Gelation, Fragmentation and Reorganization of Precipitated Silica

Abstract Bauxite reaction residue (BRR) produced from the poly-aluminum chloride (PAC) coagulant industry is a solid acidic waste that is harmful to environment. A low temperature synthesis route to convert the waste into water glass was reported. Silica dissolution process was systematically studied, including the thermodynamic analysis and the influence of calcium and aluminum on the leaching of amorphous silica. Simulation studies have shown that calcium and aluminum combine with silicon to form hydrated calcium silicate, silica–alumina gel, and zeolite, respectively, thereby hindering the leaching of silica. Maximizing the removal of calcium, aluminum, and chlorine can effectively improve the leaching of silicon in the subsequent process, and corresponding element removal rates are 42.81%, 44.15%, and 96.94%, respectively. The removed material is not randomly discarded and is reused to prepare PAC. The silica extraction rate reached 81.45% under optimal conditions (NaOH; 3 mol L−1, L S−1; 5/1, 75°C, 2 h), and sodium silicate modulus (nSiO2:nNa2O) is 1.11. The results indicated that a large amount of silica was existed in amorphous form. Precipitated silica was obtained by acidifying sodium silicate solution at optimal pH 7.0. Moreover, sodium silicate (1.11) further synthesizes sodium silicate (modulus 3.27) by adding precipitated silica at 75°C.

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Syngenetic rapid growth of ellipsoidal silica concretions with bitumen cores

Scientific Reports ◽

10.1038/s41598-021-83651-w ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Hidekazu Yoshida ◽

Ryusei Kuma ◽

Hitoshi Hasegawa ◽

Nagayoshi Katsuta ◽

Sin-iti Sirono ◽

...

Keyword(s):

Organic Matter ◽

Early Diagenesis ◽

Ph Change ◽

Carbon Preference Index ◽

Diffusion Growth ◽

Silica Precipitation ◽

Precipitated Silica ◽

Preference Index ◽

Decomposition Of Organic Matter ◽

Growth Diagram

AbstractIsolated silica concretions in calcareous sediments have unique shapes and distinct sharp boundaries and are considered to form by diagenesis of biogenic siliceous grains. However, the details and rates of syngenetic formation of these spherical concretions are still not fully clear. Here we present a model for concretion growth by diffusion, with chemical buffering involving decomposition of organic matter leading to a pH change in the pore-water and preservation of residual bitumen cores in the concretions. The model is compatible with some pervasive silica precipitation. Based on the observed elemental distributions, C, N, S, bulk carbon isotope and carbon preference index (CPI) measurements of the silica-enriched concretions, bitumen cores and surrounding calcareous rocks, the rate of diffusive concretion growth during early diagenesis is shown using a diffusion-growth diagram. This approach reveals that ellipsoidal SiO2 concretions with a diameter of a few cm formed rapidly and the precipitated silica preserved the bitumen cores. Our work provides a generalized chemical buffering model involving organic matter that can explain the rapid syngenetic growth of other types of silica accumulation in calcareous sediments.

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NR/precipitated silica/dodecanol composites: Torque, hardness and morphology behaviors

IOP Conference Series Materials Science and Engineering ◽

10.1088/1757-899x/1122/1/012115 ◽

2021 ◽

Vol 1122 (1) ◽

pp. 012115

Author(s):

Philbert ◽

K N Hafni ◽

I Surya

Keyword(s):

Precipitated Silica

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Hybrid Silica-Based Fillers in Nanocomposites: Influence of Isotropic/Isotropic and Isotropic/Anisotropic Fillers on Mechanical Properties of Styrene-Butadiene (SBR)-Based Rubber

Polymers ◽

10.3390/polym13152413 ◽

2021 ◽

Vol 13 (15) ◽

pp. 2413

Author(s):

Mariapaola Staropoli ◽

Vincent Rogé ◽

Enzo Moretto ◽

Joffrey Didierjean ◽

Marc Michel ◽

...

Keyword(s):

Mechanical Properties ◽

Silica Nanoparticles ◽

Synergetic Effect ◽

Mechanical Analysis ◽

Rubber Matrix ◽

Styrene Butadiene Rubber ◽

Butadiene Rubber ◽

Precipitated Silica ◽

Scanning Transmission ◽

Styrene Butadiene

The improvement of mechanical properties of polymer-based nanocomposites is usually obtained through a strong polymer–silica interaction. Most often, precipitated silica nanoparticles are used as filler. In this work, we study the synergetic effect occurring between dual silica-based fillers in a styrene-butadiene rubber (SBR)/polybutadiene (PBD) rubber matrix. Precipitated Highly Dispersed Silica (HDS) nanoparticles (10 nm) have been associated with spherical Stöber silica nanoparticles (250 nm) and anisotropic nano-Sepiolite. By imaging filler at nano scale through Scanning Transmission Electron Microscopy, we have shown that anisotropic fillers align only in presence of a critical amount of HDS. The dynamic mechanical analysis of rubber compounds confirms that this alignment leads to a stiffer nanocomposite when compared to Sepiolite alone. On the contrary, spherical 250 nm nanoparticles inhibit percolation network and reduce the nanocomposite stiffness.

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On the Relation between Natural and Enforced Syneresis of Acidic Precipitated Silica

Polymers ◽

10.3390/polym6122896 ◽

2014 ◽

Vol 6 (12) ◽

pp. 2896-2911 ◽

Cited By ~ 7

Author(s):

Sebastian Wilhelm ◽

Matthias Kind

Keyword(s):

Precipitated Silica

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Brazil & Germany: Evonik – precipitated silica

Focus on Pigments ◽

10.1016/j.fop.2015.07.022 ◽

2015 ◽

Vol 2015 (7) ◽

pp. 5 ◽

Cited By ~ 1

Keyword(s):

Precipitated Silica

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Processing Technogenic Raw Materials-Phosphorus Slags with the Production of Precipitated Nanosilica and Simultaneous Recovery of Valuable Components

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.316.637 ◽

2021 ◽

Vol 316 ◽

pp. 637-642

Author(s):

Yelena G. Bochevskaya ◽

Zaure B. Karshigina ◽

Aynash S. Sharipova

Keyword(s):

Specific Surface ◽

Raw Materials ◽

Nitric Acid Concentration ◽

Process Conditions ◽

Flow Sheet ◽

Process Duration ◽

Precipitated Silica ◽

Component Content ◽

Slag Processing ◽

White Soot

The paper provides a flow sheet of the phosphorus slag processing to produce precipitated silica (white soot). The process conditions for opening phosphorus slag at the I stage of leaching have been selected: the nitric acid concentration is 3.5 mol/dm3; the ratio S:L = 1:3.5; the temperature is 60 oС; and the process duration is 1 hour. The parameters of the white soot production II stage have been determined: the HNO3 concentration is 6.5 mol/dm3; the ratio S:L = 1:3.5; the temperature is 50 oС; and the process duration is 1 hour. The temperature effect on the white soot structure and the specific surface have been established. At optimal process parameters, the white soot batches have been obtained with the main SiO2 component content of 88.2 and 90.5 %, and a specific surface of 170 and 182 m2/g, respectively. The through recovery of silicon into a commercial product is 98.0 % of its initial content in slag.

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