Polyethylene terephthalate (PET) is one of the most widely used materials for food packaging and fishing nets. After use it become waste and, due to poor collection, most will be found floating in marine waters. This paper presents the results of a study of PET depolymerization by hydrolysis. We observed that marine water is a perfect reactant because it contains a multitude of metal ions that act as catalysts. A first-order kinetic model was developed and experimental data fitted to it. An activation energy of 73.5 kJ/mole and a pre-exponential factor of 5.33 × 107 h–1 were obtained. Considering that the global ocean is a huge batch reactor operating under isothermal conditions, the solution of the mathematical model shows that in tropical regions only 72 years is needed for total and only 4.5 years for 50% PET conversion.

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A sol–gel synthesis technique was employed for the preparation of anatase phase {001}-TiO2/Au hybrid nanocomposites (NCs). The scalable, schematic, and cost-efficient method was successfully modified using HF and NH4OH capping agents. The photocatalytic activity of the as-synthesized {001}-TiO2/Au NCs were tested over 2-cycle degradation of methylene blue (MB) dye and pharmaceutical active compounds (PhACs) of ibuprofen and naproxen under direct sunlight illumination at 35 °C and 44,000 lx. Transmission electron microscopy (TEM), high resolution transmission electron microscopy (HR-TEM), fast Fourier transform (FFT), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectroscopy (EDS), and ultraviolet–visible diffuse reflectance spectroscopy (UV–Vis DRS) were employed for the characterization of the as-prepared sample. The characterization results from the TEM, XPS, and XRD studies established both the distribution of Au colloids on the surface of TiO2 material, and the presence of the highly crystalline structure of anatase {001}-TiO2/Au NCs. Photodegradation results from the visible light irradiation of MB indicate an enhanced photocatalytic performance of Au/TiO2 NCs over TiO2. The results from the photocatalytic activity test performed under direct sunlight exposure exhibited promising photodegradation efficiencies. In the first cycle, the sol–gel synthesized material exhibited relatively better efficiencies (91%) with the MB dye and ibuprofen, while the highest degradation efficiency for the second cycle was 79% for the MB dye. Pseudo first-order photodegradation rates from the first cycle were determined to be comparatively slower than those from the second degradation cycle.

A series of solid acid catalyst of the Keggin-type 12-phosphotungstic acid, H3PW12O40, supported on ordered mesoporous silica MCM-41 were prepared by a simple and effective impregnation method. MCM-41 supports were synthesized in a relatively short time via a recently reported ultrasonic irradiation method. The synthesis sonication time has been systematically varied in order to investigate its influence on the structural order of the resulting materials. The prepared catalysts were characterized by nitrogen adsorption, X-ray diffraction, Raman spectroscopy and thermogravimetric analysis. The resulting materials exhibited hexagonally ordered meso structure, with high surface area of the order of several hundreds of m2g-1,relatively large pore volumes, with the pore diameter in the range of 2.19 to 2.41 nm and a corresponding pore wall thickness of over 1.67nm. The results have demonstrated that high quality MCM-41 materials can be synthesized via the ultrasonic irradiation in few tens of minutes, much shorter than the conventional synthesis methods. Despite their relatively high loading, all synthesized materials retained the characteristic MCM-41mesoporous structure after impregnation of the heteropolyacid active phase onto the inner pore surface, without crystallization, but preserving the Keggin structure as confirmed by Raman spectroscopy.

Presence of moisture is very important for vegetable oils and for corresponding biodiesel because it may cause some problems or accelerate some issues that cannot be ignored. One of the main hindrances of biodiesel is its hygroscopic nature, which accelerates the corrosion of the fuel system of the engines. Thus, this study aims to investigate the effects of moisture on corn biodiesel and its susceptibility to corrosion on different automotive materials such as copper and mild carbon steel. Static immersion tests in corn biodiesel (B100) with different water concentrations (100 ppm, 500 ppm, and 700 ppm) were carried out at 90°C for 1200 h, and the results were compared to that of commercial diesel fuel (B0). After immersion tests, the surface morphology was studied by scanning electron microscopy (SEM), and corrosion products were detected by X-ray diffraction (XRD). The total acid number (TAN) was used to evaluate the changes in acidity of fuel, before and after immersion tests. It was found that under experimental conditions, corn biodiesel is more corrosive than diesel fuel, and the moisture from corn biodiesel has a strong influence on corrosion rate on metals. Copper is more susceptible to corrosion in corn biodiesel than mild carbon steel.