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Near-neutral salt activated slag cement has better performance in environmental protection and shrinkage behavior than common sodium silicate -activated slag (AAS) cement. However, the growth of mechanical performance is too slow, which limits its application. Reactive MgO can improve early mechanical properties, while it may have different effects on the shrinkage due to changes in alkali-activators. Two near-neutral salts, sodium carbonate (SC) and sodium sulfate (SS), were selected to prepare AAS cement. The influence of reactive MgO on autogenous and drying shrinkages was studied. The hydration process and pore structure were assessed with hydration heat and nitrogen adsorption, respectively. The phase composition was evaluated by thermogravimetry (TG/DTG) and X-ray diffraction (XRD). The results indicate that the addition of reactive MgO increases the autogenous shrinkage of SC and SS activated slag. This is mainly due to accelerated reaction by reactive MgO. The drying shrinkage of AAS mortars activated with SC increases first and then decreases with the increase in reactive MgO. For SS activated slag, the more the reactive MgO used, the lower the drying shrinkage is observed. This is related to the effect of reactive MgO on pore structure and hydration products. When reactive MgO increases from 2% to 10%, the mesopore in SC activated slag increases at first and then decreases, while the SS activated slag group shows a constant decrease. Reactive MgO promotes the formation of hydrotalcite in SC activated slag, while AFt is found in SS activated slag. Hydrotalcite and AFt are crystalline products, which are beneficial to inhibit drying shrinkage.

Na2Ti3O7 has attracted much attention in the field of anode materials for Na-ion batteries thanks to its non-toxicity and very low working potential of 0.3 V vs Na0/Na+. Building a clearer picture of its formation from cheap Na2CO3 and TiO2 starting materials is therefore of obvious interest. Here, we report new insights from an in-situ high temperature X-ray diffraction study conducted from room temperature to 800 °C, complemented by ex-situ characterizations. We were thereby able to position the previously reported Na4Ti5O12 and Na2Ti6O13 intermediate phases in a reaction scheme involving three successive steps and temperature ranges. Shifts and/or broadening of a subset of the Na2Ti6O13 reflections suggested a combination of intra-layer disorder with the well-established ordering of successive layers. This in-situ study was carried out on reproducible mixtures of Na2CO3 and TiO2 in 1:3 molar ratio prepared by spray-drying of mixed aqueous suspensions. Single-phase Na2Ti3O7 was obtained after only 8 h at 800 °C in air, instead of a minimum of 20 h for a conventional solid-state route using the same precursors. Microstructure analysis revealed ~ 15 µm diameter granules made up from rectangular rods of a few-µm length presenting electrochemical properties in line with expectations. In the absence of grinding or formation of intimate composites with conductive carbon, the specific capacity of 137 mAh/g at C/5 decreased at higher rates.

Sodium carbonate (SC) activated ground granulated blast-furnace slag (GGBS) and fly ash (FA) is a potential substitute of traditional cement with ultra-low carbon footprint. However, its hydration rate and strength growth are limited, owing to the slow leaching of ions during the activation of weak base. In this work, 60% wet-grinded GGBS and 40% FA were blended as the binder, and two organic alkalis, i.e. triethanolamine (TEA) and triisopropanolamine (TIPA), were adopted to facilitate the ions dissolution and pozzolanic reaction of SC activated GGBS-FA blended cementitious material (SCSF). The compressive strength was tested and the hydration kinetics was studied by hydration heat and chemical shrinkage. Besides, ions leaching behavior was characterized by ICP; hydrates and microstructure were also detected by XRD, TG-DTG and SEM. Results indicated that the addition of TEA or TIPA significantly promoted the ions dissolution. 0.05% TEA increased the concentration of leached Ca2+, Al3+ and Fe3+ by 36%, 33% and 1545%, respectively. This solubilizing effect was also found in TIPA. Moreover, these two chemicals could promote the formation of hydrates, such as C-S(A)-H gel, hydrotalcite, calcite and aragonite, especially at the early period; these also activated the hydration process of SCSF effectively, and the compressive strength of the mortar reached above 40.0 MPa at 7 d and 48.0 MPa at 28 d. The carbon emission of the designed system is 85.9% and 55.9% lower than that of PC and strong base activated GGBS system, respectively.

As solid waste posing a great threat to the environmental system, the disposal of arsenic-alkali slag has become the top priority in the development of the antimony industry. In this paper, a novel technological scheme combining the advantages of chemical precipitation and fractional crystallization is proposed for the safe disposal and resource utilization of arsenic-alkali slag. The scheme is mainly composed of three parts, namely, leaching of arsenic-alkali slag, selective removal of arsenic in the arsenic-alkali solution, and evaporation crystallization of alkali solution. In the leaching part, the optimum leaching parameters are determined by orthogonal tests. In the arsenic and alkali separation part, based on thermodynamic analysis, the selective removal of arsenic from arsenic-alkali solution is realized by forming ammonium magnesium arsenate (MgNH4AsO4) precipitation. In the evaporation crystallization part, the crystalline product with sodium carbonate (Na2CO3) content of 89.87% is obtained by the evaporation crystallization experiment. The whole process does not produce secondary pollution and realizes the reuse of wastewater. The final products are leaching residue, arsenic slag, and sodium carbonate with an arsenic content of 0.83%, 24.93%, and 0.18%, respectively.

Carbon quantum dots (CQDs) with an average diameter of 3 nm, exhibiting blue photoluminescence, have been obtained from commercial conductive carbon black by a cost-effective and straightforward exfoliation method using dry ball milling in the presence of sodium carbonate. As a secondary abrasive medium, sodium carbonate provides effective exfoliation of carbon black with a high degree of CQD graphitization and plays an essential role in the functionalization of CQDs with oxygen groups. Due to the low toxicity of CQDs against HeLa cancer cells (cell viability above 90% at a CQD concentration of 200 μg cm−3) and the ability to penetrate cells and emit blue light, CQDs are possibly suitable for biological imaging of cells.

In present study, sodium carbonate (Na2CO3) and ammonium carbonate ((NH4)2CO3) are separately selected as precipitant to synthesize the strontium oxide (SrO) based solid catalyst, namely, SrO–M/Na and SrO–M/NH4 for biodiesel production through transesterification. The influence of precipitant on catalyst physicochemical property, catalytic activity as well as reusability are investigated and compared. To begin with, transesterification parameters of catalyst amount, molar ratio of methanol to oil, reaction time, and reaction temperature are concerned to comprehensively evaluate catalytic performance of the two catalysts. Moreover, catalyst reusability is evaluated under the optimal conditions. With catalyst amount of 4 wt.%, molar ratio of methanol to oil of 9 at 65 ℃ within 30 min, SrO–M/Na exhibits a better catalytic activity in comparison to SrO–M/NH4, whereas, the reusability is in reverse sequence. In order to reveal the reason behind, catalysts are characterized by thermogravimetric/differential thermogravimetric/scanning calorimetry (TG/DTG/DSC), X–ray diffraction (XRD), X–ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), N2–adsorption/desorption, basic strength, basicity and vibrating sample magnetometer (VSM).

