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.