Solubility of Sodium Chromate in the NaOH–CH3OH–H2O System

Article pubs.acs.org/jced

Solubility of Sodium Chromate in the NaOH−CH3OH−H2O System from (278.15 to 343.15) K Shi-hui Tang,†,‡,§ Li-li Pei,*,†,‡ Ying Tian,†,‡ Xue-kui Wang,§ Zuo-liang Sha,§ Yi-ying Gao,†,‡ Hong-bin Xu,†,‡ and Yi Zhang†,‡ †

Key Laboratory of Green Process and Engineering and ‡National Engineering Laboratory for Hydrometallurgical Cleaner Production Technology, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, China § College of Marine Science and Engineering, Tianjin University of Science & Technology, Tianjin 300457, China ABSTRACT: The solubility of sodium chromate in the NaOH−CH3OH−H2O system have been measured using the static analytical method at temperatures of (303.15, 313.15, 323.15, and 333.15) K. The measured results were respectively correlated by the Apelblat equation, the empirical equation, and the λ−h equation. Meanwhile, it was found that the liquid−liquid phase separation, also termed as oiling out, will happen under certain conditions. The relationship between the steady-state critical temperature and solvent composition was studied systematically using FBRM. The results show that the solubility of sodium chromate increases with increasing temperature and decreases with increasing concentration of sodium hydroxide, respectively. Three models were employed to correlate the experimental data, which fit the data well. Moreover, the Apelblat equation for the system has less deviations than the λ−h equation and the empirical equation. The results also show that the steady state critical oiling-out temperature increases with the increase of methanol mass fraction.

■

INTRODUCTION Methanol (CH3OH) is usually used as an efficient agent to extract sodium hydroxide (NaOH) or potassium hydroxide (KOH) from their solid mixture or aqueous mixed solution.1,2 Kashiwase et al.3 introduced the methanol leaching method into the separation of NaOH from the solid mixture of NaOH, sodium chromate (Na2CrO4), and chromite or eprocessing residue (COPR), where in the content of NaOH is above 60 % by weight. Xu et al.4 proposed a similar process for separating NaOH from the aqueous solid mixture of NaOH−Na2CrO4 and COPR, where in the content of NaOH is below 10 % by weight. In both processes, Na2CrO4 is the target product, and NaOH, however, is the reaction medium. The solubility data of Na2CrO4 in either the NaOH−CH3OH binary system or the NaOH−CH3OH−H2O ternary system becomes imperative. A higher Na2CrO4 solubility will undoubtedly lead to a lower recovery of chromium. In this paper, the solubility of Na2CrO4 in the NaOH− CH3OH−H2O system have been measured using the static analytical method5 at temperatures of (303.15, 313.15, 323.15, and 333.15) K. The measured results were respectively correlated by the Apelblat equation, the empirical equation, and the λ−h equation. Meanwhile, it was found that the liquid−liquid phase separation, also termed as oiling out, will happen under certain conditions. The relationship between the steady-state critical temperature and solvent composition was studied systematically using FBRM.6,7

than 99.5 % and was purchased from Sinopharm Chemical Reagent Co., Ltd. of China. The sodium chromate used in this work was of analytical grade with mass fraction purity higher than 99.0 % and was purchased from Sinopharm Chemical Reagent Co., Ltd. of China. The sodium chromate was previously dried in vacuum at 80 °C for 24 h and stored in a desiccator. The deionized water used throughout this work was obtained from a Millipore filter system. The sodium hydroxide used in this work was of analytical grade with mass fraction purity higher than 99.0 % and was purchased from Beijing Chemical Co., Ltd. of China. The masses of the samples and solvents were determined by an analytical balance (Mettler Toledo AB204-N, Switzerland) with an accuracy of 0.0001 g. An HZQ-type thermostatic vibrator with temperature control (precision of 0.1 °C) was used to ensure the samples at an equilibrium state. The contents of the sodium chromium in all samples were determined by an inductively coupled plasma/optical emission spectrometry (ICP-OES, Optima 5300DV, PerkinElmer), and the content of sodium hydroxide was determined by titration using hydrochloric acid solution with phenolphthalein solution as the indicators. Experimental Method. Predetermined amounts of sodium hydroxide and sodium chromate were mixed homogeneously in a given amount of aqueous methanol before putting into sealed polyethylene bottles. Then the bottles were placed in the

EXPERIMENTAL SECTION Reagents and Apparatus. The methanol used in this work was of analytical grade with mass fraction purity higher

