Evaluation of methylene blue dye and phenol removal onto modified CO2-activated pyrolysis tyre powder

Abstract

The present work was aimed at evaluating the adsorption properties of methylene blue dye and phenol by activated carbons derived from pyrolysis tyre powder. The activation was carried out under CO2 at 1000 °C for 2 h. The activated carbon (AC10-2) was demineralized using H2F2 (AC-Demi), followed by oxidation with nitric acid (AC-Oxi). Consequently, the activated carbons were characterized for textural properties, pHPZC, surface functional groups and surface morphology. Batch adsorption studies were conducted by varying the initial concentration of model pollutants, contact time and temperature, from which the experimental data were fitted into isotherm, kinetics and thermodynamics models. Upon oxidation, AC-Oxi shows an increase of surface area to 352 m2/g as compared to AC10-2 (237 m2/g). Result also shows that AC-Oxi exhibits a higher methylene blue adsorption of 107 mg/g, while AC10-2 shows a higher phenol adsorption of 48 mg/g. The equilibrium data of methylene blue adsorption fitted well with Langmuir and Redlich-Peterson models, while that of phenol adsorption obeyed Freundlich isotherm. The kinetics data of both model pollutants could be described by the pseudo-second-order model, where the rate-limiting step could be dominated by pore diffusion. The adsorption of methylene blue is endothermic and spontaneous at high temperature, while that of phenol adsorption is exothermic and spontaneous at low temperature.