Microplastics as carriers of inorganic and organic contaminants in the environment: A review of recent progress

Microplastics in the environment are becoming ubiquitous and their presence is considered a global threat. There are emerging concerns that microplastics may affect ecosystems via contamination of water, soil and air, and subsequently impact human health either by inhalation of airborne particulates or consumption of contaminated water and food. Moreover, their ingestion by organisms may cause their damage as well as their leachability of their constituent. Furthermore, microplastics are considered potential carriers of various contaminants, due to their considerable adsorption capacity, acting as a means of long-range transportation for contaminants into the environment. Therefore, this work presents a review of recent progress about microplastics as carriers of organic and inorganic emerging contaminants, while studying adsorption kinetics, mechanisms and the applications of different adsorption isotherms. Examples of different contaminants are presented, including additives, heavy metals, persistent organic contaminants, antibiotics, pesticides, and fungicides. Microplastics as carriers may differently affect the transport and the deposition of chemical contaminants such as additives, heavy metals, persistent organic contaminants, antibiotics, pesticides, fungicides, depending on their type, concentration and aging. The most common sorption mechanism of organic contaminants on microplastics is hydrophobic interaction, followed by electrostatic interactions, H-bonding, halogen-bonding and π-π interactions. On the other hand, metal ions are adsorbed mainly by electrostatic interactions and surface complexation. For both organic and inorganic contaminants, adsorption kinetic data are better fitted by the PSO model, whereas depending on the system the isothermal data are adequately described by whether the Freundlich or Langmuir isotherm model.