Photocatalytic hollow fiber membranes for the degradation of pharmaceutical compounds in wastewater

In this research, the degradation by heterogeneous photocatalysis of organic pharmaceutical waste compounds using TiO2 nanoparticles immobilized on polymeric commercial hollow fiber (HF) ultrafiltration membranes was studied. Three immobilization methods that were tested; spray-, vacuum- and sol-gel-coating. The latter was found most successful as it didn't compromise the permeability of the membrane as much as the other two methods. The sol-gel coated membranes were characterized by multiple analytical techniques, such as Raman spectroscopy, Fourier Transform Infrared Spectroscopy (FTIR), and X-ray diffraction (XRD). The compatibility of the membrane components with the aqueous feed containing pharmaceutical waste compounds was confirmed using the Hansen solubility parameters. The effectiveness of TiO2-coated membranes was then assessed in the degradation studies of two organic compounds; Methylene Blue (MB) and Chlorhexidine Digluconate (CHD), serving as the model and the target pharmaceutical compound, respectively. Spray and vacuum coating were unsuccessful in obtaining a stable TiO2 coated membranes, whereas sol-gel coating yielded a stable TiO2 layer and hence was chosen for further optimization. The immobilization of TiO2 was confirmed by SEM images and Raman spectra. Degradation of more than 30 and 40% of MB and CHD, respectively, was achieved under filtration conditions with simulated solar light radiation.