Aluminosilicate Inorganic Polymers Research Articles

Long-term durability of discarded cork-based composites obtained by geopolymerization

Geopolymers are amorphous aluminosilicate inorganic polymers synthesized by alkaline activation characterized by a lower carbon footprint, greater durability, and excellent mechanical properties compared to traditional concrete, making them promising building materials for sustainable construction. To develop sustainable lightweight geopolymer-based building materials useful as fire resistant thermal insulation materials, we added 5 and 10 wt% of discarded cork dust, a readily available industrial by-product, to metakaolin before and after the alkaline activation with sodium hydroxide 8 M and sodium silicate solutions. We followed the chemical, microstructural, antibacterial, and physical properties of the resulting composites for up to 90 days in order to monitor their long-term durability. The presence of cork does not interfere with the geopolymerization process and in fact reduces the density of the composites to values around 2.5 g/cm3, especially when added after alkaline activation. The composites resulted in chemically stable matrices (less than 10 ppm of cations release) and filler (no hazardous compounds released) with a bacterial viability of around 80%. This study provides valuable insights into the tailoring of discarded cork-based composites obtained by geopolymerization with a porosity between 32 and 48% and a mechanical resistance to compression from 15 to 5 MPa, respectively, suggesting their potential as durable interior panels with low environmental impact and desirable performance.

Adsorptive removal of Cu(II) by fly ash based geopolymer material

Geopolymer are aluminosilicate inorganic polymer synthesized by polymerization of aluminosilicate with alkaline solutions. These materials possess high surface area hence promising adsorbent. In this paper fly ash and rice husk-based geopolymer type hybrid mass is applied for remediation of Cu(II) ions. Various adsorptive parameters for example contact /reaction time, effluent metal ions concentration, dose of hybrid mass, pH and operating temperature are optimized and fixed for getting maximum removal of aqueous Cu(II) ions. Equilibrium isotherm and kinetic studies revealed that the isotherm data were best described by Langmuir adsorption isotherm and the rate of adsorption follows the pseudo second-order. Thermodynamic studies carried out by applying Van’t Hoff equation, which revealed that the process was exothermic and spontaneous. Results indicate encouraging performance of hybrid mass towards removal of Cu(II) ions.

Conversion of palm oil fuel ash (POFA) into foamy geopolymer for lightweight building material application by aluminum powder addition

Palm Oil Fuel Ash (POFA) is produced from the burning of palm oil solid waste biomass. POFA is abundant in Indonesia considering that Indonesia is one of the world’s largest producers of Crude Palm Oil (CPO) and has the largest palm oil plantation. The main content of POFA is SiO2 around 60%, Al2O3 around 3-10% and CaO around 5-15% so that POFA has the potential to be developed as aluminosilicate inorganic polymers. The high SiO2/Al2O3 ratio in POFA needs to be reduced for the formation of Si-O-Al chains in geopolymers. Therefore, two stages of research were carried out. Preliminary research was conducted to obtain optimum Solid/Liquid ratio. Aluminum powder was then added with certain variations to get a certain SiO2/Al2O3 ratio as well as a foaming agent so that the product can later be used as a porous building material. The preliminary results showed that the optimum Solid/Liquid ratio obtained was 0.83. The addition of aluminum powder was optimum at 2% w/w with a compressive strength of 5.4233 MPa, a density of 1339.2175 kg/m3, and a thermal conductivity of 0.6233 Watt/m°K. This geopolymer product can be categorized as a lightweight building material with criteria: a compressive strength of 0.5-10 MPa, densities between 600-1800 Kg/m3, and a thermal conductivity of 0.1-0.7 Watt/m°K which can be used as panels in buildings, casting walls, and ornaments in parks.

