Sodium Metasilicate Solution Research Articles

Binding properties of synthesized CS glasses activated by alkaline components

The paper presents the synthesis and evaluation of hydration and binding properties of individual minerals with glass-like structures in silicate systems, most often found in technogenic materials based on phosphorus and blast furnace slags. This work aims to determine the optimum composition of CS glasses to obtain binders with given properties, the hydration of glasses of different silicate and aluminosilicate compositions in the presence of solutions of soda, sodium hydroxide, and sodium metasilicate was investigated. The results of X-ray phase and differential-thermal analysis, and infrared spectrum are given, and the hydration structure of the calcium oxide-silicon oxide-alkali component system has been studied. The analysis of hydrate neoplasms of the studied binding systems shows that the most optimal conditions for the synthesis of stone strength with stable physical and mechanical properties are created in the presence of gel-like phase reinforced by hydrosilicates and hydroaluminosilicates of alkaline and alkaline-alkaline-earth composition, characterized by fiber-like structure and possessing the ability to epitaxial fusion with each other, as well as gel-like phase, which they reinforce.

Preparation of C-S-H gels by mechanochemistry and its influences on properties of super-retarded cement-based materials with sucrose

In this paper, low-cost dihydrate gypsum (CaSO4⋅2H2O) was used as calcium source together with sodium metasilicate solution to prepare calcium silicate hydrate (C-S-H) gels through a mechanochemical activation strategy by using planetary and vibrational ball-milling. The influences of the prepared C-S-H gels on hydrating and hardening properties of super-retarded cement-based materials with sucrose were investigated. The results showed that CaSO4⋅2H2O reacted with sodium metasilicate solution under mechanochemical effect during both planetary and vibrational ball-milling, although CaSO4⋅2H2O was just slightly dissolved in water. It was also interestingly found that the C-S-H gels can continuously form while resting for a certain time after ball-milling. Under the mechanochemical activation, the prepared C-S-H gels had complete characteristic diffusion peaks and were composed of layered, flocculent and fibrous structures. While incorporating the prepared C-S-H gels into the super-retarded cement paste with sucrose, the cement hydration was greatly accelerated and the compressive strength of the hardened cement-based materials was also effectively improved at early age as expected. Through X-ray diffraction (XRD) analysis, it was found that C-S-H gels can effectively promote the growth of CH crystals along the (001) and (101) crystal planes. The scanning electron microscopy (SEM) results supported that the C-S-H gels inhibited the refinement of ettringite (AFt) crystals in super-retarded HCP with sucrose, which was more obvious at 28 d.

Geopolymers for Space Applications

Geopolymers are cementitious materials with exceptional mechanical and physical properties, making them suitable for aerospace applications. Considering their excellent performance, the present investigation aims to develop geopolymers with designed physical properties to address some issues in the aerospace industry. In this sense, the influence of the alkaline activator on the final properties was evaluated. For the development of the geopolymers, sodium hydroxide and sodium metasilicate solutions were preparedto obtain the alkaline activator. The synthesis process also consisted of a mixing stage using a mixer to obtain a homogenous paste. After mixing, the curing process consisted of a first thermal treatment at 60 °C for 4 h to evaporate the excess water, avoid excessive contraction, and promote strength at early ages. Subsequently, the geopolymers were left at rest for 28 days until the final properties were achieved. The influence of the solid-to-liquidratio (S/L) on the microstructure of the geopolymers was evaluated. For this purpose, X-ray fluorescence spectrometry, X-ray diffraction, and infrared spectrometry analyses were performed. The results show that the content of the alkaline activator promotes variations inthe presence of different crystalline phases, which is more noticeable as the S/L ratio increases. Likewise, the infrared spectra display peaks at different wavelengths regarding the variations in elemental composition, which are more evident with the changes in the S/L ratio. In addition, physical studies, such as thermal conductivity and resistance to gamma radiation were conducted for different geopolymer compositions. The results indicate that changes in properties are not too sensitive to compositional variations, although slight modifications exist. Finally, these studies are significant as aerospace-focused materials are directly exposed to this kind of phenomena. The designed geopolymers have to be able to resist and maintain their properties through exposure to any energy.

