Green chemistry preparation of superparamagnetic nanoparticles containing Fe3O4 cores in biochar

• Preparation of superparamagnetic iron oxide nanoparticles in biochar by green synthesis.
• Novel formation of SPMIOBNPs from condensed tannin extract of Acacia mearnsii.
• Superparamagnetism in magnetite nanoparticles with sizes 25–35 nm.
• The SPMIOBNPs consisted of organic and inorganic components.

Nanotechnology is an engineering science in which the aim is to develop novel procedures and structures at the nanoscale that might offer solutions to many current problems. In this article, we describe the synthesis of superparamagnetic iron oxide (Fe3O4) nanoparticles in biochar obtained from the condensed tannin extract of Acacia mearnsii, using a single-step process that is compliant with the principles of green chemistry. Characterization of this material (acronym: SPMIOBNs) was performed using Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, and X-ray diffraction analysis. The porous particles produced contained iron oxide nanoparticles with average sizes in the range 20–35 nm. The magnetic properties revealed that the SPMIOBNPs were superparamagnetic, with a saturation magnetization of 3.2 memu/g at 300 K.