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Adsorption of Selective Serotonin Reuptake Inhibitor Antidepressant Drugs from Aqueous Solution by Polystyrene Microplastics: Experimental Investigation and Molecular Dynamic Simulation
Summary
Tiny plastic particles (microplastics) floating in water can act like sponges, soaking up common antidepressant drugs (like Prozac and Paxil) that end up in wastewater. This matters because these plastic-drug combos could travel through our water systems and potentially end up back in our environment or food chain, though this study looked at water samples in a lab, not direct effects on human health. The findings help scientists understand how microplastics might be sneaking pharmaceuticals into places they shouldn't be, which is an early step in figuring out what that means for our health down the line.
Plastic waste has emerged as a key vector for transporting organic contaminants, amid growing environmental concerns. In this study, the adsorption behaviour of selective serotonin reuptake inhibitors onto polystyrene microplastics in aqueous systems was systematically investigated. Adsorption kinetics (first-pseudo-, second-pseudo-, Weber-Morris), isotherms (Langmuir, Freundlich, Dubinin-Radushkevich), and thermodynamic analyses were conducted to elucidate the mechanisms governing SSRI–PS interactions, complemented by datasets from scanning electron microscopy and Fourier transform infrared spectroscopy. Molecular dynamics (MD) simulations were further employed to describe the adsorption process at the molecular scale. The adsorption of SSRIs onto PS reached equilibrium within 30 min. Experimentally, the adsorption capacities followed the order paroxetine > fluoxetine > escitalopram, consistent with their hydrophobicity and aromatic structural features that promote π–π and hydrophobic interactions with PS. SSRI adsorption was influenced by pH 7–9, with maximum uptake typically occurring at basic conditions. Kinetic data were best described by the pseudo-second-order model (Qₑ = 28.73–60.15 mg g⁻1), which depends on both adsorbent and adsorbate availability, while the Langmuir isotherm (Qmax 13.89–18.39 mg g−1; RL < 1) provided the best fit to equilibrium data (R2 > 0.950), suggesting monolayer adsorption on a homogeneous PS surface. MD simulations confirmed that adsorption was dominated by non-bonded interactions (g(r) > 3.5 Å). This study offers valuable insights into the interactions between microplastics and pharmaceutical pollutants in water, enhancing our understanding of the environmental behaviour of these co-occurring contaminants.