Silicic Acid Gel Research Articles

Surface corrosion mechanism of ceramic proppant caused by formation water

AbstractThe performance of ceramic proppant tended to deteriorate during service, and one of the main reasons was the formation of water corrosion on the proppant surface. The proppant was isothermally soaked in formation water and the proppant immersed for different times was characterized by X‐ray fluorescence spectroscopy, X‐ray photoelectron spectroscopy, X‐ray diffraction, Fourier‐transform infrared spectroscopy, and scanning electron micrscopy. It is found that Cl− in the formation water can migrate to the proppant surface by diffusion and cause corrosion, which degrades its performance. Silica of the proppant can react with Cl− of formation water to form SiCl4, which will rapidly hydrolyze to produce opaque silica gel or silicic acid gel coating the proppant surface. With the extension of immersion time, the gel becomes thicker and more, promoting the degradation of the proppant. This will provide some theoretical guidance for alleviating the degradation of proppant.

Native selenium in the apical rocks of the Gaisky copper-pyrite deposit

Research subject. Selenium mineralization in altered rocks of the Gaisky deposit. Aim. Determination of formation conditions of native selenium in altered rocks. Results. Selenium mineralization is established in three zones of altered rocks in the sides of the 3rd quarry and is confined to the upper part of the sulfur-quartz rocks. Layers with a high content of native selenium and tiemannite are distinguished by a carbon-black color against the general background of yellow-green sulfur-quartz rocks, forming subvertical trickle textures. The maximum propagation of selenium mineralization was found in the southwestern zone of the quarry. Here, selenium-containing rocks are traced vertically by 6 m, forming a lens with a diameter of up to 70 cm. The accumulation of selenium occurs due to its physical properties. Selenium is similar to sulfur in volatility, although it undergoes more intense condensation under decreased temperatures. The accumulation of selenium condensate is facilitated by a silicic acid gel, which prevents the removal of selenium by a hydrothermal flow. Conclusion. The native selenium of the Gaisky deposit is characterized by a hydrothermal genesis, which, along with the presence of monoclinic native sulfur in the rocks, indicates the hydrothermal formation of the entire complex of altered rocks.

Wettability, adhesive performance and structural evolution of an environment-friendly modified silicate binder for foundry moulding and coremaking

For the manufacturing of sand cores, silicate inorganic binders have emerged as promising green casting binder materials; however, their adhesive performance requires further improvement. In this study, to evaluate the impact of using water-soluble polyols, i.e. polyethylene glycol (PEG) and xylitol, to modify silicate adhesives, the effect of the content and type of water-soluble polyol on the colloidal stability, wettability and adhesive performance of a silicate binder were investigated. The structural evolution of the modified silicate binder and the polysilicate bondswere studied using characterisation techniques including infrared spectroscopy and 29Si nuclear magnetic resonance (NMR) spectroscopy. Results revealed that PEG 400 and PEG 600 increased the size of polysilicate particles in the solution, resulting in flocculation of the silicate binders and easy precipitation or separation in a short period of time. However, PEG 200 and xylitol exerted little effect on the stability of the silicate solution. Moreover, 0.25 wt% PEG 200 reduced the surface tension of the solution from 78.93 to 54.15 mN/m and the equilibrium contact angle from 45.0° to 34.6°. The polyol promoted the dehydration and condensation of silicic acid gel to form a more stable three-dimensional network structure, improving the bonding strength of casting sand cores prepared using the silicate binder and silica sand from 2.42 to 3.02 MPa. This study not only unveils the role of PEG in improving the wettability and bonding behaviour but also provides an example of the rational use of environment-friendly water-soluble polyols to enhance the performance of green inorganic adhesive materials.

Study on semi-dynamic leaching and microstructure characteristics of MSWI fly ash solidified sediment

