Changes on structural and magnetic properties of maghemite nanoparticles during their coverage with MCM-41

FELLENZ, NICOLÁS; PEREZ DE BERTI, IGNACIO; SOLDATI, ANALIA L.; STEWART, SILVANA; MARCHETTI, SERGIO; BENGOA, JORGE FERNANDO

CERAMICS INTERNATIONAL

ELSEVIER SCI LTD

Lugar: Amsterdam; Año: 2015 vol. 41 p. 15057 - 15066

0272-8842

This work reports a simple synthesis of a mesoporous ordered silica structure(MCM-41) grown up around pre-synthesized maghemite nanoparticles. A compositewith magnetic response and high specific surface area was obtained adding maghemitenanoparticles coated with oleic acid in the synthesis gel of MCM-41 and finallycalcining in air. Different characterizations techniques such as magnetic measurements,Mössbauer spectroscopy at 25 and -260 ºC and transmission electron microscopy wereused to study the magnetic and structural changes of the initial maghemite nanoparticlesproduced during its coverage with the mesoporous silica structure. The presence of themesoporous structure inhibits the expected transformation from maghemite to hematitewhen the system was calcined in air at 510 ºC. It was established that a sintering of thenanoparticles during the calcination step occurs, leading to a magnetization saturationvalue similar to that of the bulk compound. In order to evaluate the capability asadsorbent, the magnetic composite was subjected to a surface amino-functionalizationand then tested for Cr(VI) and Cu(II) adsorption from water.