Article pubs.acs.org/IECR
Preparation, Characterization and Application of Inorganic−Organic Hybrid Polymers, Poly-GPTS/M(CL)xO(OH) Asgar Kayan* Department of Chemistry, Kocaeli University, Kocaeli 41380, Turkey S Supporting Information *
ABSTRACT: Organically modified metal alkoxides were prepared from reactions between metal alkoxides and 1-benzoylcyclohexanol (BCHOH) and 3-pentenoic acid (PAH) in alcohol at room temperature by sol−gel process. Then poly-GPTS was prepared by polymerization of GPTS with KOtBu at 50 °C. After these stages, new hybrid materials Poly-GPTS/M(CL)x(O)/ OH (M = Ti, Zr, Al, CL= 1-benzoylcyclohexanolate (BCHO) and 3-pentenoate (PA), GPTS = 3-glycidyloxypropyltrimethoxysilane) were prepared from hydrolysis of mixtures of poly-GPTS and organically modified metal alkoxides in 1:1 mol ratio. The hydrolysis reactions were carried out with 0.1 molar HCl in 50 mL of alcohol. The characterizations of the hybrid materials were performed by a combination of elemental analysis, thermogravimetric measurements, and spectroscopic methods. After hydrolysis, it was seen that some of the BCHO ligands were removed from the hybrid materials under the studied conditions. To see the activity of hybrid materials as adsorbents, they were used for removal of lead ion from aqueous solution. This study showed that they were very good adsorbents for industrial usage.
1. INTRODUCTION Metal alkoxides and their organic derivatives play an important role in the synthesis of inorganic−organic hybrid materials and polymers by the sol−gel process. Sol gel synthesis of materials from titanium, zirconium, aluminum, and silicon alkoxides has been extensively investigated.1−5 Metal alkoxides are highly reactive to moisture and tend to form oxy-hydroxide precipitates.5,6 Limiting metal alkoxides reactivity with the organic ligands such as organic acids (methacrylic, 3-pentenoic, and acetic acids), diols (cis-2-butene-1,4 diol), and β-ketoesters (allylacetoacetate and ethylacetoacetate) inhibits precipitation formation and allows the preparation of oligomeric or polymeric gels.7−10 When these organic groups were added to metal alkoxides solution, some of the alkoxy groups from starting material were replaced with these chelate-ligands.7−10 Addition of water to these organically modified metal alkoxide complexes leads to hydrolysis of alkoxy groups and condensation reactions resulting in inorganic−organic networks with high surface areas.11,12 In this connection, the unsaturated organic ligands such as 3-pentenoate and 1-benzoylcyclohexanolate are essential for hydrolytic stability and the formation of organic− inorganic network structures. The other modifier compound which is very important in functional coatings, optical devices, adsorbents, and the preparation of glasses and ceramics is GPTS or polyGPTS.13,14 When poly-GPTS was added to metal alkoxides, they gained new positive properties. The concern of this work especially is to broaden the synthesis and hydrolytic stability of inorganic− organic hybrid polymers, poly-GPTS/M(CL)xO(OH). This paper also deals with the preparation, characterization, and use of new complexes with functional groups that provide specific chemical reactivity to adsorb the heavy metal ions from aqueous solution.
