Cr3+ and Al3+ co-substituted zinc ferrite: structural analysis, magnetic and electrical properties

International audienceNanocrystalline powders of chromium and aluminum co-substituted zinc ferrites with general formula ZnFe2−2xCrxAlxO4 (0 ⩽ x ⩽ 1) have been synthesized for the first time. Using the sol-gel auto-combustion technique and the tartaric acid as combustion-complexion agent, materials with spinel mono-phase cubic spinel structure were successfully prepared. The materials were characterized by IR, XRD, SEM and 57Fe Mössbauer spectroscopy. The crystallite size estimated by Scherrer formula has been found in the range of 16-69 nm. The experimental results combined with those obtained from a mathematical model suggested that all compounds have a mixed ionic distribution. Moreover, relationships between the structure features and the electric and magnetic properties have been established. The magnetic measurements showed that the hysteresis losses and the magnetization at 10 KOE linearly decreased when the Cr-Al content in Zn ferrite increased. The results obtained in dielectric study showed very low values of dielectric loss at frequencies over 1 MHz

Effect of Al3+substituted zinc ferrite on photocatalytic degradation ofOrange I azo dye

International audiencetAluminum substituted zinc ferrite catalysts were prepared by the sol-gel auto-combustion method andcharacterized by using Mössbauer spectroscopy and nitrogen adsorption-desorption isotherm measure-ments. The photocatalytic activity of ZnFe2−xAlxO4(0 ≤ x ≤ 2) spinel ferrites was evaluated for the firsttime on Orange I azo dye degradation under UV light illumination. The results showed that the photo-catalytic process was promoted when aluminum cations substituted iron cations located in octahedralsites of zinc ferrite lattice. Therefore, the Orange I azo dye best removal efficiency was observed when theAl3+and Fe3+are presents in equimolar amounts. The dye degradation performance of the ZnFe2−xAlxO4(0 ≤ x ≤ 2) catalysts was related to the crystallite size than to the BET surface area values and to thepresence of secondary phases, such as -Fe2O3and ZnO

Magnetic Solid-Phase Extraction of Cadmium Ions by Hybrid Self-Assembled Multicore Type Nanobeads

Novel hybrid inorganic CoFe2O4/carboxymethyl cellulose (CMC) polymeric framework nanobeads-type adsorbents with tailored magnetic properties were synthesized by a combination of coprecipitation and flash-cooling technology. Precise self-assembly engineering of their shape and composition combined with deep testing for cadmium removal from wastewater are investigated. The development of a single nanoscale object with controllable composition and spatial arrangement of CoFe2O4 (CF) nanoparticles in carboxymethyl cellulose (CMC) as polymeric matrix, is giving new boosts to treatments of wastewaters containing heavy metals. The magnetic nanobeads were characterized by means of scanning electron microscopy (SEM), powder X-ray diffraction analysis (XRD), thermogravimetric analysis (TG), and vibrational sample magnetometer (VSM). The magnetic properties of CF@CMC sample clearly exhibit ferromagnetic nature. Value of 40.6 emu/g of saturation magnetization would be exploited for magnetic separation from aqueous solution. In the adsorptions experiments the assessment of equilibrium and kinetic parameters were carried out by varying adsorbent dosage, contact time and cadmium ion concentration. The kinetic behavior of adsorption process was best described by pseudo-second-order model and the Langmuir isotherm was fitted best with maximum capacity uptake of 44.05 mg/g

Synergistic effect of fuel agents and mass ratio for morpho-structural optimization of magnetic claybased nanocomposites with high adsorption capacity

International audienceThe study is focused on creating magnetic mesoporous materials through the insertion of a nickel ferrite into the structure of kaolin-type clay. Sol-gel auto-combustion method was employed to synthesize the materials, using glycine and tartaric acid as chelating/combustion agents. This is the first study on the combined effect of different fuel agents and of clay-to-ferrite molar ratio on the structural, textural, magnetic and adsorptive properties of nanocomposites. The value of the average pore size, registered in a range of 6.01 and 12.9 nm, indicates the dependence on both molar ratio and fuel agent. The textural properties of the materials, corroborated with those obtained from XRD, SEM and TEM and VSM, suggest that magnetic nanocomposites can be successfully used as adsorbents in the removal of harmful organics. The obtained nanocomposites show excellent adsorption, with up to 98% BB41 dye removal, and a facile recuperation, due to their magnetic properties. The maximum adsorption capacity of dye, of 752.2 mg/g, was obtained for C3Ni_act350, in the presence of H2O2 in solution. More than that, the adsorption capacity of magnetic composites increased with increasing the NiFe2O4 content

Sequential Synthesis Methodology Yielding Well-Defined Porous 75%SrTiO3/25%NiFe2O4 Nanocomposite

In this research, we reported on the formation of highly porous foam SrTiO3/NiFe2O4 (100−xSTO/xNFO) heterostructure by joint solid-state and sol-gel auto-combustion techniques. The colloidal assembly process is discussed based on the weight ratio x (x = 0, 25, 50, 75, and 100 wt %) of NiFe2O4 in the 100−xSTO/xNFO system. We proposed a mechanism describing the highly porous framework formation involving the self-assembly of SrTiO3 due to the gelation process of the nickel ferrite. We used a series of spectrophotometric techniques, including powder X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), N2 adsorption isotherms method, UV-visible diffuse reflectance spectra (UV-Vis DRS), vibrating sample magnetometer (VSM), and dielectric measurements, to investigate the structural, morphological, optical, magnetic, and dielectric properties of the synthesized samples. As revealed by FE-SEM analysis and textural characteristics, SrTiO3-NiFe2O4 nanocomposite self-assembled into a porous foam with an internally well-defined porous structure. HRTEM characterization certifies the distinctive crystalline phases obtained and reveals that SrTiO3 and NiFe2O4 nanoparticles were closely connected. The specific magnetization, coercivity, and permittivity values are higher in the 75STO/25NFO heterostructure and do not decrease proportionally to the amount of non-magnetic SrTiO3 present in the composition of samples