Annals of West University of Timisoara

Size: px

Start display at page:

Download "Annals of West University of Timisoara"

Caroline Price
5 years ago
Views:

Annals of West University of Timisoara Series of Chemistry 19 (4) 9-18 ADSORPTION OF TRACE METALS BY XAD7 IMPREGNATED RESINS WITH DI-(2-ETHYLHEXYL)- PHOSPHORIC ACID (DEHPA) Mihaela Ciopec a, Adina

2, Timisoara, 300006, ROMANIA b Romanian Academy, Institute of Chemistry, Mihai Viteazul Blv., no.

1 Annals of West University of Timisoara Series of Chemistry 19 (4) 9-18 ADSORPTION OF TRACE METALS BY XAD7 IMPREGNATED RESINS WITH DI-(2-ETHYLHEXYL)- PHOSPHORIC ACID (DEHPA) Mihaela Ciopec a, Adina Negrea a, C.M. Davidescu a, P. Negrea a, Cornelia Muntean a, Adriana Popa b a University Politehnica Timisoara, Faculty of Industrial Chemistry and Environmental Engineering, Piata Victoriei, no. 2, Timisoara, , ROMANIA b Romanian Academy, Institute of Chemistry, Mihai Viteazul Blv., no. 24, Timisoara, , ROMANIA Received: 12 November 2010 Modified 17 November 2010 Accepted 23 November 2010 SUMMARY In the present work, we tested the adsorption of metals on solvent impregnated resin (SIR). Di-(2-ethylhexyl)-phosphoric acid (DEHPA) has been chosen as an extractant for the purpose of this study. The Amberlite XAD7 resin was impregnated with DEHPA by dry impregnation method. Adsorption on the XAD7 support macro and interaction between the extractant and support has been emphasized by physicochemical methods of analysis (FTIR spectroscopy). The experimental studies on adsorption of metal ions (Pb 2+, Cu 2+, Cd 2+, Cr 3+, Ni 2+, Fe 3+, Zn 2+, Ca 2+ ) were carried out using the SIR prepared by impregnation of Amberlite XAD7 with an organophosphorous extractant DEHPA. A separation method was developed for metals ions and was investigated the influence of stirring on the residual concentration of metal ions, on their removal efficiency and on the adsorption capacity of resin towards metal ions. Keywords: Amberlite XAD7; DEHPA; solvent impregnated resin (SIR); trace metals 9

2 C IOPEC M., N EGREA A. ET AL. INTRODUCTION In recent years, increasing interests in environmental protection, economy of energy, as well as process optimization and continuous progress in fundamental chemistry have produced an important development of new chemical separation techniques. The recovery of metal ions from dilute solutions using solvent impregnated resins (SIR) has been proposed as a technological alternative to solvent extraction techniques [1]. It has been shown that macro-porous polymeric resins containing an extractant within their lattice provide the best use of the advantages of both solvent extraction and ion exchange [2, 3]. Heavy metals are major pollutants in marine, ground, industrial and even treated wastewaters. Some of them are very toxic even at low concentrations. The pollution with heavy metals has become severe with the development of economy. Special attention is paid to the heavy metals which can cause illness such as cancer. The traditional techniques used for metal removal are based on chemical precipitation coupled to pre- or post-oxidation/reduction followed by filtration in order to concentrate the species of interest. The main disadvantage of these techniques is the production of solid residues containing toxic compounds whose final disposal is in general land filling (which is the last priority in terms of EU policies) [4]. Industrial waste streams contaminated with heavy metal ions are frequently encountered in practice. Such streams often containing solutions of metal ions such as copper, nickel, zinc, cadmium, chromium, lead, mercury and aluminum may be produced as effluents from various industrial processes [5]. The need for more specific systems for recovery of heavy metals from their dilute solutions from both ecological and economic aspects has led to the development in the synthesis of new complexing extractants, ion-exchangers, and adsorbents [6]. These products have significantly improved the selectivity and efficiency of a large number of techniques for separation process, such as membrane separation and selective adsorption [7]. These techniques may be ineffective or non-economical because of several technical and environmental constraints [5]. Among these new products, solvent-impregnated resins (SIR) have been postulated as an effective alternative for the separation and recovery of species from dilute solution. The use of macro-porous organic polymers, with a high surface area and good mechanical stability and flow characteristics, containing selective extraction reagents offers many advantages over the use of liquid liquid extraction [1]. The concept of the SIR is now well developed and has a strong place in extraction chromatography at analytical application scale and is of potential application at industrial scale [8]. 10

