I N D U S T R I A L A N D ENGINEERING CHEMISTRY
September, 1930 ADSORPTION:FACTS COKCERNING,
AND
METHODS
OF
TESTING
(11) Bliih and Stark, “Concerning Adsorption,” Vieweg (1929). (12) Fieldner et al., “Methods of Testing Gas Mask Adsorbents,” J. IND. ENG. CHBM., 11, 1519 (1919). (13) Harkins and Ewing, “Density of Gas Mask Charcoals,” Proc. Nal. Acad. Sci., 6, 49 (1920). (14) Howard and Hulett, “Study of the Density of Carbon,” ,J. Phys. Chem., 28, 1082 (1924). (15) McBain and Tanner, “Microbalance for Weighing Sorbed Films,” Proc. Roy. SOC., l26(A), 579 (1929). (16) Ruff and Roesner, “Adsorption of Gases by Activated and NonActivated Charcoal,” Ber., 60(B), 411 (1927). (17) Stamm. “Density of Wood Substance a n d Adsorption by Wood,” J . Phys. Chem., 33, 398 (1929). (18) Urbain, “Effect of Size of Pores in Charcoal on Specific Adsorption,” Compf. Rend., 180, 6 3 (1925). THEORIESOF ADSORPTION
(19) Freundlich, “New Conceptions in Colloid Chemistry,” Dutton. (20) Gibbs, “On the Equilibrium of Heterogeneous Substances,” Collected Works of J. Willard Gibbs, Vol. I. p. 65, Longmans. (21) Langmuir, “Theory of Adsorption,” Phrs. Rev., 6, 79 (1915). (22) Langmuir, “Constitution and Fundamental Properties of Solids and Gases,” J. A m . Chem. Soc., 38, 2221 (1916). (23) McBain and du Bois, “Experimental Test of the Gibbs Equation,” Ibid., 61, 3534 (1929). (24) Patrick, “Capillary Theory of Adsorption from Solution,” Trans. A m . Inst. Chem. Eng., 15, (I), 283 (1923). (25) Ruff, “Theories of Adsorption by Active Carbon,” Kolloid-Z., 38, 174 (1926). (26) Smith, “On the Adsorption of Gas by Charcoal,” Proc. Roy. SOC. (London), 12, 424 (1863).
FORMS O F CARBON ,(27) Alm, “X-Ray Investigation of Heat-Treated Amorphous Carbons,” M. I. T. Chemical Engineering Thesis (M. S.), 1927. (28) Bragg, “Carbon Atom in Crystalline Structure,” J. Franklin I n s f . , 198, 615 (1924). (29) Debeye and Scherer, “Study of the Form of Amorphous Carbon,” Physik. Z., 18, 291 (1917). (30) Lowry, “Significance of Hydrogen Content of Charcoals,” J . Phys. Chem., 33, 1332 (1929).
