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This study focuses on the synthesis of a monocarboaluminate (MCA)-based binder by treating marble waste (MW) powder with sodium aluminate (SA). The aim is to investigate the influence of various parameters, including the alumina modulus (MA) of SA, different contents of calcined clays with varying alumina levels, and curing temperatures, on the performance and phase composition of the resulting binder. The results demonstrate that the combination of SA and MW leads to the formation of an MCA-based binder, which exhibits a high compressive strength of up to 28 MPa after seven days of curing. Additional phases such as gibbsite, pirssonite, and gaylussite are observed, indicating the occurrence of a cationic exchange reaction between MW and SA, as confirmed by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). The stability of the resulting binder is primarily influenced by the MA value, with higher values associated with greater stability. Regardless of the type of calcined clay used, incorporating calcined clay results in the formation of a calcium aluminate silicate hydrate (CSAH) phase alongside MCA, contributing to the improved stability of the hardened binder over time. Notably, calcined clay with a higher alumina content exhibits the highest strength at all curing ages. Furthermore, increasing the curing temperature up to 100 °C significantly enhances the early strength, which correlates with the formation of the kotoite phase at the expense of the MCA phase. [ABSTRACT FROM AUTHOR]

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This paper presents the application of sodium aluminate, directly or after small adjustments in concentration and purity, in some other valuable intermediary products. Sodium aluminate is an intermediary product in Bayer technology applied by Alum SA Tulcea production of alumina and alumina products. Mainly, sodium aluminate is a carrier of aluminum hydroxide between important manufacturing stages in the Bayer process, bauxite processing, and aluminum hydroxide crystallization. After a short investigation of the uses of sodium aluminate, it was decided to choose and study the possibility of converting this secondary product into ecological material for the treatment of natural or industrial wastewater. Actually, on the market, products similar to sodium aluminate from Alum SA Tulcea provide treated waters with high purity and reasonable quality, excellent coagulation rates, rapid flotation, and sedimentation, and in addition, significant side effects, such as excellent removal of phosphorus and silica from treated water. Treatments do not require lime or hydroxide to control alkalinity, and chemical sludge remains at a minimum volume and mass. The test performed with sodium aluminate from Alum SA Tulcea was comparable with other tests with Al2(SO4)3 and FeCl3. The maximum removal yields of global organic load expressed by chemical oxygen demand (COD) and biochemical oxygen demand (BOD5), chromium (Cr VI), and total suspended solids (TSS) were: 83%COD, 71% BOD5, 99.7% Cr VI and 93% TSS.

Magnetite (Fe3O4) particles deposited with zeolite, which was made from sodium hydroxide (NaOH), sodium aluminate (NaAlO2) and sodium trisilicate (Na2O7Si3) using the hydrothermal process, were used in the adsorption of methylene blue (MB). A continuous stirred tank reactor (CSTR) system was used for the adsorption of MB using zeolite/Fe3O4. This study encircled the continuous reactor with a magnet to prevent the adsorbent from flowing to the output, thus producing clean water devoid of Fe3O4 particles. The performance of the adsorbent was assessed based on the effects of adsorbent mass, flow rate, pH and concentration. The adsorbent was able to remove approximately 90% of the 20 mg L−1 methylene blue from a 500 mL solution in 2 h, with a maximum adsorption capacity of 30.8528 mg g−1. This adsorption process also exhibited high removal efficiency even after 5 regeneration cycles and 55 h of operation, confirming the successful production of zeolite/Fe3O4 as an effective MB adsorbent. [ABSTRACT FROM AUTHOR]

A novel and efficient procedure has been developed to synthesize furan‐2‐carboxylate derivatives through a one‐pot condensation of chloroacetate derivatives, 1,3‐diketones, and chloroform in the presence of magnetic sodium aluminate 40 wt. % (Aluminate NP‐40). The synthesized heterogeneous catalyst can be easily recovered from the reaction mixture by applying an external magnetic field. Magnetic aluminate NP catalysts provide a sustainable, environmentally friendly, and cost‐effective method for synthesizing furan‐2‐carboxylate derivatives. Additionally, the catalyst is stable and can be reused multiple times without losing its catalytic properties. High product yields in a short experimental time and easy workup are other advantages of the present method. All synthesized compounds were characterized by NMR spectroscopy. [ABSTRACT FROM AUTHOR]

The present study explores a cost-effective method for using activated ground granulated blast furnace slag (GGBFS) and silica fume (SF) as cement substitutes. Instead of activating them with expensive alkali solutions, the present study employs industrial-grade powdered sodium aluminate (SA) and hydrated lime (HL) as activators, reducing expenses by about 94.5% compared to their corresponding analytical-grade counterparts. Herein, the exclusivity is depicted using less pure chemicals rather than relying on reagents with 99% purity. Two mixing techniques are compared: one involves directly introducing powdered SA and HL, while the other premixes SA with water before adding it to a dry powder mixture of GGBFS, SF, and HL. Microstructural analysis reveals that the initial strength results from various hydrate phases, including calcium–sodium–aluminate–silicate hydrate. The latter strength is attributed to the coexistence of calcium–silicate hydrate, calcium–aluminate–silicate hydrate, and sodium–aluminate–silicate hydrate, with contributions from calcite and hydrotalcite. The SF content significantly influenced the formation of these gel phases. Thermogravimetric analysis (TGA) reveals phase transitions and bound water related to hydration products. The optimal mix comprises 10% SF, 90% GGBFS, 9.26% HL, and 13.25% SA, with a water-to-solid ratio of 0.45. This approach yields a compressive strength of 35.1 MPa after 28 days and 41.33 MPa after 120 days, hence being suitable for structural construction. [ABSTRACT FROM AUTHOR]

