イオン交換樹脂を含む懸濁水への難溶性無機化合物の溶解(第九報) : モリブデン酸カルシウム

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Disolution process of CaMoO_4 in aqueous suspension containing H-R, a strongly acidic ion exchange resin with hydrogen form, was studied mainly by chemical analysis of the liquid phase. Several analytical methods such as titration using NaOH solution or H-R suspension, calorimetry, thermal analysis and XRD were carried out in order to confirm the dissolution mechanism. CaMoO_4 does not dissolve according to the equation, CaMoO_4+2(H-R)→Ca-R_2 + H_2MoO_4 owing to the aggregation to polyanion by the acidification of MoO_4^<2->. By considering the experimental results, it is concluded that CaMoO_4 dissolves to yield an acid having a composition to be H_4Mo_8O_26. The dissolution process of CaMoO_4 and alkali titration for the resultant acid are summerized as follows : (1) The dissolution process of CaMoO_4 as a function of H-R (g) is expressed by the following two-stages reactions, 8CaMoO_4+12(H-R)→Ca_2Mo_8O_26(aq)+6(Ca-R_2)+6H_2O Ca_2Mo_8O_26(aq)+4(H-R)→H_4Mo_8O_26(aq)+2(Ca-R_2). With incresing the amount of H-R, the concentrations of Ca and Mo increase at the initial stage which is followed by the decrease in Ca^<2+> concentration at the final stage. The formation of the intermediate, Ca_2Mo_8O_26(aq), is proved by the experimental fact of ca. 4 of Mo/Ca molar ratio. (2) The neutralization between the final acid product, H_4Mo_8O_26(aq) and NaOH solution proceeds according to the following two-stage reactions, H_4Mo_8O_26(aq)+4NaOH(aq)→Na_4Mo_8O_26(aq)+4H_2O, Na_4Mo_8O_26(aq)+12NaOH(aq)→8Na_2MoO_4(aq)+6H_2O.
社団法人日本セラミックス協会の論文
1995-08-01

イオン交換樹脂を含む懸濁水への難溶性無機化合物の溶解(第九報) : モリブデン酸カルシウム

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