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Fungal Biodeterioration
Published in Thomas Dyer, Biodeterioration of Concrete, 2017
The issue of calcium is a still more interesting one. Unlike the other micronutrients, citric acid production is generally increased when calcium levels increase in solution [33]. Calcium will react with citric acid to produce calcium citrate. In calcareous rocks and concrete, the precipitation of calcium citrate within pores will lead to cracking and fragmentation. This process will be discussed in more detail later in this chapter, since it has serious implications for concrete durability. However, the fact that citric acid production is stimulated by the presence of calcium—and hence proximity to calcium-bearing minerals—suggests that this is another means by which fungi attempt to maintain levels of nutrients, since a cracked mineral surface is likely to yield more nutrients than one which is intact.
Evaluation and mechanism of ultrasound-assisted electrochemical desulfurization using citric acid as the electrolyte solution
Published in International Journal of Coal Preparation and Utilization, 2023
Jin Liu, Hai Yang, Chaoshun Jiang, Chenfei Shi, Xing Xing, Chenye Guo
Through qualitative and quantitative analysis of R-coal, E-coal, and U-coal, the main components of desulfurization reaction in coal were gypsum, calcium sulfate, pyrite, white iron ore, zinc sulfide, chalcocite, and sulfide. Citric acid and water would ionize to form H+, carboxyl radicals, and citrate ions (as in Table 11(a)) to maintain an acidic environment during electrolysis (Pattanaik et al. 2020; Zhang et al. 2021). Under ultrasonic enhancement, the crystal structure of the gypsum was destroyed (as in Table 11(b)). EDS test showed that calcium element was reduced, indicating that gypsum and calcium sulfate were ionized and removed (Cao, Xu, and Jiang 2021). At higher concentrations, citric acid can complex with calcium ions to form calcium citrate which is slightly soluble in water (Zhao et al. 2016), as shown in Table 11(c)). FeS2 was oxidized to -SO42- by Fe3+, and the sulfur of chalcocite escaped as a gas under the action of H2SO4 (Chen et al. 2021). Cuprous sulfide in chalcocite reacted with sulfuric acid and oxygen to produce copper sulfate and water (Arce and González 2002). Citric acid can also complex Fe2+ and Fe3+ (Liu et al. 2020).
Effect of precursor chemistry on purity and characterization of CaCO3 nanoparticles and its application for adsorption of methyl orange from aqueous solutions
Published in Journal of Dispersion Science and Technology, 2023
Marwa Abd El-Fatah Moghazy, Gharib Mahmoud Taha
Nitrate precursors are distinguished by lowering the method temperature and forming high purity nanoparticles due to the high volatility of their decomposition yields.[40] In the studying method, the metal nitrates act as both oxidants and cation sources, while the organic compound acts as the fuel. At reduced temperature, Ca(NO3)2 thermally decomposed yields NO which is volatile and oxygen that is an oxidizing agent which accelerates the response of Ca(NO3)2 to citric acid and form calcium citrate hydrate as shown in Equation (4).[41] As the temperature increases, dehydration occurs (Equation (5)), forming calcium citrate, which converts to more stable calcium carbonate as illustrated in Equation (6).[42,43]
Preparation of anti-decay self-setting pastes of hydroxyapatite/collagen utilizing (3-glycidoxypropyl)trimethoxysilane
Published in Journal of Asian Ceramic Societies, 2018
Taira Sato, Yuki Shirosaki, Masaki Nagaya, Yoshinori Asano, Kazuaki Nakano, Hiroshi Nagashima, Mamoru Aizawa, Masanori Kikuchi
Since bone is a nanocomposite of HAp and type-I collagen, injectable bone void fillers composed of apatitic calcium phosphate and type-I atelocollagen have been sold worldwide as Boneject® (Koken, Japan) and Collagraft® (NeuColl, USA) [9–11]. They are simple mixtures of these contents; thus, their bone tissue reactions are phagocytosis of collagen by macrophages and osteoconduction to calcium phosphate particles with slight resorption by osteoclasts. In addition, they require a thick tube to inject them into bone defects. The hydroxyapatite/collagen bone-like nanocomposite (HAp/Col) proposed by the authors [12–15] has a bone-like nanostructure, and it is the first material that is completely incorporated into the bone remodeling process and whose resorption rate can be controlled by the crosslink ratio of its collagen content. Sponge-like porous HAp/Col, sold as Refit® in Japan, demonstrated faster bone regeneration and filler resorption than those of porous β-TCP in clinical trials, moreover, and is clinically used in Japan [15]. Hence, HAp/Col is a promising candidate for use as a bioresorbale bone substitute for other materials besides porous materials. We recently reported on HAp/Col pastes using sodium alginate as a hardening agent [16–18] and concluded that supplementation of large amounts of calcium salts other than HAp was necessary to obtain sufficient anti-washout properties. Even though the chemicals calcium citrate and calcium carbonate show no harm to tissues, huge amounts of them might decrease and/or inhibit the biological advantages of HAp/Col.