P25 film, prepared by a facile dip-coating method without any binder, was further developed in a recirculating reactor for quinoline removal from synthetic wastewater. Macroporous foam Ni, which has an open three-dimensional network structure, was utilized as a substrate to make good use of UV rays. Field emission scanning electron microscopy and X-ray diffraction analysis showed that the coated/calcinated P25 films consisted of two crystal phases, and had a number of uniform microcracks on the surface. The effects of initial quinoline concentration, light intensity, reaction temperature, aeration, and initial pH were studied. Increased reaction time, light intensity, environmental temperature, and gas aeration were found to significantly improve the quinoline removal efficiency. The aeration effect of oxygen dependency on the quinoline degradation had the trend pure oxygen > air > no gas > pure nitrogen with free O₂. The solution pH crucially affected quinoline photodegradation; the high electrostatic adsorption of quinoline molecules on the TiO₂ surface was strongly pH dependent. 2-Pyridine-carboxaldehyde, 3-pyridinecarboxaldehyde, and 2(1H)-quinolinone were identified as the major intermediates of quinoline degradation. Based on these intermediates, a primary degradation mechanism was proposed. This reusable P25 film benefits the photodegradation of water contaminants and has potential in other various applications.

When reclaimed water was recharged into groundwater containing a low content of ferrous iron, Fe-rich particles were generated and started to transport into the porous medium. X-ray powder diffraction and Mössbauer spectroscopy analysis showed that the generated Fe-rich particles were in a poorly crystallized ferrihydrite phase. After the formation of ferrihydrite particles, the mass loss of contaminants was calculated, which was 88.2% for Al, 93.3% for Zn, and 41.6% for chemical oxygen demand (COD). Protein-like compounds were predominant in the removed COD. Bovine serum albumin (BSA) was used as a model to investigate the effect of proteins on the transport of ferrihydrite particles in porous medium. Results showed that the attachment efficiency of ferrihydrite particles on the porous medium decreased from 100% to 75% with the increase of BSA concentration from 10 mg/L to 100 mg/L. BSA was attached to the surface of ferrihydrite particles via electrostatic adsorption. Thus, the zeta potential of ferrihydrite particles changed from positive to negative, and the particles became less aggregated, thereby enhancing particle mobility. This observation provided evidence that protein residues in reclaimed water enhance the transport of Fe-rich particles in saturated porous medium.