Abstract

Citrate is distributed widely in the Earth’s surface environments as a biological product released by microbes and plants. Citrate is also often used as a chelating agent for the selective dissolution of iron coatings and free iron oxides in soils. Adsorption experiments of Cs+ and IO3 before and after the complexation of citrate with the pseudoboehmite surface were conducted to evaluate the effects of citrate on the adsorption of these ions on the surface of pseudoboehmite. Additional adsorption experiments of Cs+ and IO3 after the decomposition of citrate adsorbed on the pseudoboehmite surface were also performed to confirm the recovery of the original surface properties. Citrate decomposition was carried out by means of 10% H2O2 treatments at 75°C and pH 5, 7, and 9. The results indicated that citrate complexation decreased remarkably the adsorption of both Cs+ and IO in the pH range 3–10, which was due to a decrease in the number of active charged sites available for adsorption of these ions. Decomposition of citrate adsorbed on the pseudoboehmite surface was found to be complete after three rounds of treatment with 10% H2O2 at 75°C and pH > 7. After the decomposition of citrate adsorbed on the pseudoboehmite surface, the adsorption of both Cs+ and IO3 was restored completely to the initial amounts before citrate complexation, and the inhibition effect of citrate on the adsorption of these ions disappeared under all pH conditions.

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