municipal solid waste incineration (MSWI) fly ash partially replaces cement to solidify sediment, and then can be used as intermediate cover materials in landfill as one of the resources utilization ways of MSWI fly ash and sediment. The strength and the semi-dynamic leaching characteristics of MSWI fly ash solidified sediment under hydrochloric acid attack at different pH were studied by means of unconfined compressive strength (UCS), semi-dynamic leaching, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and Thermogravimetric analysis (TGA). Results revealed that the UCS strength increased as the curing age and cement content increased. When the curing content is 50% and the replacement ratio of MSWI fly ash is 75% and 80%, the UCS of 7 d can be greater than 50 kPa. The primary contribution to the strength development was from silicic acid gels such as calcium silicate hydrate (C–S–H) and carbonates. Notably, the leaching behavior of Zn and Cu within the solidified sediment underwent substantial alterations. The leaching amount of heavy metals in a strong acidic environment (pH = 2) is significantly greater than that in a weak acidic (pH = 4) and neutral (pH = 7) environment. Conversely, minimal disparities were observed in the leaching characteristics of Zn and Cu between the weakly acidic and neutral environments. Ca(OH)2, C–S–H and carbonate exhibits a remarkable acid-resistant buffering capacity in the solidified sediment. The obvious diffusion coefficient (Dobs) was less than 10−9 m2/s in semi-dynamic leaching tests. Moreover, the mobility of Zn and Cu surpassing 12.5, coupled with a leaching index exceeding 8, further attests to the favorable S/S outcome achieved. Based on these findings, the solidified material is confidently recommended to be used as suitable landfill middle soil cover material.

Fire-Resistant Coatings, Obtained by Layer-by-Layer Assembly, in the System of Silicic Acid Gel – Diammonium Hydrogen Phosphate – Urea

The paper discusses the influence of flame retardant compositions obtained in the system of silicic acid sol (SiO2 sol) – flame retardants on the fire retardant properties of thin dense cotton fabrics and low density voluminous tapestry fabrics. The need to develop the optimal composition of a fire-retardant composition for a specific fabric, or to unify it for two main groups of fabric: thin and bulky low-density ones, is substantiated. Experimental coatings were obtained by applying SiO2 sol, which was obtained by the reaction between liquid glass and acetic acid, followed by application of flame retardant solutions (diammonium hydrogen phosphate (DAHP) and urea) by spraying or by the bath method. As a result of the optimization, using the central composite uniform rotatable plan of the second order, it was established that the main effect of the flame retardant is exerted by diammonium hydrogen phosphate (DAHP). The content or concentration of urea depends on the concentration of DAHP used: if diluted DAHP solutions (9–10 %) are used, trace amounts of urea (0–0.5 %) must be added. In the case of using a concentrated DAHP solution (18–20 %), the concentration of the urea solution should also be increased to 8–10 %.

Selection of precursors of safe silica-based fireproof coatings for textile materials

The selection of the inorganic precursor SiO2 as the main component of the simplified safe technology for obtaining flame-retardant coatings on textile materials was carried out. By thermo-graphic research of organic and inorganic SiO2 precursors, performed on an OD-102 deri-vatograph under conditions of heating at a rate of 10ºС/min in an air environment, the processes of decomposition of the coating that occur during the action of fire were investigated. Gels based on inorganic precursors produced by industry (silica sol, silica gel) and silicic acid, which was obtained by the exchange reaction of an aqueous solution of sodium silicate of liquid glass and acetic acid, were studied for the comparative characteristics of thermal destruction of coatings. As organic precursors of SiO2, gels of ethyl silicate-32 and methyltriethoxysilane were studied, which were obtained by hydrolysis of organosilicon compounds in an acidic water-alcohol medi-um with subsequent polycondensation of the hydrolysis products. The effect of temperature on the nature of thermal destruction of silica gel, silica sol, silicic acid and organosilicon gels of ethyl silicate and methylotriethoxysilane was investigated. It is shown that inorganic precursors differ favorably from organosilicon precursors in terms of the overall thermal effect during their de-composition, mass loss during heat treatment, and the rate of change of this parameter. Consider-ing that, in addition to total mass loss, the increase in mass loss during heating is less than 1 % in compositions based on inorganic precursors, it is possible to use all three types of inorganic pre-cursors, but from the point of view of acidity and safety of impregnation compositions, prefer-ence is given to silicic acid obtained by the exchange reaction of silicate sodium liquid glass with acetic acid.

Obtaining a Ferrosilicon Flocculant-Coagulant from Metallurgical Production Waste and Its Usage in Emulsified Wastewaters Purification Process

A method of obtaining a composite ferrosilicon flocculant-coagulant (FSFC) as a result of acidic modification of slaking steelmaking slag was suggested. It has been determined that the acidic modification of electric-furnace steelmaking slag results in the leaching of basic oxides with the formation of ferric sulfate and silicic acid gel. This allows using the obtained modification product as a ferrosilicon flocculant-coagulant in emulsified wastewaters purification systems. It has been demonstrated that the obtained powdery FSFC at the consumption rate 0.7 g/dm3 provides the emulsion purification efficiency – 99.3 %.

