High Levels Of Alkali Research Articles

Unveiling the Remarkable Potential of Geopolymer-Based Materials by Harnessing Manganese Dioxide Incorporation.

Thermoelectric (TE) building materials have the potential to revolutionize sustainable architecture by converting temperature differences into electrical energy. This study introduces geopolymeric TE materials enhanced with manganese dioxide (MnO2 ) as a modifying agent. Calorimetric experiments examine the impact of MnO2 on geopolymerization. Mechanical tests show that adding MnO2 (up to 5% by weight) improves the geopolymer composite's strength, achieving a peak compressive strength of 36.8 MPa. The Seebeck effect of the MnO2 -modified geopolymeric composite is also studied. The inclusion of MnO2 boosts the Seebeck coefficient of the geopolymer, reaching a notable 4273 µV C-1 at a 5% MnO2 dosage. This enhancement is attributed to an increase in the density of states (DOS) and a reduction in relaxation time. However, excessive MnO2 or high alkali levels may adversely affect the Seebeck coefficient by lengthening the relaxation time.

Dissociation and removal of alkali and alkaline earth metals from sewage sludge flocs during separate and assisted thermal hydrolysis

High levels of alkali and alkaline earth metals (AAEM, including K, Na, Ca, and Mg) in sludge needs to be removed in pretreatment process for alleviating adverse effects on subsequent disposal. Theoretically, the liquid environment provided by the pretreatment technology of thermal hydrolysis (TH) is the ideal condition for the dissolution of AAEM. Therefore, this work quantified AAEM removal efficiency of TH and carbonaceous skeleton (CSkel) assisted TH that we previously proposed for sludge dewatering. Then the mechanism of AAEM dissociating from sludge was explored through the new perspective of biological structure evolution and chemical species transformation. The results showed that all of the AAEM in raw sludge was trapped in extracellular polymer substances (EPS) and cells. Only the water-soluble K/Na in EPS could be released by TH to the supernatant, the residual K/Na in EPS was organically linked with humic matters that were generated through the degradation of proteins. Water/NH4Ac-soluble K/Na in cells still stayed inside with a more stable form of HCl-soluble after TH. Fortunately, with the assistance of CSkel, this part of K/Na could be leached out due to organic acids derived from hemicellulose decomposition. In such a case, the removal efficiency of K/Na was elevated to 55.5% and 72.5%, respectively. Unlike K/Na, nearly all the Ca/Mg in EPS were transferred to cell residuals during TH. They were combined with the bio-phosphorus in cell residuals as the form of HCl-soluble Ca/Mg-P precipitates, rather than carbonates, sulfates or other compounds. This precipitation reaction was also moderately suppressed in CSkel-assisted TH with low pH, then 7.7% and 34.1% of Ca/Mg were taken away by filtrate. This means that appropriately raising the reaction temperature and adding CSkel with high hemicellulose/cellulose contents can promote the removal of AAEM in sludge during TH process.

Efficient chlorinated alkanes degradation in soil by combining alkali hydrolysis with thermally activated persulfate

Alkali activation is the most commonly used activation method for persulfate (PS) in in-situ remediation. However, the role of alkali in pollutant degradation is still elusive, limiting the optimization of relevant remediation strategies. In this study, we found that chlorinated alkanes (e.g., tetrachloroethane (TeCA)) could be efficiently degraded by thermal-alkali activation of PS. The main role of alkali was not activating PS but hydrolyzing the chlorinated alkanes, which was evidenced by the immediate conversion of TeCA into trichloroethylene (TCE) with NaOH and PS or with sole NaOH solution. Electron paramagnetic resonance analysis also showed that with a high NaOH/PS molar ratio (4:1) the intensity of oxidative radicals decreased, implying that high levels of alkali did not favor the formation of free radicals. Interestingly, better degradation of TeCA and its product TCE was observed by the combination of alkaline hydrolysis and thermal activation of PS (where alkali was added 6 h before PS rather than simultaneously) in comparison to thermal-alkali activation of PS. This study provides new insights into the remediation of chlorinated alkane-contaminated soils by in-situ chemical oxidation.

