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Query: UMLS:C0205700 (ash)
 15,125 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

This research has applied different chemical activators to mechanically and thermally treated fine fraction (<14 mm) of incinerator bottom ash (IBA), in order to investigate the influences of chemical activators on this new pozzolanic material. IBA has been milled and thermally treated at 800 degrees C (TIBA). The TIBA produced was blended with Ca(OH)(2) and evaluated for setting time, reactivity and compressive strength after the addition of 0.0565 mole of Na(2)SO(4), K(2)SO(4), Na(2)CO(3), K(2)CO(3), NaOH, KOH and CaCl(2) into 100g of binder (TIBA+Ca(OH)(2)). The microstructures of activated IBA and hydrated samples have been characterized by X-ray diffraction (XRD) and thermogravimetry (TG) analysis. Thermal treatment is found to produce gehlenite (Ca(2)Al(2)SiO(7)), wollastonite (CaSiO(3)) and mayenite (Ca(12)Al(14)O(33)) phases. The thermally treated IBA samples are significantly more reactive than the milled IBA. The addition of Na(2)CO(3) can increase the compressive strength and calcium hydroxide consumption at 28-day curing ages. However, the addition of Na(2)SO(4), K(2)SO(4), K(2)CO(3), NaOH and KOH reduces the strength and hydration reaction. Moreover, these chemicals produce more porous samples due to increased generation of hydrogen gas. The addition of CaCl(2) has a negative effect on the hydration of TIBA samples. Calcium aluminium oxide carbonate sulphide hydrate (Ca(4)Al(2)O(6)(CO(3))(0.67)(SO(3))(0.33)(H(2)O)(11)) is the main hydration product in the samples with activated IBA, except for the sample containing CaCl(2).
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PMID:Influences of chemical activators on incinerator bottom ash. 1871 49

Lignocellulosic materials are good and cheap precursors for the production of activated carbon. In this study, activated carbons were prepared from the pyrolysis of soybean oil cake at 600 and 800 degrees C by chemical activation with K(2)CO(3) and KOH. The influence of temperature and type of chemical reagents on the porosity development was investigated and discussed. K(2)CO(3) was found more effective than KOH as a chemical reagent under identical conditions in terms of both porosity development and yields of the activated carbons. The maximum surface area (1352.86 m(2)g(-1)) was obtained at 800 degrees C with K(2)CO(3) activation which lies in the range of commercial activated carbons. Elemental analyses of the activated carbons indicate insignificant sulphur content for all activated carbons. The ash and sulphur contents of the activated carbons obtained with chemical activation by K(2)CO(3) were lower than those by chemical activation with KOH.
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PMID:Preparation and characterization of activated carbon from waste biomass. 1902 75

A hydrothermal processing strategy of MSWI fly ash is presented for obtaining stable minerals with low toxic potential. Different hydrothermal conditions were tested to obtain high yields of new stable minerals. Experimental parameters including temperature, nature and molarity of alkali reagents, and reaction time were evaluated. The chemical stability of hydrothermal products was examined by the toxicity characteristic leaching procedure (TCLP) test and subsequent XRD for the leached residue. The significant amounts of Al-substituted 11A tobermorite and katoite in addition to minor amounts of zeolites were formed under experimental conditions at 0.5M NaOH, 180 degrees C for 48 h, however KOH treatment in a similar regime resulted in smaller amounts of Al-substituted 11A tobermorite and katoite. Similarly, a product of mixed Al-substituted 11A tobermorite and katoite could be formed from the washed fly ash treated in 0.5M NaOH at 180 degrees C for 48 h. Under the acidic condition, the treated fly ash exhibited an excellent stability of the mineral assemblage and less release of heavy metals relative to the untreated parent materials.
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PMID:Hydrothermal processing of MSWI fly ash--towards new stable minerals and fixation of heavy metals. 1918 25

