Influence of post-pyrolysis treatment on physicochemical properties and acid medium stability of magnetic carbon nanocomposites

Abstract

This study presents the preparation of magnetic carbon nanocomposites (MCNCs) through a two-step procedure: (i) in situ co-precipitation of magnetite (Fe3O4) nanoparticles into four different carbonaceous matrixes and (ii) post-pyrolysis treatment to coat the magnetic core. Four post-pyrolysis MCNCs were obtained: MACP (post-pyrolyzed magnetic activated carbon), MCCP (post-pyrolyzed magnetic charcoal), MHCPOR (post-pyrolyzed magnetic hydrochar from orange residue), and MBCPSFH (post-pyrolyzed magnetic biochar from sunflower husk). These four samples were compared with the starting MCNCs prepared without post-pyrolysis treatment: MAC, MCC, MHCOR, and MBCSFH, respectively. After post-pyrolysis treatment, a thin carbon layer surrounding some of the magnetite nanoparticles was identified by transmission electron microscopy. Post-pyrolysis modified the porous structure and chemical composition of MCNCs. Furthermore, a leaching test with acid sulfuric solution at 90 °C was carried out. The results suggested that the MHCPOR and MBCPSFH were more stable in an acidic medium than MACP and MCCP, indicating that the coat generated during post-pyrolysis of hydrochar and biochar could partially protect the magnetic core by reducing Fe leaching into the aqueous solution. Biochar and the hydrochar-based MCNCs before and after post-pyrolysis treatment exhibit superparamagnetic properties; however, their saturation magnetization (Ms) decreased considerably. These results open the potential application fields of MCNCs obtained by post-pyrolysis of biochar and hydrochar-based materials in acidic mediums.

The potential of lignocellulosic biomass for magnetic solid phase extraction of naproxen from saliva samples

“…4b exhibits the FTIR spectra of the magnetic biochars, which revealed a peak at 580 cm −1 that was identied as the Fe-O vibration. 45 SEM analysis. The microstructure and morphology of magnetic biochar samples obtained from three sources, namely AMBC, WMBC, and PMBC, are illustrated in Fig.…”

Exploitation of expired cellulose biopolymers as hydrochars for capturing emerging contaminants from water

“…1f) show that bare magnetite acquires a magnetism of about 35 emu/g which is similar to values reported in literature, 44 while the hydrochar-coated magnetite exhibits a magnetism of about 12.4 emu/g which is less than that of bare magnetite due to the coating process, however higher than values reported in previous literature for magnetic hydrochar from orange residue, magnetic activated sawdust hydrochar and magnetized sesame oil cake hydrochar. [45][46][47] 3.3. Adsorption performance of the hydrochar 3.3.1. pH-controlled adsorption.…”