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The massive amount of kaolin processing waste was daily formed. To reduce the amount of their waste deposited in landfills and to increase the value- adding of recyclable waste, this work interested to use as raw materials in the preparation of geopolymer. This paper studied the reaction mechanisms of calcined kaolin processing waste-based geopolymers in the presence of low alkali activator solution by the pressing method. The reaction mechanisms of geopolymer were measured as a function of NaOH concentration by DSC, XRD, and FTIR analysis. Furthermore, the effects of NaOH concentration and curing time on the mechanical properties and microstructure of calcined kaolin processing waste-based geopolymer were investigated. The DSC, XRD, and FTIR results indicated that the geopolymerization reaction increased with higher NaOH concentrations. Forming the geopolymer by the pressing method led to the particles being close together in a compact matrix. Subsequently, their surfaces were dissolved with NaOH solution, inducing the geopolymerization reaction. This reaction and continuous reaction resulted in the compressive strength and microstructure of the geopolymer. The compressive strengths of the geopolymer synthesized with NaOH concentration of 10 M (curing time of 7 days) and a curing time of 28 days were 26.98 MPa and 28.55 MPa, respectively, which were approximately 22.58% and 52.35% higher compared to the geopolymer synthesized with NaOH concentration of 4 M and a curing time of 1 day. The SEM micrographs of the geopolymer samples displayed more geopolymeric gel and denser matrices with increases in NaOH concentration and curing time. The nitrogen adsorption and pore volume decreased with increases in NaOH concentration and curing time. Synthesis of geopolymers using kaolin processing waste as a raw material is a value- adding and environmentally friendly process.

This paper describes a simple and effective process for fabricating geopolymer-polymer composite fiber. The fiber is synthesized by mixing geopolymer powder with Polyethersulfone (PES) – N-Methyl-2 pyrrolidone (NMP) solution and the slurry was extruded then transformed into a fiber by phase inversion method. The fiber is constructed of PES and fly ash-based geopolymer (FAG) particles with porous structure. Analysis of the pore structure of fiber revealed that BET surface area is 168.30 m2/g. In addition, the adsorption capacity of heavy metal ions on geopolymer composite fiber follows the order of Pb2+ > Cu2+ > Cd2+ > Ni2+. This work provides a convenient, low-cost and environmental friendly adsorbent for removing heavy metal ions from waste water.

Waste management and water quality are two main problems nowadays. Geopolymer material has efficiency for adsorbing the ions from wastewater. In this research, the metakaolin based geopolymer was studied and used as an adsorbent to remove heavy metal ions. Moreover, the factors which affect adsorption process of heavy metals on geopolymer materials were investigated. The kaolin as used in this research was from Thailand. The metakaolin geopolymer was synthesized by mixed raw materials with an alkaline solution. The metakaolin geopolymer was washed and sieved through 100 mesh. The produced metakaolin geopolymer powder was used as an adsorbent. The XRD results showed a highly amorphous structure in obtained metakaolin geopolymer. Moreover, the BET surface area of metakaolin and geopolymer particles were 9.83 m2/g and 20.36 m2/g, respectively. The parameters of adsorbent amount, initial pH, time of shaking, temperature and initial metal ions concentration on the removal potential of geopolymer were studied. In addition, the multi-and mono-cations solution were demonstrated to compare the efficiency of each heavy metal ions. The results showed that the amount of Pb2+, Cu2+, Cd2+, and Ni2+ions adsorbed onto metakaolin geopolymer increased with an increasing contact time, pH, temperature and amount of geopolymer. It is concluded that Pb2+, Cu2+, Cd2+, and Ni2+ions in aqueous solution are efficiently removed by metakaolin geopolymer which could be applied as a low cost and good alternative for wastewater treatment.

This work aims to evaluate the effectiveness of fly ash based geopolymer powder as an adsorbent for heavy metals in aqueous solution. The structure of synthesized geopolymer was found to be highly amorphous due to the dissolution of fly ash phase. Moreover, the fly ash geopolymer powder has higher surface area compares to original fly ash with specific surface area of 85.01 m²/g and 0.83 m2/g, respectively. For this reason, the geopolymer powder has much higher removal efficiency compared to the original fly ash powder. The removal efficiency was affected by contact time, geopolymer amount, heavy metal initial concentration, pH, and temperature. The four heavy metals were chosen (Pb2+, Cu2+, Ni2+, Cd2+) for adsorption test. The highest heavy metal removal capacity was obtained at pH 5. The geopolymer powder adsorbed metal cations in the order of Pb2+>Cu2+>Cd2+>Ni2+. In addition, Langmuir model is more suitable for fly ash geopolymer powder adsorption of heavy metal ions in aqueous solution than Freundlich model. The results showed that the fly ash geopolymer powder has high efficiency for removal metal which could be employed excellent alternative for wastewater treatment.

