Electrospinning preparation of PAN/TiO2/PANI hybrid fiber membrane with highly selective adsorption and photocatalytic regeneration properties

Fiber membranes for pollutants removal have attracted more and more attentions owing to their high adsorption performance and easy recovery properties. However, some adsorption membranes are short of reusability performance due to lack of environment-friendly regeneration approach and low regeneration efficiency especially in terms of chemical adsorption. Herein a polyacrylonitrile/ titanium dioxide/ polyaniline (PAN/TiO2/PANI) hybrid fiber membrane was successfully prepared by electrospinning of PAN solution with TiO2 particles and subsequent in-situ oxidative polymerization of aniline (ANI) on PAN/TiO2 fiber membranes. The obtained fibers have ~200 nm in width with PANI and TiO2 particles dispersed uniformly. Importantly, such hybrid membrane could remove Congo red effectively and completely in water. Detailed investigation reveals that the adsorption behavior fits Langmuir model well which indicates chemical related adsorption. In addition, the membranes could be recycled by photocatalytic degradation under visible light irradiation. After 4 times photocatalytic regenerations, the regeneration efficiency and removal rate could still remain ~60% and upon 50%, respectively, higher than that of water-wash regeneration (only 2%). Such extraordinary performance could also extend to heavy metals [such as Cr (VI)]. After equilibrium adsorption, the adsorbed Cr(VI) on membrane could be reduced and desorbed through visible light photocatalytic procedure, leading to an effective regeneration. This work not only demonstrates the possibility and validity of the PAN/TiO2/PANI hybrid fiber membrane as promising environment-friendly adsorbent for pollutants removal, but also gives further insight into understanding the adsorptive behavior of the hybrid membrane.