PSO-SVM optimized dielectric barrier discharge plasma for energy-efficient degradation of sulfamethoxazole in wastewater.

Conventional treatment methods struggle to effectively eliminate sulfamethoxazole (SMX) from wastewater due to its persistent aromatic structure and sulfonamide moiety, while existing advanced oxidation processes often suffer from high energy consumption and inadequate degradation pathway control. This study demonstrates an advanced approach for SMX degradation in aqueous systems through dielectric barrier discharge (DBD) plasma technology synergistically integrated with COMSOL multiphysics simulation and particle swarm optimization-support vector machine (PSO-SVM) modeling. Computational simulations revealed that the DBD plasma generates a diffuse arc (D-A) mode electric field with Penning ionization effects, where primary reactive species formation predominantly occurs within the sheath layer. Under optimized operational parameters (input power: 50 W, pH 7, conductivity: 3.16 μS/cm, initial concentration: 10 mg/L, the carrier gas: air), the system achieved an exceptional SMX removal efficiency of 99.82 %, corresponding to a constant reaction rate of 0.3087 min-1. The machine learning-optimized process simultaneously enhanced energy yield by 18.11 mg/(kW·h) and improved energy utilization efficiency by 15.11 %. Notably, the system maintained robust performance (>75 % SMX removal) in the presence of competing inorganic anions (NO3-, HCO3- and Cl-). Mechanistic investigations combining DFT, EPR and UPLC-MS/MS elucidated that •OH, O2•-, 1O2, •NO2 and ONOOH preferentially attack the electrophilic N(4), N(7), and N(17) sites, initiating sequential diazotization and nitration pathways. Practical validation using hospital wastewater demonstrated significant removal of COD (56.17 %) and TOC (40.16 %), while effectively suppressing antimicrobial resistance genes. This work establishes PSO-SVM optimized DBD plasma as a sustainable and intelligent solution for pharmaceutical wastewater remediation.