Colloids and Surfaces A: Physicochemical and Engineering Aspects
Adsorptive removal of thorium(IV) from aqueous solutions using poly(methacrylic acid)-grafted chitosan/bentonite composite matrix: Process design and equilibrium studies
Introduction
Thorium is a naturally occurring radioactive element widely distributed over the earth's crust with nuclear significance. The toxic nature of this radionuclide, even at trace levels, has been a public health problem for many years [1]. Some human activities such as exploitation of ores with associated thorium and nuclear fuel reprocessing can also concentrate this element [2]. Thorium is an important model element for tetravalent actinides in natural waters. It is also useful as a tracer when studying environmentally important processes [3]. The effluents containing Th(IV) are known to cause acute toxicological effects and harmful diseases for human such as lung, pancreatic and liver cancer [4]. A number of techniques including chemical precipitation, electro floatation, ion exchange, reverse osmosis and adsorption have been developed to recover thorium from aqueous solutions. At low concentrations, separation/preconcentration through adsorption of long-lived radioactive radionuclides such as thorium from aqueous solution is important in nuclear/radiation chemistry and environmental/waste treatment chemistry [5], [6], [7]. The composite ion-exchangers have been used in several studies for the treatment of low and medium level liquid radioactive wastes [8]. Chitosan (CTS) is a biopolymer obtained by deacetylation of naturally occurring biopolymer chitin, which is abundant in nature, principally in shells of crustaceans, terrestrial invertebrates and fungi [9], [10]. Chitosan is an effective ion-exchanger, with a large number of amino groups which are responsible for the high adsorption property of chitosan, but in its original form, chitosan is a relatively weak base (pKa ∼ 6.2) soluble at acidic media at pH < 6.0. Chemical modification of CTS may be used to prevent the solubility when metal adsorption is performed in acidic solutions [11], [12].
The polymer/clay composites with eco-friendly property and biodegradability were developed by earlier workers for various applications [13], [14], [15]. Particularly, the natural materials, such as starch, cellulose and CTS have attracted great attention due to their abundant resources and degradability [16], [17]. The composite matrix based on natural material could be decomposed by microorganisms, and there by compatible to the natural environment. The objective of this work is to prepare a novel adsorbent, poly(methacrylic acid)-grafted chitosan/bentonite composite (PMAA-g-CTS/B) matrix for the recovery of Th(IV) ions from water and simulated sea water. It was proposed to take advantage of the cation exchange capacity of the carboxyl group from the adsorbent surface to recover Th(IV) ions from aqueous solutions.
Section snippets
Materials
Analytical grade chemicals were used through out the investigation. CTS (Sigma–Aldrich, Milwau-kee, WI, USA) was used for the preparation of adsorbent. The stock solution of Th(IV) (1000 mg/L) was prepared by dissolving 2.459 g Th(NO3)4·5H2O (Fluka Chemie AG, Buchs, Switzerland) in distilled water at 1000 mg/L of Th(IV). All the required working solutions were prepared by diluting the stock solution with distilled water. The methacrylic acid (MAA) was obtained from Fluka. Potassium persulfate
Adsorbent characterization
The IR spectra of CTS, PMAA-g-CTS/B, and Th(IV)-loaded-PMAA-g-CTS/B are shown in Fig. 1. The spectrum of pure CTS shows peak around at 3450 cm−1 corresponding to amine N–H symmetrical vibration and H bonded –OH group in CTS. The peaks present on the range 3400–3800 cm−1 were also indicate the –OH and –NH2 moieties in the CTS backbone. The intense peaks at 2890 and 2320 cm−1 are assigned to the symmetric and asymmetric –CH2 vibrations of carbohydrate ring. The CTS spectrum also shows the
Conclusions
In the present study, a novel adsorbent, poly(methacrylic acid)-grafted chitosan/bentonite composite (PMAA-g-CTS/B) was prepared and characterized. Its efficiency in removing Th(IV) was tested by batch adsorption technique. The pH 6.0 was found to be optimum for the adsorption of Th(IV) on PMAA-g-CTS/B. The kinetic experiments showed that the adsorption follows a pseudo-second-order kinetic model which indicates that adsorption involves chemical reaction in addition to physical adsorption.
Acknowledgements
The Financial support of the major research project (F.No. 37-425/2009 (SR)) received for the study from the University Grants Commission, New Delhi is gratefully acknowledged. Mr. Rijith S. expresses his sincere thanks to the University Grants Commission, New Delhi for the financial support in the form of Research Fellowship to carry out this work. The authors also thank Dr. Shripathi T. at the UGC-DAE consortium for scientific research, Indore, Madhya Pradesh for providing the XPS
References (31)
- et al.
Adsorption of thorium on amorphous silica: an EXAFS study
J. Colloid Interface Sci.
(1997) - et al.
Uranium(VI) bio-coordination chemistry from biochemical, solution and protein structural data
Coord. Chem. Rev.
(2006) - et al.
Separation, preconcentration and inductively coupled plasma-mass spectrometric (ICP-MS) determination of thorium(IV), titanium(IV), iron(III), lead(II) and chromium(III) on 2-nitroso-1-naphthol Impregnated MCI GEL CHP20P resin
J. Hazard. Mater.
(2010) - et al.
Solid phase extraction and preconcentration of uranium(VI) and thorium (IV) on duolite XAD761 prior to their inductively coupled plasma spectrometric determination
Talanta
(2007) - et al.
Metal complexation by chitosan and its derivatives: a review
Carbohyd. Polym.
(2004) - et al.
Structure and mechanical properties of superabsorbent poly (acrylamide)-montmorillonite composite hydrogels
Polymer Gels Netw.
(1993) - et al.
Adsorption of transition metal ions from aqueous solutions onto a novel silica gel matrix inorganic–organic composite material
J. Hazard. Mater.
(2010) - et al.
Expansion and hydrodynamic properties of cellulose-stainless steel powder composite matrix for expanded bed adsorption
J. Chromatogr. A
(2006) - et al.
Thermogravimetric and FTIR studies of chitosan blends
Thermochim. Acta
(2003) - et al.
Metal anion sorption on chitosan and derivative materials: a strategy for polymer modification and optimum use
React. Funct. Polym.
(2004)
Evidence of lithium–nitrogen interaction in chitosan-based films from X-ray photoelectron spectroscopy
Mater. Sci. Eng. B
The mobility of thorium in natural waters at low temperatures
Geochim. Cosmochim. Acta
Amine-modified polyacrylamide–bentonite composite for the adsorption of humic acid in aqueous solutions
Colloids Surf. A: Physiocochem. Eng. Asp.
Actinide speciation in the environment
Radiochim. Acta
Thorium removal from aqueous solutions of mexican erionite and X zeolite
J. Radioanal. Nucl. Chem.
Cited by (158)
Carboxyl-functionalized UiO-66-NH<inf>2</inf> for efficient capture of Th(IV) in aqueous solution: Experimental and DFT study
2024, Separation and Purification TechnologyModulation of the properties of starch gels by a one-step extrusion modification method based on Ca<sup>2+</sup>-citric acid synergistic crosslinking
2024, International Journal of Biological MacromoleculesPerformance of novel pillared eggshell-bentonite clay bio-composite for enhanced phosphate adsorption from aqueous media
2023, Groundwater for Sustainable DevelopmentAquatic biomass cellulose fabrication into cellulose nanocomposite and its application in water purification
2023, Journal of Cleaner Production