The Ca/Fe-rich antibiotic fermentation residue (AFR) is a hazardous waste in China, which can also be regarded as both biomass and metal resources. However, the existing treatment technology rarely pays attention to the concurrent recycle of the two resources. Meanwhile, information about the application of AFR-derived biochar is still limited. Therefore, in this study, the Ca/Fe-rich tobramycin fermentation residue was used for the fabrication of hydrochars and pyrochars using hydrothermal carbonation and pyrolysis, respectively, followed by the investigation of the phosphate adsorption performance of the hydrochars and pyrochars. The results show that both hydrochars and pyrochars contained high Ca and Fe contents; whereas, the pyrochars exhibited high affinity for phosphate and strong magnetism without further modification. Among pyrochars, the one prepared at 600 °C (PC-600) was most suitable for phosphate adsorption from aqueous solution. Alkaline environment was favorable for phosphate adsorption by PC-600. The adsorption process was almost not affected by Cl-
, but was promoted by HCO3-
. PC-600 exhibited rapid kinetics with an equilibrium time of 420 min. The adsorption process could be fitted well by the Langmuir model, and the maximum adsorption capacity (qm
) reached 108 mg/g at 35 °C. The main adsorption mechanism included precipitation and ligand exchange. This study can realize the concurrent recovery and utilization of biomass and metal resources from the Ca/Fe-rich AFR, provide reference for the application of AFR-derived biochar, and provide efficient materials for the treatment of phosphorus polluted water.