REDWOOD TANNIN Use as a Depressant for Calcite and Quartz in the Flotation
of Fluorspar WILLIAM A. MANUEL
HARRY F. LEWIS
Ohio Weskyan University, Delaware, Ohio
The Institute of Paper Chemktry, Appleton, Wia.
Redwood tannin recovered from stumpwood, rootwood, twigs, and cones is studied as a depressant In the separation of fluorspar from calcite and silica; the results are compared with those obtained from quebracho. The etumpwood tannin in sodium carbonate solution appears to have as satisfactory an action as does quebracho tannin; stumpwood tannin in isopropyl alcohol ie not quite so satisfactory. Cone tannin is likewise satiefactory. Twig
tannin and stumpwood tannin in sodium silicate solution do not appear to clean the calcite as well as the other products. The “humic acid” from redwood bark has also been tested. Good cleaning is obtained with low recoveries of calcium fluoride when 0.4 pound per ton of ore is used; both cleaning and yield are improved with 0.5 pound. Redwood bark “humic acid” is easily obtained and could be availablein crude form at a low price.
LARGE percentage of the fluorspar produced in the United
A large amount of work a t The Institute of Paper Chemistry has developed the information that redwood extracts vary greatly in active tannin content and, possibly, in the nature of the tannin when different sections of the tree are extracted. Certain extracts are actively adsorbed by hide powder, whereas others lose very little when treated under the same conditions. A study was therefore made, applying this experience to the fluorspar flotation and using these different types of redwood tannin.
A
a
States comw from deposits centerinq around Rosiclare, Ill. These deposits contain both galena and sphalerite. Originally galena rather than fluorspar was recovered; at present the district has become prominent as a producer of fldorspar, and the galena has become incidental. In the deposit being worked near Cave-in-Rock, Hardin County, Ill., a high lead-zino-fluorspar ore is obtained. In addition to galena, sphalerite, and fluorspar, it contains a certain aniount of caloareous and siliceous material with smaller amounts of pyrite and barite. The utilization of such an ore consequently involves the eeparation of galena, sphalerite, and fluorspar from one another and from the gangue. The separation of the sulfide ores-that is, galena and sphalerite-from fluorspar and the lime and silica is not important in connection with this report. The actual problems of interest in connection with the study of redwood tannin involve the flotation of fluorspar from calcium carbonate and silica. The method followed a t Rosiclare (I) involvea the use of oleic acid as a flotation agent with quebracho tannin added to depress the calcite and silica during the fluorspar flotation. The tannin appears to act as a deflocculating agent for the calcite and silica. It is essential to control the amount of quebracho used, because rtn excess has been found to retard flotation of the fluorspar. The optimum amount varies with zhe particular types of collector employed, the dilution of the stocks, and the pH. Metallic salts should also be at a minimum, since metal tannates also depress fluorspar as well as calcite and silica. In the present emergency, where every pound of quebracho has to be imported, the use of domestic redwood tannin would appear to merit consideration. In actual operation, the tailings from the sulfide ore flotation are fist conditioned with sodium cyanide, quebracho tannin is then added, and, after the proper period of conditioning, a definite amount of oleic acid is added and air is admitted to the flotation cell. Fluorspar appears in the froth resulting from the flotation operation, and calcite and silica remain in the liquid phase. In view of the similar characteristics of quebracho and redwood tannin, experiments were set up to determine whether the latter could be used aa well as the former. Preliminary tests made with a sample of redwood tannin by the mining company indicated that this might be possible, although possibly three times as much redwood tannin would be required as quebracho tannin.
