KNO - American Chemical Society

Article pubs.acs.org/jced

Solid Liquid Equilibria Studies in the KVO3−KNO3−H2O System in the Temperature Range 293.15−323.15 K Adriana Wróbel, Sebastian Druzẏ ński,* and Urszula Kiełkowska Faculty of Chemistry, Nicolaus Copernicus University in Toruń, 7 Gagarin Street, 87-100 Toruń, Poland ABSTRACT: Mutual solubility of potassium metavanadate and potassium nitrate(V) was investigated in the KVO3−KNO3−H2O system at the temperature range 293.15−323.15 K. The equilibrium studies were conducted using isothermal saturation of a solution method. On the base of the received results, a fragment of the solubility polytherm for the investigated system was plotted. The knowledge of the course of that isotherm for the ternary system is necessary to plot the equilibrium diagram in a planar projection prepared according to the Jänecke method for the systems of exchange salts NH4NO3−KVO3−H2O and to determine optimal conditions for utilization of the postfiltration liquor from soda production with the soda−chlorine−saltpeter method. NH4VO3−H2O6 and NH4VO3−NH4NO3−H2O.7 Data for the KNO 3 −KVO 3 −H 2 O system and the four-component NH4NO3−KVO3−H2O do not exist.

1. INTRODUCTION Currently, the dominant way of sodium carbonate production is an energy-intensive and wasteful Solvay process.1 The soda− chlorine−saltpeter (SCS) method is an alternative approach to the Solvay process. It is based on the carbonization of the ammoniated brine of sodium nitrate(V) according to the eq 12

2. EXPERIMENTAL SECTION 2.1. Apparatus and Reagents. Hüber Polystat CC1 water thermostat with precision ±0.02 K was used in the studies. The set temperature was controlled using a mercury thermometer with a precision of ±0.1 K. In the studies, analytically pure reagents without further purification were used (Table 1). 2.2. Methods. Equilibrium studies in the KNO3−KVO3− H2O system were conducted at a temperature range of 293.15− 303.15 K. The choice of temperature range was dictated by the process conditions during the SCS method of soda production. During the equilibrium research on the studied system, methodology analogous to the one from the previously published papers was used.7−11 The solutions were prepared as follows: in an Erlenmeyer flask with a volume capacity of 100 cm3, the appropriate mass of potassium metavanadate, potassium nitrate(V), and deionized water were weighed, in such a way that one of salts was in excess relative to its solubility in water. Then, the samples were thermostated and constantly mixed with a magnetic stirrer for 20 h. The equilibration time between the solid and the liquid phase was determined experimentally for invariant points in the temperature range of 293.15−323.15 K. The concentrations of vanadate(V) and potassium ions were checked during the thermostatting time at appropriate intervals. The equilibration time was defined as the shortest time after which concentrations of analyzed ions were constant. In the next step, the samples were sedimented for 24 h, then a clear equilibrium

NaNO3 + NH3 + CO2 + H 2O ↔ NaHCO3 + NH4NO3 (1)

Contrary to the Solvay method, the SCS process is practically wasteless and has much lower energy demand.2 The SCS method has found no extensive use in industry due to the explosive properties of ammonium nitrate(V) which are particularly evident in the presence of reducing agents.3−5 The solution to the problem is to convert ammonium nitrate(V) into a compound with a lower explosive risk. According to eq 2, potassium nitrate with a higher stability than ammonium nitrate(V) is obtained by the double exchange of ammonium nitrate(V) with potassium metavanadate.3−5 NH4NO3 + KVO3 ↔ NH4VO3 + KNO3

(2)

In practice, after precipitation and filtration of sparingly soluble ammonium metavanadate, the resulting lye is subjected to the concentration and crystallization processes of salts for fertilizing. Figure 1 presents the chemical flow diagram for the process of ammonium nitrate(V) conversion to ammonium metavanadate. Selection of the optimal parameters for precipitation of ammonium metavanadate from the postfiltration liquor requires the precise knowledge of the equilibrium plot for the quaternary NH4NO3−KVO3−H2O salt system and four ternary subsystems: KVO3−KNO3−H2O, NH4VO3−NaVO3−H2O, KNO3−NH4NO3−H2O, and NH4NO3−NH4VO3−H2O. For mutual solubility for ternary systems on the 293.15− 323.15 K temperature range published data are incomplete. Satisfactory data were found only for the systems: KVO3− © XXXX American Chemical Society

