A novel low temperature synthesis route to convert environmentally harmful silica-rich waste incineration bottom ashes into ordered mesoporous silica is reported. Bottom ash is a major by-product of ...municipal solid waste incineration with limited recycling options due to harmful contaminants. In this study, a low temperature alkaline dissolution process was employed to synthesize sodium silicate instead of a conventional high temperature fusion process. Moreover, the dissolution process was systematically investigated to attain fundamental insight into the hydrolysis of silica from bottom ash, which is currently lacking in the existing literature. The mineralogical composition of the ash residues before and after desilication experiments was quantified via Rietveld analysis to understand the formation of by-products, such as geopolymeric gels and zeolites. These by-products hinder the dissolution of the silica because of the following two factors: Firstly, their formation consumes part of the soluble silicate and, secondly, the precipitation of the by-products around the etching particles of bottom ash act as a passivating layer which hinders the diffusion of soluble silica away from the particle. The optimized reaction temperature and reaction time for the silica extraction was observed to be 75 °C for 48 h. A sequential extraction under these conditions can successfully attain an extraction efficiency of 70% of the silica. Subsequently, the sodium silicate derived from the bottom ash was used to synthesize mesoporous silica with a high specific surface area and purity of 870 m2/g and 99 wt %, respectively.
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•A low temperature synthesis route of sodium silicate from bottom ash is reported.•Dissolution mechanism and side reactions during silica extraction were identified.•Formation of geopolymeric gels and zeolites hinders the dissolution of silica.•High quality mesoporous silica was synthesized from BA-derived sodium silicate.•The mesoporous silica show high specific surface area (870 m2/g) and purity (99 wt%).
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•Microwave heating of water glass is a cost-effective, fast process to make porous scaffolds offering high design flexibility.•Energy, rather than power or time alone, determines ...water content; power influences pore structure more effectively than exposure time.•Phase diagram offers guidelines for making foams with customised porosity.•WG foams exhibit compressive strength similar to Bioglass® scaffolds with the same porosity and promising bioactivity and biodegradation behaviour.
Low-cost, porous, and mechanically resilient structures are required for bone replacement and tissue engineering applications. Numerous materials have been proposed, but few reached clinical efficacy. Starting from sodium silicate solution (water glass; WG), we developed a rapid fabrication route by microwave processing, yielding pure WG foams with high, tuneable porosity (up to 94%) and sizes of up to tens of centimetres within a few minutes. Based on experimental results and a physics-derived model description of the drying process we developed a phase diagram, offering a guideline to make WG foams with customised porosity. Combining X-ray diffraction, scanning electron microscopy and micro-computed tomography, we deduced relations between processing parameters, pore size, and pore size distribution. Pore diameters span 10 to 1000 μm, which is in the range required for the ingrowth of healthy bone. The compressive strength is equal or higher than the values reported for similar bioactive glass foams. The degradation tests in simulated body fluid showed promising bioactivity and biodegradation. Together with the purity of the material, lacking any additives, the WG foams are attractive for biomedical applications.
Arionid slugs can be serious pests on horticultural and agricultural crops. Using slug movement barriers is a potentially effective method to control slug damage. We evaluated the performance of ...waterglass (sodium silicate) and copper foil as barriers against Arion vulgaris movement both in a controlled experiment and in a semi-field validation under natural conditions. We used strawberry fruits as baits behind the barriers and monitored slug movement and damage to the strawberries. In the controlled experiment, copper foil barriers delayed but did not prevent passage, whereas waterglass barriers completely hindered slugs from passing. Barrier width (3, 4 or 6 cm) did not affect the passability of the barriers. In the semi-field validation, there was no difference in slug damage events between pots with and without copper foil barriers. Waterglass barriers applied to the pots reduced slug damage events by 50% compared with pots without a barrier. Using waterglass to hinder slug movement may prove to be a cost-effective method to control slug damage in horticulture without any adverse side effects on non-targeted organisms.
•Slug movement barriers can be used to control slug damage on crops.•Waterglass and copper foil were evaluated as barriers against Arion vulgaris.•Copper foil barriers delayed, but did not prevent slug passage.•Waterglass prevented passage and reduced crop damage in a semi-field validation.
