Adsorption of ciprofloxacin from aqueous solution by plastic-based adsorbents: a review

Plastics and antibiotics are two classes of emerging contaminants with proposed negative impacts on aqueous ecosystems. In this paper, the adsorption of Ciprofloxacin (CIP) from water in studies using plastic-based adsorbents over the last half-decade was reviewed. The objectives of this review were to 1) review the procedures in the development of plastic-based material for CIP removal; 2) review the experimental designs adopted for CIP removal by plastic-based material; 3) summarise the factors affecting the CIP adsorption behaviour of plastic-based material; 4) explore the primary mechanism by which plastic-based material adsorb CIP; 5) evaluate the reusability of the plastic-based materials and 6) identify deficiencies in existing research on the adsorption of CIP by plastic-based materials and give suggestions for further study. We observed that mainly four categories of materials have been used including native plastic-based adsorbents, chemically modified plastic-based adsorbents, high-energy physical treated plastic-based adsorbents, and plastic-based composite adsorbents. The highest removal rate was recorded for the composite (99.1%). Experimental designs are mainly batch while columns have been scantly used. Changes in the pH, contact time, initial concentration, temperature, and ionic strength also affect the adsorption capacity. The most common mechanism by which CIP was adsorbed is hydrogen bonding. Additionally, electrostatic interaction and other non-covalent forces, such as polar-polar interaction, halogen bonds, and pi-pi interactions, are also mechanisms. The majority of current research on plastic-based material adsorption behaviour is done in labs, with little in-depth investigations of the adsorption process and affecting variables. As a result, further research on the adsorption behaviour of plastic-based materials in the environment is needed, which will help to fill that gap.