Concentration Of Na2SiO3 Research Articles

Phase Analysis of the Binary System of Cryolite (Na3AlF6) and Sodium Metasilicate (Na2SiO3)

AbstractThe phase analysis of cryolite (Na3AlF6) and sodium metasilicate (Na2SiO3) was performed by thermal analysis. The eutectic system with a region of two immiscible substances at a concentration of Na2SiO3 between 42.8 and 46.3 mol‐% was identified and the eutectic temperature determined to (886±2) °C. Based on the results of mass‐loss measurements, it was assumed that the introduced Na2SiO3 reacts with Na3AlF6 due to the formation of some nonvolatile stable compounds. The stable reaction products were identified by X‐ray diffraction analysis and IR spectroscopy of the spontaneously cooled samples, which established the formation of NaF and stable amorphous aluminosilicate compounds.

Effects of silicate concentration on anodic films formed on AZ91D magnesium alloy in solution containing silica sol

Anodic films were prepared on the AZ91D magnesium alloy in 1.0 M and 1.5 M Na2SiO3 with varied silica sol addition under the constant current density of 20 mA/cm2 at 18 °C. The surface and cross-section morphologies of the anodic films were characterized by scanning electron microscopy (SEM) and energy dispersion spectrometry (EDS). The results showed that both the surface morphologies and the thickness of the anodic film were affected by the concentration of Na2SiO3 and the additions of silica sol. The effects of Na2SiO3 concentration and silica sol addition on the solution properties were also investigated. The results showed that the addition of silica sol into Na2SiO3 solution could decrease the surface energy and the conductivity of the solution. Moreover, the anodic film formed in 1.5 M Na2SiO3 with addition of silica sol was more uniform and compact than that formed in 1.0 M Na2SiO3 with addition of silica sol. And the electrochemical impedance spectroscopy (EIS) results also indicated that the anodic film formed in 1.5 M Na2SiO3 solution with 5 vol.% silica sol addition could provide higher corrosion resistance than that formed in 1.0 M Na2SiO3 with the same silica sol addition for the AZ91D Mg alloy substrate.

Boron Sorption and Release by Allophane

AbstractTo predict B behavior in soils and its influence on plants, it is crucial to understand the mechanisms of B sorption by mineral phases. Because B reacts with clay minerals and Al and Fe oxides, it should also sorb to poorly crystalline aluminosilicates such as allophane. Boron sorption, with and following allophane precipitation, was studied in batch experiments. Solutions containing AlCl3 and Na2SiO3 (concentrations <47 mM with Al/Si molar ratio of 1:1) and B(OH)3 (0, 4.4, and 32 mM) were mixed and titrated to pH 8.0 with 1 M NaOH at two rates (1 and 5 mL min−1) at 23°C, then incubated at 23 and 90°C for 5 d. More B was removed from solution when B was present during allophane precipitation than when B of an equal concentration was reacted with freshly precipitated allophane. In addition, more B was removed when allophane was formed by slower mixing at a slower titration rate, with higher initial B concentration, and incubated at lower temperature. More B was released by repeated washing with dionized water from allophane precipitated in the presence of B(OH)3 than from allophane reacted with B(OH)3. Boron sorption was investigated with diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy. Adsorbed B was both trigonally and tetrahedrally coordinated, with the former being predominant. Boron reacted with allophane precipitate was surface sorbed. Corprecipitated B occurred only in tetrahedrally coordinated positions, presumably by substituting for Si in the tetrahedral layer. The structurally coprecipitated B is expected to be more resistant to release than the adsorbed B.

Silicate Sprays as Effective as Calcium Sprays at Suppressing Bract Necrosis in Poinsettia

Bract necrosis (BN) first appears at anthesis, and symptoms become more numerous and severe with time. Previously, we reported that 3.6 mm sodium silicate (Na2SiO3) sprays, applied during bract development, were as effective as 10 mm CaCl2 sprays at suppressing BN on `Supjibi' and `Angelika White', but only for several weeks after initial anthesis. While applying Na2SiO3 during bract development dramatically suppressed BN (7.2% of bracts with BN 46 days after anthesis vs. 33.4% for untreated plants), applying Na2SiO3 after anthesis is ineffective (35.7% BN). In 1995, suppression of BN was evaluated on `Supjibi' plants sprayed with similar concentrations (2 or 4 mm) of Na2SiO3 and CaCl2; treatments were compared to unsprayed poinsettias, or plants sprayed with either deionized (DI) water, 4 mm SrCl2, 4 mm NaCl, 4 mm MgCl2, or a solution of Na2SiO3 plus CaCl2 (1 or 2 mm each). At harvest (38 days after initial anthesis), 40.6% of the bracts on unsprayed plants and 35.8% of the bracts on DI water sprayed plants had BN. In contrasts, only 5.3% of the bracts on the 4 mm CaCl2 treated plants and 5.9% of the bracts on 4 mm Na2SiO3 treated plants had BN. Plants sprayed with 4 mm SrCl2 or the combination of 2 mm Na2SiO3 plus 2 mm CaCl2 developed BN on 7.8% and 9.2% of bracts, respectively. NaCl and MgCl2 sprays (4 mm) were not as effective (29.6 and 26.4% BN) as Ca, Si, or Sr sprays at suppressing BN over the duration of this study.

Behaviour of sodium silicate and sodium phosphate (tribasic) as corrosion inhibitors for iron

The effectiveness of sodium silicate (Na2SiO3) and trisodium phosphate (Na3PO4) as corrosion inhibitors for iron in 0.1 m NaClO4, in both aerated and deaerated solutions has been investigated. Both sodium silicate and trisodium phosphate are effective inhibitors in unbuffered solutions as a result of inhibiting the rate of the anodic iron dissolution reaction. However, the inhibition of the corrosion rate in the (final) pH range 9.6–11.6 is entirely due to the change in pH which the addition of Na2SiO3 and Na3PO4 to unbuffered solutions causes, and not to the presence of silicate/phosphate species. Where the final pH was in the range 5–7 addition of I mm sodium silicate to acidified aerated unbuffered solutions caused slight inhibition of the iron dissolution reaction when compared with a solution of the same pH. Lower concentrations of Na2SiO3 at the same final pH did not cause inhibition. Silicic acid has an approximate solubility of 1 mm and it is likely that the inhibitive behaviour in this pH range is due to the precipitation of H2SiO3 at the electrode surface. An aerated phosphate buffer of pH 7.0 inhibited both the anodic and cathodic reactions when compared with a 0.1 m sodium perchlorate solution at the same pH. This was due to the presence of phosphate species at the electrode surface. In carbonate and acetate buffers neither Na2SiO3 nor Na3PO4 caused corrosion inhibition.