Enhanced cadmium removal by a magnetic potassium ferrocyanide framework: Performance and mechanism study

Polluted environments often contain large amounts of toxic metals, such as cadmium, which pose a major threat to ecosystems and public health. Contamination by cadmium and its compounds is often observed in areas surrounding zinc mining sites and electroplating factories, and the control of cadmium pollution is essential for environmental safety and health. In this study, a highly efficient and straightforward separation strategy for K₄Fe(CN)₆@Fe₃O₄ nanocomposites is successfully developed to capture the Cd ions in the water environment. Batch adsorption experiments revealed that K₄Fe(CN)₆@Fe₃O₄ exhibited a high cadmium removal rate (greater than 98 %) at a pH level of 6.0 and solid-liquid ratio of 1.0 g/L at room temperature (298 K). Kinetic analysis revealed that the adsorption process followed a pseudo-second-order model and cadmium was rapidly removed in the first 10 min, with chemisorption dominating the capture of Cd²⁺ by K₄Fe(CN)₆@Fe₃O₄. Adsorption isotherms revealed a heterogeneous adsorption behavior, with a maximum adsorption capacity of 40.78 mg/g. The intrinsic adsorption of Cd²⁺ by K₄Fe(CN)₆@Fe₃O₄ occurring primarily through electrostatic interaction and ion exchange. In addition, K₄Fe(CN)₆@Fe₃O₄ exhibited an excellent regeneration capacity. Therefore, integrating Fe₃O₄ into the metal cyanide not only provided the composite material with excellent chemical stability and selective adsorption sites for Cd²⁺, but also facilitated subsequent sorbent collection and recovery. Overall, this study presents a simple and feasible approach for integrating Fe₃O₄ into potassium ferrocyanide frameworks for efficient cadmium removal from contaminated water.