Addition Of Na2CO3 Research Articles

ВЛИЯНИЕ КАРБОНАТА НАТРИЯ НА ПРОЦЕСС ТВЕРДЕНИЯ ПОРТЛАНДЦЕМЕНТНОГО КОМПОЗИТА

The article enlightens a number of chemical transformations during hydration of Portland cement blended with sodium carbonate. Excess of ions CO3 in solution slows down the development of portlandite (calcium hydroxide) and provide intensive growth of calcium carbonate (calcite) crystals in hydrated cement, especially during the first day of hardening. It is shown that there are differences in strength between the solidified Portland cement mixture without and with the addition of Na2CO3. Soda modifies the procedure for the entry into the hydration reaction of the clinker components of the cement. With a certain increase in its content in the mixture, a slight increase in cubic strength for the dry-hardening specimens is also observed.

Influence of Na2CO3 and K2CO3 Addition on Iron Grain Growth during Carbothermic Reduction of Red Mud

Red mud is a by-product of alumina production from bauxite ore by the Bayer method, which contains considerable amounts of valuable components such as iron, aluminum, titanium, and scandium. In this study, an approach was applied to extract iron, i.e., carbothermic reduction roasting of red mud with sodium and potassium carbonates followed by magnetic separation. The thermodynamic analysis of iron and iron-free components’ behavior during carbothermic reduction was carried out by HSC Chemistry 9.98 (Outotec, Pori, Finland) and FactSage 7.1 (Thermfact, Montreal, Canada; GTT-Technologies, Herzogenrath, Germany) software. The effects of the alkaline carbonates’ addition, as well as duration and temperature of roasting on the iron metallization degree, iron grains’ size, and magnetic separation process were investigated experimentally. The best conditions for the reduction roasting were found to be as follows: 22.01% of K2CO3 addition, 1250 °C, and 180 min of duration. As a generalization of the obtained data, the mechanism of alkaline carbonates’ influence on iron grain growth was proposed.

Effect of alkali metal carbonate A2CO3 (A = Li, Na, K) on AC susceptibility and superconducting properties of YBa2Cu3O7−δ

The effect of alkali metal carbonate (A2CO3)x addition on YBa2Cu3O7−δ with A = K, Na and Li for x = 0, 0.3, 0.5 and 1.0 wt% has been investigated. XRD patterns showed a single YBa2Cu3O7−δ phase for all samples. The resistance versus temperature measurements showed that all samples exhibited metallic normal state behavior. The addition of Li2O3 suppressed the superconductivity of YBa2Cu3O7−δ more than Na2CO3 and K2CO3. The AC susceptibility measurements showed a decrease in Tcχ′ for Li2CO3 addition. Tcχ′ was not much affected with Na2CO3 and K2CO3 addition which was around 93–94 K for x = 0–1.0 wt%. However, Tcχ′ was very much suppressed in the Li2O3-added samples with Tcχ′ decreasing from 94 K for x = 0 to 83 K for x = 1.0 wt%. The peak temperature Tp of the imaginary part of the susceptibility χ″ shifted to lower temperatures for Li2CO3, Na2CO3 and K2CO3 addition. This indicated the intergranular coupling and flux pinning force were suppressed when alkali metal carbonate was added. This work also showed that alkali metals with smaller ionic radius, Li, suppressed superconductivity of YBa2Cu3O7−δ more than the larger ionic radius, Na and K.

Phagocytosis activity of three sulfated polysaccharides purified from a marine diatom cultured in a semi-continuous system

An efficient process has been developed for bioactive polysaccharide production and purification from a local diatom isolate, Halamphora sp. AQ4. First, a semi-continuous system with fixed harvesting frequency was employed to cultivate AQ4 for the production of cell mass and polysaccharides for more than 285 days with a high yield of biomass. Six cultivation sets are performed according to different harvesting volumes per 3 days with or without Na2CO3 supplement. The addition of Na2CO3 increases both cell mass and polysaccharide production. Furthermore, three different sulfated polysaccharides (PK1~PK3) were purified from the freshly-grown AQ4 diatoms following anion-exchange chromatography. Among them, polysaccharide PK3 not only has a high content of fucose and uronic acid, but also has a strong activity to stimulate murine macrophage cells and increase their phagocytosis rate up to 170%. This study demonstrates that diatom AQ4 is an important bioresource for the production of bioactive polysaccharides.

