Presence Of Alkali Metals Research Articles

Highly selective extraction of aluminum from chloride and sulfate solutions using a mixture of alkoxycarboxylic acid and tributyl phosphate

Four different solvent extraction systems are compared for aluminum (Al) separation in the presence of alkali metals, alkaline-earth metals, and transition metals. The octoxyacetic acid (OOA acid) is utilized as an Al extraction reagent for the first time, exhibiting high selectivity for Al. The impacts of the concentration of extractants, the equilibrium pH of the aqueous phase, and the concentration of phase modifier were studied systemically. The results indicate that the Al extraction efficiency using OOA/TBP (tributyl phosphate) system could reach 98.9 ± 0.63 % via a single-step solvent extraction process while maintaining negligible extraction for the other metal ions at the pH value of ∼ 4.2. Meanwhile, the separation factors (β) of Al over magnesium, calcium, manganese, cobalt and nickel reach the maximum values (βAl/Mg = 285157, βAl/Ca = 18275, βAl/Mn = 19271, βAl/Co = 10814, βAl/Ni = 5969). Slope analysis and infrared spectroscopic characterization confirm that the extraction of Al by the OOA/TBP system follows the cation exchange mechanism. The OOA/TBP solvent extraction system is promising for the efficient separation of Al, with potential applications in a wide range of practical scenarios.

Mechanistic study of better K-resistance on Mn/TiO2 catalysts with preferentially exposed anatase {0 0 1} facets in low-temperature NH3-SCR

The presence of alkali metals in the flue gas can physically and chemically poison the catalyst, leading to catalyst deactivation. In this paper, Mn/TiO2 catalysts with exposed TiO2 {001} (NS) and TiO2 {101} (NP) facets are studied for potassium poisoning. It was found that Mn/TiO2-NS exhibited higher denitrification efficiency and tolerance to potassium compared to Mn/TiO2-NP. Experimental characterizations and DFT calculations showed that the NH3-SCR reaction on the surface of both fresh Mn/TiO2-NS and Mn/TiO2-NP catalysts was controlled by the E-R and L-H mechanisms. The presence of K species did not decrease the specific surface area of Mn/TiO2-NS catalyst. Under the same K poisoning condition, Mn/TiO2-NS was able to retain more surface acidic sites and surface active species, whose reaction was still controlled by the E-R and L-H mechanisms. While the adsorption and activation of NO on the Mn/TiO2-NP surface was severely inhibited by the presence of K, resulting in the L-H mechanism blocked.

Li+(3)Mg−: A new alkaline earthide with large nonlinear optical response

Alkali metal doping has been identified as a vital step in facilitating an increase in the first hyperpolarizability(β0). To further explore this concept, we utilized Calix (Zhang et al., 2018) [3]pyrrole (3), Calix (Ma et al., 2017) [4]pyrrole (4), and Calix (Aloraini et al., 2022) [5]pyrrole (5) as our three ligands in this study. The choice of these ligands was based on their ability to undergo alkali metal doping, which ultimately led to an enhancement in the first hyperpolarizability. By doping alkali metal lithium, three new compounds Li@3, Li@4 and Li@5 were theoretically designed. Then the alkaline earthide Mg was doped onto the Li@3, and a new alkaline earthide compound Li+(3)Mg− was designed. The geometric structure and nonlinear optical properties of the molecules were studied using the CAM-B3LYP functional. The results show that Li+(3)Mg− has a considerable first-order hyperpolarizability, β0 = 21401 au, The β0 value for the 3 system is merely 37 au, whereas for the Li@3 system, it reaches a high of 12257 au Li+(3)Mg− exhibits a β0 value that is over 500 times greater than that of 3. It is evident that the electronic structure and nonlinear optical properties are significantly affected by the presence of alkali metal and alkaline earthide atoms doped in 3. The excess electron derived from alkali metal atoms and alkaline earthide atoms are significant contributors to the sudden increase in the β0 within Li+(3)Mg−. We sincerely hope that the development and production of materials with nonlinear optical properties in this study can provide new ideas and methods for the innovation of electride.

Reaction of Ph2C(X)(CO2H) (X = OH, NH2) with [VO(OR)3] (R = Et, nPr): structure, magnetic susceptibility and ROP capability.

