Zofia Lendzion-Bieluń

Equilibrium and kinetic studies on acid dye Acid Red 88 adsorption by magnetic ZnFe2O4 spinel ferrite nanoparticles.

A magnetic ZnFe2O4 (MNZnFe) was synthesized by microwave assisted hydrothermal method and was used as an adsorbent for the removal of acid dye Acid Red 88 (AR88) from aqueous solution. The effects of various parameters such as initial AR88 concentration (10-56 mg L(-1)), pH solution (3.2-10.7), and temperature (20-60°C) were investigated. Prepared magnetic ZnFe2O4 was characterized by XRD, SEM, HRTEM, ICP-AES, BET, FTIR, and measurements of the magnetic susceptibility. The experimental data were analyzed by the Langmuir and Freundlich models of adsorption. Equilibrium data fitted well with the Langmuir model. Pseudo-first-order and pseudo-second-order kinetic models and intraparticle diffusion model were used to examine the adsorption kinetic data. The adsorption kinetics was found to follow the pseudo-second-order kinetic model. Thermodynamics parameters, ΔG°, ΔH° and ΔS°, indicate that the adsorption of AR88 onto MNZnFe was spontaneous and exothermic in nature.

The effect of aluminium oxide on the reduction of cobalt oxide and thermostabillity of cobalt and cobalt oxide

AbstractDuring precipitation and calcination at 200°C nanocrystalline Co3O4 was obtained with average size crystallites of 13 nm and a well developed specific surface area of 44 m2 g−1. A small addition of a structural promoter, e.g. Al2O3, increases the specific surface area of the cobalt oxide (54 m2 g−1) and decreases the average size of crystallites (7 nm). Al2O3 inhibits the reduction process of Co3O4 by hydrogen. Reduction of cobalt oxide with aluminium oxide addition runs by equilibrium state at all the respective temperatures. The apparent activation energy of the recrystallization process of the nanocrystalline cobalt promoted by the aluminium oxide is 85 kJ mol−1. Aluminium oxide improves the thermostability of both cobalt oxide and the cobalt obtained as a result of oxide phase reduction.

Crosslinked carboxymethyl starch: one step synthesis and sorption characteristics.

Crosslinked carboxymethyl starch (cCMS) hydrogels were synthesized in a simple one step process using various crosslinking agent content - dichloroacetic acid (DCA) with the constant monochloroacetic acid and DCA/anhydroglucosidic unit (AGU) 1.75:1 molar ratio whereas DCA/AGU was changed in a range 0.15-1.0mol/AGU. The degree of substitution (DS=0.4-0.9), and reaction efficiency were evaluated. Moreover, swellability in water and aqueous solutions was determined. Adsorption tests for Fe(II) cation as a function of cCMS crosslinking degree, sorbent dose and time were performed in autogenic pH (ca. 7.0). For comparison four other divalent metal cations were tested. Adsorption efficiency was up to 98% for Fe(II), 96% for Ca(II) and above 99.7% for Cu(II), Cd(II) and Pb(II).

Effect of Cobalt Addition on the Activity of Nanocrystalline Iron Catalysts in the Cracking of Methane Reaction

The effect of cobalt addition on the activity of nanocrystalline iron catalysts in the cracking of methane reaction is studied. The composition and properties of the catalyst were determined by inductively coupled plasma optical emission spectrometry, X-ray diffraction and temperature-programmed reduction methods. The activity of the catalyst in the reaction was defined by measuring the concentration of hydrogen, which was determined by gas chromatography. After cracking of methane reaction, the sample coated with a carbon deposit was examined with scanning electron microscope with energy-dispersive spectrometer. The reaction yield in the direction of hydrogen acquisition for the catalyst with cobalt was above 80%, and after the regeneration process, the catalyst was still active at a very high level. The reaction path for the catalyst without the cobalt addition was performed in two steps, and the catalyst after the reaction was non-regenerative.

The activity of fused-iron catalyst doped with lithium oxide for ammonia synthesis

Abstract The iron catalyst precursor promoted with Al2O3, CaO, and Li2O was obtained applying the fusing method. Lithium oxide forms two phases in this iron catalyst: a chemical compound with iron oxide (Li2Fe3O4) and a solid solution with magnetite. The catalyst promoted with lithium oxide was not fully reduced at 773 K, while the catalyst containing potassium was easily reducible at the same conditions. After reduction at 873 K the activity of the catalyst promoted with lithium oxide was 41% higher per surface than the activity of the catalyst promoted with potassium oxide. The concentration of free active sites on the surface of the catalyst containing lithium oxide after full reduction was greater than the concentration of free active sites on the surface of the catalyst promoted with potassium oxide.

The effect of manganese on the structural and surface properties of nanocrystalline cobalt catalyst for ammonia synthesis

AbstractBased on the active surface model of the iron catalyst for ammonia synthesis, the assumptions which led to obtaining the cobalt catalyst for ammonia synthesis were described. The incorporation into the system small amounts of manganese, an element which binds oxygen stronger than cobalt, has influence the development of the catalyst’s specific surface area. The activity of manganese modified catalysts is higher than that of cobalt catalyst without manganese addition. The obtained catalysts were characterized with the following methods: ICP-OES, XRD, BET

Surface characteristics of KOH-treated commercial carbons applied for CO2 adsorption:

The effect of an alkali treatment (potassium hydroxide) on the properties of a commercial activated carbon has been studied. The aim of the treatment was to improve the adsorption properties of the material toward carbon dioxide. In the result of the treatment, silica contained in the raw carbon was removed and the density of the material increased. The changes in the surface chemistry were observed as well. The treatment of the activated carbon with KOH resulted in a complete removal of carboxy and lactone groups and a decrease of the general content of the acidic groups (more significant than that of basic groups). Simultaneously, the surface concentration of hydroxyl groups increased. The alkali treatment of activated carbon resulted in an increase of carbon dioxide uptake of 14% (measured using a volumetric method at 0℃). The adsorption of carbon dioxide on activated carbon has a mixed (physicochemical) character and that two types of adsorption sites are present at the surface. The adsorption energy varies roughly from 25 to 60 kJ/mol.

Characterization of FeCo based catalyst for ammonia decomposition. The effect of potassium oxide

Abstract FeCo fused catalyst was obtained by fusing iron and cobalt oxides with an addition of calcium, aluminium, and potassium oxides (CaO, Al2O3, K2O). An additional amount of potassium oxide was inserted by wet impregnation. Chemical composition of the prepared catalysts was determined with an aid of the XRF method. On the basis of XRD analysis it was found that cobalt was built into the structure of magnetite and solid solution of CoFe2O4 was formed. An increase in potassium content develops surface area of the reduced form of the catalyst, number of adsorption sites for hydrogen, and the ammonia decomposition rate. The nitriding process of the catalyst slows down the ammonia decomposition.