Adsorptive removal of arsenic from aqueous solution by zeolitic imidazolate framework-8 (ZIF-8) nanoparticles

In this study, zeolitic imidazolate framework-8 (ZIF-8) nanosorbent was successfully synthesized via a facile method at room temperature. The ZIF-8 nanoparticles were characterized by nitrogen sorption, powder X-ray diffraction, field emission scanning electron microscope, transmission electron microscopy and Zeta potential. The synthesized ZIF-8 nanoparticles exhibited a high surface area of 1063.5 m2/g and were of 200–400 nm in particle size. The kinetic and isotherm data of arsenic adsorption on ZIF-8 were well fitted by pseudo-second-order and Langmuir models, respectively. The maximal adsorption capacities of As(III) and As(V) were of 49.49 and 60.03 mg/g, respectively, at T = 25 °C and pH 7.0. The ZIP-8 nanoparticles were stable at neutral and basic conditions. However, large amounts of Zn2+ were released into water from the sorbent at acidic condition, which dramatically hindered the adsorption of arsenic. SO42− and NO3− had no significant effect on the arsenic adsorption while the adsorption was significantly inhibited by PO43− and CO32−. X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy analysis revealed that electrostatic attraction and hydroxyl and amine groups on ZIF-8 surface played vital roles in the adsorption process.