Investigation of silicic acid saturation and gel formation during ISG leaching: 180 days duration reaction at 90 °C

Currently, borosilicate glasses are utilised to immobilise highly radioactive waste. They are durable materials; however, they corrode in aqueous solutions, resulting in silica-rich alteration layers. This study employed the nuclear waste leaching tests (MCC-1, MCC-3) on International Simple Glass (ISG) samples. The corrosion rate in pure water and saturated water with respect to ISG corrosion products was investigated at an initial pH of 6.3 and a reaction temperature of 90 °C. For 3, 7, 14, 28, 90, and 180 days, batch experimental models with extremely high and very low glass surface area to volume (S/V) ratios were examined. The results showed that early saturation in the higher S/V system resulted in a ten order magnitude reduced corrosion rate compared to the lower S/V system. This emphasises the significance of saturation in achieving a reduced corrosion rate. This research proved the significant influence of the solution’s chemistry on the glass corrosion rate via pH and other chemical parameters.

Green synthesis and characterization of zeolite silicalite-1 from recycled mother liquor

Researches on zeolite silicalite-1 have focused mainly on improving its performance, with little attention paid on green and economic synthesis. Herein, a novel route for green synthesis of pure silicalite-1 from the recycled mother liquor has been developed. This route starts from the hydrothermal reaction of natural quartz with NaOH to form a sodium silicate solution, which is then transformed into a silicic acid (H2SiO3) gel by hydrochloric acid titration. Then the solid silicic acid (H2SiO3) gel and fumed silica (SiO2) are mixed with water under stirring to form a highly active slurry, which can be hydrothermally “dissolved” in a dilute NaOH aqueous solution. Using this slurry with a high SiO2/Na2O molar ratio of 5 : 1 as the silica source as well as tetrapropylammonium bromide (TPABr) as the organic template, MFI-type pure silicalite-1 has been successfully synthesized. After each synthesis, the mother liquor of centrifuged supernatant was recovered and recycled. The silica source and organic template were added to the recycled mother liquors for the synthesis of pure silicalite-1. The minimum TPABr/SiO2 molar ratio needed to synthesize pure silicalite-1 in the initial run is 0.04 : 1. In comparison, only half the amount of the organic template is needed in subsequent runs with the recovered mother liquors. Through recycling, all reactants in the mother liquors were ultimately utilized without any waste, leading to not only effectively reducing the cost of silicalite-1 synthesis but also minimizing its environmental impact.

A high strength triboelectric nanogenerator based on rigid-flexible coupling design for energy storage system

Recently, efficient green energy conversion and storage systems attracts attention due to global environmental pollution and the depletion of fossil fuels. Here, we firstly proposed a novel triboelectric nanogenerator based on the rigid-flexible coupling design (RF-TENG) using the acrylate structure glue (ASG) and the silicic acid gel (SAG) as triboelectric materials. The fully packed ASG layer and SAG layer can be easily prepared by coating ASG/SAG on the Ni foam surface, and Ni foam plays the role of conductive electrode. Remarkably, the reasonable collocation of a rigid ASG layer and soft SAG layer can bring full and effective contact during the triboelectricity process for enhancing the output performance. Moreover, the RF-TENG can work in adverse environment. The corresponding electrical properties, such as the peak value short-circuit current (Isc), open-circuit voltage (Voc), and output power density can achieve 42 μA, 345 V, and 143 μW/cm2, respectively, and 122 commercial light-emitting diodes (LEDs) can be easily lighted up by the RF-TENG. Except for that, an effective strategy for energy conversion and storage was designed, and through the proposed power management circuit (PMC), the charging efficiency of MnSe-Supercapacitor (MnSe-SC) has been significantly improved. Due to the high performance of energy conversion and storage, this research is considered promising for promoting the practical application of green energy.

Oil Removal Technology and the Mechanism of Oily Cuttings by Silicic Acid Micromicelles

A large amount of oily cuttings is produced in the drilling process when the oil-based drilling fluid is used. The oil and oil-soluble additives adsorbed on the surface of the cuttings may pollute the environment. In this paper the method of silicic acid precipitation and formation of silicic acid micromicelles is used to encapsulate oil and to remove oil from the cuttings. The authors analyze the influence of the stirring time and the solution pH on the oil removal efficiency. When the pH is 2 and the stirring time is 10 min, the oil removal rate is 96%. Research into the mechanism shows the successive formation of silicic acid sol and gel in the process of silicic acid precipitation. The structure of the silicic acid micromicelles is characterized by scanning electron microscopy (SEA). The results of differential scanning calorimetry (DSC) indicate the existence of the exothermic decomposition peak of the hydrocarbons in the range from 350°C to 500°C, which proves that the micromicelle inner phase contains oil.