3 ADSORPTION OF TRACE METALS BY XAD7 IMPREGNATED RESINS Many studies are dealing with sorption and separation of metal with SIR [1]. The objectives of these studies were mainly devoted to explain the impregnation processes and to study the physical structure of SIR beads [9-12]. The present paper investigates the adsorption of metal ions (Pb 2+, Cu 2+, Cd 2+, Cr 3+, Ni 2+, Fe 3+, Zn 2+, Ca 2+ ) using the SIR prepared by impregnation of Amberlite XAD7 with an organophosphorous extractant DEHPA. A separation method was developed for metals ions and was investigated the influence of stirring on the residual concentration of metal ions, on their removal efficiency and on the adsorption capacity of resin towards metal ions. MATERIALS AND METHODS A. Reagents Di(2-ethylhexyl) phosphoric acid (DEHPA) ~ 98.5% was supplied by BHD Chemicals Ltd Poole England and used as received. As organic solvent was used ethanol from Chimopar Romania. Stock solutions of Pb(II), Cu(II), Cd(II), Cr(III), Ni(II), Fe(III), Zn(II), Ca(II) were prepared using Merck Standard Solutions of Me(NO 3 ) 2 and Me(NO 3 ) 3 respectively, in HNO mol/l. All other chemicals used for experiments were of analytical reagent grade, and were used without further purification. Distilled water was used in all experiments. B. Instrumentation The FTIR spectra of Amberlite XAD7-DEHPA impregnated resin were recorded using a Shimadzu FTIR spectrophotometer in the range cm 1 with 2 cm 1 resolution and 40 scans using KBr discs. For batch experiments a mechanical shaker bath MTA Kutesz, Hungary was used. The concentration of metal ions was determined using a Varian SpectrAA 280 Fast Sequential Atomic Absorbtion Spectrometer with an air-acetylene flame at wavelengths =217 nm (Pb 2+ ), =324.8 nm (Cu 2+ ), =228.8 nm (Cd 2+ ), =357.9 nm (Cr 3+ ), =232 nm (Ni 2+ ), =248.3 nm (Fe 3+ ), =213.9 nm (Zn 2+ ) and =422.7 nm (Ca 2+ ). RESULTS 1. Preparation of impregnated resins For the impregnation we used the dry method [13, 14]. The extractant content of the impregnated resin was determined by potentiometric titration with 0.1 M NaOH in ethanol. 2. Procedure for removal of metal ions (Pb 2+, Cu 2+, Cd 2+, Cr 3+, Ni 2+, Fe 3+, Zn 2+, 11

4 C IOPEC M., N EGREA A. ET AL. Ca 2+ ) from aqueous solutions. Samples of 0.1g Amberlite XAD7-DEHPA impregnated resin were mixed at room temperature (27 C) with 25 ml single metal solution containing 10 mg/l Me n+ (where Me n+ = Pb 2+, Cu 2+, Cd 2+, Cr 3+, Ni 2+, Fe 3+, Zn 2+, Ca 2+ ) at several shake times (15, 30, 45, 60, 90 and 120 min.). Adsorption of metal ions on impregnated resin was studied in single component solutions and in solutions containing all cations (in this solution the concentration of each cation was of 10 mg/l). The suspensions were filtered and the concentration of metal ions in the filtrate was determined by means of atomic absorption spectrometry. The amount of Me n+ (where Me n+ = Pb 2+, Cu 2+, Cd 2+, Cr 3+, Ni 2+, Fe 3+, Zn 2+, Ca 2+ ) sorbed, q (mg Me n+ /g SIR), was calculated as follows: ( C o C t ) V q t [mg Me n+ /gsir] (1) m where C o and C t are the initial and residual concentrations of Me n+ in the solution at 0 and t moments respectively (mg/l), V is the volume of the solution (ml) and m is the mass of the resin sample (g). The metals removal efficiency (, %), was calculated using the equation: ( Co C t ) 100 [%] (2) C o where C o and C t have the same meanings as before. DISCUSSION 1. Evaluation of the interaction between XAD7 resin and di-(2-ethylhexyl)- phosphoric acid (DEHPA) The IR spectra of the XAD7 exhibit three bands at 2975 (strong, sharp), 2930 and 2890 cm 1 attributed to the stretching modes (asymmetric and symmetric) of aliphatic C-H groups. In addition, the absorption bands at 1477 and 1390 cm 1 are due to C-H deformation of -CH 3. The absorption band at 1745 cm 1 corresponds to C=O stretching. Two absorption bands at 1135 and 1260 cm 1 attributed to C O stretching are also observed. The IR spectra of XAD7 show also the presence of a broad band attributed to -OH stretching at 3450 cm 1 due to presence of water. The band assigned to P O C has shifted from 989 to 1029 cm 1 and P=O absorption band is observed at 1229 cm -1 [3]. 2. Retention of metal ions on XAD7 DEHPA impregnated resin 2.1. Retention of metal ions in single component solutions a. Influence of contact time (stirring) at the adsorption capacity of metal ions on 12

