Interpretation of diclofenac adsorption onto ZnFe2O4/chitosan magnetic composite via BET modified model by using statistical physics formalism

The goal of this work is the study of the adsorption of Diclofenac (DCF) on a magnetic composite made by metal oxide dispersion onto chitosan (ZnFe2O4/CMC). The adsorption isotherms at four temperatures (298, 308,318 and 328 K) and pH = 3 are interpreted in the light of an adsorption model derived from the statistical physics formalism, which includes the calculation of physicochemical parameters with defined physical meaning. Specifically, the adsorption process is interpreted in light of the number of DCF molecules adsorbed per site (n), which increases with temperature, and the density of receptor sites (NM), which shows a similar trend. The values of the calculated adsorption energy (ΔE1 and ΔE2) confirmed that the interaction between the DCF molecules and ZnFe2O4/CMC takes place via physical forces. Overall, the hydrogen bonds are identified as the main bonding interactions of DCF molecules on the ZnFe2O4/CMC surface. Interestingly, thermodynamic potential functions are determined for a complete adsorption characterization, which included also the adsorption energy distribution (AED) determination of DCF adsorption onto the ZnFe2O4/CMC.