Decolorization And COD Reduction Of Methylene Blue Dye Wastewater Through Adsorption Using Raw And Modified Bagasse
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Date
2011-05
Authors
Low, Ling Wei
Journal Title
Journal ISSN
Volume Title
Publisher
Universiti Sains Malaysia
Abstract
In the present study, batch and column adsorption systems were applied to
study the adsorption of methylene blue (MB) from the dye aqueous solution onto a
lignocellulosic material ―bagasse. The bagasse was modified with various
carboxylic acids, namely citric acid (CA), oxalic acid (OA), and tartaric acid (TA). In
order to improve chemical oxygen demand (COD) reduction, pretreatment of the
bagasse with thorough washing using boiling distilled water was performed instead
of conventional washing with distilled water at room temperature only. The effects of
pH, adsorbent dosage, shaking speed, contact time, and temperature on
decolorization and COD reduction were studied and optimized using response
surface methodology (RSM) ―central composite design (CCD). The results show
that the TA modified bagasse was more effective than raw bagasse (RB), CA
modified bagasse, and OA modified bagasse in decolorization and COD reduction of
MB dye from the aqueous solution. Maximum decolorization (99.05 %) and COD
reduction (98.45 %) for TA modified bagasse were achieved at 0.78 g adsorbent
dosage, pH 9.4, shaking speed of 120 rpm, 34 min contact time, and 49 oC. The
adsorption kinetics were analyzed using four kinetic equations, namely, the
pseudo-first order, pseudo-second order, the external diffusion model, and the
intraparticle diffusion model to examine the adsorption mechanisms and potential
rate controlling steps. TA modified bagasse showed good correlations with
pseudo-second order kinetic model. Adsorption isotherm data were correlated with
Langmuir, Freundlich, Temkin, Dubinin-Radushkevich (DR) isotherm models. The
adsorption process followed the Langmuir isotherm as well as Freundlich isotherm.
The enthalpy change (ΔHo) of 13.178 kJ/mol showed that adsorption using TA
modified bagasse was endothermic in nature. The Gibbs free energy change (ΔGo) of
-13.714 kJ/mol to -16.799 kJ/mol showed the feasibility of the process and the
spontaneous nature of adsorption with a high preference of MB onto TA modified
bagasse.
Description
Keywords
The adsorption of methylene blue from the dye aqueous solution , onto a lignocellulosic material bagasse