Elimination of Matrix Effects in Ionizing Radiation Treatment of Cephalosporin Wastewater by Pretreatment Coupling
Ionizing radiation (IR) is an emerging advanced oxidation process for degrading recalcitrant organic pollutants in water, but its efficiency is often hampered by matrix effects from coexisting substances in real wastewater. This study coupled three pretreatments—coagulation sedimentation, adsorption, and biological oxidation—with electron beam IR to treat a model cephalosporin wastewater containing cefotaxime sodium (CTX) and typical coexisting components. The results showed that all coupled systems significantly improved treatment performance compared to direct IR: COD removal increased by 19%–42% and CTX removal by 8.4%–19%. Under the tested conditions, the optimal coagulant was polymeric ferric sulfate (PFS), the optimal adsorbent was activated carbon, and the optimal aeration time for biological oxidation was 6 h. All three pretreatments reduced matrix effects, with adsorption, biological oxidation, and coagulation sedimentation lowering the matrix effect by 17%, 11%, and 9%, respectively. Quantum chemical calculations and LC-MS analysis predicted radical reaction sites on CTX and revealed five possible degradation pathways. The study demonstrates that pretreatment-IR coupling is an effective strategy to mitigate matrix effects and enhance the targeted degradation of antibiotics in complex wastewater matrices.