Effects of both pre-treatment and number of steps in KOH activation of raw rice straw (RS) on textural and adsorption properties of RS-derived activated carbons (ACs) were investigated. Three pre-treatment protocols were tested: mechanical, chemical by NaOH pulping, and a combination of both. Activation of RS-based materials was investigated, at a constant temperature of 800 degrees C, according to two ways: a 1-step simultaneous carbonisation-activation with KOH, and a 2-steps process: carbonisation followed by activation by KOH. 2-Steps KOH activation was more efficient in producing activated carbons with high surface areas and high methylene blue adsorption than 1-step KOH activation. Additionally, 2-steps KOH activation increased the yield of activated carbons having moderate ash content (8-14%). Surface areas as high as 1917 m(2)/g were obtained when the combined mechanical-chemical pre-treatment method and a 2-steps activation process were carried out.
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PMID:2-Steps KOH activation of rice straw: an efficient method for preparing high-performance activated carbons. 1935 64

The nanoscale distribution of elements within fly ash and the aluminosilicate gel products of its alkaline activation ("fly ash geopolymers") are analyzed by means of synchrotron X-ray fluorescence using a hard X-ray Nanoprobe instrument. The distribution of calcium within a hydroxide-activated (fly ash/KOH solution) geopolymer gel is seen to be highly heterogeneous, with these data providing for the first time direct evidence of the formation of discrete high-calcium particles within the binder structure of a geopolymer synthesized from a low-calcium (<2 wt % as oxides) fly ash. The silicate-activated (fly ash/potassium silicate solution) sample, by contrast, shows a much more homogeneous geopolymer gel binder structure surrounding the unreacted fly ash particles. This has important implications for the understanding of calcium chemistry within aluminosilicate geopolymer gel phases. Additionally, chromium and iron are seen to be very closely correlated within the structures of both fly ash and the geopolymer product and remain within the regions of the geopolymer which can be identified as unreacted fly ash particles. Given that the potential for chromium release has been one of the queries surrounding the widespread utilization of construction materials derived from fly ash, the observation that this element appears to be localized within the fly ash rather than dispersed throughout the gel binder indicates that it is unlikely to be released problematically into the environment.
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PMID:High-resolution nanoprobe X-ray fluorescence characterization of heterogeneous calcium and heavy metal distributions in alkali-activated fly ash. 1978 32

In this work, unburnt coal (UC) in bottom ash from coal-fired power plants was soaked in KOH solution and activated for 1 h at 780 degrees C. The yield of activated carbons varied from 47.8 to 54.8% when the KOH/UC weight ratio changed from 2 to 4. Pore properties of these activated carbons including the BET surface area, pore volume, pore size distribution, and pore diameter were characterized based on N(2) adsorption isotherms. It was shown that the isotherms for the adsorption of methylene blue, acid blue 74, and 4-chlorophenol from aqueous solutions on these activated carbons at 30 degrees C were well fitted by the Langmuir equation (correlation coefficient r(2) > 0.9968). The adsorption capacities of methylene blue, acid blue 74, and 4-chlorophenol were obtained to be 2.40-2.88, 0.57-1.29, and 2.34-5.62 mmol/g, respectively. Moreover, the adsorption kinetics could be suitably described by the Elovich equation.
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PMID:Preparation of activated carbons from unburnt coal in bottom ash with KOH activation for liquid-phase adsorption. 2011 19

In order to improve the comprehensive utilization of major by-products in apple-juice processing, the components, antioxidant and antimicrobial activities of oil in two species apple seeds, Fuji and New Red Star, were investigated. The Soxhlet extracted oil content of apple seeds raged from 20.69 to 24.32 g/100 g. The protein, fiber and ash contents were found to be 38.85-49.55 g/100 g, 3.92-4.32 g/100 g and 4.31-5.20 g/100 g, respectively; the extracted oils exhibited an iodine value of 94.14-101.15 g I/100 g oil; refractive index (40 degrees C) was 1.465-1.466; density (25 degrees C) was 0.902-0.903 mg/ml; saponification value was 179.01-197.25 mg KOH/g oil; and the acid value was 4.036-4.323 mg KOH/g oil. The apple seed oils mainly consisted of linoleic acid (50.7-51.4 g/100 g) and oleic acid (37.49-38.55 g/100 g). Other prominent fatty acids were palmitic acid (6.51-6.60 g/100 g), stearic acid (1.75-1.96 g/100 g) and arachidic acid (1.49-1.54 g/100 g). Apple seed oil was proven to possess interesting properties, emerging from its chemical composition and from the evaluation of its in vitro biological activities. The apple seed oil was almost completely active against bacteria, mildews were less sensitive to apple seed oil than yeasts, and the minimum inhibitory concentration (MIC) of apple seed oil ranged from 0.3 to 0.6 mg/ml. The observed biological activities showed that the oil had a good potential for use in the food industry and pharmacy.
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PMID:Analysis of components and study on antioxidant and antimicrobial activities of oil in apple seeds. 2012 37