3-glycidyloxypropyltrimethoxysilane (97%, Alfa Aesar), 1benzoylcyclohexanol (Aldrich), and 3-pentenoic acid (Fluka, 97%) were used as received. n-Butanol (Fluka, 99%), sec-butanol (Merck, 99), isopropanol (Merck, 99.5%), and tetrahydrofuran (THF) (99.9%, Merck) were dried over activated 4A° molecular sieves before use. Some syntheses were carried out under nitrogen atmosphere. 1 H and 13C{1H}NMR measurements were carried out with a Varian 500 MHz and Bruker 400 MHz Ultra Shield Plus spectrometer. Infrared spectra of complexes were recorded on a Shimadzu 8201/86601 PC spectrometer. The elemental analyses were carried out with a LECO CHNS-932 elemental analyzer. An atomic absorption spectrometer (Perkin-Elmer AA Analyst 800) was used to measure the lead ion concentration in the solutions with and without adsorbents by dilution to an appropriate concentration with distilled water. Thermogravimetric measurements were carried out in a Protherm furnace with a heating and cooling rate of 10 °C/min under air. 2.2. Preparation of [Ti4(OiPr)6(BCHO)4O3]. Ti(OiPr)4 (1.0 g, 3.45 × 10−3 mol) was stirred in 15 mL of isopropanol
2. EXPERIMENTAL SECTION 2.1. Materials and Measurements. Aluminum(III) secbutoxide (97%, Alfa Aesar), titanium(IV) isopropoxide (98%, Merck), zirconium(IV) n-butoxide (80%, Fluka), © 2012 American Chemical Society
Received: Revised: Accepted: Published: 13339
June 6, 2012 September 6, 2012 September 22, 2012 September 22, 2012 dx.doi.org/10.1021/ie301470k | Ind. Eng. Chem. Res. 2012, 51, 13339−13345
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for 2 min and then BCHOH (0.70 g, 3.45 × 10−3 mol) was added to the solution. The mixture was vigorously stirred for 3 h at room temperature. The solvent isopropanol and volatile parts were removed from the mixture under reduced pressure at 30 °C and light yellow very viscous liquid was obtained. Elemental analysis Calcd: C, 59.75; H, 7.31%. Found: C, 59.17; H, 7.48% for Ti4(OiPr)6(BCHO)4O3. 1H NMR, CDCl3, ppm, δ: 1.17 (d, J = 6.1 Hz, CH3, OiPr), 1.30 (m, CH2, BCHO), 1.70 (m, CH2, BCHO), 1.75 (m, CH2, BCHO), 2.05 (m, CH2, BCHO), 4.02 (m, OCH, OiPr), 7.42 (t, J = 7.68, CH, C3, C5, Ph), 7.55 (t, J = 7.1 Hz, CH, C4, Ph), 8.02 (d, J = 7.7 Hz, CH, C2,C6, Ph). 13C NMR, CDCl3, ppm, δ: 21.60 (CH2, C3, C5, BCHO), 25.44 (CH2, C4, BCHO), 25.48 (CH3, OiPr), 35.51 (CH2, C2, C6, BCHO), 64.51 (OCH, OiPr), 78.85 (C, C1, BCHO), 128.37 (CH, C3, C5, Ph), 129.65 (CH, C2, C6, Ph), 132.49 (CH, C4, Ph), 135.35 (C, C1, Ph), 205.63 (CO). FTIR (KBr pellet): 2972 (s), 2943 (s), 1713 (m, C O), 1643 (s, νasymCO..., bidentate), 1596 (m, Ph), 1571 (m, Ph, CC), 1446 (s, νsymCO), 1375 (m), 1361 (m), 1328 (m), 1276 (m), 1240 (m), 1168 (s), 1038 (s), 851 (m), 709 (s), 609 (m), 561 (m). Abbreviations: s: strong, m: medium, w: weak, br: broad, asym: asymmetric, sym: symmetric. 