Chemical Vapor Deposition of Photocatalyst Nanoparticles on PVDF Membranes for Advanced Oxidation Processes

Giovanni De Filpo, Elvira Pantuso, Katia Armentano, Patrizia Formoso, Gianluca Di Profio, Teresa Poerio, Enrica Fontananova, Carmen Meringolo, Alexander Mashin, Fiore Nicoletta
2018 Membranes  
The chemical binding of photocatalytic materials, such as TiO 2 and ZnO nanoparticles, onto porous polymer membranes requires a series of chemical reactions and long purification processes, which often result in small amounts of trapped nanoparticles with reduced photocatalytic activity. In this work, a chemical vapor deposition technique was investigated in order to allow the nucleation and growth of ZnO and TiO 2 nanoparticles onto polyvinylidene difluoride (PVDF) porous membranes for
more » ... ion in advanced oxidation processes. The thickness of obtained surface coatings by sputtered nanoparticles was found to depend on process conditions. The photocatalytic efficiency of sputtered membranes was tested against both a model drug and a model organic pollutant in a small continuous flow reactor. 2 of 15 onto the substrate surface. In a CVD process, the deposited (target) material reacts chemically with the substrate, while in PVD processes, the deposited molecules and substrate are still distinct [4] . Separation, concentration, and purification processes present some challenges for chemical industries. Efficient separation and purification are also important for food and pharmaceutical plants in order to guarantee high-quality water after removal of toxic components from industrial wastewater. Pharmaceutical active compounds can be considered as hazardous substances because of their potential threat to health and the environment. They are also considered an emerging pollutant due to the failure of classical treatments (such as filtration, adsorption, bio-oxidation, sedimentation, coagulation, chlorination, and UV-irradiation) to effectively remove them [5] [6] [7] . In addition to common chemical pollutants, over 80 pharmaceutical active compounds have been detected in wastewater effluents and surface water across the world [8], with concentration ranging from few ng L −1 to several g L −1 . The most important sources of pharmaceutical active compounds are incorrect disposal of unused drugs and effluents of wastewater treatment plants (including pharmaceutical industries, hospital wastewater, aqua-farming, and cattle-breeding) [9] [10] [11] . While the measured concentrations can result in water that is low or below drinking water guidelines and health criteria [12] , their continuous accumulation in aquatic environment can also represent a real hazard. More recently, polymer membranes have been used as innovative separation materials [13] . A membrane can be defined as "a barrier that separates and/or contacts two different regions and controls the exchange of matter and energy between the regions" [14] . Today, membranes are efficiently used for water desalinization, wastewater purification, recovery of valuable constituents from production waste, gas separation in petrochemical processes, concentration and purification in food and drug applications, artificial organs and therapeutic systems, energy conversion, and storage systems [15] [16] [17] . In addition to their technical simplicity and energy efficiency, membrane processes can be easily upscaled from batchwise treatment of small quantities to large-scale continuous operations. An advanced oxidation process (AOP) is a simple technique that allows an efficient degradation of organic pollutants generally found in wastewater. In an AOP, organic pollutants are mineralized by the generation of highly reactive hydroxyl radicals [18] . Among the advanced treatment technologies, UV photocatalysis by nanoparticles (e.g., ZnO and TiO 2 ), has attracted great interest in recent years [19] . In a photooxidation process (Figure 1 ), electrons are promoted from valence band to conduction band-resulting in the formation of electron-hole pairs-when the catalyst nanoparticle (CNp) is irradiated by UV light with energy intensity larger than the characteristic band gap (3.37 eV for ZnO and 3.2 eV for TiO 2 , respectively) [20, 21] . Membranes 2018, 8, x FOR PEER REVIEW 2 of 15
doi:10.3390/membranes8030035 pmid:29933602 fatcat:vqqo346wz5b3zmfylnjvl6c3qq