93 1
(31) Ramon and Krishnamurti, “Graphite Lattice Structure,” Nofure, 124, 53 ~ 9 ) . (32) Ruff, Schmidt, and Olbrich, “Amorphous Carbon and Graphite,” Z . anorg. allgem. Chem., 148, 313 (1925). PREPARATION O F
PRIMARY CHARCOAL
(33) Banks and Lessing, “Influence of Catalysts on Wood Carbonization,” J . Chem. Soc., 126, 2344 (1924). (34) Lichtenberger, “Carbonization of Wood,” Ten Years of Scientific and Industrial Efforts, Chemie et induslrie, Paris. (35) Schorger, “Chemistry of Cellulose and Wood,” McGraw-Hill. THEORYO F CHARCOAL .4CTIVATION
(36) Briggs, “.4dsorption of Gas by Charcoal, Silica Gel, etc.,” Proc. Roy. Soc. (London), 100(A), 88 (1921). (37) Chaney, “Activation of Carbon,” Trans. Elec. Chem. Soc., 36, 91 (1919). (38) Knight, Garner, and McKie, “Area of the Internal Surface of Charcoal,” J . Phys. Chem., 31, 641 (1927). (39) Netzke, Air Activation of Carbon Blacks, Report 3, Problem W-2, M. I. T. Laboratory. (40) Sutcliffe, “Gas Adsorbent us. Decolorizing Charcoal,” Chemistry Induslry, 43, 635 (1924). P R O C E S S OF
ACTIVATIOX
(41) Barnebey and Cheney, “Steam Activation in Tunnel Kiln,” U. S. Patent 1,541,099 (1925). (42) Bayer & Co., “Manufacture of Active Charcoal by Briquetting Charcoal Fines and Chemicals under Pressure,” British Patents 195,390 (1923) and 246,110 (1925). (43) Chaney, “Manufacture of Active’ Carbon (Steam Distillation),” U. S. Patents 1,497,543 and 1,497,544 (1924). (44) Metalbank Co., “Zinc Chloride for Activating Charcoal,” British Patent 238,889 (1924). (45) Mumford, “Briquette Lignite, Dolomite, and a Binder,” U. S.Patents 1,268,181 and 1,287,592 (1918). (46) Sauer, “Heat, Mixed Gases, and Stirring during Activation,” U. S. Patents 1,502,594 (1924) and 1,641,053 (1927). (47) Urbain, “Coal Compressed with Zinc Chloride or Phosphoric Acid, British Patents 257,269 and 257,917 (1927); U. S. Patent 1,610,399 (1926).
Fermentation Products from Cornstalks’ C. S. Boruff with A. M. Buswell ILLINOISSTATE WATERSURVEY,URBANA,ILL.
I
AN earlier paper (1) the writers have called attention to a possible commercial source of methane and carbon dioxide based on the anaerobic fermentation of cellulose and cellulosic materials. I n the digestion of pure cellulose the decomposition goes almost quantitatively to the two gaseous products, carbon dioxide and methane. However, in the fermentation of plant materials, as for instance cornstalks, the decomposition, so far a t least, has not been found to be complete. It is the purpose of this paper to report the analysis of this residue as well as to give the distribution of the different products formed in the digestion. ?;
Experimental Procedure
A 25-liter bottle was fitted up as a small digestion tank. It was arranged with tubes so that cornstalks could be added and withdrawn a t will without opening the tank to the air. -1 mercury-sealed inechanical stirrer served as a means of keeping the bottle contents mixed. To this bottle were added 50 grams of dry cornstalks and 22 liters of overflow liquor from a sewage-disposal plant. This liquor served as an inoculum as well as a suitable source of nitrogen for the bacteria. During the 90-day period of the experiment corn1 Received June 2, 1930. Presented before the Division of Cellulose Chemistry a t the 79th Meeting of the American Chemical Society, Atlanta, Ga., April 7 t o 11, 1930.
stalks were added from time to time and samples of the mother liquid were withdrawn and the volume made up by adding raw sewage. Samples of the cornstalks that settled to the bottom of the tank during the digestion were also withdrawn and composited with those remaining a t the end of the experiment. An analysis was made of everything that was put into and taken out of the tank. Table I gives a summary of these data. Figure 1 shows graphically the amounts, as well as the days, on which cornstalks were added. At the end of the experiment the active cornstalks remaining in the tank were separated from the mother liquid by means of a screen filter. These stalks were then washed with distilled water, dried, composited with those drawn during the run, ground, and analyzed (Table 111). The mother liquor and the washings were also analyzed and the data recorded in Table I under the heading “Sludge and Soluble Solids.” Additional data as to the nature of these solids are given in Tables I V and V. A portion of the total solids was extracted with cold water and the water-insoluble sludge analyzed separately (Table V). It might be stated a t this point that the ultimate analysis of this material throws little light upon its chemical nature. It possessed humus-like characteristics and probably would be called such by most investigators (8, 10).
