Chemical Engineering Journal, Vol.330, 531-540, 2017
Concurrent photocatalytic and filtration processes using doped TiO2 coated quartz fiber membranes in a photocatalytic membrane reactor
Titanium dioxide (TiO2) composite fiber membranes were prepared by means of sol-gel dip coating methods and were subsequently tested in a photocatalytic membrane reactor (PMR) experiment that incorporated two pollutant removal processes: dead-end filtration and photocatalytic degradation. TiO2 nanoparticle suspensions were initially prepared using the sol-gel synthesis. Quartz fiber filters were immediately dip coated with un-doped and doped TiO2 sols producing three types of membranes: undoped, nitrogen-doped, and boron-doped TiO2. The synthesized composite filters were analyzed for their (i) morphology using scanning electron microscopy and (ii) crystal structure using Raman spectroscopy and X-ray diffraction. Chemical composition and chemical bonding of the membranes were determined using X-ray photoelectron spectroscopy. The permeability performance of the membranes was analyzed by measuring the flux using deionized water and the removal of a representative organic pollutant, acid orange 7 (dye), was measured. The experiments were conducted in the PMR under dark and ultraviolet illumination. The removal of dye was improved when undoped and doped TiO2 filters were used in place of a bare quartz fiber filter, except in the case when boron was used at a low doping concentration. The study demonstrates that optimization of doping parameters, such as the type of dopant (nitrogen or boron) and concentration, on TiO2 filters can improve the removal rates of model molecule using ultraviolet A irradiation.