scholarly journals Alkali Activation of Silicate Mine-Tailings: Response to Different Activator Sources

Proceedings ◽  
2019 ◽  
Vol 34 (1) ◽  
pp. 10
Author(s):  
Perumal ◽  
Illikainen
Keyword(s):  
Sodium Silicate ◽  
Sodium Carbonate ◽  
Mine Tailings ◽  
Construction Materials ◽  
Mining Industry ◽  
Sodium Silicate Solution ◽  
Sodium Sulphate ◽  
High Alumina ◽  
Alkali Activation ◽  
Early Age

To attain sustainability in construction industries, it is important to explore industrial side-streams as a potential replacement for traditional construction materials. This will avoid the depletion of natural resources and helps in preserving the environment. In this way, mining industry attracts the attention of scientific community for the huge volume of tailings generated along with the problem of disposal. This paper mainly focuses on silicate tailings (MT) from two different mining sources with high magnesium (HM) and high alumina (HA) content. To study the possibility of using these tailings as precursors in alkali activation, different activators such as, sodium silicate (Na2SiO3), sodium sulphate (Na2SO4) and sodium carbonate (Na2CO3) were employed. It was noted that the mine tailings took longer time to set in case of activators other than sodium silicate. The milled tailings were co-grinded with the respective solid activators (10%) and mixed with 30% of sodium silicate solution (accelerates setting), to make cylindrical paste specimens. The specimens were cured at 60 °C for 24 h. The results shown that tailings rich in magnesium (MT-HM) activated with sodium carbonate gives high early age strength i.e., 60% increase in average strength compared to other activators. Whereas, sodium silicate helped in achieving 10% increase in early age strength of high alumina tailings (MT-HA). However, this was not the case for the later ages. At 7th day of testing, sodium silicate activated MT-HM shown a strength improvement from 2 MPa to 6 MPa with the formation of magnesium silicate hydrate and hydrotalcite. MT-HA activated with sodium sulphate resulted in a maximum strength of 8.5 MPa due to the ettringite and zeolite in the system. Sodium carbonate does not show comparable results at 7th day of testing though it shown improvement in strength with age. It is also important to consider that there are other oxides like calcium and iron present in these tailings which could also have impacted the results.

scholarly journals Potential of Mechanochemically Activated Sulfidic Mining Waste Rock for Alkali Activation

2021 ◽  
Author(s):  
He Niu ◽  
Lugas Raka Adrianto ◽  
Alexandra Gomez Escobar ◽  
Vladimir Zhukov ◽  
Priyadharshini Perumal ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Chemical Reactivity ◽  
Construction Materials ◽  
Mining Industry ◽  
Mining Waste ◽  
Waste Rock ◽  
Alkali Activation ◽  
Curing Conditions ◽  
Grinding Mechanism ◽  
Diffuse Reflectance Infrared

Abstract Sulfidic mining waste rock is a side stream from the mining industry with a potential environmental burden. Alkali activation is a promising method for transforming mining waste into construction materials. However, the low reactivity of minerals can be a sizeable challenge in alkali activation. In the present study, the reactivity of waste rock was enhanced by mechanochemical treatment with a LiCl-containing grinding aid. X-ray diffraction (XRD) and diffuse reflectance infrared Fourier transform (DRIFT) analysis were utilized to display the structural alteration of individual minerals. A schematic implication of the grinding mechanism of mica was provided according to the results of transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The alkaline solubility displayed the enhanced chemical reactivity of the waste rock, in which Si and Al solubility increased by roughly 10 times and 40 times, respectively. The amorphization of aluminosilicate is achieved through chemical assisted mechanochemical activation. Sulfidic waste rock, as the sole precursor in alkali activation, achieved a 28-day compressive strength exceeding 10 MPa under ambient curing conditions. The simulation of the upscaled grinding process was conducted via the HSC Chemistry® software with a life-cycle assessment. The results showed that mining waste rock can be a promising candidate for geopolymer production with a lower carbon footprint, compared to traditional Portland cement. Graphical Abstract