3D ink printing (3DIP) technology can accurately control the macroscopic size and microstructure of bioceramic scaffolds. However, nonceramic components in the printing ink used in 3DIP severely affect densification, resulting in less desirable mechanical properties of the scaffolds. In this study, a strategy of sintering assisted by a sintering aid (sodium carbonate) was used to prepare calcium silicate (CSi) scaffolds with high strength. The addition of 1% sintering aid to a CSi scaffold sintered at 1100 °C led to an appreciable compressive strength (47.8 MPa) and high elastic modulus (1847 MPa). Moreover, the CSi scaffolds with sintering aids showed better degradation ability and mineralization ability than the CSi scaffolds without sintering aids. It is expected that the method involving strengthening with sintering aids will promote the application of 3DIP bioceramic scaffolds in the repair of bone defects.

Sodium carbonate pretreatment, an environmentally-friendly and efficient pretreatment, was used to improve solid-state ethanol production from corn stover (CS). To further enhance ethanol yield from the pretreated CS, especially at low enzyme loadings, a combined pretreatment, including steam and sodium carbonate pretreatments, was developed. The removal/modification of lignin by sodium carbonate pretreatment (at 100 °C for 3 h) helped to obtain high ethanol titer at high solids and low enzymes loadings. The maximum ethanol concentration was about 44 g/L, obtained after 72 h simultaneous saccharification and fermentation (SSF) of CS pretreated with sodium carbonate without mixing and prehydrolysis at 30% solid and 15 FPU/g enzyme loadings. Applying prehydrolysis and increasing the SSF time to 120 h improved ethanol concentration to 59 and 67 g/L, respectively. Steam pretreatment at 190 °C for 10 min before sodium carbonate pretreatment led to 76% increase in ethanol concentration. At the enzyme loading of only 5 FPU/g substrate, the modified pretreatment increased the ethanol concentration from 24 g/L to 41 g/L, compared with that of sodium carbonate pretreatment. The results showed that hemicellulose removal and delignification by steam and sodium carbonate pretreatment, respectively, considerably improved ethanol concentration at high solids and low enzyme loadings.

Capturing flue gases often require multiple stages of scrubbing, increasing the capital and operating costs. So far, no attempt has been made to study the absorption characteristics of all the three gases (NO, SO2 and CO2) in a single stage absorption unit at alkaline pH conditions. We have attempted to capture all the three gases with a single wet scrubbing column. The absorption of all three gases with sodium carbonate solution promoted with oxidizers was investigated in a tall absorption column. The absorbance was found to be 100% for CO2, 30% for NO and 95% for SO2 respectively. The capture efficiency of sodium carbonate solution was increased by 40% for CO2 loading, with the addition of oxidizer. Absorption kinetics and reaction pathways of all the three gases were discussed individually in detail.

Graphical abstract, Fully inactivating SARS-CoV-2, the virus causing coronavirus disease 2019, is of key importance for interrupting virus transmission but is currently performed by using biologically or environmentally hazardous disinfectants. Herein, we report an eco-friendly and efficient electrochemical strategy for inactivating the SARS-CoV-2 using in-situ formed nickel oxide hydroxide as anode catalyst and sodium carbonate as electrolyte. At a voltage of 5 V, the SARS-CoV-2 viruses can be rapidly inactivated with disinfection efficiency reaching 95% in only 30 s and 99.99% in 5 min. Mass spectrometry analysis and theoretical calculations indicate that the reactive oxygen species generated on the anode can oxidize the peptide chains and induce cleavage of the peptide backbone of the receptor binding domain of the SARS-CoV-2 spike glycoprotein, and thereby disables the virus. This strategy provides a sustainable and highly efficient approach for the disinfection of the SARS-CoV-2 viruliferous aerosols and wastewater.

We investigated the discharge characteristics, parameters, water content, and mechanism of liquefying biomass by plasma electrolysis under alkaline conditions. Compared with the liquefaction of sawdust under acidic conditions, the discharge changed from corona to spark discharge, the liquefaction time was a little longer (8 min), and the pondus Hydrogenii (pH) of the bio-oil was 7.54 under sodium hydroxide catalyst. We identified the optimal parameters for sawdust liquefaction by sodium hydroxide, sodium carbonate, and sodium bicarbonate using a single factor method and found that the optimal parameters for sodium hydroxide and carbonate were quite different, apparently because they have different liquefaction mechanisms. When the water content increased, the liquefaction rate remained constant, so the water content prolonged the treatment time but did not affect the liquefaction rate or product quality. To analyze the universality of liquefied cellulose biomass under alkaline conditions, corn cob, rice straw, and cotton were liquefied separately. We found that the liquefaction time increased significantly with an increase in cellulose content. Notably, plasma electrolytic liquefaction efficiently heated the solution and effectively catalyzed the liquefaction of biomass with high energy efficiency, making this a promising biomass conversion technology.

In the present study, bio-oil and biochar have been produced from microwave-assisted catalytic pyrolysis of corn stover (CS). The effects of microwave power (MWP) and mixing of sodium carbonate as a catalyst at different ratios have been examined. Both MWP and the catalyst improved the heating and increased the maximum temperatures of pyrolysis process. Rise in MWP increased the gas yield but decreased the biochar yield, while the bio-oil yield was not significantly affected. The use of catalyst increased the bio-oil yield and enhanced its properties. Increase in the ratios of catalyst from 10% to 30%, did not contribute a significant effect either on the yield or on the properties of the products. The water content in bio-oil was found to be in the range of 53.09–73.79%, while the minimum viscosity was observed to be 3.31 mPa s. The maximum higher heating value (HHV) of bio-oil and biochar were 13.17 MJ/kg and 29.77 MJ/kg respectively. The bio-oil samples were characterized chemically by a gas chromatography-mass spectrometry (GC-MS) and Fourier transform infrared spectroscopy (FTIR). Most of the chemical group compounds in the bio-oil were identified to be alcohol, phenols, alkynes, acids, and aromatic. The net energy recovery from the raw CS was in the range of 28.29–42.97%.

According to the Chinese traditional black jelly production process, a critical step to ensure the quality of jelly is to add alkali to it. In this study, the effects of sodium carbonate (Na2CO3) and sodium bicarbonate (NaHCO3) on the pasting, rheological, textural, and structural properties of sweet potato starch (SPS)-Mesona chinensis Benth polysaccharide (MCP) gels were evaluated. Adding Na2CO3 at low concentration reduced the final viscosity (FV) of SPS-MCP gels, whereas adding it at a high concentration increased the FV. Adding NaHCO3 can increase the FV of SPS-MCP gels in a concentration-dependent manner. Rheological results indicated that adding NaHCO3 at a low concentration decreased the storage modulus of SPS-MCP gels, whereas adding it at a high concentration increased the storage modulus. The storage modulus of SPS-MCP gels increased with increasing concentration of NaHCO3. The addition of Na2CO3 and NaHCO3 improved the textural properties of SPS-MCP gels and decreased the water mobility. Infrared results indicated that adding alkali can enhance the hydrogen bonding between SPS and MCP. Scanning electron microscopy results suggested that alkali can reduce the size of gels, and make the structure more compact.

