Determination and extraction of zinc from aqueous solution using ion-imprinted polymer

Size: px

Start display at page:

Download "Determination and extraction of zinc from aqueous solution using ion-imprinted polymer"

Leonard Perkins
6 years ago
Views:

International Research Journal of Applied and Basic Sciences 214 Available online at www.irjabs.

1 International Research Journal of Applied and Basic Sciences 214 Available online at ISSN X / Vol, 8 (6): Science Explorer Publications Determination and extraction of zinc from aqueous solution using ion-imprinted polymer Mohammad reza rezaei kahkha 1, Massaud kaykhaii 2 1. faculty of health, Zabul university of medical science, Zabul, Iran. 2. Department of chemistry, University of Sistan&Baluchestan, Zahedan, Iran. *Corresponding Author m.r.rezaei.k@gmail.com ABSTRACT: Zinc is an environmental pollutant, which has been tested and assessed over the past few years from both the toxicological and human health viewpoints.at present study Imprinted polymer particles have been developed as a novel adsorbent for the adsorption of zinc from aqueous solution.zinc-imprinted polymer was prepared with methacrylic acid (MAA) as the functional monomers, thleneglycoldimethacrylate (EGDMA) as the cross-linking agent, 2,2 -azobisisobutyronitrile (AIBN) as the initiator and Zn (II) ion as the imprint ion. The template Zn (II) ion was removed from the polymer by leaching with a liquid of a 1:1 volumetric ratio of HCl to ethylenediaminetetraacetic acid (EDTA). The capacity and selectivity of Zn(II) ion adsorption were investigated with the imprinted polymer and it s nonimprinted counterpart. The polymer has a maximum adsorption capacity at 7.. The isotherm of their batch adsorption of Zn(II) ions shows a Langmuir adsorption pattern. Imprinted polymer have a much higher capacity and higher selectivity of Zn(II) adsorption than non-imprinted ones. The limit of detection of the proposed method was.13 µg L -1. This research showed that Ion imprinting can be a promising technique of preparing selective adsorbents to separate and preconcentrate metal in a medium of multiple competitive metals. The method was applied to the recovery and determination of zinc in water and waste water samples. Keywords: ion imprinted polymer; preconcentration; atomic absorption spectrometry; zinc ion; selective adsorption INTRODUCTION3 Molecular imprinting is a technique for preparing polymeric materials of high molecular recognition ability. This technique creates template-shaped cavities in polymer matrices with a memory of the template molecules, and thus provides synthetic material with artificial recognition sites. In molecular imprinting, monomers with appropriate functional radicals interact with template molecules, and then the radicals are fixed with chemical cross-linking agents. After removing the template molecules from the imprinted polymers, recognition sites are available to bind selectively the template or its analogue (Birlik et al., 26). Ion-imprinted polymers (IIPs), similarly to molecular imprinted polymers (MIPs), can work under extreme conditions, such as in a very acidic or alkaline medium, at a high temperature, at a high pressure and in an extremely toxic environment. (Shea et al., 1989 ). The selectivity of an ion-imprinted polymeric adsorbent is based on the specificity of the ligand concerning the coordination geometry, coordi-nation number, charge and size of ions. In addition to being simple and convenient to prepare, IIPs have outstanding advantages such as predetermined selectivity. Hence, IIPs are actively researched for their catalytic applications, stationary phases in chromatographic column and flow-injection column, solid-phase extraction (SPE) (Rao et al., 24), catalysts (Puoci et al., 25), membrane separation and sensors development (Rao et al 24). The development of new methods for quantifying trace metals is required but may be challenging. In some common procedures for the determination of low concentrations of heavy metals, a preconcentration step is required before performing the analysis. (kala, 24) A particularly promising application of IIPs is the SPE preconcentration of a metal from other coexisting metals, which is very difficult to accomplish with other methods.(kala, 24). IIP-SPE offers an approach to the recovery of valuable and rare materials from lean ores, minerals and dilute solutions, and to the removal of toxic uranium and heavy metal pollutants from industrial wastes (Wallas et al., 28). Moreover, the imprinting effect