Development of novel and green NiFe2O4/geopolymer nanocatalyst based on bentonite for synthesis of imidazole heterocycles by ultrasonic irradiations

Geopolymers as aluminosilicate inorganic polymers and eco-friendly building materials which can be used as substrate for different kinds of composite. In this research, according to the fabrication of geopolymer based on bentonite as a substrate and embedment of NiFe2O4 nanoparticles in the construction of this polymer, the synthesis of a new magnetic nanocomposite (NiFe2O4/geopolymer) was investigated for the first time. In order to describe its chemistry and morphology features, different analyses such as Fourier transform infrared spectroscopy, field-emission scanning electron microscopy and transmission electron microscopy images, Brunauer–Emmet–Teller adsorption–desorption isotherm, X-ray diffraction pattern, energy-dispersive X-ray analysis, thermogravimetric analysis, and vibrating-sample magnetometer analysis were used. The application of this novel nanocatalyst was studied for one-pot three-component condensation reaction of substituted imidazole derivatives by accelerated ultrasonic irradiations. Compared to the other conventional catalysts which were used for the synthesis of imidazole derivatives, the green synthesis method for fabrication of this heterogeneous and magnetic nanocatalyst, its high thermal stability, being eco-friendly, noticeable efficiency and easy reusability have become privileges to be superior.

Geopolymer Ceramic as Piezoelectric Materials: A Review

Diverse application for geopolymer so called inorganic polymer have been expanded as potential to continue growing at a realistic rate where the properties, processing tolerance and economical are comparable with the existing materials. An aluminosilicate inorganic polymer can be produced at low temperature under highly alkali conditions from a solid aluminosilicate and an alkali silicate solution. The conversion of amorphous to semi-crystalline behaviour of geopolymer into crystalline phases upon heating make the method be an alternate way in producing ceramic materials. For another application related to high temperature packaging and enclosure of electronical devices, piezoelectric behavior turn out to be important properties to the geopolymer ceramic materials. This paper summarize the review on the important research findings on the basic geopolymer systems, current knowledge of geopolymer ceramic, and outline potential piezoelectric effect on ceramic materials.

Synthesis and characterization of a new class of geopolymer binder utilizing ferrochrome ash (FCA) for sustainable industrial waste management

Sustainable use of industrial wastes for the production of new age eco-friendly construction materials can effectively solve the growing environmental concern over landfills and also provide an integrative industrial waste management strategy. Geopolymers are comparatively a new class of aluminosilicate inorganic polymer which has gained wide recognition due to its remarkable physicochemical and mechanical properties. Various industrial wastes such as fly ash, slag, rice husk ash, ferrochrome ash, etc. rich in alumina and silica can serve as suitable precursors for the production of geopolymer binders. This paper presents the experimental investigations on the utilization of ferrochrome ash (FCA), and waste from the ferrochrome industry as a primary precursor having considerable amounts of alumina, silica, magnesium oxide, potassium oxide for preparation of geopolymer concrete having partial replacements of ground granulated blast furnace slag and lime. The fresh and hardened geopolymer concrete properties: workability and compressive strength are thoroughly investigated. The particle size distribution, the chemical composition, mineralogy, microstructure of binder particles were analysed with advanced analytical techniques such as XRF, PSA, XRD, SEM/EDS. The results of this study not only suggest the effective utilization of ferrochrome ash for the synthesis of a new class of geopolymer binders but also provide a sustainable route for the management of ferrochrome waste currently generated in various countries worldwide.

Structural and electrical properties of geopolymer materials based on different precursors (kaolin, bentonite and diatomite)

Geopolymers (GP) were successfully synthesized from metabentonite (MB), metadiatomite (MD) and metakaolinite (MK). Characterization of their phase structure and microstructure was performed by XRD, FTIR, SEM/EDX methods. A SEM micrograph of GPMD shows a homogeneous surface with some longitudinal cavities in the gel, and it is significantly different from the micrographs of the other two geopolymer samples, GPMB and GPMK. A considerable amount of unreacted particles, as well as the presence of pores in the geopolymer matrix of GPMK and GPMD, indicate an incomplete reaction in the system. Aluminosilicate inorganic polymers, geopolymers, are quasi solid electrolytes which possess a high electrical conductivity at room temperature in relation to materials of similar chemical composition. The highest conductivity was found for the sample obtained from GPMK, amounting to 2.14 × 10–2 Ω–1cm–1at 700 ºC. The corresponding activation energies of conductivity for this sample amounted to 0.33 eV in the temperature range of 500–700 ºC. The geopolymer synthesized from metakaolin has good ionic conductivity values, which recommends it for use as an alternative material for an SOFC (Solid Oxide Fuel Cell).