Received: June 6, 2017 Accepted: September 14, 2017

A

DOI: 10.1021/acs.jced.7b00507 J. Chem. Eng. Data XXXX, XXX, XXX−XXX

Journal of Chemical & Engineering Data

Article

were performed with the SavantAA Sigma GBC. The relative standard deviation (RSD) of the analyses did not exceed 2%. The quantitative determination of vanadate(V) ions and solid phase analysis was carried out analogously to the previous works.7−11 Vanadate(V) ions in the acidic medium and in the presence of aqueous solution of H2O2, form the complex compounds V(O2)X3 and/or V(O2)X52−, where X is a monovalent anion. This reaction goes in the equimolar ratio according to eq 3.12 The relative standard deviation (RSD) of the analyses did not exceed 1%. (VO)2 (SO4 )3 + 2H 2O2 ↔ [(VO)2 )O2 ](SO4 )3 + 2H 2O (3)

Vanadates(V) were determined by the spectrophotometric method with 4-(2-pyridylazo)resorcinol (PAR) in solutions where the concentration of these ions was below 2 × 10−2 mol· dm−3. Vanadate(V) ions react with PAR in acetate buffer conditions at pH 5−6 and form a complex with the maximum absorbency at 540 nm.13 The RSD of the analyses did not exceed 1%. Solid phase analysis was performed by the XRD method. Diffractograms for selected sediment samples were recorded and compared to the standards included in the Powder Diffraction File.14

3. RESULTS AND DISCUSSION The comparison of the data available in literature with the obtained results in the present work of the binary systems Table 2. Comparison of Solubility Data Presented in This Work with the Literature Data for the Binary System KVO3− H2O reference

293.15 K

303.15 K

313.15 K

323.15 K

12.09 12.00 12.06

16.86 16.93 16.74

26.34 26.33 26.09

g·100g−1 H2O this work 6,15,16 17

Figure 1. Schematic diagram of conversion of ammonium nitrate into ammonium metavanadate.

Table 3. Comparison of Solubility Data Presented in This Work with the Literature Data for the Binary System KNO3−H2O

Table 1. Reagents Used in the Studies chemical name potassium metavanadate potassium nitrate(V) deionized water a

source Aldrich Avantor Performance Materials Poland

mole fraction purity 0.98

purification method

reference

none

0.06 μS·cm−1a

none

293.15 K g·100g

none

0.99

8.56 8.50 8.52

this work 18 19 20 21

Conductivity of water used in the studies.

−1

303.15 K

313.15 K

323.15 K

45.82 44.60 45.60 45.56 45.30

66.88 67.70 64.50 62.87 61.30

85.58

H2O

31.64 31.15 31.93 31.60

84.16

KVO3−H2O and KNO3−H2O in the temperature range 293.15 to 323.15 K is summarized in Tables 2 and 3. It is wellrecognized that the KVO3 solubility correlates consistently with the cited literature data.6,13−15 The differences between the obtained data and literature values for the KNO3−H2O system are noticeable.16−19 However, various literature sources give differing values. These discrepancies are the result of a very strong temperature dependence on the solubility of KNO3. Thus, the differences in the values are mainly caused by the sampling procedure of the equilibrated solutions or by the method of research.

solution was taken to the calibrated Ostwald pycnometer for density determination. After that, the content of the pycnometers was transferred quantitatively to 500 cm3 graduated flasks and filled with deionized water. Received solutions were used to determine the equilibrium concentrations of metawanadate and potassium nitrate(V). For experimental selected points, the solid phases were analyzed with the X-ray diffraction (XRD) method.7−11 2.3. Analytical Methods. The concentration of potassium ions in the equilibrated solutions was determined by flame atomic absorption spectrophotometry (FAAS). The analyses B



