Determination of oil content in fishery ship management by ultraviolet spectrophotometry - Master's thesis - Dissertation

UV spectrophotometric determination of oil content in fishery ship management Keywords: UV-visible spectrophotometer; oil content determination; US instrumentation ; fishery; ship; UV-1100; UV-12001 determination of oil content The practical significance in the management of fishing vessels With the outward migration of fisheries and the rise of offshore fishing, the production of fishing vessels has grown in the direction of large-scale. The large-scale fishing boat has improved the ship's ability to withstand wind and waves, and has produced good economic and social benefits, but it has also increased the discharge of engine room wastewater, so that a large amount of diesel engine oil random tank wastewater enters the sea area and causes marine pollution. To this end, the state stipulates that: "New fishing vessels of 400 gross tonnage and above should be equipped with sufficient oil and water filtration equipment." At present, the fishing vessels of the National Fisheries Corporation and the ocean-going vessels are equipped with oil-water separators on board. The cabin wastewater is treated by the oil-water separator to remove most of the oil in the sewage. However, due to the difference in installation, operation and use time of the oil-water separator, the wastewater treatment effect is very different. In this regard, the state continues to stipulate: "Oil-containing sewage discharged by fishing vessels should not exceed 15g/m.

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In order to measure whether the oil-water separation effect of each fishing vessel meets this requirement, the oil content of the newly built or over-repaired ship must be measured, and a qualified certificate for the requirements must be issued, and finally issued by the fishing vessel inspection department. The effective Fisheries Ship Oil Pollution Prevention Certificate is approved for operation.
According to the basic characteristics of fishing vessels, we have gained some experience through comparison and screening, and further exploration of the application of the method. It is organized as follows to communicate with colleagues.
2 Determination of the method of determination of the oil sample in the water sample method is more common, commonly used by gravimetric method, non-dispersive infrared method, fluorescence method and ultraviolet spectrophotometry. After comparing these methods, we believe that although the gravimetric method is commonly used, the operation is cumbersome, the sensitivity is low, the detection limit is high, and the precision of the measurement varies greatly depending on the experimental conditions and the proficiency of the personnel; non-dispersive Although the infrared method is ideal, it requires a special non-dispersive infrared oil detector to increase the investment. Although the method is sensitive, the measurement range is too narrow, and the fluorescence photometer is required. The equipment investment is too large. Ultraviolet spectrophotometry better compensates for the defects of the above three methods, not only simple operation, good precision, moderate detection range, and the measurement wavelength is in the range of 215 ~ 260nm, general laboratory spectrophotometer UV -1100; UV-1200, easy to use. Therefore, it is appropriate to use ultraviolet spectrophotometry to determine the oil content of fishing boats.
3 Solvent selection The oil extraction solvent requires a small response at the measurement wavelength and oil characteristic absorption peak. Generally, petroleum ether, carbon tetrachloride, n-hexane, etc. can be used. In order to choose a suitable solvent, we compare the dearomatization conditions and toxicity of the above three solvents as follows:
3.1 Petroleum ether: It is a mixture of pentane and hexane. At present, the analytically pure petroleum ether is commercially available, and its light transmittance is often less than 80%. It needs to be dearomatized to meet the experimental requirements, while the optical pure petroleum ether has a light transmittance that meets the requirements, but the used waste liquid must also be re-aromatically dearomatized. deal with. The dearomatization of petroleum ether requires a special set of equipment and is complicated to operate. For ordinary laboratories lacking this dearomatization condition, it is not suitable to use petroleum ether as a solvent.
3.2 Carbon tetrachloride: Commercially available carbon tetrachloride can be directly used for extraction determination, rarely purified, and its waste recovery is much simpler than petroleum ether. However, carbon tetrachloride is highly toxic, and long-term excessive exposure can cause serious damage to the liver and kidney, and cause contact skin inflammation. The International Cancer Institute has classified it as a human suspected chemical carcinogen, and many laboratories have phased out carbon tetrachloride as an extraction solvent.
3.3 n-hexane: also toxic, reported to be at 5000g / m

