Although, more than two-thirds of the Earth is covered by water, shortage of potable water is a serious issue that many countries suffer from. Furthermore, the worldwide rapid growth of industry and ...population has resulted in a large boom in demand for fresh water. The solar still, in many respects, is an ideal source of fresh water for both drinking and agriculture; it is one of the most important and technically viable applications of solar energy. There are many types of solar still; the simplest and most proven is the basin type. Investigations showed that the basin-type solar still has been found to be of limited performance. Numerous experimental and numerical investigations on basic types of solar still have been reported in various literatures. An extensive review for solar desalination systems has been carried out in this paper.
Display omitted
•WG + HEDP were firstly used as mixed depressants in magnesite flotation.•The inhibition mechanism of WG + HEDP was studied.•WG + HEDP could co-adsorb on minerals surface.•WG + HEDP ...could inhibit dolomite and calcite simultaneously.
The decalcification of magnesite remains a difficult subject in mineral flotation. In this work, water glass and HEDP (1-hydroxyethylene-1,1-diphosphonic acid, expressed as WG + HEDP) were performed as the mixed depressants in magnesite-dolomite-calcite flotation separation. Micro-flotation test was conducted to study the inhibition effect of the mixed depressants, it indicated that 20 mg/L water glass and 15 mg/L HEDP were the optimal dosages because of the maximum differences in flotation recoveries. The inhibition mechanism of the mixed depressants was revealed by ways of zeta potential measurement, contact angle test and X-ray photoelectron spectroscopy (XPS) test. It could be concluded that WG + HEDP could co-adsorb on minerals surface, but they co-adsorbed stronger on dolomite and calcite surface than magnesite. Furthermore, sodium oleate (NaOL) could further adsorb on magnesite but not dolomite and calcite surface, resulting in the differences in wettability and floatability of minerals. At last, the real ore experiment confirmed the effectiveness of WG + HEDP on magnesite flotation.
Pb2+ ions and water glass are commonly used as the activator and depressant, respectively, in the flotation separation of scheelite from calcite and fluorite in industry. The interactive effects of ...Pb2+ ions and water glass are rarely reported. In this paper, the effects of Pb2+ ions on the flotation behavior of scheelite, calcite, and fluorite in the presence of water glass were investigated through single mineral flotation experiments, zeta potential measurements, solution chemistry calculations, and X-ray photoelectron spectroscopy (XPS) tests. The flotation results showed that at optimal conditions, Pb2+ ions could activate scheelite flotation and enhance the depression effects of water glass on the calcite and fluorite flotation compared with water glass alone. Solution chemistry calculations and zeta potential analysis indicated that after Pb2+ ions adsorption, water glass could strongly adsorb onto the calcite and fluorite surfaces and inhibit the NaOL adsorption, while on the scheelite surface, water glass could hardly adsorb and thus NaOL adsorption continued. XPS results further revealed that Pb2+ ions combined with WO bond to form the W-O-Pb2+ structure on the scheelite surface which could be the active sites for NaOL adsorption, while on the calcite and fluorite surfaces, the Pb-water glass polymers (polycondensation product of water glass and Pb2+ ions) and water glass combined with CaO bond to depress their flotation.
Display omitted
•Pb2+ ions could slightly activate scheelite flotation in the presence of water glass.•Pb2+ ions could enhance the depression effects of water glass on calcite and fluorite flotation.•Pb2+ ions combined with W‐O bond to form W-O-Pb2+ structure on scheelite surface, which increased NaOl adsorption.•Pb-water glass and water glass combined with Ca‐O bond on calcite and fluorite surfaces, which impeded NaOl adsorption.
Display omitted
•Solid silica gel beads made from low cost sodium silicate precursor.•Linear trend in CO2 adsorption with increased amine loadings.•Significant CO2 adsorption at lower ...temperature.•Effect of surface area, pore volume, CO2 adsorption w.r.t. amine loading studied.