5 ADSORPTION OF TRACE METALS BY XAD7 IMPREGNATED RESINS XAD7 DEHPA impregnated resin Experimental data of the influence of contact time (stirring) at the adsorption capacity of metal ions on the XAD7 DEHPA impregnated resin are shown in Figure 1. 3,00 Metals adsorption capacity, mg Me n+ /g SIR 2,50 2,00 1,50 1,00 0,50 0, Time, minutes Pb2+ Cd2+ Cr3+ Cu2+ Ni2+ Fen+ Zn2+ Ca2+ Figure 1. Influence of contact time (stirring) at the ion adsorption capacity XAD7-DEHPA impregnated resin The experimental data of contact time (stirring) increases with increasing of adsorption capacity. Adsorption equilibrium is reached after 45 minutes, regardless of metal ions studied. XAD7 DEHPA impregnated resin with phosphate groups shows higher affinity for metal ions with larger radius, this is confirmed by data from literature [1, 2]. Thus, for trivalent ions (Fe 3+, Cr 3+ ) affinity is higher than for those divalent (Pb 2+, Cu 2+, Cd 2+, Ni 2+, Zn 2+, Ca 2+ ). b. Influence of contact time (stirring) at the efficiency of removal of metal ions solutions Experimental data of the influence of contact time (stirring) at the efficiency of removing metal ions from solutions are shown in Figure 2. 13

6 C IOPEC M., N EGREA A. ET AL. 120,00 Metals removal efficiency, % 100,00 80,00 60,00 40,00 20,00 Pb2+ Cd2+ Cr3+ Cu2+ Ni2+ Fen+ Zn2+ Ca2+ 0, Time, minutes Figure 2. Influence of contact time (stirring) at the efficiency of removal of ions metal On the basis of studies was observed that the efficiency process of retaining the metallic ions on XAD7 DEHPA impregnated resin functionalized with phosphate groups increase with the increasing of stirring time, reaching values for trivalent ions of ~ 80%. For studied divalent ions the efficiency of retention is lower (~ 70%) Retention of metal ions from mixed cation solutions a. Influence of contact time (stirring) at the adsorption capacity of metal ions on XAD7 DEHPA impregnated resin Experimental data of the influence of contact time (stirring) at the adsorption capacity of metal ions from solutions with a mixture of cations on XAD7 DEHPA impregnated resin is shown in Figure 3. From experimental data was observed that with increasing contact time (stirring) increases adsorption capacity, reaching adsorption equilibrium after 45 minutes, for all metal ions studied. 14

7 ADSORPTION OF TRACE METALS BY XAD7 IMPREGNATED RESINS Metals adsorption capacity, mg Me n+ /g SIR 0,615 0,515 0,415 0,315 0,215 0,115 0, Time. minutes Pb2+ Cd2+ Cr3+ Cu2+ Ni2+ Fen+ Zn2+ Ca2+ Figure 3. Influence of shaking time at adsorption capacity of metal ions from solutions with mixed cations resin on XAD7- DEHPA impregnated resin b. Influence of stirring time at removal efficiency of metal ions from solutions with mixed cations The experimental data for the influence of agitation time at removal efficiency of metal ions from mixed cation solutions are shown in Figure 4. 15

8 C IOPEC M., N EGREA A. ET AL. 25 Metals removal efficiency, % Pb2+ Cd2+ Cr3+ Cu2+ Ni2+ Fen+ Zn2+ Ca Time, minutes Figure 4. Influence of stirring time at removal efficiency of metal ions from mixed cation solutions On the basis of studies was observed that the effectiveness of the retaining XAD7- DEHPA impregnated resin with phosphate group increases with increasing the stirring time. Note that resin retained selective Cr 3+ and Zn 2+ from cationic mixture. For Cr 3+ and Zn 2+ was achieved an effective retention of ~ 20%. For the others cations from mixture, was observed that retention efficiencies is < 5%. CONCLUSION Amberlite XAD7 sample was impregnated with DEHPA by dry method and was evaluated by FTIR spectra, it can see that the bands appear at wavelengths characteristic P- O-C (903 to 1027 cm -1 ) and P = O (1230 cm -1 ). To study the possibility of using impregnated resin as material adsorbent for eliminate the metal ions from solutions were used solutions with one component of metal ion Pb 2+, Cu 2+, Cd 2+, Cr 3+, Ni 2+, Fe 3+, Zn 2+, Ca 2+, respectively solutions with mixed metal ions, aiming to influence the mixing time / contact at the efficiency of retention and the 16