Reaction of [VO(OR)3] (R = Et, nPr) with 2,2'-diphenylglycine afforded the alkoxide-bridged dimers {[VO(OR)(μ-OR)][Ph2C(NH2)(CO2)]}2, whereas use of benzilic acid, in the presence of alkali metals, afforded 16-membered metallocycles {V8(O)4M(OR)8[Ph2C(OH)(CO2)]12} (M = <1 Na, K). For the ring systems, magnetic susceptibility data is consistent with mixed-valence vanadium with an average oxidation state of 3.5. The dimer and ring systems are capable of the ring opening polymerisation (ROP) of ε-caprolactone under N2, air, or as melts affording mostly low to medium molecular weight cyclic and linear products.

Upcycling of the Used Cigarette Butt Filters through Pyrolysis Process: Detailed Kinetic Mechanism with Bio-Char Characterization.

Thermo-chemical conversion via the pyrolysis of cigarette butt (CB) filters was successfully valorized and upcycled in the pre-carbonization and carbonization stages. The pre-carbonization stage (devolatilization) of the precursor material (cellulose acetate filter, r-CAcF) was analyzed by micro-scale experiments under non-isothermal conditions using TG-DTG-DTA and DSC techniques. The results of a detailed kinetic study showed that the decomposition of r-CAcF takes place via complex mechanisms, including consecutive reaction steps and two single-step reactions. Consecutive stages include the α-transition referred to as a cellulose polymorphic transformation (cellulose I → II) through crystallization mechanism changes, where a more thermodynamically ordered system was obtained. It was found that the transformation rate of cellulose I → II ('cellulose regeneration') is strongly affected by the presence of alkali metals and the deacetylation process. Two single-step reactions showed significant overlapping behavior, which involves a nucleation-controlled scission mechanism (producing levoglucosan, gaseous products, and abundant radicals) and hydrolytic decomposition of cellulose by catalytic cleavage of glycosidic bonds with the presence of an acidic catalyst. A macro-scale experiment showed that the operating temperature and heating rate had the most notable effects on the total surface area of the manufactured carbon. A substantial degree of mesoporosity with a median pore radius of 3.1695 nm was identified. The presence of macroporosity on the carbon surface and acidic surface functional groups was observed.

Spatially resolved analysis of CO2 hydrogenation to higher hydrocarbons over alkali-metal promoted well-defined FexOyCz

A series of catalysts for CO2 hydrogenation to higher (C2+) hydrocarbons were prepared through controlled decomposition of iron (II) oxalate dihydrate impregnated with Li, Na, K, Rb or Cs carbonate. They consist of Fe3O4, Fe5C2, Fe3C and Fe. Their steady-state spatial phase distribution is, however, affected by the presence and the kind of the promoter. These structural characteristics determine catalyst activity and product selectivity. Fe3C seems to favor CH4 formation, while C2+-hydrocarbons are formed over Fe5C2. A positive relationship between the rate of C2+-hydrocarbons formation and the rate constant of dissociation of adsorbed CO2 was established, while an opposite dependence is valid for the rate of CO2 methanation. The rate constant of this reaction increases in the presence of alkali metal and with an increase in its atomic number. Therefore, CH4 is mainly formed over Rb- or Cs-doped catalysts through CO hydrogenation, while CO2 methanation prevails over the remaining catalysts.

Alkali-resistant NOx reduction over FeVO4/TiO2 catalysts via regulating the electron transfer between Fe and V

The presence of alkali metals in exhaust gas from stationary resources causes a grand challenge for the practical application of selective catalytic reduction (SCR) of NOx with NH3. Here, alkali-resistant NOx reduction has been successfully implemented via tailoring the electron transfer over Fe and V species on FeVO4/TiO2 catalysts. The strong interaction between Fe and V induced electron transfer from V to Fe and strengthened the adsorption and activation of NH3 and NO over active VOx sites. In the presence of K2O, the strong electron withdrawing effect of Fe offset the electron donating effect of K on the VOx species, thus protecting the active species VOx to maintain the NOx reduction ability. The enhanced adsorption and activation of NH3 allowed SCR reaction to proceed via E-R mechanism even after K2O poisoning. This work elucidated the electronic effects on the alkali metals resistance of traditional ferric vanadate SCR catalysts and provided a promising strategy to design SCR catalysts with superior alkali resistance.