Coal-fired plants in Coahuila (Mexico) produce highly reactive fly ash (MFA), which is used in a one-step process as a raw material in producing zeolite. We explored two routes in the synthesis of zeolite: (a) direct MFA zeolitization, which resulted in the formation of W zeolite with KOH and analcime with NaOH and (b) a MFA fusion route, which resulted in the formation of zeolite W or chabazite with KOH and zeolite X or P with NaOH. No residual crystalline phases were present. When LiOH was employed, ABW zeolite with quartz and mullite were obtained. For both zeolitization routes, the nature of the alkali (KOH, NaOH, LiOH), the alkali/MFA ratio (0.23-1.46), and the crystallization temperature and time (90-175 degrees C; 8-24 h) were evaluated. Additionally, the effect of temperature and time on MFA fusion was studied. W zeolite was obtained by both zeolitization methods. The direct route is preferred because it is a straightforward method using soft reaction conditions that results in a high yield of low cost zeolites with large crystal agglomerates. It was demonstrated that aluminum modified W zeolite has the ability to remove 99% of the arsenic (V) from an aqueous solution of Na(2)HAsO(4).7H(2)O originally containing 740 ppb.
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PMID:Fly ash from a Mexican mineral coal. II. Source of W zeolite and its effectiveness in arsenic (V) adsorption. 2053 61

The objective of this study was the synthesis of alpha'(L)-C(2)S (Ca(2)SiO(4)) belite cement, starting from fly-ash of system CaO-SiO(2)-Al(2)O(3)-SO(3), and using the hydrothermal method in alkaline solution. The lime deficit in these ashes was compensated by the addition of slaked lime from lime bagging workshops. The hydrothermal treatment of the mixture was carried out in demineralized water, NaOH or KOH solution, continually stirred at a temperature below 100 degrees C and atmospheric pressure. The dehydration and calcination of the mixtures at temperatures between 800 and 1100 degrees C allowed alpha'(L)-C(2)S-rich cement to be obtained. The optimization of the synthesis parameters (temperature and time of stirring, pH of solution, temperature and duration of mixture burning) was also studied. The phase formation during various synthesis stages was studied by X-ray diffraction (XRD). Other techniques, such as SEM and EDX, were used to characterize the cement minerals. The results obtained showed that these ashes could form belite cement composed of only one dicalcium silicate phase (alpha'(L)-C(2)S).
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PMID:Synthesis of alpha'L-C2S cement from fly-ash using the hydrothermal method at low temperature and atmospheric pressure. 2054 18

This paper investigates the properties of geopolymer obtained by alkali-activation of fly ash (FA), i.e. the influence of characteristics of the representative group of FA (class F) from Serbia, as well as that of the nature and concentration of various activators on mechanical and microstructural properties of geopolymers. Aqueous solutions of Ca(OH)(2), NaOH, NaOH+Na(2)CO(3), KOH and sodium silicate (water glass) of various concentrations were used as alkali activators. It was established that the nature and concentration of the activator was the most dominant parameter in the alkali-activation process. In respect of physical characteristics of FA, the key parameter was fineness. The geopolymer based on FA with the highest content of fine particles (<43 microm), showed the highest compressive strength in all cases. Regardless of FA characteristics, nature and concentration of the activator, the alkali-activation products were mainly amorphous. The formation of crystalline phases (zeolites) occurred in some cases, depending on the reaction conditions. The highest compressive strength was obtained using sodium silicate. Together with the increase of sodium silicate SiO(2)/Na(2)O mass ratio, the atomic Si/Al ratio in the reaction products was also increased. Under the experimental conditions of this investigation, high strength was directly related to the high Si/Al ratio.
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PMID:Mechanical and microstructural properties of alkali-activated fly ash geopolymers. 2055 10


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