Enhanced capacitive deionization using a biochar-integrated novel flow-electrode

In this study, we investigate the performance of a capacitive deionization system using a flow-electrode composed of biochar prepared via pyrolysis at 700 °C in combination with activated carbon. Furthermore, we introduce lead, one of the leading heavy metals known, as a model pollutant to further assess the potential applicability of the system. By comparing the adsorption of multiple ions (i.e., sodium, chloride, lead) using activated carbon alone and in combination with the synthesized biochar under homogeneous conditions, enhancement in system performance by approximately 1.83-fold is indicated using the composite flow-electrode. The distinction of biochar was based on its superior electrical efficiency, with higher mass loading leading to further reduction in solution and charge transfer resistances by 80.8 and 98.7%, respectively, and thus the improvement in system deionization. Accordingly, adopting the optimum operational conditions (applied voltage of 0.9 V, and flow-electrode composition of AC35 B10), the FCDI process achieves outstanding performance in desalination and the further removal of heavy-metal lead ions. To the best of our knowledge, this study is the first to apply biochar as a new innovative flow-electrode material in an FCDI system.