Prompt Description

Surface loading method (suitable for tracing surface passivation processes): This method involves loading ordinary Fe-C electrolytic spheres with ⁵⁷Fe²⁺/⁵⁷Fe³⁺ on the surface, marking only the active sites on the surface of the electrolytic spheres, and is used to track the formation and migration of the surface passivation film. 1. Raw Material Preparation Isotope precursor: ⁵⁷FeSO₄ solution (prepared by reacting ⁵⁷Fe metal powder with dilute sulfuric acid, concentration 100 mM); Basic raw material: Ordinary Fe-C electrolytic spheres (particle size 3~5 mm, pretreatment: soak in dilute hydrochloric acid for 2 h to remove the surface oxide layer, rinse with water until neutral); Auxiliary reagent: Citric acid (complexing agent, concentration 5 mM, enhances the adsorption stability of ⁵⁷Fe on the surface). 2. Loading Steps Surface activation: Place ordinary Fe-C electrolytic spheres in an ultrasonic cleaner, ultrasonically clean with deionized water for 10 min to remove surface impurities, and dry with nitrogen; Isotope loading: Immerse the activated electrolytic spheres in a ⁵⁷FeSO₄-citric acid mixed solution, and oscillate and adsorb at room temperature for 24 h. During this period, sonicate for 10 min every 4 h to promote the diffusion of ⁵⁷Fe²⁺ into the pores of the electrolytic spheres; Reduction and fixation: After adsorption, take out the electrolytic spheres and dry the surface moisture with nitrogen; Washing and purification: Rinse the surface of the electrolytic spheres with deionized water to remove unadsorbed ⁵⁷Fe²⁺ until no ⁵⁷Fe signal is detected in the rinsing solution (verified by ICP-MS).