Ad capitis III. Esai. comm. 16. et 17

Arkit: A-B4 C2.

Rejeito de mineração de carvão como adsorvente para remoção da acidez, Fe (III), Al (III) e Mn (II) em drenagem ácida

This study aimed the use of coal mining waste as a new adsorbent for H3O+ and removal of Al (III), Fe (III) and Mn (II) from acid mine drainage. Data from kinetic and equilibrium of the adsorption of H3O+ followed the pseudo second-order and Langmuir isotherm models. The maximum adsorption capacity of H3O+ was 316 mmol kg-1. The adsorbent removed 100% of Al (III), 100% of Fe (III) and 89% of Mn (II), suggesting its use as an alternative for the treatment of acid mine drainage.

Num a Johanne Pharisaei et Sadducaei fuerint baptizati, occasione eorum, qvae Matth. III: v. 7. seqq. leguntur

Invocatio: I.N.S.S.T.

Pré-concentração de Cr(III) e análise de especiação de cromo empregando montmorilonita saturada com íons potássio

The clay mineral montmorillonite-K10 (MT), treated under acidic medium and saturated with potassium ions (MTK), was employed in sorption and desorption studies aiming the preconcentration of Cr(III) and the speciation analysis of chromium. The sorption process of Cr(III) was close to 100%, suggesting that MTK was a good material for Cr(III) preconcentration, although, the maximum recovery in HNO3 solution was near 89%. On the other hand, Cr(VI) practically was not retained in MTK, suggesting this material as an appropriate mineral phase to be used in speciation analysis of chromium in aqueous medium.

Tutkimuksen raaka-aineita ja monitieteisiä reseptejä : : III Kulttuurintutkimuksen päivät 14.-15.12.2007 Joensuu

Ajankohtaista

Synthesis and characterization of Fe(III)-piperazine-derived complexes encapsulated in zeolite Y

Zeolite-encapsulated complexes have been widely applied in hydrocarbon oxidation catalysis. The "ship-in-a-bottle" encapsulation of iron(III) complexes containing piperazine and piperazine-derivative ligands in zeolite-Y is described. The flexible ligand methodology was employed and the efficiency and reproducibility of the procedure was investigated. The catalysts were characterized employing several techniques and the results indicate the presence of coordinated and uncoordinated iron(III) ions inside and outside the zeolitic cage.

Highly improved chromium (III) uptake capacity in modified sugarcane bagasse using different chemical treatments

The present paper focuses on improving chromium (III) uptake capacity of sugarcane bagasse through its chemical modification with citric acid and/or sodium hydroxide. The chemical modifications were confirmed by infrared spectroscopy, with an evident peak observed at 1730 cm-1, attributed to carbonyl groups. Equilibrium was reached after 24 h, and the kinetics followed the pseudo-second-order model. The highest chromium (III) maximum adsorption capacity (MAC) value was found when using sugarcane bagasse modified with sodium hydroxide and citric acid (58.00 mg g-1) giving a MAC value about three times greater (20.34 mg g-1) than for raw sugarcane bagasse.

Humanistista ympäristön tarkastelua : : Folklore ja ympäristö : Kansantietouden Tutkijain Seuran III kevätkoulu 9.5.2008, Tieteiden talo, Helsinki

Ajankohtaista

Monitoring of praseodymium(III) ions in aqueous solutions, soil and sediment samples by a PVC membrane sensor based on a furan-triazole derivative

A furan-triazole derivative has been explored as an ionophore for preparation of a highly selective Pr(III) membrane sensor. The proposed sensor exhibits a Nernstian response for Pr(III) activity over a wide concentration range with a detection limit of 5.2×10-8 M. Its response is independent of pH of the solution in the range 3.0-8.8 and offers the advantages of fast response time. To investigate the analytical applicability of the sensor, it was applied successfully as an indicator electrode in potentiometric titration of Pr(III) solution and also in the direct and indirect determination of trace Pr(III) ions in some samples.

Síntese, caracterização e estudo das propriedades de um novo complexo mononuclear contendo quercetina e íon Ga(III)

Flavonoids are one of the most important compound groups applied as medicine given their antioxidant properties, but several intrinsic properties can be improved through structural modifications to their molecules. Here, the synthesis and characterization of a new gallium (III) complex with quercetin is described. Electrochemical properties, as well as antioxidant and cytotoxic activities, were investigated and compared to the free flavonoid molecule. The mononuclear complex obtained, [Ga(C15H9O7)3].2H2O.2CH3OH.CH3CH2OH, seems more active as a DPPH radical scavenger given its lower oxidation potential compared to quercetin. The new complex cytotoxic responses have shown to be more effective than those of the free flavonoid and of lapachol used as a control.