Mechanical and microstructural characteristics of structural concrete containing RCA treated with sodium metasilicate

Purpose One of the most contested and anticipated research issues is the acceptability of using recycled aggregates instead of fresh aggregates. This study aims to look at the possibility of replacing fresh aggregates with 15%, 30%, 60% and 100% recycled aggregates. Design/methodology/approach The research is divided into two stages. The compressive, split tensile, flexural and bond strength of the various mixes were examined in the first phase using untreated recycled concrete aggregates (RCA). The second phase entails chemically treating RCA with a 10% 0.1 M sodium metasilicate solution to evaluate differences in strength, indicating the success of the treatment performed. Microstructural experiments such as scanning electron microscopy and X-ray diffraction were also conducted to evaluate the formation of interfacial transition zone (ITZ) in treated and untreated RCA specimens. Findings The observed findings reveal a decrease in concrete strength with increasing RCA concentration; however, when treated RCA was used, the strengths increased significantly when compared to untreated samples. The findings also include curves indicating the correlation between compressive strength and other mechanical strength parameters for an optimum mix of concrete prepared with 30% RCA replacement. Originality/value The study through its novel approach, demonstrates the effect of pretreatment of RCA in the absence of any standardized chemical treatment methodology and presents significant potential in minimizing reliance on fresh aggregates used in concrete, lowering building costs and promoting the use of waste materials in construction.

Aerated Concrete with Geopolymer Binder from Technogenic Waste

Aerated concrete is a material widely used in Vietnam due to several advantages over heavy concrete. This article presents some results of experimental studies of the properties of aerated concrete produced using geopolymer binder from industrial waste generated in large quantities in Vietnam. The raw materials used included thermal power plant fly ash, blast furnace slag, ceramic powder, aluminum powder and an activating alkaline solution consisting of aqueous solutions of sodium hydroxide and sodium metasilicate. Testing of aerated concrete samples of the developed compositions was carried out in accordance with current Russian and Vietnamese standards. Experimental results confirmed the possibility of producing aerated concrete with a geopolymer binder based on large-tonnage technogenic waste, with an average dry density of less than 1600 kg/m3 and a compressive strength at the age of hardening of 28 days of 18.8–27.9 MPa. At the same time, aerated concrete containing 0.456 kg/m3 of aluminum powder and 50% wt. showed the greatest strength. blast furnace slag in the composition of the geopolymer binder, with a ratio of activating alkaline solution and active mineral additives equal to 0.4.

Eco-friendly lightweight composite prepared with a geopolymer and wheat straw

Agricultural waste shows promise for use in lightweight building materials. The combination of a geopolymer and wheat straw (WS) is adopted to produce a kind of eco-friendly lightweight composite. Using WS pretreated with sodium hydroxide (NaOH) and sodium metasilicate (Na2SiO3) solutions, the influence of WS on the properties of the geopolymer–WS composite (GWSC) is investigated. The pretreated WS avoids the retarding effect of the untreated WS on the hydration of the geopolymer and even presents an accelerating effect. Increasing the content of pretreated WS generally results in a reduction in apparent density and strength. A GWSC with an apparent density of 1000–1500 kg/m3 can be prepared, corresponding to a 28-day compressive strength between 5 and 25 MPa. The water absorption linearly increases with the increase in the pretreated WS content, while an appropriate amount of the pretreated WS can enhance the water resistance of the GWSC. A WS/fly ash ratio lower than 8% can produce a GWSC with qualified thermal insulation performance. Alkaline treatment, particularly sodium hydroxide treatment, significantly improves the bonding strength between the fiber and the geopolymer matrix. In addition, pretreated WS saturated with sodium hydroxide and sodium metasilicate solutions is beneficial to the fluidity of the geopolymer–WS mixture and could act as an internal curing agent for enhancing the hydration of the geopolymer.