Rapid Nucleation of Reduced Graphene Oxide-Supported Palladium Electrocatalysts for Methanol Oxidation Reaction.

Small sized electrocatalysts, which can be obtained by rapid nucleation and high supersaturation are imperative for outstanding methanol oxidation reaction (MOR). Conventional microwave synthesis processes of electrocatalysts include ultrasonication, stirring, pH adjustment, and microwave irradiation of the precursor mixture. Ethylene glycol (EG), which serves as a reductant and solvent was added during the ultrasonication or stirring stage. However, this step and pH adjustment resulted in unintended multi-stage gradual nucleation. In this study, the microwave reduction approach was used to induce rapid nucleation and high supersaturation in order to fabricate small-sized reduced graphene oxide-supported palladium (Pd/rGO) electrocatalysts via the delayed addition of EG, elimination of the pH adjustment step, addition of sodium carbonate (Na₂CO₃), prior microwave irradiation of the EG mixed with Na₂CO₃, and addition of room temperature precursor mixture. Besides its role as a second reducing agent, the addition of Na₂CO₃ was primarily intended to generate an alkaline condition, which is essential for the high-performance of electrocatalysts. Moreover, the microwave irradiation of the EG and Na₂CO₃ mixture generated highly reactive free radicals that facilitate rapid nucleation. Meanwhile, the room temperature precursor mixture increased supersaturation. Results showed improved electrochemically active surface area (78.97 m² g-1, 23.79% larger), MOR (434.49 mA mg-1, 37.96% higher) and stability.

Simultaneous recovery of ammonium, potassium and magnesium from produced water by struvite precipitation

Unconventional oil and gas industries generate huge amounts of produced water (PW) containing high concentrations of potentially hazardous organic and inorganic contaminants. This study demonstrated the feasibility of simultaneously recovering NH4+, K+ and Mg2+ from PW by struvite precipitation after calcium pretreatment with Na2CO3 addition or CO2 stripping. Without pretreatment, calcium exhibited strong competition for phosphate through the formation of Ca3(PO4)2 precipitate. The pretreatment with a Ca2+:CO32− molar ratio of 1:1.2 achieved a relatively low loss rate of Mg2+ (31.3%) and high Ca2+ removal efficiency (95.9%). The results also revealed that the Mg/N/P molar ratio and solution pH had a remarkable effect on the struvite precipitation, while the seeding dosage and Na+ slightly influenced struvite formation. The combination of pH = 9.5 & Mg/N/P molar ratio = 1.5:1:1.5 was ideal for struvite recovery from PW, resulting in NH4+, K+ and Mg2+ recovery efficiencies of 85.9%, 24.8% and 96.8%, respectively. The results of X-ray diffraction and scanning electron microscopy further confirmed that the precipitates generated at this optimal condition were orthorhombic struvite. Moreover, along with the struvite recovery, no accumulation of heavy metals and organic contaminants was observed, indicating that the struvite quality was sufficient for field application. Furthermore, struvite recovery process was able to reduce the Microtox toxicity of PW towards Vibrio fischeri by 60%. Considering the low cost and relatively simple technology, struvite precipitation process has the potential to be used for large-scale applications for produced water treatment and resource recovery.

Thermodynamic possibilities of flue gas dry desulfurization, de-HCl, removal of mercury, and zinc compounds in a system with Na2CO3, Ca(OH)2, sulfur, and HBr addition