2.3. Preparation of [Ti4(OPri)4(PA)8O2]. Ti(OiPr)4 (1.0 g, 3.45 × 10−3 mol) was stirred in 15 mL of isopropanol for 2 min and then PAH (0.73 g, 6.90 × 10−3 mol) was added dropwise to the solution. The solution changed from cloudy to light yellow within 1 min. The mixture was vigorously stirred for 3 h at room temperature. The solvent isopropanol and volatile parts were removed from the mixture under reduced pressure at 30 °C and yellow viscous liquid was obtained. 1H NMR, CDCl3, ppm, δ: 1.2 (d, CH3, OPri), 1.3 (d, CH3, OPri), 1.65 (m, CH3, PA), 3.0 (br, CH2, PA), 4.6 (sept, CH, OPri, terminal), 5.0 (sept, CH, OPri, bridge), 5.5 (m, CHCH, PA). 13 C NMR, CDCl3, ppm, δ: 18.2 (CH3, PA), 26.4 (CH3, OPri), 38.6 (CH2, PA), 64.6 (CH, OPri), 124.8 (CH3CH, PA), 127.8 (CHCH2, PA), 172.2 (COO-Ti, PA). FTIR (KBr cell): 3036 (w), 2970 (s), 2934 (s), 2882 (m), 1735 (w, C O), 1601 (s, νasymCOO), 1560 (s), 1437 (s, νsymCOO), 1377 (m), 1321 (m), 1258 (m), 1163 (s), 1128 (s), 1080 (s), 1012 (s), 966 (s), 856 (m), 622 (s) 586 (s), 475 (m), cm−1. 2.4. Preparation of [Al6(OsBu)2(BCHO)4O6]. Al(OsBu)3 (0.96 g, 3.78 × 10−3 mol) was stirred in 15 mL of sec-butanol for 2 min and then BCHOH (0.70 g, 3.78 × 10−3 mol) was added to the solution. The mixture was vigorously stirred for 2 h at room temperature. The solvent sec-butanol and volatile parts were removed from the mixture under reduced pressure at 30 °C. The white solid was then washed with hexane or chloroform and dried again. Elemental analysis Calcd: C, 59.21; H, 6.46% for Al6(OC4H9)2(O2C13H15)4O6, C60H78Al6O16, Mw = 1217.42 g/mol. Found: C, 58.12; H, 6.48%. 1H NMR, in DMSO-d6 for soluble part of complex, ppm, δ: 0.86 (t, J = 7.45 Hz, CH3, OsBu), 1.05 (d, J = 6.18 Hz, CH3, OsBu), 1.30 (m, CH2, BCHO and OsBu), 1.50 (t, CH2, BCHO), 1.78 (m, CH2, BCHO), 1.80 (m, CH2, BCHO), 2.1 (m, CH2, BCHO), 3.86 (s, OCH, OsBu), 7.48 (t, J = 7.68, CH, C3, C5, Ph), 7.57 (t, J = 7.1 Hz, CH, C4, Ph), 8.10 (d, J = 7.1 Hz, CH, C2, C6, Ph). 13C NMR, DMSO, ppm, δ: 11.0 (CH3, OsBu), 19.3 (CH3, OsBu), 21.58 (CH2, C3, C5, BCHO), 25.57 (CH2, C4, BCHO), 35.20 (CH2, C2, C6, BCHO and OsBu), 64.8 (OCH2, OsBu), 78.13 (C, C1, BCHO), 128.45 (CH, C3, C5, Ph), 130.11 (CH, C2, C6, Ph), 132.48 (CH, C4, Ph), 136.28 (C, C1, Ph), 205.25 (CO). FTIR (KBr pellet): 3460 (s), 3070 (w), 2934 (s), 2858 (m), 1670 (s, νasym CO), 1600 (m),
