where r ij and σ ij are the actual and reference distances between atoms i and j, respectively; ε o is the permittivity of free space (ε o = 8.8543 × 10 –12 C 2 J –1 m –1); ε ij is the potential well-depth; and q i and q j are the value of the charge on atoms i and j.The LJ interactions between unlike atoms are treated with the sixth-order mixing rule. 20 The atom-based summation ...
Effect of sodium hydroxide under various conditions | A quantitative estimation of the effect of sodium hydroxide on the solubility of gypsum in the presence of lime at 30, 60 and 100°C is given.
It was found the sulfate precipitation completed in 15 mins with stirring under an alkaline condition (pH ≈ 12) and was not affected by temperature (15°C to 45°C).
For example, as shown in Fig. 2 A, gypsum solubility is constant over the pH range of most natural waters, ... As shown in Fig. 2 B, the formation of Mg-silicate is favored under alkaline conditions (at initial Mg 2+ is 10 −3 M), ...
As an industrial by-product of flue gas desulfurization, flue gas desulfurization gypsum (FGD gypsum), whose main component is CaSO 4 · 2H 2 O, is an ideal raw material for mineralization. The technical problem of indirect mineralization lies in the efficient recycling of leaching agents, while amino acids have the lowest solubility at their isoelectric point, and thus …
Materials 2022, 15, 2680 2 of 13 Previous data demonstrated that the degree of exerting the negative effects was as follows: H3PO4 > H2PO4 > HPO 4 2 [10,11]. On the other hand, soluble phosphorus ...
Methodologies for removing or stabilizing soluble alkali to promote safety management of BRDAs have been proposed, such as multi-stages washing, seawater precipitation, carbonation conversion ...
As the waste of coal-fired power plant, desulphurization gypsum is mainly composed of CaSO 3 and CaSO 4, which can replace Na+ in saline-alkali soil to improve saline-alkali soil.
As Jones et al. (2015) reported, Ca 2 + could react with soluble alkaline anions such as CO 3 2 −, HCO 3 −, OH − and Al(OH) 4 −. The mechanisms of both gypsum and phosphogypsum were similar, as both materials can provide excess calcium to precipitate soluble alkali (Kopittke et al., 2005, Jones et al., 2012). Notably, phosphogypsum ...
Saline–alkali soils have high sodicity, high pH, and high levels of soluble salts, as well as carbonates. This study aimed to evaluate the effect of cattle manure and chicken manure combined with gypsum at three levels on reclaiming a saline–alkali soil, through a soil column experiment. Combined treatments were more effective than those of sole gypsum in reducing …
Figure 1 shows the calculated solubility of gypsum in solutions under various partial pressures of carbon dioxide (pCO 2 ), based on chemical equilibrium. This figure shows that gypsum can be ...
Although the reduction of water soluble Na + was not significant in HF soil under all amendments, there was a modest decrease in water soluble Na + (by 43 mg kg −1) under CaSO 4 treatment. Clearly, water soluble Ca 2+ showed a significant increase under application of CaSO 4 (by 1156–3018 mg kg −1 ) and biochar (by 791–1138 mg kg −1 ...
Phospho-gypsum is mainly composed of CaSO 4 ·2H 2 O, and other complex impurities such as soluble phosphorus, soluble fluorine, organics, or alkali metal salts. ... In this study, the influence of soluble phosphorus on the hydration process and the mechanism of calcined gypsum under deep retarding condition were studied. The data showed that ...
Gypsum can exist stably in the bauxite residue, but its lower solubility will cause a low Ca content [17]. As a result, the efficiency of gypsum to neutralize the alkalinity of bauxite residue is limited. Solubilization of gypsum by complexation is …
This study attempted to characterize the P release behavior of the saline–sodic soil amended with gypsum alone (G25 and G50: 25 and 50% gypsum requirement:) or with farmyard manure (G25FYM) and city waste compost from Karnal (G25CK) and Delhi (G25CD). ... under alkaline compared to salinity. Saline/alkaline stress was the primary driver of ...
According to experimental data (25°C), the solubility of gypsum particles in water is inversely proportional to their size at r < 1 μm and is r-invariant for larger grains. The invariance of (C …
The analysis of published data and our experimental results showed that the existing estimates of gypsum solubility in water (C m ↑) at 25°C range from 0.0147 to 0.0182 M. Such a scatter (more than 20%) is the result of a combined influence of experimental conditions and ability of gypsum to form supersaturated solutions. This influence appears most noticeable …
Armstrong (1989) compared the solubility, exchangeable sodium replacement, and clay dispersion inhibition of three calcium amendments (PG, rock gypsum, saturated gypsum solution), and the results showed that PG was the most effective in saline-alkali soil improvement. Additionally, the total P content in PG is about 2.5–7.5%, and its reuse as ...
Gypsum precipitation kinetics and solubility in the NaCl-MgCl 2-CaSO4-H2O system. ... mixing, under agitation, equal volume (100 dm 3) of equimolar. CaCl 2 (S 1) and Na 2 SO 4 (S 2) solutions ...
In this study, by integrating the geochemical modelling of PHREEQC and column leaching experiments, the dissolution of alkaline solids in bauxite residue (BR) and gypsum …
The solubility of gypsum at 20°C is 2.531 g/L or 14 mM/L, which is roughly 140 times lower than the solubility of common salt, but two orders of magnitude greater than the solubility of CaCO3 in ...
Gypsum solubility (at 25 °C) and logarithm of rate coefficients for gypsum growth at a range of temperatures (25 °C, 50 °C, 70 °C, and 90 °C) in stoichiometric solutions as a function of ...
Solubility Measurements and Predictions of Gypsum, Anhydrite, and Calcite Over Wide Ranges of Temperature, Pressure, and Ionic Strength with Mixed Electrolytes. Rock …
The databases of alkaline and alkaline earth sulfate solubilities in water at various temperatures were created using experimental data from the publications over about the last two centuries.
Alkali metals can increase the content of sulfate ions in the early solution by forming the better soluble alkali sulfates in the clinker and by promoting gypsum dissolution (within the range of alkali content added in this study), which may be one of the reasons for the elevated water-soluble hexavalent chromium content.
This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided ... alkaline (pH 7.7), and calcareous (calcium carbonate equiv- ... which reduced P solubility. ∙ Gypsum-amended and unamended soils had a
Gypsum is calcium sulfate (CaSO 4).Refined gypsum in the anhydrite form (no water) is 29.4 percent calcium (Ca) and 23.5 percent sulfur (S). Usually, gypsum has water associated in the molecular structure (CaSO 4 ·2H2O) and is approximately 23.3 percent Ca and 18.5 percent S (plaster of paris). Gypsum fertilizer usually has other impurities so grades are approximately 22 …
The analysis of published data and our experimental results showed that the existing estimates of gypsum solubility in water (Cm↑) at 25°C range from 0.0147 to 0.0182 M.