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 (<i>R</i><sup>2</sup> > 0.98). The kinetic and thermo­dynamic parameters like diffusion coefficient (<i>D</i><sub>o</sub>), energy of activation (<i>E</i><sub>a</sub>), enthalpy of activation (Δ<i>H</i>*), entropy of activation (Δ<i>S</i>*), and free energy of activation (Δ<i>G</i>*) 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 (Δ<i>H</i>*) indicate the endothermic nature of the ion exchange process. The ion exchange follows an associative mechanism as indicated by Δ<i>S</i>* < −130 J mol<sup>–1</sup> K<sup>–1</sup>. The comparatively fast kinetics of ion exchange by the nanocomposite depicts its applicability for environmental remediation.