Properties of fluoride in wet phosphoric acid processes: Fluorosilicic acid in an aqueous solution of H2SiF6–H20 at temperatures ranging from 298.15K to 353.15K

Guendouzi, Mohamed El; Rifai, Ahmed; Skafi, Mourad

doi:10.1016/j.fluid.2015.03.014

Cited by 13 publications

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“…N is the number of experimental points. Each point is the average of 8–10 series of experiments. b Ref . c Ref . …”

Section: Resultsmentioning

confidence: 99%

“…The solubility is determined on thermodynamic considerations based on the approach of the ion-interaction model. − This has been evaluated taking into account the ternary systems as 1-2*1-2 charge type and the solubility of the salts in acid solutions. According to the measurements of the water activity and the ion-interaction parameters, binary , and ternary given in Table , the solute activity coefficients were evaluated for the aqueous solutions of hexafluoridosilicate salts and acid. The calculated solubility m s(tot) cal was determined by eq , using the experimental value of the water activity a w and the osmotic coefficients calculated from the mixing parameters (θ MN and ψ MNX ).…”

Section: Resultsmentioning

confidence: 99%

“…During the wet process of production of phosphoric acid in the dissolution of the phosphate rock by sulfuric acid, the fluoride will be in the aqueous acid solution as hydrofluoric acid. The latter reacts with the silica, usually present in the ore but can be added if necessary, to form an aqueous solution of hexafluoridosilicic acid . The hexafluoridosilicate ion can react with the cations present in the aqueous solutions, yielding solids with the composition and properties of, for instance, malladrite (Na 2 [SiF 6 ]), hieratite (K 2 [SiF 6 ]), or NaK[SiF 6 ], which can induce fouling. , One of the major problems of the wet process of production of phosphoric acid (WPA) is related to the formation of hexafluoridosilicate scale deposits, together with other solids, such as gypsum, on the filters, pipelines, and evaporators.…”

Section: Introductionmentioning

confidence: 99%

“…Their dissolution in acid aqueous solutions could be one of the solutions to overcome the problem of fouling during the industrial production of phosphoric acid. In our earlier work, the thermodynamic properties were determined for the binary systems of hexafluoridosilicate salts and acid in aqueous solutions at T = 353.15K, to understand the phenomena governing the process of phosphoric acid production in order to contribute for solving the problem of fouling.…”

Section: Introductionmentioning

confidence: 99%

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Solubility of Mixed Ternary Systems of Hexafluoridosilicate Salts (M = Na⁺, K⁺, or NH₄⁺) in Hexafluoridosilicic Acid Aqueous Solutions at T = 353.15 K

2019

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The solubility of hexafluoridosilicate salts and acid aqueous solutions {yH 2 [SiF 6 ] + (1 − y)M 2 [SiF 6 ]}(aq) with Na + , K + , and NH 4 + was experimentally determined at various ionic strength fractions (y) with y = 0.20, 0.50, and 0.80 at the temperature 353.15 K. The precipitated solid phases obtained by filtration were characterized by X-ray diffraction, which show only the presence of a single crystalline form for each ternary system at various (y) values, Na 2 [SiF 6 ], K 2 [SiF 6 ], or (NH 4 ) 2 [SiF 6 ], respectively. To find the solubility, the thermodynamic properties of these ternary systems are required, based on the measured activity of water. Then, the water activity measurements for the mixed systems were done at various (y) values with y = 0.20, 0.50, and 0.80 from diluted to the saturated solutions, using the hygrometric method at T = 353.15 K. The related thermodynamic properties of hexafluoridosilicate salts and acid aqueous solutions were also determined using Pitzer's ion-interaction approach. The new ion-interaction parameters θ (H,M) and ψ (H,M,[SiF 6 ]) , with M = Na + , K + , or NH 4 + , of the ternary systems were evaluated and employed with the interaction binary parameters to estimate the solute activity and the osmotic coefficients of water for these aqueous solutions at T = 353.15 K. The calculated solubility of mixed systems is compared with that obtained experimentally.

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“…N is the number of experimental points. Each point is the average of 8–10 series of experiments. b Ref . c Ref . …”

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Solubility of Mixed Ternary Systems of Hexafluoridosilicate Salts (M = Na⁺, K⁺, or NH₄⁺) in Hexafluoridosilicic Acid Aqueous Solutions at T = 353.15 K

2019

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“…Knowledge of the properties of aqueous solutions of hexafluorosilicate salts is essential to understand the interaction of aqueous solutions with minerals encountered in phosphate industry . This paper is a continuation of our research in phosphate aqueous solutions. , The main objectives of this study are to determine the thermodynamic properties of hexafluorosilicate salts X 2 SiF 6 –H 2 O with X = Na + , K + , or NH 4 + in aqueous solutions at a temperature of 353.15 K. The measurements of the water activity were performed using the hygrometric method, and the related properties were determined from dilution to saturated solution for Na 2 SiF 6 (aq), K 2 SiF 6 (aq), and (NH 4 ) 2 SiF 6 (aq).…”

