Addition Of Alkali Research Articles

Kinetic investigation into pH-dependent color of anthocyanin and its sensing performance

Dynamic changing process of pH-sensitive anthocyanin solutions was monitored by time-resolved ultraviolet–visible (UV–vis) absorption spectroscopy. Two-dimensional correlation spectroscopy (2DCOS) and principal component analysis (PCA) were further used to investigate the spectral data associated with chemical structure change of anthocyanin. The addition of acid resulted in the narrowing and blueshift of the absorption band of the anthocyanin solution around 528 nm. This may be caused by the formation of flavylium cation from carbinol pseudobase. The addition of alkali led to synchronous changes of the absorption bands around 528 and 607 nm, implying the conversion of flavylium cation to quinonoidal base. 2DCOS data suggested that the peak assigned to flavylium cation during the structural conversion could be located at 520 nm, which was rarely found in the time-resolved absorption spectra. Silk fabric was dyed with anthocyanin and used as a colorimetric pH sensor. The flexible pH sensing fabric showed visual sensitivity to pH changes, with great reusability and stability. The wearable pH fabric sensors fabricated from sustainable and renewable natural biomaterials have potential applications in environmental monitoring, medicine and smart clothing.

Effect of Potassium on the Regulation of C1 Intermediates in Isobutyl Alcohol Synthesis from Syngas over CuLaZrO2 Catalysts

The important role of alkali additives in the CO hydrogenation process is related to their high promotion effect. However, the wide application of alkali additives does not reflect a thorough understanding of the mechanism of their promotional abilities. Here, we have investigated the effect of potassium (K) on the isobutyl alcohol formation over CuLaZrO₂ catalysts. It was found that K addition had a great effect on the C–C chain growth in spite of the occurrences of decreased surface area and increased CuO reduction temperature. Probe molecule experiments and in situ diffuse reflectance infrared Fourier transform spectroscopy revealed that K addition enhanced the formation of C₁ intermediates needed for isobutyl alcohol synthesis under high reaction temperature. Among the adsorbed species, bicarbonate species showed moderate adsorption intensity and benefitted from isobutyl alcohol synthesis. Meanwhile, K addition promoted the adsorption of linear CO, which was considered as another important intermediate for alcohols synthesis, thus accelerating the C–C chain growth.

Separation of Re(VII) from aqueous solution by acetone-enhanced photoreduction: an insight into the role of acetone

Efficient separation of rhenium (Re) from aqueous solution is pivotal in the resource recovery, and suitable to simulate the elimination of radiotoxic technetium (Tc) due to their similar properties. In this work, we achieved a high Re(VII) separation ratio of 95.2% within 30 min from aqueous solution via an acetone-enhanced photoreduction method, in which soluble ReO4− was reduced to insoluble ReOx and Re(0) in the presence of acetone and isopropanol. Compared with the situation in absence of acetone, acetone absorbed most of the UV energy, and the produced triplet acetone could abstract Hα atoms from isopropanol to form more strongly reductive ketyl radicals, leading to the enhancement in photoreduction. Isopropanol was the most qualified for Re(VII) photoredction due to its low C–Hα bond energy. The addition of alkali also benefited the Re(VII) separation by eliminating produced protons, and stabilizing the intermediate Re(VI) to preventing the re-formation of Re(VII) through disproportionation of Re(VI). Furthermore, selective and effective separation of Re(VII) from simulated high level liquid waste containg Nd(III) was realized as well. This work gains an insight into the role of acetone in the enhanced Re(VII) photoreduction, which may be of great significance in developing novel approaches for hydrometallurgy and spent nuclear fuel reprocessing.

