Chemical Engineering Journal 160 (2010) 157–163

Contents lists available at ScienceDirect

Chemical Engineering Journal

Evaluation of Cu2+, Co2+ and Ni2+ ions removal from aqueous solution using a
novel chitosan/clinoptilolite composite: Kinetics and isotherms
Maria Valentina Dinu, Ecaterina Stela Dragan ∗
Department of Functional Polymers, “Petru Poni” Institute of Macromolecular Chemistry, Aleea Grigore Ghica Voda 41A, 700487 Iasi, Romania

a r t i c l e i n f o a b s t r a c t

Article history: A novel chitosan/clinoptilolite composite, as beads with an average size of 800 µm in diameter, in dry
Received 10 October 2009 state, was used for comparative studies on the removal of toxic metal ions like: Cu 2+, Co2+ and Ni2+
Received in revised form 8 March 2010
from aqueous solutions. The effects of the initial pH value of the solution, contact time, the initial metal
Accepted 16 March 2010
ion concentration and temperature on the adsorption capacity of the composite were investigated. The
kinetics data were analysed by pseudo-first order, pseudo-second order, and intra-particle diffusion
Keywords:
equations. The adsorption kinetics were well described by the pseudo-second order equation, and the
Adsorption
adsorption isotherms were better fitted by the Langmuir equation. The maximum theoretical adsorption
Chitosan
Clinoptilolite capacities of the chitosan/clinoptilolite composite for Cu2+, Co2+ and Ni2+ were found to be 11.32, 7.94
Composite and 4.209 mmol/g, respectively. The negative values of Gibbs free energy of adsorption (6Ga◦ds ) indicated
Heavy metals the spontaneity of the adsorption of all metal ions on the novel composite. Desorption of the metal ions
from the composite was achieved by using 0.1 M HCl in about 20 min.
© 2010 Elsevier B.V. All rights reserved.

1. Introduction charge being balanced by metal cations, like Na+, K+, Ca2+ and Mg2+
[7].
In recent years, special attention has been given to the envi- Chitosan (CS) and its derivatives have been also extensively
ronmental contamination with heavy metals because of their high investigated as biosorbent for removal of heavy metals [9–11]. To
toxicity and non-biodegradability. Conventional methods that have improve the mechanical properties, adsorption capacity, or even to
been used to remove heavy metal ions from various industrial efflu- prevent dissolution in acidic medium of the CS, numerous studies
ents usually include chemical precipitation, membrane separation, have been devoted to the chemical modification of the CS surface by
ion exchange, evaporation, and electrolysis, etc. and are often costly homogeneous or heterogeneous cross-linking with di- or polyfunc-
or ineffective, especially in removing heavy metal ions from dilute tional agents, such as sodium tripolyphosphate, glutaraldehyde,
solutions. ethyleneglycol diglycidyl ether and epichlorhydrin [11–13]. On the
Among the conventional techniques commonly used in the other hand, CS-based composite materials have also been reported
removal of heavy metals from wastewaters the adsorption process to exhibit enhanced mechanical, thermal or adsorption properties
is mainly preferred especially when the enrichment of trace metal comparative with any of its components used alone. Novel CS-
amounts or a high selectivity for a certain metal are required [1–4]. based composite materials with enhanced adsorption properties
However, the benefits of this technique are offset by the rising cost for removal of heavy metal ions like Cu2+, As3+ and As5+ have been
of adsorbents like activated carbon and synthetic ion exchangers. designed by loading attapulgite into chitosan-g-poly(acrylic acid)
The hunt for a cheap and widely available adsorbent has motivated polymeric network [14] or by coating ceramic alumina with chi-
researchers to focus on naturally available adsorbents like natural tosan [15]. Other CS-based composites were obtained by coating
zeolites [5–8]. Clinoptilolite (CPL), one of the most common natural with CS the iron hydroxide [16], or perlite, an inorganic porous
zeolites, is a hydrated alumina–silicate member of the heulandite aluminosilicate [17].
group, occurring in the zeolitic volcanic tuffs, being widespread In our recent studies, we reported on the synthesis of some novel
in many countries in the world. CPL is characterized by infinite CS/CPL composites by embedding zeolite microparticles in a matrix
three-dimensional frameworks of [AlO4]5− and [SiO4]4− tetrahedra of cross-linked chitosan [18,19]. A comparative evaluation of the
linked to each other by sharing all of the oxygens, and the negative adsorption capacities of the CS/CPL composite containing 20 wt.% of
zeolite against three environmentally problematic divalent metal
ions, namely, Cu2+, Co2+ and Ni2+, from aqueous solutions, was
∗ Corresponding author. Tel.: +40 232 217454; fax: +40 232 211299. developed in this paper. The factors influencing the adsorption
E-mail address: sdragan@icmpp.ro (E.S. Dragan). capacity of the composite such as the initial pH value of the metal