The anthropogenic carbon dioxide (CO2) fixation and various engineering strategies are gaining very significant attention because of the expansion of the net‐zero carbon environment in the atmosphere. Herein, we designed a sodium aluminate@γ‐alumina (NaAlO2@γ‐Al2O3) catalyst by a simple and facile precipitation and impregnation tactics. A series of different weight percentage NaAlO2@γ‐Al2O3 materials were successfully synthesized and well characterized by using advanced analytical and spectroscopic techniques such as TGA, XRD, FE‐SEM, TEM/HR‐TEM, FT‐IR, Raman, TPD, and XPS analysis. The NaAlO2@γ‐Al2O3 catalyst was employed as a competent catalyst for the CO2 fixation under atmospheric pressure reaction conditions. The catalytic activity results evidently revealed that the cycloaddition reaction successfully achieved 94% styrene oxide conversion and 93% selectivity, along with an 87% yield of the styrene carbonate at 120 °C for 6 h. Furthermore, we comprehensively examined the effect of different reaction parameters such as the effect of sodium aluminate amount, co‐catalyst amount, temperature, and time for CO2 fixation reaction. Additionally, different terminal and internal epoxides were tested under optimized reaction conditions and achieved moderate to excellent yield of the desired cyclic carbonate products. Interestingly, a plausible reaction mechanism was proposed for the styrene carbonate synthesis using NaAlO2@γ‐Al2O3 catalyst surface with the support of characterization and experimental results. Remarkably, the NaAlO2@γ‐Al2O3 catalyst could be easily recoverable and successfully recyclable up to six consecutive cycles without declining its initial catalytic activity along with stable structural and physicochemical properties. [ABSTRACT FROM AUTHOR]

Organic montmorillonite (OMMT) was prepared from Na-montmorillonite (MMT) by Hexadecylamine (HDA) modification. The composite material has good smoothness, acidity, and salt resistance. OMMT was characterized using small-angle X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and a video optical contact angle measuring instrument. The results showed that the layer spacing was enlarged from 1.44 nm to 2.87 nm after the modification, and the hydrophobicity performance was greatly improved. The organic modification of MMT was successful. The surface morphology, roughness, and anticorrosion properties of the organic montmorillonite/epoxy (OMMT/EP) composite coating were investigated and compared with those of the epoxy (EP) coating. The OMMT/EP composite coating had a flatter surface than the EP coating. The roughness was reduced from 65.5 nm to 10.3 nm. The electrochemical impedance spectroscopy showed that the composite coating's thickness positively affected its anticorrosion performance, the corrosion current density (Icorr) decreased with the increase in thickness, and its maximum impedance was much larger than that of EP coating. The protection efficiency of the OMMT/EP composite coating was 77.90%, which is a significant improvement over the EP's 31.27%. In addition, the corrosion resistance of the composite coating gradually decreased with increasing immersion time, but the change was insignificant. [ABSTRACT FROM AUTHOR]

In alumina production, the evaporation as the key process uses recyclable resources and reduces environmental pollution. In fact, the quality of export product with offline and delayed, results in low precision of process control and high energy consumption. To ensure green and efficient production, in this paper, a new prediction method integrating process knowledge and data-driven spatial-temporal adaptive model is put forward. First, to preprocessed production data for ensuring modeling accuracy, data reconciliation technology is adopted. Then, based on material and heat transfer mechanism, for equipment and industrial process, the mechanism models are established. Furthermore, with time difference and moving window model, an error compensation method is utilized in terms of double locally weighted kernel PLS for estimation error in hypothesis-based mechanism modeling. Finally, the data-driven spatial-temporal adaptive model and the process knowledge-based mechanism model are integrated. To illustrate the model feasibility, an industrial sodium aluminate solution evaporation is used. It demonstrates that, for the developed model, the prediction accuracy can reach more than 90% within the ± 2% error range, and effectively estimate the actual product quality and ensure the prediction effect. • A new concentration prediction method integrating knowledge and data-driven spatial-temporal adaptive model is proposed. • Mechanism modelling based on data reconciliation and process analysis is achieved to estimate concentration. • A TD-MW-DLWKPLS model considering both sample similarity and variable correlation is adopted for error compensation. • The performances of the developed method are validated on evaporation industrial application. [ABSTRACT FROM AUTHOR]

To improve the corrosion resistance of TiNi alloy fabricated by laser powder bed fusion (LPBF), a porous oxidation layer was synthesized by micro-arc oxidation in a sodium aluminate and sodium silicate electrolyte. The influences of the applied voltage and the processing time on the morphology of oxidation layer were investigated, and the corrosion behavior of the oxidation layer in artificial saliva was evaluated and compared with that of the as-fabricated LPBF alloy. The results indicate that, as increasing the applied voltage and the processing time, the oxidation layer becomes uniform and integrated. The optimum parameters are with an applied voltage of 450 V and processing time of 40 min. The oxidation layer primarily contains α-Al2O3 and consists of two layers, i.e., a thin, compact and uniform inner layer and a porous outer layer. The formation of stable α-Al2O3 phase in the coating and its almost non-porous dense structure reduce the channels for corrosion ions to penetrate into the substrate through coating, thereby improving the corrosion resistance of TiNi alloy. [ABSTRACT FROM AUTHOR]