Received: October 22, 2014 Accepted: April 21, 2015 Published: May 11, 2015

■

© 2015 American Chemical Society

1584

DOI: 10.1021/je5010356 J. Chem. Eng. Data 2015, 60, 1584−1591

Journal of Chemical & Engineering Data

Article

Table 1. Solubility of Sodium Chromate in the NaOH−CH3OH−H2O System at Pressure p = 101.3 KPaa Apelblat equation

empirical equation

λ−h equation

xcal·10

xcal·10

xcal·10

6.7066 7.2929 7.8419 8.3535 6.7811 8.0060 9.7213 11.9000 10.3000 12.4000 15.2000 18.7000 15.7000 20.0000 24.4000 28.9000 21.7000 28.0000 35.3000 43.5000 41.6000 50.8000 62.0000 75.3000

0.0202 0.0442 0.0814 0.1320 0.1667 0.2044 0.2505 0.3049 0.6513 0.7919 0.9625 1.1631 1.1125 1.3811 1.7477 2.0175 4.0764 5.0158 6.0180 7.0830 8.6729 14.5000 22.5000 31.3000 38.7000 47.1000 59.8000 76.8000 83.8000 115.5000

ωB/%

T/K

100

303.15 313.15 323.15 333.15 303.15 313.15 323.15 333.15 303.15 313.15 323.15 333.15 303.15 313.15 323.15 333.15 303.15 313.15 323.15 333.15 303.15 313.15 323.15 333.15 303.15 313.15 323.15 333.15

6.7011 7.3094 7.8253 8.3590 6.7756 8.0222 9.7050 11.9323 10.3062 12.2388 15.3294 18.6609 15.6475 20.1251 24.2162 28.9244 21.8404 27.4965 35.8140 43.3071 41.7494 50.2697 62.5603 75.1362

6.7059 7.2930 7.8437 8.3522 6.7748 8.0253 9.7011 11.9340 10.2678 12.3831 15.1432 18.7402 15.6879 19.9634 24.4207 28.8402 21.7278 27.9453 35.2142 43.5618 41.6158 50.7763 61.9093 75.4093

303.15 313.15 323.15 333.15 303.15 313.15 323.15 333.15 303.15 313.15 323.15 333.15 303.15 313.15 323.15 333.15 303.15 313.15 323.15 333.15 303.15 313.15 323.15 333.15 303.15 313.15 323.15 333.15 303.15 313.15

0.0203 0.0440 0.0816 0.1319 0.1656 0.2075 0.2473 0.3059 0.6507 0.7937 0.9606 1.1637 1.1048 1.4042 1.7777 2.0252 4.0661 5.0467 5.9871 7.0933 8.8177 14.4244 22.9628 29.0453 38.5126 47.6191 59.2757 76.9764 84.1722 114.4270

0.0203 0.0440 0.0816 0.1319 0.1663 0.2049 0.2506 0.3045 0.6510 0.7927 0.9619 1.1632 1.1101 1.3833 1.7485 2.0143 4.0740 5.0162 6.0250 7.0778 8.7587 14.7308 22.4650 31.4029 38.5833 47.3464 59.6319 76.8166 83.9189 115.5127

x·10

4

4

4

Apelblat equation

empirical equation

λ−h equation

x·10

xcal·10

xcal·10

xcal·104

6.7236 7.2647 7.8202 8.3862 6.7131 8.1586 9.8061 11.6564 10.1966 12.5520 15.2696 18.3565 15.7881 19.6750 24.2116 29.4209 21.7730 27.8503 35.1220 43.6679 41.4910 51.0789 62.1314 74.6730

0.0880 0.1291 0.1665 0.2206 0.2832 0.3216 0.3540 0.3991 1.0900 1.3051 1.5803 1.9115 1.8862 3.3763 5.8870 8.5701 4.8821 6.0101 7.6174 9.2369 21.3891 31.4017 43.5884 56.4700 63.6489 75.1713 87.3596 105.5499

0.0886 0.1263 0.1704 0.2188 0.2839 0.3190 0.3570 0.3979 1.0894 1.3073 1.5776 1.9127 1.8716 3.4596 5.7392 8.6461 4.8652 6.0756 7.5318 9.2732 21.3688 31.4947 43.4539 56.5305 63.8183 74.5478 88.1218 105.2323

0.0204 0.0419 0.0827 0.1563 0.1659 0.2054 0.2511 0.3034 0.6493 0.7960 0.9646 1.1555 1.1120 1.3755 1.7220 2.0296 4.0874 4.9793 5.9982 7.1450 8.8621 14.2105 22.1737 33.6652 38.1748 48.3440 60.3887 74.4068 94.7759 125.4386

0.0109 0.0301 0.0591 0.1009 0.0833 0.1157 0.1545 0.1948 0.1920 0.3449 0.5719 0.8445 0.2902 0.5895 1.0498 1.5083 0.4358 1.2107 2.2637 3.9867 5.1107 7.5288 10.4007 13.2471 28.8841 35.1166 41.3680 50.4782 67.4558 87.3676

