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 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.

scholarly journals Incorporation of Alkali-Activated Municipal Solid Waste Incinerator Bottom Ash in Mortar and Concrete: A Critical Review

Materials ◽  
2020 ◽  
Vol 13 (15) ◽  
pp. 3428 ◽  
Author(s):  
Rawaz Kurda ◽  
Rui Vasco Silva ◽  
Jorge de Brito
Keyword(s):  
Literature Review ◽  
Municipal Solid Waste ◽  
Solid Waste ◽  
Bottom Ash ◽  
Curing Temperature ◽  
Partial Replacement ◽  
Alkali Activation ◽  
Waste Incinerator ◽  
Alkaline Activator ◽  
Alkali Activated

In the light of one of the most common waste management issues in urban areas, namely the elimination of municipal solid waste (MSW; about 486 kg of the waste per capita were generated in the EU in 2017), this study discusses one technique as an outlet in the construction industry for the by-product of the waste’s incineration in energy recovery facilities (i.e., MSW incinerator bottom ash—MIBA). There have been some investigations on the use of MIBA as partial replacement of cement to be used in cementitious composites, such as concrete and mortars. However, the waste’s incorporation ratio is limited since further products of hydration may not be produced after a given replacement level and can lead to an unsustainable decline in performance. In order to maximize the incorporation of MIBA, some research studies have been conducted on the alkali activation of the waste as precursor. Thus, this study presents an extensive literature review of the most relevant investigations on the matter to understand the material’s applicability in construction. It analyses the performance of the alkali-activated MIBA as paste, mortar, and concrete from different perspectives. This literature review was made using search engines of several databases. In each database, the same search options were repeated using combinations of various representative keywords. Furthermore, several boundaries were made to find the most relevant studies for further inspection. The main findings of this review have shown that the chemical composition and reactivity of MIBA vary considerably, which may compromise performance comparison, standardization and commercialization. There are several factors that affect the performance of the material that need to be considered, e.g., type and content of precursor, alkaline activator, curing temperature and time, liquid to solid ratio, among others. MIBA-based alkali-activated materials (AAM) can be produced with a very wide range of compressive strength (0.3–160 MPa). The main factor affecting the performance of this precursor is the existence of metallic aluminum (Al), which leads to damaging expansive reactions and an increase in porosity due to hydrogen gas generation stemming from the reaction with the alkaline activator. Several approaches have been proposed to eliminate this issue. The most effective solution was found to be the removal of Al by means of eddy current electromagnetic separation.

scholarly journals Factors Affecting Alkali Activation of Laterite Acid Leaching Residues

Environments ◽  
2021 ◽  
Vol 8 (1) ◽  
pp. 4
Author(s):  
Konstantinos Komnitsas ◽  
Georgios Bartzas ◽  
Vasiliki Karmali ◽  
Evangelos Petrakis
Keyword(s):  
Compressive Strength ◽  
Environmental Sustainability ◽  
Structural Integrity ◽  
Acid Leaching ◽  
Sodium Silicate Solution ◽  
Curing Temperature ◽  
Alkali Activation ◽  
Curing Time ◽  
Synthesis Conditions ◽  
Alkali Activated

In this experimental study, the alkali activation of acid leaching residues using a mixture of sodium hydroxide (NaOH) and alkaline sodium silicate solution (Na2SiO3) as activators is investigated. The residues were also calcined at 800 and 1000 °C for 2 h or mixed with metakaolin (MK) in order to increase their reactivity. The effect of several parameters, namely the H2O/Na2O and SiO2/Na2O ratios present in the activating solution, the pre–curing time (4–24 h), the curing temperature (40–80 °C), the curing time (24 or 48 h), and the ageing period (7–28 days) on the properties of the produced alkali activated materials (AAMs), including compressive strength, porosity, water absorption, and density, was explored. Analytical techniques, namely X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and elemental mapping analysis were used for the identification of the morphology and structure of the final products. The experimental results show that the laterite acid leaching residues cannot be alkali activated in an unaltered state, and the compressive strength of the produced AAMs barely reaches 1.4 MPa, while the mixing of the residues with 10 wt% metakaolin results in noticeably higher compressive strength (41 MPa). Moreover, the calcination of residues at 800 and 1000 °C has practically no beneficial effect on alkali activation. Alkali activated materials produced under the optimum synthesis conditions were subjected to high temperature firing for 2 h and immersed in distilled water or acidic solution (1 mol L−1 HCl) for 7 and 30 days in order to assess their structural integrity under different environmental conditions. This study explores the potential of alkali activation of laterite leaching residues amended with the addition of metakaolin for the production of AAMS that can be used as binders or in several construction applications in order to enable their valorization and also improve the environmental sustainability of the metallurgical sector.

scholarly journals The Compressive Strength and Microstructure of Alkali-Activated Binary Cements Developed by Combining Ceramic Sanitaryware with Fly Ash or Blast Furnace Slag

Minerals ◽  
2018 ◽  
Vol 8 (8) ◽  
pp. 337 ◽  
Author(s):  
Juan Cosa ◽  
Lourdes Soriano ◽  
María Borrachero ◽  
Lucía Reig ◽  
Jordi Payá ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Blast Furnace ◽  
Fly Ash ◽  
Blast Furnace Slag ◽  
Calcium Content ◽  
Partial Replacement ◽  
Alkali Activation ◽  
High Calcium ◽  
Furnace Slag ◽  
Alkali Activated