The ultra-high lime aluminum method (UHLA) is a method that can effectively adsorb chloride ions in a solution. Calcium oxide (CaO) and sodium aluminate (NaAlO2) were mixed and added to the sodium chloride solution. After the reaction lasted for some time, the content of chloride ions in the solution was significantly reduced. Through the experiment of chloride ion adsorption, it was found that when the mass ratio of calcium oxide to sodium aluminate was m(NaAlO2):m(CaO) = 1:2.5, the reaction temperature was 25°C, and the stirring time was 60 min, the adsorption effect on chloride ion was the best. The adsorption rate can reach 93.3% in a 100 mg/L sodium chloride solution. With the increased sodium chloride concentration, the time required to reach adsorption equilibrium becomes longer. In a 2,000 mg/L sodium chloride solution, this method's unit adsorption mass of chloride ion can reach 63.5 mg/g. Through SEM and XRD analysis, calcium oxide and sodium aluminate react in solution to form Ca4Al2(OH)14 with a layered structure. The OH- between the layers can exchange with external chloride ions. After Ca4Al2(OH)14 adsorbs chloride ions, the product is Friedel's salt (Ca4Al2Cl2(OH)12) with the same layered structure. [ABSTRACT FROM AUTHOR]

The influence of process parameters in the three-stage purification of aluminate solution from the Bayer process and aluminum hydroxide was considered in this paper. One of the ways of purification is treating the aluminate solution in order to reduce the concentrations in the starting raw material (solution) and then treating the aluminum hydroxide at a certain temperature and time in order to obtain an alumina precursor of adequate quality. The purification process itself is divided into three phases. The first phase involves the treatment of sodium aluminate with lime in order to primarily remove Ca2+ and (SiO3)2− impurities. Phase II aims to remove impurities of Zn2+, Fe2+, and Cu2+ by treatment with controlled precipitation using specially prepared crystallization centers. In Phase III, Na+ is removed by the process of hydrothermal washing of Al2O3 ∙ 3H2O. In this work, parameters such as temperature (T), reaction time (t), and concentration of lime (c) were studied in order to remove the mentioned impurities and obtain the purest possible product that would be an adequate precursor for special types of alumina. [ABSTRACT FROM AUTHOR]

Copyright of Inorganic Chemicals Industry is the property of Editorial Office of Inorganic Chemicals Industry and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Mordenite's excellent physical and chemical qualities set it apart from other zeolites with similar applications in industry. Mordenite is frequently produced through hydrothermal processing with TEA+ cations. The best template agent is TEA+ cations, despite the fact that they may lead to a variety of problems, such as the release of toxicity, the high cost of production, the contamination of wastewater, and environmental damage. So, it's important to develop a mordenite synthesis technique that doesn't need an organic template or a cheap template. The mordenite-type zeolites were prepared using sand from the western part of Iraq (Ar-Rutbah). Silica was extracted from Iraqi sand as a silica source and sodium aluminate as a source of alumina Al by using the SOL-GEL method through the hydrothermal technique at temperatures ranging from 23 to 27 °C over a period of 7 days. Analyses such as XRD, BET surface area AFM, FT-IR, and FE-SEM were performed on the sample. The average particle size was 31.9 nm, and the BET surface area was 202.487. XRF detected the ratio of silica to alumina (Si/Al = 4.55), and the exchange of sodium ions for hydrogen ions through ionic exchange is 100%. The micrograph clearly reveals a tiny portion of the crystal band with a flaky habit, while FE-SEM images of synthesized H-MOR show that plates form the majority of the crystals. [ABSTRACT FROM AUTHOR]

Over a billion tons of high-sulfur bauxite has not been utilized effectively currently in China, because the pyrite existing in the bauxite poses a range of hazards during the Bayer process. A novel idea was proposed to remove sulfur by the silicon-containing minerals in bauxite reacting with sulfur species in sodium aluminate solution to form sulfur-bearing desilication products (SDSP) for discharge with the red mud in the Bayer process. This study investigated the reaction behavior between kaolinite and different sulfur-containing ions under the simulated Bayer process conditions, elucidating the desulfurization rate variation and formation mechanism of SDSPs. The thermodynamic calculations suggest that the reaction between kaolinite and sulfur-bearing sodium aluminate solution to form SDSPs can occur spontaneously. The experimental results demonstrated that various SDSPs can be produced through the reaction of kaolinite and sulfur-containing ions in sodium aluminate solution during the simulated Bayer process, resulting in various desulfurization efficiencies, while the desulfurization process will not result in additional alkali consumption. Increasing the kaolinite dosage, extending the reaction time, and elevating the reaction temperature all contribute positively to enhancing desulfurization efficiency. Kaolinite reacted with  S 2 O 3 2 −  in sodium aluminate solution to generate Na8Al6Si6O24S2O3·2H2O, achieving a desulfurization rate exceeding 90% under optimized conditions. Under the simulated Bayer digestion process conditions at elevated temperature, the desulfurization rates of kaolinite ranked in ascending order as  S 2 −  <  SO 3 2 −    <  SO 4 2 −  <  S 2 O 3 2 − . Kaolinite reacted with  SO 4 2 −  and  S 2 O 3 2 −  to form cancrinite type SDSPs, and a superior desulfurization rate can be achieved. This work can provide a theoretical foundation and technological support for the efficient utilization of high-sulfur bauxite by the Bayer process. [ABSTRACT FROM AUTHOR]

