Carbonization temperature effects on adsorption performance of metal-organic framework derived nanoporous carbon for removal of methylene blue from wastewater; experimental and spectrometry study

Abstract

In this study, heat treatment effects on adsorption capabilities of nanoporous carbon particles derived from the metal-organic framework (MOF) were investigated at different temperatures. The carbon nanoparticles were synthesized by one-step carbonization of the metal-organic framework crystals. The results showed that the MOF derived carbons at 1000 °C had an outstanding surface area and micropore volume (1337.9 m2·g−1, 0.72 cm3·g−1) compared to nanoparticles carbonized at 900 °C (1073.9 m2·g−1, 0.58 cm3·g−1) and 800 °C (480.32 m2·g−1, 0.25cm3·g−1). The acid treatment was applied on the 800 °C carbonized specimen due to its lower specific surface area than others, and an increase in its surface area and micropore volume (856.71 m2·g−1, 0.28 cm3·g−1) was observed. The heat treatment at 1000 °C had a significant impact on the adsorption capacity of synthesized MOF derived porous carbon for the removing of methylene blue (MB) (about 2724 mg·g−1) from wastewater. The physicochemical properties of the MOF derived carbon samples were characterized by X-ray diffraction (XRD), HR-TEM, N2 adsorption-desorption, FTIR, Raman Spectroscopy, TGA, and X-ray photoelectron spectroscopy (XPS) analyses. From the XPS results, the chemical environment of oxygen-containing functional groups (C−O and CO) changed by enhancing the temperature that provides sufficient reactive sites for the MB binding during the sorption process. Also, by investigation of the adsorption isotherms of Langmuir, Freundlich Dubinin-Radushkevich (D-R), and Temkin concluded that the D-R isotherm model fitted better with the experimental data than the others. The best kinetic model for the MB adsorption onto the synthesized MOF derived carbons was the pseudo-second-order model. Based on the thermodynamic calculations, the adsorption process is found to be spontaneous and endothermic.