F.Z. Yehia

Ultrasonic assisted-Fenton-like degradation of nitrobenzene at neutral pH using nanosized oxides of Fe and Cu.

Ultrasonic-assisted heterogeneous Fenton reaction was used for degradation of nitrobenzene (NB) at neutral pH conditions. Nano-sized oxides of α-Fe2O3 and CuO were prepared, characterized and tested in degradation of NB (10 mg L(-1)) under sonication of 20 kHz at 25 °C. Complete degradation of NB was effected at pH 7 in presence of 10 mM H2O2 after 10 min of sonication in presence of α-Fe2O3 (1.0 g L(-1)), (k=0.58 min(-1)) and after 25 min in case of CuO (k=0.126 min(-1)). α-Fe2O3 showed also effective degradation under the conditions of 0.1 g L(-1) oxide and 5.0 mM of H2O2, even though with a lower rate constant (0.346 min(-1)). Sonication plays a major role in enhancing the production of hydroxyl radicals in presence of solid oxides. Hydroxyl radicals-degradation pathway is suggested and adopted to explain the differences noted in rate constants recorded on using different oxides.

Extending the working pH of nitrobenzene degradation using ultrasonic/heterogeneous Fenton to the alkaline range via amino acid modification.

Oxides of iron, α-Fe2O3 (I), and copper, CuO (II) prepared by usual precipitation method without surfactant were used at room temperature in the process of nitrobenzene (10mgL(-1)) degradation at different pH values with ultrasonic at 20kHz. The degradation was complete in 20 and 30min for (I) and (II), respectively in the pH range 2-7 using1.0gL(-1) of solids and 10mM of H2O2. A remarkable decrease in degradation efficiency was recorded on increasing the pH to values higher than the neutral range. This loss in efficiency was cancelled to a great extent through modifying the used oxides with amino acids. Arginine showed higher improving effect to (II) (1:1 weight ration) than glycine or glutamic acid. Modification of both oxides with increasing amounts of arginine increased the degradation efficiency of (I) in a more regular way than in case of (II). However, the extent of improvement due to amino acid modification was higher in case of (II) because of its originally low degradation efficiency in strongly alkaline media.

Fe3O4-boosted MWCNT as an efficient sustainable catalyst for PET glycolysis

This study focuses on the utilization of Fe3O4-boosted multiwalled carbon nanotubes (MWCNT) as a sustainable, easily recoverable and a robust catalyst in the glycolysis of PET. A maximum yield (100%) of bis(2-hydroxyethyl)terephthalate (BHET) was achieved using Fe3O4-boosted MWCNT, which was higher than any other catalyst used in PET glycolysis with regard to the BHET yield. The extraordinary performance of the prepared Fe3O4-boosted MWCNT is attributed to the synergetic effect induced by both magnetite and MWCNT in the catalytic glycolysis of PET. With regard to sustainability, the catalyst endures the glycolysis process conditions for at least eight sequential runs. The reaction mechanism of PET glycolysis using Fe3O4-boosted MWCNT has also been proposed.

Role of surface modification of some metal oxides with amino acids in upgrading the sonocatalytic degradation of nitrobenzene

AbstractThe influence of surface modification of some metal oxides (Fe2O3, CuO, NiO, and CO3O4) with amino acids was investigated in the sonocatalytic degradation of nitrobenzene (NB). Glycine, arginine, and glutamic acid were used as surface modifiers. This modification resulted in a considerable enhancement of sonochemical degradation of NB at pH higher than 7 with respect to the pristine catalysts before modification. Catalysts modified with arginine exhibited the highest degradation extent. The enhanced degradation efficiency was attributed to the promoted coupling via electrostatic attraction between the negatively charged NB molecules and the positively charged arginine layer on the surface of Fe2O3, CuO, NiO, and Co3O4. The attraction capability at all modified metal oxides increased via secondary forces such as hydrogen bonding, n–π and π–π interactions.