Enhancing biochar’s adsorption and solidification performance in compound-polluted aqueous solutions remains a crucial task for achieving the cost-effective removal of heavy metals from water bodies. The study examined the removal performances and mechanisms of Cu(II) and Cr(III) using biochar prepared from food waste at tem-peratures of 350 degrees C, 450 degrees C, and 550 degrees C (FWB-350, FWB-450, and FWB-550). FWB-450 exhibited the highest overall effectiveness in adsorbing Cu(II) and Cr(III), demonstrating the adsorption capacity (Qe) of 40.283 and 21.456 mg/g in single-solution, respectively. Thermodynamic parameters indicate that the adsorption process involves physical and chemical reactions involving heat absorption. The impact of Cr(III) on the adsorption of Cu (II) is more apparent in the mixed competitive system. The pH, the oxygen-functional groups and carbonate ion quantity of FWB are crucial in improving Cu(II) and Cr(III) adsorption by affect the hydrolysis, complexation, and ion exchange processes. The presence of alkaline earth metal ions in FWB, like Ca(II), aids in the elimination of Cu(II) and Cr(III) through ionic precipitation and ion exchange, correspondingly. Furthermore, FWB adsorbed with Cu(II) and Cr(III) is relatively less hazardous than solid waste. The study validates the resource utilization of FW and its potential application of biochar in heavy metal adsorption.