2 may result in preparation of high purity rare earth oxides in view of the reported high selectivity of high coefficients.(rutkowska et al., 28) In this study, a Ion- imprinting polymer was used for selective extraction and preconcentration of zinc complex from water and waste water samples. In synthesis processes methacrylic acid (MAA), thyleneglycoldimethacrylate (EDMA) and 2,2 -azobisisobutyronitrile (AIBN) were used as zinc functional monomers, cross-linker and initiator, respectively. The synthesized polymer was applied for the selective extraction of zinc from sample solution. The effect of various experimental conditions, e.g., adsorption and desorption time on the extraction efficiency were investigated and optimized. The aim of this research was to synthesize and investigate ability of Ion Imprinted polymers technique for adsorbing of zinc from aqeous solutions under various conditions. Consequently, the influence of several operating parameters such as, ion equilibrium concentration were investigated. Furthermore, equilibrium isotherms were used to identify the possible mechanism of the adsorption process. MATERIALS AND METHODS AIBN (2,2 -azobisisobutyronitrile) was obtained from Merck. All chemicals reagent, including MAA (methacrylic acid), HCl, EGDMA (ethleneglycoldimethacrylate) and EDTA (ethylenediaminetetraaceticacid), were analytical grade and purchased form fluka Corporation. Preparation of polymers IIP particles was synthesized in two steps: (i) preparing complexes of zinc with MAA, as the ligand; (ii) copolymerizing the complexes with EGDMA as crosslinking monomers and methanol as porogen. The complex of zinc (II) with a ligand was prepared with a mixture of 1 mmol of ZnSO 4 and the ligand dissolved in 1 ml methanol. The amount of ligand was 4 mmol MAA. Into the zinc (II)-ligand solution, 2 mmol EGDMA and.8 g AIBN were added and mixed. The mixed solution was then put in a polymerizing glass-reactor that was sealed after being flushed with bubbling nitrogen, and was kept at 6 C for 24 h. The polymerization proceeded at 8 C for 3 h and finished. The obtained polymer was ground in a mortar and dried in a hot air oven at 6 C for 6 h. The dry polymer was sieved to get particles smaller than 45 μm. The Zn (II) ions were removed from polymer particles by leaching with a liquid of a 1:1 volumetric ratio of HCl to ethylenediaminetetraacetic acid (EDTA). Non -imprinted polymer particles were prepared in the same way except that the imprinting of Zn(II) ion was skipped. Adsorption measurement The adsorption of metal ion from an aqueous solution was determined by measuring the concentration of the metal in adsorption equilibrium with an atomic absorption spectrophotometer ( Shimadzu AA7). The value of the solution was measured with BEL digital meter. The polymer concentration was kept constant at 1 g/l (the specific dosage was 5 mg polymer in 5 ml solution). The amount of adsorbed ions was calculated by : Where Q is the mass of adsorbed ions divided by the mass of adsorbing polymer;c and C are the concentrations of Zn ion before and after extraction in the solution; V is the volume of aqueous phase ; m is the mass of polymer. RESULTS Effect of on adsorption Metal ion adsorption on to specific adsorbents is dependent. In the absence of functional agents, the hydrolysis and the precipitation of metal ions are affected by the concentration and form of soluble metal species. The effect of on the adsorption of Zn(II) ions by polymers is illustrated in Fig. 1 which shows the adsorbed amount of Zn(II) ions by imprinted MAA polymer changes remarkably with. 78

