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Heterojunction Perovskite Oxide/ Halide Materials for Photocatalytic Solar Hydrogen Production
Published in A. Pandikumar, K. Jothivenkatachalam, S. Moscow, Heterojunction Photocatalytic Materials, 2022
Nagalingam Rajamanickam, S. S. Kanmani, Kathirvel Ramachandran
This method is a simplistic and appropriate way to prepare the semiconductor metal oxide precipitation by using a triggering agent. Triggering agents such as oxalic acid, ammonia, ammonium oxalate, sodium hydroxide, urea, and ammonium carbonate are used to make precipitates. In this method, the precursor solution with a reactant agent was stirred for desirable time, washed with washable solvent, and then the precipitates were tried and annealed to obtain desired materials. Moreover, for successful yielding of perovskite/semiconductor metal oxides with preferred particle size and morphology, various parameters are optimized (temperature, soluble homogeneity, pH, mixing rate, and concentration). This method is used to obtain the homogeneous and pure catalyst materials by a controlled reaction. BiFeO3, [183], BaSnO3 [97], H2LaNb2O7:In [184], and BaTiO3 [185] were prepared by the co-precipitation method.
Introduction
Published in Jamie Bartram, Richard Ballance, Water Quality Monitoring, 1996
Jamie Bartram, Richard Ballance
✓ Ammonium oxalate solution, 5 per cent. Dissolve 10g of ammonium oxalate monohydrate, NH42C2O4⋅H2O, in 250ml of distilled water. Filter the solution if it contains a precipitate.
Preparation of Bulk and Supported Perovskites
Published in L.G. Tejuca, J.L.G. Fierro, Properties and Appbications of Peroushite-Type Oxides, 1992
The oxalate coprecipitation route is a relatively simple method for the synthesis of YBaCuo powders (14-16). Starting from salt solutions, addition of oxalic acid or ammonium oxalate in basic medium leads to precipitation of a complex cationic oxalate or a mixture of several oxalates. Figure 2 shows a flow sheet of the process. The solvent must be organic rather than water, because the solubility of oxalates is much lower in that medium, thus assuring a correct stoichiometry. The oxalate route allows obtaining overall stoichiometric precipitates, but fails in obtaining individual precipitated particle stoichiometry (14). An additional problem is that the formed barium oxalate transforms to barium carbonate at temperatures at which the formation reaction progresses slowly or does not even begin. Although the reactivity of the emerging barium carbonate is very high and the synthesis proceeds rapidly, it is necessary to Table 1. Processing Methods for Preparing High-T C Superconducting ceramics
Theoretical analysis and experimental Validation of selective oxalate precipitation
Published in Mineral Processing and Extractive Metallurgy, 2022
S. Ghasemi, N. Rafiei, A. Heidarpour
The advantages of precipitation in the form of oxalates over the other precipitating anions (e.g. hydroxides and carbonates) include: Convenient and efficient extraction of metal ions under optimal conditions on account of the reasonably low solubility product of oxalates (Gavris et al. 2008).The oxalate precipitation is successful even in acidic solutions at low pH values. While, precipitation of hydroxide or carbonate compounds, requires high pH values. In other words, an almost stoichiometric amount of oxalate ion is enough to precipitate the metal content of the solution.The crystalline oxalate precipitate can be compared with the amorphous forms of the hydroxides, carbonates, and basic carbonates due to the low volume of the precipitate and chemical stability at atmospheric conditions (Gavris et al. 2008).The metal-oxalate precipitate can be easily separated by filtration (Gavris et al. 2008). In comparison, the filterability of hydroxide precipitates is very low (Balintova and Petrilakova 2011).Crystallised oxalates can be easily decomposed to pure oxides at low temperatures (about 300°C) for subsequent applications. In other words, oxalate precipitation can be employed as an intermediate process step and the metal(s)-oxalate precipitate can easily be processed to obtain the desired metal compounds as finished products (Gavris et al. 2008; Naznin et al. 2017).The required reagents for oxalate precipitation are economically accessible, easy to obtain and transport (Gavris et al. 2008). Several precipitating reagents like oxalic acid (Sohn et al. 2006; Gavris et al. 2008; Sadanandam et al. 2008; Meshram et al. 2015; Nayaka et al. 2016; Naznin et al. 2017; Sinha et al. 2017), ammonium oxalate (Chen et al. 2011; Fernandes et al. 2013; Chen and Zhou 2014; Chen, Zhou et al. 2015; Chen, Chen, et al. 2015) or sodium oxalate (Brooks 1993; Linneen et al. 2019) can be exploited as the source of oxalate ion for oxalate precipitation process.