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Abstract:Immobilized TiO 2 and immobilized TiO 2 -polyethylene glycol (TiO 2 /PEG) films have been prepared via brush coating method. The formulation of immobilized TiO 2 film was prepared by mixing distilled water with P25, while the formulation containing P25 combined with 8% PEG in distilled water was used in preparing immobilized TiO 2 /PEG. A double sided adhesive tape (DSAT) was stacked onto a glass surface prior to coating with the formulations and annealing by a thermal treatment at 100 • C for 15 min. The photocatalytic activity of immobilized photocatalysts was evaluated under photodegradation of methylene blue (MB). It was observed that immobilized TiO 2 /PEG has showed a higher rate of photocatalytic activity compared to immobilize TiO 2 . The X-ray photoelectron spectroscopy and Fourier transform infrared (FT-IR) spectra of immobilized TiO 2 /PEG sample proved that the existence of C=O led to enhanced photoactivity efficiency under normal light and visible light irradiations. The photocatalytic activity performance of immobilized TiO 2 /PEG was the highest at 75 mL·min −1 aeration rate and pH 11 of MB dye. The correlation between of all these parameters was investigated in this study.

a b s t r ac tInterstitial nitrogen titanium dioxide (N-TiO 2 ) has been synthesized from solid-state microwave irradiation of commercial TiO 2 (P25) and urea, which is in contrast to other solid-state methods that give substitutional N-TiO 2 . N-TiO 2 was characterized by powder X-ray diffraction (XRD), N 2 -adsorption surface area measurement, Fourier transformed infra-red (FTIR), X-ray photoelectron spectroscopy (XPS) and UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS). FTIR, XPS and UV-Vis DRS indicate that interstitial doping of N has occurred in the TiO 2 lattice. Ti-O-N detected by FTIR at 1,449 cm -1 contributed to the N-O bond. There is no C=O bond in N-TiO 2 showing that urea was completely decomposed in modified TiO 2 . This N-O bond is also proved by XPS on deconvolution peaks detected at 404.8 and 531.5 eV in N 1s and O 1s, respectively. UV-Vis DRS analysis revealed the formation of N 2p state ca. 0.12 eV above valence band in N-TiO 2 and it is almost similar to characteristic of substitutional N-TiO 2 . Thus, the combination of substitutional and interstitial called interstitial N 2p is suggested in our prepared N-TiO 2 sample. The photocatalytic activities of N-TiO 2 and pristine TiO 2 were compared for the photodegradation of the dye reactive red 4 (RR4) under visible light irradiation from an LED source. Complete bleaching occurred within 60 min using N-TiO 2 whereas no photocatalytic degradation was observed using pristine TiO 2 .

Polypyrrole-magnetite dispersive micro-solid-phase extraction method combined with ultraviolet-visible spectrophotometry was developed for the determination of selected cationic dyes in textile wastewater. Polypyrrole-magnetite was used as adsorbent due to its thermal stability, magnetic properties, and ability to adsorb Rhodamine 6G and crystal violet. Dispersive micro-solid-phase extraction parameters were optimized, including sample pH, adsorbent amount, extraction time, and desorption solvent. The optimum polypyrrole-magnetite dispersive micro-solid phase-extraction conditions were sample pH 8, 60 mg polypyrrole-magnetite adsorbent, 5 min of extraction time, and acetonitrile as the desorption solvent. Under the optimized conditions, the polypyrrole-magnetite dispersive micro-solid-phase extraction with ultraviolet-visible method showed good linearity in the range of 0.05-7 mg/L (R > 0.9980). The method also showed a good limit of detection for the dyes (0.05 mg/L) and good analyte recoveries (97.4-111.3%) with relative standard deviations < 10%. The method was successfully applied to the analysis of dyes in textile wastewater samples where the concentration found was 1.03 mg (RSD ±7.9%) and 1.13 mg/L (RSD ± 4.6%) for Rhodamine 6G and crystal violet, respectively. It can be concluded that this method can be adopted for the rapid extraction and determination of dyes at trace concentration levels.