Oxalate coprecipitation

In the oxalate coprecipitation method, oxalate acid reacts with metal cations to form the precipitate, which is subsequently calcined to obtain the products. The advantage of oxalate acid as a precipitant is that, unlike hydroxides, oxalates are less sensitive to the treatment conditions, such as washing and drying. In addition, the... 

Nevertheless, the oxalate coprecipitation method has some problems. For example, this method usually results in rodlike doped ceria particles, which are agglomerations of smaller particles with irregular shapes. Hence, the green density of the compact body is relatively low, so it is difficult to fabricate a dense electrolyte film or membrane. In addition, the poor flow of the rodlike powder makes forming difficult. 

FIGURE 1.37 The Arrhenius plot of Ce08Sm0i2Oli9 from different methods (A) solid-state reaction [95] (B) sol-gel process [116] (C) oxalate coprecipitation [91] (D) carbonate coprecipitation, our work and (E) glycine-nitrate process [157]. 

Kramer, G. H. and Davies, J. M., Isolation of strontium-90, yttrium-90, promethium-147, and cerium-144 from wet ashed urine by calcium oxalate coprecipitation and sequential solvent extraction, Anal. Chem., 54, 1428-1431, 1982. 

The eflBciency of these methods of co-precipitation was studied for plutonium, only, by comparing the chemical recovery of the original yield monitor with that of a second (and different) plutonium isotope yield monitor added to the acid solution of the co-precipitated hydroxide or oxalate (6). This second monitor shows all losses following the coprecipitation step. The eflBciency of the hydroxide precipitation for plutonium extraction was in the range 70-80%. That for the oxalate coprecipitation was typically 75-85%. 

I) Oxalate Coprecipitation. A insoluble coordination precursor compound (a trioxolatoaluminate anion complex) for lithia-stabilized /("-alumina that has the proper concentrations of Na and Li cations can, in principle, be prepared by the following precipitation reaction from an aqueous solution ... 

La(N03)3-Ni(N03)2] and the other microemulsion containing the oxalate precipitant as ammonium oxalate or oxalic acid. Metal oxalate coprecipitates were formed that lost their colloidal stability after about 2 h, as manifested by the observation of flocculated materials. 

Calcination of the oxalate coprecipitates readily yielded phase-pure perovskite-type complex metal oxides. The required calcinations for the microemulsion-derived mixed oxalates were 100-250"C below the temperatures used for oxalates prepared in homogeneous aqueous solutions. 

Barium iron oxalate coprecipitate, well dispersed, dp = 10-20 nm calcined (950"C) product (BaFe]20 9), dp=6Q nm [109]. 

Figure 1.23 The fracture strength of Ce02)o.go LnOi 5)0.20 (Ln=Y, Cd, and Sm) ceramics prepared by solid-state reaction ofCe02 and the respective rare earth oxide powder and by an oxalate coprecipitation method [272],...

Park Y-U, Kim J, Gwon H, Seo D-H, Kim S-W, Kang K (2010) Synthesis of multicomponent olivine by a novel mixed transition metal oxalate coprecipitation method and electrochemical characterization. Chem Mater 22 2573-2581... 

Dang et al. (2000) increased the sensitivity of NAA for Th by separating the indicator radionuclide, Pa, using co-predpitations with manganese dioxide and barium sulfate and determined Th in total diet samples. A similar postirradiation procedure was coupled to the following pre-irradiation separation and concentration of Th (PC-RNAA) by H5llriegl et al. (2005) to increase the sensitivity of the method for the determination of urinary Th excretions. The pre-concentration procedure consisted of phosphate and caldum oxalate coprecipitations. The detection limit of Th in the urine sample was about 10 pg (0.04 jiBq). 

Zhao Q, Ye N, Li L, Yan F (2010) Oxalate coprecipitation process s5mthesis of 5 V cathode material LiNio,5Mni.504 and its performance. Rare Met Mater Eng 39 1715-1718... 

Probably the most common simple group separation is that for the rare-earth (RE) elements. Several workers have used either lanthanum fluoride or oxalate coprecipitations to isolate the RE elements from irradiated rock prior to determination of as many as 14 elements by Ge(Li) spectrometry. — ... 

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