Unraveling alkali-tolerance role of zeolite coupling CeWOx catalyst for NOx reduction

The deactivation of the selective catalytic reduction (SCR) catalysts in the presence of alkali metal is still unsolved to date, there is no fully effective strategy to remedy it. Herein, a series of novel zeolite coupling CeWOx catalysts (CeWOx@ZSM-5) with core-shell structures was synthesized by a simple method. The proposed CeWOx@ZSM-5 catalyst exhibited superior deNOx performance and K-poisoning resistance, which are attributed to the synergy between the shell and active components. The zeolite shell with abundant acid sites can act as a sacrificial agent to preferentially bind to K, thereby decelerating/inhibiting the alkali metal poisoning process of the catalyst. Even after loading 1 wt% K, the NOx conversion remained as high as > 80% at 300–500 °C over the CeWOx@ZSM-5 catalyst under humid conditions. The novel zeolite coupling CeWOx catalyst may serve as a workable reference for new, efficient, and highly poisoning-resistant SCR catalysts for practical application.

Hydrothermal modification of TiO2 nanotubes in water and alkali metal electrolytes (LiNO3, NaNO3, KNO3) – Direct evidence for photocatalytic activity enhancement

The influence of hydrothermal annealing (HA) of TiO2 nanotubes (TiO2-NTs) in various baths (H2O, LiNO3, NaNO3, KNO3 performed for 4 h, 24 h, 64 h), on their photocatalytic and photoelectrocatalytic properties, was studied. The use of electrolytes was to enable the monitoring of photoactivity changes as a result of the expected impact on the population of hydroxyl groups on the surface. The assumption turned out to be correct and it was proved that the presence of Li+, Na+ or K+ does not allow achieving the same increases in photoactivity as observed for water. Modified samples exhibit significantly decreased F, P and carbon containing species. The length of the HA annealing time considerably affected the geometry of the nanotubes: eliminated clusters, changing the tilting angle of nanotubes, the wall thickness and inter-nanotube distance. Morphology changes due to HA treatment were associated with the interference phenomenon recorded as maximum in the Vis range. HA treatment in water brings about the most photoactive and photoelectroactive material characterized with minor modification in the optical bandgap and position of the flat bad potential. The optical energy bandgap values for electrodes containing alkali metals were reduced (up to 2.72 eV) and flat-band potential was shifted towards the anodic direction (up to 0.25 V disparity). However, increased activity as photocatalysts in the methylene blue degradation process and higher photocurrent generation was achieved for samples after modification in distilled water than in electrolytes, but these parameters are still better in comparison to unmodified titania nanotubes. Long-term treatment in water and electrolytes reduced threshold potentials for oxygen evolution reaction. The studies confirmed the effectiveness of the hydrothermal method for obtaining better photocatalytic parameters of TiO2-NTs and indicate that the presence of alkali metals is not favourable for maintaining high photocatalytic parameters.

Roles of inorganic potassium in the evolution of heavy volatile during cellulose steam reforming

Biomass sources could transform into green chemicals and energy through steam reforming but heavy components of the resulting volatile, which are the precursors of undesirable coke, would also be formed. In the current study, the evolution of heavy components from cellulose is investigated. The effects of an inorganic potassium salt KCl on the heavy component evolution during steam reforming are firstly revealed in the homogeneous steam-volatile reforming process. The results suggest that heavy components were formed by polymerization reactions accompanied with dehydration and decarboxylation. Steam and alkali metal both promoted the cracking and secondary polymerization of heavy components. In the presence of steam and alkali metal, the percentage of molecules with low weight (<250 Da) and high weight (>500 Da) both improved. KCl significantly promoted the polymerization of oxygen-containing compounds, increasing the average oxygen number of the heavy components by 1.4 to 2.2 times depending on the reaction temperatures. Heavy phenols are also promoted in the presence of alkali metal below 700℃.

Efficient NOx Abatement over Alkali-Resistant Catalysts via Constructing Durable Dimeric VOx Species.

