Comparison between UVA- and zero-valent iron-activated persulfate processes for degrading propylparaben

Area of Science:

• Environmental Chemistry
• Water Treatment Technologies
• Advanced Oxidation Processes

Background:

• Conventional wastewater treatments fail to remove parabens, leading to environmental contamination.
• Parabens pose risks to aquatic ecosystems and human health.
• Persulfate (PS)-driven advanced oxidation technologies (AOTs) offer a promising alternative for paraben removal.

Purpose of the Study:

• To investigate the degradation of propylparaben (PrP) using UVA- and zero-valent iron (ZVI)-activated persulfate.
• To evaluate the impact of operational parameters like PS concentration, irradiance, and ZVI dosage on PrP removal efficiency.
• To assess the toxicity of PrP degradation products and the influence of water matrix on the AOTs' performance.

Main Methods:

• Doehlert experimental design to optimize PS concentration, irradiance, and ZVI dosage.
• UVA/PS and ZVI/PS advanced oxidation processes for PrP degradation.
• Liquid chromatography-tandem mass spectrometry (LC-MS/MS) for identifying degradation products.
• ECOSAR (Ecological Structure Activity Relationships) modeling for toxicity assessment.
• Evaluation of water matrix effects, including MBR effluent.

Main Results:

• UVA/PS system achieved PrP degradation rates (k) of 0.0053-0.0192 min⁻¹ and 37.9-77.3% removal.
• ZVI/PS process demonstrated significantly faster degradation (0.3304 < k < 0.9212 min⁻¹) with >97.5% removal.
• Optimal ZVI dosage was below 40 mg L⁻¹; higher doses hindered degradation.
• Degradation products were predicted to be less toxic to aquatic organisms (fish, daphnia, algae).
• ZVI/PS process was more affected by MBR effluent matrix but still outperformed UVA/PS (t½: 65.4 min vs. 276.1 min).

Conclusions:

• Both UVA/PS and ZVI/PS are effective AOTs for propylparaben removal.
• ZVI/PS offers a highly efficient and rapid method for paraben degradation.
• The ZVI/PS process shows potential for wastewater treatment, though matrix effects require consideration.
• The generated degradation products exhibit lower ecotoxicity, suggesting a safer environmental outcome.