Plant-Waste-Derived BiOBr/Biochar as a Floating Platform for Sustainable Solar-Driven Water Remediation

The implementation of photocatalytic water treatment technologies in real scenarios is often limited by fine powders, which hinder catalyst recovery, raise safety concerns, and reduce operational robustness. Herein, a recoverable floating photocatalytic platform is developed by directly growing bismuth oxybromide (BiOBr) onto waste-derived floating biochar pellets, yielding a buoyant composite operating at the air–water interface. The growth-based immobilization strategy ensures stable anchoring of the photoactive phase, preserving surface accessibility and enabling recovery, reuse, and regeneration. The BiOBr–biochar pellets were characterized and evaluated for abating representative organic pollutants, including pharmaceuticals, dyes, and polyphenols under simulated solar irradiation. The results demonstrate effective pollutant removal, with performances strongly dependent on molecular structure and matrix composition. In multi-pollutant systems (rhodamine-B, diclofenac and ibuprofen), selective behaviour was observed, with complete removal of diclofenac, while lower abatement was achieved for rhodamine-B and ibuprofen (ca. 88 and 25%, respectively), highlighting the role of competitive effects and transformation products. Reusability tests showed progressive activity loss for some pollutants, while maintaining structural integrity and allowing regeneration. This study proposes a sustainable and recoverable photocatalytic platform that integrates waste valorization and catalyst immobilization, providing a balanced assessment of potential and limitations of floating systems for solar-driven water treatment.