Basalt fiber has been used as a reinforced material in cement-based materials because it has higher mechanical strength and cheaper than common silicate based glass-fibers. However, silicate-based glass fibers have low alkali resistance especially in cement matrix composite. In this work, we studied the improvement of alkali resistance by addition of zirconium silicate (ZrSiO4) in original basalt glass composition. The batch of basalt glass with additional ZrSiO4 contents of 0.00, 2.50, 5.00, 7.50 and 10.00 wt% were melted at 1500 °C. The liquidus temperature (TL) is important in for the fiber glass manufacturing. It need to formulate glass composition which requires a lower melting temperature and is crystallization resistant. TL as a function of composition is usually determined experimentally. In this study, glassy phase was determined by X-ray Diffraction (XRD). The glass transition temperature (Tg), the crystallization temperature (Tc) and TL were analyzed by Differential Thermal Analysis (DTA). The results found that the addition of ZrSiO4 in a basalt glass batch increased Tg while Tc of each sample was closed to original basalt fiber. Moreover, the alkali resistance of these glasses increased with an increasing of ZrSiO4 content. However, excessive ZrSiO4 contents (7.50 and 10.00 wt%) resulted in crystallization of ZrO2 which separated from glassy phase.

Class C fly ash is widely used as a geopolymer raw material. It contains high calcium oxide and iron oxide resulting in a fast setting property. The influence of using kaolin and metakaolin replaced class C fly ash in geopolymer processing were investigated in term of compressive strength and setting time. Kaolin and metakaolin which calcined at different temperature of 600°C and 700°C replaced Class C fly ash between 0 to 50 wt. %. The geopolymers were prepared at constant KOH concentration as 6.0 M, K2SiO3/KOH ratio as 1.0, solid/liquid ratio as 1.5 and 7 days of curing. The compressive strength is obviously increased when fly ash was replaced with both kinds of metakaolin, although, it is inclined to decrease when replaced by kaolin. The compressive strength is increased up to 13% and 47% with the replacement by 50 wt. % of metakaolin calcined at 600°C and 700°C, respectively. On the other hand, the replacement by 50 wt. % of kaolin give the initial setting time prolonging from about 6 min to 80 min. However, the initial setting time of metakaolin calcined at 600°C and 700°C replacement is also improved to about 37 min and 20 min, respectively. These results from their difference of amorphous phase and reactivity of the replacement materials. XRD analysis reveals the combination phases of amorphous geopolymer gel that is the broad hump centered at 28 – 30° 2θ, and products from the reaction such as calcium oxide, arcanite, calcium silicate hydrate, quartz and muscovite which the two latter are from unreacted metakaolin. They are confirmed by FT-IT result and microstructure evaluation by SEM. Therefore, the partially replacement of fly ash with kaolin and metakaolin in fly ash-based geopolymer production are affected to the compressive strength and resulted to modify the setting time.

Geopolymer particles from waste coal fly ash were prepared in order to investigate adsorption process of Cadmium ions. The aim of the study is to focus on factors which affect adsorption process of heavy metals on geopolymer materials. The raw fly ash was mixed with sodium hydroxide solution and sodium silicate solution. After that geopolymer was cured at 80 °C for 24 hr. The sample was ground and washed until pH=7. The obtained geopolymer particles were dried at 60 oC. The raw materials and geopolymer were characterized. The XRD results showed a highly amorphous structure in obtained geopolymer. The major components of waste coal fly ash and synthesized geopolymer were SiO2, Al2O3, Fe2O3 and CaO. The BET surface area of fly ash and geopolymer particles were 0.83 m2/g and 85.01 m2/g, respectively. The adsorption conditions (initial concentration from 10-120 mg/L, temperature at 25-45 °C, pH of cadmium ions solution from 1-5, 0.02-0.14 g. of geopolymer and contact time for 5-180 min) were studied. From removal efficiency results, synthesized geopolymer had high removal capacity for cadmium ions (Cd2+). At pH 5 of solution, the highest Cd2+ removal capacity was obtained. In addition, the removal efficiency increases with an increasing geopolymer dosage, contact time and a decreasing of Cd2+ initial concentration. Moreover, both Langmuir and Freundlich models were investigated for studying adsorption isotherm. The result showed Langmuir model is more suitable for geopolymer adsorption of cadmium ion in aqueous solution than Freundlich model.

This project presents how steel recycling by-products employed as decorative ceramic glaze raw materials.Two steelmaking wastes were of interests: electric arc furnace dust and mill scale.EAF dust is collected from off-gas fume during melting.The dust containing zinc ferrite with some heavy metals is concerned as a toxic waste.Mill scale collected from a hot-rolled reheating furnace is iron-rich oxide and non-toxic.The as-received wastes were chemically analyzed.A mid-fired glaze, oil spot tenmoku, were carefully formulated and investigated.The work showed both wastes successfully provided the glaze with lustrous and silvery spotting effect

Objective: To investigate the flexural strength and cytotoxicity of ZCC, a resin modified zinc oxide-calcium carbonate liner prototype, compared with commercial dental liners. Materials and Methods: ZCC, Dycal, Ultra-Blend® plus (UB), and TheraCal LC® (TC) were evaluated for flexural strength. Six samples of each material were incubated in growth medium (10% fetal bovine serum supplemented DMEM) for 24 h. Primary human dental pulp cells were cultured in the conditioned medium from each sample, with growth media used as a control. Cytotoxicity was determined using an MTT assay. Data were analyzed by one-way ANOVA. The value of pppp>0.05). Conclusion: ZCC met the requirements for flexural strength per ISO 9917-2:2010(E). There was no significant difference in viability between the control and ZCC group at 24 and 48 hours.

