Abstract
Since Prussian blue (PB, or FeHCF) and its analogues (PBAs or MHCF (M=Ni, Zn, Co, Cu, etc.)) are well known as adsorbents of some ions or small molecules, especially, alkali metal cations such as Na^+, K^+, and Cs^+, these materials had been regarded as promising adsorbents to remove a radioactive Cs^+ from radioactive wastes. However, to adsorb a radioactive Cs^+ with MHCF causes the increase of radioactive wastes, so it is important to develop a reusable new system, or a controllable Cs^+ adsorbing/desorbing system. We succeeded in preparing nanoparticle inks of MHCFs, which are able to disperse into several solvents, and able to form films with the nanoparticle inks by conventional wet processes. Then we prepared the CuHCF nanoparticle films on Au/quartz substrates by a spin-coating method, and attempted to control the adsorption or desorption of alkali metal cations electrochemically. The electrochemical redox by cyclic voltammetry (CV) and adsorption/desorption measurement by electrochemical quartz crystal microbalance (EQCM) were carried out synchronously. For example, a copper substituted PBA, CuHCF films showed stable reversible redox signals for Na^+, K^+, and Cs^+ in the aqueous solution dissolving the corresponding nitrate salts (NaNO_3, KNO_3, and CsNO_3) as electrolytes. The redox potentials were different to each other, +0.55 V, +0.65 V, and +0.90 V (vs. SCE) for Na^+, K^+, and Cs^+, respectively. According to EQCM measurement, the mass changes followed by a cation adsorption/desorption occurred at the above-described potentials respectively and the ratios of mass showed almost 1:1:6 for Na^+:K^+:Cs^+. The difference of redox potentials and good duplicability of CV and EQCM signals suggests the possibility of electrochemically controllable cation adsorbing/desorbing systems.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have