Effect Of Alkali Research Articles

Adsorption behavior of in-house developed CO2-philic anionic surfactants

Incorporating CO2-philic functionalities into surfactant structure is proposed to address the drawbacks of conventional foaming agents such as premature rupture of lamellae in contact with oil, surfactant loss due to adsorption on rock or partitioning between oil and water, and salinity and temperature tolerance issues. Increased activity at the gas/water interface and less surfactant adsorption to the rock due to the presence of CO2-philic chains results in higher foam durability in the presence of oil. In the present paper, a comprehensive study on the adsorption of anionic CO2-philic surfactants onto sandstone rock surface is performed to understand adsorption mechanisms through the addition of CO2-philic tail groups in surfactant structure by observing the changes in concentration, static adsorption, and point of zero charge measurements. The static adsorption tests, Fourier Transform Infrared, and the X-ray Photoelectron Spectroscopy techniques were employed to investigate the interaction of surfactants with crushed Berea sandstone core sample at 90 °C. The static adsorption values of the S (single-tail), D (double-tail), and T (triple-tail) anionic surfactants were reported to be 0.53, 0.40, and 0.6 mg /g, respectively. The effect of alkali on the adsorption process of surfactants was also investigated and the adsorption of synthesized surfactants was found significantly low in alkaline conditions. A variety of analyses, including model fitting along with kinetics and thermodynamics studies at 30, 40, and 50 °C were performed to predict the adsorption behavior. The adsorption isotherm was found to best fit in Langmuir model. The process showed the best fit in the pseudo-second-order reaction kinetics model. The spontaneity of the adsorption process was verified by thermodynamic feasibility studies of the process.

Response of short jute fibre preform based epoxy composites subjected to low-velocity impact loadings

This work aimed to investigate the low velocity impact behaviour of short jute fibre non-woven preform epoxy matrix composites experimentally. Dry fibre preforms were developed using an optimised process and a laboratory made preforming device. The effects of alkali and poly vinyl alcohol (PVA binder) treatments on impact performances of jute composites were investigated and compared at 3 J and 6 J impact energy levels. To identify the failure modes of tested composites, the X-ray µCT tomography was employed. The results demonstrated that the developed untreated short jute fibre preform reinforced composites absorbed a higher impact energy, when they were compared to treated (alkali or PVA binder) composites. For untreated composites, maximum impact forces at 3 J and 6 J energies, were found as ⁓2478 N and ⁓2319 N, respectively; for the PVA treatment these values were measured as ⁓2457 N and ⁓2216 N, while, at same energy levels, alkali treated composites showed the lowest values as ⁓1683 N and ⁓1440 N, respectively. Untreated jute fibre contains natural matrices such as hemicellulose, lignin and waxes, which ensured a positive response to absorb more energy upon impact loading. In contrast, the alkali treatment facilitates a highly fibre packed composite structure, which accelerated the impact crack propagation in tested composites, resulting in lower resistance to impact energy. Although, PVA treated composites showed reduced impact properties compared to untreated composites due to the PVA polymer brittleness on the treated fibre surface during the impact incidents, this treatment demonstrated better impact responses over the alkali treatment. The application of PVA binder on alkali-treated fibres provided an extra support to fibres and a better fibre/matrix interface and hence, this combined treatment demonstrated a slightly better impact resistance (⁓2027 N and ⁓1874 N impact forces at 3 J and 6 J respectively) compared to only alkali treated fibre composites. The SEM fracture images and the X-ray µCT damage analysis revealed different impact damage modes, which supported the observed impact results. The obtained results from this investigation could be helpful for using short jute fibre composites in various load demanding applications where impact incidents are likely to be happened.

