Visible light-driven photocatalytic permanganate activation for efficient water purification

Area of Science:

• Environmental Chemistry
• Materials Science
• Chemical Engineering

Background:

• Permanganate (PM)-based advanced oxidation processes (AOPs) show promise for water purification but face challenges with energy sources and catalyst recovery.
• Photocatalytic activation of PM using solar irradiation is attractive but requires efficient energy utilization and catalyst management.

Purpose of the Study:

• To develop a visible light (VL)-driven photocatalytic PM activation strategy for efficient organic pollutant degradation.
• To establish a new platform technology for water purification by coupling PM oxidation with photocatalysis.
• To investigate the underlying mechanisms and design a practical reactor for continuous water treatment.

Main Methods:

• Visible light (VL) irradiation was used to activate permanganate (PM) in the presence of micron-bismuth vanate (BiVO4) photocatalyst.
• Degradation of ciprofloxacin (CIP) was monitored, and reaction kinetics were determined.
• Spectroscopic investigations (physical, theoretical, in situ) were employed to elucidate the degradation mechanism.
• A horizontal-flow photocatalytic reactor was designed and tested for continuous water treatment capacity.

Main Results:

• The VL-driven photocatalytic PM activation rapidly and completely degraded ciprofloxacin (CIP) within 7 minutes.
• The degradation rate constant was significantly higher (0.52 min⁻¹) compared to PM oxidation alone and VL-assisted PM oxidation.
• Favorable adsorption of PM on BiVO4 enhanced photogenerated electron utilization, leading to reactive manganese and oxygen species formation.
• A continuous flow reactor achieved a water treatment capacity of 20 L/h under outdoor solar irradiation.

Conclusions:

• The developed strategy synergistically combines PM oxidation and photocatalysis, addressing limitations of individual methods.
• This platform technology demonstrates broad applicability across various photocatalysts, pollutants, pH conditions, and real water systems.
• The study offers a robust and efficient AOP for water purification, providing new insights into photocatalytic PM activation.