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

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 degrees C had an outstanding surface area and micropore volume (1337.9 m(2).g(-1), 0.72 cm(3).g(-1)) compared to nanoparticles carbonized at 900 degrees C (1073.9 m(2).g(-1), 0.58 cm(3).g(-1)) and 800 degrees C (480.32 m(2).g(-1), 0.25 cm(3).g(-1)). The acid treatment was applied on the 800 degrees C carbonized specimen due to its lower specific surface area than others, and an increase in its surface area and micropore volume (856.71 m(2).g(-1), 0.28 cm(3).g(-1)) was observed. The heat treatment at 1000 degrees 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, N-2 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 C = O) 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.