Influence of alkali addition on the setting and mechanical behavior of cement pastes and mortars with electric arc furnace dust

Abstract The use of electric arc furnace dust (EAFD) in cementitious mixtures is gaining popularity. However, an arguable retardant effect in cement setting is often observed when this dust is used in proportions higher than 3%. This problem is the principle reason why high-volume addition of EAFD is typically hindered in cementitious materials; hence, this study was undertaken to isolate the effect of alkalis addition used as set-accelerant of blended cement pastes with EAFD. Mechanical properties of mortars including 10% and 20% EAFD on cement weight and with increasing alkali contents were investigated. Results indicated that increasing the alkali content was effective on shortening the setting time of blended pastes with EAFD. Final setting time of pastes with 10% and 20% EAFD was less than 6 h, and when the EAFD content was 5%, setting time was almost the same of the cement paste. Results also showed that an increase of alkali content in EAFD mortars resulted in a noticeable increase in compressive and flexural strength at 1 and 3 days, but it led to a reduction at later ages (7 and 28 days).

Antioxidant Potential of Cell Wall Polysaccharides Extracted from Various Parts of Aerva javanica

Objectives: Aerva javanica, an underutilized desert plant, is a rich source of polysaccharide but not investigated properly for the antioxidant potential of its polysaccharides. The antioxidant potential of cell wall polysaccharides in leaves, branches, stem and root of A. javanica was determined. Methods: In a sequential extraction procedure, the water-soluble fraction (WSF), sodium acetate-EDTA soluble fraction (SASF), sodium carbonate soluble fraction (SCSF), 4% potassium hydroxide soluble fraction (4%KOHSF) and 14% potassium hydroxide soluble fraction (14%KOHSF) were obtained and subjected to antioxidant analysis. Results: The addition of salt or alkali in the extraction media resulted in a significant increase in total extractable polysaccharide content. The 14%KOHSF showed higher extract yield, total antioxidant activity, ferrous ion chelating activity, ferric reducing antioxidant power and linoleic acid reduction capacity. The WSF showed higher scavenging capacity against DPPH radical. WSF of branches and root and SCSF of leaf and stem showed highest scavenging capacity against hydroxyl radical. Conclusion: The lower extraction yield but high radical scavenging capacity of WSF may be attributed to the presence of some protein linked hydrophilic polysaccharides of pectin nature. The high extractable polysaccharide content with strong antioxidant potential makes A. javanica a suitable candidate for the antioxidant polysaccharide based pharmaceutical and industrial applications.

Influences of alkali on the quality and protein polymerization of buckwheat Chinese steamed bread

The effects of alkali (NaHCO3 or Na2CO3) on the quality and protein polymerization of buckwheat Chinese steamed bread (CSB) were investigated. The alkali addition increased the specific volume of CSB, for NaHCO3 from 1.84 ml/g (control) to 2.66 ml/g. Image analysis showed that alkali increased the pore area fractions. The addition of Na2CO3 exhibited a greater pore count and lower pore average size. The texture properties were improved with the increase of crumb hardness and resilience. The extractability of protein in sodium dodecyl sulfate containing medium (SDSEP) decreased. Furthermore, SDS–PAGE showed an obvious decrease in the intensity of protein bands with lower molecular weight, while intensity of higher molecular protein bands increased. This demonstrated that alkali addition promoted protein aggregation in buckwheat CSB. In addition, the content of degydroalanine and lanthionine increased and free SH decreased, which indicated alkali addition prompted protein to form dehydroalanine-derived and disulfide cross-linkings.

Effect of photocatalytic pretreatment of potato starch for bioethanol production using Saccharomyces cerevisiae during simultaneous saccharification-fermentation (SSF)

In this study, the effect of the photocatalytic (PC) pre-treatment with TiO2 during gelatinization (GE) stage in a simultaneous saccharification-fermentation process (SSF) of potato starch for bioethanol production was evaluated. Maximum amount of reducing sugars was 119.3, 114.6 and 104.8 g l-1 for PC→GE, GE→PC and reference (without PC), respectively while bioethanol concentration it increased gradually up to a maximum amount of 128.21, 106.74 and 85.91 g l-1 after 30 h, for PC→GE, GE→PC and reference (without PC), respectively. These results were consistent with the reducing sugars concentration, because bioethanol concentration increased slightly during 18–30 h of fermentation. Although enzymatic activity (ʋmax) for reactions was similar, in reference (without PC pre-treatment) it not promoted quick substrate conversion into ethanol, despite showing the higher affinity enzyme-substrate (Km). Considering traditional potato starch hydrolysis, PC pre-treatment shortened the reaction time of the biological reactions. Thus, the PC pre-treatment of potato starch for bioethanol production could be an environmentally feasible process without acid and alkali addition.

