Structural incorporation of titanium and/or aluminum in layered silicate magadiite through direct syntheses

https://doi.org/10.1016/j.matchemphys.2012.05.072Get rights and content

Abstract

Synthesized inorganic layered magadiite containing structurally incorporated titanium and aluminum was obtained through hydrothermal procedures. The effects associated with reaction time and amount of metal used in the crystallization process yielded mostly pure and crystalline samples with 1.0% of aluminum after 36 h at 423 K. Amounts up to 4.0 and 2.0% for aluminum and titanium were successfully incorporated in the magadiite structure without co-crystallization of other phases. A higher amount of metal source or longer crystallization times led to formation of crystobalite and trydimite phases, detected by X-ray diffraction (XRD) and scanning electron microscopies. Metal incorporation slightly improved the thermal resistance of the precursor layered magadiite. Replacement of both atoms in the silicon network was examined by spectroscopy analysis. The changes in tetrahedral-oxygen-tetrahedral structural shape vibrations caused the appearance of the Ti–O–Si band at 960 cm−1. Nuclear magnetic resonance in the solid state demonstrated tandem octahedral and tetrahedral aluminum sites. Another structural feature related to titanium incorporation was observed through diffuse reflectance with UV–Vis and X-ray photoelectron spectroscopies, which distinguish crystalline and amorphous TiO2 and titanium incorporated into the silica network. Metal quantification by energy dispersive spectroscopy and X-ray fluorescence (XRF) was also followed with multivariate analysis, including principal component analysis (PCA) and partial least squares (PLS). The PCA methodology procedure clearly gives information to separate sample groups, in agreement with XRD results, which becomes a valuable feature obtained for the first time for these kinds of materials.

Highlights

► Well-crystallized magadiite containing structural aluminum and titanium were hydrothermically synthesized. ► Systematical studies on crystallization times and metal amount. ► Use of multivariate analyses methods for improving synthetic data.

Introduction

Crystalline metalosilicate materials have many different applications in sorption and catalysis, mainly when the precursor silicate combines other metals in a silicon oxide structure, to yield products that enhance involvement in several applications, not only from the scientific but also from the technological point of view. The high degree of improvement comes from the self-organized structured material, in which the attached layers have inserted metals with introduction of active centers, producing, for example, selective catalytic properties [1], [2], [3], [4].

Depending on the metal and silica source and the synthetic methodology used, a great variety of structures can be obtained, with many different properties and, consequently, many potential applications [5], [6], [7]. So, these new materials can be designed for specific purposes, such as contaminant degradation or sorption from aqueous solutions and also catalytic applications, which is an important feature for this kind of material, concerning their environmental and economic relevance [1], [2], [3], [8].

Among many possible inorganic structures, synthetic layered materials are of particular interest, owing to their properties, including thermal and mechanical stabilities and swellability in polar solvents. Other advantages associated with these synthetic materials over natural ones are high purity, homogeneity and controlled textural properties [9], [10].

Magadiite, a crystalline hydrated lamellar silicate with Na2Si14O29.9H2O composition occurs naturally [11] and was successfully synthesized in laboratory a half century ago [12], but its self-organized structure has not yet been completely solved [13]. This material is an important scientific and technological interest, due to properties related to ionic exchange, sorption, lamellar swelling etc [14]. The isomorphic substitution of silicon by a metal provides measurable changes in the silicate's properties [15] and the distribution of the metals is very important for several applications [16]. Layered hydrated silicates were also used as reactants in the synthesis of zeolites by recrystallization processes, as in the transformation of kanemite into beta zeolite with various aluminum concentrations [17]. On the other hand, titanosilicate layered materials such as JDF-L1 and AM-4 have good performance for actinide removal in salt solutions [18] and for catalytic oxidation [19].

