Research on the Reaction Mechanism between Struvite Crystals and Cesium Ions

As a strategic element, efficient extraction technology for cesium holds significant importance. This study investigates the reaction process between Cs+ and struvite (MgNH4PO4·6H2O). Fitting reveals that this reaction follows a pseudo-second-order kinetic model, while the thermodynamic equilibrium process adheres to the Temkin isothermal model (R2 = 0.990). The thermodynamic parameter ΔG° < 0 indicates a spontaneous entropy-increasing reaction process. By combining the characterization of intermediate products M1–M4 and reaction evolution analysis, the reaction mechanism between struvite and Cs+ is intuitively demonstrated. The reaction mechanism is proposed as follows: macroscopically, it manifests as an ion exchange process with chemical adsorption characteristics; microscopically, it involves dissolution and recrystallization. This finding provides theoretical support for process design in Cs+ adsorption by struvite.