Enhancing the selectivity of polar hydrophilic analytes with a low concentration of barium ions in the mobile phase using geopolymers and silica supports

Charged analytes such as organic sulfonic acids, sulfates, carboxylates, and phosphates are often analyzed by hydrophilic interaction liquid chromatography (HILIC). In many cases, these analytes do not show any selectivity and elute near the dead time using the conventional acetonitrile-ammonium acetate buffers. In this work, we introduce a powerful selectivity enhancing technique by using a trace amount of Ba2+ ion in the mobile phase as a general approach for HILIC with UV–Vis detection. Silica and a newly developed material called geopolymers are used as stationary phases. Geopolymers are X-ray amorphous aluminosilicate inorganic polymers with cation exchange properties. Barium exchanged geopolymers (Ba-NM-GP) are synthesized from metakaolin based geopolymer. Thorough characterization of Ba-NM-GP is reported using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), Brunauer-Emmett-Teller (BET) surface area analyzer and laser diffraction particle size distribution analyzer for the determination of their shape, size, porosity, surface area and particle size distribution respectively. It is demonstrated that in the absence of Ba2+, baseline separations of sulfonates, carboxylates, and phosphates is not possible, whereas, in the presence of Ba2+ in the mobile phase, these analytes are easily separated. Barium perchlorate is suggested as an additive for it is UV transparent, and it has practically an unlimited solubility in acetonitrile.

Synthesis, characterization and optimization of new adsorbent materials based on industrial discharges for the decontamination of liquid effluents

Abstract The aluminosilicate inorganic polymers, in addition to the interest they present as a cement whose production does not generate large quantities of greenhouse gases, offer great possibilities of application in the protection of the environment in according to their methods of synthesis. The purpose of this work is to valorize industrial waste, especially fly ash to synthesize a material adsorbing heavy metals from wastewater. The synthesis of materials (geopolymer) based on fly ash at different curing temperatures (20, 35, 50, 50, 60, 70 and 80 °C) has been carried out in order to optimize the retention capacity which depends on the intimate structure of the material. It is a geopolymer foam whose porosity varies according to the quantity of hydrogen peroxide introduced during synthesis and the cooking temperature. The fly ash and geopolymers obtained were characterized using several techniques; X-ray diffraction (XRD), scanning electron microscopy (SEM-EDX) and Fourier-transform infrared spectroscopy (FTIR). Then a study of the adsorption of heavy metals (Cd as an example) by these geopolymers was performed. This study it has demonstrated the effectiveness of this material which has adsorption capacities of around 280 mg/g, which is 1.5–10 times higher than the values in the literature.

The Effects of Replacement Metakaolin with Diatomite in Geopolymer Materials

Geopolymers are aluminosilicate inorganic polymers. In this study, the effects of replacement metakaolin with diatomite in geopolymer materials were investigated. The geopolymer materials were prepared by leaching diatomite (from Lampang province) and metakaolin (from Ranong province) with alkaline activator solutions. The fresh slurry was cast into plastic molds with a cubic shape and then cured at room temperatures. Effects of ratios between diatomite and metakaolin were investigated. Furthermore, influences of curing time on the properties of the studied samples were also determined. Many techniques for material characterization such as XRF, XRD, and SEM were employed in this work. The mechanical property of geopolymer compressive strength was tested after curing. It was found that compressive strength of the samples increased with increased amounts of diatomite.