Study and Characterization of Algerian Spart Cellulosic Fibers (Lygeum spartum): Effect of Alkali and Acid Treatments on Their Physicochemical and Morphological Properties for Papermaking

Recently, non-wood plants have increasingly gained attention, due to their versatile advantages like cost and fast-growing period. The purpose of this study was to examine the effectiveness of different treatments on Algerian Spart fibers (Lygeum spartum) using sodium hydroxide at various concentrations (8, 10, 15, and 22% NaOH), and sulfuric acid at 30% for 2h at 100 °C. Fourier infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM) analyses were used to characterize the microstructural changes in the treated fibers. The results of FTIR confirmed the presence of cellulose in the raw fibers with a crystallinity index of 49.4%. The FTIR and XRD studies showed that an 8% NaOH treatment eliminated the amorphous constituents and improved the crystallinity index. Also, SEM micrographs confirmed the removal of impurities; for the acid treated fibers a pseudo-lignin was formed and deposited on fibers surfaces in the form of spherical droplets. Moreover, a decrease in the yield of cellulose at high alkali concentrations was noticed. The results suggest the possibility of exploitation of Spart fibers and their application in papermaking and as a reinforcement in composite materials.

Effects of alkali and alkaline earth metals on co-combustion of sewage sludge and coal slime: Combustion characteristics, interactions, and kinetics

The co-combustion of sewage sludge (SS) and coal slime (CS) is a preferred method for their resource utilization, however, alkali and alkaline earth metals (AAEMs) in SS may affect the co-combustion process. In this work, the co-combustion behavior of AAEMs-rich SS and CS was investigated in terms of combustion characteristics, interactions, and combustion kinetics using a thermogravimetric analyzer. Further, the role of AAEMs in co-combustion was evaluated by loading Ca, K, Na, and Mg individually after pickling. The results revealed that co-combustion compensated for the limitations of the individual combustion processes, with SS reducing ignition and burnout temperatures and CS improving the comprehensive combustion characterization. Principal component analysis (PCA) showed that the effect of CS on co-combustion was more significant compared to SS. Significant synergies were observed in the weight loss phase of fixed carbon in the blends with 40%, 50%, and 60% CS ratios, where the peak temperature of fixed carbon combustion was reduced by 9.8 °C, 12.6 °C, and 13.1 °C, respectively, compared to the theoretical values. The effects of AAEMs on combustion were as follows: all AAEMs promoted the precipitation of volatiles except Ca, which showed inhibition of light volatiles; AAEMs had a significant catalytic effect on fixed carbon combustion. The improvement effect of AAEMs on the comprehensive combustion characteristics during co-combustion was Na > K > Mg > Ca. The catalytic effect of Na on fixed carbon was strongest at a loading of 5%, leading to a decrease in the apparent activation energy of fixed carbon combustion by 22.2 kJ/mol and a change in reactor order from n = 1 to n = 1.2 during co-combustion. This work provides a better understanding of the role of AAEMs in SS-CS co-combustion.

Study on the effect of alkali on the production of volatile fatty acids from rhamnolipid‐alkali‐thermal pretreated waste activated sludge

AbstractThis article systematically explores the strengthening effect of NaOH dosage on the fermentation acid production of Waste Activated Sludge (WAS) by the rhamnolipids‐alkali‐thermal combined pretreatment. Analyzed the dissolution characteristics of organic matter in sludge, changes in total volatile fatty acids (VFAs) content and components, and microbial community structure. Research has shown that increasing the amount of NaOH can promote the dissolution of sludge extracellular polymeric substances (EPS) and cell lysis. When NaOH dose was 60 mg/g VS, the dissolution of SCOD was the largest, reaching 5427.78 mg/L. It provides high‐quality substrate for anaerobic flora through the decomposition of refractory humus‐like substances and macromolecular substances, thus improving the production of VFAs. When NaOH dose was 80 mg/g VS, the maximum VFAs yield was 1663.76 mg C/L, and the fermentation type was butyric acid. The increase of NaOH dose promotes the effective enrichment of bacteria, and the dominant bacteria are Proteobacteria, Firmicutes, and Bacteroides at the gate level, with different abundance. The fermentation time plays a decisive role in the evolution of microbial population, and the increase of NaOH dose promotes the enrichment of acid‐producing bacteria, thus improving the production of VFAs.

