Kinetics–thermodynamics integration for improved understanding of adsorption mechanisms: A critical perspective

Adsorbates adsorption on adsorbent is a complex process and this study analyzed critically adsorption mechanisms using theoretical perspectives. Although considerable advances have been made in understanding the isolated role played by various system properties, theoretical developments have not been rigorous and they lag behind experimental and conceptual developments. Some of the experimental difficulties and theoretical complexities that are responsible for the slow development of a unifying adsorption model covering a range of adsorbates-adsorbent combinations have been analyzed critically from adsorption principle, experimental algorithms for obtaining adsorption and adsorption kinetics parameters as well as the adsorption parameters analysis using different adsorption, kinetic and thermodynamic models. the sudden decrease of adsorption densities of pH, temperature and adsorbent dosage after successive increase as been explained to be as a result of the effect of H+ and/or OH- ions, intermolecular forces and/or weakening of the attractive forces due to excessive heat energy at higher temperature.  The nexus between existing adsorption models such as Stern-Grahame and Equilibrium Constant (K_c), Henry and Arrhenius laws, Langmuir isotherm and thermodynamic variables (〖lnK〗_eq 〖,∆G〗^o, 〖∆H〗^o and 〖∆S〗^o), Langmuir and Stern-Grahame’s isotherm equations and pseudo first and second kinetic models were analyzed. The major individual contributions to the overall energy of adsorption have been identified and discussed for effective analysis of adsorption mechanisms and systems.