Short communicationSynthesis of the zeolite granulate for potential sorption application
Introduction
Zeolites are tectoaluminosilicates and due to their unique physicochemical properties found numerous and important applications resulting [1]. For over 60 years, zeolites have been successfully synthesized in laboratory conditions by heating of aluminosilicate materials in the presence of alkaline solution. Type of zeolite structure that forms at given temperature depends to a large extent on the composition of the starting mixture. Industrially, zeolites are produced by hydrothermal method from colloidal silica and alkali metal silicates and aluminates in the presence of alkaline solution (usually sodium hydroxide). Less expensive methods for preparing zeolites using waste materials and natural aluminum silicate [2], [3], [4] were also developed.
In the laboratory conditions, zeolites are obtained in the form of fine, highly disperse powder, which hampers their practical application. For this reason several known methods of forming them into larger agglomerates/molding were developed. The most commonly used method is a granulation [5], [6] using a binder, usually clay [7], [8] with optional additives. The granulation is carried out by mixing zeolite with binder and water, and then the resulting pulp is formed to different shapes and dried. The second method for the production of molded zeolite is the crystallization „in situ” after formation of clay mineral. This technology involves the formation of kaolinite forms, which are treated with highly alkaline solution – by reacting, kaolinite partially crystallizes in the zeolite phase [9], [10], [11].
Analysis of the related literature [12] indicates that the granulation of zeolites gives rise to several problems. The first is low sorption capacity of the granules when compared to the starting material. Secondly, the high alkalinity of zeolite leads to the destruction or weakening strength of many common binders. Another disadvantage may be swelling under the action of moisture. In addition, the potential use of molecular sieves often requires cyclic heating in the range 350–650 °C for regeneration of an overworked material (removal of the adsorbate from the zeolite structure), i.e. the binder must be resistant to temperatures in this range.
The aim of this work is to develop hard, spherical, yet lightweight zeolite granules for sorption application. The use of expanded glass granules as starting material was assumed.
Section snippets
Experimental
The Poraver® expanded glass aggregate (grain size 0.1–2.0 mm) was used in the experiments. Grain size was in the range 0.1–2.0 mm. The chemical composition of starting material composition (determined by XRF semi-quantitative analysis; WD-XRF Axios mAX 4 kW, PANalytical) was as follows (in wt. %): SiO2–64.2%, Al2O3–4.7%, Fe2O3–0.3%, MgO–1.9%, CaO–6.9%, Na2O–20.3% and K2O–0.7%.
The synthesis was carried out by mixing 1.0 g Poraver® expanded glass aggregate with 10 ml of NaOH aqueous solution in
Results and discussion
XRD patterns of synthesis products obtained from various starting mixtures are presented in Fig. 1. Treatment of expanded glass granulate (without any addition; Fig. 1a) with NaOH solution represents the first attempt. Depending on NaOH concentration, the main products in such conditions (90 °C, 24 h) are zeolite Na-P1 and hydrosodalite. As in typical hydrothermal zeolite synthesis [14], [15], at lower analyzed NaOH concentrations zeolite Na-P1 is formed, while at higher concentration –
Conclusions
With simple synthesis, it is possible to obtain zeolite granules based on expanded glass aggregate as a starting material. Moreover, depending on the concentration of other reactants (sodium and alumina source), zeolite A, X, Na-P1 and hydrosodalite are within reach. The high cation exchange capacities of zeolitization products make it possible to use them in the treatment of various types of sewage and industrial wastes, however potential use must be also verified.
Acknowledgments
Financial support this work was provided by The National Science Centre Poland under grant no. 2016/21/D/ST8/01692 entitled “Manufacturing, modification and application of granulated zeolite sorbent”.
References (19)
- et al.
Mater. Lett.
(1983) - et al.
Fuel
(2015) - et al.
Int. J. Coal Geol.
(2002) - et al.
Int. J. Coal Geol.
(2002) - et al.
Chem. Eng. J.
(2010) - et al.
Microporous Mesoporous Mater.
(2016) Zeolite Molecular Sieves
(1974)Phys. Chem. Mater.
(2001)- et al.
Environ. Monit. Assess.
(2014)
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