Evaluation of engineered hydrochar from KMnO4 treated bamboo residues: Physicochemical properties, hygroscopic dynamics, and morphology

[Display omitted] •A novel approach was developed to prepare the engineered hydrochar.•The physicochemical properties of the engineered hydrochar were evaluated.•Two hygroscopic dynamics models of the engineered hydrochar were compared.•The engineered hydrochar surface was covered with MnCO3 particles.•The chemical complexation between KMnO4 and hydrochar was inferred. In this study, a novel approach was developed to prepare engineered hydrochar from KMnO4 treated bamboo residues through hydrothermal carbonization. The hydrochar yields were within a specified range of 61.8–67.8% at 180 °C and 39.8–45.0% at 260 °C, respectively. The higher temperature led to the higher C content, lower H/C and O/C ratio, whereas the ash content increased with increasing KMnO4 concentration, causing the increase of solid yield as well as the decrease of C content. Pseudo-second kinetic model was optimal to describe bamboo hydrochar’s hygroscopic dynamic, and the engineered hydrochar produced at 260 °C and 1.0 wt% concentration obtained the better hydrophobicity of 0.82%. SEM-EDS and XRD analysis confirmed the existence of manganese carbonate on the surface of engineered hydrochar, from which we inferred the chemical complexation between KMnO4 and hydrochar.