G
\3
-
- n
10. 10
11
I1 -
1
-----I
rl
0
I1
I
11 T
I l l
During the experiment 1535 grams of dry cornstalks were fed and from this 370.02 liters of gas were collected. This volume of gas, when corrected for the 4.56 liters of carbon dioxide found to be dissolved in the mother liquid a t the end of the run, totals 374.58 liters. The gas data may be summarized as follows:
con
H2 CH4
Na Total
Liters 178.81 6.16 159.30 30.31 374,58
Per cent bv volume 47.7 1.7 42.5 8.1
Grams 350.5 0.6 113.9 37.9
502.9
No correction has been made for the gases coming from the digestion of the inoculum or sewage solids added, since the organic matter in these solutions (35.7 grams) amounted to only 2.5 per cent of that added as cornstalks (1412.2 grams). It will be noted that the volume ratio of COP:CH, is 1.0:0.89. This corresponds well with the theoretical (l:l), The simplest reactions that can be written to illustrate the gasification of cellulose and the pentosans, as well as the formation of acetic acid from these materials, are as follows: Cellulose : (CBHIOO~) HzO = 3co2 3CHr (CeHioOs) H20 3CHsCOOH 162 18 = 180
++ + + -Pentosans: __ . 2(CsH.04) + 2H20 = 5CO2 + 5CH4 2(CsHs04) + 2H20 5CHsCOOH 264 + 36 = 300
-------
I l l 1 1 1 1 ---------
I
Ilttmt
1 I
-
I II -
more, the fact that the carbon dioxide content of the gas exceeds the methane indicates a certain amount of oxidation. This would give an appreciably higher weight of gas than indicated by the above equations. The apparent ash digestion of 34.1 grams (Table I) is due in part to the digestion of the sulfates present to sulfides and hydrogen sulfide ( 2 , 3, 6). As the sulfur content of cornstalks is only about 0.1 per cent ( 5 ) , and that of overflow liquor and sewage about 40 parts per million (as s), the decomposition of sulfates cannot account for all t h e apparent loss in ash. The remainder is undoubtedly due to experimental error in the ash determination. It is commonly recognized that this error is quite appreciable in such mixtures as herein described, and especially is such the case when large calculation factors are used ( 2 ) . Table I-Summary QUANTITY
of General Data
VOLATILE
TOTALORGANICACIDSAS SOLIDS SOLIDS ACETIC ASH Grams Grams Grams Grams
MATERIALS ADDED
Inoculum solution 22 liters 5.1 grams Buffer salts Sewage 17 liters Cornstalks (dry) 1535 grams Total
41.844 22.596 5.368 19.248 5.1 5.1 16.490 6:ooz i:ioz 10.488 1535 1412.2 . . . 122.8 1598.4 1440.8 7.170 157.6
.
....
SUBSTANCES REMOVED
__. .._
(3) (4)
Overflow liouors Sludge and .soluble solids Cornstalks: Top (active) In sludge (inert) Total
26.7 liters
150.3
103.4
57.0
116.4
80.8
36.5
798.9 grams 798.9 33.3 grams 33.3 832.2(cornstalks) 1097.9
768.6 31.6 974.4
....
