Adsorption Kinetic and Isothermal Studies of 2,4-Dichlorophenol from Aqueous Solutions with Zeolitic Imidazolate Framework-8 (ZIF-8)

Abstract

It has been observed that 2,4-dichlorophenol (2,4-DCP) possesses great environmental concern for its high ecotoxicity and ubiquitousness. Adsorption is one of the simplest methods to remove the 2,4-DCP from the aqueous solutions. We conducted the synthesis of zeolite imidazolate framework-8 (ZIF-8) via a classic and facile approach as an adsorbent to remove the 2,4-DCP, while considering the superior stability and high surface area of ZIF material. The synthesized ZIF-8 material was characterized by powder X-ray diffraction, field emission-scanning electron microscope, thermal gravimetric analyses, derivative thermogravimetry, and N2 adsorption–desorption isotherms. The optimal pH conditions, adsorption kinetics, and adsorption isotherms were determined via batch adsorption equilibrium experiments. The results showed that the difference of adsorption capacity under different pH conditions could be explained via the electrostatic interaction and electrostatic repulsion between ZIF-8 and 2,4-DCP, and the optimal adsorption condition was obtained in the solution with pH 9. In addition, the Langmuir model and pseudo-second-order equation could best describe the adsorption isotherm and kinetic data, respectively. The maximum adsorption capacity was 107.07 mg/g with 50 mg/L of 2,4-DCP initial concentration at 323 K, which was comparable to some previous work. In short, it is a promising method to remove 2,4-DCP with ZIF-8 from aqueous solutions.