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Acute poisoning occurs when the symptoms are dizzy. It can irritate the mucous membranes of the eyes, nose and throat at high concentrations and has an anesthetic effect, but after all, its toxicity is lower than that of carbon tetrachloride. Moreover, it is a kind of petroleum ether component. As a pure compound, its dearomatization condition is much simpler than petroleum ether. No need to add new equipment, and purification can be achieved by using common equipment. From the above comparison, we believe that it is more appropriate to select n-hexane as the measurement solvent.
4 Purification of n-hexane and waste liquid recovery UV spectrophotometry specifies the solvent used for the determination. The light transmittance must be ≥80%. However, the commercially available stock solution and the measured waste liquid contain aromatics and contain impurities. The light rate is often less than 10%, far less than the measurement requirements, for which dearomatization purification treatment is required. In the absence of activated carbon activation and column dearomatization, we separately tested the commercially available stock solution and the measured waste liquid by water washing, distillation, sulfonation and sulfonation + distillation. The results are as follows:
4.1 Treatment of raw liquid
4.1.1 Washing: Distilled water was added to commercially available n-hexane, placed on a magnetic shaker and thoroughly shaken for 1 hour, the aqueous phase was discarded, and the light transmittance was measured. The above operation was repeated 3-4 times, and its light transmittance was increased from 4 to 7.3% to 10%. It indicates that the water washing can only remove the water-soluble substances in the reagent, but not the aromatic hydrocarbons in the reagent.
4.1.2 Distillation: The boiling point of n-hexane is 68.724 °C. When the temperature of the water bath is maintained at about 81 ° C, the temperature of the fraction of the distillation apparatus substantially reaches its boiling point. After distillation, its light transmittance is only about 32.4%. Explain distillation. Only some impurities can be removed, and it cannot be used as a fundamental method to increase the light transmittance.
4.1.3 Sulfonation: a certain amount of sulfuric acid is added to the n-hexane reagent, that is, the sulfo group (-SO3H) is introduced, and the hydrocarbon in the reagent is sulfonated with sulfuric acid, and then the sulfuric acid phase and the n-hexane are layered. The funnel was separated. The operation was repeated twice, so that the sulfurized sulfuric acid phase became substantially colorless. The light transmittance was measured separately, the first time was 31.4%, and the second time was 31.9%. It is indicated that the dearomatization effect is better after the sulfonation reaction. However, impurities still exist in the reagent and need to be purified.
4.1.4 Sulfonation + Distillation: The hexane after sulfonation dearomatization is further distilled, and the light transmittance is measured, which is obviously improved, generally up to 87.9% to 89.1%. It is indicated that the aromatic hydrocarbon is removed after the sulfonation reaction, and after distillation, the remaining impurities are also removed. Not only the reagents have met the measurement requirements, but also the operation is simple and the device is single, which can be used as a basic method for improving the transmittance of the commercially available raw liquid.
4.2 Waste liquid recovery and purification The waste liquid after the measurement is generally less than 10% due to the mixing of oils and impurities. In order to effectively utilize existing resources and save monitoring costs, we also perform the same recovery on the measurement waste liquid. As a result of the test, it was found that the light transmittance of the sulfonation reaction was only 30 to 40% after 3 to 4 times. If sulfonation is carried out and then distilled, the light transmittance can be increased to 95%. Sometimes, without direct sulfonation distillation, the light transmittance can be as close as 80%. This is mainly determined by the level of oil in the tested water sample. For low oil content water samples, the waste liquid recovery method can be directly distilled, while for high oil content water samples, the waste liquid is subjected to double recovery by sulfonation and distillation. The effect is better.
5 The standard method of photometric method is a relative analysis method. For quantitative determination, a standard curve must be used to draw a standard curve. However, since oil is a substance that constitutes a complex change, problems arise in the selection of standard materials. If the "standard oil" is extracted one by one, the measurement results can truly reflect the actual situation of oil pollution. It is theoretically correct, but it is too cumbersome and has a large workload. It lacks practical operability in practical applications. Used for monitoring of some major oil sources such as refineries. The oil extracted from a certain ship sample is used as a "standard oil", which is lack of representativeness. In order to facilitate the uniform implementation of the standard, considering the comparability of the measured data in the monitoring network, we believe that it is relatively reasonable to use the standard oil uniformly distributed by the monitoring network for routine monitoring. To this end, we selected the Marine Environmental Monitoring Standard Oil 20-3#, which was prepared by the National Ocean Monitoring Center, as the standard oil for this application.
6 Selected oils of suitable wavelengths and their products have characteristic absorption in the ultraviolet region. The aromatic compound with a benzene ring has a main absorption wavelength of 250 to 260 nm, and the compound having a conjugated double bond mainly absorbs at a wavelength of 215 to 230 nm, and the two absorption wavelengths of a general crude oil are 225 and 254 nm, and other oils such as fuel. Oil, lubricating oil and other absorption peaks are similar to crude oil. The characteristic absorption peaks of different oils are inconsistent, and there are certain wavelength errors between different instruments. In order to make the measurement results have higher sensitivity and accuracy, we tested the maximum absorption wavelength to obtain the maximum absorption peak of the standard oil 20-3# at the wavelength λ=226 nm. It was determined that the operating wavelength of the application was 226 nm, and the spectrophotometer UV-1100; UV-1200.
7 Drawing of the working curve Take 7 50ml volumetric flasks and add a certain amount of standard oil solution (concentration is 100g/m)

