Innovative potassium hexacyanoferrate intercalated into layered double hydroxide adsorbent for efficient cesium removal from seawater

Effective radioactive wastewater treatment technology is essential to ensure the sustainable development of nuclear energy. Here, the potassium ferrocyanide (HCF) intercalating with layered double hydroxide (LDH) (HCF@LDH) was successfully synthesized by coprecipitation method for selective cesium (Cs) removal from seawater. Characteristics of the adsorbent, and adsorption performance under different environmental conditions including Cs⁺ ion selectivity, and underlying adsorption mechanism were systematically investigated. The experimental results demonstrated that the adsorption capacity of HCF@LDH was 52.08 mg/g and it effectively removed 100 % of Cs⁺ from up to 200 mg/L Cs solution within 1 h under an optimal pH of 6.0–10.0. Moreover, the adsorbent displayed high selectivity towards Cs⁺ even in seawater and more than 90 % of Cs⁺ was removed from seawater and the highest cesium removal capacity from seawater was 44.64 mg/g. Both the Langmuir isotherm model (R² = 0.997) and the pseudo-second-order kinetic model (R² = 0.999) provided a good fit for the adsorption data signifying the adsorption process is homogeneous and formed monolayer through chemisorption. Furthermore, the reusability analysis exhibited this adsorbent was recycled and reused for at least 5 cycles without losing its original adsorption performance. The physicochemical analysis of the HCF@LDH proved that K₄Fe (CN)₆ successfully intercalated onto LDH and cation exchange between K⁺ and Cs⁺ played an important role in effective Cs adsorption. More specifically, the interstitial spaces of the hexacyanoferrate crystals facilitate the cation exchange process. The findings of this study demonstrate that HCF@LDH is a unique, highly effective, and selective adsorbent for Cs⁺ from complex seawater.