.. .. .. .. 93.5
46.9 34.6 40.3 1.7 123.5
DIGESTED
From these equations it will be noted that cellulose should give 11 1 per cent of its weight either as acetic acid or as carbon dioxide and methane. Similarly, the pentosans should give 114 per cent. Buswell and Neave, of this laboratory, have noted that the weight.of gas generated from the decomposition of fats may amount to 150 per cent of the weight of the material decomposed. The 485.0 grams of carbon dioxide, hydrogen, and methane plus the 86.3 grams of organic acids collected in this experiment represent a decrease of 466.4 grams (Table I) in the organic matter. I n other words, the gas and acids represent 118 per cent of the weight of the organic matter decomposed. The difference between these theoretical yields and the actual yield as found may be due in part to the decomposition of the lignin, resins, and waxes found in the original cornstalks. No equation has been suggested for the decomposition of lignin. From its empirical formula, CaH4eOla,(7) it would be expected that it would give a higher yield of gas per gram of material de-
702.8 (cornstalks)
500.5
466.4
86.33 34.1 (formed)
Table I1 gives a distribution of the products formed in the digestion. The 465 grams of gas represent the gasification of 30.3 per cent of the cornstalks added. Table I shows that there was an increase in the volatile acid content of the tank liquors amounting to 86.3 grams. This represents 5.6 per cent of the weight of the stalks added. This amount can be kept to a much lower figure by the proper regulation of digestion conditions. As the total ash content of the original stalks was 122.8 and that of the residual cornstalks only 42.0 grams, there must have been 80.8 grams of mineral matter leached from the stalks. This decrease in ash amounts to 5.3 per cent of the total weight of stalks added. The total organic solids found in the overflow liquors, and in the sludge and soluble matter a t the end of the run (184.2), less that added at the beginning of the run (28.6), represents the “sludge” or “humus” formed during the digestion of the
I S D C S T R I A L AA-D ENGINEERISG CHEMISTRY
September, 1930
cornstalks. This amounts t o 155.6 grams. Of this amount 83.3 grams were recovered a t the end of the experiment as water-insoluble sludge. cif Products Formed i n t h e Digestion of Cornstalks Per cent of Grams stalks added Cornstalks added 1535.0 Cornstalks recovered 832.2 54.3 702.8 45.7 Cornstalks digested Recovered as: Soluble and suspended solids: Ash 80.8 5.3 Organic matter 135.6 10.0 Acids, volatile organic 86.3 5.6 Gas 463.0 303 __ Total 787.7 51 2
Table IV-Extraction
Analysis of Water-Soluble a n d Water-Insoluble Sludge Per cent of original weight Hot-water soluble 31.0 Ether soluble, after 1 1.7 Alcohol-benzene soluble, after 2 2.9 Pyridine soluble, after 3 1.2 NaOH (370) soluble, after 4 34.0
Table 11-Distribution
Table 111-Analysis
of Cornstalks Before a n d Following Anaerobic Fermentation0 ORIGINAL CORNSTALKS FOLLOWIVG FERMENTATION Compo- Weight Compo- Weight RECOMPONENT sition added sition recovered M O V E D Per ccnf b Grams Per cent b Grams Per cent Total 1535.0 .. 832.2 46 Ash 8.0 123.0 5.05 42.0 Cold-water soluble 1 hour 12.2 187.0 1.4 11.6 b4‘ Ether soluble 1.8 27.6 2.4 20.0 28 Alcohol-benzene soluble 8.6 131.0 5.8 48.3 63 Pentosans, total 22.1 339.0 25.9 215.0 37 Lignin, total 27.4 421.0 29.6 246.0 42 Cellulose, C. & B., pure 32.1 493.0 29.6 246.0 50 Ammonia nitrogen 0.066 1.01 0.0366 0.31 69 Total nitrocren 0.729 11.20 0.917 7.64 32 Alcohol-waier soluble sugars: c Reducing, as dextrosed 1.09 16.7 0.00 0.00 103 After hydrolysis, as dex1.36 20.9 0.00 0.00 100 troses Xylose! 0.28 4.3 0.00 0 . 0 0 100 0 Except where otherwise stated, analysis was made as per Bray, Paper Trade J., 87, 59 (1928). b Dry weight. e Assocn. Official Agr. Chem., 1925, p. 118. d Munson and Walker method. e Twenty-five-cc. sample hydrolyzed by 2.5 cc. concd. IlCl at 70’ C. for 7 minutes. I Six carbon sugars removed from hydrolyzed sample by use of Saccharomyces cereuesiae. I Loss in ash recovered in part in mother liquor.
.. .
.
