Study of the physicochemical properties of oil in wastewater from a coke-chemical plant
Abstract Generated abstract
This study examines the physicochemical state of coal-tar oil in wastewater from a coke-chemical plant, where oil is present alongside phenols, pyridine bases, sulfates, ammonia, chlorides, and other dissolved substances under alkaline conditions. Using dialysis through a parchment membrane over 23 days, the authors assessed whether the oil existed in dissolved or emulsified form. The results indicated that about 96 percent of the oil passed into the dialysate, suggesting that most of it was dissolved, while only a small fraction remained emulsified. Electrophoresis showed negatively charged oil particles, leading the authors to conclude that conventional filtration or settling would be ineffective and that extraction using cation-active substances may be a more suitable treatment approach.
Full Text
STUDY OF THE PHYSICOCHEMICAL PROPERTIES OF OIL IN WASTEWATER FROM A COKE-CHEMICAL PLANT
L. F. Prosekova, S. A. Babenko
Coal-tar oil dispersed in the wastewater of coke-chemical plants is one of the most harmful pollutants. Its content in the wastewater studied ranges from 1.2 to 0.6 g/L. In addition to oil, the water contains phenols, pyridine bases, sulfates, ammonia, chlorides, and other substances; the pH of the water is 8.6–9.0.
The presence of the substances listed above, especially phenols and pyridine bases, which have a hydrotropic effect, gives the water the ability to dissolve oils in increased quantities [1, 2].
To confirm the presence of oil in the wastewater in the dissolved state, dialysis of the wastewater was carried out.
The dialysis method is one of the old methods of colloid chemistry, used to separate the dispersed phase from the dispersion medium.
In dialysis, a colloidal solution with impurities of truly dissolved substances contained in it is separated from the pure solvent by a semipermeable membrane. Molecules and ions capable of passing through the membrane diffuse into the solvent; by periodically replacing it, the colloidal solution can be practically completely purified of impurities. As a simple dialyzer for purifying the colloidal solution (in our case, wastewater), we used a vessel in which the bottom had been replaced by a membrane made of parchment.
Into the dialyzer vessel, 250 ml of wastewater subject to purification was poured, after which the vessel was immersed in a crystallizer filled with distilled water. The water level in the crystallizer
was maintained constant. The first analysis of samples for oil content from beneath the dialyzer was carried out after 7 days; the next three samples were analyzed after three days each; the final analysis of the fifth sample was carried out after another 7 days. In all, the analysis continued for 23 days. The wastewater remaining in the dialyzer was analyzed for the oil content in it. The wastewater analysis data are given in Table I.
Table I
Dialysis of wastewater
| Sample no. | Dialysis time, days | Amount of oil transferred into the water, g | % of oil transferred into the water | Residual oil content in the wastewater after dialysis, g/% |
|---|---|---|---|---|
| 1 | 7 | 0,0226 | 32,3 | |
| 2 | 10 | 0,0153 | 21,9 | |
| 3 | 13 | 0,0156 | 22,3 | |
| 4 | 16 | 0,0081 | 11,5 | |
| 5 | 23 | 0,0059 | 8,4 | 0,0016 / 2,4 |
| 0,0675 | 96,4 |
As is evident from Table I, the greater part of the oil (96%) is contained in the water in a dissolved state. The remaining part of the oil is emulsified. The electrophoresis method established the negative charge of the oil particles. It does not appear possible to separate from wastewater an oil having such a physical composition by the usual physicomechanical method (filtration, settling).
For extracting oil from water, a highly effective method using cation-active substances is proposed.
Literature
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N. Gerber. Solubility of Hydrocarbons as a Factor in the Primary Migration of Oil. Moscow, “Nedra,” 1958.
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L. A. Polster. Physicochemical Features and Hydrogeological Factors in the Migration of Natural Solutions. Moscow, “Nedra,” 1967.