Effect of nanoclay addition and chemical treatment on static and dynamic mechanical analysis of jute fibre composites

In this article, the influence of alkali treatment and addition of montmorillonite nanoclay as filler on mechanical and visco-elastic behaviour of jute fibre polymer composite were investigated. The composites are fabricated using 5wt% of nanoclay, untreated and chemically treated jute fibre of various percentage by handlayup method. The static mechanical properties like tensile, flexural, impact and inter laminar shear strength are studied as per respective ASTM standard. The dynamic mechanical analysis was carried out to evaluate storage modulus and damping factor of the prepared composite. The composition and structure of the functional groups of modified fibres were examined by Fourier transform infrared spectroscopy. The results showed that the interaction of filler addition and NaOH+KMnO4 treatment of fibres have significantly improved the tensile, flexural and impact properties to 47.12, 201.13, 172.61MPa respectively. Dynamic mechanical analysis results revealed that the incorporation of filler increases the storage modulus and glass transition temperature. The incorporation of 5wt% clay and 25wt% jute fiber increase the glass transition temperature of the composite material from 109 to 115 °C.

Determination of glufosinate, aminomethylphosphonic acid, and glyphosate residues in farmland soil by post-column addition of alkali using high performance anion exchange chromatography-pulse amperometric detection

A chromatographic method was developed for the determination of glufosinate (GLUF), aminomethylphosphonic acid (AMPA), and glyphosate (GLY) in farmland soil by the post-column addition of alkali using high performance anion exchange chromatography-pulse amperometric detection. Samples were extracted with 2 mmol/L sodium hydroxide solution, then filtered through a 0.22 μm membrane, and purified by a IC-C18 column and IC-Na column. Three target compounds and coexisting ions in the filtered solution were separated on an IonPacAS11-HC anion exchange column (250 mm×4 mm), and were detected by the post-column addition of alkali using pulse amperometric detection. Results showed that GLUF and GLY had good linearity in the range of 20.0-1000 μg/L, and AMPA had good linearity in the range of 5.0-400 μg/L, with correlation coefficients above 0.999. The limits of detection of GLUF, AMPA, and GLY were 0.08, 0.02, and 0.04 mg/kg, respectively, and the recoveries were in the range of 80.2%-106% with RSDs of 0.7%-5.0% (n=6). The method provides strong anti-interference, high sensitivity, and accuracy, and can be adopted simply and quickly; therefore, it is suitable for detecting the residues of GLUF, AMPA, and GLY in farmland soil.

The clonal grass Leymus chinensis overcomes salt stress by over-compensatory growth of individual ramets

Soil salinisation and overgrazing are two important factors limiting plant growth in the Songnen Grassland, Northeast China. Leymus chinensis, a dominant rhizomatous grass, resists grazing and tolerates saline–alkali stress. However, its adaptive mechanisms to the dual effects of grazing and saline–alkali stress remain largely unknown. A two-factorial field experiment was conducted in two consecutive years in the natural L. chinensis community, combining the addition of mixed saline–alkali solution (NaCl:NaHCO3:Na2CO3 1:1:1, amount 559.13 g m–2 year–1) with clipping (removal of 60% of aboveground biomass, AGB). Saline–alkali addition significantly increased AGB and total biomass in the no clipping but not in the clipping treatment. Irrespective of clipping, ramet density was significantly decreased, and individual ramet biomass was significantly increased under salt stress. The significant increase in AGB was due to a high K+:Na+ ratio, high water-use efficiency, and an increase in leaf area index and net photosynthesis rate of individual ramets under salt–alkali stress. Clipping significantly decreased AGB and total biomass regardless of saline–alkali addition, possibly because of decreased sugar content of rhizomes. Saline–alkali and clipping had an interactive effect on AGB and total biomass of L. chinensis. The significant reduction in AGB and total biomass were mainly caused by reduced proline and water-soluble carbohydrate content under dual stress. A modified and simplified graphic model of the limiting resource model was proposed based on our results. Leymus chinensis can grow well under saline–alkali stress via ramet biomass compensation, in which the significant decrease in ramet density is compensated by the significant increase in individual ramet biomass. Ramet compensation and clonal integration were identified to be main mechanisms of herbivory and saline–alkali tolerance.