Other investigations in the same direction applied layered silicate materials to yield zeolites and zeotypes [20], [21]. Also, some metalosilicates were directly synthesized with isomorphic substitution methodology [22], [23]. The importance of this approach is to obtain zeolite crystals with unusual morphologies, some of them displaying better access to the internal parts and, consequently, more effective catalytic sites. Surprisingly, in some cases, the layered materials themselves present even better catalytic properties than the corresponding analogous zeotypes [23].

In attempting to optimize materials for some applications and also to build a complete series of properties map for each condition, a large number of synthetic samples are normally required. From many characterization techniques there are information not easily detected by usual data treatments. To better interpret the multivariate approaches are powerful tools when associated with other kinds of characterization and technical analysis in many fields, such as food sciences, analytical chemistry, biology etc [24], [25], [26]. On the other hand, material science seems to be a forsaken area concerning the association of these results with multivariate analysis methods as there are only rare publications that apply this kind of procedure [27].

The present investigation deals with the synthesis of magadiite derivatives containing titanium and/or aluminum atoms in the crystalline network through a very simple route, without template, using a systematic study. The main focus is related to the short time of crystallization at 423 K, for 18–72 h, and the amount of metal source. The new layered compounds obtained from this original and simple synthetic procedure have been characterized with many techniques and their physicochemical properties are also discussed. The structural features were supported by chemometric analysis from X-ray diffraction and fluorescence data. To our knowledgement this is the first study associating these characterization techniques, applying the PCA method, for materials science.

Section snippets

Syntheses

Magadiite in the sodium form was synthesized by reacting silica in alkaline conditions by the hydrothermal procedure [14]. Briefly, a stirred suspension of silica gel (Aldrich) (8.0 g, 0.13 mol) and sodium hydroxide (2.4 g, 0.060 mol) in 54.0 cm3 (3.0 mol) of water was allowed to react under static conditions at 423 K for 18 up to 72 h in a Teflon-lined stainless steel autoclave. The solid (Na-mag) obtained was washed with water to remove the excess of base and air-dried at room temperature.

The

Structural features

The slow addition rate of reagents is an important feature to improve silicate crystallization. The resulting apparent material consisted of the magadiite phase formed in good yields. However, sometimes fragile monoliths were obtained. This type of irregular crystallization is associated with the short hydrolysis time of titanium isopropoxide under basic conditions [28]. Due to this behavior, a careful and slow addition is required to obtain a pure magadiite phase with titanium incorporated

Conclusions

The set of data supplied for the diverse analyses for magadiite samples demonstrates that the isomorphic substitution of silicon of well-structured magadiite by titanium and aluminum can be carried out. However, when higher titanium contents are used, the same success was not observed. A crystallization kinetics study demonstrated that phase transitions, amorphous, magadiite and more stable thermodynamic phases, such as trydimite and crystobalite and mixtures of them, can be formed. Metal

Acknowledgments

The authors are indebted to CAPES, FAPESP and CNPq for fellowships and financial support, and also to LME-LNLS for TEM measurements.

References (41)

  • T. Selvam et al.

    Microporous Mesoporous Mater.

    (2003)
  • C.S. Cundy et al.

    Microporous Mesoporous Mater.

    (2005)
  • S. Takagi et al.

    J. Photochem. Photobiol. C: Photochem. Rev.

    (2006)
  • G. Pál-Borbely et al.

    Stud. Surf. Sci. Catal.

    (1995)
  • S. Wold et al.

    Chemometrics Int. Lab. Sys.

    (1987)
  • R.S. Freire et al.

    Anal. Chim. Acta

    (2003)
  • G.C. Petrucelli et al.

    Thermochim. Acta

    (2006)
  • D. Pan et al.

    Mater. Lett.

    (2010)
  • O.A. Kholdeeva et al.

    Catal. Today

    (2004)
  • F. Kooli et al.

    J. Phys. Chem. Solids

    (2006)
  • R.A. Sheldon et al.

    Acc. Chem. Res.

    (1998)
  • J.J. Chambers et al.

    J. Appl. Phys.

    (2001)
  • M.A. Melo et al.

