Multi-mechanistic adsorption of pharmaceuticals and personal care products on oxidized microplastics: Oxidation processes, mechanisms, and environmental implications

• Oxidation processes enhance the surface area and adsorption capacity of MPs • Hydrophilic PPCPs adsorb better to oxidized or aged microplastics • Sorption driven by hydrophobic, hydrogen bonding, and electrostatic forces mechanism • Environmental factors such as pH, salinity, and aging alter PPCP adsorption behavior • Surface chemistry changes influence combined contaminant fate and risk pathways Microplastics (MPs) have emerged as significant environmental pollutants, raising concerns due to their persistence, widespread distribution, and potential impacts on ecological and human health. Oxidation processes increase the sorptive capacity of MPs by adding oxygen-containing functional groups and creating rougher, more reactive surfaces. This review focuses on how these oxidation-induced changes modify the adsorption of pharmaceuticals and personal care products (PPCPs). Oxidized MPs exhibit altered surface polarity and charge, strengthening key interactions such as hydrophobic partitioning, hydrogen bonding, and electrostatic attraction. Environmental conditions, including pH, salinity, and the degree of aging, further influence these mechanisms. Hydrophilic PPCPs generally show stronger affinity for oxidized MPs because their functional groups interact more effectively with the modified surfaces. Variations in pH and salinity can reduce sorption by shifting surface charge and disrupting electrostatic forces. This review demonstrates that oxidation-driven surface transformations are central to understanding how MPs adsorb, transport, and potentially release PPCPs in aquatic environments, shaping their environmental behavior and associated risks.