Dry methods of flue gas cleaning are usually based on calcium hydroxide or sodium bicarbonate (NaHCO3), which is “in situ” decomposed to active soda (Na2CO3). Together with acid gases also emissions of volatile heavy metals (e.g., mercury and some Zn-compounds) have to be reduced. Removal of both main forms of mercury (Hg0 and Hg2+) from the flue gas is dependent on chemical reactions and sorption processes at the temperatures below approx. 300 °C. In this theoretical study, attention was concentrated on the thermodynamics of gas–solid reactions (de-HCl and desulfurization), reactions of Hg/HgCl2 vapours and Zn-compounds, with soda and Ca(OH)2 in the presence of acid gases, and on effects of elemental sulfur and HBr addition. Influence of sorbents/additives and conditions (temperature, gas phase composition) on the equilibrium concentrations of gaseous and solid species was studied at temperatures 400–560 K (127–287 °C). Two types of alkaline solid sorbents have been theoretically analyzed: Na2CO3 and Ca(OH)2. The thermodynamic analyses involved systems with computations of gas/solid phase composition on a basis of assumption of solid phases with unit activities (stable, basic state). Application of the minimization of Gibbs energy for the chosen systems was used for the determination of equilibrium composition of gas and solid phases.

Rapid and Eco-Friendly Synthesis of Red Fluorescent Gold Nanoclusters for Sensing and Anti-Counterfeiting Applications

A rapid and eco-friendly synthesis method for the preparation of gold nanoclusters (Au NCs) with strong red emission has been developed. A one-pot microwave (MW) irradiation method yields bright red-emitting Au NCs, providing an easy route for the synthesis of fluorescent Au NCs without the need for a tedious operation, time-consuming procedure, or the use of toxic/corrosive agents and harsh conditions. The as-prepared Au NCs show a small-sized distribution, good dispersibility and a broad excitation band (from UV light to visible light). The optimal experimental conditions, including concentrations and order of addition of Na2CO3, bovine serum albumin (BSA), and HAuCl4and the time of MW irradiation, were investigated in detail. The as-synthesized Au NCs were well characterized by fluorescence spectroscopy, UV-Vis spectroscopy, infrared spectroscopy, high-resolution transmission electron microscopy-energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy and X-ray diffraction. Due to favorable photoluminescence features as well as minimal toxicity, the Au NCs could be applied to sensing, patterning and anti-counterfeiting. The Au NCs displayed strong red emission that was efficiently quenched by hydrogen peroxide (H2O[Formula: see text]. More strikingly, the obtained Au NCs were used as a fluorescent ink for producing luminescent handwriting and patterns, which may expand the potential applications of Au NCs in the fabrication of security inks.

Enhanced biohydrogen production from date seeds by Clostridium thermocellum ATCC 27405

Biohydrogen production from waste lignocellulosic biomass serves the dual purpose of converting waste into valuable products and alleviates waste disposal issues. In this study, waste date seeds were valorized for biohydrogen production via consolidated bioprocessing by Clostridium thermocellum ATCC 27405. Effect of various surfactants (PEG1000, surfactin, Triton X-100) and sodium carbonate (buffering agent) on biohydrogen production from the acid pre-treated substrate was examined. Among the various surfactants, addition of Triton X-100 resulted in the maximum biohydrogen yield of 103.97 mmol/L at an optimal dosage of 0.75% w/v. Triton X-100 supplementation favoured the production of ethanol and acetate as co-metabolites than butyrate. Addition of Na2CO3 to date seed fermentation medium at a concentration of 15 mM enhanced the biohydrogen production by 33.16%. Also, Na2CO3 buffering supported the glycolytic pathway and subsequent ethanol production than acetate/butyrate formation. Combined effect of the optimal dosages of Triton X-100 and Na2CO3 resulted in high hydrogen productivity up to 72 h (0.443 mmol/g h of H2) with a total increase in hydrogen yield of 40.6% at the end of 168 h, as compared to fermentation supplemented with Triton X-100 alone. Further analysis revealed that the combined effects of the additives resulted in better substrate degradation, favourable pH window and cell growth promotion which ensured enhanced hydrogen productivity and yield. Thus, the study highlights a novel stimulatory approach for enhanced biohydrogen production from a new substrate.

