T H E SORPTION OF BROMINE AND IODINE BY ACTIVATED CHARCOAL L. H. REYERSON AND A. E. CAMERON School oj Chemistry, University o j Minnesota, Minneapolis, Minnesota Received August 8, 19.96
In a previous publication (1) a method was described which made it possible to study the sorption of bromine and iodine by porous adsorbents over a rather wide pressure range a t several temperatures. At that time the sorption of bromine and iodine by silica gel a t several temperatures was reported. Equilibria for adsorption and desorption were established rapidly in the case of silica gel. In the present study on charcoal equilibrium was reached slowly, so that rates of sorption were measured in addition to the determination of the amounts taken up a t equilibrium. The charcoal used in this investigation was prepared from coconut shells. Broken coconut shells were cleaned and then placed in a large Soxhlet extractor where they were successively extracted for prolonged periods with ether, alcohol, and finally water. The extracted shells were coked in a covered iron crucible in a sand bath. The temperature was raised slowly to 550-575'C. and held there for half an hour after the last flammable vapors came off. After cooling the charcoal was crushed and sieved. A portion of 25 g. that passed a 10-mesh and was retained by a 20-mesh sieve was taken for activation. This was packed in a clean silica combustion tube and heated to 850'C. in an electric furnace. Superheated steam from a small boiler was passed over the charcoal for thirty minutes. After cooling, the average loss in weight on activation by steam was found to be 25 per cent of the initial weight. The steam-activated charcoal was then placed in a silica tube and heated to 700'C. while it was evacuated with a pair of Langmuir condensation pumps. The charcoal was protected from mercury vapor by a liquid air trap. After a 24-hour evacuation the charcoal was cooled to room temperature and oxygen admitted. After standing some time in an atmosphere of oxygen the charcoal was again heated and evacuated for a period of 48 hours. The charcoal was then cooled in an atmosphere of nitrogen. On ashing in a platinum crucible the following results were obtained: ash, 0.185 per cent; ash as sulfate, 0.233 per cent; silica, 0.026 per cent. The charcoal was crushed in an agate mortar and that portion used which passed a 60-mesh and was retained by a 100-mesh screen. About 0.2 g. 233 TEE JOQRNAL OF PHYfiICAL CHEMISTRY, VOL. 40, NO.
2
234
L. H. REYERSON AND A. E. CAMERON
PRESSURE I N
MY. CORRRCTBD
1
X/M MILLIMOLES PER GRAM OF
SORBENT
I
HOURS FOR READING
Isotherm a t 58.0"C. 0.63t 3.01 11.4t 68.8 140.4 265.7 473,O 691.8 474,1 265.8 140.4 67.4 11.4t 1.8t 0.63t 0.031
4.155 4,607 4,972 5.358 5,554 5,665 5.779 5.849 5,804* 5.702* 5.579* 5.459* 5,149* 4,787* 4.445* 3.904*
__ 90 4 5 14 0 20 0 21 5 23 0 24 0
~
PRESSCRE IN MM. CORRECTED
1
I 1
-
.st
19.2 68.1 265,8 791.5 266.7 69.5 20.3
'
Check isotherm at 58.0"C. after determining isotherms a t higher temperatures recorded in thii same table 0.037 70.6 695,6 68.3 0.00:
3.431 5,456 5,836 5.456* 3.163*
72.0 23.5 24.0 25.0 24.0
0.03t 3.01 18.6 68.3 266,2 792 3
3.044 4.088 4.729 5 048 5.311 5,527
22.0 24.0 27.0 24.0 21 .o 29.0
* Desorption
1
EOt'RS FOR READING
1
5 335* 5 076* 4 776" 4 124* 3 121*
22 22 25 10 22
0 0 0 06 0
2.611 3,355 4.207 4.629 4.990 5.217 5.013* 4.671* 4.244* 3,377* 2.623*
20.5 23.5 24.0 19.0 23.0 24.0 24.0 32.0 21 .o 25.5 24.5
Isotherm a t 178.4%.
-
~-
0.037 3.0 16.8 67.2 266.8 787.8 266.7 69.2 17.8 3.0t 0.031
readings.
t Values derived from vapor pressure function. High vacuum with charcoal a t 58.0"C. had t o be reset on temperature.
5 Thermostat
SORBENT
Isotherm a t 137 6°C.
0.03t
27.0 10.5 13.0 16.0 35.0
X /M MILLIMOLES
PER GRAM OF
Isotherm a t 98.1°C.-concZuded 266 2 68 9 18 2 3 07 0 03t
14.0
I
2.250 3.016 3.619 4.143 4.628 4.899 4.645* 4.186* 3.652% 3.054* 2.247*
38.0 33.0 25.0 20.0 23.5 26 0 20.0 27.0 26.5 23.5 72.0
SORPTION OF BROMINE AND IODINE BY CHARCOAL
235
TABLE 2 Rates of sorption of bromine by charcoal at 137.6"C.
perature = 98.1%.
-
60.031 59.597 59.252 59.125 59.009 59.001
0 5 10 25 180 400 730 1390
137.7"C.