The presence of alkali metals in flue gas is still an obstacle to the practical application of catalysts for selective catalytic reduction (SCR) of NOx by NH3. Polymeric vanadyl species play an essential role in ensuring the effective NOx abatement for NH3-SCR. However, polymeric vanadyl would be conventionally deactivated by the poison of alkali metals such as potassium, and it still remains a great challenge to construct robust and stable vanadyl species. Here, it was demonstrated that a more durable dimeric VOx active site could be constructed with the assistance of triethylamine, thereby achieving alkali-resistant NOx abatement. Due to the rational construction of polymerization structures, the obtained TiO2-supported cerium vanadate catalyst featured more stable dimeric VOx species and the active sites could survive even after the poisoning of alkali metal. Moreover, the depolymerization of VOx was suppressed endowing the catalysts with more Brønsted and Lewis acid sites after the poisoning of alkali metal, which ensured the efficient NOx reduction. This work unraveled the effects of alkali metal on the polymerization state of active species and opens up a way to develop low-temperature alkali-resistant catalysts for NOx abatement.

Theoretical insights into the origin of promoter effect of alkali metals on Au-catalyzed nitrogen electroreduction

A deeper understanding on promotion effect of alkali metals on initial N2 electroreduction at Au(111)/H2O electrochemical interface is performed. The results show that presence of alkali metals can lead to spontaneous occurrence of initial N2 electroreduction. We speculate that proton in solvent is more facile to migrate into physically adsorbed N2 molecule due to incorporation of alkali metals. The promotion effect of alkali metals may originate from increased kinetic overpotential. It can be also attributed to the retarded HER, which can further increase selectivity of initial N2 electroreduction. Thus, origin of the promotion effects of alkali metals is revealed.

Carbonation of calcium-magnesium pyroxenes: Physical-chemical controls and effects of reaction-driven fracturing

The weathering of primary silicates, and their carbonation in particular, is key for the geochemical cycling of elements, strongly affecting the C cycle and the long-term regulation of the Earth's climate. The knowledge on the controlling factors and mechanisms of aqueous carbonation of primary silicates is however still far from complete. This precludes a better understanding of their chemical weathering in nature and is a strong handicap to implement effective Carbon Capture and Storage (CCS) strategies. Here, dissolution-carbonation reactions of two abundant Ca-Mg pyroxenes, augite and diopside, have been investigated in experiments conducted at hydrothermal conditions, in the presence/absence of different carbonate sources (NaHCO3 and Na2CO3). We show that the main reaction products are low-magnesium calcite and amorphous silica. A higher conversion of augite (∼38 wt%) than diopside (∼15 wt%) was achieved. The presence of abundant Fe and Al (and minor Na) in the former pyroxene strongly enhances the release of cations to the solution, and contributes to the formation of abundant secondary crystalline and amorphous silicates as well as carbonates (Na-phillipsite and magnesium silicate hydrate, MSH, as well as calcite). In particular, Na-phillipsite nucleates in etch pits exerting a crystallization pressure ∼100 MPa exceeding the tensile strength of augite (i.e, failure under tension due to breaking of inter-atomic bonds as well as opening and propagation of subcritical fractures or flaws) and causing extensive fracturing. This takes place via an interface-coupled dissolution-precipitation mechanism, despite the bulk system being undersaturated with respect to this phase. Limited reaction-induced fracturing was also observed following MSH precipitation within diopside crystals. Reaction-induced fracturing increases exposed reactive surface area and creates channels for solution flow, thereby contributing to the progress of the reaction via a positive feedback loop. Ultimately, our results help to understand differences in the kinetics and mechanisms of chemical weathering of these two abundant rock forming inosilicates relevant for CCS strategies, showing that secondary phase formation (other than carbonates) are fostered by moderately alkaline pH and the presence of alkali metals, resulting in reaction-driven fracturing that enables the progress of silicate carbonation for an effective, safe, and permanent CO2 mineral storage. We also show that under our experimental conditions the precipitation of amorphous silica and calcite cannot generate sufficient pressure as to create fracturing, an effect that limits carbonation of Mg-Ca-Fe pyroxenes.

Assessment of the Composition of Forest Waste in Terms of Its Further Use.

