Emerging contaminants abatement in drinking water by the photocatalytic chlorine activation process using TiO₂ embedded metamaterial porous structures on polymeric optical fibers

Photocatalytic chlorine activation process shows great potential in emerging contaminants abatement in drinking water. However, its implementation in most photocatalytic slurry-based systems is hindered by the need to recover the photocatalysts from water, and the light scattering or occlusion by photocatalysts and other aqueous constituents. In this study, high mass-loading TiO2 embedded metamaterial porous structures on flexible polymeric optical fibers (TiO2-POFs) was fabricated to implement photocatalytic chlorine activation process under near UV light irradiation, termed nUV/TiO2-POFs/chlorine process, for emerging contaminants abatement in drinking water. Using bundles of 150 individual TiO2-POFs, the carbamazepine degradation rate constants (kCBZ) by nUV/TiO2-POFs/chlorine process increased from 0.019 to 0.027 min-1 with increasing chlorine concentration from 1.0 to 5.0 mgCl2/L, which is 5 to 7.1 times higher than that in the absence of chlorine. The presence of NOM, HCO3-, Cl-, SO42-, NO3-, Ca2+, Cu2+ and Fe3+ shows not impact on the CBZ degradation, while the presence of high level of Mn2+ greatly inhibited the CBZ degradation. The CBZ degradation efficiency by the process in simulated drinking water slightly decreased from 92% to 80% and 70% after 20 and 42 cycles, respectively, and further decreased to 52% after 60 cycles. The reduced reactivity of TiO2-POFs is probably due to the accumulation of Cu on the TiO2-POFs surface and could be regenerated through simple acid-washing. Compared with UV/Chlorine process, the nUV/TiO2-POFs/chlorine process exhibited a 23.7% lower yield of regulated DBPs in degrading CBZ and a 58.2% lower yield of regulated DBPs after one-day post-chlorination.