Synthesis of mesoporous carbon capsules encapsulated with magnetite nanoparticles and their application in wastewater treatment

Abstract

Mesoporous carbon capsules encapsulated with Fe₃O₄ nanoparticles were prepared by the successive coating of a silica layer and a subsequent mesoporous silica/carbon layer on the surface of Fe₃O₄ nanoparticles followed by chemical etching with NaOH solution. TEM observations show that the as-obtained samples had a rattle-like structure: Fe₃O₄ nanoparticles were encapsulated in the interior of the mesoporous carbon capsules. The typical nitrogen adsorption/desorption results demonstrate that the specific surface area for the as-prepared samples is up to 1570 m² g⁻¹, and the total pore volume is about 3.02 cm³ g⁻¹. The porous wall structure of the lateral carbon capsules provides the sufficient spaces that contribute to high adsorption capacities and faster adsorption rates of pollutants molecules in aqueous media. The nanocomposites are superparamagnetic at room temperature with a saturation magnetization of 5.5 emu g⁻¹, which provides the prerequisite for the fast magnetic separation in wastewater treatment application. Water treatment experiments indicated that the as-prepared samples exhibited higher adsorption rates and more effective removal capacity of organic pollutants compared with commercial activated carbon (AC), and their maximum adsorption capabilities for methylene blue (MB), congo red (CR), and phenol reached 608.04, 1656.9 and 108.38 mg g⁻¹, respectively. The multifunctional nanocomposites can be potentially used as absorbents for fast, convenient, and highly efficient removal of pollutants from the wastewater, which will play important roles in the purification or desalination of natural water and industrial effluents.