4

4

4

ωC = 0

95

90

85

80

70

60

ωB = 5 %

ωC = 10 % 100

95

90

85

80

70

60

50

4

1585

0.0890 0.1261 0.1696 0.2196 0.2841 0.3188 0.3568 0.3981 1.0898 1.3057 1.5797 1.9117 1.8438 3.3860 5.7598 8.6125 4.8587 6.0802 7.5473 9.2603 21.3000 31.6000 43.4000 56.5000 63.9000 74.4000 88.2000 105.3000 ωC = 20 % 0.0110 0.0110 0.0293 0.0297 0.0607 0.0596 0.1000 0.1008 0.0832 0.0830 0.1161 0.1164 0.1539 0.1537 0.1951 0.1951 0.1916 0.1906 0.3473 0.3492 0.5678 0.5676 0.8466 0.8459 0.2905 0.2838 0.5990 0.6142 1.0323 1.0251 1.5171 1.5165 0.4421 0.4554 1.1570 1.1519 2.3733 2.3225 3.9218 3.9671 5.1046 5.0868 7.5570 7.6007 10.3602 10.3000 13.2650 13.3000 28.9755 29.0000 34.7712 34.7000 41.7964 41.8000 50.2978 50.3000 67.2099 67.0000 88.3733 88.7000

0.0890 0.1239 0.1691 0.2266 0.2836 0.3194 0.3573 0.3973 1.0840 1.3188 1.5867 1.8880 1.8927 3.3333 5.6830 9.3793 4.8590 6.0933 7.5430 9.2178 21.5437 30.7510 42.9945 58.8781 63.3720 75.4053 88.8302 103.6036 0.0110 0.0275 0.0655 0.1481 0.0838 0.1140 0.1525 0.2005 0.1932 0.3355 0.5646 0.9207 0.2945 0.5612 1.0308 1.8246 0.4395 1.0927 2.5785 5.7753 5.1579 7.3342 10.2201 13.9568 28.8530 35.0013 41.9925 49.8259 67.7176 86.9848

DOI: 10.1021/je5010356 J. Chem. Eng. Data 2015, 60, 1584−1591

Journal of Chemical & Engineering Data

Article

Table 1. continued ωB/%

40

a

Apelblat equation

empirical equation

λ−h equation

xcal·10

xcal·10

xcal·10

150.7307 208.8456 180.3252 248.9663 336.6445 445.6771

4

T/K

x·10

323.15 333.15 303.15 313.15 323.15 333.15

157.4311 205.9164 180.5270 249.3776 331.7276 453.7391

4

155.8884 206.6219 181.0821 246.9882 335.0737 452.1619

4

4

ωC = 10 % 156.3000 206.3000 181.8000 240.8000 335.7000 452.4000

Apelblat equation

empirical equation

λ−h equation

x·10

xcal·10

xcal·10

xcal·104

112.4950 133.8448 124.3604 171.3403 219.0120 293.7585

111.1600 134.4013 125.0734 168.3004 223.1402 291.8589

4

4

4

ωC = 20 % 111.1000 134.3000 125.7000 167.4000 223.0000 292.4000

110.0942 137.2946 124.7628 168.5973 223.6305 291.1134

Standard uncertainties u are u(T) = 0.5 K, u(ρ) = 5 KPa (ambient pressure change), and u(x) = 0.01.

■

RESULTS AND DISCUSSION The solubility data of sodium chromate in the NaOH−CH3OH− H2O system at temperatures of (303.15, 313.15, 323.15, and 333.15) K are presented in Table 1. The solubility data in the NaOH−CH3OH−H2O system are described by the modified Apelblat equation,9−12 the Empirical equation,13 and the λ−h equation14,15 as illustrated in eqs 4 through 6, respectively.

thermostatic vibrator and kept shaking. The experiments were carried out at ambient pressure and four specific temperatures including 30 °C, 40 °C, 50 °C, and 60 °C. The liquid phase of each sample was examined every 48 h, and an equilibrium state was believed to be achieved when the liquid-phase components became stable. After equilibrium was attained, the shaking was discontinued, and then the samples were allowed to settle for 24 h before further treatment and analysis. Each sample, about 5 mL of organic phase was filtered, weighed, and diluted into a 100 mL volumetric flask. The determination of the sodium chromate content in the solution was analyzed using ICP-OES. The content of sodium hydroxide was determined by titration using hydrochloric acid solution with phenolphthalein solution as the indicators. The equilibrium solid phase was dried in a desiccator at room temperature and then analyzed by an XRD analyzer. All the measurements were repeated three times. The mole fraction solubility is given by8 xA =

ln x = A1 +

+

mB MB

+

mC MC

+

mD MD

The mass fraction of the CH3OH is given by mB ωB = mB + mD The mass fraction of the NaOH is given by mC ωC = mB + mC + mD