FLOTATION TESTS
Actual flotation results in the mill can be predicted from Iaboratory tests and are almost always better than laboratory results. In this work a Fagergren laboratory test machine W&B used because of its simplicity, ease of cleaning, and efficiency. The ore was ground in a No. 2 Patterson ball mill (porcelain jar with flint pebbles). The sample for each test was wet-ground just before use, so that its surface did not change between grinding and flotation. The ore consisted of tailings, described as “fine tailings from I) gravity plant”. Analysis showed that it contained 11.2% calcium carbonate, 77.7% calcium fluoride, and 10.0% silicou dioxide. All pH values were determined with a Cameron glass electrode pH meter. In general, the following technique was followed in the various flotation experiments: 600 grams of ore were ground in the ball mill with an equal volume of distilled water for 20 minutes. The ore was washed into the flotation cell, and supernatant water in the cell was siphoned to a volume of 1170 cc., which gives a 80% solids consistency in the cell. The total weight of ore and water is thus 1670 grams. The conditioning agents (tannin) were added, and the conditioning carried out as indicated in Table I1
TABLEI. TANNIN CONTBNTB OB EXTRACTS (Bone-Dry Basis) Material uebrscho cryatale uebrscho extract Acetone-insol. redwood tannin 37 Acetonesol, redwood tannin 37 Water extract. cone tannin Twig extract
8 1169
7 Tannin, S.O.A.C.
Tannin WiEon-Kern’O)
87.8 81.6 65.6 51.4 82.8 86.3
31.1 32.4 13.8 0.7 67.8 4.6
INDUSTRIAL AND ENGINEERING CHEMISTRY
1170
Vol. 36, No. 12
TABLE 11. CONDITIONS OF ROUGHING AND CLEANING, OF CALCIUM FLUORIDE AND PURITY AND RECOVERY Run No. 33 34 37
38
39 41 42 43 44 46 47 48 67 02 64 06 00 63 09 71 72 76 76 77 78 80
Tannin Acetone-insol. tannin in NarCO: Acetone-sol. in NarCOa Tannin 37 in 10% acetone Tannin in NanSiOa No tannin Cone crystals Total tannin 37 in 0.6% NarCOa Total tannin 37 in water Acetone-sol. rootwood tannin in NazCO: Acetone-insol. rootwood tannin Crude extract. 66736 uebracho wig tannin in 0.5% NazCOa Tannin 37 in moDroDvl alcohol Tannin 37 in irroprobvl alcohol Tannin 37 in isopropyl alcohol Tannin 37 in isopropyl alcohol Tannin 37 in isopropyl alcohol Tannin 37 in is0 ropy1 alcohol Bark humif; a p i g Tannin 37 in isopro 1 alcohol $mbracho in 0.6% %azCOa uebracho in water annin 37 in 0.6% NarCOa Same as 77 Bark humic acid
9’
Grinding Time, cc. min.
HrO, 800 800 600 500 600 600 600 600 600 600 500 500 600
600
600 500 500 600 600 600 600 600 600
500 600
600
HrO, cc.
Conditioning ‘ Time, Tannin lb./ min. ton of bre
26 26 22 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20
for the time cited without further dilution. At the end of the period, the water previously siphoned, plus enough distilled water to bring the level 0.5 inch below the lip of the cell, was added with the first-stage “rougher” reagent-oleic acid. The conditioning stage and first rougher stage (Ri) can be considered as a single operation because, after the conditioning period, the flotation agent waa added without stopping the machine and air was admitted to bring about flotation. The froth was cleaned from the flotation cell with a Bakelite paddle (3 X 6 inches) with rubbertaped edges. At the end of the first rougher period, the secondstage (RJ rougher reagent was added, and the resultant froth was added to the R1 froth. The first and second roughing operations are, therefore, two stages of a continuous process. The residue in the cell contains the tails. After the cell was emptied and rinsed, the R1 and R:,froths were placed in the cell, water was added to bring the level 0.5 inch from the lip, and the first cleaning period (C1) was begun. This first period waa generally without additional tannin. The residue from the cleaning operation is referred to as middlings (sometimes cleaner tailings); from C1, MI was obtained. The CI froth was again returned to the clean cell, and the CI reagent (tannin) was added after the water level had been restored 0.5 