Copyright of China Harbour Engineering is the property of Editorial Office of China Harbour Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The problem that sulfur causes in alumina production using the Bayer process can be eliminated by adding sodium nitrate, and, while the reaction mechanism is not perfect, this paper studies the reaction mechanism of sodium nitrate and different valence sulfurs in a sodium aluminate solution by combining thermodynamic calculations and experiments. Through thermodynamic analysis, it is deduced that sodium nitrate undergoes oxidation reactions with low valence sulfur (S2−, S2O32−, and SO32−) of different valence states in a sodium aluminate solution, while the oxidation effect of S2− is the most obvious. By studying the influence of the sodium nitrate dosage, oxidation time, and oxidation temperature on the different valence sulfurs in a sodium aluminate solution, it is concluded that S2− removal reaches 67.74% under the conditions of 3% sodium nitrate dosage, 260°Coxidation temperature, and 60-min oxidation time. However, the oxidation effect on S2O32− and SO32− is not obvious. The experimental results are consistent with the thermodynamic calculation results. Finally, the reaction mechanism of sodium nitrate with different valence sulfurs in a sodium aluminate solution is described in detail, which provides theoretical support for the desulfurization of high-sulfur bauxite in the production of alumina using the Bayer process. [ABSTRACT FROM AUTHOR]

Fly ash-bottom ash of coal is a solid waste in many industries and electric power plants. One method to reduce that solid waste is by using it to produce artificial zeolite. The Filicium decipiens charcoal was added into artificial zeolite to increase its performance to adsorb water pollutants. The pumice stone is also used in this work as a source of silica. The manufacture of artificial zeolite was carried out by the hydrothermal method by optimizing the composition of sodium silicate from Lampung pumice silica, sodium aluminate from aluminum scrap, and charcoal of Filicium decipiens. From the characterization of the LCR meter, the optimum artificial zeolite obtains the conductivity value from 9.14×10-6 (S/cm) to 6.09×10-6 (S/cm), confirming that artificial zeolite is a semiconductor material. The highest conductivity of artificial zeolite will increase its performance as a catalyst and absorbent. The composition of the artificial zeolite after XRF characterization was aluminum, silica, phosphorus, potassium, calcium, titanium, vanadium, chromium, Mangan, and ferrite. From the XRD characterization result obtained, the dominant phase is Zeolite-A. SEM-EDX characterization results obtained a spherical and cylindrical microstructure of artificial. [ABSTRACT FROM AUTHOR]

Plasma electrolytic oxidation method was used to form ceramic coatings on pure Ti substrates, using various aqueous solutions of sodium aluminate (15 g/L and 20 g/L, with or without the addition of NaOH, 2 g/L). The PEO process was carried out at constant time and voltage (300 seconds, 200 V). The ceramic coatings obtained by PEO were investigated by SEM, EDS, XRD, and XPS. Their corrosion behavior has been evaluated as well. The study aimed to understand the role of NaOH in the development of the PEO process and to evaluate the results obtained by short treatments in potentiostatic regime. [ABSTRACT FROM AUTHOR]

In this study, a certain percentage of lignin in original bamboo kraft black liquor (BKBL) was separated, and the residual BKBL with low lignin content was expected to be fed into the alkali recovery boiler to reduce the heat transfer load of the alkali recovery boiler. With the decrease in lignin content, the rheological properties/volumetric isothermal expansivity (VIE) of BKBL change. When the lignin content was 70% remaining in the original BKBL, the viscosity of BKBL with low lignin content is close to that of the passivated BKBL at the same solids content, the dynamic viscoelasticity is superior, and the VIE decreases by 57.2%. When the amount of desilication agent is 1.5%, the viscosity of BKBL with low lignin content did not change much, and the VIE increased sharply and was 62.7% higher than that of the passivated BKBL. Therefore, the combination of partial lignin separation process and sodium aluminate desilication process can effectively improve the ability of alkali recovery boiler to deal with BKBL and reduce the influence of "silicon interference". [ABSTRACT FROM AUTHOR]

The addition of active seed for increasing the precipitation rate leads to the formation of fine Al(OH)3 particles that complicates separation of solid from the mother liquor. In this study, the enhanced precipitation of coarse Al(OH)3 from sodium aluminate solution using active agglomerated seed was investigated. Aluminum salt (Al2(SO4)3) were used for active agglomerated seed precipitation at the initial of the process. About 50% of precipitation rate was obtained when these agglomerates were used as a seed in the amount of 20 g L−1 at 25 °C within 10 h. The agglomerated active seed and precipitate samples were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FTIR). SEM images showed that agglomerates consist of flake-like particles that can be stick together by bayerite (β-Al(OH)3) acting as a binder. The precipitation temperature above 35 °C and the high concentration of free alkali (αk = 1.645Na2Ok/Al2O3 > 3) lead to the agglomerates refinement that can be associated with the bayerite dissolution. [ABSTRACT FROM AUTHOR]

Aluminum alloys, along with positive properties - low density, high specific strength, electrical conductivity, ductility, viscosity and others, have disadvantages: low hardness, modulus of elasticity, wear resistance and high chemical activity in many inorganic acids. The method of microarc oxidation (MАO) can eliminate these shortcomings. The transformation of the surface layers of the workpiece into high-temperature oxides of aluminum will strengthen the surface and increase its protective properties. The properties of MАO coatings depend on many factors, one of which is the composition of the electrolyte. According to the literature, the most widely used alkaline-silicate electrolytes, which have shown the greatest efficiency in MАO of aluminum alloys. The data available in the literature on the use of multicomponent electrolytes containing sodium aluminate NaAlO2 and sodium hexametaphosphate Na6P6O18 do not allow to elucidate their role in the formation of MАO coatings. Studies of the use of hexametaphosphate to alkaline silicate electrolyte have shown that Na6P6O18 promotes the formation of a thicker coating. The rate of thickness formation in the absence of hexametaphosphate is 0.5 ,7 0.7 μm / min, and at a hexametaphosphate content of 10 g / l - 0.9 ÷ 1.1 μm / min. As for the effect on the phase composition, the effect was not detected. It was studied that the addition of aluminate-silicate electrolytes of sodium aluminate in the amount of up to 13 g / l does not have a significant effect on the thickness of the coating, but affects the phase composition of the coating.

