Khor, Siok Moi
(2013)
Activated Rice Husk-Based Adsorbents
For Chlorophenol Removal And Their
Bioregeneration.
PhD thesis, Universiti Sains Malaysia.
Abstract
The objectives of this study are to develop rice husk-based adsorbents
activated with different activating agents, namely potassium hydroxide (KRH), nitric
acid and methanol (ARH), and ethylenediamine (MRH), and compare their
adsorption capacities and bioregeneration efficiencies to remove 4-chlorophenol (4-
CP) and 2,4-dichlorophenol (2,4-DCP) from the aqueous solutions with the
commercially available powdered activated carbon (PAC).
From the adsorption equilibrium studies of 4-CP and 2,4-DCP, the trend of
maximum adsorption capacity, qm, among the adsorbents followed KRH > PAC >
ARH > MRH and in agreement with the trend of BET surface areas. The equilibrium
adsorption data of KRH and PAC were best described by the Langmuir model (R2 >
0.98) while the Freundlich model was suitable to describe the equilibrium adsorption
data for MRH and ARH (R2 > 0.99). These observations were confirmed by the
values of heterogeneity constant, μ, obtained from the Redlich-Peterson model. It
could be concluded that the adsorbent surfaces of MRH and ARH were
heterogeneous, while those of the KRH and PAC were homogenous. For the
temperature-dependent Temkin and Dubinin-Radushkevich isotherm models, the
Dubinin-Radushkevich model was better fitted to the experimental data than the
Temkin model.
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