Search Results
Abstract
On evaporation at room temperature of an aqueous mixture of Ln(III) sulphate and ethanolammonium sulphate in a molar ratio higher than 1:12, in the presence of sulphuric acid, double sulphates of Sm, Eu, Ho, Tm, Yb and Y with a waxy feel were obtained. The stoichiometry of the obtained compounds was determined by means of elemental and TG analysis. On the basis of X-ray powder diffraction patterns it was concluded that an isostructural group with a general formula: Ln2(HOCH2CH2NH3)8(SO4)78H2O was obtained. The above compounds have a stoichiometry and a crystal structure different from those of the double sulphates of La, Ce, Pr and Nd with the same monovalent cation, as presented earlier. The thermal decomposition of the investigated compounds in the temperature range from ambient temperature up to 1173 K occurred in a similar way, mainly in three not well-differentiated steps. Lanthanide oxysulphates were obtained as final products.
Abstract
On evaporation of an aqueous mixture of M(II) sulfate (M(II) = Mn, Co, Ni, Cu, Zn or Cd) and benzylammonium sulfate in a molar ratio of 1:2 at room temperature in the presence of sulphuric acid, double sulfates of only Mn, Cu and Cd were obtained. The stoichiometries of the compounds were determined by means of elemental and TG analysis. It was concluded that these compounds have the same general formula: M(C6 H5 CH2 NH3 )2 (SO4 )2 4H2 O. These compounds have the same stoichiometry as that of the corresponding double sulfates with ethanolammonium cation, but have different crystal structures. The thermal decompositions of the investigated compounds in the temperature range from ambient temperature up to 1000C take place in a similar way, in three well-differentiated stages, but with different pathways in the second and third stages. Metal oxides were obtained as final products.
Abstract
On evaporation at room temperature of an aqueous reaction mixture of Ln(III) sulfate and ethanolammonium sulfate in a molar ratio higher than 1∶16, crystal products with a waxy feel were obtained. They were identified by means of the X-ray powder diffraction patterns and it was concluded that they are isostructural. The results of elemental analysis and the mass losses by TG analysis indicated the formation of double sulfates with general formula: (HOCH2CH2NH3)4Ln2(SO4)5·4.5H2O (Ln=La, Ce, Pr or Nd) Their thermal decompositions in static atmosphere in the temperature range from ambient up to 1173 K took place in a similar way, and mainly Ln2O2SO4 was obtained as final product. The exception was the Ce compound, which decomposed to CeO2. The double sulfates decomposed in many not well-differentiated steps. From the mass losses occurring during thermal decomposition, the mode of thermal decomposition was presumed. The X-ray powder diffraction patterns of Ln2O2SO4 (Ln=La, Pr and Nd) show that they are also isostructural.
Abstract
When reaction mixtures of rare earth(III) sulphates and tetramethylammonium sulphate in molar ratios of from 1∶4 to 1∶12 were evaporated at ambient temperature and the concentrated reaction mixture was treated with ethanol, double sulphates with general empirical formula (CH3)4NLn(SO4)22H2O (Ln=Ho−Lu and Y) were obtained as reaction products. The crystalline products were identified by quantitative analysis, X-ray powder diffraction patterns and TG, DTG and DTA analysis. They were found to be isostructural. Their thermal decomposition took place in three stages. The temperature range of the dehydration mainly decreased from Ho to Lu. The thermal decomposition in the second and third stages occurred with many thermal events. As final product, Ln2O(SO4)2 was obtained.
Double sulphates of uranium(IV) with Mg, Ni, Cu and Zn with the general formula MU(SO4)3·8H2O were prepared from their respective metal sulphates. All the four compounds are isostructural and belong to monoclinic system. The thermal decomposition at 850 °C results in a single phase of triuranates MU3O10 which on further heating above 980 °C decompose to give the metal oxide and U3O8 in case of Ni and Zn compounds and MUO4 for Mg and Cu compounds. The activation energy for dehydration of these four compounds has been calculated using non-isothermal thermogravimetric data.
Anhydrous double salts of rubidium sulphate and cesium sulphate with lithium sulphate have been prepared, and polymorphous transformations at+60° and +200° for Rb2SO4 · Li2SO4 and at −75° for Cs2SO4 · Li2SO4 have been disclosed by means of differential thermal analysis. These findings were confirmed by dilatometric measurements and X-ray phase analysis at various temperatures.
Abstract
Gamma-radiolysis of KNO3 in the matrix of some sulfates, viz. Na2SO4, K2SO4, KNaSO4, KNaSO4: Eu, KNaSO4: Ce, K3Na(SO4)2, K3Na(SO4)2: Eu and K3Na(SO4)2: Ce has been studied at an absorbed dose of 30 kGy.G(NO
2
–
) values calculated on the basis of electron fraction in all the sulfates are enhanced significantly. It is also affected by the nature of outer cation and the dopant lanthanide. Electron spin resonance (ESR) and thermoluminescence (TL) measurements show the formation of radical species SO
4
–
, SO
3
–
, O
3
–
, O
2
–
upon 
-irradiation. It is proposed that there radical species may transfer energy and interact with the radical species of nitrate (NO
3
2–
, NO2, NO3 etc.) so as to enhance the decomposition. A possible mechanism has been proposed.
