Alkali Concentration Research Articles

Alkali treatment of maize bran affects utilization of arabinoxylan and other non-digestible carbohydrates by the human gut microbiota in vitro in a dose-dependent manner

Alkali treatment of maize bran can break ferulate cross-linking and increase utilization of alkali-solubilized arabinoxylan (AX) by the human gut microbiome. However, it is not known how alkali treatment affects the utilization of AX and other non-digestible carbohydrates (NDC) that remain insoluble after alkali treatment, or how varying degrees of alkali treatment affect NDC fermentation. Therefore, maize bran was treated with alkali ranging from 0 to 1.25 M NaOH, neutralized, and then subjected to in vitro digestion and fermentation using human fecal microbiomes. Increasing alkali concentration progressively increased water solubility of NDC, especially AX, and increased microbial fermentation of water-soluble AX (p < 0.001) during fermentation; however, there was a decrease in fermentation of insoluble AX and NDC (p < 0.001). Across microbiomes, more acetate (p = 0.004) and propionate (p = 0.018), but less butyrate (p < 0.001), were produced as alkali treatment of maize bran increased. Higher alkali treatments increased the abundances of Bifidobacterium (q < 0.001), Bacteroides (q = 0.0015), Faecalibacterium (q < 0.001), and several genera in the Bacilli class (q < 0.001), while decreasing Bilophila (q < 0.001), Butyricicoccus (q < 0.001), and several Lachnospiraceae (q < 0.001). Soluble but not insoluble NDC utilization was improved by extracting residual free phenolic compounds from alkali-treated maize bran (p = 0.005 and p = 0.39, respectively). In conclusion, alkali makes maize bran AX more water soluble and fermentable, but it has a negative impact on insoluble AX and NDC utilization, which reduces butyrate production by the microbiome due to decreases in Butyricicoccus and some Lachnospiraceae.

Hydrogen production by aluminum corrosion: Experimental investigation and mathematical modeling

The search for new energy sources has been a great focus lately because of concerns about climate change caused mainly by fossil fuels gas emissions. The hydrogen is a promising energy source due its clean and high energy combustion. However, the major drawbacks to use hydrogen are the difficulty of formation, transportation and storage. The objective of this work is the study of hydrogen formation by aluminium reaction with water by using strong alkalis as catalysts (NaOH and KOH), and the development of a mathematical model that accounts the evolution of hydrogen at each time. Different alkali concentrations were used (1, 1.5, 2, 2.5 and 3 mol. L-1 ). The reactions were carried out with aluminum in different samples: foils, plates with 0.5 mm and 1 mm width each. The range of temperatures studied was: 295, 305, 315 and 325 K for foils and 0.5 mm plates; 315, 325, 335 and 345 K for 1 mm plates. The results showed a strong dependence of the reaction rate on the temperature, alkali concentration and shape of the samples. The model predictions of hydrogen formation agreed with the experimental data of volume versus time, as well as the peaks observed in the reaction rates.

Kinetic and hydrogen production analysis in the sequential valorization of a Populus clone by cold alkaline extraction and pyrolysis

This work employed a two-step biorefining process, consisting of a hemicellulose-rich liquor production through ultrasound-assisted cold alkaline extraction (CAE), followed by thermochemical treatment of the resultant solid phase. The post-CAE solid phase’s pyrolytic potential was assessed by application of thermogravimetric analysis (TGA) and Friedman’s isoconversional method, and also from hydrogen production. The solid phases remaining after the CAE treatment were more reactive than the untreated raw material. Notably, the alkali concentration employed in the first step was the individual variable most pronounced influence on their activation energy (Ea). Thus, at a degree of conversion α = 0.50, Ea ranged from 109.7 to 254.3 kJ/mol for the solid phases, compared to 177 kJ/mol for the raw material; this value decreased with rising glucan content. At maximal degradation, the post-CAE solid phases produced up to 15.57% v/v more hydrogen than did the untreated raw material.