The one-part geopolymer binder was synthesis from the mixing of aluminosilicate material with solid alkali activators. The properties of one-part geopolymers vary according to the type and amount of solid alkali activators used. This paper presents the effect of various sodium metasilicate-to-sodium aluminate (NaAlO2/Na2SiO3) ratios on fly ash-based one-part geopolymer. The NaAlO2/Na2SiO3 ratios were set at 1.0 to 3.0. Setting time of fresh one-part geopolymer was examined through Vicat needle apparatus. Mechanical and microstructural properties of developed specimens were analysed after 28 days of curing in ambient condition. The study concluded that an increase in NaAlO2 content delayed the setting time of one-part geopolymer paste. The highest compressive strength was achieved at the NaAlO2/Na2SiO3 ratio of 2.5, which was 33.65 MPa. The microstructural analysis revealed a homogeneous structure at the optimum ratio. While the sodium aluminium silicate hydrate (N-A-S-H) and anorthite phases were detected from the XRD analysis.

Geopolymer bricks from lead glass sludge (LGS) and alumina flakes filling (AFF) waste were synthesized in the present work. AFF waste was chemically treated to prepare sodium aluminate (NaAlO2) powder. Silicate source (untreated LGS and thermally treated one at 600 °C (LGS600)) and sodium oxide (Na2O) concentration (as NaAlO2) were the compositional parameters, which affected the physical and mechanical properties (compressive strength, water absorption, and bulk density) of the prepared bricks. High organic matter content inside LGS caused a retardation effect on the geopolymerization process, resulting in the formation of hardened bricks with modest 90-day compressive strengths (2.13 to 4.4 MPa). Using LGS600 enhanced the mechanical properties of the fabricated bricks, achieving a maximum 90-day compressive strength of 22.35 MPa at 3 wt.% Na2O. Sodium aluminosilicate hydrate was the main activation product inside all samples, as confirmed by X-ray diffraction and thermal analyses. Acetic acid leaching test also proved that all LGS600-NaAlO2 mixtures represented Pb concentrations in leachates lower than the permissible level of characteristic leaching procedures, indicating the mitigation of environmental problems caused by these wastes. [ABSTRACT FROM AUTHOR]

Copyright of Uzbek Chemical Journal / O'Zbekiston Kimyo Jurnali is the property of Institute of General & Inorganic Chemistry of Academy of Sciences of Republic of Uzbekistan and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Precast concrete construction is frequently preferred all over the world because of its rapid production and low cost. Prefabricated structures are constructed by assembling, the structural elements that were produced in the factory, at the construction site. However, some connection types such as wet connection used in prefabricated buildings eliminate the rapid installation feature. The wet connections are the method of assembling with fresh concrete. In the wet connections, the setting time of concrete decreases the installation rapid of prefabricated structures. In the past years, various additives have been used to accelerate the setting time. However, these additives consisting of organic salts cause corrosion in the reinforcement. In recent years, the use of inorganic salts with low ions activity as the accelerator has become widespread. Rapid-setting concrete is suitable for producing precast concrete. This paper deals with the determination of optimal accelerator type and dosage for precast concrete. Sodium aluminate and Polycarboxylic ether-based chemicals were utilized as the accelerator to obtain rapid-setting concrete mixtures. Mechanical and durability tests were performed to analyze each chemical effect on the fresh and hardened properties of the concrete mixes. Polycarboxylic ether-based chemical is observed as a potential accelerator for precast concrete, especially for the connection concrete parts. With polycarboxylic ether-based chemicals, it is observed that rapid strength gain is achieved without much loss of final strength. Besides, polycarboxylic ether-based chemicals increase the workability of mixtures. However, it is observed that the workability feature is lost in a short time due to the rapid-setting feature. [ABSTRACT FROM AUTHOR]

The synthesis and single-crystal structures of three hydride-bridged sodium aluminate compounds containing the utility amide HMDS [N(SiMe3)2 or C6H18NSi2] are reported. Both bis[bis(trimethylsilyl)amido-2κN]-μ-hydridohydrido-2·H-(N,N,N',N",N"-pentamethyldiethylenetriamine-1·³N,N',N')-(tetrahydrofuran-1κO)aluminiumsodium, [AlNa(C6H18NSi2)2H2(C4H8O)(C9H23N3)] or (HMDS)2Al(H)2Na(THF)(PMDETA), (1) (THF = tetrahydrofuran, C4H8O; PMDETA = N,N,N',N",N"-pentamethyldiethylenetriamine, C9H23N3) and tetrakis[ bis(trimethylsilyl)amido]-3κ²N,4&954;²N-tetra-μ-hydrido-tetrakis(tetrahydrofuran)-1κ²O,2κ²O-dialuminiumdisodium, [Al2Na2(C6H18NSi2)4H4(C4H8O)4] or [(HMDS)2Al(H)2Na(THF)2]2 (2), are dihydrides. However, 1 is a dinuclear Al--H--Na monomer with one bridging and one terminal hydride ligand whilst in 2 all the hydride ligands bridge between Al and Na atoms to give a dimeric structure with a core (AlHNaH)2 eight-membered ring. In contrast, the structure of bis[bis(trimethylsilyl)amido]-3κN,4κN-dihydrido-3κH,4κHtetra-μ-hydrido-bis(N,N,N',N",N"-pentamethyldiethylenetriamine)-1κ³N,N',N";-2κ³N,N',N"-dialuminiumdisodium, [Al2Na2(C6H18NSi2)2H6(C9H23N3)2] or [(HMDS)Al(H)3Na(PMDETA)]2 (3), also contains a (AlHNaH)2 eightmembered ring but is a trihydride with two bridging and one terminal hydride ligand per Al centre. The (AlHNaH)2 eight-membered rings of 2 and 3 differ in their structural details. That of 2 is based around a twofold axis and has a larger Al· · ·Al intra-ring distance than that found in centrosymmetric 3. [ABSTRACT FROM AUTHOR]