Use of Mine Tailings as Precast Construction Materials through Alkali Activation

2019 ◽  
Vol 37 (1) ◽  
pp. 251-265 ◽  
Author(s):  
Bo Huang ◽  
Qingming Feng ◽  
Dongbo An ◽  
Jinhong Zhang
Keyword(s):  
Mine Tailings ◽  
Construction Materials ◽  
Alkali Activation ◽  
Precast Construction

scholarly journals Geopolymer Synthesis Using Garnet Tailings from Molybdenum Mines

Minerals ◽  
2019 ◽  
Vol 9 (1) ◽  
pp. 48 ◽  
Author(s):  
An Wang ◽  
Hongzhao Liu ◽  
Xiaofei Hao ◽  
Yang Wang ◽  
Xueqin Liu ◽  
...  
Keyword(s):  
Sodium Silicate ◽  
Mine Tailings ◽  
Industrial Waste ◽  
Room Temperature ◽  
Environmental Issues ◽  
Curing Temperature ◽  
Alkali Activation ◽  
X Ray Diffraction ◽  
X Ray ◽  
Scanning Electron

Garnet tailings obtained in large quantities from molybdenum ore beneficiation are regarded as industrial waste, which not only occupies large areas of land but also causes environmental issues and ecological fines. Preparing garnet tailings based geopolymers (GTGs) is one of the efficient methods to recycle and utilize garnet mine tailings. In this work, geopolymers were synthesized using garnet tailing (GT) and metakaolin (MK) as the main precursors and sodium silicate as the alkali-activation agent. The effect of MK and alkali activator dosage, as well as curing temperature on the compression strength of GTGs were analyzed in detail. Results showed that the maximum strength (46 MPa, 3 days) was reached at a 20 wt % MK dosage with 35% sodium silicate addition cured at room temperature. The microstructure and phase composition of GTGs were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier-transform infrared spectroscopy (FTIR), which confirmed the formation of an amorphous geopolymer gel. Lastly, it can be concluded that the garnet tailing is a promising material for geopolymer production, as an alternative for its utilization.

Sodium salt scaling in black liquor evaporators and the effects of the addition of tall oil brine

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Erik Karlsson ◽  
Anders Åkesjö
Keyword(s):  
Sodium Carbonate ◽  
Sodium Salt ◽  
Black Liquor ◽  
Sodium Sulphate ◽  
Salt Solutions ◽  
Tall Oil ◽  
Sulphate Content ◽  
Inhibition Effect ◽  
Salt Scaling ◽  
Primary Nucleation

AbstractSodium salt scaling, i. e. the formation of doubles salts comprised of sodium, carbonate and sulphate on the heat transfer surfaces, is a common problem that occurs during black liquor evaporation. In this study, experimental results are presented that provide new insights into the formation and composition of such scales and how they are influenced by the addition of tall oil brine. It was found that increased content of sodium carbonate and sodium sulphate in the black liquor increased scaling, while the ratio between carbonate and sulphate had a lesser influence than reported in other studies. Black liquor created loose clay-like scales comprised of aggregated crystals and black liquor, whereas salt solutions created hard mineral-like scales. The scales formed by both the black liquor and the salt solution showed a tendency to fall off during formation after primary nucleation. It was also found that both tall oil soap and alkalized tall oil brine could inhibit the formation of scales. The inhibition effect is stronger if adding the soap or brine just before scaling starts, but also depends on the amount added, the sodium carbonate and sodium sulphate content in the liquor as well as other factors.

scholarly journals Printability and Setting Time of CSA Cement with Na2SiO3 and Gypsum for Binder Jetting 3D Printing

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 2811
Author(s):  
Okpin Na ◽  
Kangmin Kim ◽  
Hyunjoo Lee ◽  
Hyunseung Lee
Keyword(s):  
3D Printing ◽  
Sodium Silicate ◽  
Setting Time ◽  
Sodium Silicate Solution ◽  
Preliminary Test ◽  
Silicate Solution ◽  
Calcium Sulfoaluminate Cement ◽  
Calcium Sulfoaluminate ◽  
Parametric Studies ◽  
Binder Jetting

