Adsorption kinetic, thermodynamic and desorption studies of C.I. Reactive Black 5 on a novel photoassisted Fenton catalyst

An activated alumina-supported iron oxide-composite (denoted as FeAA-25) was utilized successfully as a catalyst for the heterogeneous photoassisted Fenton degradation of the azo dye C.I. Reactive Black 5 (RB5) at a pH of 7.0 in our previous study. In this work, the adsorption and desorption behaviours of RB5 on FeAA-25 were studied. Adsorption thermodynamics of RB5 on FeAA-25 were studied at 288, 303 and 318 K and the thermodynamic parameters, such as equilibrium constant (K0)(K0), standard free energy changes (ΔG0)(ΔG0), standard enthalpy change (ΔH0)(ΔH0) and standard entropy change (ΔS0)(ΔS0) have been obtained. A pseudo-second-order rate model was employed to describe the kinetic adsorption processes. Additionally, desorption studies revealed that RB5 can be easily removed from FeAA-25 by altering the pH of the solution using NaOH. The mechanism of the RB5 adsorption onto FeAA-25 at neutral pH 7.0 will be established through this study.