Nano-structured Calcium Silicate Research Articles

ВЛИЯНИЕ ДЛИТЕЛЬНОСТИ МЕХАНОХИМИЧЕСКОГО СИНТЕЗА НА СТРУКТУРНО-МОРФОЛОГИЧЕСКИЕ ХАРАКТЕРИСТИКИ СИЛИКАТ-КАЛЬЦИЕВОЙ ДИСПЕРСИИ

Mechanochemical synthesis of sucrose-modified calcium hydrosilicates as precursors of calcium silicate dispersions – polyfunctional additives for cement systems was carried out on a fine grinding vibromill VM-20. The influence of duration of mechanochemical synthesis of modified hydrosilicates on the phase composition of calcium silicate dispersions, morpho-structural characteristics of the nanostructured calcium silicate xerogel particles, as well as technological features of the reaction mass of mechanochemical synthesis was studied. It was found that the viscosity of the reaction mass of mechanochemical synthesis changes non-monotonically during synthesis: in the first 2 hours of mechanochemical synthesis, the viscosity decreases; subsequently, the viscosity of the mixture increases slightly; the reaction mass maintains high fluidity throughout the entire synthesis process; the presence of raw mineral materials in the reaction mass continues to be fixed throughout the synthesis (up to 7 hours); recrystallization processes of synthesized weakly crystallized phases are activated after 6 hours of grinding.
 The volume of the synthesized xerogel was estimated from the specific surface area of the calcium silicate dispersion. It was found that the processes of recrystallization of weakly crystallized phases synthesized during mechanochemical synthesis do not affect the volume of xerogel in the composition of calcium silicate dispersion, the specific surface area of the calcium silicate dispersion increases in proportion to the duration of the mechanochemical synthesis of modified calcium hydrosilicates. The duration of mechanochemical synthesis does not affect the morpho-structural characteristics of coagulation xerogel particles.

Chemical functionalization of drinking water treatment residuals with calcium silicate hydrate to treat metal-enriched waters

Drinking water treatment residuals (DWTRs) provide an opportunity to further embrace circular economy in the urban water cycle. DWTRs surface properties can be improved by chemical functionalization to enhance the pollutant removal performance. Fe/Al-DWTRs were functionalized with nanostructured calcium silicate (nanoCSH) to remove Cu(II) and As(V) from rivers, simulating an accidental acid spill. Model raw DWTRs were generated using raw water. DWTRs were physicochemically characterized by a multi-technique approach (SEM-EDS, FT-IR, BET, XRD). Sorption experiments were performed using Cu(II) and As(V) by varying the initial pH and DWTRs doses. Compared with raw DWTRs, NanoCSH_DWTRs demonstrated a higher removal efficiency in acidic settings, faster removal rates, and higher effectiveness at lower dosages. Kinetic and equilibrium sorption experiments were performed. Experiments simulating accidental Cu and As pollution from acid drainage revealed that NanoCSH_DWTRs had a higher collective removal of As(V) when Cu(II) was present, most likely due to the synergistic relationship formed by the tertiary metal-surface complexes. An application approach was implemented using theoretical case studies. NanoCSH_DWTRs reduced the dose required to treat metal(loid)-enriched water compared to raw DWTRs. NanoCSH_DWTRs would provide an alternative as a first line of defense against the accidental release of acidic drainage.

Eco-friendly recycling of silicon−rich lye: Synthesis of hierarchically structured calcium silicate hydrate and its application for phosphorus removal

Silicon−rich lye (SRL), a byproduct generated from pre−treatment of coal−based solid waste (CSW), was considered as a preponderant silicon source to prepare hierarchically nanostructured calcium silicate hydrate (C-S-H). Through the novel mild−causticization synthesis strategy, C-S-H was prepared under optimal caustic process conditions at time of 3 h, temperature of 80 °C, Ca/Si of 1.25:1, and active CaO to obtain a conversion rate of Si up to 97.33 % during the high−value utilization of SRL. The synthesized C-S-H possesses abundant mesoporous structure and massive exchangeable active sites, whose formation is advanced through an appropriate elevation regulation of caustic temperature and time. The silicate chain depolymerization occurs to C-S-H prepared in the highly alkaline system at higher caustic temperature, longer caustic period, especially at existence of massive sodium ions, but it presents higher polymerization degree at more aluminum co-existing. The adsorption capacity up to 119.27 mg/g for C-S-H presents a valid removal performance toward phosphorus in the wastewater than massive present reports. The removal mechanism of phosphorus can be identified as the surface chemisorption and formation of calcium phosphate co-precipitation. This study can provide considerable and potential guidance to the coordinated disposal between industrial solid wastes and wastewater purification.