1385-8947/$ – see front matter © 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.cej.2010.03.029
158 M.V. Dinu, E.S. Dragan / Chemical Engineering Journal 160 (2010) 157–163

ions solutions, contact time, the initial concentration of metal ions effect of initial concentrations of the metal ion on the adsorption
solutions and temperature were investigated. In order to examine rate and capacity on the CS4CPL1 composite, the initial concen-
the controlling mechanism of the adsorption process, the kinet- tration of the Cu2+, Co2+ and Ni2+ metal ion solutions was varied
ics, adsorption isotherms and thermodynamics parameters were between 0.0025 and 0.1 mol/L in the adsorption medium at pH 5.0.
evaluated. The CS4CPL1 composite was filtered off, and the residual concen-
tration of the metal cation remained in the filtrate was measured
2. Materials and methods by the UV–vis spectroscopy at 510 nm for Co2+, 720 nm for Ni2+ and
775 nm for Cu2+ (these were the maximum absorption wavelengths
2.1. Materials of CoCl·2 6H2O, NiCl·2 6H2O and CuSO4· 5H2O). UV–vis spectroscopy
was performed on a UV–vis SPECORD M42 Carl Zeiss Jena, Germany.
CS as powder was purchased from Fluka, ash content less than The amount of metal ion bound on the CS4CPL1 composite was
1%, and was used without further purification. The viscometric calculated with Eq. (1):
average molar mass and the deacetylation degree of CS used in
(S0 − S)V
this study were 334 kDa and 82.4%, respectively. These values were Adsorption capacity = , mmol/g (1)
W × AM × 1000
estimated according to the methods presented elsewhere [19]. The
natural CPL sample used in the preparation of the composite comes where S0 and S are the concentrations of the metal ion in aqueous
from volcanic tuffs containing 60–70% CPL, cropped out in Măcicaş solution (mg/L) before and after the interaction with dried CS4CPL1
area (Cluj County, Romania), and has the following elemental composite, respectively, V is the volume of the aqueous phase (L),
composition: (NaKCa0.5 )5.4 (Al5.4 Si30.6 O72 )·20H2 O (Si/Al = 5.7) [7]. W is the amount of the dried CS4CPL1 composite (g) and AM is the
The zeolitic volcanic tuff was used as collected. CuSO4 ·5H2 O, atomic mass of the metal ion.
CoCl2·6H2O, NiCl2· 6H2O (all from Aldrich) were used as metal ion For each adsorption experiments, the average of three replicates
source for the adsorption experiments. All the reagents were of ana- was reported.
lytical grade or highest purity available, and used without further
purification. 2.4. Desorption and regeneration studies