New phosphors synthesised by ion exchange of a metakaolin-based geopolymer

Abstract A geopolymer prepared from dehydroxylated kaolinite-type clay was used as a host for trivalent rare earth ions to produce new photoluminescent materials. Sm3+ and Eu3+ ions were individually incorporated into the geopolymer host by ion exchange, partially replacing the charge-balancing K+ ions. The resulting materials were characterised by XRD, SEM/EDS, 27Al and 29Si MAS NMR and PIXE, and their luminescence behaviour was determined by photoluminescence spectroscopy. In addition to the characteristic photoluminescence of the Sm3+ and Eu3+ ions, the geopolymer host exhibited broad-band photoluminescence peaking at 440 nm under 372 nm excitation. The use of the clay-based geopolymer host permitted a higher concentration of rare earth ions to be incorporated compared with a previously reported chemosynthetic aluminosilicate inorganic polymer host, resulting in rare earth photoluminescence of increased intensity. A further advantage of the clay-based geopolymer phosphor is its ease of synthesis and cost-effectiveness compared with the chemosynthetic aluminosilicate inorganic polymer host.

New phosphors based on the reduction of Eu(III) to Eu(II) in ion-exchanged aluminosilicate and gallium silicate inorganic polymers

Novel blue-emitting phosphors based on Eu2+ ions dispersed within chemosynthetic aluminosilicate and gallium silicate inorganic polymer (geopolymer) hosts were prepared by heat treatment of Eu3+-exchanged inorganic polymers in reducing conditions and investigated using photoluminescence spectroscopy, 29Si, 27Al and 71Ga MAS NMR spectroscopy, XRD, and XPS. Eu2+ photoluminescence could be distinguished from the photoluminescence of the inorganic polymer host after heating at ≥ 400°C in the case of the aluminosilicate inorganic polymer and ≥ 600°C in the case of the gallium silicate inorganic polymer and became more intense as the reduction temperature was increased up to 1000°C. The gallium silicate-based phosphors heated at ≥ 900°C contained small amounts of crystalline KGaSi2O6 or β-Ga2O3, but the X-ray amorphous structure of the inorganic polymer was retained. After heating at 1000°C, the Eu2+ photoluminescence intensity was substantially more intense for the aluminosilicate phosphor, but the shape of the excitation and emission spectra of the aluminosilicate and gallium silicate phosphors were similar, with a broad emission band centred at 440–475nm when excited at 240–400nm. This band shifted to longer wavelengths as the ion exchange solution concentration was increased from 0.001M to 0.03M.

Green Concrete Made From Iron Slag Waste

Synthesis of green concrete has been carried out by using iron slag waste of PT Inti Jaya Steel Jrakah, Semarang. Geopolimer (green concrete) is an aluminosilicate inorganic polymer with chain Si-O-Al that can be synthesized from material rich in silica and alumina with sodium hydroxide as an activator. Iron slag chemical content analysis indicated that this material is a part of pozzolan material with each individual components weight as follow: SiO2: 4.55%, Al2O3: 2.54%, CaO: 11.43%, Fe2O3: 77.10%, MnO2: 1.43 and other minerals: 4.07%. The mole ratio of SiO2/Al2O3 of iron slag waste of PT Inti Jaya Steel Jrakah, Semarang is quite high at 3.05. Although the ratio is high, it is still can be synthesized using an activator solution of NaOH and increasing the drying time to 3 days and 24 hours of curing time at 60°C temperature to help the process of water molecule condensation in the geopolymerisation process. Characterized concrete (green concrete) that has been formed shows that the maximum compressive power can be achieved at composition ratio of Iron slag/ Na-silicate /NaOH /H2O of 55/10/4/8, with compressive power of 11.254 MPa. © 2015 JNSMR UIN Walisongo. All rights reserved.