1574 (w, Ph, CC), 1446 (s, νsym CO), 1394 (w), 1244 (s), 1157 (m), 1035 (w), 972 (m), 704 (s), 655 (m), 563 (m). 2.5. Preparation of [Al6(OsBu)2(PA)8O4]. A preparative procedure analogous to the above (2.3) was performed in secbutanol. Product was light yellow very viscous liquid. Elemental analysis Calcd: C, 49.49; H, 6.40% for Al6(OC4H9)2(O2C5H7)8O4, C48H74Al6O22, Mw = 1164.98 g/mol. Found: C, 48.73; H, 6.77%. 1H NMR, CDCl3, ppm, δ: 0.96 (t, J = 7.45 Hz, CH3, OsBu), 1.21 (d, J = 6.18 Hz, CH3, OsBu), 1.5 (m, CH2, OsBu), 1.70 (br, CH3, PA), 3.1 (br, CH2, PA), 3.75 (m, OCH, OsBu), 5.62 (m, CHCH, PA). 13C NMR, CDCl3, ppm, δ: 11.0 (CH3, OsBu), 19.1 (CH3, PA), 19.3 (CH3, OsBu), 35.1 (CH2, OsBu), 38.4 (CH2, PA), 64.7 (OCH, OsBu), 123.0 (CH3CH, PA), 129.5 (CHCH2, PA), 172.6 (COOAl, PA). FTIR (KBr, pellet): 2970 (s), 2940 (m), 2920 (s), 2880 (m), 1716 (w, CO), 1585 (s, νasym COO), 1456 (s, νsym COO), 1401(m), 1376 (m), 1262 (m), 1111 (m), 989 (s), 966 (s), 916 (m), 642 (s), 532 (br, s), cm−1. 2.6. Preparation of [Zr4(OnBu)4(BCHO)4O4]. A preparative procedure analogous to the above (2.2) was performed in n-butanol. Elemental analysis Calcd: C, 53.23; H, 6.31%. Found: C, 51.96; H, 6.38% for Zr4(OnBu)4(BCHO)4O4, C68H96O16Zr4, Mw = 1534.38 g/mol. 1H NMR, CDCl3, ppm, δ: 0.94 (t, J = 7.1 Hz, CH3, OnBu), 1.42 (m, CH2, BCHO and OnBu), 1.55−1.65 (m, CH2, BCHO and OnBu), 3.65 (t, OCH2, HOnBu), 4.01 (t, OCH2, OnBu), 7.32 (m, CH, Ph). 13C NMR, CDCl3, ppm, δ: 13.89 (CH3, OnBu), 18.91 (CH2CH3, OnBu), 21.62 (CH2, C3, C5, BCHO), 26.11 (CH2, C4, BCHO), 34.84 (OCH2CH2, OnBu), 35.50 (CH2, C2, C6, BCHO), 62.67 (OCH2, OnBu), 127.17 (CH, C3, C5, Ph), 130.10 (CH, C2, C6, Ph), 132.40 (CH, C4, Ph), 136.20 (C, C1, Ph), 205.18 (CO). FTIR (KBr pellet): 3060 (w), 3025 (w), 2930 (s), 2856 (s), 1732 (m, νasym CO), 1618 (w), 1556 (w, Ph, CC), 1493 (m), 1450 (s, νsym CO), 1376 (w), 1345 (w), 1250 (m), 1149 (s), 1043 (s), 857 (m), 702 (s), 640 (m), 496 (m). 2.7. Preparation of [Zr4(OnBu)4(PA)8O2]. A preparative procedure analogous to the above (2.3) was performed in n-butanol. 1H NMR, CDCl3, ppm, δ: 0.93 (t, CH3, OnBu), 1.35 (m, CH2, OnBu), 1.63 (m, CH2, OnBu), 1.70 (d, CH3, PA), 3.0 (d, CH2, PA), 4.1 (t, OCH2, OnBu), 5.55 (m, CHCH, PA). FTIR (KBr cell): 3032 (m), 2965 (s), 2934 (s), 2918 (s), 2883 (m), 1713 (w), 1585 (s, νasymCOO), 1439 (s, νsymCOO), 1377 (m), 1322 (m), 1256 (m), 1180 (m), 1108 (m), 966 (s), 771 (m), 648 (s), 453 (m), cm−1. 2.8. Polymerization of GPTS with t-BuOK. Poly GPTS was prepared and characterized as in literature.15 The catalyst (40 mg, t-BuOK) was taken in a vial, and 2.5 mL of GPTS was added under nitrogen in a drybox. The mixture was stirred at 50 °C for 48 h. The conversion of monomer (GPTS) to polymers was 100%. 