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INDUSTRIAL AND ENGINEERING CHEMISTRY
I n spite of its activity, it is believed that the special nickel catalyst offers no significant advantage; in fact, its use presents a disadvantage in that the product 1,3-butanediol must be separated from the triethylene glycol. A catalyst just as suitable, or more so, could be obtained by re-using Raney nickel. In this case, after the fist run, the nickel would be protected in 1,3butanediol-ethyl alcohol mixture which would not complicate the separation problem. ACKNOWLEDGMENT
The authors thank E. P. Schoch, director of the over-all projeet, for his endorsement and release of this paper for publication. They also thank H. R. Henze for many helpful sugges-
Vol. 45, No. 3
tions, and acknowledge the help and participation of C. Weldon ChafKn, Melvin A. Nobles, and D. A. Schofield in the procedures for hydrogenation and analysis. LITERATURE CITED (1) Bailey, A. E., IND. ENG.CHEM., 44, 990 (1952). (2) Blume, 11.C., private communication, July 21, 1952. (3) Covert, L. W., and Adkins, H., J . Am. Chem. Soc., 54, 4116 (1932).
(4) Freed, M. L. (to Seymour Mfg. C o . ) , U. 9. Patent 2,424,811 (July 29, 1947). (5) Goldstein, R. F., “The Petroleum Chemicals Industry,” p. 292, Kew York, John Wiley & Sons, 1950. ( 6 ) Hancook, C. K., IND.ENG.CHEX, 44, 1003 (1952). RECEIVED for review September 2, 1952.
ACCEPTED September 19, 1952.
Destruction of Phenols by
Oxidation with Ozone S. J. NIEGOWSICI Osone Processes Division, The Welsbach Corp., Philadelphia 29, P a .
I
N DRINKING water supplies the presence of even minute
amounts of phenol causes objectionable tastes and odors, which are greatly aggravated by the usual addition of chlorine for germicidal purposes. Phenol or phenolic compounds are common constituents of many industrial and commercial wastes and consequently find their way into drinking water supplies. Therefore, the problem of removing or destroying phenol in water or wastes is one of considerable importance to water works operators and sanitary engineers. Roth (17) and others have shown that ozonation of phenol produces compounds with relatively little or no odor a t the concenbrations involved; nor is odor produced upon subsequent application of chlorine for germicidal purposes. The general success of oxidative processes for the removal of phenolic tastes and odors at water-treatment plants is additional evidence that oxidation of phenol is a satisfactory means of eliminating it. Taste and odor considerations aside, a suitable phenol treatment process must not produce by-products toxic to stream life and should preferably result in the reduction of the chemical and biological oxygen demands. Toxicity studies (16) have shown that the ozone-oxidation reaction products are nontoxic and chemical oxygen demand and biochemical oxygen demand tests (16) have shown that oxidation to more or less complete removal of phenol brings about a substantial reduction in oxygen demands. Ozone has been proposed several times in the past fifty years as an oxidant for purifying phenolic wastes (IO). Patents have been issued for this purpose to both Leggett and Marechal (9, If). Until recently, however, ozone in quantity was not commercially available. In the past year or two efficient ozone-producing equipment of large capacity has become commercially available and ozone has become highly competitive in price with other common oxidants (6). Results of pilot plant tests on the destruction of phenols in an ammonia still waste, using ozone, chlorine, and chlorine dioxide as chemical oxidants, have been reported recently by the Ohio River Valley Water Sanitation Commission (16). This work was carried out a t the Hamilton, Ohio, plant of the Armco Steel Corp. Each of the oxidants tested was capable of destruction of phenols, but ozone treatment was demonstrated to be the most economical treatment process ( 1 , 7).
This paper presents additional information in the form of laboratory results on the oxidation of phenols and phenol-containing wastes. EXPERIMENTAL PROCEDURE
Laboratory ozonation studies were carried out on 500-ml. samples contained in a gas washing bottle equipped with a fritted-glass disk for dispersion of the gas into the liquid, The samples were treated with ozonized air of 1 to 2% ozone by weight produced from a Welsbach T-23 laboratory ozonator. A second gas washing bottle filled with 2q0 potassium iodide was used to trap exems ozone, if any. The volume of the ozonized air passed through the sample and the trap was measured with a wet-test meter. The concentration of the ozone in
PH
Figure 1. Effect of Initial pH on Oxidation of Phenolic Waste 0 320p.p.m.
Ozone applied X 430p.p.m.
0 680p.p.m.
w 360r
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
March 1953
I I
600
633
PHENOLIC WASTE OXIDATION CURVES FIGURE 3 X-THIOCYANATE *-CYANIDE 0-
PHENOL
x
OZONE, PPM
Effect of pH on Oxidation of Phenolic Waste
Figure 2.
