Incorporation of transition metal-oxide on 3D porous carbon network for electrochemical water desalination and heavy-metals removal.

Electrochemical technologies, specifically capacitive deionization, are a robust, emerging and energy-efficient wastewater treatment process for effectively eradicating heavy metals and desalting saline water streams. The performance of electrosorption-based ion removal explicitly depends on the nature of electrode materials. In this research, activated carbon (AC) derived from palm kernel shell (PKS) and the impregnation of transition metal oxide (TMO), such as cobalt-oxide (Co₃O₄) nanoparticles on PKSAC were synthesized by a carbonization process of 800 °C followed by a single-step hydrothermal technique at 160 °C, respectively. The metal-oxide-coated nanocomposite has a mesoporous structure with a specific surface area of 1200 m²/g. The performance of CDI electrodes developed by the pristine activated carbon and its associated nanocomposite was tested for desalination applications in an asymmetric configuration. Comparatively, the nanohybrid (Co₃O₄-PKSAC) electrode revealed a maximum specific capacitance of 414.3 F/g than PKSAC (365.4 F/g), respectively. Further, the asymmetric configuration of electrodes developed by PKSAC and Co₃O₄-PKSAC possessed a higher electrosorption capacity of 23.21 mg/g, 56.32 and 45.71 for NaCl, Pb²⁺ and Cd²⁺, respectively, at an initial concentration of 750 mg/L and an applied voltage of 1.2 V. The isothermal analysis and kinetic modelling demonstrated that the Langmuir isotherm and pseudo-first-order kinetic model best fit the experimental data for heavy metal electrosorption. Noticeably, the cyclic studies demonstrated that the electrodes retain the separation performance, and, hence, confirmed the applicability of the developed electrodes for the long-term desalination and wastewater treatment processes.