Zeolitic imidazolate framework-L incorporated graphene oxide hybrid for cadmium removal

Abstract

The removal of cadmium from wastewater is crucial to avoid its harmful effects on the ecosystem. Thus, in this study, novel composites were prepared by in situ synthesis of zeolitic imidazolate framework-L (ZIF-L) incorporated with graphene oxide (GO) of different loading ratios to produce ZIF-L/GO 20 and ZIF-L/GO 50. The adsorbents were characterized using X-ray Diffractometer (XRD), Fourier-transform Infrared Spectroscopy (FT-IR), and Scanning Electron Microscopy (SEM). The effects of Cd(II) adsorption with respect to the initial pH solution, adsorbent dosage, initial Cd(II) concentration, and contact time were investigated. Both ZIF-L/GO 20 and ZIF-L/GO 50 showed superior performance in removing Cd(II) as compared with ZIF-L (62.32% within 160 min), which were 64.35% and 70.41% within 60 min and 180 min, respectively. The optimum dosage obtained was 0.2 g/L for the removal of 100 mg/L Cd(II) synthetic wastewater. The protruding grains of flower-like ZIF-L/GO 20 allowed for faster adsorption time, whereas the smaller size of irregular shapes ZIF-L/GO 50 increased the surface area for higher adsorption capacity. Also, the adsorption of Cd(II) had fitted well with pseudo-second-order kinetic model and Langmuir isotherm. The Langmuir maximum adsorption capacities for ZIF-L, ZIF-L/GO 20, and ZIF-L/GO 50 were 163.93, 172.42, and 188.68 mg/g, respectively. The novel adsorbents ZIF-L/GO 20 and ZIF-L/GO 50 showed promising performance in the removal of Cd(II) ion from the aqueous solution.