Magnetic nanocomposite based on montmorillonite, Fe oxides, and hydrothermal carbon: Synthesis, characterization and pollutants adsorption tests

EMILIA ZELAYA SOULÉ,; BARRAQUÉ F,; MORANTES FERNANDEZ CÉSAR; FLORES F. M.; FERNANDEZ M A; MARÍA ROSA SANCHEZ TORRES; M. L. MONTES

Materialia

Elsevier

Año: 2021

2589-1529

This work presents the synthesis and characterization of montmorillonite-Fe oxides (Mt-Mag) and Mt-Fe oxidescarbon (Mt-Mag-C) systems as adsorbent materials, prepared by efficient and low-cost procedures. Fe oxides weresynthesized by alkaline oxidation in the presence of nitrates while carbonization was hydrothermally synthesized.The adsorption capacity of the synthesized materials was tested against different pollutants (norfloxacin, thiabendazole, thiophanate-methyl, oxytetracycline, P4R and Cr(VI)). Fe particles and carbon were not homogeneouslydistributed while Mt-Mag-C sample presented a lower specific surface area and porosity than Mt-Mag, relatedto carbon presence, while magnetic nanoparticles seem not to block Mt external pores. Both materials revealednegative surface charge, indicating that is dominated by montmorillonite. Besides, Mt structure seems to be modified by both Fe oxides and carbon synthesis. The magnetic response was higher in Mt-Mag-C than in Mt-Mag,indicating Fe phases modifications during carbonization. The principal identified Fe oxide was magnetite, withminor contributions of paramagnetic Fe3+, goethite, and paramagnetic relaxation, with a significantly increasedof the spectral area of the latter in Mt-Mag-C. Fe concentration determined by Mössbauer spectroscopy resultedhigher on Mt-Mag-C than Mt-Mag, indicating that Fe atoms located at the interlayer space of montmorillonite,that give not Mössbauer signal, are exposed by sonication and carbon synthesis, and new magnetite particlesare formed through the reduction of Fe3+ atoms in dextrose aqueous solution. The paramagnetic relaxation increase is related to new magnetite particles, that, because of carbon presence, cannot be magnetically coupled.A significant sorption capacity was found for cationic and zwitterionic compounds, revealing the relevance ofelectrostatic interaction. The magnetic response of Mt-Mag-C and the results of sorption tests for cationic andzwitterionic compounds, claims Mt-Mag-C as a promising sorbent material.