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 318K and the thermodynamic parameters, such as equilibrium constant (K0), standard free energy changes (ΔG0), standard enthalpy change (ΔH0) and standard entropy change (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.