Biosorption of Crystal violet, Congo red and Methyl orange on Nephelium lappaceum stem-derived activated carbon and its composite with chitosan

Abstract

Activated carbon was prepared using Nephelium lappaceum stem as the pre-cursor biomass. A bio-composite with chitosan and the activated carbon (NLAC) was synthesized. The activated carbon and the bio-composite were tested for the adsorptive removal of three dyes, namely Crystal violet (CV), Congo red (CR) and Methyl orange (MO), from their aqueous solutions. The characterization of each adsorbent revealed higher value for surface area, satisfactory mechanical strength, higher crystallinity as well as superior porosity. The batch adsorption equilibrium data were best fitted to Langmuir isotherm model. A maximum adsorption capacity of 212.1 mg/g was seen for CV using NLAC. For CR and MO, the maximum adsorption capacitity values were 182.57 mg/g and 64.21 mg/g respectively with CHS-NLAC composite. Electrostatic interaction was the dominant mechanism in the adsorption of the dyes and the rate controlling steps in the adsorption were reasoned in the kinetic studies.