Hydrothermal treatment of high-ash microalgae: Focusing on the physicochemical and combustion properties of hydrochars

Natural microalgae with high ash content are common in water environment. Converting them into biofuels not only meets the energy demands, but also improves the aquatic environment. This study aims to explore the physicochemical properties and molecular structural features of hydrochars derived from hydrothermal treatment of natural microalgae. Meanwhile, the combustion behavior and kinetics analysis of hydrochars were also evaluated. The hydrothermal treatment was performed with natural microalgae and its acid-washing microalgae under different temperature from 260℃ to 340℃ to reveal the effect of ash on hydrochars properties. The results indicate that the ash significantly influences the functional groups composition and physicochemical property of hydrochars. The yields of hydrochars derived from deashing microalgae are lower than those of hydrochars derived from natural microalgae. However, the relative content of C-C/C-H/C=C groups representing hydrocarbon carbon in hydrochars derived from deashing m...