Microstructural evaluation of the cement stabilization of hematite-rich red soil

Red soil, composed of a clayey bed containing hematite, is used as pavement material in southern Iran. As an effective and economical technique, soil improvement with cement is common practice for improving the engineering properties of different soil and pavement layers. The formation of nanostructured calcium silicate hydrate (C-S-H) is the primary factor contributing to this improvement. On the other hand, the presence and dissolution of hematite in the soil structure can also influence C-S-H formation. The present study investigates the effects of cement on the engineering properties of the hematite-rich red soil from a microstructural point of view, with particular emphasis on changes in the C-S-H nanostructure. For this purpose, red soil specimens were stabilized with 2, 4, 6, 8 and 10 wt% cement for different curing times. The soil's engineering properties were evaluated by macrostructural testing, namely by soil particle size analysis and slake durability, water absorption, Unconfined Compressive Strength (UCS), and Ultrasonic Pulse Velocity (UPV) tests. Furthermore, the soil stabilization process and the effects of hematite on the C-S-H microstructure were evaluated by pH and Electrical Conductivity (EC) tests, X-Ray Diffraction (XRD), energy-dispersive X-ray analysis (EDX), and Scanning Electron Microscope (SEM) imaging. It was shown that adding cement to hematite-rich soil promotes Calcium Ferrite Hydrate (C-F-H) and ilavite (C-F-S-H) formation and, consequently, improves the red soil's stability and compressive strength. In fact, using 6 wt% cement, the presence of hematite, and the formation of Fe-containing nanostructures helped the red soil specimen develop a compressive strength of 2.04 MPa (17 times that of the natural soil) in seven days.

ZIF-8 derived ZnO–calcium silicate mesoporous structures: Synthesis and photocatalytic activity

Nanoscale metal-organic frameworks (MOFs) show potential as catalysts or catalyst precursors, but they suffer from difficult separation and weak stability and do not conform to practical application conventions. Herein, we demonstrate the application of nanostructured calcium silicate hydrate (C–S–H), the building block of Portland cement concrete, to fabricate hierarchically porous zeolitic-imidazolate-framework-8 (ZIF-8)-derived ZnO nanocomposites. The dispersing and stabilizing effects of the C–S–H nanoplate structure effectively suppressed the agglomeration of ZIF-8 nanocrystals during high-temperature treatment. After calcination at 450 °C, ZnO nanocomposites with high specific surface area (579 m 2 g −1 ) and hierarchical porosity were obtained. The nanocomposites were used as photocatalysts for degradation of rhodamine B and exhibited degradation efficiency as high as 95.5% within 45 min of UV light illumination with high photocatalytic stability and excellent reusability. This study demonstrated a facile way of using economic and versatile C–S–H nanostructures to fabricate MOF and MOF-derived nanocomposites with enhanced stability and functionality. •The synthesis of MOF-derived ZnO supported on environment-friendly C–S–H is reported. •The nanocomposites presented a high specific surface area (579 m 2 g −1 ) and hierarchical porosity. •High photocatalytic activity and excellent stability and reusability were achieved. •The study opens a new route for the synthesis of green MOF-derived nanostructured composites.

