scholarly journals Acid and Thermal Treatment of Alkali-Activated Zeolite Foams

Minerals ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 719 ◽  
Author(s):  
Zdeněk Tišler ◽  
Kateřina Hrachovcová ◽  
Eliška Svobodová ◽  
Jan Šafář ◽  
Lenka Pelíšková
Keyword(s):  
Natural Zeolite ◽  
Potassium Hydroxide ◽  
Building Materials ◽  
Acid Leaching ◽  
Textural Properties ◽  
Acid Properties ◽  
Mechanical And Structural Properties ◽  
H2o2 Solution ◽  
Post Synthesis ◽  
Alkali Activated

The foamed alkali-activated zeolite materials have been studied primarily in terms of mechanical and structural properties as potential substitutes for concrete and other building materials. However, they also have interesting textural and acid properties that make them much more useful, especially in the chemical industry. The aim of the study is to map in detail the influence of post-synthesis modifications of alkali-activated natural zeolite foams on their chemical, mechanical, and textural properties for possible use in catalytic and adsorption applications. Alkali-activated natural zeolite foam pellets were prepared by activation with mixed potassium hydroxide and sodium silicate activator and foamed using H2O2 solution. The foam pellets were post-synthetic modified by leaching with mineral and organic acids and calcination. The properties of the modified materials were characterised on the basis of XRF, XRD, N2 physisorption, DRIFT, SEM, NH3-TPD analyses, and the strength measurements. Our data showed that the basic clinoptilolite structure remains unchanged in the material which is stable up to 600 °C after acid leaching. In two-step leaching, the specific surface area increases to 350 m2/g and the leaching process allows the acid properties of the materials to be varied.

scholarly journals Modified Alkali Activated Zeolite Foams with Improved Textural and Mechanical Properties

Minerals ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 483 ◽  
Author(s):  
Kateřina Hrachovcová ◽  
Zdeněk Tišler ◽  
Eliška Svobodová ◽  
Jan Šafář
Keyword(s):  
Natural Zeolite ◽  
Chemical Properties ◽  
Acid Leaching ◽  
Earth Metal ◽  
Partial Replacement ◽  
Alkali Activation ◽  
Natural Zeolites ◽  
Modified Zeolite ◽  
Potential Applicability ◽  
Alkali Activated

Natural zeolites are crystalline hydrated alkali metal and alkaline earth metal aluminosilicates with unique ion-exchange and sorption properties. The exceptional structure of pores gives natural zeolites several application possibilities, especially for water treatment and construction. For a wider use of natural zeolites, such as catalysis, properties—especially chemical, textural, and mechanical—need to be modified. In this study, the basic natural zeolite foam was synthesized by alkali activation of natural zeolite with an activator (KOH + Na2SiO3) and foamed by hydrogen peroxide solution. Other foams were prepared by a partial replacement of the natural zeolite with CaO, MgO, and metakaolin (MK) and alkali activated and foamed in the same manner as the basic natural zeolite foam. Other properties of the foams were modified by acid leaching. The aim of the study was to compare the basic alkali activated zeolite foam with the CaO, MgO, and MK modified zeolite foams and determine the effect of the CaO, MgO, and MK modification and the subsequent leaching of the alkali activated zeolite foams on the textural, mechanical, and chemical properties. Properties of alkali activated zeolite foams were determined by Hg porosimetry, N2 physisorption, NH3-TPD, XRF, XRD, and strength analyses. From the data, it is apparent that all modified samples have an increase of pore volume in the mesoporous region and the partial replacement by MgO or CaO significantly increased surface area up to 288.2 m2/g while increasing the strength several times. The obtained data showed an improvement in properties and extension of the potential applicability of modified zeolite foams in the chemical industry, especially for catalytic and sorption applications.

scholarly journals Influence of the Addition of Blast Furnace Slag to Alkali-Activated Mixtures Based on Natural Zeolites

Minerals ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 1307
Author(s):  
Kateřina Strejcová ◽  
Zdeněk Tišler ◽  
Nikita Sharkov ◽  
Martina Michálková ◽  
Kateřina Peroutková ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Blast Furnace ◽  
Chemical Industry ◽  
Blast Furnace Slag ◽  
Acid Leaching ◽  
Textural Properties ◽  
Natural Zeolites ◽  
Subsequent Modification ◽  
Furnace Slag ◽  
Alkali Activated

