Synthesis Of Calcium Silicate Research Articles

Adsorption of malachite green dye over synthesized calcium silicate nanopowders from waste materials

The synthesis of calcium silicate (CS) nanopowders from marble sawing dust and silica fume using microwave irradiation (MWI)-assisted route has been studied. Coalesced tiny cubes and rods with flower-like shapes in the range of ∼ 150 nm in size with a surface area of 18.357 m2g−1 have been obtained as observed from FE-SEM images and detected by BET measurements, respectively. According to the Langmuir isotherms, increasing the temperature from 30 to 45 °C increases the maximum monolayer adsorption capacity, qmax, from 13.44 to 59.95 mg/g. The kinetic studies indicated that the adsorption kinetics of malachite green dye (MG) over calcium silicate nanopowders followed the pseudo-first-order with a high correlation coefficient (R2) of 0.7901. The experimental results also showed that the MG dye adsorption fitted better with the Freundlich model with a high correlation coefficient (R2 = 0.9474) which suggested the multilayer physisorption process. The calculated thermodynamics parameters (ΔG° = 0.019 to − 2.898 kJ mol−1, ΔS° = 109.83 J mol−1 and ΔH = 32.79 kJ mol−1) declared the adsorption feasibility, with degrees of randomness. In our study, adsorption measurements, schemes, and mechanism have been discussed to shed light on the advances in this field. The MWI route using waste raw materials will significantly lower overhead costs of adsorbent synthesis and will allow development in wastewater treatment.

Morphology-controlled calcium silicate and natural polymer composite materials: synthesis, structure and mechanical properties

ABSTRACT Calcium silicate (CS) composite materials are widely applied in cementitious materials and bone tissue engineering. Extensive studies focused on the traditional organic templates (e.g., surfactant), however, introducing the natural polymers to participate in the synthesis of CS has rarely been studied. In this paper, two kinds of modified natural polymers, i.e., gelatinized sticky rice starch (G-SRS), carboxymethyl chitosan (CMC), were used to participate in the synthesis of CS as a novel green organic templating. The morphology, physicochemical properties of CS composites were investigated by TEM-EDS, FE-SEM, FT-IR, BET, and the mechanical properties of CS compacted pellets were determined by the compressive strength and nanoindentation test. The results show that the particle size, particle shape and pore size of the natural polymer/CS composite were effectively controlled, compared to CS. Specifically, SRS/CS composite exhibited universal spherical CS particle morphology, and the CMC/CS composite exhibited finer particle morphology. Addition of natural polymer increased the compressive strength of CS composite, and 3%SRS/CS with uniform spherical particles structure showed ~62% and ~185% increase in the indentation hardness and elastic modulus, compared to the control CS sample. After the nanoindentation test, the polymer bonding was found in the crack structure of 3%SRS/CS, implying that the SRS/CS composite has the self-healing ability. This work reported the innovative synthesis process, green templating design and techniques, paving the path for designing the bioinspired natural polymer/CS composite structural materials.

Synthesis of calcium silicate as paper filler with desirable particle size from desilication solution of silicon-containing waste residues

Resource utilization of silicon is crucial to the sustainable reuse of the silicon-containing waste residues. In this study, a simple method to synthesize calcium silicate as paper filler with desirable particle size from the residues was proposed. Foil-shaped calcium silicate with the average particle size (APS) of about 10 μm and the span of below 1.2 was successfully synthesized. Compared with larger calcium silicate, the obtained product used as paper filler could greatly improve the bulk of paper while maintaining similar tensile strength. The online focused beam reflectance measurement (FBRM) was used to investigate the hydration of CaO and the formation of calcium silicate. It was found that the hydration of CaO in NaOH solution with the presence of silicate played a key role in synthesizing the 10 μm-sized calcium silicate. The formation of calcium silicate was speculated to be controlled by a liquid-liquid reaction.

Composition and properties of Kazakhstani diatomaceous minerals and synthesis on their base calcium silicates for building production

