Precipitation kinetics; elementary processes

Djarova, M.; Tchaneva, M

doi:10.1016/0022-0248(86)90531-2

Cited by 2 publications

(3 citation statements)

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“…In both the series the supersaturation corresponds to the region of homogeneous nucleiformation of ZnC 2 O 4 ·2H 2 O [28,29].…”

Section: Synthesis Of the Samplesmentioning

confidence: 99%

“…The supersaturation coefficient S amounts to 1936 for the series (1:2), while it is 1369 for the series (1:1). The synthesis in both cases corresponds to the region of homogeneous nucleus formation [28,29], but the different degree of supersaturation will influence the type of initial formed precipitate, mechanism of crystal growth, size and shape of the crystals because of changes in the specific surface energy.…”

Section: Precursors (Mn/znc 2 O 4 2h 2 O)mentioning

confidence: 99%

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Investigation on the catalytic activity of doped low-percentage oxide catalysts Mn/ZnO obtained from oxalate precursor

2008

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“…In both the series the supersaturation corresponds to the region of homogeneous nucleiformation of ZnC 2 O 4 ·2H 2 O [28,29].…”

Section: Synthesis Of the Samplesmentioning

confidence: 99%

Section: Precursors (Mn/znc 2 O 4 2h 2 O)mentioning

confidence: 99%

Investigation on the catalytic activity of doped low-percentage oxide catalysts Mn/ZnO obtained from oxalate precursor

2008

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“…The preliminary experiments and the optical microscopic investigations of the process of crystal phase (ZnC 2 O 4 .2H 2 O) formation as a function of the supersaturation suggest that, at the supersaturations existing in the two media and on mechanical stirring, the nucleation follows a heterogeneous mechanism [19], and the crystallization takes place without any noticeable secondary processes. The size of the crystallites, determining by optical microscopy, obtained is about 0.5-4 µm.…”

mentioning

confidence: 98%

Influence of complex formation upon inclusion of Mn(II), Co(II), Ni(II), and Cu(II) in ZnC₂O₄·2H₂O

Donkova¹,

Pencheva

Djarova

2004

Cryst. Res. Technol.

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The inclusion of 3d-impurities Mn(II), Co(II), Ni(II) and Cu(II) in a crystalline precipitate of ZnC 2 O 4 .2H 2 O is investigated. This study is a part of the systematic one deal with the mechanism of inclusion of 3d-ions in sparingly soluble oxalate systems. The experiments are carried out in bi-end multi-component systems at two different mediums -one with deficiency of oxalate ions, another with excess. Good agreement between included impurity and the concentration of its complex in the solution is established. The stability constant of monooxalato complex affects the impurity inclusion. This effect depends on the medium nature. In the deficiency of oxalate ions the factor determining the inclusion is thermodynamic one -stability of monooxalato complexes. In the excess of oxalate ions inserted amount depends on kinetic factor -the formation rate of these complexes. In the term of that the insertion of Mn(II) is definitely different in the two mediums while that of the Ni (II) does not depend on the medium. The copper shows deviation from overall dependence in the two mediums due to the Jahn-Teller distortion. Its double decreasing insertion in the excess of oxalate ions is related with stabilization of [Cu(C 2 O 4 )2] 2-. The conclusions presume that by varying the background medium and taking in view the ions present in the solution, the amount of inserted impurities can be predicted and controlled. IntroductionThe study of the sparingly soluble oxalate systems is related to their use as precursors in the synthesis of hightemperature superconductive ceramic materials, in the preparation of nanomaterials and a number of other new materials due to the fact that the precipitation processes provide the possibility of controlling the chemical and physical properties of the final products. Oxalate systems are traditionally used for the separation and concentration of elements, especially rare earth and transuranium elements. Detailed studies on the insertion of impurities upon the spontaneous crystallization of sparingly soluble oxalate systems are limited. Some of them are directed to the investigation of the effect of impurities on the properties of the materials [1][2][3][4]. Others deal with the effect of the process kinetics on the inserted amount of impurities [5][6][7] and with the determination of the distribution coefficients [8][9][10][11][12][13]. However, all these studies are carried out on bicomponent systems, comprising just a macro-and a micro-component. For this reason, a detailed investigation of the kinetics of the cocrystallization in oxalate systems directed to the elucidation of the mechanism of inclusion of impurities would clear up this problem. It would undoubtedly help the elucidation of the mechanism of the coprecipitation processes as well, since "the chemistry of oxalate coprecipitatiom processes and the nature of the products have not been well defined" [14]. The present study deals with the sparingly soluble compound ZnC 2 O 4 .2H 2 O, which is used as a starting material for the pr...

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Precipitation kinetics; elementary processes

Cited by 2 publications

References 5 publications

Investigation on the catalytic activity of doped low-percentage oxide catalysts Mn/ZnO obtained from oxalate precursor

Investigation on the catalytic activity of doped low-percentage oxide catalysts Mn/ZnO obtained from oxalate precursor

Influence of complex formation upon inclusion of Mn(II), Co(II), Ni(II), and Cu(II) in ZnC₂O₄·2H₂O

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Precipitation kinetics; elementary processes

Cited by 2 publications

References 5 publications

Investigation on the catalytic activity of doped low-percentage oxide catalysts Mn/ZnO obtained from oxalate precursor

Investigation on the catalytic activity of doped low-percentage oxide catalysts Mn/ZnO obtained from oxalate precursor

Influence of complex formation upon inclusion of Mn(II), Co(II), Ni(II), and Cu(II) in ZnC2O4·2H2O

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Influence of complex formation upon inclusion of Mn(II), Co(II), Ni(II), and Cu(II) in ZnC₂O₄·2H₂O