Ultrathin sodium ferric silicate 2D nanosheets: A novel and robust adsorbent for selective removal of cationic dyes in wastewater

Sodium ferric silicate nanosheets with ultrathin 2D structure were firstly synthesized by hydrothermal method using ferric nitrate and sodium silicate as precursors. The as-prepared nanosheets were characterized by SEM, TEM, AFM, XRD, XPS and N-2-physisorption. Adsorption of ten dyes (including 5 cationic dyes and 5 anionic dyes) from aqueous solutions was investigated and discussed. The nanosheets were found to be amorphous and had a thickness of 0.85 nm. The ultrathin nanosheets displayed remarkable selective adsorption capacity toward cationic dyes due to the features of high specific surface area, negative charged surface and good mass transportation property. In particular, such ultrathin nanosheets showed a maximum adsorption capacity of 1.77 mg m(-2) per unit surface area for methylene blue (MB), which is the highest value among the reported silicates adsorbents. The equilibrium adsorption data of MB suggested that the Langmuir model was much more suitable for the experimental data, and the pseudo-second-order kinetic equation could well describe the adsorption kinetics. Moreover, the sodium ferric silicate nanosheets could be regenerated by simple calcination and used repeatedly in dyes removal, demonstrating the potential application in wastewater purification and treatment. (C) 2019 Elsevier B.V. All rights reserved.