Search

Cobalt ferrite nanoparticles were obtained by the green synthesis method using extracts of grape peel and grape pulp. The obtained samples have been investigated by means of X-ray diffraction (XRD) analysis, scanning electron microscope (SEM), and Mossbauer spectroscopy. All samples contain pure CoFe2O4 with the cubic spinel structure of the space group Fd3m. XRD analysis indicates that cobalt ferrite nanoparticles synthesized using grape peel extract and grape pulp extract have crystallite sizes of ~ 5 and ~ 25 nm, respectively. Cation distribution and crystalline structure parameters of the samples were calculated on the basis of Mossbauer spectroscopy data. After annealing, the CoFe2O4 sample obtained with grape pulp extract has a higher degree of inversion than that obtained with grape peel extract. The decrease in the degree of inversion is related to a decrease in the average size of crystallites. The CoFe2O4 sample synthesized using grape peel extract is a more active catalyst for the decomposition of hydrogen peroxide. The first-order rate constants are 1.11·10−4 s−1 and 3.43·10−4 s−1 for the CoFe2O4-pulp and CoFe2O4-peel samples, respectively. A 100 mM H2O2 solution was decomposed to 97.4%. The surface morphology of the cobalt ferrites remains unchanged after the catalytic decomposition of H2O2. The synthesized cobalt ferrites can be used in Fenton processes as stable magnetic catalysts.

In this paper, the effect of SnO2 impurity on the surface charge and adsorption properties of TiO2 samples is investigated. The experimental value of the zero charge point for TiO2 with 3%, 6% and 12% of SnO2 equals 3.53, 3.97 and 3.2, respectively. The adsorption activity of the samples was studied on model solutions of the anionic dye – Congo red. The maximum adsorption capacity (qexp) equals 24.6 mg/g for 3Sn/TiO2, 25.0 mg/g for 6Sn/TiO2 and 39.1 mg/g for 12Sn/TiO2. Langmuir, Freundlich, and Dubinin-Radushkevich models were used to describe the adsorption mechanism of Congo red dye on the surface of Sn/TiO2 samples. Based on the results of the studies of Congo red adsorption by the surface of titanium dioxide doped with Sn, all samples agree best with the Langmuir model. The correlation coefficients for the Langmuir isotherms are in the range of 0.9927 - 0.9996, while the values ​​of R2 for the Freundlich and Dubinin-Radushkevich isotherms are in the range of 0.721 - 0.8329 and 0.8283 - 0.9433, respectively. Experimental data obtained from adsorption isotherms show that the TiO2 sample containing 12% SnO2 is the most active. The best result of Congo red removal occurred at a concentration of Co = 5 mg/l (% of removed dye ≈ 83% for 12Sn/TiO2; 81% for 6Sn/TiO2 and 71% for 3Sn/TiO2). Therefore, the studied samples of TiO2 doped with SnO2 can be used as effective adsorbents of Congo red from aqueous solutions.

In this paper, the synthesis of spinel magnesium ferrite (MgFe2O4) nanoparticles is reported, along with its structural, magnetic and hyperthermic properties, which ensure them being effectively used in various fields. Firstly, magnesium ferrite was synthesized via sol-gel auto-combustion method, using honey as the reducing agent. The crystallite size was calculated via the Scherrer method, the modified Scherrer method, the Williamson-Hall method, and the size-strain plot (SSP) method. X-ray analysis was used to confirm the structure of the spinel. For morphological study of ferrite nanoparticles, scanning electron microscopy (SEM) was used. Finally, hyperthermic properties of magnesium ferrite were analyzed for potential usage in medicine. According to these results, spinel magnesium ferrite (MgFe2O4) nanoparticles proved to be suitable for destruction of cancer cells, as they can be heated to the desired temperature, which will increase the sensitivity of those cells.

The magnesium-zinc ferrites Mg1-xZnxFe2O4 (x = 0…1) were studied as magnetic sorbents for environmental applications. Low-temperature Mossbauer spectroscopy was used to determine the distribution of magnesium and ferric ions in the spinel crystal lattice. The influence of Zn content on magnetic parameters was investigated on the basis of VSM data. As the molar ratio of zinc to magnesium increases from 0 to 1, the pHPZC value decreases from 10.5 to 8.9. Langmuir and Freundlich models were used to check whether single-layer or multi-layer adsorption occurs. The adsorption of Cr(VI) and Ni(II) ions is well fitted by the Langmuir equation. To check the physical or chemical nature of the sorption process, the Dubinin-Radushkevich equation was used. It was found that the processes of adsorption of Cr(VI) and Ni(II) ions are of a chemical nature. The best Cr(VI) ion adsorption capacity was found for the Mg0·2Zn0·8Fe2O4 sample (qe = 30.49 mg/g). The percentage of heavy metal removal by the mixed ferrite samples increases with increasing zinc content. The most effective sorbent for Ni(II) removal is the Mg0·4Zn0·6Fe2O4 sample (93.2%). Modeling the antistructure provides deeper insight into the mechanism of heavy metal adsorption. The obtained magnesium-zinc ferrites are promising magnetic adsorbents for removing chromate and nickel ions from the environment.