0 pH7
X
pH 12
the ozonized air was determined by absorbing i n neutral 2% potassium iodide, acidifying, and titrating .with potassium thiosulfate solution. When a volume of ozonlzed air sufficient t o provide the required ozone dose had been passed through the sample, the flow of ozonized air was stopped and a portion withdrawn by pipet for analysis. Additional increments of ozone were applied t o the same sample until sufficient data were obtained for a complete oxidation curve, The ozone dose was based on the amount of ozone absorbed by the solution. The phenolic content was determined with 4-aminoantipyrine reagent (I,4, 6, 12, 18). Ammonium hydroxide was used to adjust the p H of the distilled sample and ammonium persulfate was the oxidant. The phenolic content of the waste is expressed as phenol. For cyanide and thiocyanate analysis the l-methyl3-phenylpyrazolone reagent as recommended by Epstein (3, 8) was employed; thiocyanate is converted by oxidation t o cyanide using dilute nitric acid for this purpose. The chemical oxygen demand test is based on oxidation with potassium dichromate in 50yGsulfuric acid (IS). EXPERIMENTAL RESULTS
d
OZONEDEMANDOF PHENOLIC COMPOUNDS.For the Iaboratory study of the ozone demand of phenols, 100 p.p.m. solutions were prepared with distilled water and the p H of the solutions was adjusted t o about 12. The results of these tests are presented in Table I. For total oxidation of pure phenol about 2 parts of ozone are required for each part of phenol. Phenolic wastes, on the other hand, exhibit higher ozone demand because of the presence of other oxidizable consituents. Experimental data on the ozone demand of various phenolic wastes plants are presented in Table 11. For the sake of comparison, the ozone demand is arbitrarily defined as that required for 99% removal of phenols. The residual phenols column indicated t h a t more than 99% removal of phenols was
TABLE I. OXIDATION OF PHENOLIC COMPOUNDS Phenol Ozone Phenol dosage, remaining, p.p.m. p.p.m. 96 0 54 47 12 110 0.4 180 0.2 220 0.1 260
o-Cresol Ozone o-Cresol ' dosage remaining, p.p.m. p.p.m. 0 99 49 49 11 100 1.7 150 0.2 200 0.1 240
m-Cresol Ozone m-Cre?ol dosage, remaining;, p.p.m. p.p.m. 0 99 57 41 110 2.7 I
150
200 260
0.4
0.0
0.0
OZONE,
PPM
attained in all the samples tested. The oxidation was not studied beyond this stage, but obviously additional increments of ozone would have caused additional reduction in concentration of residual phenols. ~
~~~
~~
OF PHENOLIC WASTES TABLE 11. OXIDATION
Initial Ozone Ozone/ Residual Phenols, Demand, Phenol Phenols Source P.P.M. P.P.M. Ratio P.P.M.' Coke plant A 1,240 2,500 2.0 1.2 Coke plant B 800 1,200 1.5 0.6 Coke plant C 330 1,700 6.2 1.0 140 Coke plant D 950 6.8 0.1 Coke plant E 127 550 4.3 0.2 Coke plant F 102 900 8.8 0.0 Coke plant G 51 1,000 20 04 Coke plant H 38 700 18 0.1 Chemical plant= 290 400 1.4 0.3 Refinery A 605 750 1.3 0.3 Refinery B 11,600 11,000 1.0 2.5 a This waste contained 2,4-dichlorophenol. Results are expressed as 2,4. dichlorophenol.
-
The great variation in the ozone-phenol ratios of samples from various sources illustrates the differences in the composition of the wastes. EFFECTOF pH. Pure phenols are easily oxidized by ozone over a wide p H range. However, in complex waste solutions, an adjustment of the initial p H will often favor oxidation of phenols. As an example, phenols in the effluents from the ammonia stills of coke-oven plants are readily oxidized b y ozone, A high p H favors phenol oxidation, presumably a t the expense of competing oxidation reactions. The curves of Figure 1 illustrate this effect and show that the optimum p H range for this particular cokeoven waste lies near p H 11.8. The effect of p H on the ozone demand of a second phenolic waste is demonstrated by the oxidation curves of Figure 2. I n this case, the ozone demand (99% oxidation) at pH 12 is only one half that of the ozone demand a t p H 7. Up t o 50% oxidation, however, the ozone-phenols reaction was still very rapid and pH adjustment had little if any effect. OXIDATION OF THIOCYANATE. Because the thiocyanate ion may be present in coke-oven plant waste in concentrations greater than the phenols, and its oxidation yields the highly toxic cya-
INDUSTRIAL AND ENGINEERING CHEMISTRY
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Vol. 45, No. 3
OZONE, PPM OZONE,
Figure 4.
