Coupling LED-Irradiated Photocatalyst-Embedded Hierarchically Porous Polymeric Optical Fibers with Residual Chlorine for Enhanced Emerging Contaminants Degradation in Decentralized Water Treatment System

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.