Enhanced methyl green adsorption of ZIF-8 metal-organic framework: Insights from different solvents

Abstract

This study investigates the effect of solvent type on the structural properties and adsorption performance of the ZIF-8 metal-organic framework for removing various dyes including, methyl green (MG), methylene blue (MB), and methyl orange (MO) from water in acidic and alkaline environments. ZIF-8 samples were synthesized using zinc nitrate, methylimidazole, and three different solvents including, water, methanol, and ethanol under atmospheric pressure and 70 °C. Characterization using BET, XRD, FT-IR, and TGA techniques sheds light on the structural, chemical, and thermal properties of ZIF-8 samples. Among the samples, ZIF-8/M, synthesized using methanol, stands out, demonstrating the high surface area of 2172.7 m2/g, large total pore volume of 1.5412 cm3/g, and high crystallinity of 31.9% with improved thermal stability. Furthermore, ZIF-8/M shows better adsorption performance for methyl green with a removal percentage of 81.9%, 87.1%, and an adsorption capacity of 20.5 mg/g and 21.8 mg/g, in acidic and alkaline environments, respectively. Enhanced dye adsorption of ZIF-8/M is associated with both physical and effective chemical adsorption mechanisms via tuning the environment's acidity.