Modifications of 3D-Printed Adsorbent Materials for Pollutant Removal from Wastewaters

Adsorption remains one of the most practical and widely adopted strategies for removing pollutants from wastewater, yet conventional powder and granular adsorbents suffer from persistent limitations: poor recyclability, difficult solid–liquid separation, and limited control over selectivity in complex, multi-contaminant streams. Three-dimensional (3D) printing has emerged as a compelling alternative, offering precise control over geometry, porosity, and macrostructure that conventional shaping methods simply cannot achieve. However, the base polymers and inks most commonly used in additive manufacturing, such as PLA, ABS, PETG, and alginate, are chemically inert and lack inherent affinity for specific pollutants. Achieving meaningful adsorption capacity therefore depends critically on how and when the active functional component is introduced into the printed structure. This review examines the full spectrum of modification strategies applied to 3D-printed adsorbents for wastewater treatment, organized by the timing of modification relative to printing. Pre-printing approaches, including composite filament fabrication, functional ink formulation, and resin doping with active materials such as MOFs, biochar, zeolites, and metal oxides, are critically evaluated alongside post-printing strategies, including surface coating, nanoparticle decoration, chemical grafting, plasma treatment, and in situ growth of porous frameworks. For each approach, the implications for pollutant selectivity are assessed across the main contaminant classes: heavy metals, synthetic dyes, and organic micropollutants such as pharmaceuticals and Bisphenol A, which are considered according to their charge, hydrophobicity, and adsorption mechanism. Finally, key structure–modification relationships are identified, gaps in regeneration, competitive-adsorption, and real-wastewater testing are highlighted, and directions for rational, pollutant-targeted adsorbent design using additive manufacturing are outlined.