In situ incorporation of modified biochar for iron fouling mitigation and process optimization in membrane capacitive...

Membrane capacitive deionization (MCDI) is susceptible to irreversible membrane fouling caused by iron ions, which severely degrades desalination performance. To mitigate this bottleneck, corncob-derived activated carbons (CCACs) offering low preparation cost, balanced performance, and stability have been developed as core electrode materials. Given the detrimental impact of iron, this study systematically compared two fouling control strategies: pretreatment filtration (Model I) and in-channel biochar dosing (Model II). The results demonstrate that introducing high-surface-area modified biochar particles directly into the flow channel provides additional deposition sites for iron-based foulants, thereby extending iron removal capacity. This in situ approach increased the specific adsorption capacity by 19% relative to pretreatment filtration. Operating conditions for Model II were further optimized using the Box-Behnken design and response surface methodology, yielding a predicted SAC of 9.32 mg g^-1 under optimal parameters (1.45 V, 84.24 mg L^-1 biochar, 20.9 mL min^-1). This work elucidates a synergistic mechanism-competitive adsorption, deposition shifting, and mass transport enhancement-through which biochar mitigates iron fouling in MCDI systems, offering a cost-effective and sustainable pathway for overcoming inorganic scaling in electrosorption-based water treatment.