Electrosprayed calcium silicate nanoparticle-coated titanium implant with improved antibacterial activity and osteogenesis

To ensure clinical success, the implant and the surrounding bone tissue must not only be integrated, but also must not be suspected of infection. In this work, an antibacterial and bioactive nanostructured calcium silicate (CaSi) layer on titanium substrate by an electrospray deposition method was prepared, followed by annealing at 700, 750 and 800 °C to improve the bonding strength of the CaSi coating. The phase composition, microstructure and bonding strength of the CaSi coatings were examined. Human mesenchymal stem cells (hMSCs), Gram-negative Escherichia coli (E. coli) and Gram-positive Staphylococcus aureus (S. aureus) species were used to analyze the osteogenic and antibacterial activity of the coatings, respectively. Experimental results showed that the as-prepared CaSi coating was mainly composted of β-dicalcium silicate phase with a particle size of about 300 nm. After annealing, the thickness of the oxidation reaction layer increased obviously from 0.3 μm to 1 μm with increase in temperature, which was confirmed by the cross-sectional morphology and element depth profile. The bonding strength of the coating annealed at 750 °C (19.0 MPa) was significantly higher (p < 0.05) than that of the as-prepared coating (4.4 MPa) and the ISO 13,779 standard (15 MPa). The results of antibacterial efficacy and stem cell osteogenesis consistently elaborated that the 750 °C-annealed coating had higher activity than the as-prepared coating and the Ti control. It is concluded that after annealing at 750 °C, the CaSi nanoparticle-coated Ti implant had good bond strength, osteogenic and antibacterial activity.

Histological Evaluation of Periradicular Tissue Inflammatory Reactions and Calcified Tissue Formations After Implantation of Experimental Calcium Silicate and Hydroxyapatite Based Nanostructural Cements Into Root Canals of Rabbits Teeth

Abstract The aim of the study was to evaluate inflammatory tissue reactions and the formation of calcified tissue after implantation of experimental nanostructured calcium silicate cement (CS) and hydroxyapatite with calcium silicate cement (HA-CS) into root canals of rabbits’ teeth. The study was conducted on four rabbits of the genus Oryctolagus cuniculus. After instrumentation and irrigation, the root canals of the central incisors were dried and filled with CS, HA-CS and control material (MTA Angelus). The animals were sacrificed after 28 days. After histological preparation and hematoxylin-eosin staining, tissue samples were evaluated for the intensity and extension of inflammatory tissue reaction; continuity, morphology and thickness of the newly formed calcified tissue; and presence of giant cells, materials particles and microorganisms. Kruskal Wallis and Dunn’s post hoc test were used for data analysis (α=0.05). There were no significant differences in the intensity of inflammatory reactions between CS, HA-CS and MTA control. HA-CS showed significantly better results than MTA and CS with respect to continuity of the newly formed calcified tissue (P=0.003 and P=0.010, respectively). Significant differences in thickness of the calcified tissue existed between CS and MTA (P=0.004) and between HA-CS and MTA (P=0.012). Application of CS and HA-CS resulted in minimal inflammatory tissue response, similar to the MTA control. CS and HA-CS were more efficient than MTA in supporting hard tissue formation. The best organized newly formed calcified tissue was seen after HA-CS application.

Nano-structured calcium silicate hydrate-based composites derived from fluosilicic acid for highly efficient Cr(III) removal and methylene blue degradation from wastewater

Nano-structured calcium silicate hydrate-based composites derived from fluosilicic acid for highly efficient Cr(III) removal and methylene blue degradation from wastewater

Synthetic CaSiO3 sol-gel powder and SPS ceramic derivatives: “In vivo” toxicity assessment

The paper presents template strategy using siloxane-acrylate latex and its modified form to prepare nanostructured calcium silicate (wollastonite) containing nanosized gold and regular porosity. Optimal conditions for the annealing of silicate xerogel were outlined leading to nanoporous wollastonite with minimal porous defects (pore size corresponds to latex particles 150–200 nm). The fabrication of nanostructured wollastonite ceramics was suggested to use spark plasma sintering (SPS). The formation of porous ceramic framework (compressive strength ∼ 120 MPa) via SPS consolidation of silicate xerogel (xonotlite) contained latex template (poreformer), a feature of the method for wollastonite template synthesis. The ceramic wollastonite samples have been implanted into ICR/CD1 mice to test the toxicity of the material “in vivo”. The results are of great interest for the preparation of high-quality biomaterials for modern medicine using simple technological approaches and available raw materials.

