RU2164024C2 - Process determining content of petroleum products in water - Google Patents

Abstract

FIELD: oil industry. SUBSTANCE: process id related to determination of content of petroleum products in natural water and sewage of various enterprises such as oil producing and refining plants, gas-filling stations, etc. Proposed process determining content of petroleum products in water includes three-phase concentration of petroleum products by passage of polluted water through cartridge filled with sorbent on base of silicon dioxide, elutriation, removal of hampering impurities and measurement of content of petroleum products in eluate. In the capacity of sorbent there is proposed to use superfine quartz fibrous material with amorphous structure having specific surface of 2.0 sq m/g and characterized by following distribution of fibers by diameter ( per cent by mass ): 0,0-0,5 mkm-7-14; 0,5-1,0 mkm-31-48; 1,5-2,0 mkm-5,6-22,5; 2,0-2,5 mkm-5,1-8,5; 2,5-3,0 mkm-2,1-7,6; 3,0-3,5 mkm-2,1-2,5; 3,5-4,0 mkm-2,8-3,6; 4,0-4,5 mkm-1,4-2,5; 4,5-5,- mkm-2,1-2,5; 5,0-5,5 mkm-0,7-2,0; 5,5-6,0 mkm-0-0,5; 6,0-6,5 mkm -0-0,7; 6,5-7,0 mkm -1-1,4. EFFECT: improved accuracy in determination of content and possibility of usage of sorbent many times. 7 cl, 8 tbl

Description

 The invention relates to the field of analytical chemistry, in particular, to the determination of the content of petroleum products (NP) in natural and waste waters, including the wastewater of various enterprises (oil producing and refining, gas stations, etc.).

 A known method for the determination of NP in water, which includes the following stages: concentration by liquid-liquid extraction using carbon tetrachloride as an extractant, separation of substances that interfere with the determination of substances by passing the extract through an alumina column and IR spectrophotometric determination [1]. This method is the basis of the industry standard OST 38.01378-85.

 A similar method for the determination of NP in water has such disadvantages as a large investment of time for each determination (from 1.5 to 4 hours) and a significant consumption of an organic solvent, because for the study of one aqueous sample it is necessary to extract it three times with 15 portions of the solvent -30 ml. In addition, during the extraction concentration of NPs from water in the presence of surface-active substances (SAS), stable emulsions can form, which makes it impossible to separate phases by sedimentation and analysis. A highly toxic carbon tetrachloride is used as an extractant.

 Chromatographic and mass spectrophotometric methods for determining NP in water are also known [2-4], but these methods require the use of expensive instruments.

Closest to the proposed method for determining the content of NP in water is a method based on the concentration of organic compounds on chemically modified silicas [5]. Chemically modified silicas (CMC) are a matrix of silicon dioxide (SiO ₂ ), to the surface of which are attached one or another inorganic, organic and organometallic compounds. To concentrate organic compounds from aqueous media, alkyl CMCs are most widely used, in which the modifying layer is bonded to the silica surface by a Si – O – Si or Si – C bond system. The advantages of CMCs include a high rate of establishment of adsorption equilibrium, mechanical strength and non-swelling of particles, ease and completeness of elution of concentrated compounds with small volumes of solvents. These advantages of CMC are used in solid phase extraction cartridges, the use of which reduces the consumption of solvents and reagents and increases the degree of extraction compared to other concentration methods.

If the substance of interest should be concentrated selectively (interfering substances must pass through the cartridge), then the sorbent must be conditioned with a solvent. For alkyl CMCs, methanol is used [5]. This operation is required, otherwise the properties of the sorbent may not be reproducible. Then water is passed through the sorbent, then the sample, keeping the flow rate constant (usually 200 ml / min · cm ² ). Next, the sorbent is washed with a solvent that dissolves interfering substances well, but poorly analyzed. In this case, interfering substances elute. The finally determined compound is quantitatively eluted with a strong solvent in a minimal volume, the solvent is distilled off or the eluate itself is used.

The disadvantages of the prototype include:
- the possibility of destruction of the grafted alkyl layer as a result of repeated use, deterioration due to this sorption properties and lower accuracy of the analysis;
- the need for conditioning the sorbent with toxic methyl alcohol and the use of special organic solvents to remove interfering impurities, which increases the duration of the analysis, leads to increased consumption of solvents and worsens working conditions;
- the presence of a grafted layer eliminates the oxidative regeneration of CMC.