3 Q Figure1. Effect of on the adsorption of zinc ions. All imprinted polymers have the strongest affinity at 7.. The affinity is weaker in a more acidic medium with <7. owing to the competition of H + ions in an acidic medium with Zn(II) ions to form a complex with a ligand. When > 7., the affinity decreases because a more alkaline favors forming Zn (II) hydroxide rather than Zn (II) complex in the competitive equilibrium. Effect of Zn(II)-ion equilibrium concentration The adsorbed amount of Zn(II) ions onto polymer is related to the equilibrium concentration of Zn (II) ions in an aqueous solution. The adsorbed amount increases with the equilibrium concentration before the saturation of active binding cavities on the polymer when the equilibrium concentration exceeds 5 mg L 1 (Fig. 2). Imprinted polymer adsorbs much more Zn (II) ions than nonprinted polymer does. The isotherm of batch adsorption of Zn (II) ions by imprinted polymer shows a Langmuir adsorption pattern (Fig. 3). The dependence of the adsorbed amount of Zn (II) ions by ion-imprinted polymer on the equilibrium concentration exhibits a linear relation,with a correlation coefficient (R 2 ) of The Langmuir adsorption model assumes that the molecules are adsorbed at a fixed number of well-defined sites, each site holding only one molecule. These sites are also assumed to be energetically equivalent and distant to each other so that no interactions exist between molecules adsorbed to adjacent sites. Q Zn(mg/L) Imprinted Non- Imprinted Figure2. Effect of equilibrium concentration of zn +2 on the adsorption of zinc ions. C/q(g/L) C(mg/L) Figure3. Langmuir isotherm for the batch adsorption of Zn(II)ions by Zn(II) ion-imprinted MAA polymer 79

4 Adsorbtion selectivity Selecting coefficients of zinc ions over the other selected inorganic cations that coexisted with zinc ions in natural sources were studied by batch procedure. The IIP particles were tested for separation of zinc ions from Zn +2, Mn +2, Mg +2 and Cd +2 ions either individually or in mixtures. The concentrations of transition metals were determined by Atomic Absorption Spectrometer. The selectivity of the zinc ions versus another cation was determined by the ratio of the two partition coefficients, D zn +2 and D m n+, which is referred to the selectivity factor, α: D zn +2 D m n+ The phase distribution ratio (D) was calculated using the following equation Where D is the distribution coefficient; C i and C f represent the initial and final solution concentrations, respectively; and V is the final volume of the aqueous solution. The obtained results are summarized in Table 1. As it is clear from the results, quantitative separation of zinc from other cations is possible. Compared to other metal ions, the selectivity factor values demonstrate that the IIP synthesized for the Zn 2+ has a higher selectivity Table 1. Selectivity factor and Distribution ratio of zinc imprinted polymer. Foreign ion Distribution ratio(d) Selectivity factor(α) Zn(II) Mn(II) Mg(II) cd(ii) CONCLUSIONS Ion imprinting remarkably improves both the capacity and the selectivity of zinc (II) ion adsorption onto polymers of methacrylic acid (MAA). The best condition for Zn(II) adsorption is at 7.. The Zn(II) ionimprinted MAA polymer is a preferable adsorbent to extract and preconcentrate Zn(II) ions in an aqueous solution of multiple competitive metal ions, effectively resisting their interference. The conditions to synthesize ion imprinted polymers are mild, and there are plenty of options for functional monomers. The ion-imprinting method is a useful technique for the preparation of adsorbents for the separation of ions, such as zinc from aqueous solutions. Ionimprinted adsorbent is a new type of carrier that can considerably enhance the adsorption capacity and the selectivity of ions. In order to assess the applicability of the method to real samples with different matrixes, it was applied to the extraction and separation of zinc ions from 4 ml of three different water samples. As seen, the results of three analysis of each sample show that the zinc recovery was almost quantitative. Table 2. Recovery of 1.2 µg zinc added to 4 ml of sample Sample Spiked amount(µg L - Zinc found(µg L -1 ) Recovery(%) R.S.D(%) 1 ) Tap Water Waste water REFERENCES Ahmadi SJ, Kalkhoran O. NArani SS.21.Synthesis and characterization of new ion-imprinted polymer for separation and preconcentration of uranyl (UO 2 2+ )ions, J. Hazard. Mater. 175; Beltran A, Marcé RM, Cormack PA, Borrull F.29. Synthesis by precipitation polymerization of molecularly imprinted polymer microspheres for the selective extraction of carbamazepine and oxcarbazepine from human urine, J.Chromatogr A 1216; Birlik E, Ersoz A, Denizli A.26. Preconcentration of copper using double-imprinted polymer via solid phase extraction.analytica Chimica Acta, 26, 565:

