Efficient synthesis of size-controlled open-framework nanoparticles fabricated with a micro-mixer: route to the improvement of Cs adsorption performance

Abstract

We demonstrated an efficient method for size-controlled nanoparticles of the open framework coordination polymer potassium copper hexacyanoferrate (KCuHCF) using only aqueous solutions of the raw materials and a Y-type micro-mixer. Despite the high viscosity of the synthesized NP slurry, the micromixer provides continuous synthesis without clogging for a few hours with a high flow rate of 100 mL min −1 , i.e. a linear velocity of 94 m s −1 . The crystallite size, evaluated by the Scherrer equation using X-ray diffraction measurements, can be controlled by changing the flow rate. With the highest flow rate of 100 mL min −1 , the smallest NPs with a size of ∼11 nm were obtained, less than half of the NP size obtained using the batch method. By downsizing the nanoparticles (NPs) using the micro-mixer synthesis, the Cs adsorption performance of potassium copper hexacyanoferrate (KCuHCF) was drastically improved. The KCuHCF with the smallest primary particles showed the fastest Cs adsorption: 1.4 times in the saturated capacity, 3.9 times in the distribution coefficient, and 7.7 times in the rate constant for the pseudo-second order adsorption theory, compared with the batch-synthesized sample.

Solvent-assisted synthesis of potassium copper hexacyanoferrate embedded 3D-interconnected porous hydrogel for highly selective and rapid cesium ion removal

“…Though the low intensity peak at around 30° is hardly recognizable in the HPC, the peaks of the HPC and bulk KCuHCF (Fig. 4(a) KCuHCF is determined to be ~9 and ~12 nm for the HPC and the bulk form, respectively, using Scherrer equation at diffraction points of 18° and 36° [35]. In both cases, the calculated values are slightly smaller than the observed particle size in the TEM analysis ( Fig is attributed to lattice water [37].…”

“…Assuming that Cs + adsorption is mainly accompanied by the ion exchange with K + as reported in previous studies [3,35,47], the theoretical ion exchange capacity (TEC) is calculated from the amount of K + in KCuHCF ( Table 2). The HPC shows much higher theoretical adsorption capacity than the bulk KCuHCF, which will be discussed later with the adsorption isotherm study.…”

Unveiling Cs-adsorption mechanism of Prussian blue analogs: Cs+-percolation via vacancies to complete dehydrated state

“…For the separation and decontamination of radioactive caesium, the use of adsorbent is efficient and cost effective. Among various adsorbents, metal hexacyanoferrate (MHCF), [3][4][5][6][7][8][9][10][11][12] zeolite, [13][14][15] calix arenes, [16][17][18] ion exchange resins, 19 metal organic frameworks, 20 ionic crystal, 21 and silicotitanate 22,23 have been surveyed and used as Cs-adsorbents. Metal hexacyanoferrates are known for high selectivity, capacity, and applicability for trace concentrations of cesium.…”

“…5,[38][39][40][41][42][43] The Cscapacity of KCuHCF is as high as 2.5 mmol g À1 . 10 Its selectivity is also sufficient, e.g., it is used for radioactive caesium recovery from seawater for trace monitoring. 44 The elution of CN À at neutral condition was suppressed relative to PB.…”

Radioactive cesium decontamination technology for ash

“…In the case of copper hexacyanoferrate, a Prussian blue analog, we achieved improvement of 7.7 times in adsorption speed compared with the case of conventional synthesis by the reduction of the particle size by micromixer synthesis. [33] The particle size can also be controlled to a certain degree by controlling the ionic valence number or temperature during mixing.…”