Characterization of resorcinol–formaldehyde hydrogel as adsorbent for cesium ion

Abstract

We evaluated the performance of a resorcinol-formaldehyde (RF) hydrogel as an adsorbent for removing aqueous cesium ions (Cs + ), by synthesizing cylindrical pellets of RF gels under different molar ratios (R/C) between resorcinol (R) and sodium carbonate (C) as the catalyst for the sol-gel polycondensation in the range from 2.5 to 400. The RF gel prepared at R/C = 2.5, containing the greatest amount of sodium ion (Na + ), had the greatest Cs + adsorption amount (0.660 mmol g −1 ), because Cs + could be adsorbed on the network structure in the gel through exchange with Na + at an equal molar ratio, but with the smallest effective diffusion coefficient of Cs + (1.45 × 10 -12 m 2 s −1 ). Kinetic analyses based on the Dryden-Kay and intra-particle diffusion models revealed that the diffusivity of Cs + in the RF gel depended strongly on the density of the network structure, which can be controlled by varying the R/C ratio.

Experimental and Modeling Studies of Sr2+ and Cs+ Sorption on Cryogels and Comparison to Commercial Adsorbents

“…The diffusion coefficients obtained for AAC and SAC cryogels was found in the range of 1.01 × 10 −9 −8.81 × 10 −10 m 2 s −1 and depends on the composition, cross-linking percentage, and ionic strength of the immersion solution. Taguchi et al 28 synthesized resorcinol−formaldehyde hydrogel with various resorcinol (R) (main monomer) and sodium carbonate (C) (reaction catalyst) ratios for cesium uptake. It was found that, when the R/C ratio (mol/mol) was 2.5, the diffusion coefficient was 1.45 × 10 −12 m 2 s −1 , while with increase of the R/C ratio, the diffusion coefficient increased and reached 7.11 × 10 −12 m 2 s −1 .…”

“…Typical adsorbents such as activated carbons (AC), natural zeolites, and clays have been used, but they are often characterized by low adsorption capacities or the need to be chemically treated to acquire desirable adsorption properties. − Natural sorbents like zeolites and AC usually show low removal capacities in the ranges of 1.3–10 mg/g for Sr 2+ ions and 0.7–51 mg g −1 for Cs + . Synthetic polymers like hydrogels and cryogels can reach much higher removal capacities, up to 312 mg g −1 for Sr 2+ and 420 mg g −1 for Cs + ions. ,,− A list of literature works investigating Cs + and Sr 2+ ions adsorption from aqueous media onto different sorbents is reported in Table S1.…”

Effect of the Resorcinol/Formaldehyde Ratio and the Temperature of the Resorcinol–Formaldehyde Gel Solidification on the Chemical Stability and Sorption Characteristics of Ion-Exchange Resins

“…It is possible to obtain new properties for the RFR by changing the initial components while preparing the resorcinol–formaldehyde (RF) polymer gel. Taguchi et al [ 18 ] synthesized the resorcinol–formaldehyde (RF) hydrogel with a different ratio between resorcinol and sodium carbonate (R/C) serving as a catalyst for the polymerization reaction. The authors concluded that along with the increase in the R/C ratio, the hydrogel absorption capacity decreases, and the rate of the ion exchange process, on the contrary, increases.…”