5 Cui Y, Chang X, Zhu X, Luo H, Hu Z, Zou X, He Q.27.Chemically modified silica gel with p-dimethylaminobenzaldehyde for selective solid phase extraction and preconcentration of Cr(III), Cu(II), Ni(II), Pb(II) and Zn(II) by ICP-OES. Microchem J, 87(1):2 26. Gallegos MG, Olivas RM, Cámara C.29.Different formats of imprinted polymers for determining organotin compounds in environmental samples, J. Environ. Manage. 9 ; Kala R, Gladis JM, Rao TP.24. Preconcentrative separation of erbium from Y, Dy, Ho, Tb and Tm by using ion imprinted polymer particles via solid phase extraction. Analytica Chimica Acta, 518: Kanazawa R, Mori K, Tokuyama H, Sakohara S.24.Preparation of thermo sensitive microcell adsorbent for quick adsorption of heavy metal ions by a temperature change, J. Chem. Eng. 37; Masci G, Aulenta F, Crescenzi V.22.Uniform-sized clenbuterol molecularly imprinted polymers prepared with methacrylic acid or acrylamide as an interacting monomer, J. Appl. Polym. Sci. 83; Metilda P, Prasad K, Kala R, Gladis JM, Rao TP, Naidu GRK.27. Ion imprinted polymer based sensor for monitoring toxic uranium in environmental samples, Anal. Chim. Acta 582 ; Okutucu B, Telefoncu A.28. Optimization of serotonin imprinted polymers and recognition study from platelet rich plasma, Talanta. 76 ; Puoci F, Garreffa C, Iemma F, Muzzalupo R, Spizziri UG, Picci N.25. Molecularly imprinted solid phase extraction for detection of sudan I in food matrixes. Food Chem, 93: Rao TP, Daniel S, Gladis JM.24. Tailored materials for preconcentration or separation of metals by ion imprinted polymers for solid-phase extraction. Trends in Analytical Chemistry, 23: Rao TP, Kala R, Daniel S.26. Metal ion-imprinted polymers novel materials for selective recognition of inorganics.(26) Analytica Chimica Acta, 578(2): Rutkowska J, Kilian K, Pyrzynska K.28. Removal and enrichment of copper ions from aqueous solution by 1, 8-diaminonapthalene polymer. Eur Polymer J, 44: Vigeau O, Pinel C, Lemire M.21. Ionic imprinted resins based on EDTA and DTPA derivatives for lanthanides (III) separation [J]. Analytica Chimica Acta, 21, 435 (1): Walas S, Tobiasz A, Gawin M, Trzewik B, Strojny M, Mrowiec H.28.Application of a metal ion-imprinted polymer based on salen-cu complex to flow injection preconcentration and FAAS determination of copper. Talanta, 28, 76(1): Wang XB, Zheng ZH, Ding XB, Cheng X, Hu XH, Peng YX.26.Synthesis of molecularly imprinted polymer particles by suspension polymerization in silicon oil, Chin. Chem. Lett. 17; Zhu QH, He JF, Feng JY.27.Optimization of the process parameters of synthesis of vinblastine imprinted polymer, Eur. Polym. J. 43;

INTRODUCTION AND OBJECTIVES

CHAPTER 1 INTRODUCTION AND OBJECTIVES 1. 1. Introduction Molecular imprinting technology has over the past few years developed to become a capable alternative to common analytical methods based on recognition