(4)

x = A 2 T 2 + B2 T + C 2

(5)

⎛1 ⎡ λ(1 − x) ⎤ 1 ⎞ ln⎢1 + ⎟ ⎥ = λh⎜ − ⎣ ⎦ x Tm ⎠ ⎝T

(6)

wherein x is the mole fraction solubility of sodium chromate; T is the absolute temperature; and A, B, C, λ, and h are the parameters. The calculated solubility values of sodium chromate xcal are also given in Table 1. The values of parameters A, B, and C are listed in Table 2 together with the root-mean-square deviations (RMSDs) as defined in eq 7.

mA MA mA MA

B1 + C1 ln T T

(1)

⎡1 RSMD = ⎢ ⎢⎣ N

(2)

N

∑ (xi − i=1

⎤1/2

xical)2 ⎥ ⎥⎦

(7)

wherein N is the number of experimental points, xi represents the solubility calculated from eqs 4−6, and xical represents the experimental solubility values. The relative deviations between the experimental value and calculated value are also listed in Table 1. The relative average deviations (ARD), as defined in eq 8, by eqs 4−6 are listed in Table 2.

(3)

wherein mA, mB, mC, and mD represent the mass of solute, methanol, sodium hydroxide, and water, respectively. MA, MB, MC, and MD are the molecular weight of solute, methanol, sodium hydroxide, and water, respectively. Each solubility data point was determined three times. The uncertainty of the experimental data is about 0.5 %. For the determination of the dependence of critical oilingout point on solvent composition, a 100 mL glass crystallizer with a heating and/or cooling jacket was used. Suspended solutions of sodium chromate with different solvent compositions were held at a lower temperature and then heated slowly at a rate of 0.1 °C·min−1 under stirring with a magnetic stirrer at 500 rpm until the oiling-out occurred. The temperature at which the oiling-out happened was defined as the critical temperature of the oiling-out at this solvent composition. To determine the critical temperature accurately, an isothermal method was also adopted with a step of 0.1 °C; the suspension was held constant around the temperature determined above for a few hours and then kept in quiescent to visually observe whether the phase separation happened.

ARD =

1 N

N

∑ i=1

xi − xical ·100 xi

(8)

The samples are characterized by XRD, and it is shown in Figure 1. It could be seen that the solid phase is sodium chromate. All of the values of the correlation coefficient R2 obtained with the Apelblat equations and the experience polynomial equation were above 0.99, with the average relative error (ARD) less than 4 %. The maximum root-mean-square deviation (105 RSMD) of the Apelblat equations and the experience polynomial equationare separately 27.56 and 48.16. However, all of the values of the correlation coefficient R2 obtained with the λ−h equations were just above 0.91, with the average relative error (ARD) less than 18 % and the maximum rootmean-square deviation (105 RSMD) was 84.73. Based on these 1586

DOI: 10.1021/je5010356 J. Chem. Eng. Data 2015, 60, 1584−1591

A1

35.8837 −211.2776 −174.6797 168.4207 35.0240 −78.3230

224.8391 −26.9906 −118.7964 488.6913 −44.4766 292.0068 −146.6018

742.6590 −42.7386 −62.3628 278.7659 79.9001 456.5644 −262.6946 5.2585 −88.4281

1355.2043 204.5561 460.6012 929.1240 1273.5567 362.5852 −88.3682 190.2644 −19.4294

ωB/%

1 0.95 0.9 0.85 0.8 0.7

1 0.95 0.9 0.85 0.8 0.7 0.6

1 0.95 0.9 0.85 0.8 0.7 0.6 0.5 0.4

1 0.95 0.9 0.85 0.8 0.7 0.6 0.5 0.4

C1

−6.0266 31.0948 25.8024 −24.8614 −4.9444 11.7481

−33.4857 2.9975 17.1428 −71.0248 6.5085 −42.4941 21.7536

−108.6899 5.6864 8.7500 −41.5596 −12.0630 −66.4619 39.1568 −0.0049 13.9865

−198.8099 −30.5805 −67.2811 −136.2309 −186.2342 −53.1725 13.1096 −27.7384 3.6169

B1

−2653.6335 7972.1185 6171.3712 −9947.7047 −3912.2522 1730.9153

−13680.6159 −184.1520 3551.0719 −27714.8748 −103.8429 −16774.5356 5226.9914

−40830.6922 −230.1344 825.6801 −15279.0238 −5691.5895 −25411.9972 10121.1009 −3034.8843 1362.5857