Avaliação de concreto autocicatrizante através do encapsulamento de metasilicato de sódio em perlita e argila expandidas

abstract: Investigating the behavior of self-healing cementitious composites is necessary to know alternatives that can be applied in structures increasing their life service. Therefore, this study evaluated concrete self-he aling from the use of expanded perlite (EP) and expanded clay (EC) capsules impregnated with a sodium metasilicate solution. These materials were used to substitute natural aggregates in concrete in proportions of 0 wt·%, 15 wt·% and 30 wt·% which were cured in humid or submerged environments. Cracking was induced with a flexural test and a closing with cicatrization product. was evaluated and measured visually with a software. Capillary absorption tests indicated a reduction in the porosity of samples which incorporated self-healing materials, considering it as an important property related to durability. Samples with EP achieved 100% self-healing with 15% substitution. Crack filling was achieved in cracks up to 0.43 mm wide. Samples with EC achieved 50% crack recovery under humid curing and 90% under submerged curing. It was concluded that incorporating the sodium silicate allowed improvements to fissure sealing and it is an alternative to produce self-healing concrete in Brazil. EP was more effective than EC as encapsulating material. Despite that, the EP did not impact the compressive strength due to its small size and better packing of the mixture, Also, EP presented higher healing percentage when comparing with samples containing EC.

Efficacy of pond ash (PA) combined with ground granulated blast furnace slag (GGBFS) in producing cement-less mortar

In this research, an attempt has been made to produce cementless construction materials utilizing industrial wastes, e.g., pond ash (PA) and ground granulated blast furnace slag (GGBFS) as binder materials, followed by alkali activation using a mixture of sodium hydroxide (NaOH) and sodium metasilicate (Na2SiO3) solution. In this study, two types of samples, i.e., alkali-activated paste (AAP) and alkali-activated mortar (AAM) were prepared. The AAP samples were prepared to evaluate the setting times, hydration behavior (by monitoring hydration temperature as the function of time), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM). Analyzing the results, it is revealed that AAP samples sets within the standard time range (initial and final setting times are 55 and 105 min, respectively). The compressive strength analysis of the AAM sample (prepared using the same binder composition with a binder to fine aggregate ratio = 1: 3) is measured to be ∼12 MPa after 28 days of ambient curing. The setting and the hardening ability of AAP and AAM samples appear to be due to the pozzolanic reaction of PA and GGBFS with alkali activators, which is verified by the formation of hydrated products as demonstrated by the FTIR, XRD, and SEM analysis. Finally, a comparative study has been done to assess the reduction of CO2 emission for the use of PA-GGBFS binary mixture in the construction sector replacing the cement.

Study of sorption processes for corn oil refining

Studies have summarized and analyzed the structure of an aqueous sodium silicate solution, which showed their dual nature. On the one hand, they exhibit the properties of electrolytes, and on the other hand, they contain monomeric alkali metal cations and polymeric silicon-oxygen anions. The use of an aqueous solution of sodium metasilicate with a silicate modulus equal to 1, in which polyanions predominate, is substantiated for the process of chemisorption purification of unrefined corn oil. A comparative analysis of the methods of purification of unrefined and hydrated vegetable oils pretreated in an electromagnetic field with solutions of organic acids and sodium silicate is carried out. Obviously, when purifying unrefined corn oil with an aqueous solution of sodium silicate, there is a complex mechanism of the sorption process with various groups of polar accompanying substances, complicated by chemical interactions. On the basis of planned experimental studies, adequate experimental-statistical models were obtained for calculating the soap content in the resulting corn oil and its yield, depending on the studied process parameters. It was found that in the studied range of temperatures and parameters of an aqueous solution of sodium silicate, corn oil is obtained according to the acid number corresponding to the Russian National Standard for refined corn oil. The optimal parameters of the chemisorption purification process in terms of temperature, concentration and dosage of sodium silicate with a silicate modulus equal to 1 are experimentally substantiated when the Reynolds criterion of the mixer is changed in the studied range from 4000 to 12000, ensuring the production of corn oil corresponding to the accepted quality parameters.

