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Investigation on the Effect of Method of Synthesis on the Thermal Decomposition of Ceria Nanostructures
Published in Satya Bir Singh, Prabhat Ranjan, A. K. Haghi, Materials Modeling for Macro to Micro/Nano Scale Systems, 2022
Figure 2.9 shows DSC curves for each cerium oxalate H1, H2, H3, and H4 at a β value of 2, 4, 6, and 8 K/min in the atmosphere of N2. During the thermal decomposition process, the self-generated reaction condition has a predominant role on controlling the reaction path ways [41]. Change in the internal gaseous pressure can alter the smoothness of the heat transfer process, which affects kinetics of the reaction. Cerium oxalate decomposes to ceria through multistage decomposition stages. Due to the experimental inconvenience of separately tracking the component process, deconvolution of overall kinetic information into the reaction component is the only possible method for interpreting the multistage reaction scheme [42, 43]. Each kinetically resolved stage is studied by formal kinetic analysis. Figure 2.10 shows the typical deconvoluted DSC curve of sample H4. Apparent activation energy for each independent process was measured by the isoconversional Friedman method. The determination of Ea values for each stage was based on ( 5). Plots of ln (dα/dt) versus T−1 (Friedman plot) [44–46] were carried out for the series of kinetic data recorded at different α values under linear nonisothermal condition. By this method, the coefficient of linearity was found to be near to unity. From the slope of the plot, the values of Ea can be evaluated.
Recovery and Recycling of Cerium from Primary and Secondary Resources- a Critical Review
Published in Mineral Processing and Extractive Metallurgy Review, 2020
The oxidation of Ce(III) to Ce(IV) and the precipitation of Ce(IV) was completed by the addition of a mixture of 30% KMnO4 and Na2CO3. The precipitated composed of ceric hydroxide and manganese dioxide was dissolved in a 3.0 M HCl at 70°C for 1h. Cerium is then selectively precipitated (>98%) from the leach solution as cerium oxalate by the addition of 10% oxalic acid solution or as cerium hydroxide by 3M NH4OH at a controlled pH 8. Finally, 99% pure CeO2 is obtained by calcination at 900°C for 1 h. Recently, Tar et al. (2017) investigated the processing of rare earth oxide from monazite using NaOH digestion at 140°C for 2 h followed by dissolution in hydrochloric acid. The reactions of digestion and dissolution are shown by the Equations (5) and (6) respectively: