The Oxidation and Immobilization of As(III) by Colloidal Ferric Hydroxide in the Concomitant Pollution of Oxytetracycline

Abstract

The concomitant pollution of arsenic and antibiotics has commonly occurred in the environments recently, the behaviors of which may be different from single existence. Colloidal ferric hydroxide (CFH) is ubiquitous, existing in surface waters, seawaters, sediments, and paddy soils. In this study, the interaction between oxytetracycline (OTC) and CFH facilitated OTC degradation and reduced Fe(III) to Fe(II). In oxic conditions, the reactions between dissolved oxygen (DO) and Fe(II) generated reactive oxygen species (ROS). • OH and O 2•− were the main free radicals through electron paramagnetic resonance (EPR) measurement, and 8.1 ± 0.5 μM • OH was detected after 48 h of reaction. Quenching experiments indicated that • OH had dominated the oxidation of As(III). Furthermore, ferric arsenate formed after the oxidation of As(III) to As(V), which greatly decreased As(III) risks in the environment. The transformation of As(III) was also observed with other iron oxides or different antibiotics. The results of this study proved the facilitation of residual antibiotics in the redox process of iron oxides and transformation of co-existing pollutants, which extended our understanding on the roles of organic pollutants in combined contamination.

Identification of Superoxide Contribution through the Quenching Method and Model System

“…Superoxide (O 2 •– ) is a ubiquitous reactive oxygen species in the environment, − playing a crucial role in various biochemical processes. It influences biological cell activity, facilitates metal recycling, and promotes pollutant reduction. ,, O 2 •– exhibits both oxidizing and reducing properties ( E 0 (O 2 •– /H 2 O 2 ) = +0.91 V) and reducing properties ( E 0 (O 2 /O 2 •– ) = −0.18 V), , allowing it to engage in single electron transfer, deprotonation, and nucleophilic substitution reactions with organic components. , O 2 •– is detected in different advanced oxidation processes, particularly in heterogeneous systems, and numerous studies have highlighted its significant contribution to pollutant degradation. − The contribution of O 2 •– is usually identified by the quenching method, − resulting from the apparent inhibition caused by the quenching of p -benzoquinone ( p -BQ) or superoxide dismutase (SOD). However, since O 2 •– is not highly reactive, quenching in complex systems is susceptible to interference from highly reactive species.…”

Highly Dispersed Magnetite Nanoparticles on Biochar with Sulfonation Modification for Simultaneous Removal of Arsenite and Tetracycline from Aqueous Solutions: Performance and Mechanistic Insight

“…The increasing toxicity and complexity due to the combined pollution of heavy metals and antibiotics in aqueous media, arising from worldwide urbanization and industrialization, is causing public concern over environmental issues. − As a result of natural and anthropogenic activities including waste discharge, rock weathering, and mining, high levels of arsenic (up to 1350 μg/L) have been frequently detected in groundwater in the northwest of China, for example, Inner Mongolia, Xinjiang Uighur, and Guizhou province, which markedly exceed the detection limit (10 μg/L) set by the World Health Organization (WHO) . Meanwhile, in the rural areas contaminated by arsenic, pharmaceutical antibiotics (e.g., tetracycline) used for animals and humans to treat infectious diseases are often directly released into domestic sewage, which will be reutilized for irrigation of farmland and inevitably lead to the antibiotic pollution of groundwater. , Excessive and long-term exposure to heavy metals and antibiotics can adversely affect the growth of animals and plants and even cause a series of health-related problems such as cancer, neurotoxicity, and chronic kidney disease through migration and the food chain. − Recent studies have demonstrated that the presence of tetracycline could reduce the immobility of arsenic in aqueous solutions, and meanwhile, the presence of high concentrations of arsenic also inhibited the removal of tetracycline. ,, Undoubtedly, their interactive behavior adversely affects the overall treatment efficiency.…”