Petrogenesis of early Paleozoic peraluminous A-type granites from southern China

ABSTRACT Early Paleozoic A-type granites in South China are rare, and their petrogenesis is still highly debated. This study focuses on the controversial Epo pluton in the Wuyi-Yunkai Orogen and conducts petrological and petrogeochemical research to discuss its origin. The Epo granites were emplaced at approximately 414 Ma and exhibit petrological and geochemical features of A-type granites. They contain only one ferromagnesian mineral, ferrum biotite. The granites mostly have high alkalis contents (Na2O + K2O = 6.48–8.85 wt.%), high field strength element (HFSE) contents (Zr + Nb + Ce + Y = 353–461 ppm), and high Ga/Al (104×Ga/Al = 2.50–3.72) and FeOT/(FeOT + MgO) (0.74–0.85) ratios. Besides, they formed under high-temperature (>850°C) and low-pressure (≤5 kbar) conditions. Their high A/CNK (average 1.20) and Eu/Eu* (average 0.46) values as well as Sr (average 128 ppm) and Ba (average 628 ppm) contents but relatively low Zr contents (approximately 200 ppm) further suggest a strongly peraluminous A-type affinity, a distinctive subtype of A-type granites. The Epo granites display enriched Sr-Nd-Hf isotope compositions with a whole-rock87Sr/86Sri average ratio of 0.712, whole-rock εNd(t) values ranging from − 8.9 to − 7.6, and zircon εHf(t) values clustering at − 8. Their two-stage Nd and Hf isotope model ages are 1.7 Ga to 2.0 Ga, suggesting ancient crustal sources. Furthermore, Nb/U (average 7.46), Ce/Pb (average 4.06) and other trace element ratios indicate negligible contributions from juvenile mantle materials. Our data on the Epo pluton, coupled with other contemporary A-type granites in South China, suggest that the high-temperature melting of metasedimentary basements generated strongly peraluminous A-type granites, while the involvement of metaigneous rocks or mantle-derived magmas resulted in metaluminous to weakly peraluminous A-type granites. Source diversity leads to different aluminium saturations. The heat required to produce high-temperature A-type magmas was supplied by upwelling mantle-derived magma in a postcollisional extensional setting.

Effect of Na2S+NaOH Pre-Identification Leaching on Oxidized Refractory Au-Ag Ores

This study was conducted to investigate the effect of the alkaline sulfide (Na2S+NaOH) pre-identification process on cyanide leaching performance in oxidized refractory gold-silver ores. The ore has intensive oxide, carbonate, and silicate content, and contains Au/Ag minerals containing electum, acanthite, and silver-bearing FePbZn Sulphate-Arsenate/Hydroxide minerals together with Fe, Pb, and Zn minerals. Niğde Ulukışla refractory Au/Ag ore has 8-9 g/T gold and 170-180 g/T silver grades. In mineralogical examinations, it was found that these metals were closed in minerals such as iron oxy/oxyhydroxide, calcite, and quartz or neighboring these minerals. In the cyanide soluble process after alkali sulfide preliminary procedure at room temperature, metal extraction yields were obtained as 62% for gold and 7% for silver. It is seen that silver is adversely affected by this process compared to the direct cyanidation process. However, after the hot alkali treatment process, metal extractions improved by approximately 25% of gold and 74% of silver. This increase in yield can be considered as converting Ag-oxyhydroxide into soluble Ag forms as a result of the effect of hot alkaline sulfur leaching on the cyanide process. The most important advantage of this decomposition process is to achieve high metal extraction efficiency in lower alkali concentrations.

Topology of anisotropic glasses from persistent homology analysis

Glasses are typically isotropic, but permanent or transient anisotropy can be induced by tensile strain. We use persistent homology (PH) analysis to explore the topological effects of such anisotropy in SiO2Na2O glass ensembles with variable alkali concentration as a function of frozen-in anisotropic strain. Statistical information was extracted on ring (H1) and cavity (H2) features, whereby anisotropic stretching was found to induce strong variations in the ring topology of the –O-Si-O- backbone, but only minor changes in the overall cavity statistics or in the Na distribution (the Na distribution was found to be governed by H2 persistence). Tensile fracture led to total recovery of network topology relative to the pristine (isotropic) glass. In revealing such reactions, PH and persistence similarity analysis may help to differentiate purely entropic orientation and irreversible structural alterations leading to glass anisotropy.