9 ADSORPTION OF TRACE METALS BY XAD7 IMPREGNATED RESINS retention capacity of the resin. It was observed that impregnated resin with phosphate groups shows affinity for metal ions, revealing a higher affinity for trivalent metal ions (Cr 3+, Fe 3+ ) due to their larger size. At the same time the process of retaining, i.e. adsorption went with the best results when using single component solutions. When mixed cation solutions were used, the efficiency of retention / adsorption is lower, this is probably due to competition between metal ions existent. The capacity adsorption increases with increasing the contact time and it arrive at equilibrium after 45 minutes. Acknowledgements This work was partially supported by the strategic grant POSDRU/89/1.5/S/57649, Project ID (PERFORM-ERA), co-financed by the European Social Fund Investing in People, within the Sectoral Operational Programme Human Resources Development REFERENCES 1. Cortina J. L., Miralles N., Aguilar M., Warshawsky A., Solid-liquid distribution studies of divalent metals from nitrate media using impregnated resins containing a bifunctional organophosphorous extractant (O-methyl-dihexyl-phosphine-oxide O -hexyl-2-ethyl phosphoric acid), React. Funct. Polym., 27 (1995) Cortina J.L., Warshawsky A., in: (Marinsky J.A., Marcus Y., Eds.), Ion Exchange and Solvent Extraction, vol. 13, Marcel Dekker, New York, Draa M.T., Belaid T., Benamor M., Extraction of Pb(II) by XAD7 impregnated resins with organophosphorus extractants (D2EHPA, IONQUEST 801, CYANEX 272), Sep. Purif. Technol., 40 (2004) Edebali S., Pehlivan E., Evaluation of Amberlite IRA96 and Dowex 1 8 ion-exchange resins for the removal of Cr(VI) from aqueous solution, Chem. Eng. J., 161 (2010) Muscatello A.C., Navratil J.D., Plutonium removal from nitric acid waste streams, J. Radioan. Nucl. Ch. Le., 128 (1988) Apostolidis C., Bekelund H., Glatz J.P., in: (Cecille L., Csarci M., Pietrelli L., Eds.), New Separation Chemistry Techniques for Radioactive Waste and Other Specific Applications, Elsevier, London, UK, Horwitz E.P., Dietz M.L., Nelson D.M., LaRosa J.J., Fairman W., Concentration and separation of actinides from urine using a supported bifunctional organophosphorus extractant, Anal. Chim. Acta, 238 (1990) Cortina J.L., Miralles N., Sastre A.M., Aguilar M., Solid-liquid extraction studies of divalent metals with impregnated resins containing mixtures of organophosphorus extractants, React. Funct. Polym., 32 (1997) Spencer R.G.M., Aiken G.R., Dyda R.Y., Butler K.D., Bergamaschi B.A., Hernes P.J., Comparison of XAD with other dissolved lignin isolation techniques and a compilation of analytical improvements for the analysis of lignin in aquatic settings, Org. Geochem., 41 (2010) Rovira M., Hurtado L., Cortina J.L., Arnaldo J. S., Sastre A.M., Recovery of palladium(ii) from hydrochloric acid solutions using impregnated resins containing Alamine 336, React. Funct. 17

10 C IOPEC M., N EGREA A. ET AL. Polym., 38 (1998) Masi A.N., Olsina R.A., Preconcentration and determination of Ce, La and Pr by X-ray fluorescence analysis, using Amberlite XAD resins loaded with 8-Quinolinol and 2-(2-(5 chloropyridylazo)-5-dimethylamino)-phenol, Talanta, 40 (1993) Masi A.N., Olsina R.A., Preparation and characterization of chelating resins loaded with 2-(5- bromo-2-pyridylazo)-5-diethylamino)phenol for preconcentration of rare earth elements, Fresen. J. Anal. Chem, 357 (1997) Benamor M., Bouariche Z., Belaid T., Draa M.T., Kinetic studies on cadmium ions by Amberlite XAD7 impregnated resins containing di(2-ethylhexyl) phosphoric acid as extractant, Sep. Purif. Technol., 59 (2008) Kabay N., Cortina J.L., Trochimczuk A., Streat M., Solvent-impregnated resins (SIRs) Methods of preparation and their applications, React. Funct. Polym., (2010), in press. 18

Heavy metal extraction by a counter-flow moving bed reactor

Vol.4, No., 99- () http://dx.doi.org/.436/ns..48 Natural Science Heavy metal extraction by a counter-flow moving bed reactor Azza H. Ali, M. Abdelaziz, H. F. Elbakhshawangy, Sameh H. Othman * Nuclear Research