The purpose of this study is to optimize the composition of CSA (calcium sulfoaluminate) cement with sodium silicate (Na2SiO3) and gypsum for binder jetting 3D printing. The preliminary test was carried out with an applicator to decide the proper thickness of one layer before using the 3D printer. A liquid binder was then selected to maintain the shape of the particles. Based on the results, the optimal mixture of dry materials and a liquid activator was derived through various parametric studies. For dry materials, the optimum composition of CSA cement, gypsum, and sand was suggested, and the liquid activator made with sodium silicate solution and VMA (viscosity modified agent) were selected. The setting time with gypsum and sodium silicate was controlled within 30 s. In case of the delayed setting time and the rapid setting mixture, the jetting line was printed thicker or thinner and the accuracy of the printout was degraded. In order to adjust the viscosity of the liquid activator, 10% of the VMA was used in 35% of sodium silicate solution and the viscosity of 200–400 cP was suitable to be sprayed from the nozzle. With this optimal mixture, a prototype of atypical decorative wall was printed, and the compressive strength was measured at about 7 MPa.

scholarly journals Silica extraction from bauxite reaction residue and synthesis water glass

2021 ◽  
Vol 10 (1) ◽  
pp. 268-283
Author(s):  
Yunlong Zhao ◽  
Yajie Zheng ◽  
Hanbing He ◽  
Zhaoming Sun ◽  
An Li
Keyword(s):  
Sodium Silicate ◽  
Water Glass ◽  
Sodium Silicate Solution ◽  
Silicate Solution ◽  
Hydrated Calcium Silicate ◽  
Precipitated Silica ◽  
Alumina Gel ◽  
Silica Alumina ◽  
Element Removal ◽  
Hydrated Calcium

Abstract Bauxite reaction residue (BRR) produced from the poly-aluminum chloride (PAC) coagulant industry is a solid acidic waste that is harmful to environment. A low temperature synthesis route to convert the waste into water glass was reported. Silica dissolution process was systematically studied, including the thermodynamic analysis and the influence of calcium and aluminum on the leaching of amorphous silica. Simulation studies have shown that calcium and aluminum combine with silicon to form hydrated calcium silicate, silica–alumina gel, and zeolite, respectively, thereby hindering the leaching of silica. Maximizing the removal of calcium, aluminum, and chlorine can effectively improve the leaching of silicon in the subsequent process, and corresponding element removal rates are 42.81%, 44.15%, and 96.94%, respectively. The removed material is not randomly discarded and is reused to prepare PAC. The silica extraction rate reached 81.45% under optimal conditions (NaOH; 3 mol L−1, L S−1; 5/1, 75°C, 2 h), and sodium silicate modulus (nSiO2:nNa2O) is 1.11. The results indicated that a large amount of silica was existed in amorphous form. Precipitated silica was obtained by acidifying sodium silicate solution at optimal pH 7.0. Moreover, sodium silicate (1.11) further synthesizes sodium silicate (modulus 3.27) by adding precipitated silica at 75°C.

A Study on a Green Route to Preparation of Silica Powders with Rice Husk Ash

2014 ◽  
Vol 1010-1012 ◽  
pp. 1015-1019
Author(s):  
Ze Xin Yang ◽  
Lin Dong ◽  
Meng Wang ◽  
Huan Li
Keyword(s):  
Sodium Bicarbonate ◽  
Sodium Silicate ◽  
Rice Husk ◽  
Rice Husk Ash ◽  
Sodium Hydroxide Solution ◽  
Sodium Silicate Solution ◽  
Silicate Solution ◽  
Raw Material ◽  
Transmission Electron ◽  
Thermal Analyzer

The main purpose of this article is to develop an environmentally friendly and economically effective process to produce silica from rice husk ash. Sodium silicate solution was prepared by the reaction of rice husk ash and sodium hydroxide solution, and then the sodium silicate solution was used as the raw material for the preparation of silica with sodium bicarbonate. During the reaction, the by-product can be passed into CO2 to prepare sodium bicarbonate what can be reutilized. Experimental route achieved resource recycling and environment-friendly, low energy consumption, zero emissions and so on. Meanwhile the microstructures of the silica powders were characterized by Transmission electron microscope (TEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR) and Thermo gravimetric/Differential thermal analyzer (TG-DTA).The purity of silicon was up to 99.43% and the particle size was 200-300nm.

How Efficient are LC3 and GGBFS-Contained Mortar Mixtures Submerged into Na2SO4 Solution against External Sulfate Attack at an early Age?