Effect of Alkalis on Tricalcium Silicate Hydration with and without Incorporating Metakaolin

Effect of Alkalis on Tricalcium Silicate Hydration with and without Incorporating Metakaolin

Alkali induced changes in spatial distribution of functional groups in carboxymethylated cellulose

The aim of the work was to investigate treatment parameters that exert most influence on performance of cellulose fibers carboxymethylated from aqueous solutions. Viscose fibers were carboxymethylated in alkaline solutions of sodium monochloroacetate at two temperatures (30 °C, 50 °C) and with different levels of alkali (0.5 mol/L and 4 mol/L NaOH). The degree of carboxymethylation was assessed with both back titration and conductometric titration methods, and the performance of carboxymethylated fibers was assessed from their propensity for sorption of the cationic dye methylene blue, a putative wastewater contaminant. Higher degrees of carboxymethylation were generally observed for fibers carboxymethylated in 4 mol/L NaOH, but in dye sorption propensities, the fibers carboxymethylated in 0.5 mol/L NaOH performed better. A combination of observations from dye sorption, color measurement and conductometric titration suggested that dye permeation was greater through fibers carboxymethylated in 0.5 mol/L NaOH as compared to 4 mol/L NaOH. As permeability differences were evinced in cases also where the degrees of carboxymethylation were very similar, it appears that the reaction conditions (i.e., alkali content during carboxymethylation), in addition to degree of carboxymethylation, affected fiber performance. The effect of alkali may stem from their influence on the topographical distribution of the substituted carboxymethyl functional groups.

The effect of alkali and alkaline earth metals (AAEMs) on combustion and PM formation during oxy-fuel combustion of coal rich in AAEMs

This study focused on the effect of alkali and alkaline earth metals (AAEMs) on combustion and particulate matter (PM) formation during oxy-fuel combustion of coal rich in AAEMs. The combustion characteristics and PM formation were investigated using thermogravimetric analyzer and drop tube furnace, respectively. The results showed a catalytic role of AAEMs in coal combustion. Addition of AAEMs can decrease ignition temperature and burnout temperature and increase the comprehensive combustion index. The catalytic effect of alkali metals was stronger than alkaline earth metals. The optimal addition ratio of AAEMs was 3 wt%. Pretreatment, such as water or acid washing, effectively reduced the formation of PM0.4. Increasing furnace temperature or O2 concentration can increase particle temperature during oxy-fuel combustion. Due to Na's higher volatility compared to Mg and Ca, increasing particle temperature cannot promote the vaporization of Na, but can enhance the reactions between Na-containing precursors and coarse particles. Thus, the content of Na in PM0.4 decreased. However, increasing particle temperature can promote the reduction reactions of Ca and Mg oxides, which was the primary reason why a higher furnace temperature or O2 concentration resulted in increased PM0.4 during oxy-fuel combustion of AAEMs-rich coal.

Effect of Alkali‐ and Alkaline‐Earth‐Metal Promoters on Silica‐Supported Co−Fe Alloy for Autocatalytic CO2 Fixation

AbstractHydrothermal vents harbor numerous microbial communities rich in reduced carbon species such as formate, acetate, and hydrocarbons. Such essential chemicals for life are produced by H2‐dependent CO2 reduction, where serpentinization provides continuous H2 and thermal energy. Here, we show that silica‐supported bimetallic Co−Fe alloys, naturally occurring minerals around serpentinite, can convert CO2 and H2O to key metabolic intermediates of the acetyl coenzyme A pathway such as formate (up to 72 mM), acetate, and pyruvate under mild hydrothermal vent conditions. Long‐chain hydrocarbons up to C6 including propene are also detected, just as in the Lost City hydrothermal field. The effects of promoters on structural properties and catalytic functionalities of the Co−Fe alloy are systematically investigated by incorporating a series of alkali and alkaline earth metals including Na, Mg, K, and Ca. Alkali and alkaline earth metals resulted in higher formate concentrations when dissolved in water and increased reaction pH, while alkaline earth metals also favored the formation of insoluble hydroxides and carbonates similar to the constituent minerals of the chimneys at the Lost City hydrothermal fields.

Effect of Alkali- and Alkaline-Earth-Metal Promoters on Silica-Supported Co-Fe Alloy for Autocatalytic CO2 Fixation.