2-Amino-5-mercapto-1,3,4-thiadiazole (M1) was prepared by the cyclization of thiosemicarbazide with carbon disulfide and anhydrous sodium carbonate in ethanol. The compound (M1) was used as precursor to react with different aromatic aldehydes to yield hydrazones (M2-M4). Thereafter, hydrazones (M2-M4) is reacted with chloro acetyl chloride to obtain 5-(sub. benzylidene) amino]-2-thioacetyl chloride-1,3,4-thiadiazole compounds (M5–M7). The compounds (M8–M10) and (M11–M13) were synthesized by the reaction of compounds (M5–M7) with benzotriazole or Indole, respectively. All the synthesized compounds were identified according to their physical properties, spectroscopic data (FT-IR). At the same time, some of these prepared compounds were identified by the use of 1H NMR spectroscopy. In addition to the systematic identification of some active functional groups in these compounds. Biological activity for some of the synthesized compounds was evaluated against two types of bacterial and two types of fungal.

The current study was conducted to assess the groundwater for irrigation purposes in the village of Ein Al-Husaan in Talafar district in Nineveh Governorate, based on the Water Quality Index (WQI) as an effective method for determining the suitability of water for irrigation. Ten wells were selected for five months with a sample site for each month and some physical, chemical, and biological tests were performed that include: pH, EC25, bicarbonate, chloride, and F. colif. In addition to calculating the irrigation coefficients of % Na, SAR (Sodium Adsorption Ratio), KR (Kelly Ratio), MAR (Magnesium Adsorption Ratio), RSC (Residual Sodium Carbonate), PI (Permeability index), and PS (Potenial Salinity), the results showed that the PS was higher than the permissible limits for irrigation as a result of the passage of water with the rocks of evaporators that contain sulfates, while the water quality index ranged between (54.83–61.58). This indicates that all the water from wells was of good quality according to the classification.

We report the synthesis of nanocrystalline calcium carbonate with varying particle sizes by precipitation techniques from an aqueous solution of calcium nitrate and sodium carbonate at controlled pH. The particle size of the carbonate powder was precisely controlled by changing the precursor concentration. The synthesized carbonate powders were characterized by using scanning electron microscopy, X-ray diffraction technique, and transmission electron microscopy. The particle size, along with the crystallite size of as-synthesized carbonate powder, decreases with increasing precursor concentration. The non-isothermal decomposition kinetics of the carbonate powder was also evaluated by using near to the modified Arrhenius equation's exact solution. The experimental results were best fitted at n = 0.5, and the one-dimensional diffusion-controlled transport process mechanism (D1) and one-dimensional phase boundary movement mechanism (R1) was found to be very close fit of the corresponding evaluated g(α) value. The apparent activation energy of the nano calcium carbonate decomposition was found in the range of 120–175 kJ/mol, which is also inherently functioning with the average particle size. The apparent activation energy of decomposition of CaCO3 found to be decreased with decreasing average particle size of nanocrystalline calcium carbonate.

The co-presence of geopolymers and cellulose in clay-based materials could improve their performances. Thus, cured NaOH-activated heated clay-cellulose (up to 10 mass%) composites were prepared, and their microstructural characteristics were investigated. Moreover, the effect of waste glass addition on the composites characteristics was evaluated. The results showed that zeolite (chabazite) and sodium carbonate were formed from metakaolin and by carbonation respectively, and the zeolization process slowed down after 5 days of curing because of ions immobilization. The coating of metakaolin particles by the amorphous cellulose II-Na formed reduced drastically the formation of zeolite. The presence of cellulose II-Na resulted in the porosity decrease, and consequently the mechanical strength and density enhanced. The results also showed that the kinetics of water absorption by the composites followed the pseudo-first order equation, and the rate constant was found to be 4.3 × 10−3 s−1. Moreover, the reinforcing effect of the cellulose fibbers was annihilated by the formation of glass derivatives. Resumen: La co-presencia de geopolímeros y celulosa en materiales a base de arcilla podría mejorar sus rendimientos. De este modo, se prepararon compuestos de arcilla-celulosa calentada activados con NaOH (hasta un 10% en masa) y se investigaron sus características microestructurales. Además, se evaluó el efecto de la adición de residuos de vidrio sobre las características de los composites. Los resultados mostraron que la zeolita (chabasita) y el carbonato de sodio se formaron a partir de metacaolín y por carbonación, respectivamente, y el proceso de zeolización se ralentizó después de 5 días de curado debido a la inmovilización de iones. El recubrimiento de partículas de metacaolín por la celulosa amorfa II-Na formada redujo drásticamente la formación de zeolita. La presencia de celulosa II-Na resultó en la disminución de la porosidad y, en consecuencia, la resistencia mecánica y la densidad aumentaron. Los resultados también mostraron que la cinética de la absorción de agua por los compuestos siguió la ecuación de pseudo primer orden, y se encontró que la constante de velocidad era 4,3 × 10−3 s−1. Además, el efecto de refuerzo de las fibras de celulosa fue aniquilado por la formación de derivados de vidrio.

It was shown by ATR FTIR, XRD and 11B MAS NMR methods that increasing contents of sodium polyborate and sodium carbonate impurities were formed in solid sodium borohydride upon its storage and contact with the air. To increase the NaBH4 purity after storage, it was re-crystallized in diglyme using the well-known Brown's procedure. The purification efficiency was further improved by ammonia treatment during NaBH4 dissolution. It was found that the advantages of using the gaseous ammonia consisted in an increased NaBH4 solubility in diglyme and a more efficient reduction in the content of impurities to form a material consisting of uniform highly dispersed particles of the hydride having a regular cubic shape. It was found for the process of catalytic hydrolysis of NaBH4 that the rate of hydrogen generation and its yield increased with the decreasing content of impurities. These results demonstrate the importance of investigations aimed at improving the existing methods of NaBH4 purification and creating new ones.

The ionic electrolyte and compatible cathode are major challenges to develop advanced low temperature solid oxide fuel cells (LT-SOFCs). Perovskite La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) has considered as desired SOFC cathodes due to its unique advantages including high mixed electronic and ionic conductivity and excellent catalytic activity for oxygen reduction reaction. Our present work demonstrates the first application of LSCF tuned as functional electrolyte through composing with sodium carbonate. The mixed ionic and electronic conductor (MIEC)/carbonate LSCF/Na2CO3 nanocomposites can make use of the intrinsic high ionic conductivity of LSCF, and extend the three phase electrocatalytic reaction region into the electrolyte region along with suppress its electronic contribution, ultimately tuned as functional electrolyte material. Through optimizing Na2CO3 content, the novel LSCF/Na2CO3 nanocomposite gives rise to an superior fuel cell performance of 700 mW/cm2 at 550 °C. This work has demonstrated a new approach to develop electrolyte materials tuned from MIEC for advanced LT-SOFCs for next-generation.