The review covers existing modern technologies and researches on applying diatomaceous minerals as silicate additives to building materials. Specialists of industrially developed countries actively work in this direction and there are some of the works on the stage of implementation now. The article also describes researches of the authors on synthesis of calcium silicate and hydrated forms of ferro-calcium silicates using different kinds of Kazakhstani diatomaceous minerals from Zhalpak deposit (Aktobe region) as main siliceous component. Main topological and physical-and-mechanical characteristics of natural diatomaceous minerals were studied. It was found out that using thermally activated diatomite mixed with a plasticizing agent enlarges strength under compression and raises the brand of building materials while lowering water absorption and specific weight. It was observed that use of thermally activated highly ferriferous diatomite (20-30 % of Fe2O3) increases the strength of building materials dramatically. X-ray phase analysis of the samples of cubes from obtained composites exposed to semi-dry pressing with thermally activated ferrous diatomite followed by steam tempering showed that there were Ca(Fe, Mg)Si2 and FeAl2SiO5(OH)2 in their composition in the amount up to 1 mas. %.The technical characteristics of cubes of composition obtained with the use of thermally activated diatomite, in particular its highly ferriferrous forms, are completely meet requirements of inter-state standards GOST 379–95 to siliceous stones and bricks and sometimes overcome this norms. In future, the technology for obtaining the synthesized materials can become a base to organize new and to improve the existing industries producing dry building mixtures and strong silicate bricks in Kazakhstan.

Synthesis of zeolite membranes on calcium silicate support and their bioactive response

The synthesis of calcium silicate supported zeolite membrane was carried out by second growth method. The chemical nature of the functionalizing agent on the formation of homogenous zeolite membrane was evaluated. One monomer and two cationic polymers were used: 3-aminopropyltriethoxysilane (APS), polyethylenimine (PEI) and polydiallyldimethylammonium chloride (PDDA). The support was subjected to chemical functionalization and then it was rubbed with zeolite crystals. The W zeolite was used as zeolite seed in two different Si/Al ratios. The functionalized and rubbed supports were submitted to hydrothermal treatment at 150 °C for 48 h. The bioactivity of the homogeneous zeolite membranes was evaluated by the biomimetic method through the membranes soaking in a simulated body fluid (SBF) at 37 °C for 21 days. Two immersion methods were evaluated. The products were characterized by XRD and SEM techniques. The results indicated that the supported functionalization with PDDA and the Si/Al ratio (higher than 1.8) of zeolite enhanced the interaction between the support and the zeolite precursor enhancing the formation of homogeneous zeolite membrane on the surface. The presence of the functional groups of PDDA on the membrane was detected by FTIR. After immersion in SBF, the zeolite membrane was stable and led to the formation of Ca–P layer on its surface. The re-immersion method led to the formation of richer Ca/P layer (1.36). These findings allowed generating a zeolite membrane with combined properties of calcium silicate and the controllable porosity of zeolitic material making it potentially useful for bone regeneration and drug releasing.

Synthesis of calcium silicate from selective thermal transformation of waste glass and waste shell

This study details a new pathway for successfully synthesising calcium silicate compounds using 100% waste inputs and processing temperatures significantly lower than conventional approaches. Using a solid-state reaction of two common wastes – powdered float glass from building demolition and sea shells discarded by the food industry, wollastonite (β-CaSiO3) and pseudo-wollastonite (α-CaSiO3) were obtained at 1100 °C and 1200 °C respectively. By comparison, a minimum processing temperature of 1436 °C has previously been required to achieve the same result. For both products, the optimum ratio of powdered glass to CaO derived from the mixed sea shell waste was 75:25. SEM analysis showed the wollastonite produced was dense with small sized porosity. By increasing the temperature to 1200 °C, smoother surface of pseudo-wollastonite was achieved with an acicular crystal structure observed at the fracture surface. Interactions between glass and CaO powder at 1000 °C, 1100 °C and 1200 °C were also studied using confocal microscopy. This revealed that the solubility and viscosity of the glass plays key roles in the production of the calcium silicate compounds. The hardness, flexural and compressive strength of the products increased in line with increases in temperature from 1100 to 1200 °C, with maximum values of 198.6 N/mm2, 30.1 and 110 MPa achieved, respectively. By measuring the mechanical properties of the calcium silicate compounds produced, we confirmed these 100% ‘made from waste’ slabs are potential low cost, energy-saving alternatives to ceramic tiles.

Impact of minor iron content on crystal structure and properties of porous calcium silicates during synthesis

We investigate the impact of minor iron content on the crystallization behavior and thermal stability of hydrothermally treated calcium silicates for insulation at high temperatures. The impurity content of the raw materials (micro silica and quicklime), particularly iron, varies greatly with the production site and method. In this work the porous calcium silicate is synthesized with a Ca/Si molar ratio of 1. To systematically study the iron impact on crystallization during synthesis of calcium silicates, we introduce different amounts of iron (Fe/Si = 0 to 0.013) into the reactants. Using Fourier transform infrared spectroscopy we find a pronounced decrease in the number of 3-bridging oxygen coordinated Si sites in the calcium silicate with increasing iron content. The X-ray diffraction results revealed that the fractions of tobermorite, calcite, and amorphous phases increase with iron content, whereas the fraction of xonotlite phase decreases. These phase changes affect the compressive strength and thermal shrinkage of the calcium silicates. The compressive strength decreases with increasing iron content until amorphous phase becomes dominant, and then it increases again. The shrinkage increases from 1.3% at 1050 °C for the reference sample, to 30.4% for the sample with Fe/Si = 0.01. We discuss why such a small amount of iron can greatly affect the crystal structure of calcium silicates and deteriorate the physical performances of final products. Therefore, the iron contamination of raw materials should be avoided to ensure high temperature stability of porous calcium silicates.

