Preparation and Adsorption Properties of Green Sustainable Biomass Carbon Microspheres

In this study, carbon microspheres (CSn) with various oxygen-containing functional groups (−OH, −C═O, −COOR) were prepared through hydrothermal carbonization at different temperatures. The raw material is the micro-/nanocellulose prepared from factory poplar waste. Methylene blue (MB), as the model dye, was used to verify the adsorption performances. The influences of different adsorption parameters, such as adsorption time, temperature, solution pH, and ion concentration, were analyzed. The adsorption kinetics was well fitted to the pseudo-second-order model. The adsorption isotherm was better described by the Langmuir isotherm with the maximum adsorption capacity (536.64 mg g–1) at room temperature. Using Fourier transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS), and adsorption processes, it was confirmed that the interactions between the oxygen-containing functional groups and methylene blue were the key factor affecting the adsorption. At the same time, it was further confirmed that the content of the oxygen-containing functional groups of the CSn had been relatively reduced with the increases in the temperature, and the adsorption capacity of methylene blue was also decreased. The CSn after adsorption of methylene blue were directly pyrolyzed and its electrical conductivity was also significantly improved. The conducting material not only solved the dilemma of desorption waste liquid treatment but also achieved the dual application of the materials. Therefore, CSn is considered to be a green and sustainable carbon material.