The impact of sodium carbonate on physico-chemical properties and cooking qualities of starches isolated from alkaline yellow noodles

The physicochemical and cooking properties of wheat starch isolated from alkaline yellow dough treated with sodium carbonate (Na2CO3; 0–3.2 g/100 g) were investigated. With increasing Na2CO3 addition, swelling power increased from 7.28 to 10.70 g/g. X-ray diffraction showed no changes in crystalline patterns while the relative crystallinity decreased from 30.11% to 23.13%. Differential scanning calorimetry results suggested that alkaline salt shifted the gelatinization peak of starch to higher temperatures. The values of pasting viscosity and pasting temperature in alkali-treated starch increased and decreased, respectively. Farinograph results revealed the strengthened structure of dough with alkali-treated starch that was manifested by an increase in the dough development time and dough stability time. Cooking loss and rehydration values of noodles prepared from alkali-treated starch increased by 42% and 36%, respectively. The results suggested that Na2CO3 affected starch crystalline structure, swelling power, gelatinization, pasting properties, starch-gluten interactions and cooking characteristics of noodle products.

Novel method and its mechanism of reconstruction of commercial alumina to homogeneous porous alumina composite material

Abstract In this study, a novel method for reconstruction of commercial alumina to a homogeneous porous alumina composite material (HPACM) using an alumina powder, boric acid, and Na2SO4 and Na2CO3 additives is proposed for the first time and experimentally evaluated in detail. The properties of the as-prepared porous materials and their formation mechanisms are investigated. Unlike the traditional complex methods for manufacturing of porous alumina including electrochemical anodisation of aluminium and chemical etching, the HPACM can be simply prepared through sintering and dissolution. Scanning electron microscopy and N2 adsorption–desorption isotherm analyses demonstrate the formation of the HPACM with a diameter distribution centred at ∼20 nm after the sintering and decomposition at high temperatures and dissolution at room temperature. Transmission electron microscopy and X-ray diffraction results show that the main components of the as-prepared HPACM are alumina and sodium aluminate. The formation of the HPACM is attributed mainly to the reactions between the alumina powder, boric acid, and Na2SO4 and Na2CO3 additives at high temperatures and dissolution of the intermediate product of sodium aluminate at room temperature. A NaCl additive does not contribute to the formation of the intermediate product during the sintering process, owing to its considerable vapour loss at low temperatures. Moreover, a nanoindentation test shows that the HPACM has a good mechanical strength.

A low‐cost and efficient pathway for preparation of 2D MoN nanosheets via Na2CO3‐assisted nitridation of MoS2 with NH3

AbstractIn this paper, an efficient and low‐cost method was developed for producing isolated 2D MoN nanosheets via Na2CO3‐assisted nitridation and exfoliation of natural 2H‐MoS2 by NH3 at 700‐800°C. It was found that, in the presence of Na2CO3, the nitridation of MoS2 with NH3 was a topochemical transformation. After heat treatment the mixture of MoS2 and Na2CO3 in NH3 at 700‐800°C, layered MoN with intercalated Na2S was obtained. Na2CO3 can dramatically promote the topochemical nitridation and exfoliation of MoS2 in NH3. At 750°C, the time for complete nitridation of (commercial) MoS2 can be shortened to 2 hours, which is much shorter than 40 hours in the case without the addition of Na2CO3 as reported in the previous literature. After acid‐washing, the intercalated Na2S was removed, and the generated H2S promoted the further separation of the MoN nanosheets. Finally, dispersed high crystalline 2D MoN nanosheets with thickness of a few nanometers were successfully produced. This method may be also applicable for the production of other 2D nitrides or carbides by nitridation or carbonization of various transition metal dichalcogenides (TMDs) with the assistance of sulfur‐fixed agent.

Effect of Roasting Characteristics of Vanadium-Rich Slag on Its Vanadium Leaching Behavior

The effect of the roasting characteristics of vanadium-rich slag on its vanadium leaching behavior was investigated to enable its effective utilization. Thermodynamic analysis of the sodium roasting of vanadium-rich slag was performed for the first time. The effect of the roasting temperature, roasting time, quantity of sodium carbonate (Na2CO3) added, and particle size of the raw material on the vanadium leaching was studied. The results showed that the oxidation reactions of vanadium oxides, fayalite (Fe2SiO4), and vanadium-iron spinel (FeV2O4), and the formation of sodium vanadate were feasible within the roasting temperature range. The sodium roasting was significant for the subsequent vanadium leaching process. The optimum process conditions for sodium roasting were roasting temperature of 850°C, roasting time of 60 min, Na2CO3 addition of 20%, and particle size of − 74 μm, resulting in an ideal vanadium leaching ratio. The results of the current study provide experimental evidence to establish a correlation between the roasting characteristics of vanadium-rich slag and its vanadium leaching behavior, as well as a theoretical and technical basis for effective utilization of vanadium-rich slag.

