Two-dimensional acetate-based light lanthanide fluoride nanomaterials: An ultrahigh adsorption capacity and salt-tolerance endowed by surface acetates exchange

To develop an excellent two-dimensional (2D) adsorbent with an ultrahigh adsorption capacity and salt-tolerance is much of importance in actual wastewater treatment. In this work, 2D acetate-based light lanthanide fluoride nanomaterials (F–Ln nanosheets) are identified as high-efficient adsorbents for anionic dye decoloration. F–Ln nanosheets are prepared through a hydrothermal synthetic methodology at room temperature and pressure. Multiple characterizations demonstrate that surface acetates exchange with exogenous anions is the prominent characteristic of these nanosheets. Adsorption experiments infer that adsorption processes obey a pseudo-second-order kinetics model and a Langmuir isotherm model. The maximum Langmuir adsorption capacity for Congo red and Coomassie brilliant blue G-250 is 4334 mg/g and 2827 mg/g, respectively. The mechanism analysis suggests that surface acetates exchange of F–Ln nanosheets is responsible for their ultrahigh adsorption capacity. Besides, F–Ln nanosheets present an ultrahigh salt-tolerance in saturated NaCl or high-concentration Na2SO4, K2CO3 and NaNO3 solution. Computational studies claim that surface acetates exchange with dye anions, which has a higher binding strength than common salts, is the key to induce an ultrahigh salt-tolerance. With an ultrahigh adsorption capacity and salt-tolerance, we believe that F–Ln nanosheets promise an outstanding platform to develop excellent adsorbents for environment remediation.