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Geopolymers Using Rice Husk Silica and Metakaolin Derivatives; Preparation and Their Characteristics  [PDF]
Francisco J. López, Satoshi Sugita, Motohiro Tagaya, Takaomi Kobayashi
Journal of Materials Science and Chemical Engineering (MSCE) , 2014, DOI: 10.4236/msce.2014.25006
Abstract:

The effect of the amorphous silica derived from biomass rice husk (RH) in the alkaline activating solution on the properties was investigated in geopolymerization process, when metakaolin was used as the aluminum source from metakaolin (MK). With changing a molar ratio of SiO2/Al2O3 = 3.0 and 10, the curing in the preparation of geopolymers was carried out at 85°C, 100°C and 200°C. Viscoelastic properties of the geopolymer pastes including SiO2 and Al2O3 components suggested that the alkaline activation was found in higher RH silica source. The mineralogical and microstructural characteristics of the cured products were evaluated to be amorphous aluminosilicate.

Compressive Strength of Metakaolin-Based Geopolymers: Influence of KOH Concentration, Temperature, Time and Relative Humidity  [PDF]
Tania Ariadna García-Mejía, Ma. de Lourdes Chávez-García
Materials Sciences and Applications (MSA) , 2016, DOI: 10.4236/msa.2016.711060
Abstract: The influence of KOH concentration (8 and 12 M) and curing conditions as temperature (40 and 60), time (7 and 28 days) and relative humidity (85% and 95% RH), on compressive strength of metakaolin-based geopolymers (MK-based GP) was evaluated. Derived from the experimental design technique, and using a factorial design 2K with two replications in the center point, eighteen experiments were conducted. The results reveal that the best performance conditions of geopolymerization to develop a higher compressive strength of 20 MPa are 12 M KOH to 60 and 85% RH at 28 curing days. With these conditions, the value of relative humidity of 85%, promotes high strength compact samples, and a maximum of 42 MPa at 90 days. The results of significant, compressive design of GP showed that KOH concentration and curing relative humidity were the most important factors, followed by curing time and temperature. The GP were characterized by XRD, and their evolution on compression strength was followed by SEM.
Separation and Recovery of Tetramethyl Ammonium Hydroxide with Zeolitic Adsorbents  [PDF]
Nishihama, S.,Takatori, K.,Yoshizuka, K.
Ion Exchange Letters , 2010,
Abstract: Separation and recovery of tetramethyl ammonium hydroxide (TMAH) has been investigated, employing several zeolites as adsorbents. Zeolite X, prepared by using TMAH as a structure directing agent, possesses highest adsorption ability among the adsorbents investigated in the present work, which corresponds to the specific surface area and pore volume of the zeolite. The adsorption amount of TMAH with the zeolitic adsorbents increases with increase in pH value in the aqueous solution, indicating the adsorption progresses via cation exchange mechanism. The chromatographic operation is finally conducted, using granulated zeolitic adsorbents to prevent from the pressure-drop, and the quantitative adsorption-elution processing of TMAH can be achieved.
Separation of precious metals using selective mesoporous adsorbents
Koon Fung Lam,Chi Mei Fong,King Lun Yeung
Gold Bulletin , 2007, DOI: 10.1007/BF03215580
Abstract: The mesoporous NH2-MCM-41 adsorbent prepared by grafting aminopropyls on MCM-41 is selective towards gold and palladium adsorptions and can separate these precious metals from complex solutions containing other metal ions such as cobalt, nickel, copper and zinc. Adsorption is rapid and the adsorbent’s capacity for gold is better or comparable to most carbonaceous adsorbents including activated carbons. Furthermore, NH2-MCM-41 can separate palladium from gold solution at pH1.0 with excellent selectivity and capacity. Thus, it is possible to design a two steps separation process for the separation of palladium and then gold from the complex solution. A simple acid wash was sufficient to recover the adsorbed palladium and gold as concentrated, high purity (i.e., > 95%) metal salt solutions and the regenerated adsorbent was reused without lost of performance.
