Isotherm, kinetics and thermodynamics of methylene blue dye adsorption onto CO2-activated pyrolysis tyre powder

Abstract

This work was aimed at evaluating the adsorption properties of methylene blue dye by CO 2 -activated pyrolysis tyre powder carbons. The activated carbons were prepared under the flow of CO 2 at temperatures between 900°C and 1,000°C for durations of 2–8 h. Consequently, the activated carbons were characterized for textural properties, pH PZC , surface functional groups, and surface morphology. Batch adsorption was conducted by varying the concentrations of methylene blue and contact times, from which the experimental data were fitted into isotherm and kinetic models. Results show that CO 2 activation at 1,000°C for 2 h yields a 57.2% activated carbon with a 243 m ² /g specific surface area and a maximum methylene blue adsorption capacity of 132 mg/g. The Langmuir and Redlich– Peterson models appeared to fit the equilibrium data well. The rate of adsorption data obeyed the pseudo-second-order kinetic model, while the rate-limiting step in the adsorption of methylene blue is probably film diffusion. The adsorption is endothermic and spontaneous with increasing temperature. Activated carbon prepared from pyrolysis tyre powder by CO 2 activation is a promising candidate to abate dye wastewater pollution.