Treatment of Coke Plant Wastewater for Oil Removal Using Solid Carriers Treated with a Cationic Surfactant
Abstract Generated abstract
The paper examines flotation treatment of coke plant wastewater containing oils, resins, phenols, pyridine bases, and other impurities that hinder conventional oil removal because part of the oil is present in dissolved rather than emulsified form. It proposes using quartz particles pretreated with the cationic surfactant aminonitroparaffin as a reusable hydrophobic carrier, aiming to extract oil into the froth while limiting surfactant transfer to water that must later undergo biological treatment. Experiments at pH 9 and 20°C with an initial oil content of about 0.57 g/l showed oil removals of 76 to 81 percent over repeated quartz loadings, indicating the practical feasibility of the carrier-assisted flotation approach.
Full Text
Treatment of Wastewater from a Coke-Chemical Plant for Oils Using Solid Supports Treated with a Cationic Surfactant
S. A. Babenko, L. F. Prosekova
(Presented by the scientific seminar of the departments of PMKhP and OKhT)
The flotation method has found wide application for treating wastewater to remove emulsified particles of petroleum, resins, and oils, since it has the following advantages: 1) flotation machines, while occupying a small area, have high capacity; 2) capital and operating costs are low; 3) maintenance is simple. However, for the treatment of wastewater from coke-chemical plants to remove oils, this method has not yet found application because of the special physical state of the oil in wastewater, determined by the impurities present in it. In particular, the wastewater of the Kemerovo coke-chemical plant contains the following substances (in g/l): phenols—0.22, cyanides—0.16, rhodanides—0.5, pyridine bases—0.145, naphthalene—0.021, resins—0.071, oils—0.588 (analysis of wastewater at the end of December 1969). The water contains a large amount of mineral impurities, and the pH of the water is 9. The considerable alkalinity and the presence of phenols and pyridine bases, which possess hydrotropic properties [1], promote the transfer of part of the oil into a truly soluble form. Therefore, flotation treatment methods, which give high results when the oil is present in the form of an emulsion, will be of little effectiveness for that part of the oil which is in dissolved form.
Table 1
Results of flotation treatment of wastewater with quartz (particle size—10 mm), preliminarily treated with ANP
(pH = 9, temperature 20°C, initial oil content 0.57 g/l)
| Order of quartz loading | Oil content in treated water, g/l | % removal |
|---|---|---|
| 1 | 0.095 | 81 |
| 2 | 0.107 | 79 |
| 3 | 0.113 | 77 |
| 4 | 0.120 | 76 |
To increase the extraction of oil into the froth product, it is proposed to add to the wastewater a cationic surfactant—aminonitroparaffin (ANP).
ANP ensures a reduction of the oil content to the required limits, which was verified by studies on several samples of the plant’s wastewater. But since ANP has bactericidal properties, in the event of its accumulation in the water the latter will not undergo biological treatment. In this connection, using the ability of ANP
not be desorbed from the surface of minerals in an alkaline medium [2], experiments were conducted on treating wastewater with quartz that had been preliminarily treated with an amine. Such quartz readily passes into the froth, adsorbing oil on its surface. A certain amount of water also passes into the froth; after it is separated from the quartz, the latter is again charged into the flotation machine with a fresh portion of water. Thus, the same quartz (once treated with ANP) was used as a hydrophobic additive in order to achieve more complete extraction of oil from the wastewater.
The ratio of solid to liquid in the flotation cell was 1 : 2. The results of the experiments (Table 1) indicate the fundamental possibility of such treatment of water to remove oils. The consumption of ANP in this case was 180 mg/l of wastewater (determined from the amount of amine fixed on the surface of the quartz).
Thus, to reduce the transfer of ANP into the water being treated, flotation using supports treated with a cationic surfactant may be recommended.
REFERENCES
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L. A. Polster. Physicochemical Features and Hydrogeological Factors of the Migration of Natural Solutions. Nedra, Moscow, 1967.
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V. I. Klassen, V. A. Mokrousov. Introduction to the Theory of Flotation. Gosgortekhizdat, Moscow, 1959.