This study focuses on a comparison of alkali-activated materials based on natural zeolites without and with the addition of blast furnace slag and their subsequent modification by acid leaching. The addition of slag to alkali-activated mixtures is generally used to increase the strength. The subsequent modification of its chemical, textural and mechanical properties by acid leaching makes this material usable in other industries, especially in the chemical industry. This study aimed to examine the influence of the addition of blast furnace slag to alkali-activated mixtures based on natural zeolites and observe the effect of subsequent acid leaching on the chemical, textural and mechanical properties and CO2 adsorption capacity of these materials. The modification of alkali-activated materials was carried out by acid leaching using 0.1 M HCl and then using 3 M HCl. The properties of these materials were determined using N2 physisorption, Hg porosimetry, XRF, XRD, DRIFT, TGA and strength measurements. The results showed that the addition of blast furnace slag significantly increased the cutting-edge strength of the obtained materials and affected the textural properties, especially in leached samples. The presence of blast furnace slag generated a higher proportion of mesopores, which are attributed to the presence of the calcium silicate hydrate (C–S–H) phase and are easily removed by leaching, as shown by the XRF results. The obtained data showed an improvement in properties and extension of the potential applicability of these materials in the chemical industry, especially for catalytic and adsorption applications.

Production of Porous Materials by Dealumination of Alumina-Rich Zeolites

1994 ◽  
Vol 371 ◽  
Author(s):  
R. Le Van Mao ◽  
G. Denes ◽  
N.T.C. Vo ◽  
J.A. Lavigne ◽  
S.T. Le
Keyword(s):  
Comparative Study ◽  
Pore Size Distribution ◽  
Mesoporous Materials ◽  
Acid Leaching ◽  
Textural Properties ◽  
Zeolite A ◽  
New Materials ◽  
Ammonium Hexafluorosilicate ◽  
Void Volumes ◽  
Exchange Properties

AbstractA comparative study of chemical and textural properties for materials obtained by three different methods of dealumination of alumina-rich parent Ca-A zeolite showed that the method using ammonium hexafluorosilicate (AFS) resulted in the most interesting developments of mesoporous materials, with much higher void volumes and cation exchange properties than obtained by acid leaching or hydrothermal treatment. AFS treatment on both the Na and Ca forms of zeolite A resulted in materials with 12 nm sized mesopores, whereas smaller mesopores of about 4 nm were obtained when using the higher Si/Al ratio parent zeolite Na-X. Pore size distribution profiles obtained for these new materials are fairly narrow, indicating homogeneous mesopore sized solids.

scholarly journals Statistical Approach for Water Glass Precursor Preparation from Bamboo Leaf Silica

2019 ◽  
Vol 22 (2) ◽  
pp. 52-57 ◽  
Author(s):  
Silviana Silviana ◽  
Bakti Jos ◽  
Herry Santosa ◽  
Siswo Sumardiono
Keyword(s):  
Sodium Hydroxide ◽  
Water Glass ◽  
Potassium Hydroxide ◽  
Combustion Process ◽  
Acid Leaching ◽  
Extraction Process ◽  
Silica Content ◽  
Silica Concentration ◽  
Pre Treatment ◽  
Alkali Hydroxide

The bamboo leaf consists of high silica content. In this study, the bamboo silica was utilized as water glass. Water glass can also be used as eco-friendly precursors for the preparation of silica aerogel. The extraction process of silica from bamboo leaf have been carried out through acid leaching and combustion process at 750°C based on thermal gravimetry analysis. This paper is aimed to assess the effect of two types of alkali hydroxide and concentrations producing water glass of bamboo leaf silica. The result was analyzed by using a 22-factorial design with six replications. The alkali hydroxide types were sodium hydroxide and potassium hydroxide with a concentration of 4 M and 6 M, respectively. The study was executed in several steps, i.e. pre-treatment of bamboo leaf, leaching process, combustion, purification of bamboo leaf silica and synthesis of water glass. The optimum condition of water glass products was obtained at silica concentration of 41.08 ppm and density of 1.23 g/L for potassium hydroxide, while at 40.15 ppm and 1.30 g/L for sodium hydroxide. ANOVA analysis resulted in a significant effect for type of hydroxide and concentration releasing model for silica concentration response. This study also characterized the silica structure and composition by instrumentation analysis for silica solid obtained from optimum water glass condition with potassium hydroxide. It can be denoted the physical behavior of silica solid from water glass by potassium hydroxide did not differ from previous research of water glass by sodium hydroxide.