Yielding and flow of foamed metakaolin pastes  [PDF]
Lucie Ducloué,Olivier Pitois,Laurent Tocquer,Julie Goyon,Guillaume Ovarlez
Physics , 2015,
Abstract: Metakaolin is a broadly used industrial raw material, with applications in the production of ceramics and geopolymers, and the partial replacement of Portland cement. The early stages of the manufacturing of some of these materials require the preparation and processing of a foamed metakaolin-based slurry. In this study, we propose to investigate the rheology of a foamed metakaolin-based fresh paste by performing well-controlled experiments. We work with a non-reactive metakaolin paste containing surfactant, in which we disperse bubbles of known radius at a chosen volume fraction. We perform rheometry measurements to characterize the minimum stress required for the foamed materials to flow (yield stress), and the dissipation occurring during flow. We show that the yield stress of the foamed samples is equal to the one of the metakaolin paste, and that dissipation during flow increases quadratically with the bubble volume fraction. Comparison with yielding and flow of model foamed yield stress fluids allows us to understand these results in terms of coupling between the bubbles' surface tension and the metakaolin paste's rheology.
Comparison of Fire Resistant Geopolymers for Passive Fire Protection of Concrete Tunnel Linings
Konstantinos Sakkas, D. Panias, P. Nomikos, A. Sofianos
Open Access Library Journal (OALib Journal) , 2017, DOI: 10.4236/oalib.1103327
Abstract:
Fire resistant geopolymers are developed and the performance under thermal loading is examined and compared in this paper. The geopolymers were prepared by mixing the solid phase, metallurgical slag and metakaolin with a highly alkaline potassium hydroxide aqueous phase in order to create a paste that was subsequently cured at 70℃ for a certain period of time. The developed materials were tested for the mechanical, physical and thermal properties. The behaviour of the geopolymers upon exposure on fire was studied following the EFNARC guidelines for testing of passive fire protection for concrete tunnels linings. The geopolymers were subjected to the most severe fire scenario, the Rijks Water Staat (RWS) temperature-time curve. Both geopolymers appeared great behaviour after the test reaching temperature lower than the RWS test requirement, proving the ability of both materials to work successfully as an efficient thermal barrier. Thus, the concrete slab protected by the geopolymers did not appear any form of spalling or degradation of its compressive strength.
Synthesis of Geopolymers Using Local Resources for Construction and Water Purification  [PDF]
Arwa Hamaideh, Bassam Al-Qarallah, Moshrik R. Hamdi, Saida Ali Abu Mallouh, Juma’a Khalil Al-Kafawein, Mazen Alshaaer
Journal of Water Resource and Protection (JWARP) , 2014, DOI: 10.4236/jwarp.2014.65049
Abstract:

Large deposits of impure kaolins exist in Jordan and many parts of the world; geoplymers can reduce environmental impacts and have multi-application in many fields, such as water purification, waste treatment, fire proof construction, etc. The aim of this research is to investigate the use of alkali activated zeolitic tuff and low purity metakaolin as precursors for the production of functional geoplymers exhibiting proper mechanical properties and high potential for water storage and decontamination of polluted solutions. The results confirmed that this type of geopolymers showed superior mechanical characteristics and higher adsorption capacity towards heavy metals such as Cu(II) ions, which was similar to natural zeolite. X-ray diffraction analysis showed that phillipsite, a major zeolite mineral, disappeared upon geopolymerization, while scanning electron microscopy analysis showed that geopolymers exhibit a porous matrix of nano-particles. The geopolymers have also displayed high compressive strength and tensile bending strength of about 7.8 MPa and 45 MPa respectively, compared to reference geopolymers. This functional-geopolymers indicate that they are efficient, cost effective and have a potential for number of applications including construction, water storage and wastewater treatment.