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Diluted to the mark with n-hexane, with the aid of a spectrophotometer UV-1100; UV-1200, using a 10 mm cuvette at a wavelength of λ = 226 nm, with n-hexane as a reference, the absorbance was measured as follows: No. 1 2 3 4 5 6 7 Standard oil use liquid ml number 0 2.0 4.0 8.0 12.0 20.0 25.0 Oil content mg ​​0 0.2 0.4 0.8 1.2 2.0 2.5 Absorbance 0 0.108 0.163 0.305 0.442 0.752 0.917 The data of No. 3-7 was input into the spectrophotometer UV-1100; the regression equation of the working curve obtained by the UV-1200 calculation system was C=275.3A-3, and the correlation coefficient γ=0.9997. From the obtained correlation derivative γ=0.9997, the production error of the working curve is extremely small, and the linearity of each data is good, which can be used as a standard curve for actual measurement.
8 For Ning Yu 619

#

620

#

621

#

622

#

The actual measurement of the fishing boat is based on the UV spectrophotometric method. The oil in a sufficient amount of water is extracted multiple times with n-hexane; the extracts are combined. The extract was filtered and dehydrated with anhydrous sodium sulfate, and the volume was adjusted. At a wavelength of λ=226 nm, a light-absored value A was measured using a 10 mm quartz cuvette with n-hexane as a reference, and a blank test was performed.
Got A

619

=0.401 A

620

=0.419 A

621

=0.161 A

622

=0.144 A

air

=0.018
Data input 751-GW computing system, get M

619

=107Mg M

620

=111Mg M

621

=41Mg M

622

=36Mg from the volume of water sample taken, the oil content of the above four ships is calculated to be 10.6g/m

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11.0g/m

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4.0g/m

3

3.6g/m

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Obviously the oil content in these water samples is less than 15g/m

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According to the results of this measurement, the ship inspection department can determine that the oil-water separators of the above four ships have good performance and comply with the relevant national regulations, and issue the corresponding Fisheries Ship Oil Pollution Prevention Certificate for the host of the ship.
9 Conclusion Under ordinary experimental conditions, it is ideal to use UV spectrophotometry to determine the oil content in the cabin waste water of fishing vessels. Especially after the combination of sulfonation and distillation to improve the purity of the solvent, the traditional ultraviolet spectrophotometry is more practical and more operable. Key words: UV-visible spectrophotometer; oil content determination; US instrumentation ; fishery; ship; UV-1100; UV-1200