Removal of trace naproxen from aqueous solution using a laboratory-scale reactive flow-through membrane electrode

Area of Science:

• Environmental Chemistry
• Electrochemistry
• Water Treatment

Background:

• Naproxen (NPX) is a common pharmaceutical pollutant in aquatic environments.
• Effective removal of NPX is crucial for environmental protection and public health.
• Electrochemical methods offer a promising approach for degrading persistent organic pollutants.

Purpose of the Study:

• To investigate the kinetics and mechanisms of naproxen degradation using a reactive flow-through membrane anode.
• To determine the optimal conditions for efficient NPX removal and low energy consumption.
• To assess the influence of operational parameters and water matrix on degradation performance.

Main Methods:

• Electrochemical degradation experiments were conducted using a flow-through membrane anode.
• Naproxen concentrations ranged from 20-200 μg/L.
• Kinetic analysis followed pseudo-first-order reaction kinetics.
• Parameters optimized included current density, pump rotational speed, and pH.
• The effect of humic acid as a water matrix component was evaluated.

Main Results:

• Naproxen degradation followed pseudo-first-order kinetics with a rate constant (k) of 0.649 min⁻¹ under optimal conditions (50 μg/L NPX).
• Optimal conditions yielded an energy consumption (EEO) of 0.744 Wh/L.
• Higher current density, faster pump speed (up to 600 rpm), and lower pH (down to 3.0) significantly enhanced NPX degradation and reduced energy consumption.
• Degradation efficiency and energy consumption remained stable across NPX concentrations (20-200 μg/L) and in the presence of humic acid (1.0-10.0 mg/L).
• Major degradation pathways included demethylation, decarboxylation, and subsequent ring cleavage.

Conclusions:

• The flow-through membrane anode is highly effective for the electrochemical degradation of trace naproxen in aqueous solutions.
• Optimized electrochemical treatment offers an energy-efficient method for removing NPX.
• The process demonstrates robustness against varying NPX concentrations and the presence of natural organic matter.