Ilmenite as alternative bed material for the combustion of coal and biomass blends in a fluidised bed combustor to improve combustion performance and reduce agglomeration tendency

Co-firing coal and biomass has the potential to reduce GHG emissions. However, high levels of alkali and alkaline metals in biomass ash can bring additional issues to the operation of coal-fired boilers. This study investigates the effects of ilmenite as the bed material on CO and NOx emissions and combustion efficiency of a coal and biomass blend, and the agglomeration tendency of the bed material with a pilot-scale (30 kWth) bubbling fluidised bed combustor. The experiments were carried out at 900 °C using a bituminous coal blended with wheat straw pellets at 40 wt% as the fuel and silica sand as the baseline bed material. Samples of agglomerates collected from the combustor and cyclone ash were characterised by SEM-EDS, XRD, and XRF. The results revealed that ilmenite could reduce the level of excess air required to achieve complete combustion due to lower CO emissions and less efficiency loss compared to silica sand. However, ilmenite increased NOx emissions. Furthermore, the characterisation of the obtained agglomerates and cyclone ash showed that ilmenite could hinder the K-rich molten substance attachment to the bed material, leading to significantly smaller agglomerates and hence less tendency towards defluidisation in comparison to silica sand.

Hot corrosion of TBC‐coated components upon combustion of low‐sulfur fuels

AbstractGas turbine reliability is a crucial requirement for passenger safety in aviation and a secure energy supply. Hence, corrosive degradation of combustor parts, vanes, and blades in gas turbines must be prevented. One of the most severe forms of corrosion is alkali‐sulfate‐induced hot corrosion, which is associated with internal sulfidation of components and is usually anticipated to fade in importance in the absence of sulfur. However, the literature suggests that hot corrosion might still occur in low‐sulfur combustion gases. In this study, established thermodynamic modeling methods are used to analyze the low‐sulfur hot corrosion regime. Liquid sodium chromate is found to be stable in these conditions. A comparison of calculation results and engine findings suggests that high alkali levels can negatively impact thermal barrier coating life even if sulfur is absent in the fuel. Laboratory tests are carried out to validate the chromate formation on MCrAlY‐coated specimens. It is shown that molten sodium chromate can alter the oxidation behavior of MCrAlY, promoting the formation of voluminous spinel. This represents a new and different form of hot corrosion compared to type I hot corrosion.

Slagging characteristics caused by alkali and alkaline earth metals during municipal solid waste and sewage sludge co-incineration

Municipal solid waste (MSW) and sewage sludge co-incineration is developing into a new method for sludge treatment. However, waste and sludge containing high levels of alkali and alkaline earth metals (AAEMs) will likely cause slagging, corrosion and deterioration of materials during incineration. The occurrence of AAEMs is studied through extraction experiments. Additionally, the surface microstructure and composition of samples are analyzed by SEM-EDS. XRF and XRD are used to analyze the content and crystalline phases of AAEMs. The experimental results indicate that slagging samples are characterized by high amounts of Ca, Na, K, Cl, and S elements. The samples contain numerous irregular particles due to the condensation and nucleation of AAEMs. The extraction experiments and XRD analyses indicate that the insoluble AAEMs are primarily Ca-diopside and gehlenite and Na and K-aluminosilicates in the furnace. The ammonium acetate-soluble Ca consists mainly of sulfates, and the water-soluble Na and K consist of alkali chlorides in the superheaters. In the reaction tower, AAEMs mainly exist as carbonates and the slagging mechanisms are caused by soda manufacture process. The transformation and deposition of AAEMs enhance the slagging and reduce the heat transfer efficiency. The release of AAEMs can be effectively decreased through using sludge granulation technology during MSW and sludge co-incineration, and the furnace running time is extended.

Analyzing mix parameters in ASR concrete using response surface methodology

The purpose of this experimental study was to investigate the effect of some critical concrete mix parameters on the ASR expansion and engineering properties by employing response surface methodology. Box–Behnken experimental design was utilized. Three independent variables (i.e., alkali content, water–cementitious ratio, ground clay brick percentage) were evaluated in three levels—minimum, maximum and midpoint of the experimental domain. The chosen ranges for alkali content, water–cementitious ratio and ground clay brick content were 2–8kg/m3, 0.40–0.55 and 5–25%, respectively. 15 concrete mixes were prepared. Four responses (i.e., ASR expansion, compressive strength, flexural strength and modulus of elasticity) were measured in duplicates. The regression analysis showed the fitted model explains over 85% of the variations for all four responses. The plotted response surfaces showed that (a) ASR expansion decreases with ground clay brick quantity and increases with alkali content, and increases with increasing water–cementitious ratio at high alkali levels; (b) ground clay brick has positive effect on compressive strength at high alkali levels; (c) flexural strength increases with decreasing water–cementitious ratio and with increasing ground clay brick content; (d) modulus of elasticity increases with increasing ground clay brick and decreases with increasing alkali content, moreover, modulus of elasticity increases with decreasing water–cementitious ratio when brick content is high or alkali level is low, in other words, when ASR is low.

