Unparalleled photocurrent and dark radical conversions of natural nano-iron oxides versus synthetic ones: thousand-fold enhanced degradation of extra antibiotic resistant genes

Abstract

Antibiotic resistant genes (ARGs) have been widely detected in global rivers, lakes and oceans. Although nanoscale natural acrisol iron oxides (NNIOs) are ubiquitous in global aquatic environments, their photoelectric conversion efficiency and bactericidal and ARG removal are not well clarified. This study evaluated the photocurrent conversion and photocatalytic degradation of antibiotic-resistant bacteria and extracellular ARGs (eARGs) of two typical NNIOs (natural hematite and goethite) in comparison with their synthetic ones. It was found that NNIOs exhibit unparalleled and persistent photocurrent conversion versus the synthetic ones. NNIOs also had high dark radical conversion in contrast to little conversion of the synthetic ones. Owing to these unrivalled performance, NNIOs had significant advantages of killing bacteria over the synthetic ones. What is more important, thousand-fold higher degradation rates of eARGs were obtained by NNIOs than the synthetic ones under light or light–dark conditions. The residual eARG copies after synthesized hematite treatment were up to 17 400 times that of natural hematite groups, and this difference between synthetic and natural goethite was 1612 times. These novel findings imply that enough attention should be paid to the overlooked huge contribution of NNIOs to aquatic eARG elimination and reduction of antibiotic resistance risk. The mechanisms of incomparable photoelectric and dark radical conversions of NNIOs and their ultraefficient degradation of eARGs deserve further study.