- Email: [email protected]
Direct hydrothermal synthesis of zirconium phosphate and zirconium arsenate with a novel basic layered structure in alkaline media
$sKRY OMMUNICATIONS
ELSEVIER
Inorganic
Chemistry
Communications
1 ( 1998) 206-208
Direct hydrothermal synthesis of zirconium phosphate and zirconium arsenate with a novel basic layered structure in alkaline media Abraham Clearfield a**, Anatoly I. Bortun a, Lyudmila N. Bortun a, Josd R. Garcia b “Department of Chemistry, Texas A&M University, College Station, 7X 77843-3266, USA b Departamento de Q&mica Orgbnica e Inorgcinica, Universidad de Oviedo, 33071 Oviedo, Spain Received 2 October 1997
Abstract
The hydrothermal synthesis in alkaline media of several zirconium phosphatesand arsenatesof general formula Zr,O,( M’M”0,) . nHzO (where M’= H, Na, K, NH4;M” = P, As, n = l-3) with the novel basic $-type layered structure is reported. 0 1998Elsevier Science S.A. All rights reserved. Keywords: Zirconium
compounds;
Phosphate compounds;
Arsenate compounds;
Among the various inorganic materials of current interest, layered polyvalent metal phosphates occupy a special position. This attention is related to the possibility of their application as highly selective ion exchangers, acid catalysts, protonic conductors and novel functionalized materials [l-4]. Two basic types of layered zirconium phosphates are known and have been studied in detail. They are (Yand &zirconium phosphates represented by formulae Zr( HPO& . H,O and Zr( PO,) (H,PO,) *2H,O, respectively. These compounds were first prepared by Cleatfield et al. [ $61 by reflux methods. Both zirconium phosphates have a layered structure. In cw-ZrPmetal atoms lie very nearly in a plane and are bridged by monohydrogenphosphate groups [7,8], whereas in y-ZrP zirconium octahedra dual planar sheets are connected though phosphate tetrahedra and the dihydrogenphosphate groups are linked axially to the metal atoms [ 9, lo]. Such an arrangement of atoms creates sufficiently large openings to the inner ‘zeolite-type’ cavities located between the layers, which enables exchange between protons and outer ions, intercalation of organic molecules and pillaring. Recently, Cleat-field and co-authors [ 111 have shown that treatment of a-ZrP with NaOH or KOH under mild hydrothermal conditions leads to the formation of a novel metastable zirconium-rich phosphate of the formula Zr,O, ( MP04) . nH20 (M = Na, K; n = 1, 2)) designated as the @-phase.Characterization of t,&ZrPrevealed that it has a layered structure, exhibits extremely high hydrolytic stability * Corresponding
author. Tel.: + l-409-845
1387-7003/98/$ - see front matter 0 PIIs1387-7003(98)00055-0
2936; Fax: + l-409-845
1998 Elsevier
2370
Layered compounds
in alkaline media and has a preference for uptake of large cations. Further investigation has shown that alkali metal zirconium phosphates, as well as alkali metal zirconium arsenates, with the new @type structure, can be prepared by a direct hydrothermal reaction in alkaline media between zirconium- and phosphorus- ( or arsenic-) containing reagents taken in the molar ratio Zr:P(As) of about 2:l. It is noteworthy that this is the only example of zirconium phosphates or arsenates that have been synthesized in alkaline media. We report here the results of these experiments. In all cases a 70% solution of zirconium propoxide (in npropanol) was used as an initial source of zirconium and 85% H3P04 or As,OS +3H,O were used as the source of phosphorus or arsenic. The synthetic procedure included first the preparation of an H3P04 ( As205 *3H,O)-MOH (M = Na, K, NH,) solution with MOH:P(As) molar ratio (4-5):l and then mixing Zr( O&H7 )4 and the phosphorus ( arsenic) -containing solutions in the molar ratio P( As) :Zr = 1:2 in a 100 ml stainless steel Teflon lined vessel. In all cases the total volume of the reaction mixture was 60 ml. The reaction mixture was then sealed and heated at 190°C for 5-6 days. The solid product was filtered, thoroughly washed with an excess of deionized water, and dried in air at 60°C. The results of elemental analysis and the interlayer spacings of all the synthesized compounds are given in Table 1. Under the given experimental conditions only $-ZrP and t&-ZrAssamples with relatively low crystallinities are formed. It was found that an increase of the duration of the hydrothermal synthesis (from 5 to 30 days), and either increase or
Science S.A. All rights reserved.
