Preparation of sandwich-type bipolar membrane and its application in the degradation of phenol

Chitosan (CS) was modified with nano-Pt/TiO₂ semiconductor photocatalyst (CS-Pt/TiO₂) which was prepared by doping Pt on TiO₂ in advance. CMC-Pt/TiO₂-CS bipolar membrane was then prepared using carboxymethyl cellulose(CMC)and CS-Pt/TiO₂ which were cross-linked by FeCl₃ and glutaraldehyde, respectively. Sandwich-typed CMC-Pt/TiO₂-CS bipolar membrane, the composite membrane with fine protons and hydroxyl ion-permeability, was then applied as the septum of the electrolytic cell in the degradation of phenol. Nano-Pt/TiO₂ semiconductor photocatalyst can not only generate hydroxyl radicals (·OH) which can directly degrade phenol into the small inorganic molecules, but also promote water splitting at the intermediate layer of CMC-Pt/TiO₂-CS bipolar membrane and greatly reduce the impedance and resistance(IR) of bipolar membrane. Compared CMC-Pt/TiO₂-CS bipolar membrane with CMC-TiO₂-CS bipolar membrane under UV irradiation, the degradation rate of the former is 12.7% higher than that of the latter after 80 min electrolysis at the current density of 16.7 mA·cm^-2, while IR drop of CMC-Pt/TiO₂-CS is as low as 0.9 V.