Aluminosilicate inorganic polymers (geopolymers) containing rare earth ions: a new class of photoluminescent materials

Chemosynthetic aluminosilicate inorganic polymers exhibiting photoluminescent properties were prepared by introducing rare earth activator ions (Sm3+ or Eu3+) into the aluminosilicate structure by ion exchange. Under ~400 nm excitation, the materials showed the characteristic 4f–4f emission peaks of Sm3+ and Eu3+ ions and also broad emission bands in the blue and green regions that were also exhibited by the unexchanged inorganic polymer host. The host and the corresponding phosphors were characterised by XRD, 27Al and 29Si MAS NMR, PIXE and XPS. The photoluminescence intensities of the aluminosilicate inorganic polymers containing Sm3+ and Eu3+ were considerably enhanced by heating in air at >800 °C. The best phosphors were heated at 1200 °C, forming a mixture of crystalline KAlSi2O6 (leucite) and the residual aluminosilicate inorganic polymer.

Corrosion Studies of Fly Ash and Fly Ash-Slag Based Geopolymer

This paper presents the results of corrosion studies between Fly Ash Geopolymer (FG) paste and Fly Ash-Slag Geopolymer (FSG) paste. Geopolymer was made from aluminosilicate inorganic polymers mixed with the alkaline activator in order to reduce the carbon dioxide (CO2) to the ecosystem. Samples then were cured at 60ºC for 24 hours in the oven. Reinforcement bar is placed at the center of the paste. The samples were examined after 7, 14 and 28 days in terms of Open Circuit Potential (OCP) test, phase analysis and morphology analysis. The potential values regarding OCP test for FSG paste from 7 days until 28 days are 0.464 V, 0.474 V and 0.498 V more positive than FG paste which the potential values are 0.087 V, 0.133 V and 0.206 V respectively. From the Pourbaix diagram, all the potential values for FG paste and FSG paste were located in the same Fe2O3, passivity region. Passive layer which is the oxide form exists in this region to protect the reinforcement bar from corrosion agents. It can be proved from phase analysis results which iron oxide hydroxide (FeOOH), hematite (Fe2O3) and magnetite (Fe3O4) peaks exist. The differences of morphological structures of these pastes were observed by Scanning Electron Microscope (SEM). It shows that FSG paste had good corrosion resistance and low corrosion rate compared to FG paste.

Facile synthesis of new hierarchical aluminosilicate inorganic polymer solid acids and their catalytic performance in alkylation reactions

This paper reports the synthesis of hierarchical aluminosilicate inorganic polymers (also known as geopolymers) containing both Bronsted and Lewis acid sites that function as a new class of heterogeneous solid acid catalysts. The geopolymers were synthesised from a naturally occurring clay mineral by an energy-efficiently and ecologically friendly process. Their catalytic performance was evaluated in a model liquid phase Friedel-Crafts alkylation of relatively large substituted benzenes (alkylation of toluene, anisole, p-xylene and mesitylene with benzyl chloride). The influence of the geopolymer starting composition on the acidity and porosity of the synthesised catalysts was studied and the impact of post-synthetic demetallation on their catalytic performance was investigated. The geopolymer-based catalysts achieved high catalytic activity which was superior to HY zeolite under identical reaction conditions. These results suggest that geopolymers have considerable potential as cost efficient, readily synthesised and environmentally friendly heterogeneous solid catalysts for fine chemical applications.

Porous aluminosilicate inorganic polymers (geopolymers): a new class of environmentally benign heterogeneous solid acid catalysts

Aluminosilicate inorganic polymers (geopolymers) were developed as a new class of cost-efficient, environmentally friendly, solid acid catalysts and their performance evaluated in a model liquid-phase Beckmann rearrangement reaction (cyclohexanone oxime to ε-caprolactam). The active sites were generated within the structure of the geopolymers by ion-exchange with NH4+ followed by thermal treatment. The effect of varying the starting composition on the textural and acidic properties of the geopolymer catalysts was studied and its influence on the catalytic activity was investigated. Catalytic performance was significantly improved by the use of post-synthetic treatments. No significant decrease in the yield of ε-caprolactam after recycling for five times suggesting that geopolymer-based catalysts are advantageous over supported catalysts which often lose their catalytic activity due to leaching of the active sites from the support. The catalytic activities obtained in this study are comparable, and sometimes superior, to other solid catalysts suggesting that geopolymers have a great potential as environmentally benign heterogeneous catalysts.