A. Clearjield et al. /Inorganic Chemistry Communications I (1998) 206-208
207
Table 1 Elemental analysis and the interlayer spacings of +-ZrP and $-ZrAs samples Compound
Zr,03( NaPO,) .I .8H,O Zr,07( KPOd) 1.7H20 Zr203(NH,P0,) .0.9H20 Zrz03(NaAs0,).3.3H,0 Zr,03(KAs0,) .2.5H,O Zr,O,(mAsOd) .0.9Hz0
d”
Found (%)
(A)
Zr
P (As)
Mb
Zr
P (As)
Mb
13.3 14.0 12.8 15.3 15.0 13.1
47.6 46.2 48.8 39.9 40.0 42.3
8.2 7.9 8.7 16.8 16.4 18.1
6.2 10.0 3.7 (N) 5.2 8.6 3.6 (N)
47.89 46.19 49.30 39.45 39.25 43.39
8.16 7.86 8.40 16.23 16.15 17.86
6.05 9.90 3.79 4.98 8.41 3.34
Calculated
(%)
a The position of the first reflection in the XRD powder pattern. ’ M = Na, K or nitrogen.
Fig. 1. The SEM magnification).
photograph
of Zr,O,(NaPO.,)
.1.8H,O (20 000 X
-3 6
1 5
1
I
I
I
15
I
25 28
I 35
I
contain NH,Zr, (PO,) 3 or NI-L,Zr,(AsO,) 3 as an admixture. We relate this to the fact that NH,OH cannot create a sufficiently high pH in the reaction mixture (as is in the case of NaOH or KOH) to hydrolyze other zirconium phosphate or arsenate compounds that could be formed under these conditions. The electron micrograph, presented in Fig. 1, shows the typical morphology of the hydrothermally grown crystals of +-ZrP-Na (at 20 000 X magnification). The particles are small and have a broad size range (from 0.1 to 1 mm) and an irregular shape. The lack of a clearly defined morphology correlates with the low crystallinity of the compounds. The XRD powder patterns of t,&ZrP-Naand +ZrP-K are identical to those belonging to the compounds prepared via partial hydrothermal decomposition of cw-ZrPand described in our recent paper [ I 11, The XRD powder patterns of bl/-ZrAs-Na %nd+ZrAs-K having a first X-ray reflection at 15.3 and 15.0 A, respectively, are presented in Fig. 2. The layered zirconium phosphates and arsenates are stable both in acid and alkaline solutions. In acid media they could be easily converted to the proton phase by exhaustive treatment with 0.5-2 M HCl or HNO,. Characterization of the proton phase +-ZrAs-H will be reported separately. The IR spectra of $-ZrAs-K and J/-ZrAs-Na are shown in Fig. 3. The adsorption bands in the 84CL1020 cm-’ region are assigned
I
El
ldeg)
Fig. 2. The XRD powder patterns of +ZrAs-Na
(a) and t,!+ZrAs-K (b)
decrease of the alkalinity of the reaction mixture (in the range of pH 11-14) do not result in a substantial improvement in the crystallinity. Additionally, ‘in the case of the use of NH,OH, as the source of alkali, (CI-ZrPand ICI_ZrAs samples
I
I
2800
I
I
I
1600 Wavenumber
Fig. 3. The IR spectra of $-ZrAs-Na
I
800 (cm ‘1 (a) and $-ZrAs-K
(b)
208
A. Clear$eld et al. /Inorganic Chemistry Communications I (1998) 206-208
to symmetric and antisymmetric stretching modes of As-O bonds in the AsO, group [ 121. The bands in the 500-700 cm- ’region are connected with Zr-0 orl and Zr-O-As bond vibrations. The broad bands in the OH stretching regions (1625-1635 and 3400-3500 cm-‘) arise from surface and interlayer water. The presence of ammonium ion in +-ZrAsNH, manifests itself by bands at 1412 and 3 195 cm- ’. To summarize, a new synthetic route for the preparation of zirconium phosphates and arsenates, possessing a new I,/+ type layered structure, is reported.