Hydrothermal vents harbor numerous microbial communities rich in reduced carbon species such as formate, acetate, and hydrocarbons. Such essential chemicals for life are produced by H2 -dependent CO2 reduction, where serpentinization provides continuous H2 and thermal energy. Here, we show that silica-supported bimetallic Co-Fe alloys, naturally occurring minerals around serpentinite, can convert CO2 and H2 O to key metabolic intermediates of the acetyl coenzyme A pathway such as formate (up to 72 mM), acetate, and pyruvate under mild hydrothermal vent conditions. Long-chain hydrocarbons up to C6 including propene are also detected, just as in the Lost City hydrothermal field. The effects of promoters on structural properties and catalytic functionalities of the Co-Fe alloy are systematically investigated by incorporating a series of alkali and alkaline earth metals including Na, Mg, K, and Ca. Alkali and alkaline earth metals resulted in higher formate concentrations when dissolved in water and increased reaction pH, while alkaline earth metals also favored the formation of insoluble hydroxides and carbonates similar to the constituent minerals of the chimneys at the Lost City hydrothermal fields.

Effect of Alkali and Alkaline Earth Metallic Species on Gas Evolution and Energy Efficiency Evolution in Pyrolysis and CO2-Assisted Gasification

Abstract In this study, the same moles of alkali and alkaline earth metallic species were introduced into pine wood to investigate their effects on biomass pyrolysis and carbon dioxide-assisted gasification. First, thermogravimetric analysis was conducted to examine the pyrolytic behavior of pine wood loaded with alkali and alkaline earth metallic species. A semi-batch fixed bed platform was used to quantify gaseous product parameters, including gas mass flowrate, gas yield, recovered energy, energy efficiency, and net carbon dioxide consumption. Thermogravimetric results indicated that the loading of alkali and alkaline earth metallic species promoted the thermal decomposition of pine wood at low temperatures, but an inhibitory effect was observed at high temperatures. In terms of pyrolysis, adding alkaline earth metals increased syngas yields, and recovered energy, as well as energy efficiency, whereas alkali metals had the opposite effect. For the gasification, the loading of alkali metals showed a stronger catalytic than the pine wood loaded with alkaline earth metals. Based on the evolution of carbon monoxide, the effects of alkali and alkaline earth metallic species on enhancing the biochar's gasification reactivity were in the sequence of sodium > potassium > calcium > magnesium. In addition, the addition of alkali metals exhibited a stronger capacity for carbon dioxide consumption, which contributed to the management of the greenhouse gas. Considering only energy efficiency, adding alkaline earth metals in biomass pyrolysis is an optimal choice due to the higher overall energy efficiency obtained in less time.

Effect of alkali and alkaline earth metal ion as glass modifiers on the spectroscopic characteristics of Er3+‐ion doped lead silicate glasses

AbstractThe spectroscopic characteristics of Er‐doped lead silicate glasses were investigated with respect to the effects of glass modifiers (Li+, Na+, K+, Mg2+, Ca2+, Sr2+, and Ba2+) with various optical basicities. Using the absorption spectra of the glasses, the Judd–Ofelt parameters of the glasses were calculated and examined, with an emphasis on the glass emission intensity ratio at 1572 nm. The spectra of the samples at low temperatures were examined, and the Stark splitting of Er3+ was investigated. The McCumber method was used to determine the emission cross sections of glasses. The SPM glass exhibited high values of full width at half maximum (51.24 nm) and the emission cross section at 1572 nm (1.908 × 10−21 cm2), with potential applications for guiding component design of 1.5‐μm fiber lasers and amplifiers.

Effect of alkali and alkaline-earth metal oxides on the chemical strengthening properties of sodium alumino-silicate glasses

Silicate based alumino-sodium (SAS) glasses were fabricated with various alkali (Li2O and K2O) and alkaline-earth metal (MgO and CaO) oxides to study their influence on chemical strengthening characteristics such as surface compression stress (CS) and depth of layer (DOL) after ion exchange of Na+ with K+. Introducing Li2O instead of Na2O decreased DOL while increasing CS up to 5.0 mol. % of Li2O. In contrast, replacing Na2O content with K2O increased DOL while decreasing CS. When alkaline-earth oxides such as MgO and CaO were substituted for Na2O, both CS and DOL decreased. Micro-Raman spectroscopy was used to study structural changes induced by alkali and alkaline-earth oxides and their impact on ion exchange properties. The inter-diffusion coefficients of K+ ions were predicted by employing the Boltzmann-Matano equation to support the chemical strengthening effect of various alkali and alkaline-earth elements in SAS glasses.