Geopolymer/PEG Hybrid Materials Synthesis and Investigation of the Polymer Influence on Microstructure and Mechanical Behavior

Geopolymers are aluminosilicate inorganic polymers, obtained from the alkali activation of powders containing SiO2+Al2O3>80wt%, mainly proposed as environmentally friendly building materials. In this work, metakaolin-based geopolymers have been prepared and a water-soluble polymer, polyethylene glycol (PEG), has been added in different percentages to obtain organic-inorganic hybrid geopolymers. The influence of both the polymer amount and aging time on the structure and the mechanical behavior of the materials were investigated. FTIR spectroscopy allowed us to follow the evolution of the aluminosilicate framework during the geopolymerization process. This analysis revealed that PEG leads to a network which is rich in Al-O-Si bonds and forms H-bonds with the inorganic phase. SEM microscope showed that the two phases are interpenetrated on micrometric scales. Traction and bending tests have been carried out on appropriate samples to investigate the mechanical behavior of the obtained hybrids, showing that both PEG content and aging time affect the material behavior.

Synthesis and properties of novel photoactive composites of P25 titanium dioxide and copper (I) oxide with inorganic polymers

The synthesis of novel composites of spherical Cu2O nanoparticles and P25 TiO2 with aluminosilicate inorganic polymers (geopolymers) is described and the morphology of the homogeneous oxide nanoparticle dispersion within the geopolymer matrix demonstrated by SEM/EDS and TEM. XRD and FTIR confirmed the formation of a well-reacted geopolymer matrix that was unaffected by the insertion of the Cu2O/TiO2 nanoparticles. Experiments in dark conditions and under UV irradiation showed that these materials efficiently remove a model organic pollutant (methylene blue dye) from solution by a dual process of adsorption on the geopolymer matrix, and photodecomposition of the dye without destroying the geopolymer structure. The adsorption kinetics are described by a pseudo-first-order model and Freundlich-type isotherms. Incorporation of 10wt% Cu2O/TiO2 nanoparticles into the geopolymer composites decreases their adsorption ability by blocking the active adsorption, sites, but at higher Cu2O/TiO2 concentrations, dye adsorption is facilitated, probably by expanding the geopolymer matrix structure. Under UV irradiation, the composites remove the MB dye by a combination of adsorption and photodegradation without destroying the geopolymer structure. The combination of nanosized Cu2O particles and photoreactive P25 titania in an aluminosilicate inorganic polymer matrix is a more efficient photocatalyst under UV irradiation than geopolymer composites containing either of the individual oxides alone. These new geopolymer composites show promise as ecologically-friendly materials which can efficiently remove organic pollutants from water or the atmosphere.

Optimization of Geopolymer Properties by Coating of Fly-Ash Microparticles with Nanoclays

Geopolymer binders are aluminosilicate inorganic polymers with expanding applications as construction materials. For wider industrial use of these binders, limited controls of their rheological properties and short solidification time have to be improved. A surface modification of fly ash microcores allows for better control of the geo-concrete formation. Naturally occurring nanoclays, such as halloysite nanotubes and kaolin nanoplates are cheap and abundantly available materials allowing encapsulating alumosilicate microcores with simple and scalable layer-by-layer (LbL) nanocoating technique. An electrostatic attraction drives coating of anionic nanoclays onto fly ash particles providing a potential to controllably adjust properties of geopolymer composites. LbL technique was used to modify geopolymer through nanoarchitectural formation of composite shells on ash microcores. We describe mechanical and rheological enhancement of geopolymers produced from ash microparticles coated with tubule or platy nanoclays sandwiched with polycations, and its advantages for better concrete materials.