Efficient and fast adsorption of methylene blue dye onto a nanosheet MFI zeolite

ZSM-5 zeolite is a promising adsorbent for pollutant removal from aqueous solution. The micropore and long diffusion pathway, however, restrict the adsorption performance for large molecules. Thus, a nanosheet MFI zeolite (NZ) with ultrathin lamellar structure, large average pore diameter (3.94 nm), high BET surface area (365.28 m(2) g(-1)) and large pore volume (0.74 cm(3) g(-1)) was synthesized in order to enhance the adsorption performance. Its adsorption performance for methylene blue (MB) was studied comparatively with the conventional ZSM-5 zeolite (CZ). For both CZ and NZ, the adsorption of MB was favored at a higher pH value and the optimal pH value was 10. The adsorption conformed to pseudo-second order model and Langmuir model according to the higher calculated values of R-2. The adsorption process was so fast that it reached equilibrium within 10 min. The maximum adsorption capacity of MB onto NZ was 476.19 mg g(-1), which was much higher than that onto CZ (105.82 mg g(-1)). The adsorption of MB onto NZ and CZ was spontaneous and endothermic. The adsorption mechanism can be attributed to electrostatic adsorption and hydrogen bonding between zeolite and MB molecule. The excellent texture property of NZ endowed it with a higher adsorption performance.

Automated summary

The nanosheet MFI zeolite with ultrathin lamellar structure showed superior adsorption performance for methylene blue compared to the conventional ZSM-5 zeolite. Higher pH values favored the adsorption of methylene blue for both types of zeolite, with fast adsorption rates and shorter time to reach equilibrium.