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Material densities, total porosities, and compressive strengths of the studied alkali- activated binders (AABs).
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This work reports and describes a novel alkali-activated metakaolin as a potential binder material for the granulation of zeolites, which are widely used as CO2 adsorbents. The alkali-activated binders are zeolite-like materials, resulting in good material compatibility with zeolite-based adsorbents. A major problem during the granulation of zeolit...
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Context 1
... material densities, the total porosities, and the compressive strengths of the monolithic AABs are shown in Table 1. According to the obtained results, the material densities of the AABs ranged from 1230 up to 1535 kg/m 3 , depending on binder composition and curing conditions, which were higher than those of zeolite 4A granules with an average density of 950-1150 kg/m 3 [26]. ...Context 2
... to the obtained results, the material densities of the AABs ranged from 1230 up to 1535 kg/m 3 , depending on binder composition and curing conditions, which were higher than those of zeolite 4A granules with an average density of 950-1150 kg/m 3 [26]. As seen in Table 1, the samples of series M8 exhibited lower material densities (1230-1255 kg/m 3 ) compared to the samples of series M10 (material density: 1530-1535 kg/m 3 ), while the samples of series M6 had material densities in a range of 1285-1315 kg/m 3 . ...Context 3
... correlation is not clear, but it can be speculated that some amount of relatively small zeolite crystals (like zeolite 4A) might provide a denser AAB structure, also affecting the porosity and the compressive strength of the final product. As seen in Table 1 and Figure 1, the studied AABs had compressive strengths ranging from 9.4 to 20.8 MPa, depending on binder composition and curing conditions. Özen et al. reported that the compressive strengths of natural zeolite-based geopolymers were in a range between 6.7 and 42.0 MPa [41,42], which agrees with the experimental results presented here. ...Context 4
... since curing at RCs (RC-type) is the cheapest route and, therefore, is likely to be more beneficial in an industrial setting, the RC-type specimens were chosen for BET testing. Additionally, the total porosity (Table 1) was not strongly affected by the type of curing method but was strongly dependent on the molarity of the used alkali-activation solution. Therefore, it seems that comparing influence of alkali-activation molarity is more relevant. ...Similar publications
Nitrogen and phosphorus are commonly recognized as causing eutrophication in aquatic systems, and their transport in subsurface environments has also aroused great public attention. This research presented four natural clay minerals (NCMs) evaluated for their effectiveness of NH4⁺ and PO4³⁻ adsorption from wastewater. All the NCMs were fully charac...
Citations
... Vanadium is a redox-sensitive element that occurs in three oxidation states in the environment (+III, +IV and +V), although it usually occurs as the oxygen anion vanadium (V) under most environmental conditions [7,8]. Adsorption is a widely used and very convenient method for removing specific contaminants, especially if the adsorbent has good regenerative properties [9,10]. Extensive work has been carried out to research suitable adsorbents to remove vanadium from aqueous solutions, including chitosan, alumina, anatase, Fe 2 O 3 , LDHs and crystalline hydroxyapatite [11][12][13][14][15]. ...
A series of novel layered double hydroxides (Mg-Fe-Ti-LDHs) containing Mg2+, Fe3+ and Ti4+ were prepared. The adsorption performance of Mg-Fe-Ti-LDHs on vanadate in aqueous solution was investigated and the effects of various factors on the adsorption process were examined, including initial vanadate concentration, adsorbent dosage, contact time, solution pH and coexisting ions. A preliminary discussion of the adsorption mechanism of vanadate was also presented. Results show that the adsorption efficiency of vanadate increased with the introduction of Ti4+ into the laminate of LDHs materials. The adsorption capacity of the materials also differed for different anion intercalated layers, and the Mg-Fe-Ti-LDHs with Cl− intercalation showed higher vanadate removal compared to the CO32− intercalated layer. Furthermore, Mg-Fe-Ti-CLDH showed higher vanadate removal compared to pre-calcination. The adsorption experimental data of vanadate on Mg-Fe-Ti-LDHs were consistent with the Langmuir adsorption isotherm model and the adsorption kinetics followed a pseudo-second order kinetic model. The pH of the solution significantly affected the vanadate removal efficiency. Meanwhile, coexisting ions PO43−, SO42− and NO3− exerted a significant influence on vanadate adsorption, the magnitude of the influence was related to the valence state of the coexisting anions. The possible adsorption mechanisms can be attributed to ion exchange and layered ligand exchange processes. The good adsorption capacity of Mg-Fe-Ti-LDHs on vanadate broadens the application area of functional materials of LDHs.
