Adsorption of brilliant green dye from aqueous solution onto chemically modified areca nut husk

Abstract

Areca nut husk, an inexpensive, easily available agricultural by-product modified with sodium hydroxide has been applied to remove Brilliant green (BG) dye from aqueous solution. Surface characteristics and the elemental composition of areca nut husks were examined using Scanning electron microscope (SEM) and Energy dispersive X-ray (EDX). The chemical treatment changes the surface morphology of the areca nut husk. The alkali treatment removes natural wax, resins and lignin from husks and thus it added extra active surface area and pores for better adsorption. The Fourier-transform infrared (FTIR) spectroscopy indicated that the presence of functional groups (-OH), (-C=O), (-C=C), (-COOH). Experiments were performed in batch adsorption procedure. The optimum removal of 97% BG dye was obtained at pH 7.0, adsorbent dosage 10 g/L, initial concentration 100 mg/L, agitation speed 200 rpm and temperature 298 K. Adsorption data fit better to Langmuir model in comparison with Freundlich, Temkin and Dubinin-Radushkevich isotherm model. The maximum adsorption capacity of 18.21 mg/g was obtained. Kinetic date followed pseudo-second-order rate kinetic better than pseudo-first-order model. The thermodynamic parameters ΔH0 = 12.522 kJ/mol and ΔS0 = 0.044 J/mol indicate endothermic and spontaneous adsorption process. Taking considerations of all experimental results and model analysis, it is concluded that sodium hydroxide treated areca nut husk is a good, low cost and effective biosorbent for the removal of BG dye from aqueous solution.