Effect of high-energy milling and thermal treatment on the solid-phase reactions in apatite–ammonium sulphate system

The phosphorous fertilizers are a product of natural sedimentary phosphorite ores. Using this raw material to produce phosphoric acid and classic phosphorous fertilizers has generated well-known ecological problems. A new and perspective way to use the same materials is creating a new type of time-delayed fertilizers applying high-energy milling (HEM) activation method. The impact of the mechanical forces over the solids is mostly revealed through the changes of the quantities being related to the energetic stability and reactivity of the solid phase. The aim of this work is to report the results from the investigation on the chemical and thermal reactions in composites of natural apatite , which are HEM activated for different times and thermally treated, (from Tunisia) and ammonium sulphate. The Tunisian phosphorite belongs to the ‘basic’ apatites having a Ca/P ratio of 1.70–1.77 and is characterized by a complex mineral composition with major component carbonate-fluorapatite. The used ammonium sulphate—(NH₄)₂SO₄ is obtained as a by-product from cleaning industrial waste gases, using e-beam technology. The composites of Tunisian phosphorite ores and ammonium sulphate, mixed in a mass ratio 1:1, were HEM activated during 10 min to 50 h with 20 mm Fe-milling bodies and temperature treated up to 1,100 °C. As a result, the chemical properties of the treated composites changed. Proofs were found for (i) formation of new phases during HEM activation such as NH₄Ca(PO₃)₃ (NH₄)₂CaH₄(P₂O₇)₂, (NH₄)₂Ca₃(P₂O₇)₂.6H₂O, CaH₂P₂O₇ and α-Ca₂P₂O₇; and (ii) decreasing of temperature intervals of phase changes in comparison to untreated composite.     

Determination of manganese by a new spectrophotometry method using toluidine blue

The formation of the ion associate of manganese(VII) with Toluidine Blue is studied spectropho-tometrically in water-organic media. The composition of the complex is established as TB: MnO₄ ^- =1:1. The molar absorptivity ε290 = (2.46 ± 0.09) × 10⁴ L/mol cm is determined. The selectivity of the reaction is studied and the method for determination of manganese(VII) 0.1—2.9 fug/mL is developed. Investigations of extraction in the system discussed were carried out. The characteristic values for the extraction equilibrium and the equilibrium in the aqueous phase were determined: extraction constant K_ex = 1 × 10⁴, distribution constant KD = 26.08, and association constant β = 3.83 × 10². A rapid and selective extractive-photometric method for the determination of manganese(VII) in plants was proposed.     

Extraction of chromium(VI) with blue tetrazolium chloride and tetranitrotetrazolium blue chloride

The optimum conditions for extraction of microquantities of chromium(VI) as an ion-association complex with blue tetrazolium chloride (BTC) and tetranitrotetrazolium blue chloride (TNBT) has been determined. The extracted species was a 1: 2 of the BTC and TNBT cation and the chlorochromate anion. Beer’s law was obeyed in the range of 0.04–0.8 μg/mL Cr(VI) for BTC and 0.1–1.6 μg/mL Cr(VI) for TNBT. The molar absorptivities were ?₂₅₅ = 7.77 × 10⁴ L/(mol cm) (for BTC) and ?₂₇₅ = 2.04 × 10⁴ L/(mol cm) (for TNBT). Sandell’s sensitivity of the systems were found to be 6.69 × 10^?4 μg/cm² (for BTC) and 2.55 × 10^?3 μg/cm² (for TNBT). Limit of detection (LOD) is 8.55 ng/mL and limit of quantitation (LOQ) is 0.028 μg/mL Cr(VI) for BTC. For TNBT, LOD is 0.031 μg/mL and LOQ is 0.103 μg/mL. The characteristic values for the extraction equilibrium and the equilibrium in the aqueous phase have been determined. A sensitive method for determination of trace of chromium(VI) in plants has been developed.     