Silica, Alkali Carbonate and Alkali Rich Metal Ore as Additive Effect on the Carbothermic Reduction Process of Phosphorus Ore

The phosphorus production industry is energy-intensive, which is one of the major reasons phosphorus has lower yields through furnace production. In this study, phosphorus conversion rate from phosphorus ore was investigated using four different fluxing agents: silica, potassium shale, potassium feldspar, and nepheline. Different holding times (10, 20, 30, and 40 min), acidity values (0.68, 0.88, 1.02, 1.42, and 2.02), coal surplus coefficients (1.05, 1.25, 1.5, 2, and 2.5), and calcination temperatures (1250 °C, 1300 °C, 1350 °C, 1400 °C, and 1450 °C) were studied. The results demonstrated that potassium shale, potassium feldspar, and nepheline as new fluxing agents improved phosphorus conversion rate under the same experimental conditions. To further ensure the significance of the experiment, the conversion rate of phosphorus from phosphorus ore was also investigated without an additive and with the addition of Na2CO3 and K2CO3. The slag viscosity of different fluxing agents and different additives at high temperatures was analyzed via the spread area method. To investigate the mechanism of phosphorus conversion, silica and nepheline as fluxing slag at different calcination temperatures were analyzed using X-ray diffraction.

Understanding the roles of activators towards setting and hardening control of alkali-activated slag cement

Sodium silicate-activated slag often gives high early strength but sets too rapidly. Commercial retarders for Portland cement and partial replacement with other cementitious components in alkali-activated slag (AAS) system have been proven ineffective. This study investigated the approach of controlling setting by altering activator ion composition and silica polymer status. The roles of activators during the alkali-activation process were studied via pore solution chemistry analysis and microstructural analysis of hydration products. The addition of Na2CO3 does not, but NaOH does alter the polymerization of silicate ion groups in sodium silicate solution due to the increases in pH and Na2O concentration. The specific effects of Na2CO3 on the setting and hardening of AAS depend on the relative contents of NaOH and Na2O·2SiO2 in alkaline solution. The reaction degree of AAS is dependent on activator compositions, which govern the kinetics of formation and intrinsic characteristics of the reaction products calcium aluminosilicate hydrates. The setting and strength development of sodium silicate-activated slag can be controlled by manipulating the compositions of Na2CO3-NaOH-Na2O·2SiO2.

Promotive Effect of Bicarbonate Ion on Two-Electron Water Oxidation to Form H2 O2 Catalyzed by Aluminum Porphyrins.

Two-electron water oxidation initiated by one-electron oxidation of aluminum porphyrins (AlTMPyP) is an alternative water oxidation to the conventional four-electron pathway and could help to avoid the bottleneck subject of photon-flux density in artificial photosynthesis. Here, a dramatic enhancement of the reactivity by bicarbonate ion in the two-electron water oxidation to form H2 O2 is reported. An addition of sodium carbonate (Na2 CO3 ) controlled both catalytic current and product selectivity of the two-electron water oxidation to enhance the activity of AlTMPyP at pH≈10-11. Controlled potential electrolysis experiments at different concentrations of Na2 CO3 (10-100 mm) showed that peroxide selectivity was improved up to approximately 73 % by the increase of [Na2 CO3 ] added to the system. The promotion of the reaction cycle was induced by an enhanced dynamic capturing of H2 O2 from the hydroperoxy complex of AlTMPyP through an attack of a bicarbonate ion. The detailed electrochemical studies and product selectivity indicated that the bicarbonate ion served as a good cofactor for producing H2 O2 from water. At stronger alkaline conditions (pH 12.5), however, a retardative effect of the addition of Na2 CO3 on the catalytic reactivity was observed.