Effect of Sulfide Removal on Oxidation of Phenolic Waste Untreated
X
Figure 5. @ X
Aerated
0
nide ion, the ozone oxidation of this constituent was studied. The reaction proceeds in two steps. First the thiocyanate is oxidized t o cyanide, and on completion of t h a t reaction, the cyanide is oxidized (to cyanate). These data indicate that 1 part of thiocyanate requires about 3 parts of ozone for oxidation to the cyanate stage. The high ozone demand of thiocyanate accounts for a considerable portion of the ozone demand of many of these wastes. Several coke-oven waste samples were studied not only for phenol oxidation, but also for thiocyanate and cyanide oxidation. Experimental results obtained with one such waste are presented in the curves of Figure 3. These curves are typical in the sense t h a t the cyanide content rises t o a maximum as oxidation of the thiocyanate proceeds. However, one waste studied showed atypical behavior; the oxidation of thiocyanate produced no increase in cyanide content. EFFECTOF SULFIDE. Phenolic wastes from petroleum refineries may contain significantly high concentrations of sulfide. Although the effect of sulfide removal by aeration on the ozone demand of a refinery waste has been demonstrated ( 1 4 ) , the curves of Figure 4 show a more pronounced reduction of the ozone demand of another refinery waste. REDUCTION OF CHEMICAL OXYGEN DEMAND AND COLOR. For the laboratory study of this effect, a 1000 p.p.m. solution of pure phenol wa5 prepared. The ozone oxidation was performed a t a p H of 12. The experimental data, presented by the chemical oxygen demand curve of Figure 5 , show that the reaction does not proceed completely t o carbon dioxide and water. Ozone continues to be consumed by the oxidation products of phenol, even when the phenol itself is completely destroyed. Phenol solutions become highly colored on partial oxidation with ozone; additional oxidation removes the color. The color of the solution was determined quantitatively with a KlettSummerson photoelectric colorimeter using a No. 40 filter (3800 t o 4300 A.). A maximum color is reached when about 1 mole of ozone per mole of phenol has been applied t o the solution. About one third of the phenol initially present still remains. Oxidation beyond this stage brings about proportional decrease in color. On complete phenol removal, the solution is practically colorless. The toxicity tests were carried out by TOXICITY OF PRODUCTS. the Academy of Natural Sciences (Philadelphia) (16). The organisms used in this study were blue gills, diatoms, and mayfly larvae, which were exposed t o both ozonated and untreated phenol solution, The initial phenol content of 200 p.p.m. was reduced b y ozone oxidation to about 0.1 p.p.m. The biologically
PPM
Phenol Oxidation Curve
Chemical oxygen demand, p.p.m. Phenol, p.p.m. Color, arbltrary units
safe concentration of phenol with respect t o all these organisms determined to be 2.7 p.p.m. The ozonated phenol solution produced no toxic effect on any of the organisms.
WEB
CONCLUSION
Oxidation with ozone, when preceded by proper pretreatment, appears to provide an economical solution t o the problem of destruction of phenols in a variety of industrial wastes. Most of the wastes studied required a t the most only a n adjustment in the initial p H as a pretreatment t o the oxidation process. Refinery or other wastes with high sulfide content may require preaeration for sulfide removal. B y destruction of phenols and oxidation of thiocyanate and cyanide a marked reduction in toxicity of such wastes can be realized. As the treatment process is oxidative, the chemical oxygen demand of the wastes is also decreased. LITERATURE CITED
Chem. Eng., 58,224-8 (September 1951). Dannis, M., Sewage d I n d . Wastes, 23, 1516-22 (1951). Epstein, J., A n a l . Chem., 19, 2 7 2 4 (1947). Ettinger, hf. B., Ruchhoft, C. C., and Lishka, R. J., Ibid., 23,
1783-8 (1951). Gottlieb, S., and Marsh, P. B., IND.ENG.CHEM.,rl1.7~~.ED., 18, 16-19 (1946). Hann, V. A., Chem. Inda., 6 7 , 386-9 (1950). Hann, V. A, “Complete Destruction of Phenol in Coke-Oven Waste,” paper presented a t Western Regional Meeting, American Coke and Coal Chemicals Institute, Chicago, Ill., March 7. 1951. Kruse, J. h.,and Mellon, &I. G., Sewage & I n d . Wastes, 23, 1402-7 (1951). Leggett, U. S. Patent 1,341,913 (1920). Lowry, H. H., “Chemistry of Coal Utilization,” Vol. 2, p, 1466. New York, John Wiley & Sons, 1947. Marechal, French Patent 350,879 (1905). Martin, R. W., A n a l . Chem., 21; 1419-20 (1949). Moore, W. A4., Kroner, R. C., and Ruchhoft, C. C., Ibid., 21, 953-7 (1949). Murdock, H. R., ISD. ENG. CHEM.,43, 125A (November 1951). Ohio River Valley Water Sanitation Commission Report, “Phenol Wastes, Treatment by Chemical Oxidation,’’ June 15, 1951. Patrick, R., Academy of Natural Sciences of Philadelphia, private communication, June 12, 1951. Roth, W., “Ozonation of Phenol in Water Solution,” M.S. thesis, New York University, 1947. Shaw, J. A., A n a l . Chem., 23, 1788-92 (1951). RECEIVED for review August 9. 1952.
ACCEPTED December 4, 1952.