Copyright of Applied Chemical Industry is the property of Shaanxi Research Design Insitute of Petroleum & Chemical Industry and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The high concentration of potassium in sodium aluminate solution seriously threatens the seed precipitation process and reduces the quality of alumina products, but the separation of potassium is quite difficult due to the similar chemical properties between potassium and sodium ions. In this work, a novel single-step double salt crystallization (SDSC) process with low energy consumption was proposed to remove potassium from the concentrated sodium aluminate solution using sodium sulfate, and the corresponding removal performance, kinetics and mechanism were studied. The potassium concentration decreases with the increase of additive dosage and reaction temperature, while the high caustic alkali concentration hinders the potassium removal. At 70 °C, the SDSC process exhibits a rapid crystallization and reaches an equilibrium within 60 min because of the low activation energy and weak bonding of 3 K 2 SO 4 ·Na 2 SO 4 ·9H 2 O. Under the optimum conditions, the potassium removal efficiency can achieve 85.68 %, and the potassium concentration is reduced from 120 g∙L−1 to 24.54 g⋅L−1. Finally, a cyclic utilization pathway was obtained to economically and effectively remove potassium from the sodium aluminate solution. [Display omitted] • A novel SDSC process was proposed to remove potassium from the Bayer liquor. • Over 85 % potassium was removed under the optimal conditions. • The kinetics and mechanism of potassium removal were obtained. • The crystallized products can be treated by salt separation for Na 2 SO 4 recycling. [ABSTRACT FROM AUTHOR]

The influence of process parameters in the three-stage purification of aluminate solution from the Bayer process and aluminum hydroxide was considered in this paper. One of the ways of purification is treating the aluminate solution in order to reduce the concentrations in the starting raw material (solution) and then treating the aluminum hydroxide at a certain temperature and time in order to obtain an alumina precursor of adequate quality. The purification process itself is divided into three phases. The first phase involves the treatment of sodium aluminate with lime in order to primarily remove Ca2+ and (SiO3)2− impurities. Phase II aims to remove impurities of Zn2+, Fe2+, and Cu2+ by treatment with controlled precipitation using specially prepared crystallization centers. In Phase III, Na+ is removed by the process of hydrothermal washing of Al2O3 ∙ 3H2O. In this work, parameters such as temperature (T), reaction time (t), and concentration of lime (c) were studied in order to remove the mentioned impurities and obtain the purest possible product that would be an adequate precursor for special types of alumina.

This paper investigates the effect of varying solid alkali activators on the fresh and hardened properties and microstructural changes of one-part geopolymers (OPGs). Single and binary solid alkali activators were used to activate high calcium fly ash. The alkali activators were either solely sodium metasilicate (Na2SiO3) or a combination of sodium aluminate (NaAlO2) and sodium metasilicate (Na2SiO3). The OPG activated with anhydrous Na2SiO3 achieved an excellent 28-day compressive strength of 83.6 MPa while OPG activated with NaAlO2 and Na2SiO3 attained a compressive strength of 45.1 MPa. The Na2SiO3-activated OPG demonstrated better fluidity than the OPG activated with NaAlO2 and Na2SiO3 due to the thixotropic behaviour caused by the NaAlO2. The Na2SiO3-activated OPG consisted of sodium-calcium aluminium silicate hydrate ((N,C)-A-S-H) gel phase, while the OPG activated with NaAlO2 and Na2SiO3 comprised of the coexistence of sodium aluminium silicate hydrate (N-A-S-H) and calcium aluminium silicate hydrate (C-A-S-H) gel phases. Regardless of the distinctive properties, the OPGs are adequate for building materials applications.

The objective of this study was to explore the influence of an alkali liquid accelerator based on sodium aluminate (ASa) on the early hydration behaviour of cement paste, tricalcium aluminate (C3A) and tricalcium silicate (C3S) and identify its accelerating mechanism. The setting times and mechanical properties of cement paste and mortar mixed with different amounts of ASa were determined. Isothermal calorimetry showed that the addition of ASa increased the first exothermic peak of cement hydration and advanced the second exothermic peak. The morphology of hydration products was analysed by scanning electron microscopy (SEM) and a model for the early hydration of cement paste was established. X-ray diffraction and SEM were also used to analyse the phase composition and morphology changes of C3A and C3S with or without ASa and early hydration models were established. Analysis of the experimental results revealed that the sodium hydroxide produced by ASa hydrolysis had the function of consuming gypsum, breaking calcium silicate hydrate gel film and increasing the calcium hydroxide concentration in the cement paste. The ettringite in the hydration products interweaved together to form a skeleton structure, which was conducive to cement paste hardening. [ABSTRACT FROM AUTHOR]

Geopolymers based on natural zeolite clinoptilolite were activated with different concentration of sodium aluminate and potassium hydroxide and the influence on compressive strength, density and water absorption were evaluated. The microstructure was analyzed by XRD, FTIR and SEM. The obtained geopolymers are comprised of newly formed zeolite phases - phillipsite, zeolite A. [ABSTRACT FROM AUTHOR]