−70598.3413 −12583.5769 −26375.3591 −48842.2744 −66510.7360 −20106.6610 2307.9568 −11144.8782 −1703.6611

R2

1587

0.9983 0.9998 0.9997 0.9988 0.9947 0.9998 0.9960 0.9966 0.9944

1.0000 0.9945 0.9999 0.9919 0.9985 0.9966 0.9991 0.9986 0.9986

0.9925 0.9927 0.9999 0.9968 0.9965 0.9999 0.9965

0.9999 1.0000 0.9953 0.9978 0.9932 0.9964

Apelblat equation

0.0100 0.0037 0.0260 0.1092 0.6917 0.2644 2.9315 8.8940 27.5683

0.0001 0.0224 0.0088 0.1894 0.2585 12.1485 2.4071 10.1492 22.1930

0.0259 0.0211 0.0186 0.9328 0.5750 0.87777 5.2426

0.1298 0.0266 1.2572 1.3847 3.9962 4.3956

105RSMD

1.7768 0.2926 0.5969 1.4612 3.1195 0.3339 0.7644 0.9229 1.2198

0.1194 0.8746 0.2081 1.0863 0.5799 3.3153 0.4664 0.7199 0.8613

1.5792 0.5677 0.3071 1.7475 0.9838 0.2683 0.5673

0.1558 0.1195 0.8622 0.6782 1.1286 0.6829

ARD %

0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000

0.0000 0.0000 0.0000 0.0000 0.0000 −1.1996 0.0000 0.0000 0.0000

0.0000 0.0000 0.0000 0.0000 0.0000 7.17·10−7 0.0000

0.0000 0.0000 0.0000 −0.2471 0.0000 0.0000

A2 ωC = 0 0.0000 −0.0001 −0.0002 7.9346 −0.0002 −0.0005 ωC = 5 % 0.0000 0.0000 0.0000 −0.0002 −0.0001 −3.39·10−4 −0.0009 ωC = 10 % 0.0000 0.0000 0.0000 0.0000 0.0000 49.9515 −0.0012 −0.0025 −0.0076 ωC = 20 % 0.0000 0.0000 0.0000 0.0000 −0.0001 0.0000 −0.0004 0.0000 −0.0039

B2

0.0005 0.0001 0.0024 0.0029 0.0204 0.0031 0.0540 −0.0250 0.5451

0.0006 0.0003 0.0011 −0.0022 0.0005 0.1813 0.1824 0.3449 1.0870

0.0002 0.0001 0.0022 0.0235 0.0085 0.03897 0.1329

−0.0029 0.0202 0.0278 0.0389 0.0265 0.0725

C2

0.9997 0.9995 0.9995 0.9952 0.9968 0.9991 0.9953 0.9952 0.9933

1.0000 0.9939 0.9998 0.9879 0.9987 0.9950 0.9978 0.9991 0.9975

0.9933 0.9926 1.0000 0.9958 0.9970 0.9995 0.9956

0.9988 0.9999 0.9969 0.9984 0.9931 0.9971

R2

empirical equation

0.0034 0.0055 0.0317 0.1841 0.4382 0.6835 3.1835 10.1691 29.6102

0.0013 0.0233 0.0138 0.1969 0.2303 11.5375 3.9069 8.2405 48.1583

0.0230 0.0211 0.0046 0.7052 0.5222 1.4461 5.9723

0.1231 0.2000 1.0520 1.1488 3.7904 4.0133

105RSMD

Table 2. Parameters in the Different Equations for the Na2CrO4 Solubility in the NaOH−CH3OH−H2O System

0.9533 0.3836 0.7207 2.4777 3.1105 0.6979 0.7462 0.9452 1.4151

0.2347 0.9335 0.1440 1.1019 0.3817 2.9861 0.6725 0.5712 1.4093

1.4721 0.5632 0.0293 1.2984 0.7041 0.3833 0.6549

0.1463 0.1801 0.6076 0.4501 1.0887 0.6316

ARD %

0.0000 7.3894 0.0015 0.0001 0.0000 0.0304 0.7993 0.0532 0.0054

0.0001 75.0279 25.9655 7.7610 5.0304 0.0004 0.1525 0.0143 0.0017

3.5139 964.9636 19.8292 0.0001 1.6864 0.0063 0.6605

199.2056 3.2962 1.4387 0.6266 0.1979 0.3437

λ

8765.3289 2937.5783 5257.2492 6140.4102 8672.7163 3353.9635 1840.5924 2401.7663 2909.2939

6852.2256 2028.0420 1936.2273 2138.8172 1876.0694 4501.5501 2257.0774 2698.2190 3138.1587