In this work, porous silica gel-solid beads have been made from economically affordable water–glass precursors via sol–gel nano casting technique. A stable nanometric silica sol was prepared first from water glass and studied for surface potential and sol to gel transition. A free-flow, injectable gel was obtained upon aging the sol which was then assembled into spherical silica beads in a chemical bath. A surface area of 304.7m2g−1 was obtained for water glass derived silica gel beads. These gel beads were impregnated with 3-aminopropyltrimethoxysilane (APTMS) and polyethylenimine (PEI) active functional groups at different percentages for turning the gel beads as sorbents for CO2 gas adsorption. The effect of amine loading on the thermal stability, morphology as well as porosity was studied and was correlated with CO2 adsorption values. Depending upon the amount of amine loaded in the gel support CO2 uptake was found varied. These amine modified silica gel porous adsorbents showed CO2 adsorption capacity at temperatures as low as 100°C; samples modified with 15wt% PEI had CO2 adsorption capacity of 1.16mmolg−1 at 50°C.
The flotation separation of fluorite and calcite poses a long-standing challenge in the mineral processing industry because of their similar physicochemical characteristics. This study uses sodium ...oleate (NaOL) as the collector and Pb-water glass as the depressant to improve the fluorite-calcite separation efficiency. The effect of Pb-water glass was analyzed using micro-flotation experiments, calculations of solution chemistry, X-ray photoelectron spectroscopy (XPS), zeta potential and time of flight secondary ion mass spectrometry (ToF-SIMS). The results of micro-flotation experiments show that Pb-water glass exhibits a stronger selective depression effect on calcite than water glass alone, but is considerably less sensitive to fluorite flotation. The calculations of solution chemistry, XPS and zeta potential results show that the improved depression effect can be attributed to lead ions, which not only increase the adsorption of silicate species on the calcite surface but also improve the formation of Pb-silicate polymer species. The ToF-SIMS results further show that the adsorption of Pb-water glass on the calcite surface interferes with the adsorption of NaOL on the calcite surface, thereby reducing the floatability of calcite.
•Fluorite is difficult to separate from calcite using only a water glass depressant.•Pb(NO3)2 enhances the selective depression effect of water glass on calcite.•The adsorption mechanism of Pb-water glass on the mineral surface is discussed.
Bioinspired superhydrophobic surfaces (SHS) have potential application prospects in many fields, but weak mechanical stability of the microstructures has become the main bottleneck. In this work, the ...water-glass strengthened the interfacial force between the inorganic SiO2 and ZnO particles and the substrate through chemical reaction rather than physical embedding, which obtains a robust superhydrophobic surface. Based on surface characterization and analysis, the mechanism of the water-glass that played a role of enhancing the interface between the particles and the substrate in the coating was explored and proposed. Furthermore, the effect of the treatment temperature on the surface structure of the water-based paint during the spraying process was studied. Through simulating different environments, the anti-acid and -alkali resistance and anti-aging ability were tested in the full pH range or under strong UV irradiation, showing an excellent performance. Different mechanical stability tests confirmed that the silicate network structure enhances the binding force between the particles, improving the robustness of the superhydrophobic surface. This work may provide a new insight for the construction of superhydrophobic surfaces with enhanced interfaces.
Display omitted
Display omitted
Flotation separation of scheelite from calcite remains a challenge because of the presence of Ca active sites on both mineral surfaces and of their similar physicochemical ...characteristics. In this study, the effect of Zn2+ and its addition sequence on flotation separation of scheelite from calcite was investigated via micro-flotation experiments, zeta potential measurements, solution chemistry calculations, and X-ray photoelectron spectroscopy (XPS) tests. The Zn-water glass (a mixture of Zn2+ and water glass) exhibits a better selective depression effect on calcite than the water glass alone but is much less sensitive to scheelite flotation. However, when Zn2+ is added prior to the water glass, both scheelite and calcite are significantly depressed. The superior selective depression effect of Zn-water glass arises from the selective adsorption of the Zn-silicate polymer and Si(OH)4 on the calcite surface, while the significant non-selective depression effect of Zn2+ added prior to the water glass is due to the adsorption of the hydrophilic Zn species on both scheelite and calcite surfaces.
