Oxolinic acid photo-oxidation using immobilized TiO(2)

Area of Science:

• Environmental Chemistry
• Photocatalysis
• Water Treatment

Background:

• Antibiotic contamination in water poses significant environmental and health risks.
• Oxolinic acid (OA) is a widely used antibiotic whose environmental persistence is a concern.
• Advanced Oxidation Processes (AOPs) are effective for degrading recalcitrant organic pollutants.

Purpose of the Study:

• To investigate the photocatalyzed oxidation of oxolinic acid (OA) using immobilized TiO2.
• To evaluate the degradation efficiency and kinetics of OA under specific reaction conditions.
• To assess the removal of antibacterial activity during the process.

Main Methods:

• Utilized an annular reactor with titanium dioxide (TiO2) immobilized on sintered glass cylinders (SGC).
• Conducted experiments with oxolinic acid (OA) solutions at pH 9, under oxygen bubbling, and black light irradiation.
• Monitored degradation using Chemical Oxygen Demand (COD), Total Organic Carbon (TOC), and Average Oxidation State (AOS) calculations.
• Assessed antibacterial activity using the inhibition halo technique against Escherichia coli.

Main Results:

• Achieved a one-order-of-magnitude decrease in OA concentration within 60 minutes, with complete elimination at 100 minutes.
• Reduced Total Organic Carbon (TOC) by 54%, indicating significant mineralization.
• Average Oxidation State (AOS) reached +3, suggesting the formation of low molecular weight carboxylic acids.
• Observed a decrease in antibacterial activity correlating with OA removal, with no activity from intermediates.

Conclusions:

• Photocatalyzed oxidation with immobilized TiO2 is an effective method for degrading oxolinic acid (OA).
• The reaction follows Langmuir-Hinshelwood kinetics, highlighting the importance of the adsorption step.
• The process successfully eliminates OA and its associated antibacterial activity, producing benign byproducts.