Hybrid nanoadsorbents for the magnetically assisted removal of metoprolol from water

• Synthesis of Fe3O4 nanoparticles coated with κ-carrageenan hybrid siliceous shells.
• Magnetic hybrids for the uptake of metoprolol tartrate from water.
• The adsorption capacity enhanced 300% compared with the best sorbent in literature.
• Easy separation of sorbents from water under a magnetic gradient.

Metoprolol (MTP) is known as one of the most frequently detected beta blockers in surface waters, with potentially harmful impact on environment and human health due to its widespread use and resistance to hydrolysis. The removal of MTP in wastewater treatment plants is still very low due to fairly ineffective conventional water treatment procedures and, therefore, more efficient treatments are needed. To tackle this challenge, novel biosorbents composed of magnetite nanoparticles functionalized by κ-carrageenan hybrid siliceous shells (Fe3O4@SiO2/SiCRG) were successfully prepared and tested in magnetically assisted removal of metoprolol tartrate from aqueous solutions. The MTP adsorption by the produced core–shell composite structures was thoroughly assessed and modeling of the equilibrium data was best fit with Langmuir and Toth models. The maximum observed MTP adsorption capacity of the magnetic hybrids amounted to 447 mg/g, thus representing an enhancement of 300% compared to most efficient MTP sorbents reported so far. The results of FTIR analysis indicate that the adsorption mechanism is mostly based on electrostatic interactions between sulfonate groups of κ-carrageenan and protonated amine groups of metoprolol. The obtained Fe3O4@SiO2/SiCRG composite particles show a great potential for removing MTP from water, stemming from their high inherent absorption capacity and convenient magnetic separation.