Highly selective extraction of lignin and hemicellulose with retained original structure from sugarcane bagasse via low-temperature soaking and acidic precipitation

Low-temperature soaking can be used to extract the majority of the hemicellulose and lignin from bagasse without substantially changing its structure.The effects of temperature, alkali concentration, and treatment duration on the extraction of hemicellulose and lignin from bagasse via low-temperature alkaline soaking were investigated. Acid precipitation provided a solution by separating lignin from black liquor and enabled the categorization of the lignin into different groups based on the reduced pH of the solution. The precipitation of hemicellulose and lignin from black liquor under different pH conditions was investigated. The optimal pretreatment conditions for bagasse were determined to be an alkali concentration of 75 g L–1 at 35 °C for 8 d, achieving a pentose selectivity of 0.97. The main organic components of lignin and carbohydrates precipitated in different pH environments. The highest xylose content in the precipitate was obtained at pH 13.65 (above 85%), whereas the lignin content was above 90% at pH 2. The results of fourier transform infrared (FTIR) spectroscopy and two-dimensional nuclear magnetic resonance (2D NMR) analyses showed that the structure of the water-soluble substances and precipitates slightly changed during alkali pretreatment, which allowed for increased accessibility in subsequent biorefineries, such as in catalytic hydrogenolysis.

Red luminescence properties of Na5Y(WO4)4 doped with Eu3+ and alkali metal ions

Abstract Na5Y(WO4)4: 6 % Eu3+, 6 % R+ (R = Li, Na, K) phosphors were synthesized using a high-temperature solid-state reaction method. Through a series of characterization methods, the crystal structure, morphology, composition, and luminescence properties of the sample are obtained. At the same time, the properties of Na5Y(WO4)4: Eu3+ phosphor added with alkali metal ions such as Li+, Na+, K+ were also studied. The experiment showed the red light emission and fluorescence lifetime of Na5Y(WO4)4: 6 % Eu3+ are improved through the doping of low concentration alkali metal agents, and Na5Y(WO4)4: 6 % Eu3+, 6 % Li+ obtained the strongest red light emission intensity. The results indicate that the red emissions intensity of Na5Y(WO4)4: Eu3+ can be enhanced through the Li+ alkali metal agents, which may lead to less use of Y3+ and hence lower cost.

Wood fibre alkalization effect on the thermal stability of meranti wood flour: a modification of the conventional method

Alkalization of plant or wood fibre (WF) is the most widely used method of chemical modification to improve reinforcement in thermoplastic composites. This process involves the complete or partial removal of extractives and or modification of lignocellulosic material. While research has shown that removal of the less thermally stable extractives results in an improvement in fibre thermal stability, in the current work it has been shown through single-factor analyses, Fourier transform infrared microscopy, scanning electron microscopy, thermogravimetric analyses and wide angle X-ray diffraction that meranti WF thermal stability is largely influenced by the holistic changes in the WF structure, which itself is affected by alkalization factors. After implementing stepwise regression on a central composite design, no empirical model could be established to explain or predict thermal stability due to interaction of treatment factors. As a result, single-factor analyses of temperature, time and alkali concentration were conducted. Single-factor analyses showed that different combinations of time, temperature and alkali concentration through a central composite design result in WF with different thermal stabilities, lignocellulosic content, crystallinities, crystallite sizes, extractives content and morphology. Alkali-treated meranti WF showed lower thermal stability compared to the untreated WF. Mild treatment conditions (e.g. 50 °C/30 min/5%) were seen to result in the most thermally stable WF. Increasing temperature, treatment duration and alkali concentration increased thermal stabilities except at harsh conditions (e.g. 50 °C/90 min/15%). A combination of high alkali concentration and long treatment times showed a combined detrimental effect on WF thermal stability. Changes in the lignocellulosic structure, crystallinity, crystallite sizes and surface features explain the observed changes in thermal stabilities.