Solid oxide fuel cell (SOFC) is an electrochemical energy conversion device which is considered as clean energy source generator with reliability and relatively inexpensive production cost. One of the most important components for planar design SOFC is the hermetic seal that prevents fuel from leaking out of between the stack of fuel cells. Glass-ceramics are attractive materials as sealing materials for this device. The expected coefficient of thermal expansion (CTE) of the glass-ceramic sealants should be between 9 and 12 x 10−6 K−1. Glass – ceramics based on åkermanite (Ca2MgSi2O7) crystalline phase were reported their high CTE value from about 10 to 11.3 x 10−6 K−1. In this study, glass compositions in the CaO-MgO-B2O3-Al2O3-SiO2 system with varying amounts of Bi2O3 from 0 to 10 wt. % were prepared by conventional melting and investigated their properties. The selected compositions were derived from ternary åkermanite–forsterite–anorthite phase diagram. Phase composition and quantitative phase analysis of glass–ceramics were examined by X-ray diffractometer. The onset of crystallization (Tx) and crystallization temperature (Tc) were measured by DTA. The thermal properties of bulk glass samples and heat treated samples at 900 oC for 2 h which were glass transition temperature (Tg), dilatometric softening temperature (Ts), and coefficient of thermal expansion (CTE) were determined by dilatometer. Furthermore, the long-term stability of their CTE was investigated. The samples were continued to soak at 800 °C for 100 h and observed their change in CTE value. The results found that the åkermanite phase tended to increase with increasing amount of Bi2O3 content.

Microwave synthesis of porous fly ash geopolymers was achieved using a household microwave oven. Fly ash paste containing SiO 2 and Al 2 O 3 component was mixed with sodium silicate (Na 2 SiO 3 ) solutions at different concentrations of sodium hydroxide (NaOH) of 2, 5, 10, and 15 M, which were used as NaOH activators of geopolymerization. The mass ratio of Na 2 SiO 3 /NaOH was fixed at 2.5 with SiO 2 /Al 2 O 3 at 2.69. After the fly ash and alkali activators were mixed for 1 min until homogeneous, the geopolymer paste was cured for 1 min using household microwave oven at different output powers of 200, 500, 700, and 850 W. Porous geopolymers were formed immediately. Micro X-ray CT and SEM results showed that the porous structure of the geopolymers was developed at higher NaOH concentrations when using 850 W power of the microwave oven. These results derive from the immediate increase of the temperature in the geopolymer paste at higher NaOH concentrations, meaning that aluminosilicate bonds formed easily in the geopolymers within 1 min.

Electric Arc Furnace (EAF) is commonly used in steel recycling industries. Apart from steel metal product, a waste in the form of dust is also produced and so called EAF dust. The fine particulates mainly contain zinc-iron oxides along with a small amount of heavy metals like chromium and lead, and have been categorized as a toxic waste. Proper treatments can be crucially required in order to recover crude zinc oxide and iron oxide from the dust; however, no practical recycling plants have been now readily operated in Thailand. To reduce its toxicity, EAF dust could be mixed with silica-based materials and vitrified into glass. Therefore, EAF dust can possibly be employed as a ceramic glaze raw material. This work pointed out how to make decorative “oil spot” ceramic glaze by substitution of EAF dust for a conventional iron oxide. The prepared glaze mixtures were applied over the ceramic bodies and fired at 1250 °C in oxidation atmosphere. The as-fired glaze appearances with tiny and silvery crystals floating over dark brown based-glaze were exhibited. Phase content and characteristics of the obtained glaze were analyzed. The roles of zinc oxide to iron oxide ratios on oil spot and crystal generation was concerned. A comparison of oil spot effects due to different iron oxide sources was presented and discussed. Oil spot glaze made from a combination of EAF dust and iron oxide powder was also proposed.

Hydroxyapatite (HA) nanoparticles were synthesized using a wet mechanochemical method without a calcination process. Dicalcium phosphate dihydrate (CaHPO4 ·2H2 O) and calcium carbonate (CaCO3 ) were mixed and milled in a planary mill using ethanol or water as liquid media in the two different synthesized routes. Effects of rotation speed and milling time on the final products formed have been studied. Experimental results showed that HA phase having a characteristic of low crystallinity could be formed under the synthesis route using water. The original phases of both starting chemicals were remained without HA formation in the synthesis route using ethanol. Particle size and morphology of HA nanoparticles were obviously depended on optimum conditions of rotation speed and milling time. Differences on phase formation in both synthesized routes have been considered and discussed based on occurring chemical reaction possibilities. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 679-688, 2017.