... It was found that their method could accurately control the early-age phases of the metakaolin geopolymer. Apart from these studies, metakaolin geopolymer can further be applied to civil engineering works, such as a low-cost and self-bearing thermal insulating core for thermostructural sandwich panels [31], cultural heritage restoration [32], and as a potential binder for granulation zeolites [33,34]. From these applications, it can be observed that various research topics in metakaolin geopolymer are still ongoing. ...
This study proposes the use of a non-destructive testing technique, based on piezoelectric bender element tests, to determine the initial and final setting times of metakaolin geopolymer pastes. (1) Background: Metakaolin geopolymer is a new eco-friendly building material that develops strength rapidly and is high in compressive strength. (2) Methods: The initial and the final setting times were investigated via bender element and Vicat needle tests. Metakaolin powder was prepared by treating kaolin at 0, 200, 800, 1000, and 1200 °C. All metakaolin powder samples were then mixed with geopolymer solution at different mixing ratios of 0.8:1.0, 1.0:1.0, 1.2:1.0, and 1.5:1.0. The geopolymer solution was prepared by adding 10 normal concentrations of sodium hydroxide (10 N NaOH) to sodium silicate (Na2SiO3) at various solution ratios of 1.0:1.0, 1.0:1.2, 1.0:1.5, 1.0:2.0, 1.2:1.0, 1.5:1.0 and 2.0:1.0. (3) Results: The optimum temperature for treating metakaolin is established at 1000 °C, with a mixing ratio between the metakaolin powder and the geopolymer solution of 1.0:1.0, as well as a solution ratio between NaOH and Na2SiO3 of 2.0:1.0. (4) Conclusions: The use of piezoelectric bender elements to determine the initial and final setting times of metakaolin geopolymer pastes is a useful method by which to detect geopolymerization by shear wave velocity in a real-time manner. Moreover, the penetration of the Vicat apparatus can confirm the setting times at specific intervals. The relationships between the shear wave velocity and the Vicat penetration appear to be linear, with an initial setting time of 168 m/s and a final setting time of 187 m/s. Finally, the optimum metakaolin geopolymer pastes are applied to improve laterite soils, as measured by CBR tests.
... Showing common supplementary cementitious materials under scanning electron microscope (SEM) with figures from[40][41][42][43] ...
Due to constant growth of waste production, recent strategies in waste management such as circular economy promote the maximum life cycle use of materials. In construction industry where structures tend to last for decades, the use of such recycled materials can have numerous benefits including overall reduction in cost, in use of virgin materials, and in CO2 production as well as providing an opportunity for a tailored concrete with specific properties. Yet, because of the stereotypical and negative image of mechanical properties reduction, as a result of using waste materials, often their vast contribution in sustainability and durability properties are not taken into consideration. In this regard, we propose viewing waste materials as secondary raw materials that in certain regards, can provide a favorably tailored property. In this regard, the following review article first provides a short description of the most commonly used waste materials such as supplementary cemen-titious materials (fly ash, ground granulated blast furnace slag, silica fume, metakaolin, rice husk ash, municipal solid waste ash, steel slag, copper slag), ceramics from construction and demolition (glass powder, brick and tile ceramic and porcelain), and the vastly available plastic materials (polypropylene, polyethylene terephthalate, polyvinyl chloride, and rubber). Then, by reviewing a selected environmental impact (life cycle assessment), physicochemical, durability, and finally mechanical properties discuss the limitations, future projections of newer waste materials (e.g., agricultural waste) to be used and suggest potential future study in this area.