AN ANALYSIS OF THE GEM‐BLUE GLAZE OF YE WANG'S KOJI POTTERY*

Koji pottery is a glazed ceramic art used widely for figurines. In early Taiwan, it was employed in temple construction for decorative purposes. Ye Wang (1826–87) is the first historically documented Koji artist of Taiwan and also the most prominent Koji pottery artist, noted for his modelling and glazing skills. Unfortunately, his unique technique was lost following his death in 1887. In order to provide vital information for ongoing conservation work on Koji pottery, this study analysed the physical and chemical characteristics of Ye Wang's gem‐blue glaze, to discover the glaze formula. DSC combined with the two‐thirds rule revealed that the firing temperature of Ye Wang's works of art was most probably around 878–923°C. EPMA revealed that the gem‐blue glaze has high alkali levels, and belongs to the PbO–K2O–B2O3–Na2O–SiO2 system, deriving its unique colour from copper, iron, manganese and cobalt. This study found high potassium levels in the gem‐blue glaze, which are generally a characteristic of traditional Chinese glazes. In addition, a unique discovery of boron, commonly used in famille rose, was also identified in the glaze. By comparing spectra of historical and reconstructed glazes and adjusting the proportion of chromophoric elements, this study found a glazing formula with colours close to those of Ye Wang's gem‐blue glaze.

A NO x trap for low-temperature lean-burn-engine applications

A NO x trap that uses only high-surface-area alumina as the NOx-storage material appears to provide significant advantages over the conventional baria-based trap for exhaust-gas after-treatment in low-temperature exhaust (∼250 °C) characteristic of light-duty diesel-powered vehicles operating at low speed/load conditions. In particular, an alumina trap provides better low-temperature NO x conversion and also allows more efficient de-sulfurization than a baria-based trap in laboratory evaluations. Both of these features are ascribed to the difference in basicity of the NO x -storage materials, which leads to thermally less stable nitrate (nitrite) and sulfate compounds in the case of alumina compared to conventional traps with high levels of alkali or alkaline-earth metal oxides. Further studies, extending the laboratory experiments to engine and vehicle evaluations, are still needed, however, in order to fully assess the true potential of the alumina trap.

Alkali activation of reactive silicas in cements: in situ 29Si MAS NMR studies of the kinetics of silicate polymerization

In the highly alkaline environment of the cement paste of a concrete, a source of silica can potentially react in two ways. In the pozzolanic reaction, it can combine with free lime to generate additional calcium silicate hydrate binding phase. Alternatively, reaction with alkali to form a gel can occur; this gel may swell and degrade the concrete. 29Si magic angle spinning (MAS) and cross-polarization (CP) MAS nuclear magnetic resonance (NMR) studies have been performed to determine the silicate connectivity in some model cement systems; 29Si enrichment was utilized to enable a series of spectra to be acquired in situ from a single sample. The hydrate from pozzolanic reaction of lime with silica was similar to the hydrate formed around silica in blended pozzolanic cements, with a relatively high crystallinity and long silicate chains. In the absence of lime, silica reacted with an alkaline solution to produce a gel having a high degree of cross linking, and a range of silicate mobilities. Tricalcium silicate hydration was found to be accelerated significantly by high levels of alkali (KOH) in solution; the hydrate formed had shorter silicate chains and was more crystalline than that produced by reaction in pure water. Hydration in alkali solution of a model blended cement, comprising a mixture of tricalcium silicate and silica, gave rise to two products, a long chain calcium silicate hydrate (C-S-H) and an alkali silicate of low rigidity. The alkali silicate phase gradually polymerized; at later ages it underwent a phase change, although no crystalline phase appeared to be formed. Silicate exchange took place between the C-S-H and the alkali silicate phase at a slow rate.

