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Description
Ion‑exchange (IX) technologies are widely used for purifying aqueous solutions by enabling a reversible, stoichiometric exchange of ions between an electrolyte and a solid sorbent. Among the various materials available, aluminosilicate zeolites—particularly clinoptilolite—exhibit strong intrinsic selectivity for cesium and strontium, making them highly relevant to nuclear effluent treatment. However, traditional fixed‑bed systems often suffer from slow uptake rates and significant mass‑transfer limitations, motivating intensified processing approaches capable of improving sorbent utilisation and reducing contact times.
This study evaluates the kinetic performance of a novel intensified IX system by comparing stationary and agitated modes of operation using chabazite‑based aluminosilicate pellets. Batch experiments exposed pellets to 25–50 ppm cesium and strontium solutions at a 20:1 liquid‑to‑solid ratio, with concentration decay measured via Inductively Coupled Plasma Mass Spectrometry (ICP‑MS). Kinetic modelling showed good agreement with Pseudo‑First‑Order (PFO) behaviour and strong agreement with Pseudo‑Second‑Order (PSO) kinetics, indicating a chemisorption controlled mechanism. NOVA gas adsorption analysis revealed a specific surface area above 300$m^2$/g, which decreased following IX, consistent with occupation of microporous domains.
These findings provide new insights into pellet structure, hydrodynamics and sorption kinetics within intensified IX systems. The results highlight the potential for composite or mechanically reinforced pellets to enhance selectivity, improve operational robustness and lower lifecycle cost in nuclear waste remediation. These outcomes support future development of intensified IX processes, particularly those incorporating oscillatory or agitated‑flow conditions that address the kinetic limitations of conventional fixed‑bed systems.
References:
[1] Kivan, Harbottle, Hunter et al 2025. Intensified co-precipitation and ion exchange using an agitated tubular reactor (ATR) for enhanced removal of ($\text{Cs}^{1+}$) and ($\text{Sr}^{2+}$) ions. Chemical Engineering \& Processing: Process Intensification 207-110077.
[2] Yaghy et al 2023. Opportunities for intensification technologies in nuclear effluent treatment: a review of precipitators, absorbers and separators. Chemical Engineering & Processing: Process Intensification 191-109441.