1H NMR, CDCl3, ppm, δ: 4.28 (br, CH), 3.74−3.2 (br, CH, CH3O, CH2, 2CH2O), 1.75 (br, CH2, CH2CH2CH2), 0.72−0.70 (br, CH2−Si). 13C NMR, C6D6, ppm, δ: For CH region: 79.19−79.06 (CH, diad, s/i = syn/iso), 78.81−78.68 (CH, diad, s/i), 71.77−71.69 (CH, diad, s/i), 70.96−70.86 (CH, diad, i/s), 58.66, 58.51, 58.42 (CH). For CH2 region: 74.54 (CH2, broad singlet), 73.78 (CH2, singlet), 72.00−71.94 (CH2, diad, s/i). Other signals: 73.47, 73.27, 72.98 (CH2, OCH2CH2), 72.86, 72.49 (CH2, ring-CH2−O−), 49.99, 49.89, 49.72 (CH3O), 23.96, 23.11 (CH2, CH2−CH2− CH2), 7.51−7.33, 6.39, 5.49 (CH2−Si). 2.9. Hydrolysis of [Poly-GPTS/Zr4(OnBu)4(PA)8O2]. The compounds poly-GPTS (Mw ∼3000 Da) and zirconium 13340
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δ: 1.22 (d, CH3, OiPr), 1.52 (br, CH2, BCHO), 1.74 (br, CH2, BCHO), 2.05 (m, CH2, BCHO), 4.04 (d, J = 3.97 Hz, OiPr), 7.46 (t, J = 7.68, CH, C3, C5, Ph), 7.54 (t, J = 7.1 Hz, CH, C4, Ph), 8.03 (d, J = 7.7 Hz, CH, C2,C6, Ph). FT-IR (KBr pellet): 3422 (m), 2930 (m), 2860 (m), 1674 (s, νasym CO), 1596 (m, Ph, CC), 1575 (w), 1446 (s, νsym CO), 1381 (w), 1313 (w), 1258 (m), 1201 (w), 1158 (m), 1091 (s), 1036 (s), 972 (m), 706 (s), 656 (m), 505 (w) cm−1. 1H NMR spectrum (the peak at 3.48 ppm for C−OH) showed that ∼5% BCHOH was released from complex by hydrolysis. 1H NMR spectrum also includes characteristic peaks for poly-GPTS. 2.12. Hydrolysis of Poly-GPTS/[Al6(OsBu)2(BCHO)4O6]. The hydrolysis reaction of the mixture of poly-GPTS and Al6(OsBu)2(BCHO)4O6 in s-butanol was carried out in a way similar to preparative procedure of 2.9. 1H NMR, in CDCl3, ppm, δ: 1.0 (t, CH3, OsBu), 1.26 (br, CH3, OsBu), 1.33 (br, CH2, BCHO), 1.50 (m, CH2, BCHO and OsBu), 1.60 (d, GPTS), 1.72 (m, CH2, BCHO), 2.75 (br, GPTS), 3.35 (m, OCH, OsBu), 4.55 (s, OH), 7.18 (t, CH, C3, C5, Ph), 7.27 (t, CH, C4, Ph), 7.90 (d, CH, C2,C6, Ph). FTIR (KBr): 3430 (m), 2935 (m), 2860 (m), 1676 (s, νasym CO), 1597 (m, Ph, CC), 1577 (w), 1436 (s, νsym CO), 1379 (w), 1313 (w), 1261 (w), 1246 (m), 1196 (m), 1090 (s), 819 (m), 787 (m), 704 (m), 656 (m), 507 (w) cm−1. 2.13. Removal of Lead(II) Ion from Aqueous Solution. All these experiments were performed at initial pH 5.50−6.00. The solutions of Pb2+ ion (from Pb(NO3)2) and hybrid materials (2.5 mg) were mixed for 10 min. After stirring 10 min, the solutions were filtered with quantitative filter and then measured by AA spectrometer. The results are summarized in Table 1.
