NaP1 zeolite synthesized via effective extraction of Si and Al from red mud for methylene blue adsorption

Abstract

NaP1 zeolite, using red mud (RM) as raw material, was successfully prepared via alkali fusion and hydrothermal method. NaP1 zeolite, which was a mesoporous material, had specific surface area and pore diameter of 79.3 m2·g−1 and 7.26 nm, respectively. NaP1 zeolite had excellent adsorption properties. Under the optimum adsorption conditions, methylene blue (MB) was adsorbed through NaP1 zeolite, the adsorption capacity was 48.7 mg·g−1 and the removal efficiency was 97.1%. The adsorbent was regenerated with sodium chloride as eluent. The adsorption capacity of the adsorbent regenerated three times still was satisfactory 34.53 mg·g−1, which showed the excellent stability performance from NaP1 zeolite. The adsorption conformed to the pseudo second order kinetic and Freundlich isotherm model. Moreover, MB molecules were adsorbed by diffusion on the outer surface, diffusion on the inner surface, and adsorption on the inner surface of NaP1 zeolite. And, during the external diffusion, electrostatic attraction and hydrogen bonding created. Al and Si were extracted from RM to prepare NaP1 zeolite with excellent adsorption properties. This result provides an important example for the development of the potential value of RM.