Kinetics and Thermodynamics of Alkaline Earth and Heavy Metal Ion Exchange under Particle Diffusion Controlled Phenomenon Using Polyaniline-Sn(IV)iodophosphate Nanocomposite

The poly­aniline-Sn­(IV)­iodo­phosphate nanocomposite (PANI-SnIP) has been synthesized, and its various kinetic and thermo­dynamic parameters for alkaline earth and heavy metal ion exchange were evaluated. Above 0.03 M solution of metal ions, the particle diffusion controlled phenomenon is found to be predominant (R² > 0.98). The kinetic and thermo­dynamic parameters like diffusion coefficient (D_o), energy of activation (E_a), enthalpy of activation (ΔH*), entropy of activation (ΔS*), and free energy of activation (ΔG*) were evaluated under particle diffusion controlled phenomenon. The fractional attainment of equilibrium was faster at an elevated temperature, and the rate of exchange is predominated by Hg­(II) ions in the case of multi­component systems. The positive values of the standard enthalpy change (ΔH*) indicate the endothermic nature of the ion exchange process. The ion exchange follows an associative mechanism as indicated by ΔS* < −130 J mol^–1 K^–1. The comparatively fast kinetics of ion exchange by the nanocomposite depicts its applicability for environmental remediation.