A new method of full resource utilization of copper slag

Copper slags can hardly be utilized because the fayalite in it produces silica gel during the dissolution process. This work proposes a new process on sulfuric acid treatment of copper slag (Jinchuan Group, Gansu Province, China.). The results show that over 98% of recovery efficiency of Cu2+, Co2+, Ni2+ and Zn2+ was achieved through the whole process cycle. Ammonia was used to control the pH of the solution in order to completely precipitate Fe2+, and then produce hematite powder. More than 85% of the non-ferrous metal ions were left in the solution, and the utilization method of stepwise extraction was evaluated. The generation of silica gel during the acid digestion of copper slag was not restricted, and the silica gel in the acid-leach residue was subsequently dissolved with NaOH solution to obtain sodium metasilicate solution. Acidification and other steps were carried out to produce high-purity silica with a purity of 99.9%. Magnetite and pyroxene were obtained by using a simple magnetic separation process to segregate the remaining slag phase. The whole process achieves the full resource utilization of copper slag, and exhibits great potential for the future industrial utilization of copper slag in an economically and environmentally friendly way.

Potential one-pot synthesis of spherical magnesium silicate powder by mechanical milling

Synthetic magnesium silicate finds applications in adsorbents, catalysis, pharmaceuticals, foods, cosmetics, and in oil industry. This study introduces a method for potential one-pot preparation of narrowly sized, spherical magnesium silicate powders. After initial synthesis by precipitation from magnesium sulphate and sodium metasilicate solutions, the magnesium silicate precursor was ball-milled with two immiscible liquids, forming a particle-loaded emulsion. Hexane formed the continuous phase; the droplet phase was formed by either acetonitrile, methanol, or water-methanol mixtures. Suspended precursor particles were refined, their fragments became trapped in the droplets, where they were eventually compacted into composite spheres. Prepared spherical powders were characterized using scanning electron microscopy, nitrogen sorption, and low angle laser light scattering. The synthesized powders exhibited narrow size distributions with modes from 3.3 to 92 μm. The spherical powders showed an enhanced flowability and had specific surface areas comparable to or higher than the precipitated precursor powders.

Sodium metasilicate solution enhances drought stress tolerance by improving physiological characteristics in apple stocks

Sodium metasilicate solution treatment contributes to improved plant tolerance to drought stress. In this study, pot experiments were conducted to compare the effect of sodium metasilicate solution on Malus halliana and Malus hupehensis seedlings under drought stress. Principal component analysis (PCA) was used to evaluate the effects of sodium metasilicate solutions on gas exchange, fluorescence, and physiological characteristics. Forty days after transplantation, the control (75% field capacity (FC)) and treatment 1 (50% FC) seedlings were sprayed with distilled water, and the other treatment (50% FC) seedlings were sprayed with a sodium metasilicate (Na2SiO3·9H2O) solution at different concentrations. The results showed that the growth of M. halliana and M. hupehensis was inhibited when exposed to drought stress. This adverse effect was reversed by applying sodium metasilicate solution, and there was a significant concentration effect. Compared to the control, sodium metasilicate solution increased the proline (Pro) content. At the same time, the decrease in the SPAD values, net photosynthetic rate (P n), stomatal conductance (G s), transpiration rate (T r), initial fluorescence (F 0), maximum fluorescence (F m), photochemical efficiency (F v/F m), electron transfer rate (ETR), and superoxide dismutase (SOD) activity were effectively controlled. The increase in intercellular CO2 concentration (C i) and malondialdehyde (MDA) content was also restricted. Additionally, the PCA showed that the first principal component of M. halliana accounted for 80.42% variance, contributed by P n, T r, G s, Pro, SOD, F v/F m, and ETR. The first principal component of M. hupehensis accounted for 69.72% and mainly contained P n, SPAD, and F v/F m index information. The PCA evaluation showed that the effect of sodium metasilicate solution on M. halliana and M. hupehensis seedlings under drought stress was most significant (p < 0.05) at concentrations of 2.5 and 3.75 mM·L−1, respectively.

Катализатор на основе бентонитовой глины, модифицированной метасиликатом натрия для гетерогенного процесса типа Фентона – Раффа

Natural bentonite clay with a montmorillonite content of 98 %, modified with a solution of sodium metasilicate, has high catalytic activity in the reaction of oxidative degradation of organic azo dyes with hydrogen peroxide by the Fenton-Ruff mechanism in a neutral medium. The activity is due to the presence of iron cations contained in the structure of montmorillonite, as well as protonated silanol and aluminol groups on the surface of the edges of aluminosilicate layers, which are the acid centers of Brensted. The degree of conversion of azo dye from cinema blue with an initial concentration in a solution of 20 mg/l was 99 % in 4 – 6 minutes of contact, at room temperature. The resulting material is well filtered and can be recommended for wastewater treatment from organic substances.

