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

•Combined US/heterogeneous Fenton can be used for NB degradation in alkaline media.•Amino acids play the major role in extending the pH of treatment.•Hydration characteristics of amino acids are the key of this role.•The higher the IEP of the amino acid the higher its improving effect.•The specific surface area of oxides has a detrimental role.

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 (10 mg L−1) degradation at different pH values with ultrasonic at 20 kHz. The degradation was complete in 20 and 30 min for (I) and (II), respectively in the pH range 2–7 using1.0 g L−1 of solids and 10 mM 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.

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