2021 ◽  
Vol 902 ◽  
pp. 145-151
Author(s):  
Islam Orynbassarov ◽  
Chang Seon Shon ◽  
Jong Ryeol Kim ◽  
Umut Bektimirova ◽  
Aidyn Tugelbayev
Keyword(s):  
Synergistic Effect ◽  
Construction Materials ◽  
Sulfate Attack ◽  
Early Age ◽  
Weight Changes ◽  
Calcined Clay ◽  
Initial Strength ◽  
Sulfate Resistance ◽  
Dense Microstructure ◽  
Pozzolanic Materials

Ordinary Portland cement (OPC) is one of the most widely used construction materials in civil engineering infrastructure construction but it is susceptible to sulfate attack. One of the ways to improve the sulfate resistance of an OPC mortar/concrete is to replace a certain amount of OPC with different pozzolanic materials such as ground granulated blast furnace slag (GGBFS) and metakaolin. The use of pozzolanic materials to mortar/concrete not only enhances durability but also reduces carbon dioxide (CO2) emission due to the less usage of OPC at the initial construction state. As considering these aspects, limestone calcined clay cement (LC3) has been developed in recent decades. However, the influence of LC3 on sulfate attack resistance has not been fully evaluated. Therefore, this study investigated the efficiency of LC3 mortar mixtures against sulfate attack at an early age (approximately 4.5 months) after two different curing periods, namely 1-day and 3-day curing, since the strength of the LC3 mixture is lower than OPC mixtures. To evaluate the synergistic effect of a combination of LC3 and GGBFS on the sulfate resistance, the LC3 and OPC mixtures containing 25% GGBFS were also assessed in terms of density, porosity, compressive strength, volumetric expansion, and weight changes. The experiment results show that the expansion of the LC3 mixture regardless of the addition of GGBFS and an initial curing strength made a plateau after a rapid increase up to 7 days, while the expansion of the OPC mixture kept increasing throughout the period. Furthermore, the addition of GGBFS to OPC or LC3 mixture provides the synergistic effect on reducing the expansion due to sulfate attack. Therefore, if LC3 mixture has high initial strength (min. 15 MPa) and dense microstructure to minimize the penetration of sulfate ion into the mixture, it is expected that LC3 mixture is more efficient than OPC mixture against the sulfate attack.

scholarly journals Fayalite Slag as Binder and Aggregate in Alkali-Activated Materials—Interfacial Transition Zone Study

Proceedings ◽  
2019 ◽  
Vol 34 (1) ◽  
pp. 1 ◽  
Author(s):  
Adediran ◽  
Yliniemi ◽  
Illikainen
Keyword(s):  
Transition Zone ◽  
Sodium Hydroxide Solution ◽  
Coal Fly Ash ◽  
Construction Materials ◽  
Fine Powder ◽  
Silicate Solution ◽  
Interfacial Transition Zone ◽  
Alkali Activation ◽  
Fayalite Slag ◽  
Alkali Activated

Alkali-activated materials (AAMs) are an environmentally friendly option for Portland cement mortars and concretes. Many industrial residues such as blast furnace slag and coal fly ash have been extensively studied and applied as AAM precursors but much less focus has been on the use of fayalite slags. Water-cooled fayalite slag comes in granular form, which is then milled into fine powder (d50 ~10 microns) prior to its alkali activation. In addition, the un-milled granular fayalite slag can be used as an aggregate to replace sand in mortar. The alkaline solution utilized for the study was a mix of 10 M sodium hydroxide solution and commercial potassium silicate solution. A liquid to solid ratio of 0.15 was held constant for all the mixes. The particle size distributions of the binder and the aggregates were optimized, and the microstructure and chemical composition of the interfacial transition zone (ITZ) was studied using scanning electron microscope coupled with energy dispersive X-ray spectroscopy. ITZ is a region that exists between the aggregate and the binder and this can influence the mechanical and transport properties of the construction materials. The results showed that the mechanical properties of mortar having fayalite slag as aggregate and binder was significantly higher than one with standard sand as aggregate. No distinct ITZ was found in the samples with fayalite slag as aggregate. The outer rim of the fayalite slag aggregate participated in the hardening reaction and this significantly contributed to the bonding and microstructural properties of the mortar samples. In contrast, an ITZ was observed in mortar samples with standard sand aggregates, which contributed to its lower strength.

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