Integrated use of magnetic nanostructured calcium silicate hydrate and magnetic manganese dioxide adsorbents for remediation of an acidic mine water

The integrated use of two solid adsorbents with magnetic properties was studied with the aim of decontaminating an acid mine water. The adsorbents were magnetic nanostructured calcium silicate hydrate (mag-NanoCSH) and magnetic manganese dioxide (mag-MnO2), both of which consist of a crystalline Fe3O4 nucleus surrounded by external amorphous layers of calcium silicate and manganese oxide, respectively. They were synthesised using simple, quick, and reproducible methods. Both adsorbents were characterised chemically, physically, and magnetically via different analytical techniques. The particle size of the adsorbents varied between 60 and 200 nm, which led to a tendency to agglomerate, and the surface area varied between 30 and 70 m2/g. The magnetic saturation of the absorbents was found to be around 57–59 emu/g, which is sufficient to ensure complete separation of these two compounds from an aqueous raffinate using a common magnet. The nanostructure and microstructure of both adsorbents had many available adsorption sites, and their chemical structure permitted efficient and simultaneous removal of cationic and anionic species present in aqueous solutions, following different adsorption mechanisms. The influence of the main variables on the adsorption of the ionic species was studied. Samples of an acid mine water were treated using both magnetic composites consecutively. In the first step, mag-NanoCSH was able to dramatically reduce the contents of many of the ions in the treated water. Then, mag-MnO2 was added to the re-acidified raffinate produced in the first step, and the resulting final aqueous solution was found to comply with the Chilean environmental regulations.

Treatment of acidic mine drainage in an adsorption process using calcium silicate modified with Fe(III)

Two compounds based on calcium silicate hydrate and modified with Fe(III), using FeCl3 and Fe(OH)3 as iron sources, were synthesized, characterized and evaluated as adsorbents for removing ionic species from an arsenic-containing acidic aqueous mine solution. The adsorbents were prepared by contacting an aqueous solution of sodium silicate with calcium hydroxide and Fe(III) compounds. The structure of these adsorbents was determined by X-ray diffraction, FTIR, DSC, BET porosimetry analysis, mean particle size measurements and chemical analysis. Both adsorbents are amorphous, consisting of large agglomerates of particles whose mean particle size averages 358nm with a surface area variable between 80 and 150m2/g. Both adsorbents showed very similar fast adsorption behavior, achieving an almost quantitative and simultaneous uptake of arsenate, phosphate, Cu(II), Zn(II) and Cd(II) ions. In the pH range between 2 and 4, it was measured a maximum arsenic and phosphate loading capacities close to 55mgAs(V)/g of adsorbent and 81mg phosphate/g adsorbent. Adsorption efficiencies over 99.94% were determined for the three metallic ions studied. The latter allowed the raffinate to comply with the limits accepted by environmental national regulation for ions discharging in natural water bodies. Particularly, As(V) equilibrium and kinetics were established in adsorption experiments. The hybrid Redlich-Peterson adsorption isotherm model explained the experimental results and a pseudo-second-order kinetic model provided a good fit to the experimental data. The modification with Fe(III) of the nano-structured calcium silicate generated a suitable adsorbent for removing arsenic species by forming highly insoluble and very stable double iron and calcium arsenate salts, keeping its ability to uptake other contaminants commonly present in acidic mine waters.

Fabrication of nano-structured calcium silicate coatings with enhanced stability, bioactivity and osteogenic and angiogenic activity

The bioactivity and stability of coatings on alloy implants play critical roles in the fast osseointegration and maintenance of a long-term life span of the implants, respectively. Herein, nano-sheet surface on bioactive calcium silicate (CaSiO3, CS) coatings on metal substrates was fabricated by combining atmosphere plasma spraying (APS) and hydrothermal technology (HT). The glassy phase in CS coatings generated by APS was converted into crystalline sheet-like nano-structures after HT treatment. Compared with the original CS coating samples, HT treatment decreased the degradation rate of the CS coatings. Moreover, the fabricated nano-structured topography of CS coatings increased the apatite mineralization ability and significantly enhanced the cell attachment, proliferation, differentiation, alkaline phosphatase (ALP) activity and expression of osteogenic genes and angiogenic factors of rat bone marrow stromal cells (bMSCs). Our results suggest that the nano-structured CS coatings have immense potential in improving the clinical performance of medical implants.

