Magnetic adsorbents for removal of pharmaceuticals: A review of adsorption properties

The global development of industry and agriculture around the world led to the contamination of various aquatic environments with pharmaceuticals. Even at low concentrations in water, these pollutants cause significant human health problems, adversely affect the quality of drinking water, and have a detrimental effect on the environment. The uncontrolled release of pharmaceuticals into aquatic ecosystems poses a real threat to all life on Earth and requires effective methods of removal. Adsorption is one of the best and most cost-effective ways to clean wastewater from micropollutants. Magnetic adsorbents attract considerable attention due to their outstanding magnetic properties, high surface reactivity, chemical stability, and the possibility of their modification and functionalization. The presence of various functional groups makes it possible to increase the adsorption efficiency. This article is a comprehensive review of studies on the use of various magnetic nanoparticles and composites for the removal of pharmaceuticals from aqueous environments through adsorption. The main attention is paid to two categories of pharmaceuticals: antibiotics (tetracycline, ciprofloxacin, levofloxacin, etc.) and nonsteroidal anti-inflammatory drugs (diclofenac, ibuprofen, etc.). The concentration of these pollutants in the European surface waters is provided. The main modes of interaction between the adsorbent (functionalized magnetic nanoparticles) and the adsorbate (pharmaceuticals) are discussed. The analyzed drugs are mainly adsorbed through electrostatic interactions, hydrogen bonds, π-π interaction, surface complexation, ion-exchange, etc. The effect of various parameters (pH, contact time, temperature, adsorbate concentration, adsorbent dose) on adsorption efficiency is summarized. The analysis shows that the adsorption behavior strongly depends on the solution pH, temperature, and the initial concentration of the pollutant. The functionalized magnetic nanoparticles have a good potential for pharmaceuticals removal from aqueous media. The perspectives and problems in magnetic adsorbents applications have been presented.