The effect of densification with alkali hydroxides on brown coal self-heating behaviour and physico-chemical properties

Victorian Morwell coal’s physico-chemical properties were modified through densification with Ca(OH)2, KOH, NH4OH and NaOH, in order to compare the effects of varying alkali metals addition on self-heating behaviour.The wire basket results showed that densification of brown coal with alkali hydroxides increased the critical ignition temperature in the order Ca(OH)2 < KOH < NaOH relative to densified sample with NH4OH and without additive. The surface area and pore volume of all coal products densified with alkalis reduced. In addition, results showed that the size and charge of the exchanged cations play an important role in their interaction with coal oxygen functional groups, the extent of cross-linking network and consequently on the reduction of surface area of densified products with alkalis. Thermogravimetric analysis (TGA) results demonstrated a decrease in the proportion of the mass loss occurring at lower temperatures, and a shift to higher temperature in the main oxidation/decomposition stages, consistent with increasing the critical ignition temperature.Fourier transform infrared spectroscopy (FTIR) results suggested a catalytic role for cations (K > NH4 > Na > Ca) in the formation of quinones during kneading of brown coal under alkaline conditions. The results revealed that the addition of alkalis to brown coal at basic pH improves the oxidation tolerance of the carboxylic/carboxylate groups and also enhances the polymerization and aromatization reactions during the thermal oxidation of coal, generating aromatic ether and/or ketone substituted polymers with higher thermal stability toward oxidation. Using NaCl as additive, at coal’s natural acidic pH, resulted in a very brittle densified product, with higher macro and mesopore volumes than the coal densified prepared without additive. However, the Tcr value increased, probably due to its lower micropore volume.

Kinetics of cinnamaldehyde hydrogenation in four phase system

The kinetics of cinnamaldehyde hydrogenation in four phase system viz. gas (hydrogen)-liquid (cinnamaldehyde + toluene)-liquid (aqueous KOH)-solid (catalyst, 5% Pt/C), [GLLS] system has been studied in this work. As reported, addition of aqueous alkali in hydrogenation of unsaturated aldehydes like cinnamaldehyde shifts selectivity towards unsaturated alcohol, cinnamyl alcohol. The promotion action by alkali metals for improving selectivity towards cinnamyl alcohol involves changes in the adsorption mechanism of the cinnamaldehyde in a way that CO bond get preferentially hydrogenated. In cinnamaldehyde hydrogenation in presence of promoters two different catalytic sites can be considered, each for CO and CC bond hydrogenation. In accordance with this consideration and as demonstrated in various studies on hydrogenation of unsaturated aldehydes, further hydrogenation of intermediate-cinnamyl alcohol (CC bond hydrogenation) occurs on Pt only sites while cinnamaldehyde and intermediate hydrocinnamaldehyde (both involving CO bond hydrogenation) are hydrogenated on catalytic sites affected by promoters. This preferential adsorption and hydrogenation through CO bond leads to the increased selectivity of cinnamyl alcohol. Although, many authors have studied cinnamaldehyde hydrogenation using various promoters, there are very few reports on kinetics in which this two site approach behind promotion action has been considered. The effect of various operating parameters on the rates of hydrogenation was studied and the two site Langmuir-Hinshelwood type of kinetic model was used for evaluating the kinetic parameters by fitting experimental data. The thermodynamic model for estimating the solubility of hydrogen in the reaction mixture was incorporated with this kinetic model.

