New Insights into the In Situ Fenton-like Process by Copper(II)-hydroxylamine Coupling: Reactive Species,...

Area of Science:

• Environmental Chemistry
• Oxidation Processes
• Catalysis

Background:

• The Cu-(II)/NH2OH system is investigated for pollutant degradation.
• Understanding the complex reaction pathways and influencing factors is crucial for effective wastewater treatment.

Purpose of the Study:

• To elucidate the mechanism of pollutant oxidation by the Cu-(II)/NH2OH system.
• To identify key factors affecting the process, including pH, oxygen, anions, and metal ions.
• To assess the role of hydroxylamine in the Fenton reaction and its potential toxicity.

Main Methods:

• Experiments were conducted using benzoate as a probe pollutant.
• Techniques included selective scavenger addition, electron paramagnetic resonance, NO(g) kinetics, and high-resolution mass spectrometry.
• The effects of pH, dissolved oxygen, hydrogen peroxide, chelating agents, anions, and transition metals were systematically studied.

Main Results:

• Acidification hindered the process, while high bicarbonate concentrations accelerated NH2OH consumption and pollutant oxidation.
• Molybdenum-(VI)-peroxo species interfered by consuming NH2OH.
• Hydroxylamine, though primarily forming gaseous products, exhibited toxicity at trace concentrations.

Conclusions:

• Hydroxylamine acts as a Cu-(II) reducing agent, initiating Fenton reactions via *in situ* H2O2 generation.
• NH2OH modifies the Cu-(I, II)/H2O2 Fenton mechanism, implicating reactive nitrogen species in pollutant abatement over HO• or Cu-(III).
• The system's efficiency and safety are influenced by various chemical species and reaction conditions, with NH2OH posing a toxicity risk.