inch below the lip. The froth recovered from the Ct operation was then treated t o a third cleaning stage and the residue becomes Mt. The concentrate (froth from third cleaning stage Ca), the three middling fractions, and the tailings were dried separately and weighed; in general, only the concentrate was analyzed. The above procedure was developed as the result of a large number of preliminary experiments involving variations in time, number of cleaning stages, concentration of reagents, and grinding conditions. A number of different tannins were investigated. A short description follows: 1. Redwood tannin 37, extracted from redwood stumpwood by 95% alcohol, and separated from phlobaphene and other water-insoluble resinous material by evaporating the alcohol at reduced pressure. the tannin remains dissolved in the residual water and the phloba henes and water-insoluble resins are removed by filtration. &he water-soluble tannin 37 was recovered by evaporation of the water in a vacuum-pan dryer equipped with stainless steel pans. 2. Redwood cone tannin, crystals of redwood cone tannin shaken from air-dry cones. 3. Redwood twig tannin, prepared from twigs by essentially the same process described for redwood tannin 37. 4, 5. Acetone-soluble and acetone-insoluble fractions of redwood rootwood tannin, originally recovered from the rootwood in a manner similar to that described for stumpwood tannin 37.
Roughing (Oleic Acid) -Rr-RITime, Reagent, lb./ Time, Reagent lb./ min. ton ot ore mm. ton ot’ore 2 1.0 3 0.5 1.0 2 3 0.6 2 3 1.0 0.6 2 1.0 3 0.5 1.0 3 3 0.6 3 1.0 2 0.6 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 2 2 3
1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 0.8 1.0 1.0 0.6 0.6 1.0
2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2
3
2 2
0.5 0.6 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.6 0.5 0.6 1.0
0.5 0.4 0.6 0.5 1.0 0.6
0.6
6. For comparison quebracho liquid and quebracho crystals. 7. A humic-acid-lie material recovered in large yield from the redwood bark by solution in hot dilute caustic and precipitation with acid.
Tannin 37 waa modified by solution in isopropyl alcohol, in sodium silicate, in sodium carbonate, and in 10% acetone solution. These extra.cts have different tannin contents as determined both by the A.O.A.C. and Wilson-Kern (2’) methods. The values are indicated in Table I. The A.O.A.C. is the standard method usod by leather chemists for tannin determination. In brief, it involves the extraction of tannin from a solution of given concentration by a specially prepared hide powder adsorbent; the suspension is filtered to separate it from the nontannins, and the latter are determined in the filtrate. Wilson and Kern have shown that certain nontannins structurally related to the tannins (such aa gallic acid, pyrocatechol, etc.) are adsorbed loosely under these conditions and play no part in the tanning reaction. They therefore introduce a washing step and determine the tannin retained in the hide powder. Experience here indicates that the Wilson-Kern method predicts certain other tannin characteristics of the extracts more reliably than does the standard method. The conditions and results of the more significant flotation tests are assembled in Table 11. The effect of varying the nature of the tannin on calcium fluoride recovery and purity of the product is shown in Table 111; results essentially equal to quebracho are obtained when either tannin 37 in 0.5% sodium carbonate or cone crystals are employed. The same reagents give high recoveries of calcium fluoride. Purities equal to those with que-
TABLE 111. EFFECT OF VARIATION IN TANNIN SOLVENTS AND SOURCE Flotation Reagent Blank Tannin 37 in: Sodium silicate
Concentrate CaFz Wt.. In conoen- RecovGrams trate, Yo ery, %
Impurities in Concentrates % C m
380
94.3
92.2
6.2
o.a
363.6 360.5 349.5 337.5 393.6 327.6 347.5 347 330 332 320 294.5
90.0 90.8 971.6 97.0 94.0 97.4
88.9 88.7 57.8 84.3 95.2 82.1
97.6 90.7 97.4 90.7 96.5
80.9 82.9 82.7 81.7 73.1
3.4 2.0 2,o 2.4 5.3 2.7 4.7
0.4 0.8 0.0 0
...