Table I11 gives an analysis of the cornstalks that were used in the experiment, as well as an analysis of a composite of the stalks drawn from the tank during the digestion and those left a t the end of the experiment. From this table it is apparent that the water-soluble constituents are almost entirely removed. Although there is not a very pronounced difference in the analysis of the water-insoluble matter of the cornstalks before and after being exposed to anaerobic digestion, it is noted that there is a greater decrease in the cellulose content than in any other constituent. The sugars are, of course, an exception to this statement. They are quantitatively removed. The analytical data presented in this paper bear out the fact that cellulose is more readily attacked anaerobically than is lignin. Only a trace of cellulose was found in the sludge or slime a t the bottom of the vessel, but the lignin and pentosan contents were found to be 34.4 and 11.1 per cent, respectively. Making these corrections to the data given in Table IV, there was noted an over-all removal of 35 per cent of the lignin, 34 per cent of the pentosans, and 50 per cent of the total cellulose added.
933
It is quite generally recognized that anaerobically cellulose is almost quantitatively decomposed to acids and gas. Pentosans are also known to ferment quite readily, The lignin problem, however, is still an open question. Most investigators agree with the Fischer-Schrader theorynamely, that lignin is changed anaerobically to ulmic substances or humic acids, which in turn are the precursors of coal (4, 9). No announcement has been made of the anaerobic gasification of lignin; in fact, the literature indicates that it does not decompose to gas under anaerobic conditions. Waksman and Stevens (9) state “that under anaerobic conditions lignins do not decompose a t all or only in mere traces due to the absence of specific organisms, while under aerobic conditions the lignins are slowly decomposed, but here as well they are found to be the most resistant group of plant constituents.” The 465 grams of gas collected in this experiment represent the disappearance of 147 grams of lignin, 115 grams of pentosans, and 247 grams of cellulose. From this it is noted that the pentosan and cellulose decomposition alone cannot account for the weight of gas collected. I n other words, the anaerobic flora and digestion conditions present were capable of fermenting a t least part of the lignin to gaseous end products. This fact may find commercial use in the gasification of the enormous amounts of lignin now thrown to waste. Table V-Analysis of Water-Insoluble Sludge (Total weight, 83.3 grams) Per cents Ash 23.11 34.4 Lignin (ash-free) 11.1 Pentosans Trace Cellulose Undetermined (by difference) 31.4 ULTIMATE ANALYSIS
0
Total nitrogen Carbon Hydrogen Sulfur (total) Ash Oxygen (by difference) Dry basis,
2.76 30.21 5.20 0.56 23.11 38.16
L i t e r a t u r e Cited (1) Boruff and Buswell, IND. END.CHRM., 11, 1181 (1929). (2) Buswell, Symons, and Pearson, Illinois State Water Survey, Bull. 29 (1930). (3) Elder and Buswell, IND. END. CHEM.,11, 560 (1929). (4) Fischer and Schrader, Brennstof-Chem., 2, 37 (1921). (5) Headden, Colo. Sta., Bull. 114 (1907). (6) Pedlow, N. J. Agr. Expt. Sta., Bull. 486, 64 (1929). (7) Phillips, J . A m . Chem. Soc., 49, 2037 (1927). (8) Waksman, Soil Science, 28, 123 (1926). (9) Waksman and Stevens, Ibid., 61, 1187 (1929). (10) Waksman and Tenney, Ibid., 22, 395 (1926).
Cooling System for KDKA Transmitters Station KDKA, Pittsburgh, has recently installed a modern water-softening system t o be used in connection with the cooling system for the gigantic vacuum tubes used in radio transmitters. There is a practical reason for this installation because these giant tubes are expensive and unless properly protected their useful life period is limited. Therefore, anything that can be done t o increase their life constitutes a saving in costly replacements. According to E. B. Landon, chief operator of the Westinghouse East Pittsburgh transmitting station, the water must be tested frequently to protect the tubes and the cooling system. Ordi-
nary city water cannot be used because it contains lime and other minerals which form harmful scale in the coils. The wellknown soap test, consisting primarily of partially filling a test tube with water to which is added a drop of liquid soap, is used to determine whether the water is hard or soft. If the water becomes soapy when shaken it is soft and is suitable for use in the cooling system. At the KDKA station this ultra-soft water is pumped to an outdoor cooling pool before going to the cooling coils and the tubes. Hot water coming from the station circulatory system enters the pool through a fountain-like spray. After cooling in the pool, it is pumped through the same circuit again.
