Adsorption of reactive dye on palm-oil industry waste: Equilibrium, kinetic and thermodynamic studies

The adsorption of C.I. Reactive Red 120 (RR120) on activated oil palm ash (AOPA) was studied in a batch system. The adsorption studies were carried out at different initial dye concentratiosn (50–600 mg L−1), solution pH (2–12) and temperature (30, 40 and 50°C). The experimental data were analyzed by the Langmuir and Freundlich isotherms. The Freundlich model agreed very well with the experimental data. The maximum monolayer adsorption capacities obtained from the Langmuir model was 200.12, 334.78 and 376.41 mg g−1 at 30, 40 and 50°C, respectively. The pseudo-first-order and pseudo-second-order were used to describe the kinetics data The adsorption kinetics of RR120 onto AOPA was described by the pseudo-second-order kinetic equation. The activation energy, change of Gibbs free energy, enthalpy and entropy of adsorption were also evaluated for the adsorption of RR120 onto AOPA.