Thermal decomposition and phase transformation for the mixture of Bayan Obo rare earth concentrate (BORC) and sodium carbonate (Na2CO3) roasted at different temperatures with weight ratio of 100:20 were studied in detail in our study. The aim of our study is to reveal the nature of roasting reaction between BORC and Na2CO3 and thus providing a new method for processing BORC. The results indicate that BORC can be decomposed completely with Na2CO3 at around 600 °C after 3 h. During the calcination process, Ce0.5Nd0.5O1.75, NaF, Na3PO4, and a rare earth double phosphate phase Na3RE(PO4)2 are formed after the decomposition of BORC with Na2CO3. In addition, the thermal decomposition mechanism is determined in the paper. Based on these facts, a clean technique processing BORC was developed. And a CeF3 powder, whose composition was measured and stability was also evaluated, was obtained for some potential application from the new technique. This research is of significance in terms of the Na2CO3-roasting BORC solid reaction study and sheds a light on a potential clean technique for BORC.

Sodium titanate nanotubes (STN) modified by the addition of sodium carbonate (3–10 wt. %) were tested as catalysts for the transesterification of soybean oil with methanol giving good results. Prepared catalysts were characterized by N2 physisorption, X-ray diffraction, FT-IR, temperature-programmed desorption of CO2, scanning and transmission electron microscopy. The STN catalysts modified with sodium carbonate were significantly more active in the transesterification reaction than the reference catalyst containing 5 wt. % of Na2CO3 on alumina. The most active catalyst, STN with 10 wt. % of Na2CO3, resulted in the 97% yield of methyl esters at a short reaction time (30 min) in mild conditions (80 °C). High activity of the prepared catalysts was attributed to a synergetic effect between the support and the deposited sodium carbonate leading to a noticeable increase in the amount of strong basic sites able to generate methoxide anions required for the transformation of triglycerides to methyl esters. According to the FT-IR characterization, the above synergy was attributed to the presence of different types of carbonate species in the alumina and STN-supported catalysts. Upon reutilization, Na2CO3-containing STN catalysts showed a decrease in their activity due to leaching of the active phase in the reaction media.

Porous alumina bodies, intended for use as heat-insulating refractory materials, were fabricated by a high-temperature evaporation method and characterized. A series of flux systems was used by adding a third component to Na2O–B2O3 glass in addition to boric acid and sodium carbonate. When SiO2 was added as the third component, the primary alumina particles grew anisotropically, forming a plate-like shape, and the house-of-cards structure was self-organized. The anisotropic growth of alumina platelets was promoted by the solid solution of Si4+ ions in the flux on the α-Al2O3 surface. Furthermore, the bonding between the alumina platelets was strengthened by the high-SiO2-concentration flux. Our typical alumina body had a porosity of 71.5%, a compressive strength of 3.7 MPa, a shrinkage rate of 2.6% when reheated at 1700 °C, and a thermal conductivity of 0.24 W m−1•K−1 at 1000 °C. Thus, the present alumina bodies are expected to find application as high-performance heat-insulating refractory materials.

Lubrication is vital in enabling the key machinery contact components to operate durably and reliably at extremely high temperatures for space aviation and metal forming. In this work, the expanded graphite in sodium metasilicate solution as high temperature lubricant was evaluated using a ball-on-disc tribometer. The results suggest that the use of this mixture can remarkably reduce the friction and wear of steel counterparts by up to 85% and 60% at 850 °C, respectively, compared with unlubricated condition. These improvements result from the formed tribo-layer containing amorphous carbon and sodium carbonate melt, as well as the two different ordered crystal layers on the rubbing interface induced by high temperature, pressure and shear. The expanded graphite in sodium metasilicate solution studied here for the first time will extend its application for high temperature lubrication due to its excellent performance.

Ex-situ co-pyrolysis of sugarcane bagasse pith and polyethylene terephthalate (PET) was investigated over zeolite-based catalysts using a tandem micro-reactor at an optimised temperature of 700 °C. A combination of zeolite (HZSM-5) and sodium carbonate/gamma-alumina served as effective catalysts for 18% more oxygen removal than HZSM-5 alone. The combined catalysts led to improved yields of aromatic (8.7%) and olefinic (6.9%) compounds. Carbon yields of 20.3% total aromatics, 18.3% BTXE (benzene, toluene, xylenes and ethylbenzene), 17% olefins, and 7% phenols were achieved under optimal conditions of 700 °C, a pith (biomass) to PET ratio of 4 and an HZSM-5 to sodium carbonate/gamma-alumina ratio of 5. The catalytic presence of sodium prevented coke formation, which has been a major cause of deactivation of zeolite catalysts during co-pyrolysis of biomass and plastics. This finding indicates that the catalyst combination as well as biomass/plastic mixtures used in this work can lead to both high yields of valuable aromatic chemicals and potentially, extended catalyst life time.

Synthesis of nanomaterials from readily available minerals for industrial applications is a growing research area. Understanding the causes of their properties becomes handy in utilization. In this study, an effective sucrose solution based method was employed for the extraction of calcium from dolomite to synthesize precipitated calcium carbonate nanostructures with different morphologies and sizes. It was found that 30% (w/v) sucrose solution extracted approximately 91% of calcium from dolomite forming a calcium-sucrate complex. Carbonation was achieved by CO2 bubbling and aqueous sodium carbonate addition. Precipitation was performed under different pH values of 7.5, 10.5 and 12.5 in the absence of an anionic surfactant and in the template of sodium dodecyl sulfate (SDS)/calcium-sucrate at pH 12.5. It was found that CO2 bubbling slightly promotes smaller particles. The anionic surfactant enables particle size and agglomeration reduction while introducing some hydrophobicity. The smallest particles were achieved at a range of 40–55 nm in the presence of SDS/sucrose template and were of spherical morphology. By changing the pH, a tendency to form different polymorphs and shapes of calcium carbonate was observed.

The feasibility of employing ion-exchange resins for the selective removal of uranium from a complex waste effluent has been investigated. The source of the effluent is a treatment process to reduce the volume of a spent uranium containing catalyst prior to its immobilisation and disposal in South Korea. Commercial anion exchange and chelation resins have been screened, along with an in-house synthesized polyamine functionalized resin. The Langmuir isotherm model produced the best fit for UO22+ binding to all resins, with Purolite MTS957, a mixed sulfonic/phosphonic acid functionalised resin, showing the highest equilibrium adsorption capacity for UO22+, 96.15 mg g-1. The Modified Dose-Response Model was found to adequately represent breakthrough across all flow rates used and for all resins tested under dynamic testing conditions. The maximum uranium loading capacities under dynamic conditions for simulant and real wastes were established as 131.52 mg g-1 and 68.62 mg g-1,respectively. Purolite MTS957 effectively decontaminated the real effluent to uranium levels below the Korean release limit of 1 mg L-1. Over 99.9% uranium was successfully eluted from the resin bed in under 20 BV with a mixed sodium carbonate/sulfate eluent.

