Nowadays, a continuously worldwide concern for development of process to produce ultra-low sulfur and nitrogen fuels have been emerged. Typical hydrodesulfurization and hydrodenitrogenation technology deals with important difficulties such as high pressure and temperature operating condition, failure to treat some recalcitrant compounds and limitations to meet the stringent environmental regulations. In contrary an advanced oxidation process that is ultrasound assisted oxidative desulfurization and denitrogenation satisfies latest environmental regulations in much milder conditions with more efficiency. The present work deals with a comprehensive review on findings and development in the ultrasound assisted oxidative desulfurization and denitrogenation (UAOD) during the last decades. The role of individual parameters namely temperature, residence time, ultrasound power and frequency, pH, initial concentration and types of sulfur and nitrogen compounds on the efficiency are described. What's more another treatment properties that is role of phase transfer agent (PTA) and solvents of extraction step, reaction kinetics, mechanism of the ultrasound, fuel properties and recovery in UAOD are reviewed. Finally, the required future works to mature this technology are suggested.

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Various nanocomposites of TiO2–ZnO, TiO2–ZnO/CS, and TiO2–ZnO/CS–Gr with different molar ratios were synthesized by sol–gel and ultrasound-assisted methods and utilized under UV irradiation to enhance the photocatalytic degradation of tetracycline. Characterization of prepared materials were carried out by XRD, FT-IR, FE-SEM, EDX and BET techniques. The TiO2–ZnO with the 1:1 molar ratio supported with 1:2 weight ratio CS–Gr (T1‒Z1/CS1‒Gr2 sample) appeared as the most effective material at the optimized operational conditions including the tetracycline concentration of 20 mg/L, pH = 4, catalyst dosage of 0.5 g/L, and 3 h of irradiation time. As expected, the graphene had a significant effect in improving degradation results. The detailed performances of the T1‒Z1/CS1‒Gr2 were compared with ternary nanocomposites from EDX and BET results as well as from the degradation viewpoint. This novel photocatalyst can be effective in actual pharmaceutical wastewater treatment considering the applied operational parameters.

A CuO-ZnO@graphitic carbon nitride (Cu/Zn/g) triplex heterojunction nanocomposite was prepared through a multistep ultrasound-assisted hydrothermal procedure. XRD, SEM, EIS, EDX, BET, FT-IR, EDS, UV−Vis, TEM, PL, and transient photocurrent techniques were employed for catalyst characterization. The XRD profiles demonstrated the formation of the ZnO wurtzite phase and CuO monoclinic phase in the samples. It was revealed by the SEM and TEM images that the Cu/Zn/g catalyst is composed of g-C 3 N 4 nanosheets decorated with ZnO nanorods and CuO nanospheres. According to the results obtained from the ultrasound-assisted desulfurization experiments, almost complete sulfur removal was achieved using Cu/Zn/g at a photocatalyst dose of 0.2 g/L, initial dibenzothiophene (DBT) concentration of 250 ppm, and H 2 O 2 loading of 250 ppm at 298 K within 60 min of treatment in the presence of ultrasonic waves (80 W/m 2 ) and light irradiation (150 W). Upon g-C 3 N 4 incorporation, considerable enhancement in desulfurization efficiency was achieved due to the significantly higher surface area and lower recombination rate of electron−hole pairs. At optimal experimental conditions, a 99.1% desulfurization rate was achieved using Cu/Zn/g with a g-C 3 N 4 concentration of 10 wt %, compared to the pristine CuO-ZnO catalyst (76.2%). Moreover, the as-synthesized photocatalyst showed excellent stability after five cycles. Kinetic studies also confirmed that the desulfurization procedure could be fitted to a pseudo-firstorder kinetic model. Finally, the product of DBT oxidation was identified by the gas chromatography−mass spectrometry analysis. It was revealed on the basis of the photoelectrochemical and trapping experiments that the photoinduced holes and •OH radicals are responsible for desulfurization and the charge carrier migration pattern is dictated by the dual Z-scheme approach, resulting in the enhanced redox potential of the as-synthesized catalyst and therefore outstanding photocatalytic performance. ■ HIGHLIGHTS• Cu/Zn/g ternary composite was prepared and used for sono-photocatalytic desulfurization. • Complete desulfurization was achieved using a combined approach of the dual Z-scheme Cu/Zn/g photocatalyst, US, and visible light irradiation within 60 min. • The fabricated catalyst showed excellent catalytic performance and stability after five cycles. • Photogenerated charge carriers and •OH radicals are responsible for the oxidative treatment.