Equilibrium and kinetic study of arsenic sorption by water-insoluble
nanocomposite resin of poly[N-(4-vinylbenzyl)-N-methyl-
Bruno F. Urbano
, Bernabé L. Rivas
, Francisco Martinez
, Spiro D. Alexandratos
Departamento de Polímeros, Facultad de Ciencias Químicas, Universidad de Concepción, Casilla 160-C, Concepción, Chile
Departamento de Ciencias de los Materiales, Facultad de Ciencias Físicas y Matemáticas, Universidad de Chile, Casilla 2777, Santiago, Chile
Department of Chemistry, Hunter College of the City University of New York, 695 Park Avenue, New York, NY 10065, United States
Received 17 December 2011
Received in revised form 23 March 2012
Accepted 23 March 2012
Available online 11 April 2012
This research presents the kinetic and equilibrium performance of arsenic sorption by a novel polymer-
clay nanocomposite ion exchange resin. The monomer N-(4-vinylbenzyl)-N-methyl-
previously synthesised and subsequently polymerised via radical initiation in the presence of crosslink-
ing reagent N,N-methylene-bis-acrylamide and organic-modiﬁed montmorillonite. The sorption of
arsenic(V) was studied as a function of time, initial concentration and pH. Experiments as a function of
pH revealed that arsenic sorption was favoured in the pH range from 3 to 6. The experimental data were
ﬁtted to kinetic and diffusion models, such as pseudo-ﬁrst order, pseudo-second order, Elovich, and the
intra-particle diffusion model. The pseudo-second order model presented the best correlation with the
experimental data. The model indicated that high percentages of retention could be achieved in a short
time (>90%, 1 h of contact) at pH 6 when the initial arsenic concentration was between 5 and 50 mg/L.
Intra-particle diffusion and the Boyd relationship showed that arsenic sorption was controlled by the ﬁlm
diffusion mechanism. The Langmuir, Freundlich, and Dubinin–Radushkevitch isotherms were ﬁtted to
experimental data, and the Langmuir isotherm presented the best ﬁt. Thermodynamic parameters
S°) showed that the arsenic sorption process was a spontaneous process, endothermic,
and produced an increase in entropy.
Ó 2012 Elsevier B.V. All rights reserved.
Water plays important roles in human activities, the natural
environment, and social development. One of the most important
problems in water use is arsenic pollution due to its high toxicity.
Arsenic pollution concerns the entire world, particularly in coun-
tries where water naturally has high arsenic concentrations, such
as Bangladesh, India, China, Chile, Argentina, and Mexico . The
World Health Organization (WHO) and the Environmental Protec-
tion Agency (EPA) have strictly reduced the maximum contami-
nant level recommended from 50
g/L to 10
g/L to minimise the
risk to humans . Therefore, it is necessary to research new sorp-
tion procedures able to remove arsenic selectively.
Arsenic exists in water primarily as arsenate, As(V), and arse-
nite, As(III), in the forms of arsenic acid (H
) and arsenous acid
), respectively. The arsenic species are pH dependent and
the most dominant species in natural waters is the monovalent
Þ. Several technologies exist for arsenic removal,
such as coagulation-precipitation, ﬁltration, and adsorption ,
with adsorption being the most extensively studied because it
has better performance, easier operation, lower cost and the possi-
bility to recycle [4–7].
Ion exchange resins containing N-methyl-
are widely used for selective boron removal [8,9]. This ligand has
also been studied for oxyanion uptake of molybdate, vanadate,
chromate, and arsenate [10,11]. Arsenic uptake presented the most
promising results, and it has been demonstrated that ion exchange
resins containing NMDG ligands improve the retention of arsenate
at pH 4–6. Additionally, the NMDG ligand showed a
high selectivity toward arsenate ions, even in the presence of a
high concentration of sulphate [12,13].
The development of new materials for potential application in
ion exchange has presented important advances. These have in-
cluded solvent impregnated resins and metal-loaded ion exchange
resins, which consist of hybrid materials to obtain new materials
with improved properties [14–17]. Our group has reported the
synthesis of polymer-clay nanocomposites of monomers able to
interact with metal ions and loaded with organic-modiﬁed mont-
morillonite. The nanocomposites presented enhanced mechanical
1385-8947/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved.
Corresponding author. Fax: +56 41 2245974.
E-mail address: firstname.lastname@example.org (B.L. Rivas).
Chemical Engineering Journal 193–194 (2012) 21–30
Contents lists available at SciVerse ScienceDirect
Chemical Engineering Journal
journal homepage: www.elsevier.com/locate/cej