Display omitted
•Refuse mudstone, GGBS and red mud were used as the precursors for geopolymer.•A combination of water glass and NaOH were used for a desired activator modulus.•The coupled influence ...of refuse mudstone and water glass contents was investigated.•UCS and BTS tests were conducted and analysed on geopolymer composites.•Failure mode and SEM were analysed and compared with mechanical results.
In this study, refuse mudstone, ground granulated blast-furnace slag (GGBS) and red mud were used as the precursor materials for geopolymer. Water glass was used as the alkaline activator for polymer synthesis and standard sand was used as the aggregate in the polymer composites. A series of laboratory tests including unconfined compressive strength (UCS) tests, Brazil tensile strength (BTS) tests, scanning electron microscopy (SEM) tests were carried out for mechanical and microstructural analysis. The coupled influence of the content of refuse mudstone (P) and the content of alkaline activator (Q) was investigated. Results show that it is feasible to synthesize geopolymer using refuse mudstone, GGBS and red mud. The produced geopolymer composites could have the highest UCS of 23.48 MPa (P = 30% and Q = 25%) and the highest BTS of 2.98 MPa (P = 30% and Q = 10%). Due to the inactive crystal phases in refuse mudstone, the UCS of geopolymer composites was increased and the strain at the UCS (εUCS) was increased. The influence of Q on the UCS and εUCS was not evident and it was affected by P. Similarly, the influence of P and Q on the BTS of geopolymer composites was also found to be dependent on each other. Compared with cemented paste backfill composites, the relatively high strength and small permeability of geopolymer composites originated from its compact microstructure. The influence of P and Q on the geopolymer composites was also confirmed by failure mode analysis and SEM analysis at the micro-scale.
•Fresh-state properties of grouts with cement, fly ash, bentonite and SP are studied.•Mechanical properties of grouts with cement, FA, B, SP and water class are studied.•Combined effects of fly ash, ...bentonite, superplasticizer and water glass are studied.•Optimum volume ratios of double-slurry grouts with FA, B and SP are discussed.•Microstructure characteristics of cement-based grouts with FA and B are presented.
To ensure desirable flowability, enough penetrability and less leaching of grouting materials in geotechnical engineering, the ASTM Type I Portland cement (PC), class F fly ash (FA), bentonite (B), superplasticizer (SP) and water glass were designed to improve properties of grouting materials in different aspects. The fresh-state properties i.e. flowability, spreading ability, bleeding and setting time; mechanical properties i.e. flexural strength and compressive strength; and microstructures of the cement-based grouts were investigated. The water/solid (W/S) ratio is selected as 1.0, the amounts of FA, bentonite and SP by mass of PC were 0–40%, 0–15% and 0.7%, respectively. The volume ratios of cement-based suspensions and water glass were selected as 1:1, 2:1 and 3:1. The results show that the FA and 0.7% SP enhance the flowability and spreading ability of fresh grouts, and the bentonite can enhance the stability. The effects of various FA, B, SP and water glass contents on flexural strengths of grouts are different. The class F FA, B and 0.7% SP reduce the compressive strength of hardened grouts. The performance of cement-based grouts with 20–30% class F FA, 0–5% bentonite, 0.7% SP and volume ratios of 2:1–3:1 can satisfy the requirements of high performance, environmental friendliness and low costs in geotechnical and underground engineering.
In this paper, hybrid silica aerogels were prepared by methltrimethoxysilane (MTMS) and water-glass co-precursor through two-step sol-gel process followed by freeze drying (FD). The characteristics ...of aerogels were strongly affected by the molar ratio of MTMS/Water-glass. When the molar ratio is 5.1, hybrid aerogel was obtained with good performances, such as low density (0.083g/cm3), high contact angle (155.1°) and low thermal conductivity (0.0226W/m·K). The density, contact angle and thermal conductivity of aerogels based on co-precursor are still showing excellent thermal stability with the same performances after 550°C heat-treatment.
Display omitted
•Hybrid aerogel based on organic and in-organic silicon source was prepared.•Hybrid aerogel was prepared under freezing drying.•The hybrid aerogel shows high thermal stability and low thermal conductivity.
PDF
