Organically modified clay with potassium copper hexacyanoferrate for enhanced Cs⁺ adsorption capacity and selective recovery by flotation

Abstract

The selective capture of mobile radioactive nuclides, such as 137 Cs + , is crucial to the clean-up and remediation of contaminated environments. While remediation remains a challenging task, the current study considers novel organo-clay composites containing potassium copper hexacyanoferrate (KCuHCF) as a viable option for large-scale clean-up. A threestep synthesis has been demonstrated whereby pristine montmorillonite clay was readily modified to incorporate KCuHCF nanoparticles for enhanced and selective Cs + removal from aqueous environments. Alkyldiamine (DT) was used as an organic modifier to intercalate the clay and provided chelating sites to anchor copper onto the clay matrix, from which KCuHCF nanoparticles were subsequently grown in-situ via the coordination of hexacyanoferrate precursors with the immobilized copper ions. The organo-clay-HCF composite particles exhibited a superior Cs + adsorption capacity (qm = 206 mg/g), twice that of the pristine clay. The enhanced performance also extended to high Cs + selectivity in seawater, with the organo-clay-HCF composites demonstrating Cs + selectivity values in excess of 10 5 mL/g, two orders of magnitude greater than the pristine clay. Organo modification of the clay particles reduced the particle wettability, thus facilitating the separation of Cs-loaded composite particles from aqueous environments by collector-less flotation. Batch flotation experiments showed recovery efficiencies of the Cs-loaded composite particles of up to 90%, which was in great contrast to the low recovery of less than 15% for the Cs-loaded pristine montmorillonite. The current study provides a new concept for the treatment of contaminated aqueous environments.

The effect of pre-activation and milling on improving natural clinoptilolite for ion exchange of cesium and strontium

“…Additionally, the sodium and hydrogen ions will be electrostatically attracted to the negatively charge surface of the clinoptilolite, leading to further adsorption. For highly expandable clays, electrostatic surface interactions can lead to a distinct two layer adsorption model, where firstly, inter-layer ion-exchange sites control interaction, before secondly, surface interactions dominate [44]. While clinoptilolite and zeolites more generally, do not…”

“…Another technique that may potentially be used to increase natural ion capacity, is to expose additional exchange sites through increasing the surface area to volume ratio by milling [39,40]. While fine milled particles would not be practically used in traditional ion-exchange columns, there has been increasing interest in combining batch adsorption contact tanks with flotation, giving highly efficient uptake and rapid de-watering of nuclear effluents [41][42][43][44].…”

Synthesis of functionalized porous montmorillonite via solid-state NaOH treatment for efficient removal of cesium and strontium ions

“…Alternatively, natural clays are readily abundant and inexpensive, demonstrating reasonable ion exchange capacity [18]. Specifically, montmorillonite clay (MT) having an expandable layered structure has received significant attention owing to its high cation exchange capacity [19,20]. A unit layer of MT is composed of an octahedral AlO 6 sheet sandwiched between two tetrahedral SiO 4 sheets, with numerous exchangeable cations such as Na + , Mg 2+ , Ca 2+ , and Fe 2+ , existing between the negatively-charged unit layers [18,19,21].…”

Study of effect of phosphate and uranium ions on the thermal properties of surfactant-modified natural red clay using TG–FTIR–MS techniques

“…Organoclays are widely used as adsorbents in the industry and in waste treatment [1][2][3][4][5]. The potential application of organically modified clays in the removal of U(VI) ions from the aqueous phase has been reported by many authors [6][7][8][9][10][11][12] and is very important from the practical viewpoint, especially with respect to decontamination of nuclear wastes [13][14][15][16][17][18][19][20][21][22] and use of barrier materials in radioactive waste repositories [23,24]. The use of unmodified clays in repositories is limited due to the fact that waste disposed in those facilities releases not only cationic nuclides (Cs-137, Sr-90, Co-60) but also anionic ones (Se-79, Tc-99, I-129), whose retention by clay minerals is reduced due to electrostatic repulsion.…”