Clinoptilolite foams prepared by alkali activation of natural zeolite and their post-synthesis modifications

2019 ◽  
Vol 282 ◽  
pp. 169-178 ◽  
Author(s):  
Zdenek Tisler ◽  
Jan Horacek ◽  
Jan Safar ◽  
Romana Velvarska ◽  
Lenka Peliskova ◽  
...  
Keyword(s):  
Natural Zeolite ◽  
Alkali Activation ◽  
Post Synthesis

scholarly journals Geopolymer Based on Mechanically Activated Air-cooled Blast Furnace Slag

Materials ◽  
2020 ◽  
Vol 13 (5) ◽  
pp. 1134 ◽  
Author(s):  
Ilda Tole ◽  
Magdalena Rajczakowska ◽  
Abeer Humad ◽  
Ankit Kothari ◽  
Andrzej Cwirzen
Keyword(s):  
Compressive Strength ◽  
Blast Furnace ◽  
Portland Cement ◽  
Sodium Silicate ◽  
Blast Furnace Slag ◽  
Ball Mill ◽  
Efficient Solution ◽  
Building Materials ◽  
Furnace Slag ◽  
Alkali Activated

An efficient solution to increase the sustainability of building materials is to replace Portland cement with alkali-activated materials (AAM). Precursors for those systems are often based on water-cooled ground granulated blast furnace slags (GGBFS). Quenching of blast furnace slag can be done also by air but in that case, the final product is crystalline and with a very low reactivity. The present study aimed to evaluate the cementitious properties of a mechanically activated (MCA) air-cooled blast furnace slag (ACBFS) used as a precursor in sodium silicate alkali-activated systems. The unreactive ACBFS was processed in a planetary ball mill and its cementing performances were compared with an alkali-activated water-cooled GGBFS. Mixes based on mechanically activated ACBFS reached the 7-days compressive strength of 35 MPa and the 28-days compressive strength 45 MPa. The GGBFS-based samples showed generally higher compressive strength values.

scholarly journals Cobalt Based Catalysts on Alkali-Activated Zeolite Foams for N2O Decomposition

Catalysts ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1398
Author(s):  
Zdeněk Tišler ◽  
Anna Klegová ◽  
Eliška Svobodová ◽  
Jan Šafář ◽  
Kateřina Strejcová ◽  
...  
Keyword(s):  
Ion Exchange ◽  
Alkali Metals ◽  
Catalyst Activity ◽  
Acid Leaching ◽  
N2o Decomposition ◽  
Cobalt Catalysts ◽  
Alkali Activation ◽  
Incipient Wetness Impregnation ◽  
Exchange Method ◽  
Alkali Activated

In this work, we studied the effect of alkali-activated zeolite foams modifications on properties and catalytic activity of cobalt phases in the process of catalytic decomposition of N2O. The zeolite foam supports were prepared by alkali activation of natural zeolite followed by acid leaching and ion exchange. The cobalt catalysts were synthesised by a different deposition technique (direct ion exchange (DIE) and incipient wetness impregnation (IWI) method of cobalt on zeolite foams. For comparison, catalysts on selected supports were prepared and the properties of all were compared in catalytic tests in the pellet form and as crushed catalysts to determine the effect of internal diffusion. The catalysts and supports were in detail characterized by a variety of techniques. The catalyst activity strongly depended on the structure of support and synthesis procedure of a cobalt catalyst. Ion exchange method provided active phase with higher surface areas and sites with better reducibility, both of these factors contributed to higher N2O conversions of more than 80% at 450 °C. A large influence can also be attributed to the presence of alkali metals, in particular, potassium, which resulted in a modification of electronic and acid base properties of the cobalt oxide phase on the catalyst surface. The promotional effect of potassium is better reducibility of cobalt species.

Use of Glassy Slag from Biomass Combustion in the Building Industry – Coarse Aggregate

2015 ◽  
Vol 1122 ◽  
pp. 219-224 ◽  
Author(s):  
Filip Khestl ◽  
Veronika Šulková ◽  
Pavel Mec
Keyword(s):  
Soil Temperature ◽  
Building Materials ◽  
Coarse Aggregate ◽  
Waste Product ◽  
Biomass Combustion ◽  
Building Industry ◽  
Basic Characteristics ◽  
Alkali Activated

The work deals with possibilities using of glassy slag produced during the combustion of biomass in construction. This is a waste product with glass characteristic, which may also contain ash and other pollutants. This waste is significantly different according to the used types of biomass, soil, temperature and time of combustion. Its structure is mostly porous and glassy. Building materials in which may be applied are cementitious or alkali-activated composites in which can appear in due to its nature as a filler or binder. In the paper the basic characteristics with the focus on use of this slag as a coarse aggregate were examined.

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