Succinic acid has been recognized as a useful platform chemical that can be applied in various industries. The application of bio-based succinic acid is still limited due to high downstream processing cost. In this study, vegetable oil-based emulsion liquid membrane (ELM) process is proposed to recover succinic acid from fermentation broth. The ELM system consists of three main liquid phases; external feed, membrane, and internal stripping. The liquid membrane phase was prepared by dissolving Amberlite LA2 and Span 80 in palm oil, while, the internal phase comprises of sodium carbonate solution, Na2CO3. The influence of feed, stripping agent and carrier concentration, treat ratio, as well as liquid membrane recycling on ELM performance were studied. The results showed 10 g/L of initial concentration, 1.0 M of Na2CO3, 0.7 M of Amberlite LA2, and treat ratio of 1:5 is the best condition with almost 100% recovery and enrichment of 21 times. The recycled liquid membrane concentrates the succinic acid up to 12 times. Therefore, the proposed ELM is a potential technology to extract bio-succinic acid.

Background: Salting-out extraction (SOE) had been developed as a special branch of aqueous two-phase system recently. So far as we know, few reports involved in extracting ginsenosides with SOE because of the lower recovery caused by the unique solubility and surface activity of ginsenosides. A new SOE method for rapid pretreatment of ginsenosides from the enzymatic hydrolysates of Panax quinquefolium was established in this article. Methods: The SOE system comprising ethanol and sodium carbonate was selected to extract ginsenosides from the enzymatic hydrolysates of Panax quinquefolium, and HPLC was applied to analyze the ginsenosides. Results: The optimized extraction conditions were as follows: the aqueous two-phase extraction system comprising ethanol, sodium carbonate, ethanol concentration of 41.51%, and the mass percent of sodium carbonate of 7.9% in the extraction system under the experimental condition. Extraction time had minor influence on extraction efficiency of ginsenosides. The results also showed that the extraction efficiencies of three ginsenosides were all more than 90.0% only in a single step. Conclusion: The proposed method had been successfully applied to determine ginsenosides in enzymatic hydrolysate and demonstrated as a powerful technique for separating and purifying ginsenosides in complex samples. Keywords: enzymatic hydrolysate, ethanol, ginsenosides, salting-out extraction, sodium carbonate

Water-uptakes of pure sodium carbonate (Na2CO3), pure β-alanine and internally mixed β-alanine/Na2CO3 aerosol particles with different mole ratios are first monitored using attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) technique. For pure Na2CO3 aerosol particles, combining the absorptions at 877 and 1422 cm−1 with abrupt water loss shows the efflorescence relative humidity (ERH) of 62.9%–51.9%. Upon humidifying, solid Na2CO3 firstly absorbs water to from Na2CO3·H2O crystal at 72.0% RH and then deliquesces at 84.5% RH (DRH). As for pure β-alanine particles, the crystallization takes place in the range of 42.4%–33.2% RH and becomes droplets at ~ 88.2% RH. When β-alanine is mixed with Na2CO3 at various mole ratios, it shows no efflorescence of Na2CO3 when β-alanine to Na2CO3 mole ratio (OIR) is 2:1. For 1:1 and 1:2 β-alanine/Na2CO3 aerosols, the ERHs of Na2CO3 are 51.8%–42.3% and 57.1%–42.3%, respectively. While β-alanine crystal appears from 62.7% RH for 2:1 and 59.4% RH for both 1:1 and 1:2 particles and lasts to driest state. On hydration, the DRH is 44.7%–75.2% for Na2CO3 with the OIR of 1:1 and 44.7%–69.0% for 1:2 mixture, and those of β-alanine are 74.8% for 2:1 mixture and 68.9% for two others. After the first dehumidification–humidification, all the water contents decrease despite of constituent fraction. And at ~ 92% RH, the remaining water contents are 92%, 89% and 82% at ~ 92% RH, corresponding to OIR of 2:1, 1:1 and 1:2 mixed system, respectively.

A novel lightweight adiabatic refractory material combining alkaline earth silicate (AES) fiber board and SiC particles was fabricated by immersing the AES fiber board into a slurry consisting of SiC particles with a median diameter of 1.2 μm and 13% silica-sol as an inorganic binder. When the composite was heated at 1400 °C for 8 h, the fired shrinkage of the composite was almost 0%, while that of untreated AES fiber board was 3.2%. The compressive strength of the composite heated at 1300 °C for 8 h was greatly improved to 0.95 MPa, 4.6 times that of untreated AES board. The corrosion resistance of the composite to a mixture of iron (II) oxide and sodium carbonate at 1400 °C was improved by more than 40% compared to that of untreated AES fiber board.

The extraction and separation of docosahexaenoic acid (DHA)-rich oils, proteins, and polysaccharides from microalgae is a challenge for industrial commercialization of DHA, such as drying and dewatering, cell wall disruption, laborious conventional extraction procedures and exploitation of large volumes of solvents. To address these concerns, a novel microwave-assisted three-liquid-phase salting-out extraction (MA-TLPSOE) was used to separate DHA-rich oils, proteins, and polysaccharides from wet cultivation broths of Schizochytrium limacinum SR21. The optimized MA-TLPSOE system was composed of 30% (w/w) n-hexane/13% (w/w) ethanol/9% (w/w) sodium carbonate and treated at high microwave power (650 W) for 30 s. Under optimized conditions, 100 ± 0.59% oil and 100 ± 0.64% DHA were partitioned in the top n-hexane phase while 93.75 ± 0.25% of polysaccharides and 92.96 ± 0.43% of proteins were distributed in the solid-phase interface. The effects of microwave power and duration, sodium carbonate, n-hexane, ethanol concentration and extraction time were studied. When the optimized system was enlarged from 20 g to 60 g, the yields of all effective components were almost the same. Thus, the MA-TLPSOE system is a promising and attractive technology, which could be used for the separation and extraction of various effective ingredients from complex natural products in a single step with significant recovery yield.

Copper(II) oxide powder manufacture from H2O2 type etching waste is proposed. The basic copper carbonate, the intermediate product, is depends on the reaction mole ratio of sodium carbonate to copper hydroxide. The optimum reaction mole ratio is 2.64 at 80 °C under copper content of 57.5 wt.%. The optimum usage of NaOH is 120 g for Copper(II) oxide. The Copper(II) oxide yield and chlorine ion concentration, are 97.0 wt.% and 9.0 mg L, respectively. The physical properties, such as mean particle size, dissolution time, and angle of repose are 20.0 μm, 60 s, and 34.1°, respectively. The via-hole filling thickness is 9.4 μm, which satisfies general electroplating criteria, 15 μm.