Swelling and removal of metal in zeolit alam lampung (ZAL) using a swelling agent C15H32

Natural Zeolite, especially Zeolit Alam Lampung (ZAL) from Indonesia is a natural zeolite with a clinoptilatite-type crystal with a hollow structure. One option in modifying ZAL in the chemical field, especially catalysts and adsorbents, is the swelling method. The challenge of swelling in ZAL is the content of alkali and alkaline earth metals (Na, Mg, K, Ca), transition metals (Fe and Cu), and the Si/Al ratio of 5.9, which will influence the structure of the swelled ZAL. The selection of swelling agents with isomers of aromatic and alkane groups at C15H32 has two functions: a swelling agent and a removal agent for alkali metals, alkaline earth, and transition metals. The ability of C15H32 can break Si-O-T and Al-O-T bonds without adversely affecting the crystal structure of ZAL Swelling. SEM EDX results showed that the highest decrease in alkali and alkaline earth metal content occurred in Na and Ca metals, which amounted to 42.6% and 43.3%, respectively. The same condition also occurred in Fe and Cu transition metals, which decreased to 59.3% and 52.3%, respectively. Brunauer, Emmett, and Teller (BET) analysis showed an increase in Average pore Radius in ZAL Swelling by 35.6% (95.8442 Å) compared to ZAL of 70.6596 Å.

The effect of various factors on the yield of 2,3,3–triiode propene–2–ol–1

A triode derivative of propargyl alcohol has been synthesized, and the effects of catalyst concentration, time and temperature on the synthesis process have been studied. Various concentrations of alkalis (5,0–30,0 mass. %) have been used as catalysts. It has been found that 2,3,3–triode propene–2–ol–1 has a higher yield when the concentration of the catalyst NaOH is 15%. The effect of time duration (1–5 hours) on product productivity has also been studied. Product yield has been found to be high for 3 hours. In addition, the effect of temperature on the product’s productivity has also been studied at intervals of (10–60°C). It has been found that the yield of 2,3,3–triiodpropen–2–ol–1 was high in 3 hours at 20°C. The structure of the synthesized substance was studied and confirmed by the methods of IR– and NMR–spectroscopic analysis.

STRUCTURAL FEATURES AND PROPERTIES OF MULTICOMPONENT SODIUM-CESIUM/RUBIDIUM ALUMINOBOROSILICATE MODEL MATRIX GLASSES OF BASIS COMPOSITION

Synthesis and study of the structure and various properties of Na-Cs and Na-Rb aluminoborosilicate model glasses with addition of the alkaline-earth cations have been carried out. Vibrational spectroscopy techniques have been used to establish the high degree of polymerization and noticeable structural similarity of all synthesized glasses at fixed ratio of modifying and network-forming cations. It has been shown that increasing fraction of large cations in the total content of modifying cations leads to changes in distribution of modifying cations between the silicate and borate structural units. The observed homogeneity with the similarity of anionic structure, at different content and various combinations of alkali and alkaline-earth cations, points at promising application of these glasses as a basis for synthesis of matrix materials for high-level radioactive waste disposal.

Surface modification of bamboo fibers through alkaline treatment: Morphological and physical characterization for composite reinforcement

This study primarily emphasizes the effect of alkaline treatment on the surface morphology, and the physical properties of extracted bamboo fibers were investigated in detail. The bamboo fibers were extracted from raw bamboo culms using a mechanical extraction process followed by roller-milling techniques. The physical properties of the extracted bamboo fibers and their chemical composition were examined based on standard requirements. The extracted and sun-dried bamboo fibers were subjected to surface modifications by treating them with a 5 wt.% NaOH solution. The process involved soaking the extracted bamboo fibers for 1 day at ambient temperature; subsequently, the alkali-treated fibers were washed with distilled water several times to remove alkali content from the fiber surface until it became neutral. Finally, the fibers were dried under the sun for a week. The alkali-treated and untreated extracted bamboo fibers underwent characterization using Fourier transform infrared spectroscopy (FTIR), Thermogravimetric analysis (TGA), X-Ray diffraction (XRD) analysis, and Scanning electron microscopy (SEM). The investigation revealed an improvement in the surface morphology of the alkali-treated extracted bamboo fibers, with a significant reduction in surface roughness, as illustrated by SEM. Test results from FTIR, XRD, and TGA indicated that the alkali-treated fibers had removed lignin and hemicellulose from their surface. This study strongly suggests that bamboo fibers prepared using these techniques could be utilized as reinforcing material in composite production.

