Surface-functionalized g-C3N4/3D-printed alkali-activated materials for the removal of emerging water pollutants

The growing demand for sustainable water treatment technologies has spurred interest in structured photocatalytic materials. Herein, we report the first integration of 3D-printed alkali-activated material (AAM) scaffolds with graphitic carbon nitride (g-C₃N₄) for visible-light-driven degradation of emerging organic contaminants. The scaffolds, fabricated by direct ink writing and subsequently functionalized via a PVA-assisted coating, exhibit preserved mesoporosity and uniform g-C₃N₄ coverage. Structural and spectroscopic analyses confirm the successful anchoring of g-C₃N₄ onto the AAM surface, preventing leaching and ensuring long-term reusability. Nitrogen physisorption revealed a moderate decrease in specific surface area (from 90 to 64 m 2 g −1 ) due to partial pore coverage, while maintaining accessible mesoporosity beneficial for mass transfer and interfacial photocatalysis. Under visible-light irradiation, the hybrid monolith achieved 99 % sulfamethoxazole (SMX) degradation and 72.5 % total organic carbon (TOC) mineralization within 210 min using only 1.6 g L −1 of catalyst—surpassing most powdered systems in efficiency-to-dose ratio. Beyond SMX, tests with a quaternary mixture of carbamazepine, ciprofloxacin, and diclofenac confirmed broad-spectrum photocatalytic activity. Quenching and EPR analyses identified •OH, O ₂ •- , and 1 O ₂ as the main reactive oxygen species. Ecotoxicological assays with freshwater microalgae, rotifers, and zebrafish embryos demonstrated a marked reduction in post-treatment toxicity, validating the environmental safety of the process. This reusable and monolithic photocatalytic platform represents a robust, metal-free, and sustainable solution for real-water purification.