Review on Opacifying Polymeric Pigment: Reconceive Hiding

A hollow core-shell latex particle synthesized through sequential semi-continuous emulsion polymerization method has served as a promising substitute to white inorganic pigments useful for the coating applications. Incorporating more amount of Titanium dioxide in the paint is a costly measure with diminishing returns. Severe paint defects such as phase separation, agglomeration or settling arises due to incompatibility between inorganic pigments and organic resins. Opaque polymer helps in minimizing the cost of Titania in surface coating formulations. It provides white appearance and hiding due to diffraction of incoming light in different directions. It has gained widespread importance over the years due to its unique structure and morphology. It has potential applications in other technologies such as micro-encapsulation, paper coatings and controlled release of drugs. Osmotic swelling – the most prominent approach involves the synthesis of an ionizable core particle which is encapsulated by another polymer functioning as shell, followed by neutralization with the addition of suitable alkali. Significant techniques have been developed including hydrocarbon encapsulation and water-in-oil-in-water emulsion in this field.

Simultaneous removal of NOx and SO2 with H2O2 catalyzed by alkali/magnetism-modified fly ash: High efficiency, Low cost and Catalytic mechanism

A catalyst with high efficiency and low-cost is proposed which can catalyze hydrogen peroxide (H2O2) for desulfurization and denitrification simultaneously in this study. The active catalyst made by fly ash of power plant was prepared through milled, alkali modification and magnetic separation. Electron-spin-resonance test confirmed that it catalyzed the decomposition of H2O2 to generate hydroxyl radicals (OH). The simultaneous removal efficiency reached 100% for SO2 and 80% for NOx under the optimal conditions (molar ratio of H2O2 to NOx = 3:1; reaction temperature = 130 °C). The catalyst was characterized by X-ray fluorescence, X-ray diffraction, Scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, Photoluminescence and so on. The NOx removal efficiency was affected by OH concentration which attributed to content of iron in fly ash. Magnetic separation increased the iron content, and alkali addition benefited this process. We proposed reasonable catalytic mechanisms with catalyst/H2O2 in low- and high-temperature zones. In the low-temperature zone, the dissolved iron ions catalyzed H2O2 decompose to generate OH. In the high-temperature zone, H2O2 was catalyzed by hydroxyl iron (FeOH) on the catalyst surface.

Effects of weak-alkali ASP composition on the stability of O/W emulsions

ABSTRACT The effects of weak-alkali ASP composition on the o/w emulsion-stabilizing properties of simulative produced liquid by the weak-alkali ASP flooding were analyzed by use of spinning-drop interfacial-tension (IFT) meters, microscopes, zeta-potential analyzer and Turbiscan laboratory expert stabilizer in this work. The experimental results showed that the irregular movement of the droplets in the lower and middle regions is the main cause of the instability of the emulsion system. The addition of alkali changes the movement of emulsion droplets formed by the weak-alkali ASP system and the oil. Both weak-alkali and surfactants play dual roles in the ASP system. The optimum amount can make the emulsion achieve the best stability and less or more amounts are not conducive to the stability of the emulsion. Appropriately increasing the polymer concentration is helpful to increase the stability of the emulsion. However, the addition of an excessively high concentration of polymer does not increase the stability of the emulsion, resulting in unnecessary waste. It is expected that this study will be of guiding significance for the mechanism of weak-alkali ASP flooding and the treatment of produced liquid in actual production.

Alkali enhanced biomass gasification with in situ S capture and a novel syngas cleaning. Part 2: Techno-economic assessment

Previous research has shown that alkali addition has operational advantages in entrained flow biomass gasification and allows for capture of up to 90% of the biomass sulfur in the slag phase. The resultant low-sulfur content syngas can create new possibilities for syngas cleaning processes. The aim was to assess the techno-economic performance of biofuel production via gasification of alkali impregnated biomass using a novel gas cleaning system comprised of (i) entrained flow catalytic gasification with in situ sulfur removal, (ii) further sulfur removal using a zinc bed, (iii) tar removal using a carbon filter, and (iv) CO2 reduction with zeolite membranes, in comparison to the expensive acid gas removal system (Rectisol technology). The results show that alkali impregnation increases methanol production allowing for selling prices similar to biofuel production from non-impregnated biomass. It was concluded that the methanol production using the novel cleaning system is comparable to the Rectisol technology in terms of energy efficiency, while showing an economic advantage derived from a methanol selling price reduction of 2–6 €/MWh. The results showed a high level of robustness to changes related to prices and operation. Methanol selling prices could be further reduced by choosing low sulfur content feedstocks.

