The soil environment is an important sink for
penicillin antibiotics released from animal
manure and
wastewater, but the
mineral-catalyzed transformation of
penicillins in soil has not been well studied. To simulate this environmental process, we systematically investigated the behavior of
penicillin G and
amoxicillin, the two most widely-used
penicillin antibiotics, in the presence of
goethite and
metal ions. The results demonstrated that Zn
ions significantly promoted the hydrolysis of
penicillins in
goethite suspensions, as evidenced by the degradation rate nearly 3 orders of magnitude higher than that of the non-Zn-containing control. The spectroscopic analysis indicated that the specific complexation between
penicillins, adsorbed Zn, and
goethite was responsible for the enhanced degradation. Metastable interactions, involving hydrogen bonds between carbonyl groups in the β-
lactam ring and the double/triple
hydroxyl groups on
goethite surface, and coordination bonding between carboxyl groups and surface irons were proposed to stabilize the ternary reaction intermediates. Moreover, the surface
zinc-hydroxide might act as powerful nucleophile to rapidly
rupture the β-
lactam ring in
penicillins. This study is among the first to identify the synergic roles of Zn ion and
goethite in facilitating
penicillin degradation and provides insights into β-
lactam antibiotics to assess their environmental risk in soil.