Theoretical and spectroscopic study of 2-substituted indan-1,3-diones: a coherent picture of the tautomeric equilibrium

The structures of some 2-substituted indan-1,3-diones are investigated in the gas phase and solution using quantum chemical calculations and spectral (NMR, IR, and UV) measurements. The influence of the substituent at the 2-position on the tautomeric equilibrium of 2-substituted indan-1,3-diones in solvents with different polarity is evaluated. It is shown that the equilibrium in 2-formyl-indan-1,3-dione and 2-acetyl-indan-1,3-dione is shifted to the 2-hydroxyalkylidene-indan-1,3-dione tautomer, while 2-carboxyamide-indan-1,3-dione exists as a mixture of two tautomers, 2-(hydroxyaminomethylidene)-indan-1,3-dione and 2-carboamide-1-hydroxy-3-oxo-indan, with extremely fast proton transfer between them. The situation for 2-carboxy-indan-1,3-dione is quite different - on the basis of the analysis of the obtained results, the possible existence of an anionic form of 2-carboxy-indan-1,3-dione in solution can be inferred.     

Vibrational characterization and prooxidant activity of newly synthesized dysprosium(III) complex

The dysprosium(III) complex of 5-aminoorotic acid (HAOA) was synthesized by reaction of the respective inorganic salt in amounts equal to ligand, molar ratio of 1:3. The structure of the complex was determined by means of elemental analysis, FTIR and FT-Raman spectroscopies. Significant differences in the IR and Raman spectra of the complex were observed as compared to the spectra of the free ligand. Detailed vibrational analysis of HAOA and Dy(III)-AOA systems revealed that the binding mode in the complex was bidentate through the carboxylic oxygen atoms. Dy(III) complex of 5-aminoorotic acid (DyAOA) exhibited prooxidant properties in the presence of the model system X/XO. In the DyAOA complex, the ion diminished the antioxidant properties of the AOA ligands.     

Tautomerism in 5-Bromouracil: Relationships with Other 5-Haloderivatives and Effect of the Microhydration

A comparative analysis on the effect of the water on the molecular structure and spectroscopy of 5-halogenated uracils was carried out. Solvent effects were considered by using a variable number (1–10) of explicit water molecules surrounding the 5-halouracil derivatives in order to simulate the first hydration shell. More than 300 cluster structures with water were analyzed. B3LYP and MP2 quantum chemical methods were used. For cases where literature data are available, the computed values were in good agreement with previous experimental and theoretical studies. Several general conclusions were underlined.     

The electron impact mass spectra of some rotenoid derivatives

The fragmentation behaviour of several rotenoids functionalized in the alicyclic portions of the molecule is described.     

Extraction-radiochemical study of the ion-association complex of antimony (V) with tetrazolium violet and its thermal behavior

The optimum conditions for extraction of ion-associated complexes (IAC) formed from the tetrazolium salt-tetrazolium violet and Sb(V) in hydrochloric acid medium have been studied. An isotope of antimony (¹²⁵Sb) was used for determination of the recovery factor (R%) and distribution ratio (D_Sb). The thermal behavior of the antimony complex with tetrazole violet was studied using differential thermal and thermogravimetric analysis.     

Interaction of hydrogen sulfide with molybdophosphoric heteropolyacid

The effect of hydrogen sulfide on P–12Mo heteropolyacid has been studied using ESR, IR spectroscopic and thermal analysis methods. It has been established that hydrogen sulfide can be chemisorbed like water and no entering of sulfur into the anion structure takes place.

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, P–12Mo . , . .

     

4,4-Bis(methylthio)azetidin-2-ones as synthons of 1,2- and 1,3-dicarbonyl systems

The importance of β-lactams as synthetic building blocks has been widely recognized in organic synthesis due to possible ring cleavage at any of the four single bonds of the β-lactam ring. We now report reactions involving breaking of the N1-C4 bond in differently substituted at C3 4,4-bis(methylthio)azetidin-2-ones, leading to formation of 1,2- and 1,3-dicarbonyl systems.