Performance of geopolymer foams of blast furnace slag covered with poly(lactic acid) for wastewater treatment

This research investigated a new method to produce geopolymer foams from blast furnace slag (BFS) with poly(lactic acid) (PLA) covering the developed porosity into the materials. A porous alkali-activated material was developed, and a biodegradable polymer was used to cover the geopolymer in the bulk state. Geopolymer foams were synthesized with a sodium metasilicate solution, and the porosity was developed by adding hydrogen peroxide (H 2 O 2 ). Foams of materials were produced with two stoichiometries of 1.4 and 1.6 g/L between solid/liquid with a hydrogen peroxide solution. The dimensional stability was achieved after coating geopolymer foams with PLA, improving the molding capacity on different geometries for the composite materials. Specimens of the geopolymer foam/PLA composites were characterized by X-ray fluorescence (XRF), Fourier transformed infrared (FTIR), thermogravimetry (TGA), and field emission gun scanning electron microscopy (FEG-SEM). The permeation analysis of metal oxide particles through the composites foam specimens was performed using water dispersions containing bismuth oxide or titanium oxide. The test resulted in high performance in the retention of particulate materials. The highlights of the results indicated the efficiency in the synthesis of geopolymer foam, a good formation of porosity, and an effective PLA coating on the internal interfaces of geopolymer foam through the development of a new bulk state coating method, improving the dimensional stability and the retention of bismuth and titanium oxides particles by the produced geopolymer foams for water depollution.

Development of novel geopolymeric foam composites coated with polylactic acid to remove heavy metals from contaminated water

As an alternative for ordinary Portland cement, geopolymers are cost effective materials that can be prepared with relatively low energy consumption and substantial reduction of CO2 emissions. In the present study the characteristics of novel hybrid composite of geopolymer foam (GPF)/polylactic acid (PLA) and their efficiency in removing copper(II) and zinc(II) to treat high volumes of polluted water are investigated. Contrary to the conventional methods for removing heavy metals, the newly developed composites are ecological, low-cost, easily available, and economically viable alternatives providing good physical-chemical stability, ion-exchange properties, and a porous structure. Based on the sustainable advantage to produce geopolymers from recycled materials, GPFs were obtained from blast furnace slag (BFS) by reacting 20 ml of an 8 M alkaline solution of sodium metasilicate (Na2SiO3) with BFS particles and later addition of hydrogen peroxide. GPFs were produced with a stoichiometry of 1.4 and 1.6 g/L between BFS/alkali solution with a 1.6 ml solution of hydrogen peroxide 50% to develop porosity into the materials. Finally, the GPFs were coated with PLA. Specimens of GPF/PLA composites were characterized by X-ray fluorescence spectroscopy, Fourier transformed infrared spectroscopy, thermogravimetric analysis, dynamic mechanical analysis, and field emission gun scanning electron microscopy. Adsorption analysis of Cu(II) and Zn(II), as well as ion-exchanges from aqueous solution through the composite with 1.4 and 1.6 stoichiometry, were performed using deionized water containing 0.80% Cu(II) or Zn(II). The test resulted in high performance for retaining Cu(II) and Zn(II). Under CO2 pressure at 50 bar, the gas permeation tests confirmed porous formations into the geopolymer foams coated with molten PLA.

The effect of sodium metasilicate on the three-dimensional chondrogenesis of mesenchymal stem cells.

The benefits of different silicic concentrations on chondrogenesis of mesenchymal stem cell (MSC) are unclear. Here an in vitro scaffoldless model was used to determine the impact of different silicic concentrations on the three-dimensional chondrogenesis of MSCs. Sodium metasilicate solutions were used as the source of silica, and were added in the chondrogenic medium and replenished every 3 days. The thickness and area of cartilage; the expression of collagen II, aggrecan, and the collagen type II/I ratio; the glycosaminoglycan and cell contents; and the tangent modulus of the constructs were all significantly higher in 100 and 200 ng/mL groups compared with those in 0 and 10 ng/mL groups. All the above parameters, as well as several mechanical parameters of cartilage constructs were highest in 200 ng/mL group. Thus, 200 ng/mL sodium metasilicate could promote the chondrogenic differentiation of MSCs and the mechanical and biochemical properties of the cartilage constructs.

