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Chemical Equilibrium
Published in Armen S. Casparian, Gergely Sirokman, Ann O. Omollo, Rapid Review of Chemistry for the Life Sciences and Engineering, 2021
Armen S. Casparian, Gergely Sirokman, Ann O. Omollo
Like the acids and bases discussed in the previous section, another group of substances comprised generally of ionic compounds that have very limited solubility in water deserves separate treatment. Examples include magnesium hydroxide (commonly known as milk of magnesia, an antacid), barium sulfate (used in enemas to diagnose colonic tumors), and silver chloride. These substances are generally referred to as “insoluble” or “slightly soluble” and are governed by a solubility equilibrium expression and a solubility product constant known as Ksp, identical in concept to the principle of equilibrium discussed in Section 4.3.
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Published in James F. Pankow, Aquatic Chemistry Concepts, 2019
This line, as plotted in Figure 19.6 from pH = 12.01 to 14.00, lies slightly below the pO2(g) = 1 atm water stability line.Example 19.4Saturation Index and Solid FormationConsider Figure 19.6 and the system wherein PbT,sys = 10–7M. For intermediate pe values where only Pb(II) is stable, use Eq.(19.4) and α0Pb(II) to compute and plot the Saturation Index (SI) vs. pH from pH = 8 to 12 for α-PbO(s). Eq.(11.6) provides the definition of SI; saturation occurs when SI = 0. Neglect activity corrections for dissolved species.SolutionSI = log Ω = log [(ion activity product)/Ks], with Ks being the solubility equilibrium constant corresponding to the ion activity product. When SI < 0, the solution is undersaturated; when SI = 0, a solution is exactly saturated with a solid; when SI > 0, a solution is supersaturated with a solid. When Ks is taken to be K*s0 for α-PbO(s), the ion activity product = [Pb2+]/[H+]2, so Ω = log [([Pb2+]/[H+]2)/K*s0]. [Pb2+] = α0Pb(II)Pb(II)T. We take Pb(II)T = PbT,sys to see if this value of Pb(II)T can lead to saturation. The plot indicates it cannot because SI < 0 at all pH. No α-PbO(s) can form at PbT,sys = 10–7M.
Quality of tap water in an urban agglomeration: 2-years’ monitoring study in Wrocław, Poland
Published in Urban Water Journal, 2022
Grzegorz Izydorczyk, Małgorzata Mironiuk, Sylwia Baśladyńska, Daria Kocek, Anna Witek-Krowiak, Katarzyna Chojnacka
We tried to see whether that was a correlation between the existence of individual elements and co-leaching from the water supply system. The data collected in Table 4 do not show any clear, distinct trends. The highest positive correlation coefficients were observed for pairs As-Tl (0.4985), Fe-Mn (0.4663), Mg-V (0.6977) and Tl-Sb (0.6214). A correlation between iron and manganese concentrations may be proof of the coexistence of these elements from the materials used for the construction of the water supply system. The highest negative correlation coefficients were recorded for pairs Cd-B (−0.8159), Cd-Sb (−0.5109), Cd-Tl (−0.8392), Cd-Cr (−0.6646) and Mg-Mo (−0.4960), which may result from significant differences in the solubility equilibrium. For a better understanding of the relationship between the occurrence of individual elements, the correlation assessment can be extended to multivariate statistics to determine whether the concentration of a given element is influenced by more than one element.
Efficient Removal of Ni(II) and Co(II) Ions from Aqueous Solutions Using Silica-based Hybrid Materials Functionalized with PAMAM Dendrimers
Published in Solvent Extraction and Ion Exchange, 2020
Mateusz Pawlaczyk, Grzegorz Schroeder
Nevertheless, both materials were found to demonstrate the highest adsorption capacity toward both Ni(II) and Co(II) ions in the solutions buffered to pH 5.4. The main reason of such a phenomenon is the fact that in a strongly acidic environment peripheral amine and internal amide groups exist in their protonated forms (–NH3+ and –NH2+–), hindering diffusion of positively charged metal ions into matrices by the repulsive interaction. Furthermore, the competitive binding of protons to surface dendritic domains may appear. On the other hand, in a slightly acidic environment (pH 6.0) metal ions might be inactivated by the formation of unhydrolyzed hydroxides due to the low values of their solubility equilibrium. Therefore, all the following adsorption experiments were conducted in slightly acidic environment at pH 5.4. Under such conditions only internal tertiary amine groups are protonated, while amide and primary amine groups remain in their unaltered form.[105] Thus, the metal ions binding in the materials structure is based on the neutral coordination of outer amine groups to the metal cations, but also on the ionic exchange between H+ ions of protonated tertiary amines and M2+ ions driven by ions diffusion, leading to coordination of tertiary amine and oxygen domains to metal cations/proton systems (Figure 4).
The Effect of Shear Rate on Aggregation and Fragmentation of Asphaltene Aggregates
Published in Journal of Dispersion Science and Technology, 2019
Hassan Soleimani-Khormakala, Mohammad Torkaman, Masoud Bahrami
The precipitation of asphaltene may occur by destabilization of oil phase with change in the crude oil temperature, composition, and pressure which are unavoidable at extraction, processing, and transportation of crude oil. The precipitation and stability of asphaltenes in crude oil can be verified under conventional techniques including optical microscopy,[14] refractive index,[15] UV-vis spectrophotometer,[16,17] and interfacial tension (IFT).[18] The precipitation of asphaltenes is an extremely piecemeal process and it is taking up to several weeks to reach solubility equilibrium.[1] Depending on the asphaltene concentration, either the bulk diffusion or surface attraction of nanoaggregates can be a rate-limiting step for asphaltene precipitation.[19] Hence, the application of existing thermodynamic models for determining the asphaltenes behavior under different conditions may be scientifically intangible and even lead to misleading prediction considering that these models are developed for experiments in which the solubility equilibration is immediately acquired.