face for methylene blue removal from water

In this study, chitosan-induced self-assembly of montmorillonite nanosheets (MMTNS) along the end-face to form the layered and porous structured composite with high adsorption capacity towards MB dye wastewater was investigated. The self-assembly process was driven by the hydrogen-bond interaction among -OH groups distributed along the end-face of MMTNS and -NH2 groups on chitosan (CS) chain, which finally formed the infinite two-dimensional lamellae. This technology remained the exposed adsorption sites on MMTNS surface, and solved the separation issue of spent MMTNS from water, making MMTNS/CS an excellent adsorption material for macromolecular MB dye. The maximum adsorption capacity of MMTNS/CS towards MB reached 243 mg/g, which was achieved via the Na+- exchange, hydrogen-bond and n-pi stacking interactions with MB molecules. This work aimed at breaking through the bottleneck of small adsorption capacity of traditional MMT adsorbents, solving the problem of solid-liquid separation of nanosheets, and effectively reducing the adsorption cost, which might guide an important direction for adsorption material design and development in the future.