Kinetics and Thermodynamics of Sulfate Adsorption on Magnetite at Elevated Temperatures
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Magnetite is a major corrosion product of carbon steel that forms deposits in the steam generators in water-cooled nuclear reactors. Sulfate is present as an impurity in the steam generator feed water and accumulates in the magnetite deposits, leading to formation of acidic crevices, corrosion and stress corrosion cracking of steam generator tubing. Reliable adsorption data are required to understand material degradation of steam generator tubing. Sulfate adsorption onto magnetite has been studied at temperatures from 25 to 300 °C as a function of pH, and chloride and sulfate concentrations. The results show that adsorption decreases with increasing pH and ionic strength, and adsorption followed the Langmuir adsorption isotherm. Overall, sulfate adsorption onto magnetite is endothermic and the enthalpy of adsorption depends on the pH and ionic strength of the solutions. The adsorption behavior of sulfate onto magnetite is explained through outer-sphere and inner-sphere adsorption.
KeywordsMagnetite Adsorption Sulfate High temperatures Enthalpy change
This work was financially supported by Federal Science and Technology Programs at Canadian Nuclear Laboratories through the work package FST-51100.01.11.
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