Uranium-Lead Age According to Zircon of Syenites of the Velykovyska Massif (Korsun-Novomyrhorod Pluton)

The results of uranium-lead dating of zircons from syenites of the Velykovyska massif (Korsun-Novomyrhorod pluton) of the Ingul megablock of the USh are given. The Velykovyska massif, located in the southern part of the Korsun-Novomyrhorod anorthosite-rapakivi granite pluton, in the area of the village Velyka Vyska, composed of fayalite-hedenbergite syenites. Syenites are small isolated intrusive bodies that are conventionally united in the Velykovyska massif. Several varieties of syenites are distinguished by textural-structural features and mineral composition — fine-grained, medium-grained (predominant), mesocratic (10-15% of dark-colored minerals, occasionally 20-30%), leuco- and melanocratic (present in subordinate quantities) syenites according to alkali content belong to the normal series. The anatomy of zircon crystals from a sample (217/862) of syenite discovered by well 862 was studied. Zircon crystals from the Velykovyska syenite massif are quite diverse — from transparent yellow and lilac to slightly transparent brown, cracked. Zircon crystals in the syenites of the Velykovyska massif crystallized from magmatic melt, probably with a short break in crystallization. The age of the syenites of the Velykovyska massif was determined by the uranium-lead isotope method based on three size fractions of multi-grain weights of zircon crystals from the fayalite-hedenbergite syenite, sample (217/860) and two size fractions of multi-grain weights of zircon crystals of the sample (158/860) St. 860. The discordia intersects the concordia at two points: the upper crossing corresponds to the age of 1774 ± 18 Ma and the lower one — –129 ± 955 Ma. Taking into account the slight discordance (0.9-1.6), the weighted average value of the age based on the 207Pbr/206Pbr isotopic ratio was calculated to be 1776.2 ± 2.8 Ma, which coincides within the margin of error with the age calculated from the upper intersection of concordia with discordia and which we take the time of crystallization of zircon crystals and the age of the syenite of the Velykovyska massif.

Hyalophane- and tourmaline-bearing K-metasomatised polished stone implement from Northern Hungary

A late Neolithic flat adze, originated from Szerencs-Taktaföldvár locality, North Hungary, was studied from archaeometric aspect. The adze suffered an alkali metasomatism which was revealed by the strikingly high alkali content and a large amount of potassic feldspars. Ba-rich and Ba-free potassic feldspars, and tourmaline, as characteristic minerals, were recorded from the adze. Despite of the several unique features, the precise provenance cannot be established. According to the mineral assemblage, one of the most possible provenances of raw material is Slovak Ore Mountains, near Tisovec; but due to the archaeological background of the Tiszaculture, the regions south of the Carpathian basin (Balkan, Banat) should be considered as well.

Preparation of polycrotonic aldehyde

Croton aldehyde (2-butenal) is a reactive compound. NaOH and, in the second experiment, KOH were used to get polycrotonic aldehyde. The dependence of alkali concentration and amount of water on the yield of polymerization products was revealed. It was found that the got compounds are not homogeneous, differ in their solubility, composition and physicochemical properties.

Optimization of Antiseptic Paper Soap through Varying NaOH Concentration: Combination of Cooking Oil, Citronella Oil, and Aloe Vera

Antiseptic paper soap is convenient because it is flexible, safe for the skin, easily foams, and relatively affordable. Measuring the ratio between the concentrations of NaOH, cooking oil, citronella oil, and aloe vera additives is needed to improve the quality of antiseptic paper soap. Testing the saponification rate, density, pH, water content, fatty acid (FA) level, and free alkali content is critical to determine the characteristics of antiseptic paper soap so that it meets the standards for solid bath soap according to SNI 3532-2021 which is closest to the characteristics of paper soap because SNI for paper soap is not yet available. The weight ratio of citronella oil to cooking oil used is 1:1, 1:2, and 1:3. The NaOH concentrations used were 30%, 40%, and 50% w/v. The natural additives used are 0%, 5%, and up to 10% of the total mass. The research results showed that saponification value of the antiseptic paper soap produced was 197.724 milligrams KOH/gram up to 206.138 milligrams KOH/gram, the pH of the antiseptic paper soap was 9.1-10.6, the water content value was 10.940%-23.863%, the alkali content value free is 0.044%-0.104%, total fatty acid (FA) content is 29.688%-45.734%. The best antiseptic paper soap is produced using 30% w/v NaOH with a weight ratio of citronella oil to cooking oil used of 1:1 and natural additives (aloe vera) 5% of the total mass.

