Coupling LED-Irradiated Photocatalyst-Embedded Hierarchically Porous Polymeric Optical Fibers with Residual Chlorine...

Addressing global water scarcity requires the development of efficient decentralized water treatment technologies. This study presents novel hierarchically porous TiO₂-embedded polymeric optical fibers (TiO₂-POFs) with a lotus-leaf-like bionic and micro/mesoporous structure for the removal of emerging contaminants (ECs). When coupled with UV-A LEDs and trace chlorine (5.0 mg/L), the system achieved a carbamazepine degradation rate constant of 0.0302 min^-1 (1.167 cm²/μeinstein or 0.0143 cm²/mJ), which was 8.4 times that without chlorine, and a order of magnitude lower electrical energy per order (EE/O) of CBZ degradation (0.001 kWh/m³/order) compared to the median EE/O of the existing UVC-based AOPs. The enhancement was attributed to chlorine activation by photoinduced holes, electrons, and superoxide radicals, ultimately generating hydroxyl radicals (HO^•), which were responsible for 99.4% of the degradation. The unique hydrophobic interface of TiO₂-POFs confers a high affinity for hydrophobic pollutants and superior resistance to matrix quenching by hydrophilic natural organic matter. This enables the rapid degradation (within 2-5 min) of ECs at environmentally relevant (ng/L) levels in complex matrices like real tap water. The system maintained high activity after treating ∼454 L of tap water and exhibited excellent structural stability under an accumulated HO^• exposure of ∼1.04 × 10^-8 M·s. A 40% decrease was observed after high Cu²⁺ exposure, i.e., equivalent to treating 19,800 L of water due to copper oxide/hydroxide deposition. Simple acid washing using household vinegar or dilute nitric acid readily restores their activity. Furthermore, the process yielded less disinfection byproduct (DBP) compared to UV-C/chlorine due to the in situ adsorption and degradation of DBPs and their precursors. With its high selectivity, efficiency, safety, and stability, the UV-A-irradiated TiO₂-POF chlorine process represents a highly promising strategy for safe and effective decentralized water purification.