A new magnetic composite with potential application in boron adsorption: Development, characterization, and removal tests

• Published in: Materials chemistry and physics 2022-02, Vol.277, p.125368, Article 125368
• Main Authors: Pinotti, Camila N., de Souza, Luana M., Marques, Willbrynner P., Proveti, José R.C., Jesus, Honério C., Freitas, Jair C.C., Porto, Paulo S.S., Muniz, Eduardo P., Passamani, Edson C.
• Format: Article
• Language: English
• Subjects: Adsorption; Aqueous solutions; Boron; Boron adsorption; Boron compounds; Cobalt ferrites; Crystallites; Ferrite nanoparticles; Infrared spectroscopy; Iron 57; Magnesium oxide; Magnetic composite; Mossbauer spectroscopy; Orange bagasse; Permanent magnets; Scanning electron microscopy; Sol-gel processes; Spectrum analysis; Surface chemistry; X-ray diffraction
• ISSN: 0254-0584; 1879-3312
• DOI: 10.1016/j.matchemphys.2021.125368

In this work, a new magnetic composite, with good performance in the adsorption of boron from aqueous solutions, is proposed. The composite was prepared from CoFe2O4 and MgO precursors, which were produced by the sol-gel method using orange juice residues. X-ray diffraction, scanning electron microscopy, infrared spectroscopy, 57Fe Mössbauer spectroscopy, and magnetization measurements have indicated that the ferrimagnetic CoFe2O4 nanocrystalline phase is immersed in the MgO matrix. The magnetic composite was applied to boron compounds removal from synthetic effluents (with boron concentrations up to 20 mg L−1), showing up to 92% removal capacity. After the boron adsorption process on the MgO surface, X-ray diffraction, scanning electron microscopy, and infrared spectroscopy results have shown the formation of crystalline Mg(OH)2 (with needle-like structures), and 57Fe Mössbauer spectroscopy has indicated that the fraction of Fe+3 ions in the nanograin surfaces was changed in comparison with the pristine adsorbents. Three possible boron adsorption mechanisms are suggested: adsorption at the Mg(OH)2 crystallite surface, adsorption through the formation of Fe–O–B bonds, and adsorption by an amorphous Mg(OH)2 gel. The pseudo-first order model was successfully used to fit the kinetic adsorption curves, whereas the Freundlich model has described the isotherms, thus indicating a heterogeneous distribution of adsorption heat and affinities. The composite was found to adsorb about 6% more boron than pure MgO and can be recoverable with a permanent magnet. •Novel magnetic composite produced by Sol Gel method using orange bagasse residues.•MgO and Cobalt ferrite react when mechanically mixed in a mortar.•Boron adsorption related to surface hydroxyl.•More than 90% boron adsorption in synthetic effluent with 6 mg L−1 of boron.