pentenoate were mixed in 1:1 mol ratio in 50 mL of isopropanol and stirred for a few minutes. Then the mixture was hydrolyzed by 0.1 molar HCl. Four mol of water per mol of Zr(OnBu)4 and 3 mol of water per mol of −Si(OCH3)3 (GPTS) were added dropwise to the solution and stirred for 24 h at room temperature. After 24 h of stirring, the volatile parts of mixture were removed under reduced pressure at 50 °C and a beige solid was obtained. Elemental analysis Found: C, 33.17; H, 5.63%. The TGA of the hydrolyzed product showed a weight loss of 38% up to 800 °C. 1H NMR, CDCl3, ppm, δ: 0.75−1.25 (m, CH2, CH3, OnBu and GPTS), 1.64 (dd, CH3, PA), 3.0 (d, OCH2, PA), 3.4 (s, GPTS), 3.6 (m, GPTS), 4.0 (OCH2, OnBu), 5.55 (m, CHCH, PA). FT-IR (KBr pellet): 3412 (s), 2965 (m), 2937 (m), 2920 (m), 2860 (m), 1716 (w, CO), 1560 (s, vasym COO), 1437 (s, vsym COO), 1398 (s), 1321(m), 1261 (w), 1198 (w), 1094 (s), 1045 (s), 966 (m), 636 (m), 465 (m), cm−1. The peaks at 1716 (CO) and 1437 (CO) cm−1 in the FTIR spectrum showed that ∼10% 3-pentenoate was coordinated to zirconium as monodentate. 2.10. Hydrolysis of [Poly-GPTS/[Al6(OsBu)2(PA)8O4]. The hydrolysis reaction of the mixture of poly-GPTS and Al6(OsBu)2(PA)8O4 in s-butanol was carried out in a way similar to preparative procedure of 2.9. 1H NMR, CDCl3, ppm, δ: 1.75 (d, CH3, PA), 3.1 (d, OCH2, PA), 5.56 (m, CHCH, PA). FT-IR (KBr pellet): 3460 (s), 2970 (m), 2939 (m), 2881 (m), ∼1716 (w, CO), 1585 (s, νasym, bidentate coordinated COO), 1454 (s, νsym COO), 1377 (w), 1302 (m), 1257 (w), 1201 (w), 1111 (s), 1055 (s), 968 (m), 623 (s), 517 (w), cm−1. 2.11. Hydrolysis of Poly-GPTS/[Ti4(OiPr)6(BCHO)4O3]. The hydrolysis reaction of the mixture of poly-GPTS and Ti4(OiPr)6(BCHO)4O3 in isopropanol was carried out in a way similar to preparative procedure of 2.9. 1H NMR, CDCl3, ppm,
3. RESULTS AND DISCUSSION In this study, 1-benzoylcyclohexanolate Ti, Zr, and Al-alkoxides and 3-pentenoate Al-alkoxide complexes were synthesized for the first time. The 1-benzoylcyclohexanolate Ti, Zr, and Alalkoxide compounds were prepared between 1-benzoylcyclohexanolate and metal alkoxides in alcohol at room temperature and were characterized as mentioned in the Experimental Section. The formulations of complexes were based on the
Table 1. Results of the Lead Ion Adsorption on Novel Inorganic−Organic Hybrid Polymer metal ion
initial concn. (mg/L)
hydrolyzed product of poly-GPTS q(mg/g)
Pb2+
20.0
165.2
hydrolyzed hydrolyzed product of poly- product of n GPTS-Zr(O Bu) poly-GPTS-ZrPA q(mg/g) q(mg/g) 185
176
Figure 1. 1H NMR spectrum of [Ti4(OiPr)6(BCHO)4O3]. 13341
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Figure 2. 13C NMR spectrum of [Ti4(OiPr)6(BCHO)4O3].
integration of 1H NMR spectra and the amounts of hydrogen and carbon measured by elemental analysis. 1H NMR data showed the expected characteristic peaks and peaks multiplicities (Figure 1). For example, the 1H NMR spectrum of Ti4(OiPr)6(BCHO)4O3 compound gave peaks at 1.17 (d, CH3, OiPr), 1.3 (m, CH2, BCHO), 1.70 (m, CH2, BCHO), 1.75 (m, CH2, BCHO), 2.05 (m, CH2, BCHO), 4.02 (m, OCH, OiPr), 7.42 (t, J = 7.68, CH, C3, C5, Ph), 7.55 (t, J = 7.1 Hz, CH, C4, Ph), 8.02 (d, J = 7.7 Hz, CH, C2,C6, Ph) ppm. Also characteristic 13C NMR data for Ti4(OiPr)6(BCHO)4O3 complex were observed at 21.60 (CH2, C3, C5, BCHO), 25.44 (CH2, C4, BCHO), 35.51 (CH2, C2, C6, BCHO), 78.85 (C, C1, BCHO), 128.37 (CH, C3, C5, Ph), 129.65 (CH, C2, C6, Ph), 132.49 (CH, C4, Ph), 135.35 (C, C1, Ph), 205.63 (CO) ppm (Figure 2). The structure of Ti-BCHO complex can be drawn as shown in Scheme 1. These two types of compounds (M-BCHO and M-PA) were also characterized by FTIR spectroscopy. The characteristic CO, COM bands were observed at the expected place in the FTIR spectrum (Figure 