Determinação espectrofotométrica de sulfato em álcool etílico combustível empregando dibromosulfonazo III

A sensitive spectrophotometric method was developed for sulphate determination in automotive ethanol fuel. The method based on the reaction of the analyte with barium-dibromosulphonazo(III) complex lead to a decrease in the magnitude of the absorbance signals monitored at 649 nm. No sample pretreatment is required and the proposed method allows sulphate determination in the 0.45 - 6.50 mg L-1 range with R.S.D. < 2% and limit of detection of 0.14 mg L-1. The method has been successfully applied for sulphate determination in automotive ethanol fuel and the results agreed with the reference chromatographic method.

Preparation and immobilization of diNOsarcobalt(III) complex in zeolite y for the catalyzed production of hydrogen peroxide

A complex cation, diNOsarcobalt(III), [Co(diNOsar)]3+, (diNOsar = 1,8-dinitro-3,6,10,13,16,19-hexaazabicyclo-[6.6.6]eicosane), was synthesized and immobilized in the cavities of a Y zeolite by the reaction of precursor species in the pores of the zeolite. The encapsulated material was compared to the compound diNOsarcobalt(III) chloride, [Co(diNOsar)]Cl3. Both diNOsarcobalt(III) chloride and the zeolite-encapsulated complex, [Co(diNOsar)]3+/zeolite, were obtained in high yield and characterized by ultraviolet-visible and infrared spectroscopy. X-ray diffraction demonstrated the incorporation of the complex cation into the pores of the zeolite. The catalytic production of hydrogen peroxide from oxygenated water confirmed the successful synthesis of the complex diNOsarcobalt(III) immobilized in the zeolite.

Experimento didático de quimiometria para planejamento de experimentos: avaliação das condições experimentais na determinação espectrofotométrica de ferro II com o-fenantrolina. Um tutorial, parte III

The objective of this manuscript is to describe a practical experiment that can be employed for teaching concepts related to design of experiments using Matlab or Octave computing environment to beginners, undergraduate and graduate students. The classical experiment for determination of Fe (II) using o-phenanthroline was selected because it is easy to understand, and all the required materials are readily available in most analytical laboratories. The approach used in this tutorial is divided in two steps: first, the students are introduced to the concept of multivariate effects, how to calculate and interpret them, and the construction and evaluation of a linear model to describe the experimental domain by using a 2³ factorial design. Second, an extension of the factorial design by adding axial points is described, thereby, providing a central composite design. The quadratic model is then introduced and used to build the response surface.

Síntese, liofilização e caracterização de acetato de 57Fe(III)

Iron(III) acetate was synthesized by the reflux method using iron enriched in the 57Fe isotope and the compound processed by freeze-drying. The as-synthesized and freeze-dried acetates were characterized regarding their structural, thermal, vibrational and hyperfine properties. Similar diffractometric and spectroscopic results were found for both materials and also for an industrial acetate made with natural iron. However, the microstructures differed: the as-synthesized compound showed flake morphology with micrometric dimensions, whereas the freeze-dried showed flake morphology with sub-micrometric dimensions. The activation energies for thermal decomposition, calculated from the exothermic events occurring in differential scanning calorimetry measurements, were 100.9 kJ/mol (as-synthesized) and 114.7 kJ/mol (freeze-dried).

Preparation and evaluation of magnetic chitosan particles modified with ethylenediamine and Fe(III) for the removal of Cr(VI) from aqueous solutions

The adsorption of Cr(VI) in aqueous solution by magnetic particles of crosslinked chitosan-ethylenediamine-Fe(III) (MPCh-EDA-FeCL) was studied in a batch system. Fe3+ in the MPCh-EDA-FeCL permitted that adsorption of Cr(VI) occurred with maximum efficiency between pH 3 and 11. The maximum adsorption capacity at pH 7.0 was 81.04 mg g-1 at 25 ºC. The adsorption kinetic process was described by the pseudo-second-order model. Thermodynamic parameters indicated spontaneous, exothermic and chemical adsorption nature. The adsorbent was successively regenerated using a 0.1 mol L-1 NaOH solution. Results were satisfactory for treatment of wastewater from the electroplating industry.