The properties of a binder developed by the alkali-activation of a single waste material can improve when it is blended with different industrial by-products. This research aimed to investigate the influence of blast furnace slag (BFS) and fly ash (FA) (0–50 wt %) on the microstructure and compressive strength of alkali-activated ceramic sanitaryware (CSW). 4 wt % Ca(OH)2 was added to the CSW/FA blended samples and, given the high calcium content of BFS, the influence of BFS was analyzed with and without adding Ca(OH)2. Mortars were used to assess the compressive strength of the blended cements, and their microstructure was investigated in pastes by X-ray diffraction, thermogravimetry, and field emission scanning electron microscopy. All the samples were cured at 20 °C for 28 and 90 days and at 65 °C for 7 days. The results show that the partial replacement of CSW with BFS or FA allowed CSW to be activated at 20 °C. The CSW/BFS systems exhibited better mechanical properties than the CSW/FA blended mortars, so that maximum strength values of 54.3 MPa and 29.4 MPa were obtained in the samples prepared with 50 wt % BFS and FA, respectively, cured at 20 °C for 90 days.

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 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.

Sorption of Uranium(6+) and Neptunium(5+) by Surfactant-Modified:Natural Zeolites

1999 ◽  
Vol 556 ◽  
Author(s):  
James D. Prikryl ◽  
Roberto T. Pabalan
Keyword(s):  
Anion Exchange ◽  
Cationic Surfactant ◽  
Natural Zeolite ◽  
Natural Zeolites ◽  
Radionuclide Concentration ◽  
Modified Zeolite ◽  
Surfactant Modification ◽  
Naci Concentration ◽  
Carbonate Complexes

AbstractExperiments were conducted to determine the ability of surfactant-modification to enhance the ability of natural zeolites to sorb U(6+) and Np(5+). Natural zeolite material, comprised mainly of clinoptilolite and treated with the cationic surfactant exadecyltrimethylammonium-bromi(le (IDTMA), was reacted with U(6+) and Np(5+) solutions open to the atmosphere and having a range of radionuclide concentration, pH, and NaCI concentration. The results indicate surfactantmodification of the zeolite enhances its ability to sorb U(6+), particularly at pHs greater than six where U(6+) sorption on unmodified zeolite is typically low due to formation of anionic U(6+) aqueous carbonate complexes. In contrast, there is little enhancement of Np(5+) sorption onto surfactant-modified zeolite. The presence of chloride anions in solution makes surfactantmodification less effective. The enhanced sorption of U(6+) is interpreted to be due to anion exchange with counterions on the external portion of a surfactant bilayer or admicelles.

ION Exchange Characterisation of Modified Zeolite

1992 ◽  
Vol 26 (9-11) ◽  
pp. 2269-2272 ◽  
Author(s):  
Š Cerjan-Stefanovic ◽  
M. Kaštelan-Macan ◽  
T. Filipan
Keyword(s):  
Drinking Water ◽  
Ion Exchange ◽  
Anion Exchange ◽  
Natural Zeolite ◽  
Deionized Water ◽  
Isomorphous Substitution ◽  
Waste Waters ◽  
Modified Zeolite ◽  
Water Drinking

Isomorphous substitution of phosphorus into a natural zeolite affords the possibility to change the overall framework charge from negative to positive. The substances so created should be used for purification of waste waters. The work describes the preparation of phosphated zeolite, their characterisation and examples of their anion exchange of NO3 on observed in deionized water, drinking water and in the solution containing varying amounts of nitrate.

scholarly journals Grinding Kinetics of Slag and Effect of Final Particle Size on the Compressive Strength of Alkali Activated Materials

Minerals ◽  
2019 ◽  
Vol 9 (11) ◽  
pp. 714 ◽  
Author(s):  
Evangelos Petrakis ◽  
Vasiliki Karmali ◽  
Georgios Bartzas ◽  
Konstantinos Komnitsas
Keyword(s):  
Particle Size ◽  
Compressive Strength ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Ageing Time ◽  
Reduction Rate ◽  
Curing Temperature ◽  
Alkali Activation ◽  
Final Particle ◽  
Alkali Activated

This study aims to model grinding of a Polish ferronickel slag and evaluate the particle size distributions (PSDs) of the products obtained after different grinding times. Then, selected products were alkali activated in order to investigate the effect of particle size on the compressive strength of the produced alkali activated materials (AAMs). Other parameters affecting alkali activation, i.e., temperature, curing, and ageing time were also examined. Among the different mathematical models used to simulate the particle size distribution, Rosin–Rammler (RR) was found to be the most suitable. When piecewise regression analysis was applied to experimental data it was found that the particle size distribution of the slag products exhibits multifractal character. In addition, grinding of slag exhibits non-first-order behavior and the reduction rate of each size is time dependent. The grinding rate and consequently the grinding efficiency increases when the particle size increases, but drops sharply near zero after prolonged grinding periods. Regarding alkali activation, it is deduced that among the parameters studied, particle size (and the respective specific surface area) of the raw slag product and curing temperature have the most noticeable impact on the compressive strength of the produced AAMs.

Formation and some chemical properties of of alkaline-earth metal monouranates

1979 ◽  
Vol 41 (12) ◽  
pp. 1729-1735 ◽  
Author(s):  
Hiroaki Tagawa ◽  
Takeo Fujino ◽  
Toshiyuki Yamashita
Keyword(s):  
Alkaline Earth ◽  
Chemical Properties ◽  
Earth Metal ◽  
Alkaline Earth Metal
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