3). FTIR measurements showed that BCHO ligand can coordinate to metals both in bidentate (CO, ∼1640 cm−1, medium intensity) and monodentate (CO, ∼1713 cm−1, COM, 1038 cm−1) forms. Therefore, it is also possible to draw the structures of BCHO compounds as shown in Scheme 2. PA modified Ti and Zr alkoxides complexes gave results similar to previously published works about titanium and zirconium pentenoate.16 The difference here is the mole numbers of pentenoic acid. The mole numbers of pentenoate ligand were increased from 1 to 2 for Ti and Zr alkoxides. The spectroscopic techniques showed that the pentenoate ligand was bonded to metals in mostly bidentate form. The 13C NMR spectrum of free 3-pentenoic acid shows signal at δ = 179 ppm for COOH. When 3-pentenoic acid was added to metal alkoxides compounds in 1:2 molar ratio (M(OR)4 or 3/PA), alkoxy groups substitute with PA. The 13C NMR spectra of M-complexes indicate that carboxy group of coordinated PA shift to ∼172 ppm from ∼179 ppm. The signal for the −COOH proton of M-complexes in the 1H NMR spectrum is
Scheme 1. Structure of [Ti4(OiPr)6(BCHO)4O3] Complex
absent. Lack of a COOH proton signal indicates that 3-pentenoic acid is completely coordinated to metal. All these data are consistent with literature data.16 New inorganic−organic hybrid polymers, poly-GPTS/M(CL)(O)/OH were prepared by hydrolysis of mixtures of polyGPTS and pentenoate−metal alkoxides and 1-benzoylcyclohexanolate−metal alkoxides in 1:1 mol ratio. The hydrolysis reactions were carried out by 0.1 molar HCl in alcohol at room temperature. These new compounds were also characterized by elemental analysis and spectroscopic techniques. Elemental analysis measurement and thermogravimetric measurement of inorganic−organic hybrid material of hydrolyzed product polyGPTS/Zr(PA)(O) showed that the organic part (C, H) was approximately 38%. FTIR spectroscopy gave more idea about hydrolyzed products. Both ligands 3-pentenoate and 1-benzoylcyclohexanolate were still bonded to metals after hydrolysis reactions by HCl(aq). The carboxyl (CO), carboxylate (COO), and olate (C−O−M) group (occurring from C−OH) 13342
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Figure 3. FTIR spectra of pure BCHOH and [Ti4(OiPr)6(BCHO)4O3] complex.
alkoxides, the peak at 1089 cm−1 disappeared in the FTIR spectrum. This disappearance supported the fact that the SiOCH3 groups underwent condensation reactions. After condensation reactions, new peaks appeared at 1110−1090 cm−1 for Si−O−Si17 and ∼968 cm−1 for Si−O−M (M = Zr, Ti, Al) bonds, respectively. FTIR spectrum also showed a peak at ∼3465−3410 cm−1 because of the presence of OH groups bonded to Si and metal atoms. The peak at ∼1200 cm−1 in the FTIR spectra can be attributed to CH2−Si bond. The synthesis of hybrid materials using 3-pentenoate can be summarized as in Scheme 3. These hybrid materials (or adsorbents) were used to remove toxic metal ions from aqueous solution. Hybrid materials contain many oxygen atoms which can form bonds with toxic metal ions. The binding properties of hybrid material for Pb2+ ion were tested by immersing the Zr-PA(O) hybrid material in a solution containing a lead ion. The binding of the Pb2+ ion by hybrid material is illustrated in Figure 4. The maximum Pb2+ binding capacity is ∼176 mg for Zr-hybrid material at pH 5.5− 6.0. It is clear that the tendency of the hybrid material to bind Pb2+ ion is greater than some adsorbents examined in literature studies under the same conditions. It is well-known that Pb2+ is the easiest metal ion to be coordinated to compounds containing oxygen atoms.18 However, the binding ability of Zr(PA)-hybrid material was somewhat lower than the other Zr,Ti-adsorbents without chelate ligands as shown in Table 1.
