Improved adsorption performance of ZIF-8 towards methylene blue dye by hybridization with nanodiamond

A series of ZIF-8/OND hybrid nanostructures with different percentages of oxidized nanodiamond (OND) was prepared. Then, the adsorptive removal performance of pristine ZIF-8 and its nanohybrids with OND towards methylene blue (MB) was investigated. The fabricated adsorbents were characterized via thermogravimetric analysis, X-ray diffraction, Fourier transform infrared spectroscopy, nitrogen adsorption/desorption, field emission scanning electron microscopy and zeta potential measurements. The maximal adsorption capacity of ZIF-8 (242 mg/g) was found to grow steadily with the increment in OND content and reached an approximate plateau at 343 mg/g for the nanohybrid containing 5 wt% OND, i.e. ZND 5, with a rod-like morphology. It was realized that kinetics and isotherm of the adsorption of MB onto all the prepared adsorbents were best suited with pseudo-second order and Langmuir models. Moreover, the adsorption rate of ZIF-8 multiplied by nearly four orders of magnitude by hybridization with OND due to synergistic effects between OND and ZIF-8. Thermody-namic studies proved the adsorption of MB onto ZND 5 to be an endothermic, spontaneous, and entropy -governed process. The impact of different parameters was investigated, and the optimum conditions for the adsorptive removal of MB from polluted water were found to be at 50 degrees C and pH = 11.

Automated summary

A series of ZIF-8/OND hybrid nanostructures with different percentages of oxidized nanodiamond (OND) were prepared and investigated for their adsorptive removal performance towards methylene blue (MB). The results showed that the addition of OND significantly enhanced the adsorption capacity and rate of ZIF-8 towards MB. The adsorption of MB onto ZND 5 was found to be an endothermic, spontaneous, and entropy-governed process.