Catalytic pulsed plasma treatment for organic micropollutants: unveiling the synergistic role of photocatalysts in radical generation and degradation mechanisms†

This work aims toward the remediation of multiple organic micropollutants simultaneously present in municipal wastewater. Catalytic pulsed plasma treatment (CPPT) coupled with TiO₂ and N-TiO₂ photocatalysts was employed to degrade naproxen (NPX), triclosan (TCS), and reactive red 180 (RR180). This study addressed a key challenge towards achieving Sustainable Development Goal (SDG) 6 for clean water and sanitation. The operating conditions were 23 kV at a pulse frequency of 33 Hz for a 50 mL sample volume. The synergy of photocatalysts with plasma was observed with N-TiO₂ reducing the treatment time for complete degradation by 50% as compared to the non-catalytic system. This improvement was due to enhanced radical generation, catalyst activation by UV-visible light, and increased surface area. The enhancement in radical generation noted was ∼85% for H₂O₂ and ∼100% for ˙OH. The role of SO₄˙⁻ in RR180 degradation was noted. The disc diffusion test showed no inhibition zone for NPX and TCS at 1 mg L⁻¹ and RR180 at 10 mg L⁻¹ within 8 min. The degradation yield increased by 25% compared to the non-catalytic system. The mineralization efficiency follows the order TCS > RR180 > NPX. Finally, CPPT demonstrates >99% degradation efficiency in the multipollutant system of real secondary treated wastewater, showcasing its broad applicability in diverse wastewater scenarios.