Article

Table 4. Solubility Data in the KVO3−KNO3−H2O System as a Function of Mole Fraction (x) and Density (d) at Temperature T and Pressure p = 0.1 MPaa m (mol·1000g H2O−1) no. T = 293.15 1 2 3 4 5 6 7 8 9 (E) 10 11 12 T = 303.15 1 2 3 4 5 6 7 8 9 10 11 12 13 (E) 14 15 T = 313.15 1 2 3 4 5 6 7 8 9 10 (E) 11 12 T = 323.15 1 2 3 4 5 6 7 8 (E) 9 10 11 a

d (g· cm−3)

KVO3

KNO3

x KVO3

solid phase composition

1.0604 1.0540 1.0501 1.0480 1.0477 1.0626 1.0849 1.1436 1.1679 1.1676 1.1671 1.1670

0.6199 0.5147 0.4449 0.3607 0.3080 0.1812 0.1142 0.0752 0.0739 0.0382 0.0244 0

0 0.0978 0.1613 0.2661 0.3821 0.8292 1.414 2.806 3.121 3.124 3.119 3.129

1 0.840 0.734 0.575 0.446 0.179 0.075 0.026 0.023 0.012 0.008 0

KVO3 KVO3 KVO3 KVO3 KVO3 KVO3 KVO3 KVO3 KVO3 + KNO3 KNO3 KNO3 KNO3

1.0816 1.0802 1.0775 1.0774 1.0838 1.1001 1.1087 1.1349 1.1578 1.1812 1.2007 1.2174 1.2226 1.2195 1.2171

0.8756 0.7633 0.5927 0.5056 0.3957 0.2408 0.1821 0.1501 0.1264 0.1049 0.0980 0.0873 0.0781 0.0434 0

0 0.1053 0.2615 0.3757 0.6645 1.383 1.724 2.411 2.754 3.509 3.737 4.115 4.555 4.525 4.532

1 0.879 0.694 0.574 0.373 0.148 0.096 0.059 0.044 0.029 0.026 0.021 0.017 0.010 0

KVO3 KVO3 KVO3 KVO3 KVO3 KVO3 KVO3 KVO3 KVO3 KVO3 KVO3 KVO3 KVO3 + KNO3 KNO3 KNO3

1.1110 1.1001 1.1039 1.1171 1.1328 1.1797 1.2058 1.2286 1.2515 1.2727 1.2718 1.2694

1.222 0.7260 0.5361 0.3793 0.2843 0.1801 0.1529 0.1265 0.1104 0.0829 0.0433 0

0 0.6655 1.199 1.782 2.280 3.586 4.324 4.820 5.536 6.598 6.610 6.615

1 0.522 0.309 0.176 0.111 0.048 0.034 0.026 0.020 0.012 0.007 0

KVO3 KVO3 KVO3 KVO3 KVO3 KVO3 KVO3 KVO3 KVO3 KVO3 + KNO3 KNO3 KNO3

1.1560 1.1406 1.1624 1.2178 1.2527 1.2874 1.3074 1.3298 1.3286 1.3259 1.3210

1.908 1.095 0.6786 0.2104 0.1472 0.1156 0.1069 0.0866 0.0563 0.0373 0

0 1.287 2.418 4.597 5.758 6.971 7.731 8.410 8.422 8.447 8.465

1 0.460 0.219 0.044 0.025 0.016 0.014 0.010 0.007 0.004 0

KVO3 KVO3 KVO3 KVO3 KVO3 KVO3 KVO3 KVO3 + KNO3 KNO3 KNO3 KNO3

K

K

Figure 2. Branches II of solubility isotherms for the solutions saturated with potassium metavanadate: black circle, 293.15 K; red square, 303.15 K; blue triangle, 313.15 K; green diamond, 323.15 K.