In this paper, the physical and mechanical properties of TISCO steel slag were tested by different ratios of composite activators. The optimal neutral composite activator was determined, and the properties of neutral activated steel slag power-cement composite cementitious material with 30% cement content were studied. The experimental results indicated that the best ratio of gypsum: silica fume: sodium sulfate: sodium aluminate: selfmade activator was 2.5:2.5:1:0.5:0.5. Through XRD, SEM and TG-DTG detection, less stable periclase was found at 30% cement content and activated steel slag slurry. After 28d curing, the micro morphology and compactness of hydration products were not different from those of cement, and there were even no incompletely hydrated particles. The voids between hydration products and the interface of different hydration products were continuously filled with hydration products over age. C-S-H and AFt generated by 7d activated SSP cement composite powder was greater than those of cement. At 28d, a small amount of Ca(OH)2 was generated. The results show that the combination of self-made neutral activator and other activators can improve the properties of cement steel slag powder composite cementitious material and improve the utilization rate of steel slag. [ABSTRACT FROM AUTHOR]

This study investigates applying the principles of the long-discontinued Pedersen process as a possible route for producing metallurgical grade alumina from low-grade and secondary feed materials. The investigation focused on the hydrometallurgical steps in the process, namely leaching, desilication, and precipitation, and adapting it to valorize bauxite residue. The test material used was a calcium–aluminate slag made by the smelting-reduction of a mixture of bauxite residue (dewatered red mud) and a calcium-rich bauxite beneficiation by-product. Samples of the slag were leached in a 1 L jacketed glass reactor with Na2CO3 solution, varying Na2CO3 concentration and leaching time. Additionally, different approaches to leaching involving mechanical treatment of the leached slag and re-leaching using either fresh or recycled solution were also explored. The desilication step was carried out by treating the leachate solution with powdered CaO, varying the amounts of CaO used. Finally, the desilicated leach solution was sparged with a CO2 gas mixture, after which the precipitate was allowed to age in the solution. The carbonation and aging temperatures and times were varied. As much as 67% of the Al was leached from the slag. The desilication process successfully removed 88% of the Si. The precipitation process produced a product composed mostly of bayerite [Al(OH)3], but some tests had considerable amounts of the unwanted phase dawsonite [NaAlCO3(OH)2]. The results indicated that the highest Al recovery was obtained using low concentrations of Na2CO3 solutions, and aluminum tri hydroxide is formed from these solutions at low temperatures at a fast rate compared to higher solution concentrations and temperatures. [ABSTRACT FROM AUTHOR]

The processes of reagent purification of aqueous solutions from sulfates when using the red slime of the Mykolayiv Alumina Plant were investigated in this work. According to chemical analysis, this slime contains a sufficient amount of alumina (up to 18 %) and calcium oxide (up to 10 %) and along with calcium silicate and iron oxides contains sodium and calcium aluminate. The ability of sodium aluminate to precipitate from a solution of sulfates in the form of calcium sulfoaluminate was used in the work to purify water from sulfate anions. The process takes place when treating the solution with sludge and lime suspension. The extraction of sulfates was achieved at the level of 64-75%. The dependence of the efficiency of sulfates extraction on their initial concentration is determined. It is shown that at the initial concentration of sulfates of 20 mg-eq/dm3 at a lime consumption of 2-10 mg-eq/dm3 at a sludge consumption of 1 g/dm3 the residual concentration of sulfates decreases to 7.8-9.1 mg-eq/dm3. At a sulfate concentration of 40 mg-eq/dm3, the concentration of sulfates decreases to 10.8-21.2 mg-eq/dm3 at a lime consumption of 30 mg-eq/dm3, regardless of the sludge consumption. [ABSTRACT FROM AUTHOR]

The effects of sodium aluminate (NA) and reverse-osmosis brine (RW) on alkali-activated slag cement (AASC) using sodium hydroxide and sodium silicate as activators were investigated. NA was mixed at 0%, 2.5%, and 5.0% by binder weight, and the mix waters tested were tap water (TW) and RW. In the experiment NA showed the effect of improving the compressive strength, with the highest strength value obtained at 2.5%. However, the strength improvement effect of NA was more clearly demonstrated in RW samples than in TW samples. Changes in the C4AH13 (Tetracalcium aluminate hydrate; Ca4Al2(OH)14.6 H2O), C2ASH8 (stratlingite; Ca2Al2SiO7.8 H2O), and C3AH6 (katoite; Ca3Al2(OH)12) phases were observed according to the increase in NA through hydration reaction analysis. Friedel’s salt (Ca4Al2O6Cl2.10 H2O) was additionally observed in the RW sample. In the TW samples, more of the C3AH6 phase was formed than in the RW samples, which affected the strength reduction. In the RW samples, increases in the chloride ions and calcite phase in the pore solution due to carbonation of Friedel’s salt were confirmed. This phenomenon of the RW samples became more pronounced as the NA concentration increased. The technique of utilizing RW in AASC showed the possibility of being used as a novel stabilization/solidification method for reverse osmosis brine.

