Complete removal of 4-fluorophenol using a novel optical fiber photocatalysis–biodegradation–ion-adsorption system

Abstract

To effectively remove 4-fluorophenol from water, a novel optical fiber photocatalysis–biodegradation–ion-adsorption reactor, which is composed of photocatalytic optical fibers, algal–bacterial biofilm, and ion-adsorption functionalized glass fiber cloth, was developed. The photocatalytic optical fibers, i.e., polymeric carbon nitride and lanthanum-doped TiO2 coated photocatalytic optical hollow fibers (POHFs), were located in the middle-layer of the reactor. POHFs have good ultraviolet–visible–near-infrared light absorption and photocurrent conversion capability and can rapidly oxidize 4-fluorophenol into biodegradable products. The S. obliquus biofilm was located on the top layer of the reactor and enriched by phototrophs (Limnothrix and Gemmatimonas) and heterotrophs (Blastomonas and Roseococcus), which continuously consume the photocatalytic products to accumulate biomass and provide dissolved oxygen through photosynthesis to generate advanced oxidation groups. The fluoride ion (F–) absorption material, which is composed of amyloid fibril/ZrO2/activated carbon nanoparticles, was coated on the glass fiber cloth. The prepared fiber cloth was located on the bottom layer of the reactor and has good F adsorption (the adsorption rate approaches 27.8 μM/L), which enables it to effectively remove the F− in water to avoid F− poisoning of the biofilm. The results showed that the developed fiber reactor can perform complete and rapid removal of 4-fluorophenol (for 160 mL, 0.44 mM 4-FP, totally removed in 20 h) and increase biomass production (increase up to 18.0 mg/day). Hence, it provides a smart method for the effective removal and conversion of 4-fluorophenol in water.