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The Modern Cement Industry: Its Emergence and the Role of F.L. Smidth & Co.
Published in Morten Pedersen, Internationalisation and Strategic Control, 2021
Cement is manufactured by heating a mixture of limestone and other materials, traditionally clay. In the heating process, silicic acid is formed, which, together with water, combines with the limestone, producing in the material the hydraulic, i.e. water-hardening, properties that are absolutely essential when cement is used for building construction.
Contribution of Bioavailable Silicon in Human Health
Published in Debasis Bagchi, Manashi Bagchi, Metal Toxicology Handbook, 2020
As previously discussed, elemental silicon exists primarily as an oxide largely in the form of silicon dioxide. Silica, SiO2, is a silicic acid anhydride of monomeric OSA (H2SiO4), which is water-soluble and stable in aqueous solutions when relatively dilute but can polymerize and complex with numerous minerals to form silicates with aluminum silicate being the most prevalent. Several other low molecular weight, but hydrated forms, of silicic acid exist in aqueous solutions and are non-toxic. Forms of silicon that are toxic include long fibrous crystalline forms such as asbestos, which is a group of crystalline 1:1 layer hydrated silicate fibers that are classified into six types based on different physicochemical features. These include chrysotile [Mg6Si4O10(OH)8], the most common and economically important asbestos in the Northern Hemisphere, and the amphiboles: crocidolite [Na2(Fe3+)2(Fe2+)3Si8O22(OH)2], amosite [(Fe, Mg)7Si8O22(OH)2], anthophyllite [(Mg, Fe)7Si8O22(OH)2], tremolite [Ca2Mg5Si8O22(OH)2], and actinolite [Ca2(Mg, Fe)5–Si8O22(OH)2].184,185
Oryza sativa)
Published in Yong-Guan Zhu, Huaming Guo, Prosun Bhattacharya, Jochen Bundschuh, Arslan Ahmad, Ravi Naidu, Environmental Arsenic in a Changing World, 2019
Rice plants at heading stage were exposed to the half-strength Kimura B nutrient solution containing 10 μM As(III) or 10 μM DMA. Different levels of 0 (CK), 1000 (DSi), 2000 (GSi) μM Si as silicic acid were sprayed on the rice shoots at 10:10 am every day and the exposure of As and Si would last for 72 h. Thus, the ratios of Si to As(Si/As) would be 100:1 and 200:1. Silicic acid was prepared by passing potassium silicate through a cation-exchange resin (Amberlite IR-120B, H+ form).
Purification of the Sodium Hydroxide Leaching Solution of Black Dross by Removal of Silicate(IV) with Polyacrylamide (PAM)
Published in Mineral Processing and Extractive Metallurgy Review, 2021
Thi Thuy Nhi Nguyen, Man Seung Lee
Knowledge of the distribution of aqueous silicate species with solution pH is important in understanding the mechanism of silicate removal by coagulation. The distribution diagram of aqueous silicate is represented in Figure 2. The speciation diagram was constructed by using the computer program Mathematica Software (Wolfram 1996). The values for the hydrolysis constants and solubility constants (in pK form) were taken from the reported values (Antonangelo et al. 2017; Romero 2016). Silica exists as silicic acid, H4SiO4(Si(OH)4) when solution pH is less than 8. As solution pH increases, the hydrogen in the OH group attached to Si(IV) can react with the hydroxide ion consecutively, resulting in H3SiO4−(SiO(OH)3−) and H2SiO42–(SiO2(OH)22–), which are represented as Eqs. (2) and (3) (Cheng, Chen and Yang 2009; Latour, Miranda and Blanco 2016).
Aerogel composites and blankets with embedded fibrous material by ambient drying: Reviewing their production, characteristics, and potential applications
Published in Drying Technology, 2023
Jaya Sharma, Javed Sheikh, B. K. Behera
The cheapest and most reliable source of reasonably pure silicic acid for the production of silica gel has traditionally been sodium silicate (Na2SiO3). The interaction of sodium silicate with water results in silicic acid formation. Subsequently, the silicic acid undergoes polymerization, which results in the formation of silica gel, as shown by the following reactions: