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Simulated calculation of surface acid-base equilibrium constants and surface species distribution of the nanoceria suspension

De-Hui Sun,Ji-Lin Zhang

As artificial nano-enzymes and effective adsorbents, CeO 2 nanomaterials have been extensively studied for their potential applications in biomedicine and environmental protection. However, the surface acid-base properties of nanoceria suspensions have not been fully studied. In this work, the ceria nanoparticles were synthesized by hydrothermal reaction and calcination . They have a BET specific surface area of 52.01 m 2 /g. FTIR and XPS showed that there are two amphoteric sites (≡Ce(IV)-OH and ≡Ce(III)-OH) and a trace acidic site (≡Ce(III)-OCOOH) which can act as a site probe. The pH range of the acid-base reaction of surface hydroxyl groups of the CeO 2 nanomaterials was determined by Gran plot method. The acidic ionization constants (log K 1 , log K 2 ), site concentration (log C) of two amphoteric surface hydroxyl sites and pH pzc in three KNO 3 supported electrolytes were simultaneously optimized by ProtoFit GUI v2.1 free software using Donnan Shell Model (DSM) and same initial parameters. Their surface species distribution was calculated by PHREEQCI 3.4.0 free software using Donnan model and database (phreeqc.dat). The results show that the proton transfer reaction occurred between ≡Ce(IV)-OH and ≡Ce(III)-OH sites. Therefore, this study reveals the surface acid-base properties, proton transfer behavior and pH pzc of the CeO 2 suspension.