Removal of antimony (III) and cadmium (II) from aqueous solution using animal manure-derived hydrochars and pyrochars

In this study, hydrochars and pyrochars prepared from animal manures were characterized and were used to remove Sb (III) and Cd (II) from aqueous solution. Fourier transform infrared spectroscopy (FTIR) analysis revealed the interaction between Cd (II) and CO and CO groups within biochars and between Sb (III) and CO, CO and OH groups, respectively. Additionally, the lower absolute value of zeta potential of biochar after loading Sb (III) and Cd (II) suggested the occurrence of surface complexation. Existing primarily in the form of Sb (OH)₃, the maximum adsorption capacities (Q_max) for Sb (III) were lower than those for Cd (II). Due to the lower contents of surface polar functional groups and less negative surface charge, hydrochars exhibited lower Q_max for Sb (III) and Cd (II) than pyrochars. However, hydrochars in this study had higher sorption capacities for Cd (II) than most of plant-based pyrochars reported by other literature.