Energy‐Efficient Degradation of Sulfamethoxazole in Water Using Nanosecond‐Pulsed Underwater Plasma Bubbles

ABSTRACT Non‐thermal plasma‐liquid systems provide a promising route for water treatment via reactive oxygen and nitrogen species, though achieving high efficiency with low energy input remains challenging. A nanosecond‐pulsed underwater plasma bubble reactor was developed for efficient sulfamethoxazole degradation, achieving ~90% removal within 20 min and a high energy yield of ~860 mg·kWh⁻¹. Optical emission spectroscopy indicated enhanced oxygen‐related reactive species under air and O 2 plasmas, correlating with improved degradation performance. Solution chemistry showed increased oxidation‐reduction potential and acidification during treatment. Electron spin resonance confirmed short‐lived radicals (OH, ONOO⁻) and long‐lived species (H 2 O 2 , NO 2 ⁻, NO 3 ⁻). Mechanistic analysis suggests that indirect oxidation pathways dominate via hydroxylation, bond cleavage, and aromatic ring opening, highlighting the importance of plasma chemistry regulation and reactor design.