KINETIC AND THERMODYNAMIC ADSORPTION STUDIES OF METHYLENE BLUE ONTO ZEOLITE FROM AQUEOUS SOLUTION

Zeolite was synthesized via hydrothermal method from sodium metasilicate and sodium aluminate solutions. The prepared sample was characterized by Fourier transform infrared (FTIR) spectroscopy, Scanning electron microscopy (SEM) and X-ray diffraction (XRD).The adsorption of methylene blue dye onto zeolite was studied. The adsorption experiments were carried out in batches and the effect of parameters such as concentration, pH, adsorbent dosage, temperature and contact time were investigated. The experimental data were fitted into the Langmuir and Freundlich Adsorption Isotherm. The result was fitted into pseudo- first order and pseudo- second order kinetic models. The thermodynamic parameters were also evaluated. The results revealed that maximum adsorption of methylene blue dye was achieved at a concentration of 20 mg/L and pH of 8.9. The adsorption process followed a Langmuir adsorption isotherm model with a correlation coefficient value of 0.9911. The negative value of standard enthalpy of adsorption, ΔHo calculated as -9.4 kJmol-1 revealed the exothermic nature of the adsorption process, the negative value of standard entropy of adsorption, ΔSo evaluated as -20.6 Jmol-1K-1showed that no significant change occurs in the internal structures of zeolite during the adsorption process and the negative value of Gibbs free energy, ΔGo obtained as -3.28 kJmol-1indicated the spontaneity of the adsorption process

Evaluation and characterization of geopolymer foams synthesized from blast furnace with sodium metasilicate

This study concerns the synthesis of geopolymeric foams from blast furnace slags, comparing the results of the produced materials using 8 M alkaline solutions of sodium metasilicate (Na2SiO3) or sodium hydroxide (NaOH) as geopolymerization agents with 1.4 and 1.6 g/L (solid/liquid) ratios of slags. Blast furnace slags (BFS) were added to each alkali-activated solution reaction, maintaining under constant stirring during periods of 4, 20, and 24 h. Posteriorly, hydrogen peroxide 50% was inserted as a foaming agent. This method used room temperature (25 °C) to the production of the foams. The influence of the mixture parameters on the resultant porosity was observed through the characterization by X-ray fluorescence (XRF), Fourier transformed infrared (FTIR), X-ray diffraction (XRD), thermogravimetry (TG/DTG) and scanning electron microscopy (FEG-SEM) analyses. Geopolymeric foams (GF) were obtained with different characteristics of porosity, thermal stability, crystallinity, and interconnection between porous. Dimensional stability was observed on the samples of geopolymer of blast furnace slags with metasilicate. According to characteristics of the developed samples, they can be investigated as CO2 and other gases absorber, or retainer of harmful metals.

Impact of chemical treatments on Leuconostoc bacteria from harvested stored cane/stale cane

Post-harvest sucrose losses are always a critical problem for sugar industries. A predominant factor which is causing these post-harvest losses that affects sugar recovery is the bacterium Leuconostoc spp. This study aims to check the efficacy of certain chemical treatments in reducing the proliferation of this bacterium. Our study based on a Leuconostoc-specific media revealed that application of 0.5 % aqueous solution of benzalkonium chloride and sodium metasilicate (BKC + SMS), formaldehyde, glutaraldehyde, sodium chloride and pine oil showed significant reduction in zone of proliferation. Considering formaldehyde and glutaraldehyde as control, the most effective treatments were chemical formulations of benzalkonium chloride along with sodium metasilicate, pine oil and sodium chloride in checking the proliferation of this bacterium. The application of these treatments has an immense potential in the sugar industry for reducing post-harvest sugar losses.

The effect of expanded graphite with sodium metasilicate as lubricant at high temperature

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.