3144.3874 1099.0487 1862.7166 5390.5655 2154.5628 3397.1498 1659.4047

647.3716 1853.7737 1978.0577 2097.1837 2348.8015 1985.6409

h

0.9919 0.9975 0.9973 0.9932 0.9902 0.9942 0.9974 0.9963 0.9976

0.9962 0.9975 0.9995 0.9893 0.9977 0.9965 0.9925 0.9101 0.9991

0.9917 0.9965 0.9975 0.9978 0.9977 0.9965 0.9947

0.9961 0.9923 0.9913 0.9941 0.9970 0.9966

R2

λ−h equation

0.2384 0.0311 0.3859 1.5907 9.0992 3.7961 4.5544 21.1426 30.0055

0.1225 0.0252 0.0474 0.3160 0.4413 23.4595 14.5612 84.7299 47.2708

0.0424 0.0223 0.1431 4.1786 0.5777 12.8441 12.3311

0.2861 1.6496 2.2714 3.4239 4.2978 5.2914

105RSMD

16.7469 1.5373 3.4048 7.1078 17.3446 2.6506 0.8095 1.3845 1.2334

6.2781 0.8943 0.4049 1.5109 0.6931 5.3321 1.9038 6.9748 0.8839

2.3925 0.5655 0.8091 3.6316 0.7598 2.1055 1.0684

0.3349 1.4939 1.4111 1.2176 1.0902 0.8826

ARD%

Journal of Chemical & Engineering Data Article

DOI: 10.1021/je5010356 J. Chem. Eng. Data 2015, 60, 1584−1591

Journal of Chemical & Engineering Data

Article

Figure 4. Experimental results fitted by the Apelblat equation at ωC = 10 %. □, ωB = 100 %; ○, ωB = 95 %; △, ωB = 90 %; ▽, ωB = 85 %; ■, ωB = 80 %; ●, ωB = 70 %; ▲, ωB = 60 %; ▼, ωB = 50 %; ☆, ωB = 40 %.

Figure 1. XRD pattern of the solid phase of the NaOH−CH3OH− Na2CrO4−H2O system at (30 to 60) °C.

Figure 2. Experimental results fitted by the Apelblat equation at ωC = 0. □, ωB = 100 %; ○, ωB = 95 %; △, ωB = 90 %; ▽, ωB = 85 %; ■, ωB = 80 %; ●, ωB = 70 %.

Figure 5. Experimental results fitted by the Apelblat equation at ωC = 20 %. □, ωB = 100 %; ○, ωB = 95 %; △, ωB = 90 %; ▽, ωB = 85 %; ■, ωB = 80 %; ●, ωB = 70 %; ▲, ωB = 60 %; ▼, ωB = 50 %; ☆, ωB = 40 %.

Figure 3. Experimental results fitted by the Apelblat equation at ωC = 5 %. □, ωB = 100 %; ○, ωB = 95 %; △, ωB = 90 %; ▽, ωB = 85 %; ■, ωB = 80 %; ●, ωB = 70 %; ▲, ωB = 60 %.

Figure 6. Experimental results fitted by the empirical equation at ωC = 0. □, ωB = 100 %; ○, ωB = 95 %; △, ωB = 90 %; ▽, ωB = 85 %; ■, ωB = 80 %; ●, ωB = 70 %.

results, the best results were obtained when fitted with the Apelblat equation. Therefore, the Apelblat equation was most suitable for the investigated system within the temperature range in this paper. Figures 2 through 13 showed more straightforward results of the individual equations.

The comparison of the calculated results by fitting with the Apelblat equation and the experimental results is given in Figures 14 through 17. The results show that solubility of 1588

DOI: 10.1021/je5010356 J. Chem. Eng. Data 2015, 60, 1584−1591

Journal of Chemical & Engineering Data

Article

Figure 7. Experimental results fitted by the empirical equation at ωC = 5 %. □, ωB = 100 %; ○, ωB = 95 %; △, ωB = 90 %; ▽, ωB = 85 %; ■, ωB = 80 %; ●, ωB = 70 %; ▲, ωB = 60 %.

Figure 10. Experimental results fitted by the λ−h equation at ωC = 0. □, ωB = 100 %; ○, ωB = 95 %; △, ωB = 90 %; ▽, ωB = 85 %; ■, ωB = 80 %; ●, ωB = 70 %.

Figure 8. Experimental results fitted by the empirical equation at ωC = 10 %. □, ωB = 100 %; ○, ωB = 95 %; △, ωB = 90 %; ▽, ωB = 85 %; ■, ωB = 80 %; ●, ωB = 70 %; ▲, ωB = 60 %; ▼, ωB = 50 %; ☆, ωB = 40 %.

