Adsorption Potential of HWBC and Electrochemical Performance of Heavy Metal-Loaded HWBC

The release of heavy metals in aquatic systems may cause serious health hazards to humans and other living organisms. Adsorption is a cost-effective and efficient method for heavy metal removal. Biochar is an effective adsorbent for removing heavy metals from aquatic systems because of its larger surface area, functional group, and porous structure. In this study, hardwood-based biochar was used to remove Pb²⁺, Ni²⁺, and Cu²⁺ ions from synthetically prepared wastewater. The highest percentage adsorption of Pb²⁺, Ni²⁺, and Cu²⁺ ions was found to be 90.8 ± 1.9, 92.9 ± 2.1, and 87.9 ± 1.8%, respectively. The adsorption capacity of hardwood-based biochar for Pb²⁺, Ni²⁺, and Cu²⁺ ions was found to be 15.89 ± 0.8, 9.24 ± 0.6 and 11.61 ± 0.9 mg/g. The pseudo first-order rate constant for Pb²⁺, Ni²⁺, and Cu²⁺ ions has been evaluated to be 0.023 ± 0.02, 0.030 ± 0.01, and 0.026 ± 0.02 min⁻¹. The heavy metal ion-loaded biochar was also used as an electrode material for supercapacitors after the successful removal of heavy metal ions. The specific capacitance of Pb²⁺, Ni²⁺, and Cu²⁺ loaded hardwood-based biochar was found to be 203 F/g, and maximum power and energy densities were observed as 3600 W/kg and 3.5 Wh/kg, respectively. After 5000 cycles, the material was able to achieve a retention of 84.9%. Thus, biochar derived from hardwoods shows promise as an electrode material for supercapacitors and as an effective adsorbent for the removal of heavy metals. To improve performance, future studies should focus on surface modification, process upgradation, and assessment in real wastewater treatment and energy storage systems.