Section: Introductionmentioning

confidence: 99%

Hexafluorosilicate Salts in Wet Phosphoric Acid Processes: Properties of X₂SiF₆–H₂O with X = Na⁺, K⁺, or NH₄⁺ in Aqueous Solutions at 353.15 K

2016

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During the production of phosphoric acid in wet processes, the acid and salts of fluorosilicates are formed in turn by inducing the problem of fouling. The knowledge of the physical−chemical properties of hexafluorosilicates allows a better understanding of process governing complex equilibria in the mixture. The literature indicates that significant deficiencies exist in the study of these salts. In this work, the thermodynamic properties of hexafluorosilicate salts X 2 SiF 6 −H 2 O with X = Na + , K + or NH 4+ were determined at temperature T = 353.15 K. The measurements of the water activity were performed from dilution to saturation of Na 2 SiF 6 (aq), K 2 SiF 6 (aq), and (NH 4 ) 2 SiF 6 (aq) using the hygrometric method. The osmotic coefficients were evaluated for these systems. From these measurements, the ion interaction parameters in binary solution were calculated at 353.15 K and used to predict the solute activity coefficients. The measurements of the binary systems were combined with reference pure water, Na 2 SiF 6 (s), K 2 SiF 6 (s) and (NH 4 ) 2 SiF 6 (s) solubility data to develop a chemical model that evaluates solute and solvent activities from dilute to saturated solution concentration at 353.15 K up to m max (Na 2 SiF 6 (s)) = 0.25 mol•kg −1 ; m max (K 2 SiF 6 (s)) = 0.30 mol•kg −1 ; and m max ((NH 4 ) 2 SiF 6 (s)) = 0.22 mol•kg −1 . The thermodynamic characteristics, solubility products (ln K sp °) and the standard molar Gibbs energy of dissolution ΔG diss °were also given. The solid phases obtained at saturated solution containing Na 2 SiF 6 , K 2 SiF 6 , or (NH 4 ) 2 SiF 6 were characterized by X-ray diffraction.

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Fluoride contents in commonly used commercial phosphate fertilizers and their potential risks in China

Li,

Ma,

Huang

et al. 2023

Environ Monit Assess

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Properties of fluoride in wet phosphoric acid processes: Fluorosilicic acid in an aqueous solution of H2SiF6–H20 at temperatures ranging from 298.15K to 353.15K

Cited by 13 publications

References 14 publications

Solubility of Mixed Ternary Systems of Hexafluoridosilicate Salts (M = Na⁺, K⁺, or NH₄⁺) in Hexafluoridosilicic Acid Aqueous Solutions at T = 353.15 K

Solubility of Mixed Ternary Systems of Hexafluoridosilicate Salts (M = Na⁺, K⁺, or NH₄⁺) in Hexafluoridosilicic Acid Aqueous Solutions at T = 353.15 K

Hexafluorosilicate Salts in Wet Phosphoric Acid Processes: Properties of X₂SiF₆–H₂O with X = Na⁺, K⁺, or NH₄⁺ in Aqueous Solutions at 353.15 K

Fluoride contents in commonly used commercial phosphate fertilizers and their potential risks in China

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Properties of fluoride in wet phosphoric acid processes: Fluorosilicic acid in an aqueous solution of H2SiF6–H20 at temperatures ranging from 298.15K to 353.15K

Cited by 13 publications

References 14 publications

Solubility of Mixed Ternary Systems of Hexafluoridosilicate Salts (M = Na+, K+, or NH4+) in Hexafluoridosilicic Acid Aqueous Solutions at T = 353.15 K

Solubility of Mixed Ternary Systems of Hexafluoridosilicate Salts (M = Na+, K+, or NH4+) in Hexafluoridosilicic Acid Aqueous Solutions at T = 353.15 K

Hexafluorosilicate Salts in Wet Phosphoric Acid Processes: Properties of X2SiF6–H2O with X = Na+, K+, or NH4+ in Aqueous Solutions at 353.15 K

Fluoride contents in commonly used commercial phosphate fertilizers and their potential risks in China

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Solubility of Mixed Ternary Systems of Hexafluoridosilicate Salts (M = Na⁺, K⁺, or NH₄⁺) in Hexafluoridosilicic Acid Aqueous Solutions at T = 353.15 K

Solubility of Mixed Ternary Systems of Hexafluoridosilicate Salts (M = Na⁺, K⁺, or NH₄⁺) in Hexafluoridosilicic Acid Aqueous Solutions at T = 353.15 K

Hexafluorosilicate Salts in Wet Phosphoric Acid Processes: Properties of X₂SiF₆–H₂O with X = Na⁺, K⁺, or NH₄⁺ in Aqueous Solutions at 353.15 K