References [ I] A. Clearfield (Ed.), Inorganic Ion Exchange Materials, CRC Press, Boca Raton, PL, 1982.
[21 G. Alberti, in: P.A. Williams, M.J. Hudson (Eds.), Recent Developments in Ion Exchange, Elsevier, London, 1987. r31 A. Clearfield, in: D.L. Cocke, A. Clearfield (Eds.), Design of New Materials, Plenum, New York, 1987. I41 G. Alberti, M. Casciola, U. Costantino, R. Viviani, Adv. Mater. 8 (1996) 291. [51 A. Clearfield, J.A. Stynes, J. Inorg. Nucl. Chem. 26 (1964) 117. 161 A. Clearfield, R.H. Blessing, J.A. Stynes, J. Inorg. Nucl. Chem. 30 (1968) 2249. r71 A. Clearfield, G.D. Smith, Inorg. Chem. 8 (1969) 431. 181 J.M. Troup, A. Clearfield, Inorg. Chem. 16 ( 1977) 3311. PI A.N. Christensen, E.K. Anderson, LG. Anderson, G. Alberti, M. Nielson, MS. Lehmann, Acta Chem, Stand. 44 ( 1990) 865. 1101D.M. Poojaq,B. Shpeizer, A. Clearheld, J. Chem. Soc.,DaltonTrans., (1995) 111. [Ill AI. Bortun, L.N. Bortun, A. Cleariield, Solvent Extr. Ion Exch. 15 (1997) 305. [I21 N.G. Chemorukov, LA. Korshunov, I.M. Zhuk, Russ. J. Inorg.Chem. 27 (1982) 1728.
ELSEVIER
Inorganic
Chemistry
Communications
1 ( 1998) 206-208
Direct hydrothermal synthesis of zirconium phosphate and zirconium arsenate with a novel basic layered structure in alkaline media Abraham Clearfield a**, Anatoly I. Bortun a, Lyudmila N. Bortun a, Josd R. Garcia b “Department of Chemistry, Texas A&M University, College Station, 7X 77843-3266, USA b Departamento de Q&mica Orgbnica e Inorgcinica, Universidad de Oviedo, 33071 Oviedo, Spain Received 2 October 1997
Abstract
The hydrothermal synthesis in alkaline media of several zirconium phosphatesand arsenatesof general formula Zr,O,( M’M”0,) . nHzO (where M’= H, Na, K, NH4;M” = P, As, n = l-3) with the novel basic $-type layered structure is reported. 0 1998Elsevier Science S.A. All rights reserved. Keywords: Zirconium
compounds;
Phosphate compounds;
Arsenate compounds;
Among the various inorganic materials of current interest, layered polyvalent metal phosphates occupy a special position. This attention is related to the possibility of their application as highly selective ion exchangers, acid catalysts, protonic conductors and novel functionalized materials [l-4]. Two basic types of layered zirconium phosphates are known and have been studied in detail. They are (Yand &zirconium phosphates represented by formulae Zr( HPO& . H,O and Zr( PO,) (H,PO,) *2H,O, respectively. These compounds were first prepared by Cleatfield et al. [ $61 by reflux methods. Both zirconium phosphates have a layered structure. In cw-ZrPmetal atoms lie very nearly in a plane and are bridged by monohydrogenphosphate groups [7,8], whereas in y-ZrP zirconium octahedra dual planar sheets are connected though phosphate tetrahedra and the dihydrogenphosphate groups are linked axially to the metal atoms [ 9, lo]. Such an arrangement of atoms creates sufficiently large openings to the inner ‘zeolite-type’ cavities located between the layers, which enables exchange between protons and outer