Evaluating the reaction of actual compositions of concrete with respect to alkali-aggregate reactions preliminary testing at 110°C and 150°C

Different curing methods at 110°C and 150°C were tested on concrete prisms of various compositions in order to develop a rapid expansion test to evaluate the risl of AAR in actual concrete compositions. While no significant expansion occurred at 110°C (in water or water vapour), we obtained expansion values in the range 0–0.35% for concrete prisms cured at 150°C in water or in alkaline solution during 3–5 weeks. For both curing methods at 150°C, the highest expansion values are obtained for potentially reactive aggregates and high alkali levels in the concrete, whereas the lowest expansions correspond to the concrete mixes containing only non-reactive aggregates or having a total alkali content of less than 2.5 kg m−3. However, alkaline treatment accounts better for the effectiveness of mineral admixtures and, in general, for the reactivity of the concrete compositions, than curing in water. From the correlations obtained with data at 38°C or 60°C and 100% RH after 12 and 4 months, respectively, alkaline curing for 3 weeks at 150°C shows a reasonable potential for predicting accurately the influence of the total alkali content, nature of the aggregates, water/cement ratio and effectiveness of mineral admixtures on concrete expansion.

Alkali-labile sites are prevalent in kidney tissue DNA

Inherent DNA damage in the form of single strand breaks and alkali labile sites is generated by essential intracellular processes, such as DNA replication and repair. Utilizing the in situ DNA unwinding assay and the comet assay (single cell gel), we have observed high levels of alkali induced DNA strand breaks in cells isolated from mouse kidney tissue homogenate. Kidney cell DNA demonstrated a 7.4 × increase in nucleoid expansion and a 7 × increase in comet length compared to negative control cells (thymocytes and splenocytes) in the two assay systems, comparable to epididymal sperm cells which have previously been demonstrated to contain abundant alkali-labile sites. These results argue for the existence of prevalent alkali-labile sites in kidney cell DNA.

Morphological, mineralogical and chemical features of steam-cured concretes containing densified silica fume and various alkali levels

Densified silica fume was incorporated in concrete mixes, containing various alkali contents, at the rate of 10% silica fume replacing 20% cement by mass. The cast specimens were steam-cured at 75°C and were examined by scanning electron microscopy, X-ray diffraction and thermal analysis soon after steam curing (1 day), and after periods of28 days and 1 year of external exposure. Mortars with and without silica fume were made with the same cement as that used in the concretes, and their pore solutions were expressed at different ages for the determination of their chemical compositions. The results show that the silica fume is very effective in removing alkali from the pore solution. However, densified silica fume agglomerates of 40-100 μm size persisted in the concrete, and in the presence of high alkali levels acted like reactive aggregate. Nevertheless, the silica fume was very effective in reducing the concrete expansion caused by a reactive granite aggregate, although it added slightly to the expansion of concretes containing a non-reactive basalt aggregate. The silica fume also had an influence on the type of sulphoaluminate phase formed in the concrete, and favoured the formation of ettringite. Therefore, silica fume may be effective in controlling both the alkali—aggregate reaction and secondary-ettringite formation in steamcured concrete.

Laser-enhanced ionisation spectrometry following matrix modification by automated chelation chromatography for the analysis of biological and environmental reference materials

Trace metal analysis of biological and environmental materials by laser-enhanced ionisation (LEI) spectrometry is hampered by measurement interferences caused by high levels of alkali and alkaline earth elements. The use of chelation chromatography to remove the interfering elements from samples prior to analysis is demonstrated, and results from the use of an automated chelation chromatography system are presented. Using this procedure, LEI spectrometry has been utilised for the determination of trace metals in biological and environmental samples. The performance of LEI for the certification analysis of six National Institute of Standards and Technology (NIST) Standard Reference Materials (SRMs) is described. The reference materials analysed and the elements determined include: Cd, Co, Cu, Mn, Ni and Pb in Trace Metals in Water (SRM 1643b); Mn and Ni in Inorganic Constituents in Bovine Serum (SRM 1598); Ni and Pb in Buffalo River Sediment (SRM 2704); Cu, Mn and Ni in Total Diet (Proposed SRM 1548); Mn and Ni in Apple Leaves (Proposed SRM 1515); and Mn and Ni in Peach Leaves (Proposed SRM 1547). The concentrations of the elements determined in SRM 1643b ranged from 20 to 47 ng g–1, in SRM 1598 they were 3.87 and 0.76 ng g–1, in SRM 2704 45.7 and 154.4 µg g–1, in proposed SRM 1548 2.43, 5.04 and 0.41 µg g–1, in proposed SRM 1515 54.9 and 0.97 µg g–1 and in proposed SRM 1547 98.4 and 0.74 µg g–1. Precisions ranged from 0.8% relative standard deviation (RSD) for Co in SRM 1643b at a concentration of 26.0 ng g–1 to 36% RSD for Ni in SRM 1598 at a concentration of 0.76 ng g–1.