Figure 11. Experimental results fitted by the λ−h equation at ωC = 5 %. □, ωB = 100 %; ○, ωB = 95 %; △, ωB = 90 %; ▽, ωB = 85 %; ■, ωB = 80 %; ●, ωB = 70 %; ▲, ωB = 60 %.

Figure 12. Experimental results fitted by the λ−h equation at ωC = 10 %. □, ωB = 100 %; ○, ωB = 95 %; △, ωB = 90 %; ▽, ωB = 85 %; ■, ωB = 80 %; ●, ωB = 70 %; ▲, ωB = 60 %; ▼, ωB = 50 %; ☆, ωB = 40 %.

Figure 9. Experimental results fitted by the empirical equation at ωC = 20 %. □, ωB = 100 %; ○, ωB = 95 %; △, ωB = 90 %; ▽, ωB = 85 %; ■, ωB = 80 %; ●, ωB = 70 %; ▲, ωB = 60 %; ▼, ωB = 50 %; ☆, ωB = 40 %.

increasing the temperature and decreases with increasing the concentration of sodium hydroxide, respectively. With the presence of 5 % to 20 % of sodium hydroxide, the solubility of sodium chromate markedly decreases; and it is substantially

sodium chromate in the NaOH−CH3OH−H2O system can be illustrated as a function of temperature, and it increases with 1589

DOI: 10.1021/je5010356 J. Chem. Eng. Data 2015, 60, 1584−1591

Journal of Chemical & Engineering Data

Article

Figure 16. Solubility of sodium chromate in the NaOH−CH3OH− H2O system at 50 °C. ■, ωC = 0; ●, ωC = 5 %; ▲, ωC = 10 %; ▼, ωC = 20 %.

Figure 13. Experimental results fitted by the λ−h equation at ωC = 20 %. □, ωB = 100 %; ○, ωB = 95 %; △, ωB = 90 %; ▽, ωB = 85 %; ■, ωB = 80 %; ●, ωB = 70 %; ▲, ωB = 60 %; ▼, ωB = 50 %; ☆, ωB = 40 %.

Figure 17. Solubility of sodium chromate in the NaOH−CH3OH− H2O system at 60 °C. ■, ωC = 0; ● , ωC = 5 %; ▲, ωC = 10 %; ▼, ω C = 20 %.

Figure 14. Solubility of sodium chromate in the NaOH−CH3OH− H2O system at 30 °C. ■, ωC = 0; ●, ωC = 5 %; ▲, ωC = 10 %; ▼, ωC = 20 %.

Figure 18. Dependence of steady state critical oiling-out point on solvent composition. ■, ωC = 0; ○, ωC = 5 %. Figure 15. Solubility of sodium chromate in the NaOH−CH3OH− H2O system at 40 °C. ■, ωC = 0; ●, ωC = 5 %; ▲, ωC = 10 %; ▼, ωC = 20 %.

Kashiwase et al.16 introduced the solubility of sodium chromate in methanol solution at (25 and 35) °C. We have compared the experimental data with the law in methanol solution (25 and 35) °C. It is concluded that the solubility data is in line with the results reported by Kashiwase et al. The dependence of the steady state critical oiling-out point on solvent composition was presented in Figure 18. It can be

zero when ωB is larger than 80 %. Compared with the temperature, the concentrations of sodium hydroxide and methanol have more effect on the solubility of sodium chromate. 1590