Removal of oxygen atoms from triglycerides is the most important step in their conversion into hydrocarbons. Basic catalysts have proven to be highly efficient in deoxygenation, whereby the oxygen atoms are removed in the form of CO and CO2, yielding pyrolytic oil with acid number below 10 mg KOH⋅g−1. We have now investigated the deoxygenation abilities of composite basic catalysts during the thermochemical conversion process. The dynamics of the catalytic cracking reaction using metal oxides, such as calcium oxide, in the presence of sodium carbonate, has been tested. According to thermogravimetric analysis (TGA) data, the activation energy for catalytic cracking was influenced by cations. By using calcium oxide as a catalyst, the activation energy was reduced from 260 kJ/mol to 185 kJ/mol, leading to a reduction in the reaction temperature of approximately 20–40 °C. The yield of the cracked liquid fraction was of the order of 66–70%, more than 90% of which could be recovered as liquid hydrocarbons. The results presented herein indicate an alternative reaction pathway, allowing thermochemical conversion to be conducted at a lower operational temperature, which would be beneficial for industrial production with lower energy consumption.

Mononuclear Eu(III) and Dy(III) complexes of the chiral hexaaza macrocycle L, 2(R),7(R),18(R),23(R)-1,8,15,17,24,31-hexaazatricyclo[25.3.1.1.0.0]-dotriaconta-10,12,14,26,28,30-hexaene have been obtained as chloride derivatives (1 and 2, respectively) and characterized by using spectroscopic methods. The X-ray crystal structure of 2 has been determined. The reaction of two equivalents of mononuclear 1 or 2 complexes with one equivalent of sodium carbonate results in the formation of dinuclear complexes [Eu2L2(µ2-CO3)(H2O)3]Cl4 3 and [Dy2L2(µ2-CO3)(H2O)3]Cl4 4, respectively. The X-ray crystal structure of complex 3 reveals two macrocyclic [EuL]3+ units bridged by the carbonate anion. The carbonate anion is bound to the Eu(III) ions using the η1:η2-µ2 bridging mode. The binding of carbonate anions to the [EuL]3+ or [DyL]3+ macrocyclic units has also been studied in solution using spectroscopic methods. The titration of the starting paramagnetic mononuclear chloride derivatives 1 and 2 monitored by 1H NMR spectroscopy revealed initial formation of dinuclear species, followed by the formation of complexes possessing additional carbonate ligands. The dinuclear carbonate complexes 3 and 4 are also formed in the reactions of the respective mononuclear chloride complexes with gaseous CO2. Lanthanide(III) complexes of the chiral hexaaza macrocycle L are effective for catalytic hydrolysis of bis(4-nitrophenyl) phosphate BNPP. Within the series of the studied mononuclear complexes: nitrate derivatives [LnL(NO3)(H2O)](NO3)2 (Ln = Ho, Er), [LnL(H2O)2](NO3)3 (Ln = Tm, Yb, Lu) and chloride derivatives [LnL(H2O)2]Cl3 (Ln = Tm, Yb, Lu, Y) the catalytic activity of the complexes is increased with increasing ionic size. Kinetic studies revealed that most active is the dinuclear europium(III) complex 3 which catalyzes the hydrolysis of BNPP with a rate kobs = 6.5 × 10−5 s−1 (at 0.3 mM concentration of the catalyst) at pH 8.5 and 37 °C.

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.

Alkali-based chemical enhanced oil recovery is used to increase the incremental oil production and relies on the interaction of alkali lye with crude oil. Optimizing the chemical formulation depends on screening multiple alkali concentration ranges to maximize the generated emulsion volume. However, the strong chemical variation of the crude oil, caused by biodegradation within the reservoirs, and its influence on generating in-situ soaps has never been studied in detail. In this paper, organic geochemical oil characterization was combined with phase screening data. Thereby, differences in terms of initial crude oil composition (slightly degraded, moderate degraded, and heavy degraded oils), but also regarding the excess alkali-equilibrated oil phase, and the hydrocarbons which are included in the in-situ soap (emulsion phase) were worked out. Different alkalis, concentration ranges, and water-oil-ratios were studied, to understand the control mechanism for the in-situ soap generation. The formed emulsions were observed over time (emulsion stability) and classified into possible emulsion types. Alterations caused by the alkali-oil interaction were quantified by the use of organic geochemistry. The degree of biodegradation seems to be an important control mechanism. Slightly degraded oils do not interact with the alkali lye due to a high content of non-polar compounds such as alkanes and isoprenoids. Moderately and heavily degraded oils show varying interactions with the alkali solution. The degree of interaction depends on the used degradation type, the alkali type as well as on the used concentration. Moderately degraded oils interact in a lower concentration range compared to heavily degraded oils, which show an increased non-soap forming acid content. Phase experiments conducted over a long period of time (100 days) were used to determine which emulsion types (micro or macro) were formed. Stable micro emulsions were preferably generated over time in formulations prepared with potassium carbonate (K2CO3). In contrast, formulations containing sodium carbonate (Na2CO3) hardly did not generate stable micro emulsions. The composition of alkali-equilibrated oil differs from the initial oil composition and shows a strong dependency of the used alkali type. Potassium carbonate caused mild alterations of the moderately and heavily degraded oils, whereas the impact of sodium carbonate was more severe. In addition, dissolution of naphthalenes, steranes, hopanes, and parts of the generated in-situ soap into the aqueous phase, was observed during the performed phase experiments of the moderately degraded oils (at the elevated pH values).

Recently, the design of photocatalytic building materials for self-cleaning, self-disinfecting, and environmental pollution remediation has resulted in increasing interest. The advantage of using solar energy and rainwater as driving force has opened a new domain for environmentally friendly building materials. This work reports the fabrication of photocatalytic self-cleaning coatings with alternative building materials such as fly ash, sodium carbonate as an alkaline activator, and bismuth-based photocatalysts deposited on concrete. The photocatalytic materials were powders of Bi 2 O 3 , Bi 2 O 2 CO 3 , BiOI, BiVO 4 , BiPO 4 , which were synthetized by a precipitation method at room temperature without the use of surfactants or additives. The photocatalytic self-cleaning efficiency of the coatings was evaluated according to the ISO 10678:2010 norm by using aqueous methylene blue (MB) as a model pollutant in order to measure the photoactive surface’s ability to degrade dissolved organic molecules under light irradiation. The tendency of the photocatalytic self-cleaning coating activities was: Bi 2 O 2 CO 3 (49%) > BiOI (30%) > BiVO 4 (15%) > BiPO 4 (14%) > Bi 2 O 3 (5%) after 3 h of reaction. The best result was obtained when Bi 2 O 2 CO 3 was incorporated into the coatings, and it was associated to its lowest crystallite (27 nm), flake-like morphology, and to its negatively charged surface (pH PZC = 11.5) at the pH of the experiments, that favored the adsorption of the cationic dye (MB) on its surface. The self-cleaning efficiency of the Bi 2 O 2 CO 3 coating was investigated at different curing ages: 7, 14, and 28 days. It was observed a decrement in the photocatalytic activity with increasing the curing age. However, it was possible to restored the self-cleaning efficiency after washing the surface with water due to the removal of hydration products, which filled up the coating-pores forming diffusion barriers to both reactants and photons.

