Photocatalytic discoloration of Methyl Orange on innovative parylene–TiO2 flexible thin films under simulated sunlight

Abstract

Parylene films loaded with TiO 2 are reported as photocatalysts in azo dye discoloration processes. The TiO 2 loading of the parylene film was 0.32% (w/w) and the amount of TiO 2 on the film was about two orders of magnitude below the TiO 2 added in suspension to discolore the same solution of Methyl Orange used as a probe. The parylene/TiO 2 films showed a similar activity in the presence of O 2 or H 2 O 2 during the discoloration of dyes. This shows the efficient role of O 2 as e cb À scavenger. The photonic efficiency of the parylene/TiO 2 film during the Methyl Orange discoloration was 0.04. Based on X-ray photoelectron spectroscopy (XPS) data, the TiO 2 particles loaded on the parylene film were shown to be at first encapsulated in the polymer. After the encapsulation is broken, the TiO 2 particles are fully exposed to the dye solution. The lack of surface intermediates like C-residues, N and S-species after the photocatalytic process implies an efficient decomposition of the dye at the catalyst interface. During the dye degradation carbonates and carboxylates were detected by XPS and Fourier transform infrared spectroscopy (FTIR) disappearing at the end of the discoloration process. Evidence is presented during the photocatalysis for the formation of a composite parylene/ TiO 2 film. The formation of this composite involves surface modification of parylene (partial lost of chlorine) in the outermost surface layer with concomitant densification of the TiO 2 particles on the parylene film. The parylene film presented a side with high rugosity and one with low rugosity attaching different amounts of TiO 2 in each case as observed by transmission electron microscopy (TEM). #

Parameters affecting the photocatalytic degradation of dyes using TiO2-based photocatalysts: A review

“…Actually, addition of H 2 O 2 enhanced the reaction. Zhiyong et al [47] also reported that addition of H 2 O 2 (1 mM) to methyl orange solution mediated TiO 2 Degussa P25 (0.5 g/l) under sunlight irradiated photocatalyst brought about methyl orange degradation in 1 h.…”

“…The following investigations are the proofs of enhancement of the efficiency of TiO 2 by doping [23,[38][39][40][41][42][43][44][45][46][47]. Krishna et al [48] also reported a 2.6 times higher rate coefficient for PHF-TiO 2 over TiO 2 for the degradation of triazine monoazo compound Pricion red MX-5B.…”

Modification of Parylene film-coated glass with TiO2 nanoparticles and its photocatalytic properties

“…The zirconia-modified Parylene film demonstrated the enhanced fracture resistance of dental ceramics [9]. The flexible polymer titania Parylene obtained by the immersion of a Parylene thin film (45 μm) into an alcohol suspension of TiO 2 Degussa P25 and heated at 180°C, demonstrated high photocatalytic activity in the discoloration of azo-dyes [10,11]. In another study, the authors described the liquid phase deposition of titania onto Parylene-coated Si wafers as a prerequisite for their evaluation as materials for bio-implant applications [12].…”

Fluorinated and Platinized Titania as Effective Materials in the Photocatalytic Treatment of Dyestuffs and Stained Wastewater Coming from Handicrafts Factories

“…Working with real wastewater samples, which are polluted by different types of organic substances lead to determine the true effectiveness of the photocatalytic treatment. Methyl orange and Methylene blue has extensively studied in order to know their photodegradation mechanism, which takes place mainly by unstable intermediates cations formation and successive oxidation reactions [14][15][16][17].…”

“…As TiO 2 is the most recognized and employed material in photocatalysis, many efforts have been devoted to improve its effectiveness; thus, noble metal addition [11,18], non-metals doping [19,20], sulfation and fluorination [4,[21][22][23][24][25][26][27][28][29][30] among others have been reported to be suitable alternatives for titania modification. Taking into account that the practical application of TiO 2 is not in the form of dispersions, many studies in this area have been also focused on supported TiO 2 being photolyzed in the presence of a pollutant during a continuous cleaning process [14,16,28,31,32], in these processes the separation of the pollutant from the processed solution at the end of the process it is not necessary.…”