Robust decomplexation of Cu(II) complexes in excessive ligand environments by Mn(II)/PMS process: Ligand...

Area of Science:

• Environmental Chemistry
• Catalysis
• Wastewater Treatment

Background:

• Copper-ligand complexes are common pollutants in industrial wastewater.
• Existing methods struggle with non-stoichiometric complexes, especially with excess ligands.
• Efficient decomplexation is crucial for effective wastewater remediation.

Purpose of the Study:

• To investigate the Mn(II)/peroxymonosulfate (PMS) process for eliminating Cu(II)-ligand complexes.
• To evaluate the process's efficacy in environments with excessive ligand concentrations.
• To elucidate the underlying decomplexation mechanisms.

Main Methods:

• Utilized the Mn(II)/PMS catalytic oxidation system.
• Employed Cu(II)-EDTA as a model complex to test decomplexation efficiency.
• Conducted mechanistic studies involving oxidation species characterization and product analysis.

Main Results:

• Achieved 90% decomplexation of Cu(II)-EDTA within minutes, even at a 2:1 EDTA:Cu ratio.
• Demonstrated superior performance compared to UV/H2O2, UV/PDS, and Co2+/PMS methods.
• Identified a non-radical pathway involving high-valence metals and singlet oxygen for EDTA decarboxylation.

Conclusions:

• The Mn(II)/PMS process is a robust and efficient solution for treating Cu(II)-ligand complexes in wastewater, including ligand-rich scenarios.
• The system operates via dual mechanistic regimes, adapting to ligand-deficient and ligand-rich conditions.
• This study presents a practical strategy for industrial wastewater treatment, addressing challenges posed by non-stoichiometric copper complexes.