Degradation of acetaminophen in fresh urine by periodate: Mechanisms, influencing factors and toxicity assessment

The efficient utilization of urine and reducing environmental pollution require the selective removal of pharmaceuticals from fresh urine (FU). Though advanced oxidation processes show promise, they often fail in FU due to its complex matrix. This study introduces a novel approach using periodate (PI) without externally added activators for the targeted degradation of acetaminophen (ACE) in FU. The results reveal that PI addition significantly enhances ACE removal. The degradation rate of ACE positively correlates with increased PI concentration within the range of 0.5 - 4 mmol·L⁻¹. Optimal degradation conditions are observed under weakly acidic to neutral pH levels. The process demonstrates robust performance across a broad concentration range of ACE (3 - 9 μmol·L⁻¹), with ACE removal efficacy remaining stable under batch PI addition ( n = 1 - 4). The phosphate in FU promotes the activation of PI, while other coexisting urinary constituents such as such as urea, citrate, Ca²⁺, Mg²⁺, and SO₄²⁻ does not adversely affect ACE elimination, indicating good anti-interference properties. Interestingly, elevated Cl⁻ levels marginally enhance ACE removal. Singlet oxygen was identified as the primary reactive species responsible for ACE degradation, as evidenced by scavenging experiments, probe analysis, and electron paramagnetic resonance spectroscopy. Further analysis through three-dimensional fluorescence spectroscopy revealed the formation of fluorescent degradation products with increased intensity. Potential degradation pathways of ACE were proposed based on the identification of degradation intermediates. Toxicity assessments of the PI/FU system indicate a detoxification effect during ACE degradation, highlighting the system's potential for broader application in various pharmaceuticals. • Periodate can selectively remove ACE from fresh urine without any extra activator. • Singlet oxygen was the main reactant for ACE removal. • Chloride and phosphate accelerate ACE decomposition. • The elimination of ACE was minimally affected by other urine components. • Toxicity decreased after periodate treatment.