A novel pyro-hydrochar via sequential carbonization of biomass waste: Preparation, characterization and adsorption capacity

Comprehensive utilization of agricultural biomass waste, such as biochar, is a hot spot in recent years. In order to keep high chemical stability, large specific surface area, and rich oxygenated functional groups of carbonized product, a novel rich-carbon material ‘pyro-hydrochar’ was proposed firstly via sequential carbonization of biomass wastes. In the present study, the pyro-hydrochar was derived from the corn straw and corncob by consecutive hydrothermal carbonization under 200 °C and then pyrolysis at the temperatures of 350–650 °C. The physicochemical properties of biochar, hydrochar and pyro-hydrochar were compared by multi-analysis including the characterization by elemental composition, BET, FTIR, XPS, SEM, chemical oxidation method by K2Cr2O7 and H2O2. The results showed the pyro-hydrochar is a newly developed rich carbon material with large specific surface area, rich functional groups, high aromatization degree and strong chemical oxidation stability. Specifically, the stable carbon-rich pyro-hydrochar indicates the strong capacity of potential carbon sequestration. Additionally, the biochar, hydrochar and pyro-hydrochar could show different adsorption performance on the representative contaminants like atrazine, Cd2+ and Cr(VI). It suggested the pyro-hydrochar with rich oxygenated functional groups and large specific surface area could be a new candidate of economic adsorbent, and it also indicated the important practical value for further modification and development of pyro-hydrochar derived from biomass wastes.