... Adsorbents can be classified as organic or inorganic. Inorganic adsorbents include ____________________________________________________________________________ 2021 / 25 1087 activated aluminum, silica gel, adsorbent clays, molecular sieves, and zeolites [6]. Organic adsorbents are activated carbon adsorbents and polymer adsorbents [7]. ...
An eco-friendly method for the synthesis of granular activated carbon was developed in this study. Two types of activated carbon and three types of activated carbon granules have been obtained using different binders, and their properties have been determined. The approach requires adding other binders and waste materials to improve the granulation of activated carbon. Activated carbon was prepared from birch wood chips. Prepared carbon was granulated with a) gas generator tar, b) phenol-formaldehyde resin, and c) polyvinyl acetate to obtain granular activated carbon. This work aims to study the possibilities of using activated carbon adsorbents for CO2 adsorption. The activated carbon produced was characterized by BET, FTIR, and SEM. The adsorption behavior on CO2 was also studied. Granular activated carbons compression strength was enough to study it in an adsorption bed, and an optimal binder was to be phenol-formaldehyde resin and polyvinyl acetate. The obtained results show that activated carbon granules are suitable for CO2 adsorption and can be used, for example, for the removal of CO2 in the biogas upgrading process. As the sustainability problems are increasing, granules from waste materials could be promising materials for further studies.
... Up to now geopolymers or alkali activated materials (AAM) are one of most promising materials [2], [3]. Traditionally, AAM are synthesized from metakaolin or fly ash based precursors which now are associated with valuable raw and secondary raw material consumption [4]- [6]. However, research continues for alternative alumina and silica sources to obtain low cost alternative binders. ...
The search for alternative alumosilicates source for production of alkali activated materials (AAM) is intensively researched. Wide spread of natural materials such as clays and waste materials are one of potential alternatives. In this research AAM was made from local waste brick made of red clay and calcined low-carbonate illite clay precursor and its properties evaluated. Waste silica gel containing amorphous silica from fertilizer production plant was proposed as additional raw material. 6 M and 7 M NaOH alkali activation solutions were used to obtain AAM. Raw materials were characterized by X-ray diffraction, laser particle size analyser, DTA/TG. Raw illite clay was calcined at a temperature of 700 to 800 °C. Waste brick was ground similar as raw clay and powder was obtained. Replacement of red clay with silica gel from 2–50 wt.% in mixture composition was evaluated. Results indicate that the most effective activator was 6 M NaOH solution and AAM with strength up to 13 MPa was obtained. Ground brick had the highest strength results and compressive strength of AAM reached 25 MPa. Silica gel in small quantities had little effect of AAM strength while significant strength reduction was observed with the increase silica gel content. The efflorescence was observed for samples with silica gel.
... During this last decade, a shift has been seen toward more research dedicated to alkaliactivated materials [1][2][3][4][5][6][7][8], because of their applications and properties. One way to utilize these kinds of materials is to use them as binders in a composition with other materials to enhance the overall properties of the composite. ...
Amajor problem in the field of adsorbents is that binders (kaolin clay, bentonite) introduced
to bind zeolites and ensure the needed mechanical strength, are not able to sorb gases like CO2 and
N2, and decrease the overall adsorption capacity. To solve this problem, one of the pathways is to
introduce a binder able to sorb such gases. Thus, in this study, the physical and mechanical properties
of a novel binder based on metakaolin and its composite with zeolite 4A in the granular form were
studied. Metakaolin was used as a precursor for alkali-activated binder, which was synthesized
using an 8M NaOH activation solution. Raw materials were characterized using granulometry, X-ray
diffraction (XRD), and differential thermal analysis (DTA); and final products were characterized
using density measurements, a compressive strength test, XRD, Brunauer–Emmett–Teller (BET)
analysis, and scanning electron microscopy (SEM). Alkali-activated metakaolin was found to be
efficient as a binding material when data for morphological properties were analyzed. A relationship
was observed—by increasing the liquid-to-solid ratio (L/S), compressive strength decreased. Zeolite
granule attrition was higher than expected: 2.42% and 4.55% for ZG-0.8, 3.64% and 5.76% for ZG-1.0,
and 2.73% and 4.85% for ZG-1.2, measured at 4 and 5 atmospheres, respectively.