Use of extractants in the synthesis of calcium silicates and calcium silicate-based materials

During hydrothermal synthesis of calcium hydrosilicates from phosphogypsum and silica gel, the addition of quaternary ammonium bases during the crystallization step makes it possible to decrease the particle size and preserve the high disparity of calcium silicate product (wollastonite) after high-temperature annealing (from 900 to 1200°C). Solid extractants (TVEKS) based on xonotlite and wollastonite were obtained and tested with the use of a binary extractant, namely, methyltrioctylammonium di(2-ethylhexyl)dithiophosphate. The methods of preparation of organomineral paints based on calcium hydrosilicate were designed with the use of binary dyes of various compositions. Shell ceramic cobalt paints on a wollastonite carrier were obtained with the use of extraction-pyrolitic method.

An innovative CaSiO3 dielectric material from eggshells by sol–gel process

Calcium silicate (CaSiO3), wollastonite, with a molar ratio of CaO:SiO2 of 1:1, was synthesized by a sol–gel process and sintered at 1,100°C for 1 h. The synthesis of calcium silicate was carried out using chicken eggshells as the starting material possessing several advantages such as low cost, high purity, and less moisture sensitivity, when compared with those obtained from metal alkoxide precursors via the sol–gel process. The CaSiO3 samples have the triclinic or anorthic phase formations and good electrical properties. The dielectric constant and electrical conductivity are 62.59 ± 0.44 and 8.0052 × 10−4 (Ω.m)−1, respectively, at 25°C and 1 MHz. The transmission electron microscopy (TEM) images of the samples show a good dispersion and uniform particles with an average diameter of about 0.5 nm. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM), and Simultaneous thermal analysis (STA) were used to verify the synthesis.

Synthesis of calcium silicate hydrate/polymer complexes: Part I. Anionic and nonionic polymers

High molecular weight anionic polymers have been incorporated into the calcium silicate hydrate (C–S–H) structure during precipitation of quasicrystalline C–S–H from aqueous solution. The anionic polymers studied were poly(methacrylic acid), poly(acrylic acid), and the sodium salt of poly(vinyl sulfonic acid). Expansion of the interlayer spacing coupled with high-carbon contents confirmed that the polymers intercalated between the layers. D-gluconic acid behaves similarly. Intercalation characteristics strongly depended on both the type of polymer and Ca/Si molar ratio of C–S–H; intercalation reached a maximum at an initial Ca/Si = 1.3 in all cases. Poly(vinyl alcohol) was the only nonionic polymer among those studied that was incorporated into C–S–H. Evidence for interlayer intercalation is less definite. The C–S–H/polymer complexes were examined by Fourier transform infrared spectroscopy, 29Si nuclear magnetic resonance magic angle spinning, and 13C cross-polarization, magic angle spinning nuclear magnetic resonance spectroscopy.

Synthesis of calcium silicate hydrate/polymer complexes: Part II. Cationic polymers and complex formation with different polymers

Some high molecular weight cationic polymers, poly(diallyldimethylammonium chloride) (PDC) and poly(4-vinylbenzyltrimethylammonium chloride) (PVC), have been incorporated into the calcium silicate hydrate (C–S–H) structure during precipitation of quasicrystalline C–S–H from aqueous solution. Expansion of the interlayer spacing [0.9 nm (PDC), 1.5 nm (PVC)] and a high-carbon content provided evidence that these polymers were intercalated between layers of C–S–H when Ca/Si <1.0. Intercalation characteristic properties strongly depended on both of the type of polymer and Ca/Si ratio in C–S–H. Poly(4-vinyl-1-methylpyridinium bromide) and methyl glycol chitosan (iodide) also interacted with C–S–H, probably by surface adsorption. The C–S–H/polymer complexes were examined by Fourier transform infrared spectroscopy, 29Si nuclear magnetic resonance magic angle spinning, and 13C cross-polarization, magic angle spinning nuclear magnetic resonance spectroscopy. Mechanisms of intercalation of different kinds of polymers between the C–S–H layers are discussed.