Synthesis and characterization of composites based on expanded vermiculite and ferrite spinels

Abstract

Expanded vermiculite (EV) is clay, a typical 2:1 phyllosilicate which may be easily produced from the mineral vermiculite. After expansion EV withholds vermiculites physical structure but becomes far more porous than vermiculite which is accredited to the huge increase in the intercalation layer thickness. This feature in conjunction with the fact that the intercalation layer enriched by intercalation cations and water was the initial motive for this research, which opened a novel method for spinels synthesis. Intercalation layer of the EV is utilized as a reaction medium for the synthesis of Fe3O4, MnFe2O4, CoFe2O4, and FeCrFeO4. While magnetite is synthesized using the co-precipitation method, others are synthesized using hydrothermal co-precipitation method. Composites are then characterized by XRD (X-ray diffraction), FTIR (Fourier transformed infrared spectroscopy), SEM/EDS (scanning electron microscopy with energy dispersing microscopy) that confirmed the presence of the ferrite spinels inside the intercalation layer. After performed synthesis of the spinels, further parameters were determined: the isoelectric point (IEP), the capacity of cation exchange (CEC) and specific surface area (SSA) is calculated using Brunauer–Emmett–Teller (BET) adsorption isotherm of each composite together with matrix material (EV). The composites could be used as potential adsorbents of heavy metals and/or organic pollutants, and this synthesis method could be used for producing numerous compounds that are mainly being produced by solvothermal method or co-precipitation method.