The whey of sweet cheese was used as a raw material for preparing high fructose high tagatose whey syrup. The whey proteins were precipitated through a boiling treatment. Whey lactose was hydrolysis by using different concentrations of citric acid (0.8, 1.6, 2.4 and 3.2%) for 2hr at boiling point. It was found that the hydrolysis by using 3.2% citric acid was more efficient. The lactose hydrolysate consist of 36.48% glucose, 43.76% galactose, 07.92 lactose and 11.84% degradation (unidentified sugars). The previous lactose hydrolysate was subjected to isomeriaztion reaction by using different molarties of sodium aluminates (1, 2 and 3) for various periods of time (2, 4, 6, and 8 hr) at different temperatures (30, 50, 70 and 90oC). There were direct relationships between degree of isomerization and catalyst molarity, time, and temperature. High sodium aluminates molarity at high temperature for long time was associated with high fructose, high tagatose, high lactulose and high percentages of degradation. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Northeastern University (Natural Science) is the property of Dongbei Daxue Xuebao and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Invited for this issue's Front Cover is the groups of Grey and Wright. The cover picture shows the chemical structure of sodium tetrakis(hexafluoroisopropyloxy)aluminate, with the sodium ion in the beach ball and the aluminate anion floating in a pool. The cover art uses a pool theme as the sodium aluminate salt synthesised in this work is a room‐temperature ionic liquid, thus the sodium salt in the pool represents this. The application of the salt in a sodium‐ion battery is shown in the cover design with the diving board acting as a battery, which can be seen by the positive and negative signs. Cover design by Demelza Lee. Read the full text of the Research Article at 10.1002/celc.202300381. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Chemistry & Technologies is the property of Oles Honchar Dnipro National University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Precious Metals / Guijinshu is the property of Precious Metals Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The sodium aluminate solution of the evaporation process is provided for the digestion process to recycle useful resources, decrease alkali concentration in waste solution, and reduce environmental pollution. However, the concentration of recycled sodium aluminate solution as an indispensable indicator for manipulating the evaporation process of the industrial alumina production is acquired offline leading to delayed feedback information. To ensure stable production of the subsequent process, reduce energy, and resource consumption, this article focuses on developing a hybrid prediction model for recycled sodium aluminate solution concentration in evaporation process. First, data reconciliation is utilized to improve the quality of material flow information, and the process mechanism model is established through mechanism research and equilibrium principle to obtain the concentration prediction result. Moreover, an industrial production condition analysis as well as fuzzy expert rules, are introduced for modifying prediction results from the mechanism model. Furthermore, the errors are predicted by the kernel extreme learning machine (KELM), and a concentration prediction model integrated error compensation results and modified predictions are established. The experimental simulations and industrial applications show that the accuracy of the prediction error obtained by the proposed model reaches 90% within ±2%, and the advantages of the hybrid model are particularly prominent under different conditions, which is beneficial for efficient and clean production. [ABSTRACT FROM AUTHOR]

Copyright of Precious Metals / Guijinshu is the property of Precious Metals Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Clean Coal Technology is the property of Clean Coal Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Carbonate is the main anionic impurity in alumina produced by the Bayer process. The phase composition, morphology, and precipitation activity of desilication products (DSPs) precipitated at 245°C in sodium aluminate solution with different carbonate concentrations have been investigated by x-ray diffraction (XRD) and scanning electron microscopy–energy-dispersive x-ray spectroscopy (SEM–EDS) methods. The crystalline DSPs without carbonate are composed of zeolite, sodalite, and hydroxy-sodalite, but only zeolite and cancrinite precipitate in the presence of carbonate. Increasing the carbonate concentration promotes the precipitation of cancrinite but reduces the crystallinity of various DSPs. The cell parameters and the Na2O/Al2O3 ratios of DSPs are significantly increased because of the entry of sodium carbonate during crystallization, especially for the cancrinite. The morphology of various DSPs is greatly changed by the carbonate. The amorphous phase content and precipitation activity of DSPs increase with increasing carbonate concentration. This contributes to the effective removal of carbonate from sodium aluminate solution by controlling the desilication process. [ABSTRACT FROM AUTHOR]

Zeolite 4A is crystalline microporous sodium aluminosilicate having many applications. Intensive work is being undertaken worldwide to synthesis zeolite using different aluminium and silicon sources. In this work chemical composition of indigenous bauxite was evaluated using XRF and alumina was extracted by calcination process. High quality zeolite 4A was synthesized from sodium aluminate extracted from bauxite of Khushab area, Pakistan, and commercial sodium silicate by hydrogel process without the addition of organotemplates. The SEM and XRD confirm the formation of Zeolite 4A. Performance of the prepared zeolite was also evaluated for its metal exchange rate. [ABSTRACT FROM AUTHOR]

Extensive research into alkali-activated slag as a green gel material to substitute for cement has been done because of the advantages of low-carbon dioxide emissions and recycling of industrial solid waste. Alkali-activated slag usually has good mechanical properties, but the too fast setting time restricted its application and promotion. Changing the composition of alkaline activator could optimize setting time, usually making it by adding sodium carbonate or sodium sulfate but this would cause insufficient hydration reaction power and hinder compressive strength growth. In this paper, the effect of sodium aluminate dosage as an alkaline activator on the setting time, fluidity, compressive strength, hydration products, and microstructures was studied through experiments. It is fair to say that an appropriate amount of sodium aluminate could obtain a suitable setting time and better compressive strength. Sodium aluminate provided enough hydroxyl ions for the paste to promote the hydration reaction process that ensured obtaining high compressive strength and soluble aluminium formed precipitate wrapped on the surface of slag to inhibit the hydration reaction process in the early phase that prolonged setting time. The hydration mechanism research found that sodium aluminate played a key role in the formation of higher cross-linked gel hydration products in the late phase of the process. Preparing an alkali-activated slag with excellent mechanical properties and suitable setting time will significantly contribute to its application and promotion. [ABSTRACT FROM AUTHOR]