Degradation performance and mechanism of penicillin G in aqueous solution by ionizing radiation

Abstract

Penicillin G (PG), a frequently detected β-lactam antibiotic in aquatic environment, has attracted extensive concerns because of its extensive application and potential to develop antimicrobial resistance. In this study, gamma radiation was used to degrade PG in water. The main influencing factors, such as initial PG concentration, pH value, absorbed dose, as well as water matrix (inorganic anions and organic matters) were investigated. Results showed that lower initial concentration, acidic condition (pH = 5.57), and higher absorbed dose was conducive to PG degradation. Besides, NO3−, HCO32−, SO42− and HPO42− had negative influence on PG degradation, while Cl− had positive influence. Organic matters had negative influence. Twelve transformation intermediate products (TPs) were identified during PG degradation. Together with the density functional theory (DFT) calculation, four possible pathways of PG degradation were proposed. The results of antibacterial activity test demonstrated that the transformation of PG to TPs eliminated the antibacterial activity. Notably, except some para-modified products of PG, the toxicity of other TPs was reduced PG degradation. Moreover, no potential risk of bacterial mutagenicity during PG degradation was observed. In summary, ionizing radiation has good performance in PG degradation in the real wastewater.