...
...
1.9 2.5 2.0 2.1
... ..* ... ... ... ...
0
INDUSTRIAL AND ENGINEERING CHEMISTRY
December, 1944
I171
TABLE 11. (Continued) Cleaning Stage -
C
v
-Ca-
Rea ent Rea ent, Time, Ib.yton' Time, 1b.yton min.4' mm. of ore min. of ore 2 2 0.01 0.01 2 2 0.01 0.01 3 3 0.1 0.1 3 3 0.1 0.1, 3 3 3 0.1 0.1 3 3 0.1 0.1 3 3 3 0.1 0.1 3 3 3 3 0.1 0.1 3 3 3 0.1 0.1 3 3 3 0.1 0.1 3 0.1 3 3 0.1 3 0.1 3 3 0.1 3 3 0.1 3 0.1 3 3 3 0.1 0.1 3 3 3 0.1 0.1 3 3 3 0.1 0.1 3 3 3 0.1 0.1 3 0.I 3 3 0.1 3 3 0.1 0.1 3 3 0.1 3 3 01 3 3 0 :i 3 0.1 3 0.1 3 0.1 3 3 3 0.1 0.1 3 3 3 3 0.1 0.1 3 0.1 0.1 3 3 No reagent used in CI. CI
Run Tim:
No. a3 34 37 38 39 41 42 4a 44 46 47 48 67
62
64 61 66
63 69 71 72 7s 76 77 78 80 a
...
. . I
Conc. 262.S 2S7.S 3S6.S 363.6 380 347 349.5 337.8 326 332 327.S
330 347.6 344.6 346 329 339.s 321 333 306.6 311 320.1 320.S 317 333 294.6
Products, G r a m Mi &ft MMI 80 44.s 34.s 82.S 60.6 (11.6 20 36.6 11 31 14.S 38 13.6 4i ~. 28 1s 40 22.11 12.s 41,s 32.s 17.0 49.5 2s 19 (12.6 21 14.6 S8.S 26.1 13.6 153 22.6 13.S S3.6 22.s 11 A7 24.6 14.5 i i . s 20.6 9.s 4s 21 13 46.5 19,s 14 20 48 10 2s 46 12 S6 33 1s 17 28 13,s 49 24 13.6 46.S 10 17 60 31.6 20.s 49,s 31 20 4s.s 29 11.8
3
bracho, with somewhat higher yields of calcium fluoride, would appear to be possible from the technical use of redwood stumpwood tannin in sodium carbonate solution under the conditions described. Cone tannin would also be used, but this is a moduct of only theoretical interest. Incidentally, the conditions giving the best results with the redwood tannin are also those which result in the best leather in the tanning of calfskin. Acbowledflent is made to The Pacific Lumber company for making poasible this project and to the MahQning Mining Com-
Tails
67.8 s3.3 62.S
47.s 48.6 60.6 66
67 76.1 73 68.6
7s
64.1 60.S 68.8
79.6 68 90 a2 86.11 88.S 79 90.6 73.6 62.6 106.6
Purity Of Con% % CaCOt SiO: CaFz
1 .6 2.4 2.6 3.4 6.2 1.9 2.0 2.4 2.1 2.S
2.7 1.9 4.7 2.4 2.8 1.7 1.7 1.4 1.4 1.6 1.7 1.6 1.6 1.9 18 2.1
0.1 0.1 0 0 0.2 0 0 0.4 0.4 0.4 0.6 0.6
...
... ... I.. ... ... ... ... ... ... ... ..* . I .
e . .
97.6 96.7 96.8 96.0 94.3 97.4 97.6 97.0 97.4 96.7 97.4 97.6
...
