Adsorption of cationic dye on activated carbon from hydrolyzed Dipterocarpus alatus leaves: Waste from biodiesel production

Abstract

In this study, hydrolyzed Dipterocarpus alatus leaves (HDL), waste from biodiesel production, were used as precursor to prepare activated carbon. The HDL residue was treated with 30 wt% ZnCl2 (raw material:ZnCl2 solution = 1:2 by weight) for 1 to 24 h followed by carbonization at 500 °C for 1 h in N2 atmosphere. The highest specific surface area of 497 m2 g1 was obtained with 12 h treatment. The physicochemical properties of the optimum carbon were investigated by thermogravimetric analysis (TGA), Fourier transform infrared (FTIR) spectroscopy, proximate analysis, bulk density and pH, and the potential of the activated carbon for methylene blue (MB) adsorption was tested under various contact times and initial dye concentrations. Adsorption equilibrium was reached within 50 min. The adsorption of MB onto the HDL-derived activated carbon followed pseudo-second order kinetics through chemisorption, with intra-particle diffusion as the significant controlling step. The Langmuir isotherm provided a better fit of the adsorption equilibrium than the Freundlich isotherm, with a maximum monolayer adsorption capacity of 338.86 mg g1. The activated carbon prepared from Dipterocarpus alatus leaves residue exhibited good adsorption uptake for MB and therefore presents an attractive and effective adsorbent for cationic dyes.

Keywords

• activated carbon
• dipterocarpus alatus leaves
• chemical activation
• adsorption
• cationic dye