ions, intercalation of organic molecules and pillaring. Recently, Cleat-field and co-authors [ 111 have shown that treatment of a-ZrP with NaOH or KOH under mild hydrothermal conditions leads to the formation of a novel metastable zirconium-rich phosphate of the formula Zr,O, ( MP04) . nH20 (M = Na, K; n = 1, 2)) designated as the @-phase.Characterization of t,&ZrPrevealed that it has a layered structure, exhibits extremely high hydrolytic stability * Corresponding
author. Tel.: + l-409-845
1387-7003/98/$ - see front matter 0 PIIs1387-7003(98)00055-0
2936; Fax: + l-409-845
1998 Elsevier
2370
Layered compounds
in alkaline media and has a preference for uptake of large cations. Further investigation has shown that alkali metal zirconium phosphates, as well as alkali metal zirconium arsenates, with the new @type structure, can be prepared by a direct hydrothermal reaction in alkaline media between zirconium- and phosphorus- ( or arsenic-) containing reagents taken in the molar ratio Zr:P(As) of about 2:l. It is noteworthy that this is the only example of zirconium phosphates or arsenates that have been synthesized in alkaline media. We report here the results of these experiments. In all cases a 70% solution of zirconium propoxide (in npropanol) was used as an initial source of zirconium and 85% H3P04 or As,OS +3H,O were used as the source of phosphorus or arsenic. The synthetic procedure included first the preparation of an H3P04 ( As205 *3H,O)-MOH (M = Na, K, NH,) solution with MOH:P(As) molar ratio (4-5):l and then mixing Zr( O&H7 )4 and the phosphorus ( arsenic) -containing solutions in the molar ratio P( As) :Zr = 1:2 in a 100 ml stainless steel Teflon lined vessel. In all cases the total volume of the reaction mixture was 60 ml. The reaction mixture was then sealed and heated at 190°C for 5-6 days. The solid product was filtered, thoroughly washed with an excess of deionized water, and dried in air at 60°C. The results of elemental analysis and the interlayer spacings of all the synthesized compounds are given in Table 1. Under the given experimental conditions only $-ZrP and t&-ZrAssamples with relatively low crystallinities are formed. It was found that an increase of the duration of the hydrothermal synthesis (from 5 to 30 days), and either increase or
Science S.A. All rights reserved.
A. Clearjield et al. /Inorganic Chemistry Communications I (1998) 206-208
207
Table 1 Elemental analysis and the interlayer spacings of +-ZrP and $-ZrAs samples Compound
Zr,03( NaPO,) .I .8H,O Zr,07( KPOd) 1.7H20 Zr203(NH,P0,) .0.9H20 Zrz03(NaAs0,).3.3H,0 Zr,03(KAs0,) .2.5H,O Zr,O,(mAsOd) .0.9Hz0
d”
Found (%)
(A)
Zr
P (As)
Mb
Zr
P (As)
Mb
13.3 14.0 12.8 15.3 15.0 13.1
47.6 46.2 48.8 39.9 40.0 42.3
8.2 7.9 8.7 16.8 16.4 18.1
6.2 10.0 3.7 (N) 5.2 8.6 3.6 (N)
47.89 46.19 49.30 39.45 39.25 43.39
8.16 7.86 8.40 16.23 16.15 17.86
6.05 9.90 3.79 4.98 8.41 3.34
Calculated
(%)
a The position of the first reflection in the XRD powder pattern. ’ M = Na, K or nitrogen.