2.2. Preparation and characterization of CS/CPL composite Desorption studies were performed in 25 mL 0.1 M HCl solu-
tion by contacting with maximum amount of metal ion absorbed
Ionic composite based on chitosan (CS) and clinoptilolite (CPL) CS4CPL1 composite for 1 h. After removing the CS4CPL1 composite
were prepared as microspheres by a “tandem” ionic/covalent from the desorption medium, the metal ion concentrations were
cross-linking, according to the method previously presented [19]. determined by UV–vis spectroscopy.
Typically, 0.15 g CPL powder was mixed with distilled water, the The regeneration of the CS4CPL1 composite was performed with
volume of water being 1/2 volume of CS solution used for the 0.1 M NaOH, followed by washing to neutral pH.
synthesis of the composite, and kept under vigorous magnetic stir-
ring for 1 h at least. Two volumes of CS solution were mixed with 3. Results and discussion
one volume of water containing the dispersed zeolite, and after
a vigorous magnetic stirring, the epichlorohydrin as cross-linker From the previous study on the influence of zeolite content
was added step-by-step. The mixture thus prepared was added on the adsorption capacity of the CS/CPL composite for Cu2+ ions
by a syringe into an aqueous solution of sodium tripolyphosphate [19] it was observed an abrupt increase of the adsorption capac-
with a concentrantion of 0.05 M, under mild magnetic stirring. ity of CS/CPL composites compared with cross-linked chitosan,
The mass ratio between CS and CPL was 4:1, the sample name starting with the lowest content of CPL loaded in the composite
being CS4CPL1. The composite microspheres were kept under stir- (CS10CPL1), up to about 20% of CPL (CS4CPL1). The increase of the
ring 5 h at 37 ◦C, and then were separated from the dispersion adsorption capacity of the CS/CPL composites compared with cross-
medium and intensively washed with distilled water to remove linked chitosan was explained by a synergy of both components,
the excess of small ions. For characterization in dried state, the the presence of CPL microparticles leading to the increase of the
composite microspheres were filtered off, dried at room temper- accessibility at the functional groups of CS network. Therefore, for
ature for 24 h and under vacuum at 40 ◦C, for 48 h. The average size the present study, the CS4CPL1 composite has been selected to per-
of the microspheres in dry state was 800 µm, measured by envi- form a comparative evaluation of the metal ion removal to examine
ronmental scanning electron microscopy (ESEM) type Quanta 200, the controlling mechanism of the adsorption process the kinetics,
operating at 15 kV with secondary electrons, in high vacuum mode. adsorption isotherms and thermodynamic parameters.
The average size of the composite microspheres in hydrated state
was 1200 µm. 3.1. Effect of pH

2.3. Adsorption studies The pH of the metal ion solution plays an important role in the
whole adsorption process and particularly on the adsorption capac-
Study of the metal ion retention properties of the composites ity by the modification of the level of ionization of CS. Fig. 1 showed
was carried out using a batch equilibrium procedure. Thus, 0.25 g the effect of solution pH on the adsorption capacity of CS 4CPL1
of dried CS4CPL1 composite was placed in a flask and contacted composite for Cu2+, Co2+ and Ni2+.
with 25 mL of the aqueous solution of each metal ion (Cu2+, Co2+ It can be seen from Fig. 1 that the amount of M 2+ adsorbed
and Ni2+) at different temperatures and pH. The kinetics of the by CS4CPL1 composite slowly increased when pH of M 2+ solution
metal ion retention was studied by placing 0.25 g of dried CS4CPL1 increased from 2 to 5, the optimum adsorption pH being located at
composite in 25 mL of aqueous solution of metal ion with a concen- 5. At low pH, most of the amino groups of CS in the composite were
tration of 0.07 mol/L, at 25 ◦C, the equilibrium concentration of the ionized and presented in the form of NH3+, electrostatic repulsion
metal being measured at different contact durations. The contact between M2+ and NH3+ ions may prevent the adsorption of M2+ ions
onto the composite. At pH > 5 the M2+ retention decreased because
time ranged between 2 and 36 h. The effect of medium pH on the
small amount of M2+ started to deposit as M(OH)2. This also sup-
adsorption capacity of the CS4CPL1 composite was investigated in
ports the chelation of M2+ on the CS4CPL1 composite. Considering
the pH range 2.0–6.0 for each metal ion at 25 ◦C. To determine the
Thank you for using www.freepdfconvert.com service!

Only two pages are converted. Please Sign Up to convert all pages.

https://www.freepdfconvert.com/membership