Abstract
Bioinspired, graded structures with hierarchical porosity, combining high surface area with low density, are attractive for a wide range of applications. Local adaptation of properties makes ...it possible to fine‐tune their strength and degradation kinetics over time. Production of such structures is, however, still scientifically and technically challenging. A versatile approach for fabricating hierarchical, porous structures from water‐glass (WG), exploiting its inherent foaming ability in conjunction with robocasting, for applications such as, bone‐replacement scaffolds, is presented. The unique processing route that is proposed uses a purely inorganic, mouldable sodium silicate hydrogel based on WG as ink for robocasting, which makes it cost‐effective and highly environmentally friendly. The WG‐based hydrogels can be used in a pure state, and also as carrier systems, e.g., for tricalcium phosphate. Following heat treatment at a relatively low temperature of 450 °C, the robocast parts develop hierarchical porosities. Multi‐microscale porosity is created due to foaming during heating, in addition to the macroscale porosity designed during robocasting. The suggested process opens up a powerful alternative to fabrication routes presently available for hierarchically porous structures.
•Silica aerogels with novel core/shell fibrous skeleton structure were prepared.•The obtained aerogels exhibit good insulation at high temperature.•The hydrophobic aerogels could act as insulator for ...solar thermal evaporation.
We presented the fabrication of novel water glass-based monolithic aerogel reinforced with the electrospun SiO2 nanofibers (SNFs) by one-step acid catalysis in alkaline condition under ambient pressure drying (APD). Compared with the powder-like water glass-based aerogel (WAG), integrated monolithic aerogel composited with nanofibers (FWAG) was successfully constructed featured with core/shell fibrous skeleton, low density, high porosity, hydrophobic surface and enhanced mechanical property. The obtained FWAG exhibits compressive elastic modulus of 0.13 MPa for FWAG-3 and a sorption capacity of 11.83 g−1 for CH2Cl2, as well as good insulator performance used at high temperature of ∼460 °C without obvious damage. The low density, hydrophobicity and excellent insulation property enable the FWAG to be applied as insulator for solar thermal evaporation with a water evaporation rate of 1.35 kg m−2h−1 and conversion efficiency up to 88.4% at one solar intensity to produce fresh water.
•The water stability of the HDMPCC was systematically investigated.•The durability of the HDMPCC was improved by adding the fly ash and water glass.•The water stability improvement mechanism of the ...HDMPCC was revealed.
High ductile magnesium phosphate cement-based composites (HDMPCC) give full play to the superior performance of magnesium phosphate cement (MPC) in repair and reinforcement. However, when the MPC is cured in water or wet environment, the strength will be greatly reduced and the durability will be poor. In this paper, a series of experiments were conducted to investigate the effects of the substitution rate of fly ash (FA) and mass fraction of water glass (WG) on the mechanical properties and water stability of the HDMPCC. The main properties of the HDMPCC were examined, including the workability, compressive performance, bending performance and water stability. Finally, the effect mechanism was observed by using the Scanning Electron Microscopy (SEM). The results showed that the slump and compressive strength decreased as the FA substitution rate increased. In addition, when the FA substitution rate was 40%, the HDMPCC had the most excellent bending performance and water stability. The WG had little effect on the slump and compressive strength. However, the HDMPCC with a WG mass fraction of 5% had the best water stability, while excessive WG could reduce the fluidity of the slurry. The microscopic test results indicated that the FA and WG could improve the compactness of the HDMPCC. Moreover, the failure mode of PVA fiber at the fracture interface changed from the fracture failure to pull out damage after 7-day immersion, which improved the ductility of the specimens.
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•Developed a combined grouting experiment facility using a transparent chamber.•Conducted a combined grouting experiment with foam and reinforcement grouts.•Recorded evolution of ...combined grouting pressure and grout outline diffusion.•Tested the mechanical properties of grout-gravel mixture at different locations.•Analyzed the interaction between two kinds of Polyurethane/water glass grouts.