Fig. 1. The SEM magnification).
photograph
of Zr,O,(NaPO.,)
.1.8H,O (20 000 X
-3 6
1 5
1
I
I
I
15
I
25 28
I 35
I
contain NH,Zr, (PO,) 3 or NI-L,Zr,(AsO,) 3 as an admixture. We relate this to the fact that NH,OH cannot create a sufficiently high pH in the reaction mixture (as is in the case of NaOH or KOH) to hydrolyze other zirconium phosphate or arsenate compounds that could be formed under these conditions. The electron micrograph, presented in Fig. 1, shows the typical morphology of the hydrothermally grown crystals of +-ZrP-Na (at 20 000 X magnification). The particles are small and have a broad size range (from 0.1 to 1 mm) and an irregular shape. The lack of a clearly defined morphology correlates with the low crystallinity of the compounds. The XRD powder patterns of t,&ZrP-Naand +ZrP-K are identical to those belonging to the compounds prepared via partial hydrothermal decomposition of cw-ZrPand described in our recent paper [ I 11, The XRD powder patterns of bl/-ZrAs-Na %nd+ZrAs-K having a first X-ray reflection at 15.3 and 15.0 A, respectively, are presented in Fig. 2. The layered zirconium phosphates and arsenates are stable both in acid and alkaline solutions. In acid media they could be easily converted to the proton phase by exhaustive treatment with 0.5-2 M HCl or HNO,. Characterization of the proton phase +-ZrAs-H will be reported separately. The IR spectra of $-ZrAs-K and J/-ZrAs-Na are shown in Fig. 3. The adsorption bands in the 84CL1020 cm-’ region are assigned
I
El
ldeg)
Fig. 2. The XRD powder patterns of +ZrAs-Na
(a) and t,!+ZrAs-K (b)
decrease of the alkalinity of the reaction mixture (in the range of pH 11-14) do not result in a substantial improvement in the crystallinity. Additionally, ‘in the case of the use of NH,OH, as the source of alkali, (CI-ZrPand ICI_ZrAs samples
I
I
2800
I
I
I
1600 Wavenumber
Fig. 3. The IR spectra of $-ZrAs-Na
I
800 (cm ‘1 (a) and $-ZrAs-K
(b)
208
A. Clear$eld et al. /Inorganic Chemistry Communications I (1998) 206-208
to symmetric and antisymmetric stretching modes of As-O bonds in the AsO, group [ 121. The bands in the 500-700 cm- ’region are connected with Zr-0 orl and Zr-O-As bond vibrations. The broad bands in the OH stretching regions (1625-1635 and 3400-3500 cm-‘) arise from surface and interlayer water. The presence of ammonium ion in +-ZrAsNH, manifests itself by bands at 1412 and 3 195 cm- ’. To summarize, a new synthetic route for the preparation of zirconium phosphates and arsenates, possessing a new I,/+ type layered structure, is reported.
References [ I] A. Clearfield (Ed.), Inorganic Ion Exchange Materials, CRC Press, Boca Raton, PL, 1982.
[21 G. Alberti, in: P.A. Williams, M.J. Hudson (Eds.), Recent Developments in Ion Exchange, Elsevier, London, 1987. r31 A. Clearfield, in: D.L. Cocke, A. Clearfield (Eds.), Design of New Materials, Plenum, New York, 1987. I41 G. Alberti, M. Casciola, U. Costantino, R. Viviani, Adv. Mater. 8 (1996) 291. [51 A. Clearfield, J.A. Stynes, J. Inorg. Nucl. Chem. 26 (1964) 117. 161 A. Clearfield, R.H. Blessing, J.A. Stynes, J. Inorg. Nucl. Chem. 30 (1968) 2249. r71 A. Clearfield, G.D. Smith, Inorg. Chem. 8 (1969) 431. 181 J.M. Troup, A. Clearfield, Inorg. Chem. 16 ( 1977) 3311. PI A.N. Christensen, E.K. Anderson, LG. Anderson, G. Alberti, M. Nielson, MS. Lehmann, Acta Chem, Stand. 44 ( 1990) 865. 1101D.M. Poojaq,B. Shpeizer, A. Clearheld, J. Chem. Soc.,DaltonTrans., (1995) 111. [Ill AI. Bortun, L.N. Bortun, A. Cleariield, Solvent Extr. Ion Exch. 15 (1997) 305. [I21 N.G. Chemorukov, LA. Korshunov, I.M. Zhuk, Russ. J. Inorg.Chem. 27 (1982) 1728.