This paper presents the results of the analysis of the chemical composition and content of heavy metal contamination in forest logging residues, in order to assess the possibility for their further utilisation. The samples were divided into 9 groups, which included coniferous tree cones, wood, and other multi-species logging residues. The elementary composition, ash content, and calorific value were determined as energy use indicators for the samples. Additionally, the content of heavy and alkali metals, which may affect combustion processes and pollutant emissions, was tested. The high content of heavy metals may also disqualify these residues for other uses. The research shows that the test residues are suitable for energy use due to their high calorific value and low content of heavy metals. However, an increased ash content in some samples and the presence of alkali metals, causing high-temperature corrosion of boilers, may disqualify them as a potential fuel in the combustion process. The forest residues may be used in other thermal processes such as pyrolysis or gasification. A low content of heavy metals and a high content of organic matter permit the use of these residues for the production of adsorbents or composite materials.

Theoretical insights into the poisoning effect of Na and K on α-Fe2O3 catalyst for selective catalytic reduction of NO with NH3

The poisoning effect of potassium (K) and sodium (Na) on the α-Fe2O3 catalyst in the ammonia-selective catalytic reduction (NH3-SCR) for the NO reduction was investigated by the density functional theory calculation. The results show that, in the presence of alkali metals, the strength of the Lewis acid site on the surface is not affected, while the strength of the Brønsted acid site is significantly inhibited, which thus decreases the de-NOx performance of the α-Fe2O3 catalyst. Both K and Na enhance the NOx (NO and NO2) adsorption capacity and inhibit the O2 adsorption capacity of the α-Fe2O3 catalyst. These data indicate that NO and NH3 form competitive adsorption, and the ‘Fast-SCR’ reaction is inhibited in the alkali metal poisoned systems. In addition, the alkali metals don't affect the dehydrogenation of NH3, but inhibit the formation of H2O which is the rate determination step of NH3-SCR for α-Fe2O3 catalyst.

A review on the migration and transformation of heavy metals influence by alkali/alkaline earth metals during combustion

Alkali/alkaline earth metals (AAEMs) are widely present in various solid fuels. During the combustion process, the AAEMs undergo complex physical and chemical reactions with heavy metals and other minerals in the fuel, thereby affecting the migration and transformation of heavy metals. This paper mainly introduced the influence of AAEMs on the migration and transformation of As, Se, Pb and Cr, including the influence of alkali metals and alkaline earth metals on the migration and transformation of heavy metals, and the influence of particle agglomeration and coherence on heavy metal emissions. AAEMs can inhibit the volatilization of heavy metals. The combination of alkali metals and Cl elements reduces the production of PbCl2. The presence of alkali metals is beneficial to improve the adsorption efficiency of kaolin for Pb. AAEMs can form stable compounds with As and Se. However, at the same time, it should be noted that in the partial combination products of AAEMs and Cr, Cr exists in a hexavalent state and has high toxicity. AAEMs play a role in promoting and inhibiting the occurrence of agglomeration, respectively. An appropriate content of alkali metals is beneficial to reduce the release of heavy metals. By summarizing the influence of AAEMs on the migration and transformation of heavy metals, it is hoped to provide ideas for reducing the harm of heavy metals.

Thermal behaviors and kinetics for fast pyrolysis of chemical pretreated waste cassava residues

Abstract In the present study, thermal decomposition behaviors and kinetics for fast pyrolysis of acid/alkali pretreated waste cassava residues were investigated. The results demonstrated that chemical pretreatments apparently loosened the compact structure of cassava residue and benefited to the sufficient contact with acid/alkali sites. Acid/alkali pretreatments enriched the product varieties and had remarkable influence on the adjustment of product formation. Particularly, the pyrolysis behavior obviously shifted to low-temperature zones for pretreated samples. Low heating rate significantly promoted the formation of anhydrosugars with 27% levoglucosan produced, while elevating heating rate contributed to furfural production. Some oxygenated-chemicals, such as acetic acid, hydroxyacetone and 4-hydroxydihydrofuran-2(3H)-one, were apparently formed in the presence of alkali metal. Noticeably, the generation of most gaseous products was restrained for those acid-impregnated cassava residues. Moreover, kinetic study suggested that the apparent activation energy for waste cassava residue pyrolysis was significantly lowered, further verifying the positive role of chemical pretreatments.