Optical Response of Metakaolin after Ultraviolet and High Energy Electron Exposure  [PDF]
B. T. Cesul,S. Mall,L. Matson
Journal of Materials , 2014, DOI: 10.1155/2014/623832
Abstract: Metakaolin, which is part of a class of inorganic polymers called geopolymers, is being tested currently for its use as a lightweight mirror material in spacecraft applications. Metakaolin, as with most geopolymers, has the advantages of low initial coefficient of thermal expansion, easy preparation at room temperature and pressure, and high specific strength. Even though metakaolin has been known as a structural material for millennia, it has not been properly vetted for use as a material in spacecraft applications, especially with respect to exposure to its environments. This research highlights one particular aspect of response to the space environment; that is, how do the optical properties of metakaolin change after subjugation to bombardment by ultraviolet and high energy electron radiation? These two radiation sources are common in low earth orbit and a primary cause of degradation of organic polymers in space. Photospectroscopic analysis showed that ultraviolet in combination with high energy electrons causes changes in the metakaolin which need to be accounted for due to their potential impacts on the thermal management of a spacecraft and during application in composite mirror structures. 1. Introduction The primary choice of mirror material for spacecraft imaging optics, since the beginning of the space age, has been monolithic glass. Monolithic glass mirrors have enabled spacecraft designers to achieve mirror diameters of over 1?m, and they are well understood in terms of mechanical and thermal performance as monolithic glass variants have been one of the first man-made construction materials [1]. However, material performance requirements for the future space mirrors for advanced imaging missions necessitate a lower areal density than glass with similar if not superior mechanical strength. Additionally, any material chosen must also be able to withstand the unique environment of low earth orbit, namely the near-vacuum conditions, radiation environment and interaction with atomic oxygen. The space environment poses unique hazards for materials. There is a specific concern with any material, including geopolymers, and it is about the behavior under the radiation environment encountered in orbit. Previous investigations, both on the ground and in-flight experiments, have shown that significant degradation of the organic polymer strength occurs due to the increased cross-linking of polymer networks after absorbing the radiation emitted from the sun or deep space. The typical radiation environment includes exposure to ultraviolet and gamma
Separation of Sensitized and Non-Sensitized RBCs: Sephadex-Based Cell-Affinity Adsorbents  [PDF]
Jingchun Liu, Yan Wang, Fuping Liu
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0045583
Abstract: Introduction In transfusion medicine, antibodies that cause RBCs positive DATs, may interfere with patients' phenotyping. Traditionally, these antibodies were removed using various antibody elution methodologies. However, the elution agents and conditions used have been only partially successful; and no one method is superior. The purpose of this study was to develop a general and efficient method to separate non-sensitized from sensitized RBCs using Sephadex-based cell-affinity adsorbents. Methods First, we coupled Sephadex support with Staphylococcal Protein G (SpG) with or without NHS. Then we simulated clinical conditions by mixing differe∏nt ratios of sensitized and non-sensitized RBCs in vitro. Sensitized cells were prepared by mixing antibody with corresponding antigen-positive RBCs. Finally, we checked the sensitization status of absorbed RBCs after absorption with modified Sephadex support. Results The number of sensitized RBCs bound to Sephadex-based cell-affinity adsorbents is approximately 5×108 RBCs/mL support. Activated Sephadex could separate sensitized from non-sensitized RBCs. Conclusion Sephadex-based cell-affinity adsorbents with an NHS spacer arm have bigger capacity for binding RBCs than unmodified Sephadex. The Sephadex-based cell-affinity adsorbents readily separate non-sensitized RBCs from sensitized RBCs, thus providing a new strategy to type the blood for transfused patients.
Thermal treatment of kaolin clay to obtain metakaolin
Ili? Biljana R.,Mitrovi? Aleksandra A.,Mili?i? Ljiljana R.
Hemijska Industrija , 2010, DOI: 10.2298/hemind100322014i
Abstract: The metakaolin was produced by thermal treatment (calcination) of the starting high-quality kaolin clay from Serbia. The optimal calcination parameters, for which nearly complete dehydroxylation of the material was achieved, are: temperature 650°C and heating time of 90 min. The conversion of the kaolinite to metakaolin was confirmed by XRD and IR analyses of the starting and thermally treated kaolin samples. The pozzolanic activity was determined by Chapelle test. The obtained value 0.65 g Ca(OH)2/g of metakaolin indicates that produced metakaolin may be used as supplementary cementitious material.
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