Combined grouting with multiple materials can effectively block flowing water that cannot be blocked by conventional grouting methods. Firstly, foam grouting is used to reduce the fluidity of water, and then reinforcement grouting is employed to improve the grouting effect. The traditional cement grout cannot achieve the required foamability, setting rate, and injectability. Therefore, two kinds of polyurethane/water glass grouts have been used in combined grouting experiments. In this study, we combine foam and reinforcement polyurethane/water glass to examine the interaction performance of grout seepage. We develop a visible grouting facility, including a transparent chamber and a grouting pump. We monitor the grouting pressure during the test and use a charge-coupled device camera to capture the diffusion of both grouts in the granular media. After solidification of the grouts, the samples were cored and tested to obtain the uniaxial compressive strength (UCS), porosity, and density. Our results demonstrate that the reinforcement grouting pressure increased, as compared with the foam grouting pressure, because the foam grouting blocked water and pressure conduction. The reinforcement grout intruded into the foam grout, and the UCS was improved. The higher the grouting pressure at the corresponding location of the samples, the larger the total filling ratio. The larger the volume percentage of RPU/WG, the smaller the volume percentage of FPU/WG, the greater the strength and the greater the density of the samples. The empirical strength-equivalent porosity equation is also provided in this paper. We suggest that foam grouting shall be carried out outside the stress-bearing area first, and then reinforcement grouting shall be carried out inside the stress-bearing area. This study provides a reference for the theoretical development and field application of combined grouting.
The water-glass (sodium silicates solution) is low-cost and remarkably available as a raw material for novel functional materials. In the present study, the new synthetic process from water-glass for ...glass hollow foam was developed. We found the saturation point of water retaining in water-glass during the drying process under moisture control at 140 °C. The water-glass dried at 140 °C was crushed into granular powders and filtered with three grades :45~150µm, 150~300 µm, and 300~500 µm. Furthermore, we discovered that the water-glass powder dried at 140 °C expands to spherical micro particles with glass-like envelope (glass hollow foam) by heating at > 140 °C. In addition, the water-glass dried at 140 °C and thermo-plastic powders (various super engineering plastic) were mixed and heated at > 140 °C, which led to fabrication of porous super engineering plastic/glass hollow foam composites.
Synthetic nanosilica derived from rice husk ash (RHA) is an eco-friendly and sustainable material that can replace silica sand and fumed silica. High surface area and large pore channels are required ...to extend the industrial applicability of nanosilica. To overcome the current limitations of water-glass-based synthetic nanosilica prepared from RHA (denoted as WNS), a silica-based nanoarchitecture composed of a dendritic fibrous silica nanolayer (DFSL) as the outer layer and WNS as the inner part (WNS@DFSL) was constructed. The preparation of RHA and WNS was investigated and optimized to improve the surface properties of WNS@DFSL. DFSL substantially enhances the porosity, surface area, and channel size of WNS. Moreover, the obtained WNS@DFSL can be used as an efficient template for incorporating other active components such as zeolitic imidazolate framework (ZIF-8) and ZnO. The current synthetic strategy can be used to construct hierarchical porous silica-based nanoarchitectures, thereby facilitating the industrial use of eco-friendly materials.
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•Quality of water-glass-based synthetic nanosilica prepared from RHA (WNS) is optimized.•Dendritic fibrous silica nanolayer (DFSL) is successfully fabricated on the surface of WNS to generate WNS@DFSL.•DFSL substantially enhances the porosity, surface area, and channel size of WNS.
Calcite slimes removed from malachite particles surface in malachite-calcite system with water glass, sulfide ions adsorped on malachite surface increased and then malachite can be floated easily by ...xanthate because water glass selectively interacted with calcite slimes.
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In order to eliminate the adverse effects of calcite slimes on the sulfidization-xanthate flotation of malachite, water glass was used as a depressant for calcite slimes. Micro-flotation results indicated that the floatability of malachite was restored in mixed malachite and calcite by adding water glass. Addition of the water glass into the suspension of malachite with calcite slimes promoted dispersion of these minerals and increased the selective adsorption of sulfide ions onto the malachite. The dispersion effect was supported by results of sedimentation and electrokinetics. The zeta potentials significantly increased in the negative direction, primarily for calcite, which caused removal of its slimes from the malachite surface. Thus, floatability of this mineral with xanthate was restored since it allowed a more efficient sulfidization. The DLVO calculations performed, predict the observed behaviour of the sulfidization of malachite.
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