From Molecules to the Field: Iron Oxides Controlling Pharmaceutical Fate and Remediation

Abstract

Iron oxide (nano)minerals are abundant and reactive components of natural systems, exerting a profound influence on the environmental fate of contaminants. Among these, pharmaceutical pollutants have gained increasing attention due to their ubiquitous presence in aquatic and terrestrial environments, their persistence, and their potential to harm ecosystems and human health, particularly through contributions to antimicrobial resistance.

Iron oxides play a dual role in mitigating pharmaceutical pollution: they serve as adsorptive surfaces and as redox-active materials capable of transforming pharmaceutical compounds. Adsorption is governed by the affinity between pharmaceutical functional groups and specific iron oxide surface sites, while redox-active pharmaceuticals may undergo abiotic transformations upon electron transfer with Fe(III) or mixed-valent (Fe(II)–Fe(III)) minerals. These interactions can yield breakdown products with altered bioactivity and toxicity, adding complexity to environmental risk assessments. However, these processes remain poorly understood due to experimental limitations and the absence of reliable predictive models. Predicting pharmaceutical behavior under environmentally relevant conditions requires bridging multiple spatial and temporal scales.

In this Account, we provide a multiscale evaluation of how iron oxides influence the fate and remediation potential of pharmaceutical pollutants, integrating findings from experimental and modeling studies at molecular, interface, pore, column, and field levels. We also explore how Machine Learning can link across scales and uncover emergent patterns in complex data sets. Environmental factors, including solution chemistry, mineral properties, and co-occurring components, significantly influence these interactions.

This approach allows us to identify key knowledge gaps, draw connections between molecular-scale reactivity and macroscale environmental processes, and highlight opportunities for developing predictive tools for environmental risk assessment. The insights gained extend beyond pharmaceuticals to a wide range of emerging organic contaminants. Advancing this field requires interdisciplinary collaboration at the intersection of molecular geochemistry, environmental materials science, mineralogy, hydrology, and microbiology.