Investigation of Ash Deposition Characteristics in Full-Scale Circulating Fluidized Bed Boiler Burning Zhundong Coal

ABSTRACT Due to the high content of alkali and alkaline earth metals (AAEMs) in Zhundong coal, serious ash-related problems such as slagging and fouling occurred in the process of utilization, which has attracted wide attention. In this work, the ash deposition characteristics in a new type circulating fluidized bed boiler burning Zhundong coal was studied. The effect of steam cooled flue on alleviating slagging problems was evaluated, and the influence of flue gas temperature and wall temperature on ash deposition characteristics were studied. The results showed that the mass of ash deposition and the concentration of submicron particles decrease gradually along the direction of flue gas flow in the steam cooled flue. The deposited ash changed from tightly bound to wall to loosely deposited, which indicated that the arrangement of the steam cooled flue greatly alleviated the slagging problems. Compared with flue gas temperature, the wall temperature had a greater impact on ash deposition characteristics. Mineral elements such as Na, S, Fe and Mg were more likely to enrich on the high temperature wall, while the Ca showed the opposite trend. On the low temperature wall, Na existed in the form of Na2SO4 and Na2Si2O5, while on the high temperature wall, the direct condensation of alkali metal vapor was prevented and the thermophoresis disappeared, so Na mainly existed in the form of Na2Si2O5.

Effects of high-temperature curing on hydration and microstructure of alkali-activated typical steel slag cementitious material

Hydration process, products, microstructure, and compressive strength of steel slag in alkaline environments at room and high temperature were investigated. Results show that high-temperature curing significantly promotes the early hydration, causing more products. The promoting effect of temperature becomes more apparent with higher activator content. The cumulative heat apparently increases by approximately twice at 6% alkali content. Increasing temperature has no effect on the types of products and hydration of inactive components. The products remain as Ca(OH)2 and C-(A)-S-H, but Ca/Si and Al/Si ratios significantly increase from 1.42 to 2.41 and from 0.14 to 0.21, respectively. High-temperature curing makes matrix denser, resulting in a substantial increase in the early strength. However, promoting effect on the strength diminishes over time. The growth rates of 28 d strength are only −1% and 4% at different alkali content. Moreover, alkali-activated steel slag material has great potential in the field of low-carbon cementitious materials.

Design and performance evaluation of Alkaline-Surfactant-Polymer slug of a natural surfactant of fenugreek in saline media for Foaming/Emulsification applications

The increasing demands of oil energy has created burden on conventional oil recovery methods because of which use of synthetic chemicals is increasing and creating significant health and environmental issues. Therefore, this study reports the synthesis of alkali-surfactant-polymer (ASP) slug with the use a natural surfactant and natural polymer as an alternate for foaming in saline environment of chemical-EOR applications. The natural surfactant (used at CMC level) derived from fenugreek seeds and guar gum (4000 ppm) was used as natural polymer, while the concentration of NaHCO3 (alkali) was tuned to curtail the impact of salt-ions on foam-ability of ASP slug for practical applications. It was observed that a stable air foam developed in saline medium due to the synergistic interaction between alkali-polymer. The desired ASP slug (nomenclature: 0.5ASP1) of 0.5 wt% alkali, 0.2 wt% surfactant (CMC), and 4000 ppm guar gum was developed after significant tuning in alkali concentration as per the variation in NaCl concentration (1–8 wt%). The desired slug 0.5ASP1 showed significant foaming potential till NaCl concentration of 2 wt% as demonstrated by superior foam height of 139.8 mm at span of 60 s which was only 113.4 mm for ASP slug (at salinity 2 wt%). The presence of alkali, capable of generating in-situ surfactant, and inclusion of additional natural surfactant in ASP formulation (0.5ASP1) resulted into minimum SFT of 38 mN/m and contact angle of 54°. This indicates a favorable impact of ASP slug on wettability alteration of reservoir rock and making them more water-wet. Microscopic investigations were also conducted to visualize packing and coverage of foam bubbles stabilized by 0.5ASP1 and ASP slugs. 0.5ASP1 slug sustained bubbles for longer duration than ASP slug. The results concluded that inclusion of natural derivative in form of surfactant and polymer along with inexpensive alkali makes ASP slug a green alternative for practical applications such as oil recovery, crude emulsification, CO2 foams, and IFT reduction.