K

Figure 3. Branches I of solubility isotherms for the solutions saturated with potassium nitrate(V): black circle, 293.15 K; red square, 303.15 K; blue triangle, 313.15 K; green diamond, 323.15 K

K

The results of the equilibrium studies for the KVO3−KNO3− H 2 O system were summarized in Table 4. The salt concentration, the density of equilibrium solutions, mole fractions of salts calculated without taking into consideration a solvent, and the solid phase composition in the equilibrium with solutions have been tabulated. Equilibrium concentrations of salts were used to plot a fragment of the mutual solubility polytherm for the KVO3− KNO3−H2O system (Figures 2 and 3). The presented solubility isotherms for 293.15, 303.15, 313.15, and 323.15 K have two branches. One of isotherms parts denoted (I) represents the solutions saturated with KNO3. The second

u(T) = 0.02 K; u(p) = 5 kPa; u(ρ) = 0.0018 g·cm−3; ur(m) = 0.02. C



Article

Figure 4. Density of equilibrium solutions for branches II of solubility isotherms for the solutions saturated with potassium metavanadate: black circle, 293.15 K; red square, 303.15 K; blue triangle, 313.15 K; green diamond, 323.15K

Figure 6. Diffractograms for the solid phase (A) for pure KNO3; (B) for pure KVO3; (C) for branches I, saturated with KNO3; (D) for branches II, saturated with KVO3; (E) for eutonic point at 293.15 K; (F) for eutonic point at 303.15 K; (G) for eutonic point at 313.15 K; (H) for eutonic point at 323.15 K. ●, KVO3; ■, KNO3.

However, branches II corresponding to the solutions saturated with potassium metavanadate have hyperbolic character. The specific course of these branches is caused by the strong salting out effect of KNO3 on KVO3. The increasing concentration of the potassium nitrate reduces the rate of dissolution of potassium metavanadate, which reduces the rate of the conversion reaction. The salting out effect decreases with the rise of temperature. For high temperatures, the rapid increase of the KVO3 concentration occurs at high concentrations of KNO3. During equilibrium studies over ternary systems it is possible to create new solid phases. To find out if a new solid phase appears in a given system, graphs of property-composition type are helpful. If in the system additional solid phases are created there are two or more invariant points in the isotherms.7−11 Figures 4 and 5 show density dependence of the equilibrium solutions from the KVO3 mole fraction. The branches of isotherms are presented separately, as with the fragment of polytherm of the mutual solubility. The course of the curves in Figures 4 and 5 shows that no complex salts or salt hydrates are formed in the studied system. The confirmation of this conclusion are XRD patterns Figure 6, where no reflections corresponding to a new solid phase have been observed. The mole fraction of salts, without taking a solvent into consideration, were calculated according to the following equations

Figure 5. Density of equilibrium solutions for branches I for branches of solubility isotherms for the solutions saturated with potassium nitrate(V): black circle, 293.15 K; red square, 303.15 K; blue triangle, 313.15 K; green diamond, 323.15 K.

branches of isotherms marked (II) corresponding to solutions saturated with KVO3. Figures 2 and 3 also show the invariant points (eutonic points) corresponding to saturated solutions of both salts (mark E). The solubility of potassium metavanadate in saturated solutions of potassium nitrate(V) is very small (max. 0.087 mol·1000g H2O1− at 323.15 K) which makes the branches (I) isotherms very short. For better readability of the course of these isotherms, these are shown separately in Figure 3. The course of branches I of the solubility isotherms for the investigated temperatures is linear (Figure 3) and the concentration of potassium nitrate(V) is almost constant.

XKVO3 = D

[KVO3] , [KVO3] + [KNO3]

XKNO3 =

[KNO3] [KVO3] + [KNO3]



Article

(16) Trypuć, M.; Białowicz, K.; Mazurek, K. Solubility in the KVO3 − KCl − H2O system from 293 to 323K. Ind. Eng. Chem. Res. 2002, 41, 4174−4177. (17) Trypuć, M.; Kiełkowska, U. Solubility diagram for the system KHCO3 + KVO3 + H2O at 293 − 323K. Fluid Phase Equilib. 2003, 213, 81−88. (18) Korin, E.; Soifer, L. Phase diagram for the system K2Cr2O7 + KNO3 + H2O in the temperature range 10°C to 40°C. J. Chem. Eng. Data 1997, 42, 508−510. (19) Mullin, J. W. Crystallization; Butterworth: London, 1993. (20) Söhnel, O.; Novotny, P. Densities of aqueous solutions of inorganic substances; Elsevier: Amsterdam, 1985. (21) Speight, J. G. Lange’s handbook of chemistry; McGraw-Hill, Inc: New York, 2005.