Composites of nanostructured calcium silicate hydrate with superparamagnetic particles and their use in the uptake of copper from solution

Environmental context Mining operations release dissolved metals in waste streams which can present an environmental hazard as well as an economic loss. Large volumes of waste water and low levels of metals mean that highly effective materials such as nanoparticles or nanostructures need to be employed to remove the dissolved metals from the stream. The challenge in using nanotechnology lies in the recovery of the particles, as filtration proves ineffective; this article discusses use of magnetic composites as a potential solution to this challenge. Abstract Composites of magnetite and maghemite with a nanostructured calcium silicate hydrate are generated and used in the sorption of copper from solution. The superparamagnetic components allow use of high gradient separation thereby circumventing the time-consuming recovery of the silicate by filtration. The sorption capacity of the composites is comparable to that of the pure silicate. The ideal ratio of iron oxide to calcium silicate hydrate is identified to be 10wt % of magnetite or maghemite.

Solubility and porosity of new nanostructured calcium silicate cement

Introduction. Calcium silicate cements are most commonly used materials in endodontics for many indications due to their exceptional biological and physical properties. The aim of this study was to assess solubility and porosity of new experimental nanostructured calcium silicate cement. Material and Methods. A novel nanostructured calcium silicate cement (CS), commercialized calcium silicate cement (Biodentin), traditional glass ionomer cement (GIC) (Micron Superior) and resin-reinforced glass ionomer cement (Fuji VIII) were used in this study. All materials were prepared as per manufactuers? instructions, placed in metal rings of 16?2 mm diameter and kept in an incubator at 37?C for 24 hours. After that they were weighed and put in plastic containers filled with 25 ml of water for additional 24 hours. Then after all samples were weighed again and resorption and solubility were calculated. Results. The highest solubility was found for new CS cement (12.45) followed by conventional GIC Micron Superior (11.5) and Biodentin (6.1) whereas the lowest solubility was for resin reinforced GIC Fuji VIII (3.8). These differences were statistically significant (p&lt;0.005). The highest absorption was also observed in new CS cement (24.15), followed by Biodentin (18.5) and Micron superior (17.95) while the lowest was for GIC Fuji VIII (7.75). These differences were also statistically significant except between Micron Superior and Biodentin. Conclusion. Solubility and porosity of new nanostructured calcium silicate cement were significantly higher than for traditional calcium silicate cement, traditional GIC and resin-reinforced GIC.

Batch and continuous phosphate uptake studies employing a ferrimagnetic calcium silicate hydrate composite

Composite particles of ferrimagnetic magnetite and a nano-structured calcium silicate hydrate were used for the sorption of phosphate. The composite absorbed up to 5.5 mmol phosphate per gram and settled within minutes compared to hours for the pure sorbent.

Nano-structured calcium silicate hydrate and doping of soggy sand electrolytes

An amorphous nano-structured calcium silicate hydrate with a high surface area and wide band gap can be used in soggy sand solar cells as oxide material. The material can be reinforced to yield a cell that is active over weeks despite employing the readily photo-bleached iodine/triiodide redox couple. The material offers a unique opportunity to be doped by cerium or vanadium, generating cells with higher ion mobility than observed for comparative silicate, silica or titania containing cells. In case of cerium containing oxide materials short circuit currents were twice as high as for the pure electrolyte. For vanadium containing cells current values were observed to be in excess of three times the current found in silica or pure electrolyte cells. These findings show a new possibility to enhance cell performance for soggy sand electrolyte solar cells, batteries and other devices.

