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Some perovskites exhibit catalytic activity in the abatement of organic pollutants in water. However, their performance decreases over time, possibly due to forms of poisoning, such as carbonate formation. Here, we present the kinetics of carbonate formation on a Ce-doped SrFeO₃ perovskite with formula Sr_0.85Ce_0.15FeO_3−δ (SCF), which can act as a thermocatalyst for the degradation of organic pollutants. The carbonate formation was studied in air, in deionized water, and during degradation of bisphenol A. The formation of SrCO₃ occurred for perovskites in aqueous environments, i.e., when dispersed in water or used as catalysts in the degradation of bisphenol A, while no SrCO₃ was detected for samples stored in air for up to 195 days. SrCO₃ formation was detected using both XRD and ATR-FT-IR, and from the XRD, the crystallite size was found to decrease when carbonates formed. The samples containing SrCO₃ showed an increasing mass loss at >610 °C with increasing time used as catalysts or dispersed in water, showing that SCF reduces its own efficiency during catalytic use. The kinetics of carbonate formation based on the TGA measurements showed that SrCO₃ forms approximately three times faster during the degradation of organic compounds in water compared to SCF dispersed in water. The formation of SrCO₃ in SCF is thermally reversible; thus, the catalyst can resume its activity after heat treatment at 900 °C for 1 h.