Refractory/steel/inclusion interactions in Al-deoxidised valve spring steel treated with Na2CO3

ABSTRACTCa treatment is generally used in the production of Al-deoxidised steel to prevent nozzle blockage by modifying high melting point inclusions such as MgO·Al2O3 (Melting point: 2408 K). However, the successful application of Ca treatment can be quite difficult due to the requirements for stringent control of the amount of calcium that is added. In the present paper, a novel and effective method of inclusion modification by Na2CO3 treatment is developed and the evolution process of inclusions in Al-deoxidised steel with Na2CO3 treated is studied, which is in good agreement with FactSage calculation results. In addition, the relevant refractory/steel/inclusion interaction mechanisms are also discussed. The experimental results show that MgO–Al2O3 inclusions can be transformed into Na2O–MgO–Al2O3–SiO2 inclusions with low-melting points by Na2CO3 treatment. After Na2CO3 addition, both the dissolved [Na] and [Si] start to reduce MgO and Al2O3 in the generated MgO–Al2O3 inclusions from outside to inside, accompanied with the reduction of MgO–Al2O3 reaction layer at the steel-refractory interface by [Na] and [Si] in the steel.

Study on extraction of rare earth elements from coal fly ash through alkali fusion – Acid leaching

The growing demand for rare earth elements (REEs), which play vital roles in the production of technologically advanced products, has stimulated the development of original processes to recover REEs from secondary resources. Coal fly ash (CFA), as the main byproduct of coal combustion, enriches REEs in some areas of the world. In this paper, a two-stage hydrometallurgical process (alkali fusion-acid leaching) was developed to recover REEs from CFA. The CFA was firstly roasted at high temperature with Na2CO3 addition, followed by the leaching step. The effects of parameters of the alkali fusion and acid leaching on REEs extraction were investigated. Results indicated that the two-stage method was more efficient compared with direct leaching method. Optimum conditions of alkali fusion were 1:1 (mass ratio of CFA/Na2CO3), heating in 860 °C for 0.5 h. The 72.78% leaching REEs efficiency can be obtained in the optimal operation conditions: leaching time (2 h), stirring speed (400 rpm), the HCl concentration (3 mol/L) and the solid-liquid ratio (1/20). This study should be useful in developing a strong theoretical foundation and technological support for the enrichment and extraction of REEs.

Transition-Metal-Free Allylic Borylation of 1,3-Dienes.

This work explains the reactivity of diboron reagents with 1,3-dienes in a transition-metal-free context. The sole addition of Na2CO3 (30 mol %) to bis(pinacolato)diboron in MeOH allows the 1,4-hydroboration of cyclic and noncyclic 1,3-dienes. The electronic influence on the substrate guarantees the conjugated 1,4-hydroboration versus 1,2-diboration. DFT calculations show that the distribution of charge in the allylic anion intermediate governs the selectivity toward 1,4-hydroboration, while the favored trans configuration in diene reagents determines the preference for the E allyl boronate products.

Microwave sodium roasting (MWSR) spent HDS catalysts for recovery Mo and in situ sulfur fixation

Abstract The heat pretreatment of the spent hydrodesulfurization (HDS) catalysts plays an important role in its comprehensive recycling. In this work, the microwave sodium roasting (MWSR) strategy was used for the heat treatment of the spent catalyst, with the aim of achieving effective separation of Mo and Al while achieving in-situ sulfur fixation. Specifically, the de-oiled, spent HDS catalyst was roasted with Na2CO3 by microwave heating in air, followed by hot water leaching. Based on the thermodynamic analysis, the effects of microwave heating temperature, holding time and Na2CO3 addition on the recovery of molybdenum have been thoroughly investigated. Owing to the special heating method of microwave, the spent catalyst after roasting has a microstructure suitable for leaching, and S is more in situ converted to Na2CO3. After following the strategy, the leaching degree of Mo can reach 99%, while the leaching degree of Al is less than 8%, which indicates that Mo and Al are effectively separated. More importantly, a sulfur fixation degree of 79.1% was obtained. This strategy provides a novel reference for the harmless treatment of spent HDS catalysts.