DOI: 10.1021/je5010356 J. Chem. Eng. Data 2015, 60, 1584−1591

Journal of Chemical & Engineering Data

Article

(6) Deneau, E.; Steele, G. An in-Line Study of Oiling Out and Crystallization. Org. Process Res. Dev. 2005, 9, 943−950. (7) Stephane, V.; Eve, R. Crystallization in the Presence of a LiquidLiquid Phase Separation. Org. Process Res. Dev. 2006, 10, 841−845. (8) Shi, X. H.; Zhou, C. R.; Gao, Y. G.; Chen, X. Z. Measurement and Correlation for Solubility of (S)-(+)-2,2-Dimethylcyclopropane Carbox Amide in Different Solvents. Chin. J. Chem. Eng. 2006, 14, 547−550. (9) Wang, S.; Song, Z. Q.; Wang, J. D. Solubilities of Ibuprofen in Different Pure Solvents. J. Chem. Eng. Data 2010, 55, 5283−5285. (10) Sun, W. Z.; Qu, W. B.; Zhao, L. Solubilities of 4-Formylbenzoic Acid in Ethanoic Acid, Water, and Ethanoic Acid/Water Mixtures with Different Compositions from (303.2 to 473.2) K. J. Chem. Eng. Data 2010, 55, 4476−4478. (11) Apelblat, A.; Manzurola, E. Solubilities of o-acetylsalicylic, 3,5dinitrosalicylic, and p-toluic acid, and magnesium-DL-aspartate in water from T = (278 to 348) K. J. Chem. Thermodyn. 1999, 3l, 85−91. (12) Apelblat, A.; Manzurola, E. Solubilities of manganese, cadmium, mercury and lead acetates in water from T = 278.15 to 340.15 K. J. Chem. Thermodyn. 2001, 33, 147−153. (13) Li, F. L. The measure and correlation of the solubility of elemental sulfur in different solvents. J. Sci-Tech Inform. Dev. Econ. 2011, 21, 184−186. (14) Buchowski, H.; Ksiazczak, A.; Pietrzyk, S. Solvent activity along a saturation line and solubility of hydrogen-bonding solids. J. Phys. Chem. 1980, 84, 975−979. (15) Song, W. W.; Ma, P. S.; Xiang, Z. L.; Fan, L. H. Solubility of glutaric acid in cyclohexanone, cyclohexanol, their five mixtures and acetic acid. J. Chem. Eng. Data 2007, 2, 228−232. (16) Kashiwase, K.; Mita, M.; Kon, T.; Okabe, T. Solubility of Sodium Chromate in Sodium Hydroxide Solution and in Methand Solution. Nippon Kagaku Kaishi 1974, 9, 1224−1229 (in Japanese).

seen from Figure 18 that the steady state critical oiling-out temperature increases with the increasing of mass fraction of methanol. However, when the ωB is higher than 65 % or 60 %, the ωC is 0 % or 5 %, respectively. No steady state critical oiling out point was available, and therefore, no liquid−liquid phase separation phenomenon can be observed during the heating process. It can be concluded that the liquid−liquid separation will happen only in two cases: (1) the ωB is lower than 65 % and the ωC is 0; (2) the ωB is lower than 60 %, and the ωC is 5 %.

■

CONCLUSIONS The solubility of sodium chromate in the NaOH−CH3OH− H2O system have been measured using the static analytical method at temperatures of (303.15 to 333.15) K. The measured results were respectively correlated by the Apelblat equation, the empirical equation, and the λ−h equation. The results show that the solubility of sodium chromate increases with increasing the temperature and decreases with increasing the concentration of sodium hydroxide, respectively. Compared with the temperature, the concentrations of sodium hydroxide and methanol have more effect on the solubility of sodium chromate. The three models were proposed to correlate the experimental data, which fit the data well. Moreover, the Apelblat equation is the best for the system. Meanwhile, it was found that the liquid−liquid phase separation, also termed as oiling out, will happen under certain conditions. The relationship between the steady-state critical temperature and solvent composition was studied systematically using FBRM.

■

AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Tel.: +86 10 82544810; Fax: +86 10 82544810. Funding

This work was financially supported from the National Natural Science Foundation of China under Grant No. 21406233, the National Hi-tech Research and Development Program of China (863 Program) under Grant No. 2011AA060702, and the National Basic Research Program of China (973 Program) under Grant No. 2013CB632600. Notes

The authors declare no competing financial interest.

■

REFERENCES

(1) Raquel, R. S.; Jose, M. S.; Jose, M. D. Estragole quantity optimization from fennel seeds by supercritical fluid extraction (carbon dioxide−methanol) using a Box−Behnken design. Characterization of fennel extracts. Ind. Crops Prod. 2014, 60, 186−192. (2) Flavio, A.; Maria, G. C.; Luiz, G. L. Extracts from the leaves of Piper piscatorum (Trel. Yunc.) obtained by supercritical extraction of with CO2, employing ethanol and methanol as co-solvents. Ind. Crops Prod. 2013, 43, 490−495. (3) Kashiwase, K.; Mita, M.; Kon, T.; Okabe, T. Methanol Leaching of Reaction Product of Chromite with Molten Sodium Salts. Nippon Kagaku Kaishi 1975, 9, 1491−1495 in Japanese. (4) Xu, H. B.; Shi, Y. L.; Zhang, Y.; Cai, Z. H.; Pei, L. L.; Cheng, X. C.; Zhang, Y.; Shi, D. X.; Tang, S. H.; Chen, X. H.; Tian, Y.; Liu, J. W. A method of separating the potash alkali and chromate from the solid mixtures thereof. China Patent, CN201310461509.1. (in Chinese). (5) Shu, Y. G.; Lu, B. L.; Wang, X. R. Phase Diagram Analyses of Inorganic Chemical Production: Basic Theory; Chemical Industry Press: Beijing, 1985 (in Chinese). 1591

DOI: 10.1021/je5010356 J. Chem. Eng. Data 2015, 60, 1584−1591