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Chemical Engineering Journal 156 (2010) 2–10
Contents lists available at ScienceDirect
Chemical Engineering Journal
journal homepage: www.elsevier.com/locate/cej
Review
Insights into the modeling of adsorption isotherm systems
K.Y. Foo, B.H. Hameed ∗
School of Chemical Engineering, Engineering Campus, Universiti Sains Malaysia, 14300 Nibong Tebal, Penang, Malaysia
article info
Article history:
Received 2 March 2009
Received in revised form 6 September 2009
Accepted 7 September 2009
Keywords:
Adsorption
Isotherm
Linear
Nonlinear
Error function
abstract
Concern about environmental protection has increased over the years from a global viewpoint. To date,
the prevalence of adsorption separation in the environmental chemistry remains an aesthetic attention
and consideration abroad the nations, owning to its low initial cost, simplicity of design, ease of oper-
ation, insensitivity to toxic substances and complete removal of pollutants even from dilute solutions.
With the renaissance of isotherms modeling, there has been a steadily growing interest in this research
field. Confirming the assertion, this paper presents a state of art review of adsorption isotherms mod-
eling, its fundamental characteristics and mathematical derivations. Moreover, the key advance of the
error functions, its utilization principles together with the comparisons of linearized and non-linearized
isotherm models have been highlighted and discussed. Conclusively, the expanding of the nonlinear
isotherms represents a potentially viable and powerful tool, leading to the superior improvement in the
area of adsorption science.
© 2009 Elsevier B.V. All rights reserved.
1. Introduction
Over the past several decades, the exponential population
and social civilization expansion, change affluent lifestyles and
resources use, and continuing progress of the industrial and tech-
nologies has been accompanied by a sharp modernization and
metropolitan growth [1]. With the rising awareness of the occur-
rences of industrial activities which has intensified numerous
deteriorations on several ecosystems and seriously threatens the
human health and environment, the enforcement of stringent rules
and regulations concerning the emission of contaminants from
industrial waste streams by various regulatory agencies has been
promulgated [2].
Simultaneously, a developing research by the invention
of a wide range of treatment technologies (precipitation,
coagulation–flocculation, sedimentation, flotation, filtration, mem-
brane processes, electrochemical techniques, biological process,
chemical reactions, adsorption and ion exchange) with varying lev-
els of successes has accelerated a dramatic progress in the scientific
community [3–13]. Of major interest, adsorption process, a sur-
face phenomenon by which a multi-component fluid (gas or liquid)
mixture is attracted to the surface of a solid adsorbent and forms
attachments via physical or chemical bonds, is recognized as the
most efficient, promising and widely used fundamental approach in
wastewater treatment processes [14], mainly hinges on its simplic-
∗Corresponding author. Tel.: +6045996422; fax: +60 45941013.
E-mail address: chbassim@eng.usm.my (B.H. Hameed).
ity, economically viable, technically feasible and socially acceptable
[15].
A notable trend in the development of activated carbon (AC),
an adsorbent with its large porous surface area, controllable pore
structure, thermo-stability and low acid/base reactivity has been
witnesses [16], in terms its versatility for removal of a broad
type of organic and inorganic pollutants dissolved in aqueous
media, even from gaseous environment [17]. Despite its prolific
use in adsorption processes, the biggest barrier of its application
by the industries is the cost-prohibitive adsorbent and difficul-
ties associated with regeneration [18]. Realizing the complication,
a growing exploitation to evaluate the feasibility and suitability
of natural, renewable and low-cost materials (bamboo dust, peat,
chitosan, lignite, fungi, moss, bark husk, chitin, coir pith, maize
cob, pinewood sawdust, rice husk, sugar cane bagasse, tea leaves,
and sago waste) as alternative adsorbents in water pollution con-
trol, remediation and decontamination processes has been exerted
[19,20].
In the endeavor to explore novel adsorbents in accessing an ideal
adsorption system, it is essential to establish the most appropri-
ate adsorption equilibrium correlation [21], which is indispensable
for reliable prediction of adsorption parameters and quantitative
comparison of adsorbent behavior for different adsorbent systems
(or for varied experimental conditions) [22,23]. In the perspec-
tive, equilibrium relationships, generally known as adsorption
isotherms, describe how pollutants interact with the adsorbent
materials, and thus are critical for optimization of the adsorption
mechanism pathways, expression of the surface properties and
capacities of adsorbents, and effective design of the adsorption
systems [24,25].
1385-8947/$ – see front matter © 2009 Elsevier B.V. All rights reserved.
doi:10.1016/j.cej.2009.09.013
