Aimed at catalytic oxidative desulfurization (cat-ODS) of sulfur-containing aromatic compounds (SAs) and catalytic oxidative denitrogenation (cat-ODN) of nitrogen-containing aromatic components (NAs) to control air pollution, we successfully designed and synthesized a new green catalyst (named as TBAPMo11Cu@CuO) based on quaternary ammonium salt of copperII-monosubstituted phosphomolybdate [(n-C4H9)4N]­[PMo11CuO39] (TBAPMo11Cu) and copper oxide (CuO) via a sol–gel method. Cat-ODS and cat-ODN processes of SAs (thiophene (Th) and dibenzothiophene (DBT)), NAs (pyridine (Py) and carbazole (CBZ)) were carried out using hydrogen peroxide green oxidant and poly­(ethylene glycol) (PEG-200), which is considered as a green extractant over a TBAPMo11Cu@CuO catalyst. This new catalyst demonstrated a superb catalytic activity in the oxidation of SAs and NAs and long-term stability for producing ultraclean fuels: 97, 98, 99, and 98% values of conversion were obtained for Th, DBT, Py, and CBZ, respectively, at 35 °C. The results proved that Th and DBT were converted to the corresponding sulfoxides and sulfones, while Py and CBZ were oxidized to the corresponding N-oxides. Accordingly, the oxidized product of CBZ was identified as carbazole-9-carbaldehyde. Also, the removal of a considerable amount of Th, DBT, Py, and CBZ is possible via catalytic oxidation–extraction; however, simple solvent extraction (using methanol, ethanol, and acetonitrile) was inadequate for deep denitrogenation and desulfurization. TBAPMo11Cu@CuO as a catalyst indicated excellent reusability for five oxidation cycles. The high performance of TBAPMo11Cu@CuO/H2O2/PEG-200 can prove it as a promising green method for fuel purification.

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In this study, (C 4 H 9) 4 NPZnW 11-TiO 2 /PANI was synthesized as an efficient catalyst for dye decolorization of C 16 H 18 ClN 3 S (MB) from aqueous solution. The catalyst was successfully prepared using the reaction of quaternary ammonium salt of zinc (II)substituted Keggin-type polyoxometalate [(C 4 H 9) 4 N]PZnW 11 O 39 , titanium dioxide (TiO 2), and polyaniline (PANI) at room temperature under sonication conditions. Response surface methodology (RSM) was used to obtain maximum dye degradation and to determine the significance of the variables on the decolorization system under static conditions. The main parameters affecting decolorization efficiency on dye degradation, including process temperature (25-35°C), catalyst dosage (0.001-0.006 gr), and reaction time (5-15 minutes), were investigated in detail. The optimum decolorization conditions were identified to be a temperature of 30°C, catalyst dosage of 0.006 gr, and 14 minutes process time, giving an experimental dye removal value of 89.1%. The high regression coefficient between the variables and the response (R 2 = 0.9642) displayed a good evaluation of the experimental results by polynomial regression model.

In this research, zinc (II)-substituted Keggin-type polyoxometalate [(C 4 H 9 ) 4 N] PZnW 11 O 39 (PZnW 11 ) was prepared and stabilized on the modified graphene oxide (m-GO) for removal of methyl red (MR) dye from aqueous solution. The maximum dye degradation and significance of variables on the decolorization system in static conditions were determined using response surface methodology (RSM). The main variables affecting the decolorization performance on dye decolorization, including system temperature (25-40 C), catalyst amount (0.001-0.005 g), and irradiation time (5-25 min), were evaluated. The optimum temperature, catalyst applying amount, and irradiation time were identified as 35 C, 0.003 g, and 20 min, respectively, and the experimental dye removal value was 96.8%. The high regression coefficient between the response and the variables (R 2 = 0.9335) showed a good investigation of the experimental results by regression-based polynomial model. In comparison with the previously reported photocatalytic decolorization systems, the dye removal system suggested in this work is quick, easy and involves a small amount of catalyst. Polyoxometalate-based photocatalyst (PZnW 11 /m-GO) shows potent visible-light photocatalytic activity for the decolorization of methyl red dye, due to the generates the strong oxidants hydroxyl radical (OH) and superoxide anion radical (O 2 À ) via photoelectrochemical decomposition of H 2 O and O 2 in the presence of visible light irradiation. Efficient decolorization and degradation of organic contaminants by synthesized catalyst PZnW 11 /m-GO suggest its potential for real industrial applications in removal of synthetic dye wastewater.