Decolourization by PVP stabilized Fe-Ni nanoparticles of Reactive Black 5 dye

Nanoscale Fe-Ni bimetallic particles with Polyvinyl pyrrolidone (PVP) as a stabilizer were synthesized for dye decolourization and characterized by X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM) and nano particle size analyser. Analysis of variance (ANOVA) for decolourization was done by the central composite design (CCD) with response surface methodology (RSM). Three operational factors concentration of nanoparticles, concentration of dye and pH were selected for design of experiments. The influence of reaction duration, alkali and salt addition on dye decolourization was also studied. Dye degraded product and breaking of chromophoric group was analysed by gas chromatography–mass spectrometry (GCMS) and FT-IR analysis. The dye decolourization of was 97.89% obtained with reduction in COD and BOD value was achieved with negligible generation of the sludge.

Comparison between cesium and sodium retention on calcium silicate hydrate (C[sbnd]S[sbnd]H) phases

Batch sorption experiments and sorption modelling were combined to analyse the mechanisms of Cs and Na retention on calcium silicate hydrate phases, CSH, and to identify similitudes/differences between the two elements.The role played by the CSH's Ca/Si ratio and the tracer concentration on alkali ions retention was experimentally analysed. For both elements, sorption decreased when the Ca/Si ratio increased, but only in the case of Cs sorption was clearly not linear.Distribution coefficients (Kd) for Cs were higher than those of Na at trace concentration and low Ca/Si ratio but at high alkali concentrations, Kd values for Cs and Na were always comparable. This was a first indication that low-density but high selective sorption sites exist on the CSH surface, accessible for Cs and not for Na.Electrophoretic measurements were carried out to evaluate the variation of the CSH surface charge (ζ-potential) upon alkali addition and to support modelling studies. Under similar experimental conditions, the change produced by Cs or Na additions on the ζ-potential of the gels was always similar.Different sorption models were proposed to fit the experimental data, based on the adsorption data, on the variation of CSH surface potential upon Cs/Na sorption and on previous tests showing the competitive effects of Na and Cs on Ba uptake. Their adequacy will be discussed as well as the differences/similitudes of sorption behaviour for both elements.

Bio-hydrogen and bio-methane production from food waste in a two-stage anaerobic digestion process with digestate recirculation

Abstract Bio-H2 and bio-CH4 production from food waste in a two-stage temperature phased system were investigated to determine the effects of digestate recirculation on energy efficiency and process stability. Different recirculation ratios (RR), i.e. 0.3, 0.5, and 1.0, were tested. Maximum H2 production of 3 L-H2 L−1d−1 and yield of 135 L-H2 kg−1VSin were achieved for an RR of 0.3 at HRT 5 d and OLR of 18 kg-VS m−³d−1. The RR of 0.3 was also the best for producing CH4 and gave results of 2.9 L-CH4 L−1 d−1, i.e. 510 L-CH4 kg−1VSin at HRT 9 d and OLR of 5.7 kg-VS m−³ d−1. The energy recovered from the recirculation process increased the H2 production by 8% and decreased the CH4 production by 3%; the total energy production did not change. Digestate recirculation in comparison with a no-recirculation system reduced the need for alkali addition to maintain pH in the H2-reactor by 54%.

Manufacture of high bulk paper using alkali swollen kraft pulp

AbstractEffects of alkali swelling of kraft pulp fibers and the order of alkali swelling and beating treatments on paper bulk and paper strength were evaluated in terms of NaOH concentration in order to produce high bulk sheet (i. e., high porous and low density sheet). Effects of replacement of part of furnish with the alkali swollen pulp on paper properties were also investigated. It was found that alkali swelling of pulp fiber can increase the bulk of handsheet. NaOH concentration and beating treatment influenced paper bulk and paper strength. Alkali swollen pulp without beating showed the highest handsheet bulk. The paper bulk of alkali swollen pulp with pre-beating was higher than that with post-beating. Paper strength decreased with increasing the bulk of handsheet. In addition, replacement of part of furnish with alkali swollen pulps increased paper bulk, adversely decreasing paper strength. The highest improvement in paper bulk was achieved with the addition of alkali swollen SwBKP without beating.