... The leaching of alkalis is affected by three main factors: Chemical composition of raw materials (type of precursor and activator, alkali activator solution/solid ratio), physical properties (porosity, pore structure), and production method of AAM (curing conditions, thermal treatment, etc.) [2,5,[11][12][13]. The previous results from different studies have shown that calcined illite clay [3], biomass-fly ash [5], natural zeolite [14], glass waste and slag blend [15], and metakaolin [2,16] can be used as raw materials for production of AAM. ...
Due to the increase of water consumption, water treatment systems become more actual and innovative materials for water treatment are welcomed. Traditionally, alkalizing agents, such as lime or caustic soda, have been employed to increase the pH levels, which induce chemical clarification of wastewater. Some innovative ideas of using low-calcium, alkali-activated materials (AAM) for this purpose have been considered previously. In this study, the low-calcium, porous, alkali-activated material (pAAM) was characterized to understand the impact of the aluminum silicate source and heat treatment on basic properties for material that might be used in water treatment systems as a softener by stabilizing the pH. The studied porous alkali-activated materials may ensure stable and long-lasting (30 days) pH (pH 10.3–11.6) in water media depending on the composition and amount of activation solution used for AAM preparation. Heat treatment does not have an impact on the mineralogical composition and structural properties of the pAAM, but it does change the leaching ability of alkalis from the material structure.
... Our group has successfully produced ZSM-5 from abundant feedstock such as kaolin [13] and rice husk [14]. The zeolite that was produced from metakaolin has potential to be used as an adsorbent as reported in literature [15]. ...
A hierarchical zeolite ZSM-5 with micro and meso-pore was prepared by optimising the most affecting parameter in sequence of desilication and dealumination. The physicochemical properties of zeolite were characterised with XRD, nitrogen adsorption-desorption, FTIR and SEM. The potential of this zeolite for decolorisation of CR, RY, MB, RhB, DB-1 and DB-14 was evaluated with adsorption isotherm, thermodynamics, kinetics, and influencing parameter for adsorption. The unique modification of ZSM-5 resulted in lower crystallinity, easier porosity control, rich terminal silanol and unbridged silanol groups which assisted in higher adsorption capacity. The adsorption capacity of the optimum ZSM-5 was 323, 435, 589, 625, 61 and 244 mg/g for CR, RY, MB, RhB, DB-1 and DB-14, respectively. The dye adsorption progressed through pseudo-first-order kinetic and close to the Langmuir model. The adsorption mechanism is proposed mainly through interaction between deprotonated silanol site and the electron-rich dye site.
... Alkali activated materials have several known advantages, such as exceptional mechanical strength, acid and fire resistance, long term durability, fast setting, and low thermal conductivity. Therefore, these materials are mainly used in the construction, and thermal and heat insulation industries, but they are also used for several applications, such as catalysts and membranes [15]. ...
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.
Zeolites, a group of minerals with unique properties, have been known for more than 250 years. However, it was the development of methods for hydrothermal synthesis of zeolites and their large-scale industrial applications (oil processing, agriculture, production of detergents and building materials, water treatment processes, etc.) that made them one of the most important materials of the 20th century, with great practical and research significance. The orderly, homogeneous crystalline and porous structure of zeolites, their susceptibility to various modifications, and their useful physicochemical properties contribute to the continuous expansion of their practical applications in both large-volume processes (ion exchange, adsorption, separation of mixture components, catalysis) and specialized ones (sensors). The following review of the knowledge available in the literature on zeolites aims to present the most important information on the properties, synthesis methods, and selected applications of this group of aluminosilicates. Special attention is given to the use of zeolites in agriculture and environmental protection.
