On the thermal decomposition of alkali persulfates by derivatograph

Barboott, Mahmood M.; Jasim, Fadhil

doi:10.1016/0040-6031(76)80035-4

Cited by 26 publications

(11 citation statements)

References 5 publications

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“…Several investigators have used TG, DTG and DTA to study the non-isothermal (dynamic) decompositions of pure Na.,S2Os and K2S2Os and the decompositions catalyzed by metal oxides such as CuO, TiO2, Zn [1][2][3][4][5], oxides with a corundum structure such as A1203, Cr203 and F%Oa, and oxides with a cubic structure such as CdO [6], to establish their catalytic effects on the decomposition and concluded that these effects increased with the p-type semiconductor characters of the catalyst, thereby supporting previous findings [6].…”

mentioning

confidence: 52%

“…Further on, the solid-phase transition of NaSm(SO4)2 resulting in the endotherm in the DTA curve at 595 ~ is actually the Tm of this double sulfate. However, the last endotherm in the DTA curves corresponds to the Tm of Na2SO4 produced as a result of the thermal decomposition of the unreacted Na2S2OT, whereas the first sharp endotherm corresponds to the exothermic decomposition [1 ] of Na2SzOs. In fact, this exotherm is due to a secondary process in which Oz molecules are formed from atomic oxygen.…”

Section: Binary Systemsmentioning

confidence: 97%

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Thermal and x-ray studies of binary rare earth sesquioxides — Alkali metal persulfate systems

Jasim

Idan

1981

Journal of Thermal Analysis

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Three binary systems, each consisting of mixtures of different molar ratios of a rare earth (4] metal) sesquioxide and sodium or potassium persulfate (peroxodisulfate) have been investigated under static (air) atmospheres using a derivatograph. For each system (RzO a --MeSzOs, where R is Sin, Gd, or Dy, and M is K or Na), the molar ratios that represent stoichiometric reactions were fixed. Calculations were based on data obtained from T, TG, DTG and DTA curves. Intermediate and final products were mainly identified by X-ray diffractometry. Double salts of Sm, Gd, and Dy were thermally prepared by solid-state reactions. It was found that one such double salt KDy(SO4)e, forms a eutectic mixture with K2SO a and also that both Gd and Dy sesquioxides behave as p-type semiconductors and therefore exhibit catalytic activities towards the thermal decomposition of persulfates and pyrosulfates. OptimaI catalysis was obtained with molar ratios of 1 : 3. The activities increased as the ionic radii of these metals decrease: Sm, Gd, Dy.Several investigators have used TG, DTG and DTA to study the non-isothermal (dynamic) decompositions of pure Na.,S2Os and K2S2Os and the decompositions catalyzed by metal oxides such as CuO, TiO2, Zn [1-5], oxides with a corundum structure such as A1203, Cr203 and F%Oa, and oxides with a cubic structure such as CdO [6], to establish their catalytic effects on the decomposition and concluded that these effects increased with the p-type semiconductor characters of the catalyst, thereby supporting previous findings [6].It was found that some of the rare earth sesquioxides act as semiconductors at high temperatures. For instance, both Gd2Oa and Dy~O3 exhibit p-type semiconductor activities at pressures of 10 -9"~ and 10 -11'3 atm and at temperatures of 727-1177 ~ and 727-t377 ~ respectively [8]. Furthermore, it has been shown [7,9] that Sm203, Gd2Oa and Dy2Oz exert catalytic effects by lowering the thermal decomposition temperatures of lithium perchlorate and lithium carbonate.A thermogravimetric study of the thermal decomposition of formic acid over lanthanide oxides such as Sm2Oa and Dy2Oa revealed that the decomposition occurs at 300-400 ~ via a lanthanide formate intermediate, which transformed to an oxycarbonate and then cracked to liberate COz, with reformation of the lanthanide oxide [10].The present paper deals with the influences of the three sesquioxides on the decompositions of the peroxodisulfates of sodium and potassium and their

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mentioning

confidence: 52%

Section: Binary Systemsmentioning

confidence: 97%

Thermal and x-ray studies of binary rare earth sesquioxides — Alkali metal persulfate systems

Jasim

Idan

1981

Journal of Thermal Analysis

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“…The first of these, at 330 ~ relates to the B-a phase transition [8], and the second, at 382 ~ to the fusion of potassium pyrosulfate [5]. Neither of these peaks appeared in the DTA curves at any of the molar ratios studied.…”

Section: V205-k2s2os Systemmentioning

confidence: 77%

“…1. Pure K2S~O3 begins to lose oxygen slowly at 182~ the process suddenly accelerates above 190 ~ , and it finishes at 200 ~ [5]. The DTG curve of the reaction indicates a single-step decomposition with a well-defined peak in the temperature range involved.…”

Section: V205-k2s2os Systemmentioning

confidence: 96%

Thermal and X-ray diffraction investigations of vanadium(V) oxide-alkali persulfate binary systems

Jasim

Jaffer

Barbooti

1981

Journal of Thermal Analysis

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Thermoanalytieal investigations of the VzO 5-K2S~O 8 system have revevled that, m the presence of excess amounts of VzO~, the initial decomposition temperature is lowered compared to that of the pure salt, An explanation for this lowering is based on the interaction between V2On and the peroxo group of the persulfate ion. The reaction however, is, not unimolecular. The presence of an unknown potassium sulfate complex of V(V) with a catalytic character is indicated by XRD patterns obtained for samples heated up to 410% It has been found that the formation of KzVOs, KV(SO4)2, K~VsO14 and K4VxoOz7 depends on whether V205 or K2SO 4 is present in excess during thermal decomposition.Sharp d-lines for unknown phases are identified. V~Os is found to behave differently towards sodium and potassium persulfates.Compounds such as a-NaVO3, NaVOs, NaV308 and NaV6Oa5 are obtained on thermal analysis of various molar ratios of the V2Os--Na2S2Os system.

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“…The peroxodisulfates of ammonium, sodium, and potassium are white, crystalline, and stable under dry conditions. The salts decompose on heating in two steps: first the formation of pyrosulfates and oxygen and then upon further heating the decomposition of the pyrosulfate into sulfate and sulfur tri-and dioxide [110], [111]. The decomposition temperatures increase in the series NH 4 þ < K þ < Na þ , and decrease with increasing moisture content.…”

Section: Propertiesmentioning

confidence: 99%