0 20 65 195 990 1230
3.120 2.956 2.755 2.678 2.600 2.587
62.443 62.950 62.985 62.999 63.037 63.040 63.055
Pressure
59.001 59.829 60.043 60.221 60.249 ' 60.276 60.267
0 20 45 240 430 1260 1355
0 5 10 30 170 410 830 1420
2.587 3.086 3.220 3.304 3.339 3.361 3.356
-
4.623 4.906 4.932 4.946 4.974 4.976 4.985
791.5 mm.
63.064 63.370 63.396 63.405 63.420 63.433 63.448 63.450
4.990 5.153 5.179 5.184 5.193 5.201 5.216 5.217
-
-5.217 /
Pressure = 266.7 mm.*
60,267 61.289 61,457 61.491 61.564 61.633 61.703 61.715
0 15 20 25 40 100 645 1425
3.951 4.073 4.069 4.112 4,146 4.176 4.174
- - /I
Pressure = 68.1 mm.
0 5 10 15 30 60 140 245 495 1100
1
61.715 62.034 62.303 62.357 62,370 62.395 62.413 62.415 62.425 62.443
* Desorption
0 5 15 60 270 520 760 1330
1
4.174 4.370 4.529 4.566 4.586 4.607 4.612 4.613 4.619 4.623
readings.
1-
63.450 63.166 63,146 63.111 63.107 63.103 63.104 63.102
5.050 5.038 5.018 5.015 5.013 5,014 5.012
-/i
Pressure = 69.5 mm.*
-
0 5 15 60 520 670 885 1935
63.102 62.656 62.620 62.540 62.520 62.517 62.516 62,504
5.012 4.757 4.739 4.692 4.680 4.678 4.678 4.671
0 15 25 85 195 1070 1280
62.504 61.900 61.877 61.824 61.796 61.780 61.779
0 10 20 30 55 420 1090 1600
61.779 4.241 61.110 3.851 60.831 3.687 60.688 3.597 60.532 3.511 60.361 3.411 60.328 3.391 60.302 3.376
4.671 4.313 4.293 4.271 4.255 4.242 4.241
Pressure = 0.03 mm.*
0 5 10 20 60 120 195 250 910 1460
1
I
60.302 60.234 60.082 59.901 59.518 59,340 59.222 59.184 59.110 59.021
3.376 3.324 3.241 3.122 2.909 2.807 2.720 2.713 2,657 2.617
236
L. H. REYERBON AND A. E. CAMERON
of this charcoal was weighed into the little glass bucket of the McBain balance. The experimental procedure was the same as previously described (1). Table 1 gives the results obtained for the sorption of bromine by charcoal a t 58", 98.1°, 137.6", and 178.4"C. Table 2 gives the complete data a t 137.6"C. for the rates of adsorption and desorption of bromine by the charcoal. Table 3 records the results of the sorption studies of iodine on charcoal. It should be noted that during desorption it was never possible to TABLE 3 Sorption of iodine by charcoal PRESSURE IN
MM. CORRECTED
1
XI'M MILLIMOLES PER GRAM OF SORBENT
1
HOURS FOR READING
1
X/M PRESSURE I N
MILLIIOLES
MM CORRECTED
PER O R A M O F ~
11
Isotherm a t 178.4%.
5.5 2.0 12.5 3.0
0.03t 10.6 80.0 169.0 234.0 368,O 100.0 26.0 4.3 0.03t
0,07492 0.2341 0,2774 0.2897 0.2963 0,3036 0,2815* 0,2614* 0.2205* 0.0759*
30.0
0.031 10.6 80.0 169.0
0.0416 0.1881 0.2625 0.2671
17.0 3.5 1.2 12.0
SCRRENT
1
H O U R S FOR RElDING
Isotherm a t 218.8"C.-concZuded
1 ii::: 1 234.0
317.5 100.0
4.0 10.5
0.03t
0.2721 0.2829 0.2882 0,2784* 0.2593* 0.2315* 0,1470* 0.0539*
'
2.2 2.2 2.7 2.2 11.0 5,O 6.0 22 0 8.0
Isotherm a t 178.4"C.
168.4 420.0
0,2889 0.3011 0,3175
3 .O
* Desorption readings.
t Value derived from vapor pressure function.
t: High vacuum a t 525"C., spring measured a t 37°C
completely remove the bromine or iodine which had been adsorbed by the activated charcoal. In a previous paper in this journal (2) figures were given for the data here presented. They are not therefore repeated here. The data are given as a matter of record for other investigators. SUMMARY
1. Data are given for the sorption of bromine by activated charcoal a t 58", 98.1°,137.B0, and 178.4"C.
SORPTION OF BROMINE AND IODINE BY CHARCOAL
237
2. Data are given for the rates of adsorption and desorption of bromine by charcoal a t 137.6OC. 3. Data are given for the sorption of iodine by activated charcoal a t 178.4" and 218.8OC. REFERENCES (1) CAMERON, A. E., AND REYERSON, L. H.: J. Phys. Chem. 39, 169 (1935). (2) REYERSON, L.H., AND CAMERON, A. E.: J. Phys. Chem. 39, 181 (1935).