4. CONCLUSIONS On the basis of the results, the polytherm of the mutual solubility of the KVO3−KNO3−H2O ternary system was plotted. A strong salting-out effect of potassium nitrate(V) on potassium metavanadate was observed. Moreover, the potassium metavanadate is sparingly soluble in the saturated solutions of potassium nitrate(V). Furthermore, the formation of complex salts or hydrates was not observed. Investigations of the salt solubility in the KVO3−KNO3− H2O system are necessary for further research on possible utilization of the postfiltration liquor from the SCS method. The obtained data will allow for planning further studies in the quaternary KVO3−KNO3−NH4VO3−NH4NO3−H2O system to construct the equilibrium plot in the planar projection according to Jänecke, which is the basis for determination of the optimal conditions for the reaction described by eq 2.

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. ORCID

Sebastian Drużyński: 0000-0002-8762-2528 Notes

The authors declare no competing financial interest.

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REFERENCES

(1) Niederliński, A.; Bukowski, A.; Koneczny, H. Soda and accompanying products; WNT: Warsaw, 1978. (2) Pischinger, E. Research on the new method of soda production; Nicolaus Copernicus University in Toruń Press: Toruń, 1969. (3) Bobrownicki, W.; Biskupski, A.; Kołaczkowski, A. On the thermal decomposition of ammonium-sodium nitrate. Applied Chemistry 1977, 21, 3−18. (4) Kołaczkowski, A. Spontaneous decomposition of ammonium nitrate; Scientific papers Institute of Inorganic Technology and Mineral Fertilizers, Wrocław Technical University Press: Wrocław, 1980. (5) Trypuć, M.; Drużyński, S. Optimum conditions of ammonium metavanadate precipitation from the post − filtration lye from the sodium nitrate − based production of soda ash. Przemysl Chemiczny 2009, 88, 722−727. (6) Trypuć, M.; Stefanowicz, D. I. Solubility in the KVO3 + NH4VO3 + H2O system. J. Chem. Eng. 1997, 42, 1140−1144. (7) Trypuć, M.; Drużyński, S. Investigation of mutual solubility in the NH4VO3 − NH4NO3 − H2O system. Ind. Eng. Chem. Res. 2009, 48, 5058−5063. (8) Trypuć, M.; Drużyński, S. Investigation of the solubility in the NaVO3 − NaNO3 − H2O system. Ind. Eng. Chem. Res. 2007, 46, 2688−2692. (9) Trypuć, M.; Drużyński, S. Solubility in the NaNO3 + NH4NO3 + H2O system. Ind. Eng. Chem. Res. 2008, 47, 3767−3770. (10) Trypuć, M.; Drużyński, S.; Kiełkowska, U.; Mazurek, K. Utilization of the post-filtration lye from the SCS method of soda production. Pol. J. Chem. Technol. 2007, 9, 59−62. (11) Trypuć, M.; Kiełkowska, U. Solubility in the NH4HCO3 + NaHCO3 + H2O System. J. Chem. Eng. Data 1998, 43, 201−204. (12) Williams, W. J. Handbook of anion determination; Butterworth and Co Ltd: London, 1979. (13) Sandell, E. B. Colorimetric Determination of Traces of Metals, 3rd ed.; Interscience: New York, 1959. (14) Powder Diffraction File; International Center for Diffraction Data: Newtown Square, PA, 2001. (15) Mazurek, K. Investigations on the solubility in the KVO3 + K2SO4 + H2O system from 293.15 K to 323.15K. J. Chem. Eng. Data 2013, 58, 980−985. E


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