Co–Fe–oxide nanoparticles supported on the various highly dispersed matrices: the effect of the carrier on structural and magnetic properties

A series of mixed oxides was synthesized by deposition of the guest phase on the highly dispersed oxide matrix. Fumed nanooxides SiO2, Al2O3, SiO2/Al2O3, and SiO2/Al2O3/TiO2 with the specific surface area of 65–91 m2/g were selected as highly dispersed matrices. Co–Fe mixed oxides with the general formula Co4xFexOy (Co: Fe = 4: 1) were deposited as the guest oxides using the two-step method: (i) solvate-stimulated modification of the surface of fumed nanocarriers with the mixture of cobalt nitrate (II) and iron (III) formate and (ii) subsequent heat treatment up to 600 °C to form Co4xFexOy. The aim of this paper was to study the influence of the composition and structure of fumed oxide matrices and deposited guest phase on the morphology of the resulting composites in the gaseous and aqueous media using the XRD, XPS, FTIR, nitrogen adsorption and SEM/EDX, as well as quasi-elastic light scattering (QELS) methods. The low-temperature nitrogen adsorption isotherms have a sigmoidal shape with a narrow hysteresis loop characteristic of mesoporous materials. The specific surface area (SBET) of the composites varies from 48 to 82 m2/g, showing a tendency towards a decrease in the SBET values by 10–26% in comparison with the initial nanocarriers. The SEM data show the denser aggregate structure of nanocomposites compared to the initial carriers. The primary particle size was in the 30–60 nm range and the EDX data confirm the formation of a guest phase on the mixed aluminosilicate carriers, mainly in the surface patches corresponding to the alumina structure. According to the QELS data, there is a tendency to form aggregates of 100–10 μm in size in the aqueous media. The XRD method shows that the deposited metal oxides are in the form of crystalline phases of Co3O4 with the crystallites of 25–26 nm in size for the individual SiO2 and Al2O3 nanocarriers and 34–37 for the mixed ones, but the iron oxide reflections were not identified for the composites. XPS observation demonstrates the signal of Fe 2p electrons as the form of Fe2O3 oxide in the surface layer of nanocomposites as well as Co 2p as the Co3O4 and Co(OH)2

Preparation of yttrium citrate by the reaction of yttrium hydroxide with sodium citrate

A method of obtaining yttrium citrate by transformation of freshly precipitated yttrium hydroxide in the solutions of sodium citrate under hydrothermal conditions has been proposed. To determine the synthesis time, transformation kinetics consisted in by taking the solid samples for the C and H contents analysis after 6, 12, 24, 48 and 72 hours of synthesis. Simultaneously these samples were subjected to the thermogravimetric analysis. As follows from the thermogravimetric analysis adsorption of citrate dihydrate on yttrium hydroxide is observed in the initial period up to 24 hours. Later the yttrium citrate dihydrate is formed. The thermogravimetric analysis of the final product i.e. amorphous yttrium citrate showed that the decomposition/oxidation of the sample occurs in six stages the particle size analysis method of static light scattering showed that 45% of the particles had a diameter of 0.1-0.9 µm and 55% of particles with sizes from 0.9 to 5 µm

The influence of the hydroxyapatite synthesis method on the electrochemical, surface and adsorption properties of hydroxyapatite

Hydroxyapatite is a compound that belongs to the group of apatite minerals. It is a very interesting adsorbent and the main inorganic component of bones and teeth. Hydroxyapatite was obtained using three different methods. The samples were designated as HAP1, HAP2 and HAP3. The synthesized adsorbents were characterized by the following methods: thermal analysis, EDAX, XRD, FTIR, adsorption and desorption of nitrogen. The electrochemical properties were studied by electrochemical titration and zeta potential. The protein used was bovine serum albumin; its concentration was 5 mg/ml. The adsorbed protein concentration was determined based on the absorbance measurements at λ = 279 nm by UV-VIS. The characteristics are pHpzc = 6.64, 6.22, 6.43 at the HAP1/NaCl, HAP2/NaCl, HAP3/NaCl interfaces respectively and the pHiep values are about 4 for all the systems. The thermal stability of hydroxyapatite changed due to the bovine serum albumin adsorption. Synthesis method of hydroxyapatite influences on electrochemical properties and adsorption of bovine serum albumin on it

Influence of the Synthesis Method on the Structural Characteristics of Novel Hybrid Adsorbents Based on Bentonite

New hybrid composite materials were prepared by polymerization of resorcinol⁻formaldehyde resins in the presence of bentonite with various contents of polymer and water, and then exposed to pyrolysis in an inert atmosphere at 800 °C. The influence of the filler and synthesis method on the morphological, textural and structural characteristics has been described. The materials were characterized using low temperature nitrogen adsorption⁻desorption, small angle X-ray scattering, scanning electron microscopy, Raman spectroscopy, differential scanning calorimetry (DSC), and thermogravimetry analysis (TGA). The maximal values of the specific surface area of organo-bentonite and carbonized samples were 254 and 200 m2/g, respectively, which is much larger than that of the initial bentonite. The TGA and DSC experiments showed changes in the thermal stability of samples depending on their composition. The obtained data could provide a better understanding of the principles of preparing hybrid bentonite-containing composites that may provide an additional incentive to develop advanced technologies

Production of Activated Carbons from Food/Storage Waste

This paper deals with the adsorption of organic and inorganic pollutants on the surface of carbonaceous adsorbents prepared via the chemical activation of expired or broken food products—the solid residue of the “cola-type” drink as well as spoilt grains of white rice and buckwheat groats. The activation process was conducted in the microwave furnace with the use of two activating agents of different chemical nature—potassium carbonate and orthophosphoric acid. The activated carbons were characterized based on the results of elemental analysis, low-temperature nitrogen adsorption/desorption, Boehm titration, thermal analysis, and scanning electron microscopy. Additionally, the suitability of the materials prepared as the adsorbents of methylene blue and iodine from the aqueous solutions was estimated. The materials obtained via chemical activation with H3PO4 turned out to be much more effective in terms of both model pollutant adsorptions. The maximum sorption capacity toward iodine (1180 mg/g) was found for the white-rice-based activated carbon, whereas the most effective in the methylene blue removal (221.3 mg/g) was the sample obtained from the solid residue of the expired “cola-type” drink. For all carbonaceous materials, a better fit for the experimental adsorption data was obtained with the Langmuir isotherm model than the Freundlich one

Production of Activated Carbons from Food/Storage Waste

This paper deals with the adsorption of organic and inorganic pollutants on the surface of carbonaceous adsorbents prepared via the chemical activation of expired or broken food products—the solid residue of the “cola-type” drink as well as spoilt grains of white rice and buckwheat groats. The activation process was conducted in the microwave furnace with the use of two activating agents of different chemical nature—potassium carbonate and orthophosphoric acid. The activated carbons were characterized based on the results of elemental analysis, low-temperature nitrogen adsorption/desorption, Boehm titration, thermal analysis, and scanning electron microscopy. Additionally, the suitability of the materials prepared as the adsorbents of methylene blue and iodine from the aqueous solutions was estimated. The materials obtained via chemical activation with H3PO4 turned out to be much more effective in terms of both model pollutant adsorptions. The maximum sorption capacity toward iodine (1180 mg/g) was found for the white-rice-based activated carbon, whereas the most effective in the methylene blue removal (221.3 mg/g) was the sample obtained from the solid residue of the expired “cola-type” drink. For all carbonaceous materials, a better fit for the experimental adsorption data was obtained with the Langmuir isotherm model than the Freundlich one