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Crystallization
Published in Louis Theodore, R. Ryan Dupont, Water Resource Management Issues, 2019
Louis Theodore, R. Ryan Dupont
Although crystallization is ordinarily thought of as the deposition of a solid, crystalline phase from a liquid phase by cooling, evaporation, or both, the same principles apply to crystal formation by precipitation caused by the addition of a third substance. This other component may either react to form a precipitate or simply decrease the solubility of the precipitated material. One may also view crystallization as a phase equilibrium application. These solid crystals are usually formed from a homogenous liquid phase. If one starts with an unsaturated solution formed by dissolving some solid in liquid, more solid can be dissolved until the solution becomes saturated. More solid can still be dissolved in the solution causing it to become supersaturated. At this point, solids begin to deposit out of solution in a process often referred to as nucleation. Crystal growth continues until the solution reaches the previously attained saturation (equilibrium) point.
Solubility Behaviors of Simple Mineral Salts, and Metal Oxides, Hydroxides, and Oxyhydroxides
Published in James F. Pankow, Aquatic Chemistry Concepts, 2018
The situation is very analogous for equilibria describing the dissolution of solids, that is, for reactions like those in Eqs. (11.1)–(11.3). For a given solid, we describe: 1) Q < K as being a state of undersaturation; 2) Q = K as a state of saturation; and 3)Q > K as a state of supersaturation. When a solution is undersaturated, it can “hold” additional dissolved solid; if some solid is present, then some of it will tend to dissolve; if no solid is present, none will form. When a solution is saturated, it can hold no additional dissolved solid; if some solid is present, then none of it will dissolve; if no solid is present, none will form. When a solution is supersaturated, it is holding more than it is capable of holding at equilibrium; if some solid is present, then more of it will tend to form; if no solid is present, some will tend to form. These results are summarized in Table 11.1. If we do know that Q = K, we do not necessarily know that solid is present.
Desalination
Published in Frank R. Spellman, Hydraulic Fracturing Wastewater, 2017
Although polar substances dissolve better than nonpolar substances in water, polar substances dissolve in water only to a point; that is, only so much solute will dissolve at a given temperature. When that limit is reached, the resulting solution is saturated. At this point, the solution is in equilibrium—no more solute can be dissolved. A liquid/solids solution is supersaturated when the solvent actually dissolves more than an equilibrium concentration of solute (usually when heated).
Inhibition of calcium carbonate scale under severe conditions
Published in Petroleum Science and Technology, 2022
The saturation ratio of an aqueous solution of a salt refers to how much more of the salt is currently dissolved in the solution above that which would be present at equilibrium. Some of the salt must precipitate (or crystallize) from a supersaturated solution in order for it to come to equilibrium. The saturation ratio is an important determining factor of precipitation of salts from a solution. In a sense, the saturation ratio may be thought of as the thermodynamic "driving force" for precipitation; i.e., it is more likely that precipitation will occur easily from a higher than from a lower supersaturated solution. The degree of supersaturation is affected by changes in temperature, pressure and pH, all of which may change during the oil and gas production. It is also affected by the concentration of scaling ions (Ca2+ and HCO3-), which are two major factors to contribute the degree of supersaturation.
Contrasting geology and mineralogy of evaporative encrustations in salt-tolerant ecosystems, Maniototo basin, Central Otago, New Zealand
Published in New Zealand Journal of Geology and Geophysics, 2022
Dave Craw, Cathy Rufaut, Gemma Kerr, Dhana Pillai
If a mineral does not precipitate for nucleation or kinetic reasons, the mineral saturation index can rise above 1 and the solution becomes supersaturated with respect to that mineral. The minerals listed in Table 4 are those with highest degrees of saturation and supersaturation for the two synthetic waters created from dissolution of salts (Patearoa and Belmont saline sites), Belmont wetland water, and ephemeral runoff water collected at Hamiltons site (Table 2). All these waters are apparently supersaturated with respect to Ca–Mg carbonates but equilibrium precipitation of these minerals has not occurred, presumably for kinetic reasons. However, small amounts of Ca–Mg carbonates have been observed in evaporative precipitates at the Patearoa and Hamiltons sites, although not at Belmont (Table 1).
Microstructure tuning enables synergistic improvements in strength and ductility of wire-arc additive manufactured commercial Al-Zn-Mg-Cu alloys
Published in Virtual and Physical Prototyping, 2022
Yueling Guo, Qifei Han, Wenjun Lu, Fengchao An, Jinlong Hu, Yangyu Yan, Changmeng Liu
The effective approach to achieve superior mechanical properties is to activate the inherent strengthening mechanisms of 7xxx alloys, such as grain boundary strengthening and precipitation strengthening (Ma et al. 2014; Wang et al. 2018). Though the functionalisation with the nucleants, such as WC, etc. generates fine equiaxed microstructures and effectively improves the mechanical property (Lin et al. 2019; Martin et al. 2017), here we focus on the WAAM processing of commercial property-proven 7xxx alloys that are currently used in industries. The excellent age-hardening capability of commercial 7xxx alloys typically arises from nanoscale precipitation of the metastable Zn- and Mg-rich η’ phases (Khan et al. 2021; Sha and Cerezo 2004). Heat treatment is the key step for such precipitations, including the solution treatment to obtain a supersaturated solid solution and the ageing treatment to enable precipitations. Then comes the question whether the solution and aging treatments developed from conventional wrought 7xxx alloys are suitable for WAAM alloys, considering the non-equilibrium solidification process of WAAM. Therefore, specific heat treatments have to be developed for WAAM 7xxx alloys to maximise precipitation strengthening.