96.6
... ... 98.b ... 97.s 97.0 ... 97.4
96.7 96.6
PH
~~~~~~
Con& After Conoen% tioningroughing trate 66.8 9.6 8.8 63.9 ... 8.9 9.4 i:i 88.7 8.6 9.9 9.4 88.9 9.2 92.2 9.3 8.8 8.9 86.9 9.3 8.7 8.6 9.4 8.7 87.8 8.8 9.4 9.0 84.3 9.0 81.7 9.5 8.7 8.7 82.7 9.6 8.7 9.0 82.1 9.6 8.9 9.1 9.4 8.9 8.8 82.9 9.0 8.7 8.7 9.3 8.8 8.8 86:O 8.6 9.2 8.6 ... 9.2 8.6 8.8 ... 9.3 8.8 8.S 8.S 9.2 8.7
...
84.0
... ... 79.7
78.0 so.1 82.8 73.2
... ... ... 9.7
9.8
... ...
9.3
... ... 9.2
...
8.8
8.6
9.2
9.0 9.0
8.9
i:i
... ...
...
...
pany for cooperation and for the samples of ores used in the experiments. LITERATURE CITED
(1) Bur. of Minee, Metallurgioal Div., Prolress Rept. 31 [Rept. Zn-
uestigation 3437 (1939)l. (2) Wilson and Kern. J. IND. Em. C E ~ M .13, . 722 (1921). P R ~ S B N T Dbefore D the Divieion of Industrial and Engineering Chemistry a t the 107th Meeting of the AMERICAN CEEXICALS O C I ~ T YCleveland, , Ohio.
ACETYLATED CASEIN FIBER ALFRED E. BROWN, W. G. GORDON, EDITH C. GALL, AND R. W. JACKSON Eastern Regional Research Laboratory,
U. S. Department of Agriculture, Philadelphia, Pa.
M
ILLIONS of pounds of casein fiber have been produced, both here and abroad. The fiber is in an active stage of development, as shown by the extensive literature. Compared with wool, casein fiber as ordinarily hardened with formaldehyde h inferior because of its lower tensile strength, particularly when wet, and because of its poor resistance to boiling, especially in mildly alkaline solution. Similar properties with consequent need of improvement have been encountered in artificial fibers prepared from a number of other proteins. A British patent (14) reported that treating fibers spun from peanut protein with acyl chlorides would improve the resistance of the fiber to hot dilute acid as well as impart water-repellent properties. Reaction with ketene and acetic anhydride was subeequently claimed (26) to produce the same benefits in artificial protein fibers. Another patent (16) deals specifically with the acetylation of casein fiber by ketene or acetic anhydride, with or without catalysts. A process for treating protein fiber such as casein, involving the use of acylating agents like ketene and acetic anhydride in the presence of fatty acid catalysts, to improve or modify dyeing affinities, resistance to water, and other properties, was patented (1). The water-resistant properties and dyeing aharacteristics of Aralac, the casein fiber made commercially in
this country, were described (9). Up to the present, however, no detailed study of the acylation of hardened casein fiber has been published. Acetic anhydride has been used to acetylate wool for the purpose of masking the basic groups and thus decreasing the afiinity of the wool for acid dyes (4). Elliott and Speakman (3)recently described such a process based on treatment with acetic anhydride and glacial acetic acid in the presence of sulfuric acid. K i and Carr (7)studied the acetylation of silk fibroin with ketene. Up to 7.3% acetyl content waa obtained, depending on the duration of exposure to ketene, but the fibers were colored tan to brown. No correlation with other physical properties was reported. I n a later paper, describing the acetylation of silk by acetic anhydride, Carr (9)showed that sodium acetate accelerated the reaction. The literature on the acetylation of proteins other than fibers is reviewed in another article (6). The investigation reported here was undertaken for the purpose of correlating acetylation with its effect on important properties of casein fiber. Three types of casein fiber were prepared. All were spun from the same batch of -in. One type was precipitated in a bath containing aluminum sulfate and collected in skein form (referred