Aqueous phase reforming of various compounds in biomass derived products over Ni/α-MoO3 catalysts: Effect of alkali and alkaline earth metals

Aqueous phase reforming (APR) of biomass derived products is a promising hydrogen generation approach, and many internal alkali and alkaline earth metals (AAEMs) have been proven capable of catalyzing these processes. In this study, APR of various functional groups in biomass derived products over Ni/α-MoO3 catalyst toward hydrogen production and pollutants control was investigated. The effect of different AAEMs was comprehensively studied under a temperature of 225 °C and a residence time of 30 min. Findings demonstrated that Na, K, Ca, and Mg all showed hydrogen generation and total organic carbon removal capability, whose performances were competitive to Ni/α-MoO3 catalyst. Moreover, although the presence of single K suppressed the removal of total nitrogen (TN), the combination of K and the Ni/α-MoO3 catalyst exhibited the optimal removal efficiency of TN (69.92 %). A series of characterization results revealed that the AAEMs effectively prevented Ni leaching in the hydrothermal environment of the Ni/α-MoO3 catalysts and promoted the formation of oxygen vacancies, inhibiting carbon deposition and deactivation of the catalyst.

Influence of alkali and alkali earth metals on pyrolysis of tobacco waste

The effect of alkali and alkali earth metals on pyrolysis behavior of tobacco was revealed in this paper. Four alkali and alkali earth metal ions (Na+, K+, Ca2+, and Mg2+) were used to impregnate acid-washed tobacco. The addition of alkali and alkali earth metal ions in acid-washed tobacco increases the relative content of ketones, acids, nitrogen containing compounds, and esters, while inhibit the formation of anhydro sugars and aldehydes. The generation of solid residues is enhanced by the presence of alkali and alkali earth metal ions and the increase of K+ concentration. The addition of 0.5 mmol K+/g can increase the yield of solid residues from 13.7 wt% to 20.2 wt%. The increase of K+ concentration promotes the conversion of anhydro sugars to ketones. The effect of hot water-wash, acid-wash, and acid-infuse, which can control the concentration of alkali and alkali earth metal ions in the tobacco, on the product distribution of tobacco pyrolysis were also discussed. Acid-wash method and hot water-wash method promote the production of carbohydrate derivatives and inhibit the generation of nitrogen-containing products. After nitric acid-wash and hot water-wash pretreatment, the relative content of nitrogen-containing products decreased from 52.1% to 6.2% and 4.3%, respectively. Compared with inorganic acid-wash pretreatment method, organic acid-wash pretreatment method has weaker inhibition on nitrogen-containing products. Organic acid-wash pretreatment method promoted the formation of aromatics and aldehydes. Prewash methods facilitate the thermal decomposition of tobacco. The results from this study suggests that feedstock pretreatment could be used as a strategy of controlling aroma compounds formation from tobacco.

Exploration and Insights on Topology Adjustment of Giant Heterometallic Cages Featuring Inorganic Skeletons Assisted by Machine Learning.

Inorganic molecular cages are emerging multifunctional molecular-based platforms with the unique merits of rigid skeletons and inherited properties from constituent metal ions. However, the sensitive coordination bonds and vast synthetic space have limited their systematic exploration. Herein, two giant cage-like clusters featuring the organic ligand-directed inorganic skeletons of Ni4[La74Ni104(IDA)96(OH)184(C2O4)12(H2O)76]·(NO3)38·(H2O)120 (La74Ni104, 5 × 5 × 3 - C2O4) and [La84Ni132(IDA)108(OH)168(C2O4)24(NO3)12(H2O)116]·(NO3)72·(H2O)296 (La84Ni132, 5 × 5 × 5 - C2O4) were discovered by a high-throughput synthetic search. With the assistance of machine learning analysis of the experimental data, phase diagrams of the two clusters in a four-parameter synthetic space were depicted. The effect of alkali, oxalate, and other parameters on the formation of clusters and the mechanism regulating the size of two n × m × l clusters were elucidated. This work uses high-throughput synthesis and machine learning methods to improve the efficiency of 3d-4f cluster discovery and finds the highest-nuclearity 3d-4f cluster to date by regulating the size of the n × m × l inorganic cages through oxalate ions, which pushes the synthetic methodology study on elusive inorganic giant cages in a significantly systematic way.

