Regulating Microbial-Driven Iron-Based Nanoparticles for Enhanced Pharmaceutical Contaminant Remediation

Abstract

The persistence of organic contaminants in aquatic environments poses serious threats to living organisms, while concentrations of highly toxic contaminants are often several orders of magnitude lower than those of coexisting interferents, and this presents a significant challenge to achieving available removal. Microbially synthesized iron-based nanoparticles (nFe) possess a characteristic biomass coating (nFe-OM) that may confer effective removal toward certain contaminants. However, the role of environmental factors in tuning the nFe-OM composition for contaminant removal remains underexplored. In this study, the modified nanoparticles feature distinct phases [nano zerovalent iron (Fe⁰), Fe₂O₃, FeOOH, and Fe₃O₄] and functional groups (−COOH, −OH, and −C═C). Four pharmaceutical contaminants─quinolyl (chloroquine phosphate, DIP), ribofuranyl (ribavirin, RIB), piperazinyl (rifampicin, RIF), and progesterone (dexamethasone, DEX)─are selected to evaluate selective removal mechanisms: RIB, DIP, and RIF exhibit a stronger affinity for carboxyl (−COOH) and hydroxyl (−OH) groups on nFe-OM synthesized by MR-1 (M-nFe-OM), while halogenated hydrocarbons (DIP/DEX) undergo additional reactions with conjugated π systems. In aquaculture wastewater experiments, the M-nFe-OM achieves a 197.5–215 mg/g removal capacity (960 mL/day) and retained its performance over 4–6 cycles. This work demonstrates a tunable microbial strategy for engineering multifunctional nFe-OM, offering a green and effective solution for pharmaceutical contaminant remediation.