Electroactive 3D-printed monolithic PAC filters for integrated adsorption and electrochemical oxidation of dyes

Powdered activated carbon (PAC) is widely used for dye removal because of its high adsorption capacity and large specific surface area; however, its practical application is severely limited by poor handleability, difficult recovery, and low regenerability. Here, we report a three-dimensional (3D)-printed PAC-based monolithic filter that structurally and functionally integrates adsorption and electrochemical advanced oxidation within a single carbon architecture. The monolithic filters were fabricated by direct ink writing (DIW) of a carbon-rich ink containing PAC and polymeric binders, followed by solvent-exchange-induced phase inversion to generate a mechanically robust, hierarchically porous, and electrically conductive structure. The resulting 3D PAC filter preserved the high adsorption performance of PAC while providing a freestanding and reusable form. When operated as a conductive porous electrode (E-3D PAC), the filter enabled in situ generation of reactive oxygen species in the presence of H₂O₂, allowing oxidative degradation of adsorbed dyes and partial regeneration of the carbon surface within a single platform. Adsorption kinetics and isotherm analyses demonstrated strong affinity toward both anionic and cationic dyes. Electrochemical operation significantly enhanced dye removal through coupled adsorption-oxidation pathways, while the monolithic architecture maintained stable electrochemical performance over repeated treatment cycles. By unifying adsorption and electrochemical oxidation within a printable carbon framework, this work provides a scalable strategy for designing regenerable carbon-based filters for the treatment of dye-contaminated and complex wastewaters.