Synthesis and characterization of nanostructured CaSiO3 biomaterial

Here we report a successful preparation of nanostructured calcium silicate by wet chemical approach. The synthesized sample was characterized by various physico-chemical methods. Thermal stability was investigated using thermo-gravimetric and differential thermal analysis (TG-DTA). Structural characterization of the sample was carried out by the X-ray diffraction technique (XRD) which confirmed its single phase hexagonal structure. Transmission electron microscopy (TEM) was used to study the nanostructure of the ceramics while homogeneous grain distribution was revealed by scanning electron microscopy studies (SEM). The elemental analysis data obtained from energy dispersive X-ray spectroscopy (EDAX) were in close agreement with the starting composition used for the synthesis. Superhydrophilic nature of CaSiO3 was investigated at room temperature by sessile drop technique. Effect of porous nanosized CaSiO3 on early adhesion and proliferation of human bone marrow mesenchymal stem cells (BMMSCs) and cord blood mesenchymal stem (CBMSCs) cells was measured in vitro. MTT cytotoxicity test and cell adhesion test showed that the material had good biocompatibility and promoted cell viability and cell proliferation. It has been stated that the cell viability and proliferation are significantly affected by time and concentration of CaSiO3. These findings indicate that the CaSiO3 ceramics has good biocompatibility and that it is promising as a biomaterial.

Rhodium catalysts build into the structure of a silicate support in the hydroformylation of alkenes

Abstract Rhodium is build into a nano-structured calcium silicate during the synthesis of the silicate. Thereby, it was desired to create a robust heterogeneous catalyst, which does not suffer from catalyst leaching like rhodium impregnated on a pre-formed silicate. While this was achieved, the silicate structure was adversely affected by the incorporation of rhodium — the surface area and pore volume of the material were found to be comparatively low. Alcohol and acid washing were tested to address this issue. The alcohol treatment proved detrimental as catalytic material was leached from the silicate. The acid washed rhodium containing calcium silicate was quite active in the hydroformylation of alkenes and did not suffer loss of catalyst into the product phase. Acid treated rhodium containing silicates were more active than their untreated counterparts but less selective due to access to the rhodium centers being opened.

ADSORPTION OF POLLUTANT IONS FROM RESIDUAL AQUEOUS SOLUTIONS ONTO NANO-STRUCTURED CALCIUM SILICATE

The sorption of contaminant ions existing in residual aqueous solutions onto nano-structured calcium silicate has been studied. The sorbent was prepared by chemical reaction between a soluble solution of sodium silicate and calcium hydroxide. X-ray diffraction analysis showed the amorphous character of the obtained calcium silicate, although patterns associated to wollastonite, CaSiO 3 , and larnyta-syn, Ca 2 SiO 4 were detected. The particle mean size was approximate 0.5 to 1.0 µm having an average BET surface area of 333.0 m2/g and a mean pore diameter variable between 15.8-23.6 nm. The nano-structured calcium silicates were contacted with industrial residual aqueous solutions containing, among others, Cu(II), Zn(II), Cd(II) and the anions PO 4 3-, SO 4 = and CrO 4 =, being copper (II) and phosphate the ions that were most easily and quantitatively adsorbed. The results of equilibrium experiments showed that the Redlich-Peterson adsorption isotherm model explained the experimental results for some metal ions.The experimental kinetics followed a pseudo-second-order kinetics model for Cu(II) and Zn(II) sorption.

Nanostructured calcium silicate hydrate seeds accelerate concrete hardening: a combined assessment of benefits and risks

Nanotechnology creates new possibilities to control and improve material properties for civil infrastructure. Special focus in this area is put on Portland cement and gypsum. Together their annual production is by far larger than for any other material worldwide. Nanomodification of these materials can be done during the few hours between dissolution and hardening, especially by nucleation of the re-crystallization with suitable colloids. Here we report first results in homogeneous seeding of the precipitation of calcium silicate hydrates within a real Portland cement composition. The occupational safety during the production phase and during mixing of concrete paste is addressed in detail by in vivo testing. We perform 5-day inhalation with 21-day recovery in rats and analyze organ-specific toxicity and 71 endpoints from bronchoalveolar lavage (BALF) and blood. In BALF parameters, no test-related changes were observed, indicating the generally low toxicity of the test material. Some mild lesions were observed in larynx level. In the lungs, all animals of the 50 mg/m³ concentration group revealed a minimal to mild increase in alveolar macrophages, which recovered back to control level.