Scheme 2. Structures of BCHO-Ti, Al, Zr Compounds
were at ∼1716 (CO, monodentate coordinated PA), ∼16001560 (COO, bidentate coordinated PA), and ∼1040 cm−1 in FTIR spectra, respectively. 1H NMR spectra for hydrolyzed products gave the peaks of coordinated PA and BCHO. The poly-GPTS was prepared from tBuOK and GPTS monomer as in my published articles.15 FTIR studies support the condensation reactions between poly-GPTS and organically modified metal alkoxides compounds in the presence of HCl(aq). The poly-GPTS shows characteristic bands at 1089 cm−1 for Si-OMe bonds. When poly-GPTS underwent condensation with metal 13343
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This is very reasonable because chelate ligand includes more organic parts and they remain bonded to metal atoms after hydrolysis reactions. When the organic parts of hybrid materials increase, the adsorption ability of hybrid materials decreases. The effects of the amount of adsorbent on the metal adsorption are shown in Figure 5. When the adsorbent amount is increased, the adsorption sites increase. It is obvious that the high adsorption capacity is decreased with increasing amount of the adsorbent as shown in Figure 5. Low amount of adsorbent provided high adsorption capacity. In literature, there are many adsorbents which give similar results while metal ions are adsorbed.19 It can be noticed that saturation of the adsorption sites and agglomeration could be the reason of the decrease in adsorption capacity. However, the removal percentage of metal ions increases with increasing the adsorbent amount to an optimum value. In these experiments, the optimum amount of the adsorbent was taken as 2.5 mg for lead ion. In spite of the small amount of adsorbents, they have good attractive sites for lead ion. As this study shows, the results have great importance for removal of metal ions using a very small amount of adsorbent. As seen from Table 1, all adsorbents have a high maximum adsorption capacity (165−185 mg/g) and percentage removal (85−99%) for Pb2+ ion. As a result of the large number of highly electronegative oxygen atoms, the maximum capacity and percentage removal of adsorbed lead ion were higher in poly-GPTS-Ti than poly-GPTS-Zr(PA).
Scheme 3. Synthesis of Inorganic−organic Hybrid Material (Si−Zr(PA))
Figure 4. Effect of initial lead ion concentrations on the adsorption of lead ion on hydrolyzed poly-GPTS (Δ) and poly-GPTS/Zr(PA) (□).
Figure 5. Effect of the amounts of hydrolyzed poly-GPTS (△) and poly-GPTS/Zr(PA) (□) on the adsorption of lead ion. 13344
dx.doi.org/10.1021/ie301470k | Ind. Eng. Chem. Res. 2012, 51, 13339−13345
Industrial & Engineering Chemistry Research
Article
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4. CONCLUSIONS New compounds were prepared from reactions between metal alkoxides and 1-benzoylcyclohexanol (BCHOH) and 3-pentenoic acid (PAH) by sol−gel process. Then, hybrid materials poly-GPTS/M(CL)x(O)/OH were prepared from hydrolysis of mixtures of poly-GPTS and BCHO-Ti, BCHO-Al, BCHO-Zr and PA-Ti, PA-Al, PA-Zr. All compounds were characterized successfully by a combination of elemental analysis and spectroscopic methods. New hybrid materials were used as adsorbents and were very effective in removing Pb2+ ions from aqueous solution.
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ASSOCIATED CONTENT
S Supporting Information *
FTIR and 1H NMR spectra for compounds 2.2−2.12. This information is available free of charge via the Internet at http:// pubs.acs.org/.
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AUTHOR INFORMATION
Corresponding Author
*Tel.: +90 2623032018. Fax: +90 2623032003. E-mail:
[email protected]. Notes
The authors declare no competing financial interest.
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ACKNOWLEDGMENTS
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REFERENCES
This work was supported by the research foundation of Kocaeli University (project 2009/034).
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dx.doi.org/10.1021/ie301470k | Ind. Eng. Chem. Res. 2012, 51, 13339−13345