Biological reference materials from the National Institute for Environmental Studies (Japan)

The National Institute for Environmental Studies has recently undertaken the development of two new biological reference materials, Sargasso (NIES No. 9) and Rice Flour-Unpolished (NIES No. 10), for trace element analysis. The sargasso seaweed (Sargassum felvellum) reference material contains high levels of alkali, alkaline earth elements and As, together with low concentrations of heavy metals. The rice flour-unpolished reference material was prepared from unpolished rice collected from three different locations in Japan. This reference material consists of three samples, each containing different levels (low, medium, high) of Cd. This paper presents the preparation and elemental composition of NIES Sargasso and Rice Flour-Unpolished reference materials, following a brief description of each of the currently available NIES certified reference materials (NIES No. 1-No. 8).

Investigation of the structural forms of potassium in coke by electron microscopy and X-ray absorption spectroscopy

An investigation of the chemical and structural forms of potassium in coal, coke, and potassium-enriched coke has been made. The principal analytical techniques used were X-ray absorption spectroscopy, computer controlled scanning electron microscopy, and scanning transmission electron microscopy. The potassium in the bituminous coals investigated was contained in the clay mineral illite, which was transformed to a predominantly amorphous or glassy potassium aluminosilicate during coking at temperatures of 1050–1100 °C. In cokes artificially enriched in potassium and annealed at 1260 °C under argon, two principal forms of potassium were identified: potassium in K-enriched aluminosilicates and silicates, and potassium dispersed throughout the carbonized macerals and bonded to carbon. Although the aluminosilicates and quartz act as effective potassium receptors, approximately half of the added potassium was dispersed through and bonded to the carbonized macerals. Both potassium forms were predominantly amorphous in structure. Analysis of the electronic structure and local atomic environment by X-ray absorption spectroscopy showed that these amorphous phases exhibited some similarities to chemically similar crystalline phases such as leucite (KAlSi 2O 6) and intercalated potassium-graphite (KC 8). X-ray absorption spectroscopy measurements on samples extracted from a blast furnace experiencing high alkali levels indicated that the forms of potassium in the blast-furnace coke were qualitatively similar to those in the laboratory prepared cokes, and suggested a possible mechanism for alkali attack on refractories.

Studies on forage cell walls

SummaryResults of a 13-week group feeding study (Expt 1) and a 16-day digestion and mineral, nitrogen and water balance study (Expt 2) in which alkali-treated rice hulls were fed to young Border-Leicester × Merino sheep of 24-kg body weight are reported.Five pelletized diets comprising a 1:1 mixture of ground lucerne and alkali-treated ground rice hulls (Expt 1) or these five diets supplemented with biuret plus one diet of 100% lucerne pellet (Expt 2) were examined.Sodium hydroxide at levels of 0, 2·5, 5, 10 and 15% (w/w) was applied to rice hulls for 12 h and neutralized with acid. Sheep fed the 5% NaOH treatment level or greater maintained or increased body weight: those fed the 0 and 2·5% level lost body weight. Daily food organic matter intakes were: 5% alkali, 1025 g, 0% alkali, 765 g; 100% lucerne, 1195 g.Organic matter digestibility was highest (52%) for the diet containing rice hulls treated at the 15% alkali level and this digestion coefficient was significantly greater (P < 0·05) than for the control diet (nil alkali) (42%) but not significantly greater than for diets with 2·5, 5 and 10% levels of alkali.It'is indicated that cell wall organic matter of rice hulls treated with 15% alkali was digested to an extent of 62% whereas cell wall organic matter in the control diet (0% alkali) was digested to an extent of 13%.Cellulose digestion (52%) of the rice hull component of diets was not increased by alkali treatment suggesting the alkali to have freed hemicellulose components of the cell wall for digestive attack. Digestibility of lignin of the rice hull component of diets was not significantly increased by alkali treatment.Animals tolerated the salt contents of diets containing rice hulls treated at high levels of alkali, were able to clear the excess salt from their bodies without significant alteration of their blood haematocrit ratios, and drank significantly more water. All sheep fed diets containing rice hulls had appreciable amounts of soluble silica in their blood plasma (> 100/μg/l) and urine (> 25 μg/l).It is concluded that alkali beneficiation of rice hulls offers a means of enhancing their nutrient worth to ruminants and that the process requires further study.