Laws of the Formation and Diffusion Properties of Silica and Agarose Gels

The physicochemical and mass-transfer properties were studied for two gels that can be applied in the fabrication of bioreactors using additive manufacturing. The fundamental difference between these gels lies in the mechanisms of their formation from solutions. The first one is a silicic acid gel, which is formed in a chemical reaction and has an irreversible gelling process. The second one is an agarose gel, which is formed from a water solution of agarose upon cooling and turns back into liquid when heated. Studies were performed by optical methods that include the spectroscopy of gel samples during their formation and the visualization of the diffusion fronts of transferred substances. Being nonintrusive, these methods have no effect on the state of samples and do not distort the dynamics of processes. Characteristic patterns of changes in the spectral parameters during gelling were studied for both gels depending on the dispersed phase concentration, which was relevant to the practical application of the gels. New experimental data were obtained on the structure of the gels and the mechanisms of its change during gel aging. The main laws are determined for changes in the diffusion coefficients in the gels with increasing concentration of the dispersed phase.

Corrosion mechanism of E-glass of chemical resistance glass fiber in acid environment

The corrosion of ECR glass fiber was investigated by the analysis methods of weight loss ratio under different acids and at various durations. Weight loss, leaching of cations, and surface composition of ECR glass fiber were analyzed. The corrosion mechanism of ECR glass fiber in acid environment was also discussed. The experimental results showed that the corrosion degree of ECR glass fiber in different acids obeyed the order: HNO3>H2SO4>HCl. The acid effects on corrosion of ECR glass fiberis were totally different. Hydrochloric acid mainly destroyed the network structure of [AlO4], while sulfuric acid and nitric acid mainly destroyed the structure of [SiO4]. The acid resistance of ECR glass fiber is much better than that of E glass fiber due to the generation of intermediate product silicic acid gel Si(OH)4 during ion exchange. It can adhere to the glass surface to form a thin film and hinder the proceeding of corrosion.

Evaluation of the Significance of the Factors Influencing the Microstructure of Silicic Acid Gels

It is shown that modern high-porosity insulation material can be obtained on the basis of silicon dioxide. The most significant parameters influencing the formation of a porous structure of gels obtained from alkoxides by the sol–gel method are determined by means of factor analysis.

Improvement of wheat (Triticum aestivum) drought tolerance by seed priming with silicon

Silicon has the potential to improve drought tolerance in crops. Seeds primed with silicon were used in the present study to explore its potential benefit to withstand water stress. Seeds of two wheat varieties, NARC-2009 and Chakwal-50, were sown in pots after priming with distilled water and different concentrations (0.5%, 1.0% and 1.5%) of silicon sources (silicic acid, sodium silicate and silica gel) at PMAS, Arid Agriculture University, Rawalpindi. Maximum silicon uptake at three-leaf stage (0.028 µg g−1 dry weight (DW)), anthesis (0.072 µg g−1 DW) and maturity (0.103 µg g−1 DW) was recorded for silica gel. Silicon uptake increased significantly in response to increase in Si concentration from 0.5% to 1.5%. Leaf membrane stability index, epicuticular wax, relative water content and proline remained maximum – 78.90%, 2.6 mg g−1 DW, 83.88% and 54.90 µg g−1 – for silica gel treatments compared with others. Silica gel with 1.5% silicon concentration resulted in maximum spike length (14.3 cm), biological yield (7.63 g pot−1), hundred-grain weight (3.97 g pot−1) and grain yield (2.46 g pot−1). Based on the study outcomes, it is concluded that silica gel might be a good priming option with 1.5% silicon concentration to establish plant under drought stress.

Оцінка якості реставрацій постійних зубів у дітей, які проживають у місцевості, забрудненій солями важких металів