This work presents the effect of calcium and carbonate precursors on properties of CaCO3. The synthetic CaCO3 samples were transformed into CaO and tested their application to high-temperature CO2 capture. Four different sorbent precursors were investigated in this work, including calcium chloride (CaCl2) and calcium acetate (CaAc2) as calcium precursor, and sodium carbonate (Na2CO3) and urea (CO(NH2)2) as carbonate precursor. The results show that both calcium and carbonate precursors affect morphologies of CaCO3; CaCO3,Cl-Urea, and CaCO3,Cl-Na have calcite phase, whereas mixed-phases of calcite (30%) and vaterite (70%) are observed with CaCO3,Ac-Na, and aragonite is found with CaCO3,Ac-Urea. CaCO3,Cl-Na exhibits small cubic (rhombohedral) particle, CaCO3,Cl-Urea possesses spherical particle with rough surface, CaCO3,Ac-Na has spherical-like morphology with smooth surface, and CaCO3,Ac-Urea possesses aggregated form of CaCO3 particles. For application to CO2 capture, CaO derived from CaCO3,Ac-Urea provides the highest CaO conversion of 80% at 700 °C. The synthetic CaO-based sorbents were further incorporated with nickel oxide to form one-body bi-functional catalysts for H2 production from sorption-enhanced steam ethanol reforming. The results show that 87%H2 purity could be obtained with pre-breakthrough period of 60 min. Sorbent reactivity can be maintained the production of H2 for at least 10 consecutive cycle tests.

A weathered bentonite (Japanese acid clay), a natural resource found as a by-product in the production of bentonite, was altered by an environmentally friendly treatment, where the Japanese acid clay was mechanochemically mixed with sodium carbonate without the addition of solvent, to give sodium type bentonite. The product was subsequently purified by conventional dispersion-sedimentation method to obtain purified sodium bentonite. The altered acid clay and the purified product exhibited useful swelling properties, which are satisfactory for industrial uses of conventional high quality sodium bentonites, and further functionalization of the product was possible through ion exchange. As an example, an organophilic clay, which is useful as adsorbent for toxic organic compounds from environments, was successfully prepared by the ion exchange of the present product with a cationic surfactant. The present mechanochemical process is an important environmentally benign option for the modification of the natural resources for the practical uses.

The purpose of this study was to develop alkali activated earthen materials with enhanced physical and mechanical properties. Specifically, clay mortars were produced, by using various alkaline activators of different pH (values 11–14). The specimens were cured in certain conditions. The physical and mechanical properties of the mortars manufactured were measured at the age of 28 days. Specifically, capillary absorption, shrinkage, Karsten tube penetration, porosity, as well as compressive and flexural strength tests were performed. Additionally, microscopic analysis was also conducted. The results of the experiments indicated the positive effect of potassium metasilicate and the combination of sodium metasilicate with sodium hydroxide solution on mechanical characteristics. The influence of sodium carbonate as an alkali activator was also proven beneficial on the physical properties of the specimens. In conclusion, the alkaline activators with pH > 12, lacked in enhancing physical properties, yet allowed the development of mechanical strength, while the alkaline activators with lower pH values showed reversed results.

A diluted alkali-soluble pectin (DASP) fraction, extracted using sodium carbonate, is characterized by a low degree of methylesterification and has the ability to self-organize on mica. The aim of this study was to characterize the cross-linking process of this fraction, extracted from apples, over a wide pH range (3-11) and without the addition of salt. An FT-IR study showed an increase in the intensity of bands connected with νas and νs (COO−) and a decrease in the intensity of the band associated with ν (C=O) in the carboxyl group with increasing pH, which indicated the dissociation of the carboxyl groups of galacturonic acid units. An increase in the surface electrical charge of particles in the pH range of 3–7 confirmed this. The value of the average apparent dissociation constant (∼4.60) indicated the acidic character of the DASP fraction. An AFM study showed the morphological changes of the DASP fraction with increasing pH, which allowed for the evaluation of the cross-linking process. This fraction formed a network on mica at pH 4 and 9, while the aggregates were noted mainly at pH 11. For totally ionized carboxyl groups (pH 7), the pectin chains were separated from each other due to the electrostatic repulsion between them.

This study represents the fresh state behavior of Na2CO3-activated ground granulated blast furnace slag (GGBS) pastes. Sodium carbonate (NC) is a suitable activator, though with an extended setting time. To accelerate the hydration process, NC was replaced with sodium hydroxide (NH), then, slaked lime (CH) was used as a carbonate binding agent. This replacement improved the rheological properties, but increased the setting time. The use of 3% CH with GGBS caused a significant decrease in setting time, enabled to set within 6.5 h. The decrement was attributed to the removal of a large amount of dissolved carbonate ions from the fresh state pastes. The NH replacement did not effectively enhance the fresh properties. In the pore solution, the CO32− ion concentration is one of the major parameter that affects the reaction besides other ions released from raw material.

The enhancement of surface functional groups of biochar is essential to improving the biochar contaminant adsorption. Current pyrolysis methods that are accompanied by activation are energy consuming and costly. Herein, a novel wet-pyrolysis system that was carried out in open air, with simultaneous conversion and modification to produce an effective biochar adsorbent, is described. Within this system, the surface of the biochar was oxidized partially to produce sufficient functional groups at the surface, whereas carbonization of the biomass (miscanthus sacchariflora) occurs under an acidic catalyst. The characteristic results confirmed the attachment of abundant surface functional groups, including hydroxyl and carboxyl groups, which increased in content with the ongoing reaction time. Neutralization with sodium carbonate removed the hydrogen bonds and enhanced the adsorption properties. The biochar that was obtained by using this technique exhibited an excellent cadmium adsorption capacity of 197 mg .g−1 and a high removal efficiency of 99%. Analysis of the Cd-loaded biochar indicated that adsorption occurred via ion exchange, and formed cadmium complexes. It could be concluded that this novel wet-pyrolysis system is a promising approach to produce biochar efficiently and cost-effectively for heavy-metal remediation.

Surface modification of biochar is significant to obtain more functionalized material for contaminants immobilization. In situ modification, modifying the biochar while the conversion process, was applied by a novel wet pyrolysis system. By using phosphoric acid as working medium, liquid/air interface was created to introduce low content of oxygen, under the control of appropriately settled reaction temperature. Followed with the addition of sodium carbonate to neutralize the system and increase mineral species, effective biochar adsorbent attached with large quantity of acidic oxygenic and phosphoric groups, and carbonate anions was finally produced. The biochar showed excellent decontamination performance of lead with a high adsorption capacity of 316 mg·g−1 and removal efficiency larger than 95%. The alteration of the characteristics after the adsorption confirmed the adsorption mechanism is the bi-function of surface coordination and precipitation. This novel route is easy handling and energy saving, promising it to be a reliable way to produce biochars with attractive surface properties for environmental decontamination.

