Effect of Solution pH on the Carbon Microsphere Synthesized by Hydrothermal Carbonization

Carbon microspheres(CMSs) in a diameter of 10colonm were prepared by the hydrothermal carbonization of starch under different solution pH value. The structures and surface chemical properties of obtained CMSs before and after carbonization were characterized and compared by SEM images, nitrogen adsorption isotherms and FT-IR spectra. The results showed that the suitable solution pH value of hydrothermal carbonization ranged from 3 to 7, whereas starting pH of 1 only accelerated the hydrolysis of starch and the formation of microsphere in the early stage of the reaction. The surface chemical groups of the carbon microsphere determined its adsorption on acetic acid, while the porous structure took the role on adsorption after carbonization at 600 °C for 2 h.