Equilibrium and kinetic modelling of the adsorption of Cd2+ ions onto chestnut shell
Introduction
The industrial waste containing heavy metals constitutes an important source of pollution in water resources, especially due to their toxicity. Therefore, in order to meet regulatory safe discharge standards, it is essential to remove metals from wastewaters before they were released into the environment. Different technologies such as chemical precipitation, ion exchange, coprecipitation/flocculation and carbon adsorption have been developed to remove toxic metal ions from water. Adsorption as compared to others methods, appears to be an attractive process in view of its high efficiency, easy handling and cost effectiveness as well as the availability of different adsorbents [1].
Chestnut shell (from the Castanea sativa species) is generated as a residue of a food factory during the peeling process of chestnut in the “marrón glacé” production, where it is used as fuel. Although other similar lignocellulosic materials such as nut, coconut and walnut shells have received considerable attention as adsorbents of cations from wastewaters [1], [2], no information has been found in the literature on the utilization of chestnut shell as an adsorbent.
There are several parameters which determine sorption rate, such as structural properties of the adsorbent, metal ion properties, cation initial concentration, pH and temperature [3]. In order to design appropriate adsorption treatment plants, it is important to be able to predict the rate at which pollutant is removed from aqueous solutions [4], [5].
In this work, the capacity of chestnut shell as an adsorbent for the removal of Cd2+ ions from aqueous solutions in batch mode was analysed. Three adsorption kinetic models have been applied to evaluate the experimental data: the Lagergren's pseudo first order kinetic model, the Ho's second order rate equation and the intraparticle diffusion kinetic model [3]. The dynamic behaviour of the adsorption process was investigated analysing the effect of Cd2+ initial concentration (15.3, 50.5 and 87.3 mg L− 1) at 25 °C and temperature (15, 25 and 35 °C) at an initial cadmium concentration of 15.3 mg L− 1. In addition, Langmuir and Freundlich isotherms were used to describe the adsorption equilibrium at the three temperatures essayed.
Section snippets
Preparation of the adsorbent
Chestnut shell was supplied by a food factory (Galicia, NW of Spain) which produces chestnut derivatives. It was air dried till equilibrium moisture content (approximately, 18% w/w), ground in a hammer mill and after classified, the fraction with particle sizes between 0.1 and 2 mm was selected. Natural pH of chestnut shell was determined by stirring 1 g of shell in 100 mL of distilled water for 24 h.
Chestnut shell as pretreated with formaldehyde in acid medium to polymerise and immobilise the
Characterization of the adsorbent
The comparison of natural and acid formaldehyde pretreated shell FTIR spectra indicated that the main functional groups remained unchanged after the acid formaldehyde treatment of the shell. On the other hand, FTIR spectra of chestnut pretreated shell before and after cadmium adsorption were used to analyse the changes in the vibrational frequency of the functional groups of the adsorbent (Fig. 1).
The FTIR spectra of the pretreated chestnut shell displayed a great number of absorption peaks,
Conclusions
Chestnut shell was investigated as an adsorbent for the removal of cadmium ions from aqueous solutions. FTIR analysis of the shell before and after cadmium adsorption showed that certain functional groups including ether, alcoholic and amino groups, were involved in the adsorption process. Adsorption kinetics depended on the cadmium initial concentration, temperature and contact time, and could be represented by the pseudo second order model. The initial rate constant and the equilibrium
Acknowledgements
The authors are grateful to Ministerio de Educación y Ciencia, Plan Nacional de I + D + i (AGL2005-00273) and Xunta de Galicia (PGIDIT06PXIC265046PN) for the financial support of this work.
Glossary
List of symbols
- b
- Langmuir constant (L mg− 1)
- Ce
- equilibrium concentration of the solute in the bulk solution (mg L− 1)
- C0
- initial concentration of the solute in the bulk solution (mg L− 1)
- E
- activation energy (kJ mol− 1)
- h0
- initial sorption rate (mg g− 1 min− 1)
- ki
- intraparticle diffusion rate constant (mg g− 1 min− 1/2)
- k0
- rate constant of sorption (g min− 1 mg− 1)
- k1
- pseudo first order rate constant (min− 1)
- k2
- pseudo second order rate constant (g mg− 1 min− 1)
- KF
- Freundlich constant which is indicative of the relative sorption capacity of the
References (23)
- et al.
Water Res.
(1999) - et al.
J. Hazard. Mater.
(2006) - et al.
J. Hazard. Mater.
(2006) - et al.
Biores. Technol.
(1994) - et al.
Biores. Technol.
(2008) - et al.
J. Hazard. Mater.
(2006) - et al.
J. Hazard. Mater.
(2006) - et al.
Water Res.
(2004) - et al.
Ind. Crops Prod.
(2008) - et al.
J. Colloid Interface Sci.
(2004)
Biores. Technol.
Cited by (45)
Fir bark modified by Phanerodontia chrysosporium: A low-cost amendment for cd-contaminated water and agricultural soil
2021, Ecotoxicology and Environmental SafetyAdsorption of Cu (II)and Co (II) from aqueous solution using lignosulfonate/chitosan adsorbent
2020, International Journal of Biological MacromoleculesRemoval of Cd, Pb, Zn, Cu in smelter soil by citric acid leaching
2020, ChemosphereAdsorption behavior of heavy metal ions from aqueous solution onto composite dextran-chitosan macromolecule resin adsorbent
2019, International Journal of Biological MacromoleculesCitation Excerpt :Adsorption isotherm is to explore the relationship between adsorption capacity and adsorption concentration in adsorption equilibrium, that is to say, adsorption capacity is only related to equilibrium concentration at constant temperature. Langmuir adsorption isotherm model, Freundlich adsorption isotherm model, Temkin adsorption isotherm model and D-R adsorption isotherm model are commonly used in isotherm research [15,16,35,36]. The Langmuir adsorption isotherm model assumes that there is an atomic force field on the surface of the adsorbent that is not saturated.
Adsorption performance of a polysaccharide composite hydrogel based on crosslinked glucan/chitosan for heavy metal ions
2019, Composites Part B: EngineeringDescription of adsorption interactions of lead ions with functional groups of pectin-containing substances
2019, Journal of Molecular LiquidsCitation Excerpt :Soft maple wood adsorbs Cu2+ at the level of 9.51 mg g−1 [13]. Among other recommended potential raw materials are ground fern [14], lentil, wheat and mustard husk [3,15], nutshell powder [4], fibers of Agave Americana [16] and coconut [17], ground olive seeds [18] and chestnut shells [19], sugarcane [20], processing products of flax and its biomodification [21–26], as well as fruit [27] waste and other plant materials. Plant sorbents have a developed system of micro-, supermicro- and mesopores and contain biopolymer components capable of different types of interparticle interactions with different mechanisms of substance adsorption from liquid and gas phases.