Effect of activators on hybrid alkaline binder based on tungsten mining waste and ground granulated blast furnace slag

This article illustrates the effects of different combinations of alkaline activator solutions (sodium silicate “SS”, sodium hydroxide, potassium hydroxide and dissolved waste glass powder in sodium hydroxide) as well as their concentrations and the Solid/Liquid ratios on the compressive strength development, and the microstructure of hybrid alkaline binder. The current study used a combination of tungsten mining waste mud (TMWM) (90 vt.%) and ground granulated blast furnace slag (GGBFS) (10 vt.%) as precursors. The obtained hybrid alkaline binder specimens were submitted by compressive strength tests. It was found out that the alkaline activator (KOH when mixed with SS) improves the compressive strength of the hybrid alkaline binders compared to the alkaline activator (NaOH mixed with SS), which depends on the presence of alkali metal K+ and Na+ cations. Moreover, the samples prepared by the alkaline activator (dissolved waste glass powder in NaOH mixed with SS) giving the highest compressive strengthof about 32.8 MPa at 28 days. From the results of XRD, TGA-DTGA, FTIR analyses, and the obtained microstructures of the hybrid alkaline binders it indicates the existence of a different reaction product formed during the alkaline activation such as C-S-H, N-A-S-H, C-A-S-H, and K-A-S-H type cementitious gels. In addition to these conventional gels, there was a formation of a complex mixture of (C, M)-A-S-H cementitious gels were (M = K, Na). The pore structure of hybrid alkaline binder was evaluated through mercury intrusion porosimetry (MIP). The pore structure of specimens was characterised by the total porosity, average pore diameter, pore size distribution as well as characteristic pore sizes. The MIP results indicate that the type of alkaline activators, solid/liquid ratios and the alkaline activators’ concentration have a specific impact on all characteristics of the pore structure of all the hybrid alkaline binders. Finally, the cost impact on the compressive strength for different activators was also analysed.

CO2 gasification of biogenic fuels in a dual fluidized bed reactor system

A 100 kWth dual fluidized bed steam gasification pilot plant has been developed at TU Wien to convert different types of biogenic fuels into a valuable product gas. In this paper, the conversion of different biogenic fuels in combination with the utilization of CO2 as alternative gasification agent was investigated in the mentioned pilot plant. For this purpose, five experimental campaigns were carried out aiming at the investigation of softwood as reference fuel, and rapeseed cake, bark and lignin as alternative fuels. Pure olivine as well as a mixture (90/10 wt%) of olivine and limestone were used as bed materials. The product gas compositions of the different biogenic fuels changed depending on the elemental composition of the biogenic fuels. Thus, a high amount of carbon in the fuel enhanced CO formation, whereas an increased content of oxygen led to higher CO2 contents. Additionally, the presence of alkali metals in the biomass ash favoured the production of CO. The addition of limestone enhanced the H2 and CO contents via the water gas shift reaction as well as steam and dry reforming reactions, but had no significant effect on tar contents. Overall, this paper presents the feasibility of the dual-fluidized bed gasification process of different biogenic fuels with CO2 as gasification agent.

Ageing of bio-oil and its fractions in presence of surfactants

This study reports the ageing characteristics of bio-oil and its fractions in presence of three surfactants including Span 80, IGEPAL CO890 and soap that have hydrophilic-lipophilic balance (HLB) values of 4, 17 and 18, respectively. The results show that Span 80 with a low HLB value has not led to phase separation of the bio-oil nor has noticeable effect on ageing characteristics of the bio-oil. IGEPAL CO890 and soap with high HLB values have led to phase separation of the bio-oil into dark and clear fractions. After accelerated ageing, both the bio-oil and the separated bio-oil fractions (dark or clear) have increased viscosities, average molecular weights, water contents and total acid numbers (TANs), e.g. with increases of ∼34.7%, 16.1%, 1.7% and 6.2% respectively for the bio-oil. Such increases are more in viscosity and average molecular weight (∼21.3% and 18.5% vs a maximum of ∼18.4% and 17.1%) but less in TAN (a maximum of ∼15.4% vs a maximum of ∼25.6%) for the dark fractions than the clear fractions. Soap has a more significant effect on bio-oil ageing compared to IGEPAL CO890, due to its basic nature, presence of alkali metals and the separation of fatty acids in bio-oil.