    Dalton Trans.

    (2010)
  • M.G. da Fonseca et al.

    J. Mater. Chem.

    (2000)
  • A. Corma et al.

    J. Am. Chem. Soc.

    (2000)
  • M. Polverejan et al.

    Chem. Mater.

    (2002)
  • M. Ritala et al.

    Science

    (2000)
  • C.S. Cundy et al.

    Chem. Rev.

    (2003)
  • Y. Fukushima et al.

    Bull. Chem. Soc. Jpn.

    (1996)
  • J. Gallégo et al.

    New J. Chem.

    (2008)
  • Cited by (16)

    • Comparison of the hydrothermal syntheses of Sn-magadiite using Na<inf>2</inf>SnO<inf>3</inf> and SnCl<inf>4</inf>·5H<inf>2</inf>O as the precursors

      2019, Applied Clay Science
      Citation Excerpt :

      The absorption spectra of the samples synthesized in this study in the mid-infrared region (Fig. 6) reveals that, in structural terms, magadiite belongs to the spatial group C2h and has a monoclinic Bravais lattice with the Si, O and Sn atoms organized in an infinitely long planar zigzag chain that is described by the operations of symmetry E, C2 and σh (Miecznikowski and Hanuza, 1985; Garcés et al., 1988; Oliveira et al., 2015). The main absorption bands observed in the spectra (Fig. 6) are highlighted in Table 3 with their assignments according to the literature (Jacobs et al., 1981; Jansen et al., 1984; Szostak et al., 1987; Garcés et al., 1988; Ko et al., 1999; Moura et al., 2011; Pires et al., 2012; Supronowicz et al., 2012; Chen et al., 2014; Wang et al., 2017b). The spectra presented in Fig. 6 are similar to those recorded for magadiites modified with different metal sources (Ko et al., 1999; Moura et al., 2011; Pires et al., 2012; Supronowicz et al., 2012; Chen et al., 2014; Oliveira et al., 2015; Wang et al., 2017b).

    • Understanding the interactions between ranitidine and magadiite: Influence of the interlayer cation

      2019, Chemosphere
      Citation Excerpt :

      TEM images (Fig. SM10) were obtained for samples of K-magadiite before and after ranitidine adsorption. The micrographs show a layered structure, characteristic of magadiite, where clear and dark lines can be observed that represent the interlayer spaces and the individual layers (Ma et al., 2015; Pires et al., 2012). After drug sorption, the basal spaces were approximately 1.51 and 1.58 nm for K-mag and K-mag-R, respectively, almost similar to those determined based on their X-ray diffraction data.

    • Aluminum doped mesoporous silica SBA-15 for the removal of remazol yellow dye from water

      2016, Microporous and Mesoporous Materials
      Citation Excerpt :

      Commercial zeolites with unique surface and pore properties have been extensively investigated for sorbing dissolved pollutants from liquid phase [13]. This inorganic material and its derivatives have been investigated in a series of processes, demonstrating the effectiveness for dyes sorption [14]. The same property can be evidenced for mesoporous silica materials such as SBA-15 and MCM-41 [15,16].

    • Catalytic performance of kenyaite and magadiite lamellar silicates for the production of α,β-unsaturated esters

      2015, Chemical Engineering Journal
      Citation Excerpt :

      Also, the nature of the active site for enhancing catalyst stability over the lamellar silicates is not reported in the literature. Synthesis of kenyaite and magadiite lamellar silicates was based on the classical hydrothermal method [19,20], which was modified in the preparation of trivalent cations-containing lamellar silicates. In a typical synthesis of magadiite, about 10 g of silica gel (0.16 mol, Aldrich, Particle size range: 35–75 μm/200–425 mesh possessing 98% of purity) was dissolved in a 1.0 mol L−1 of sodium hydroxide solution (0.060 mol, Impex) under continuous stirring for 40 min to form a white suspension.

    View all citing articles on Scopus
    View full text