The influence of the environment on the child health is one of priority issues of the present time and it is of great social importance. Increased dental diseases associated with climatic and geographical characteristics of the area are widely discussed in the literature. The leading among them are environmentally determined dental diseases in children associated with geochemical and technogenic pollution of the area where they live. Increasing amounts of hard metal salts is the urgent hygienic problem, due to severity of their multi-element analysis in microsubjects, and negative influence on health of the children population, due to tropism, ability to cumulation, long biological life in the body and antagonism of heavy metal salts to the number of microelements. Influence of hard metal salts on dental diseases development is undeniable. Particular attention is paid to their influence on caries process and treatment peculiarities. Despite the fact that modern аdhesive dentistry in recent years has made a significant breakthrough in improving adhesive systems, correct choice of adhesive system depending on changes in the structure of hard tissue under geochemical contaminants (like heavy metal salts) is the most important step. It is the decisive factor for adaptation and connection of restoration with the restoration base. We should remember that on the way of adhesive system there is an altered structure preventing from deep penetration of such system and, consequently, leading to violation of restoration tightness. Therefore, early detection of complications by clinical evaluation of quality of the restorations is of great interest. Multi-vector approach to treatment of dental caries in children living in conditions of technogenic pollution by heavy metal salts is extremely urgent and important issue. Significant niche in this approach is given to adhesive preparation methods combined with local fluoridation, using fluoride medication of the new generation. One of them is Hluftored which promotes the formation of microcrystalline СаF2. Protocol of work with this new generation drug is based on the sequential precoating of enamel with magnesium-fluoride silicate, and then with suspension of high desperasible calcium hydroxide promoting formation of microcrystalline СаF2, magnesium and copper with the size of ~50Аº, leading to easy penetration of fluoride into pores of softening range. Moreover, microcrystals of CaF2 are protected by silicic acid gel from outwashing. Therefore, they release fluoride for a long period of time (over 1 year), which promotes remineralization and prevents complications of dental caries. This article includes the data regarding effectiveness of the Hluftored use in combination with various adhesive systems. Also, we show data of clinical quality assessment conducted for restoration procedures in children of different age groups and territories by using index of USPHS, after 6 and 18 months of carrying out such procedures. Clinical observations indicate the effectiveness of deep fluoridation and different adhesive systems in the complex of caries treatment in different age groups at present time and in future.

PREPARATION AND CHARACTERIZATION OF SOLID DISPERSION OF ITRACONAZOLE

The aim of the present study was to improve the dissolution rate and oral bioavailability of a poorly water soluble drug, itraconozole (ITR) by its adsorption on a porous calcium silicate (FLR). The drug w as adsorbed on FLR by adsorption method . solid dispersion of various composition were prepared using Porous Calcium Silicate (FLR), Silicic Acid, Colloidal Silica and Silica Gel (Neutral) (2:1, 1:1, 1:2, 1:3, Physical mixture) . C rystallinity of the drug in the solid dispersion was evaluated by differentia l scanning calorimetry and powder X - ray diffraction analysis. Itraconazole was released at a much higher rate from solid dispersion and physical mixture as compared to that as of it r aconazole faster dissolution was exhibited by solid dispersion containing 1:2 ratios of drug and polymer compared to physical mixture and itraconazole . The increase in dissolution rate of the drug may be due to decrease in crystalinity.

물유리와 이산화탄소로 가압함침한 가문비 나무의 연소특성

After produce the extracted wood to silicic acid gel, sodium carbonate and silicon dioxide with application of the making method for carbon dioxide, ignition time, ignition temperature, mass loss rate and critical heat flux are measured according to external radiation source (20, 25, 35 and 50 kW/m 2 ). From the results, pressure impregnation wood to use with water glass and carbon dioxide has fire retardant performance at heat flux (less than 20 kW/m 2 ) of Pre-Flashover fires. If we find out the excellent maxing ratio through continuously study, it might be decided to be able to be utilized as fire-retardant wood.

Modification of HCBS at the nanodispersion level

The possibility of modifying HCBS by artificial introduction of an optimum amount of nanoparticles in the form of silicic acid gel is studied. It is shown that a modifying addition promotes improvement of rheotechnological properties of suspensions, and an increase in the physicomechanical properties of castings based on them.

Research on a novel composite gel system for CO2 breakthrough

A composite gel was prepared for plugging CO2 channeling, which is a serious problem for enhanced oil recovery with CO2. A composite gel which is one of the materials for successful control of CO2 channeling during CO2 injection process was studied in this paper. SEM and nano particle size analysis were used to describe this material’s microstructure. Its effect on CO2 channeling control was evaluated with core flow experiments. Both the rheological test and core plugging experiments indicated that both acrylamide monomer concentration and reaction pressure had positive influences on gel properties. The gel system with an acrylamide monomer concentration of 2% and 5% sodium silicate was proved to have excellent strength, elastic and plugging efficiency, which confirmed huge development potential and wide application of the composite gel system. The high-pressure acid environment arising from the CO2 injection not only reacts with solid silicate to form silicic acid gel, but also facilitates efficient polymerization.