Flotation tests were performed on a skarn ore to attain the selective separation of scheelite (CaWO4) from fluorite, apatite, and silicates. Fluorite and apatite constitute common gangue minerals in scheelite ores. Due to their similar surface properties and good floatability, the separation of scheelite from fluorite is particularly difficult. These ores are usually processed at basic pH using sodium silicate as a gangue mineral depressant and a fatty acid as the collector. Sodium silicate was not efficient enough to depress the fluorite in the studied ore. Thus, different depressants were tested in the flotation of scheelite using a commercial mixture of fatty acids. The effect of adding metallic salts [FeSO4, Al(NO3)3, and Zn(SO4)] prior to sodium silicate was therefore investigated. The sole use of organic molecules (starch, lignin sulfonate, tannin, carboxymethyl cellulose, and citric acid), instead of sodium silicate, was also studied. This led to a global depression of the minerals, including scheelite, and did not improve the selectivity of the separation. The addition of metallic cations did not significantly enhance the selectivity of the flotation; however, iron sulphate slightly increased the sodium silicate performance. Overall, among all the studied depressants, the combination of sodium carbonate and sodium silicate presented the best efficiency. This system was then studied through the design of experiments methodology. Strong synergistic effects existed between the two reagents, mainly impacting the scheelite and fluorite recovery as well as the scheelite grade. This was attributed to surface carbonation of the minerals, subsequently leading to a better depression by sodium silicate. The effect of sodium carbonate on the apatite and silicates was small. This was attributed to spontaneous carbonation and the presence of complex crystallographic structures, respectively. The efficiency of the sodium carbonate/sodium silicate combination was limited (maximum WO3 enrichment ratio = 16.48) due to the lack of selectivity of the depressants. The proposed optimization of the flotation separation of scheelite from gangue minerals maximizes both the WO3 grade and recovery.

Ceramic foams with low bulk density and uniform tiny pores were successfully prepared from coal bottom ash (CBA) by introducing only a small amount of sodium carbonate and magnesium oxide as fluxing agents. The effects were investigated of the Na2O and MgO contents on the bulk density, the crystalline phases, the pore structure and the compressive strength of the ceramic foams. The results indicated that, at firing temperature, an increase in Na2O content significantly improved the pore formation ability of CBA powder compacts. The samples that contained 8 wt% Na2O exhibited a low bulk density and large-sized pores but the Na2O caused a dramatic change in bulk density with firing temperature. Nevertheless, if MgO was introduced, the increasing MgO content resulted in a further decrease in bulk density as well as a decrease and homogenization of the pore size. The improved pore structure of samples that contained more than 4 wt% of MgO contributed to a relative increase in their compressive strength. It was concluded that MgO can be used as a foam stabilizer for ceramic foams produced from CBA powder. 4–6 wt% of MgO combined with 6 wt% of Na2O in the composition of CBA powder was determined to be the best proportions for preparing ceramic foams with an optimal pore structure and good mechanical properties.

In the present study, an environment-friendly one-part alkali-activated cement dry mixture was prepared by using blast furnace slag as the aluminosilicate precursor, solid sodium carbonate as the alkali activator and calcined dolomite (CD) as the reaction kinetics controlling additive. The effects of CD addition on the reaction kinetics and phase evolution of the hydrated cement paste were investigated by using the isothermal conduction calorimetry (ICC), X-ray diffractometry (XRD), thermogravimetric analysis (TGA) and nitrogen adsorption technique. The CD addition promoted the formation of hydrotalcite-like phase in the paste to consume the excess CO32− ions. This is helpful in raising the alkalinity of the pore solution, and consequently enhancing the rate and degree of the alkali-activation. The growth of space-filling C-A-S-H gel phase leads to a more compact pore structure in the paste with higher CD content. The CD addition enables the Na2CO3-activated slag paste to set within 24 h, and improves the compressive strength to an acceptable value of 32.9–41.6 MPa after 28 days of curing at ambient temperature.

Herein a strategy for biogas upgrading in a continuous flow absorption unit using CaCl2 as capturing agent is reported. This process is presented as an alternative to the standard physical regeneration processes to capture carbon dioxide (CO2) from biogas effluents with inherent high energy penalties. This work showcases a systematic study of the main parameters (reaction time, reaction temperature, and molar ratio reactant/precipitator) affecting calcium carbonate (CaCO3) precipitation efficiency in a reaction between sodium carbonate (Na2CO3) and CaCl2. In addition, the purity and main characteristics of the obtained product were carefully analysed via in a combined characterization study using Raman, XRD, and SEM. Our results indicate that acceptable precipitation efficiencies between 62 and 93% can be reached by fine tuning the studied parameters. The characterization techniques evidence pure CaCO3 in a calcite structure. These results confirmed the technical feasibility of this alternative biogas upgrading process through CaCO3 production.

This study compares thermal decomposition of pure and transition metal-doped (Fe, Co, Ni, Cu, and Zn) calcium carbonate samples under 0.1 mbar of Ar, H 2 O, and H 2 in order to evaluate the effects of doping on CO 2 release and conversion. All samples were synthesized via precipitation methods at room temperature from calcium chloride and sodium carbonate precursors, with additional doping of the relevant transition metal chloride. Structural and compositional analysis of the as-prepared and calcined materials is presented. TM-doping results in an earlier onset of CO 2 release as compared to Pure CaCO 3 irrespective of calcination gas. Cu-doping induced the largest temperature reduction. Calcination in H 2 O produces an additional lowering of the release temperature, as compared with calcination in Ar, with the Zn-doped sample exhibiting the largest enhancement. During calcination in H 2 , the Ni-, Co- and Fe-doped samples produce a significant enhancement of CO 2 to CO conversion, whereas the overall conversion by the Cu- and Zn-doped samples remained comparable to that of Pure CaCO 3 . The Ni-doped samples, which produced the highest CO 2 conversion, showed the largest comparative enhancement when the calcination gas was changed to H 2 .

The increasing of aluminum demand globally raises the interest in developing alternative technologies to produce alumina from non-bauxitic sources, especially clays. This paper studies the extraction of alumina from the kaolin ore excavated from the Irkutsk region, Russia through the leaching process, using aqueous solutions of sodium carbonate as a leaching agent. Before the leaching process, the kaolin ore and limestone charge was sintered. The sintering process achieves the dehydroxylation of the kaolinite, which is the main mineralogical phase in the kaolin and activates its transformation to metakaolin. Metakaolin is an amorphous Al Si phase, from which alumina could be easily leached. The annealed sintered material transform into dust that is suitable for the leaching process without any additional grinding. The sintering process was taken place in the temperature range 800-1400 °C for 1 h. The effect of briquetting pressure and sintering temperature on the recovery of alumina from kaolin, were studied. About 87% of the alumina in the kaolin was extracted at 1360 °C and briquetting pressure of 5 MPa.