DSC STUDIES OF THE EFFECT OF SODIUM CARBONATE, POLYOLS, AND EMULSIFIERS ON THERMAL PROPERTIES OF GLUTEN-FREE NOODLE DOUGH

Alkaline salt confers unique characteristics to noodles. Polyols and emulsifiers can be used to improve noodle quality and prolong their shelf life. However, there is no information regarding the effect of alkali in combination with polyols and emulsifiers on the properties of noodle dough. This research aimed to study the effects of emulsifiers [lecithin and distilled monoglycerides (DMG)] and polyols (glycerol and sorbitol) with or without sodium carbonate on the thermal properties of gluten-free noodle dough during gelatinisation and retrogradation analysed by DSC. Results showed that the addition of alkali increased the gelatinisation temperature of noodle dough (pH ~10). The effect of incorporating either emulsifiers or polyols on gelatinization temperature was significant in a neutral system compared to an alkaline system. The control presented the lowest onset temperature to melt the retrograded sample, indicating a less crystalline arrangement. Noodle dough in neutral pH had both type I and II ALCs, while alkaline noodle dough presented only type I ALCs. All retrograded samples presented only type I ALC. Polyol significantly decreased ALC formation. In conclusion, alkali had a significant effect on gelatinisation properties and proved effective in preventing the formation of crystals in starch containing DMG after cold storage.

Ruthenium Complex Hydride Catalyst as a Platform for Ammonia Synthesis: The Effect of Alkali or Alkaline Earth Elements

Ruthenium Complex Hydride Catalyst as a Platform for Ammonia Synthesis: The Effect of Alkali or Alkaline Earth Elements

Effect of alkali and alkali earth metals on reactions of stable free radicals during biomass pyrolysis: An in-situ EPR study

Stable free radicals are the long-lived macromolecule radicals formed in pyrolysis, and their reactions play an essential role in biochar formation. The alkali and alkaline earth metals (AAEMs) in biomass might be involved in the radical reactions during pyrolysis. Figuring out the effect of AAEMs on the reactions of stable free radicals can further understand the radical reaction mechanism and the formation of biochar in pyrolysis. In this paper, the in-situ electron paramagnetic resonance (EPR) spectroscopy was used to detect the stable free radicals in cocoanut pyrolysis, and the effect of AAEMs was analysed by the comparative experiments. The results indicate that the stable free radicals in nascent chars, which are generated from the thermal decomposition of biomass, could react and couple with each other. The AAEMs in biomass improve the activity of stable free radicals and promote the radical-radical coupling during high-temperature pyrolysis above 400 °C, which inhibits the condensation of aromatic structure and generates more weak bonds in hot nascent char. After stopping the heating, the weak bonds will be broken by cooling stress, thus inducing radical reactions and further changing the char structure.

Effects of alkali and alkaline earth metals on the activity and stability of Pd/SSZ-13 for passive NOx adsorption

Pd/SSZ-13 has been proposed as a passive NOx adsorber (PNA) to effectively alleviate NOx emission during vehicle cold start. However, the chemical poisons which are derived from biodiesel and lubricant oil are challenging for the practical application of PNA technology. In this paper, Pd/SSZ-13 was poisoned by alkali/alkaline earth metals to investigate the effects of chemical poisons on the adsorption performance of Pd/SSZ-13. It was found that the alkali/alkaline earth metals led to the decrease of surface area and Brønsted acid sites of Pd/SSZ-13. Strikingly, the 27Al MAS NMR demonstrated that the alkali/alkaline earth metals could effectively prevent Pd/SSZ-13 from dealumination during hydrothermal aging treatment. The H2-TPR results showed that more than 70% of Pd2+ ions were lost in the Na- and K-impregnated Pd/SSZ-13, while almost complete loss of Pd2+ ions was observed in the Mg- and Ca-impregnated Pd/SSZ-13, which resulted in the deactivation of Pd/SSZ-13. Further, the DRIFTS results showed that Mg2+ and Ca2+ ions exhibited preferential substitution for Pd2+ ions, while Na+ and K+ ions preferentially replaced the H+ ions. This work provides insights into the effects of alkali/alkaline earth metals on Pd/SSZ-13, expecting to attract attention to design PNA materials with resistance to chemical poisons.