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Photocatalytic degradation of bisphenol A (BPA) was investigated using commercial TiO2 P25 nanoparticles supported on natural zeolite clinoptilolite (Cli). Employing ultrasound assisted solid-state dispersion method hybrid photocatalyst containing 20 wt% of TiO2, marked TCli-20, was prepared. The structural, morphological and surface properties, and particle size distribution of TCli-20 were studied by X-ray powder diffraction, Fourier transform infrared spectroscopy, ultraviolet–visible diffuse reflectance spectroscopy, scanning electron microscopy with energy dispersive spectroscopy, atomic force microscopy, Brunner-Emmet-Teller method and laser diffraction. The results revealed a successful loading of TiO2 P25 nanoparticles on Cli surface and the preservation of both zeolitic structure and optical properties of TiO2. The influence of catalyst dose, pH value and the addition of hydrogen peroxide (H2O2) was evaluated. The optimal reaction conditions were 2 g/L of catalyst at near-neutral conditions (pH = 6.4) for complete BPA (5 mg/L) photodegradation after 180 min of exposure to simulated solar light. The addition of H2O2 was beneficial for the degradation process and led to the removal of BPA after 120 min of irradiation. BPA removal (60% for 180 min of irradiation) was reduced when TCli-20 was tested in bottled drinking water due to the presence of bicarbonate ions which acted as scavengers for hydroxyl radicals. Even though the photocatalytic activity of TCli-20 decreased after several cycles of usage, 70% of BPA was still successfully degraded during the fourth cycle. The reusability study showed easy separation, stability and good photocatalytic ability of investigated cost-effective hybrid photocatalyst. © 2023, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.

Bisphenol A (BPA) is a well-known emerging contaminant that pose a severe threat to human health due to its negative effect on the body’s endocrine systems. BPA is widely used in the production of polycarbonate plastic and epoxy resins and therefore often detected in different water environments. Since the conventional wastewater treatments for BPA removal haven’t been proven efficient it is important to find a green and efficient method for its complete elimination. Therefore, the aim of this work was to prepare a cost-effective hybrid photocatalyst based on TiO2 nanoparticles and natural zeolite clinoptilolite and study its photocatalytic performance toward BPA. The TiO2/clinoptilolite, containing 20 wt% of TiO2, was prepared using ultrasound assisted solid-state dispersion method and characterized using a multi-technique approach by combining X-ray powder diffraction, FTIR, UV Vis DRS spectroscopy, atomic force microscopy (AFM), BET measurements and laser diffraction. The study showed complete removal of BPA (5 mg/L) after 180 minutes of simulated solar irradiation using 2 g/L of hybrid photocatalyst, at pH = 6.4. The addition of H2O2 led to a faster BPA removal after 120 minutes of irradiation. When BPA removal was tested in bottled drinking water a lower removal of 60 % after 180 minutes of irradiation was observed because of the presence of bicarbonate ions and its scavenger effect toward hydroxyl radicals. The reused photocatalyst showed good photocatalytic activity in repeated cycles (e. i. 70 % of BPA was still successfully removed at the end of the 4th cycle).

The growth of thin oxide coatings on the aluminum substrate in water-based sodium tungstate electrolyte by plasma electrolytic oxidation (PEO) is discussed and experimentally illustrated. The growth is carried out using a distinctive ultra-low duty cycle pulsed direct current (DC) power supply. During the PEO processing elements present in micro-discharges are identified using standard optical emission spectroscopy (OES) technique. The spectral line shape analysis of the first two hydrogen Balmer lines shows the presence of two types of micro-discharges. Obtained coatings are also characterized with respect to their morphology and chemical and phase composition. It is shown that coatings are composed of Al, O, and W, featuring low roughness and porosity. Partial crystallization of the coatings resulted in identification of WO3, W3O8, and gamma-Al2O3 crystalline phases.

In this paper, we employed plasma electrolytic oxidation (PEO) of aluminum in a water solution of sodium tungstate (Na2WO4 center dot 2H(2)O) with the addition of the pure and Ce-loaded zeolites clinoptilolite and 13 X for the preparation of oxide coatings. The obtained coatings were characterized with respect to their morphologies and chemical and phase compositions using scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy, atomic force microscopy, and X-ray diffraction. The prepared coatings contained gamma-alumina, WO3, and metallic tungsten. The surface morphologies of the obtained coatings strongly depended on the PEO processing time; the roughness of all coatings increased with PEO time, while porosity decreased with PEO processing time as a result of microdischarge coalescence and growth. All coatings contained elements originating from the substrate and from the electrolytes. Coatings containing zeolites with Ce showed higher photoactivity than those with immobilized pure zeolites. The highest photocatalytic activity levels were observed for coatings containing immobilized Ce-exchanged clinoptilolite processed for 10 min. It was observed that both clinoptilolite and 13X zeolites improved the features of the PEO coatings in a similar manner, making natural and abundant clinoptilolite an excellent candidate for various applications.