 The objective of the present invention is to reduce analysis time, increase the accuracy of determination with repeated use of the sorbent, the exclusion of the use of toxic solvents and the reduction of solvent consumption.

 The problem is solved by the proposed method for determining the content of petroleum products in water, including solid-phase concentration of petroleum products by passing contaminated water through a cartridge filled with a sorbent based on silicon dioxide, regeneration of the sorbent, removal of interfering impurities and measuring the content of petroleum products, in which according to the invention as a sorbent in solid-phase concentration use superthin quartz fibrous material with an amorphous structure with a fiber diameter of up to 0.5 μm 7 -14 wt.%, With a diameter of 0.5-1.0 microns 31-48 wt.% And not more than 7 microns - the rest.

In preferred embodiments:
- use a superthin quartz fibrous material with an amorphous structure having a specific surface area of 2 m ² / g and characterized by the following distribution of fibers by diameters (wt.%): 0.0-0.5 microns - 7-14; 0.5-1.0 microns - 31-48; 1.5-2.0 microns - 5.6-22.5; 2.0-2.5 microns - 5.1-8.5; 2.5-3.0 microns - 2.1-7.6; 3.0-3.5 microns - 2.1-2.5; 3.5-4.0 microns - 2.8-3.6; 4.0-4.5 microns - 1.4-2.5; 4.5-5.0 microns - 2.1-2.5; 5.0-5.5 microns - 0.7-2.0; 5.5-6.0 microns - 0-0.5; 6.0-6.5 microns - 0-0.7; 6.5-7.0 microns - 1-1.4;
- regeneration is carried out by treating the sorbent with freons selected from the range of 1,2,2-trifluoro-1,1,2-trichloroethane, tetrafluorodibromoethane;
- the removal of interfering impurities is carried out by passing the eluate after regeneration through a column filled with a sorbent selected from the series aluminum oxide, magnesium oxide, magnesium silicate and / or ion exchanger;
- the removal of interfering impurities is carried out by passing water through a cartridge filled with superthin quartz fibrous material and a sorbent selected from the range of cation exchangers, anion exchangers placed below or on top of the superthin quartz fibrous material;
- determination of petroleum products is carried out at a pH of contaminated water 2-7;
- the regeneration of superthin quartz fibrous material is carried out by thermal oxidation and the determination of petroleum products is carried out by the amount of carbon dioxide formed;
- superthin quartz fibrous material with an amorphous structure after passing water is subjected to x-ray radiometric analysis to determine the elemental composition of petroleum products.

The essence of the method is as follows: the concentration of petroleum products from contaminated water is carried out by passing through a cartridge filled with a sorbent, superthin quartz fibrous material (SCRM) with an amorphous structure (TU-6-11-15-15-191-81). The specific surface of the material used as a sorbent in the proposed method is 2 m ² / g, fiber diameter distribution (wt.%): 0.0-0.5 microns - 7-14; 0.5-1.0 microns - 31-48; 1.5-2.0 microns - 5.6-22.5; 2.0-2.5 microns - 5.1-8.5; 2.5-3.0 microns - 2.1-7.6; 3.0-3.5 microns - 2.1-2.5; 3.5-4.0 microns - 2.8-3.6; 4.0-4.5 microns - 1.4-2.5; 4.5-5.0 microns - 2.1-2.5; 5.0-5.5 microns - 0.7-2.0; 5.5-6.0 microns - 0-0.5; 6.0-6.5 microns - 0-0.7; 6.5-7.0 microns - 1-1.4.

 The regeneration of superthin quartz fibrous material is carried out by elution with a non-toxic solvent belonging to the class of freons, for example, 1,2,2-trifluoro-1,1,2-trichloroethane (HFC 113) or tetrafluorodibromoethane (HFC 114B2). The influence of organic compounds, such as surfactants, which interferes with determination, is eliminated by controlling the pH of contaminated water during solid-phase extraction in the range from 2 to 7 and using special sorbents. To remove impurities that interfere with the determination of impurities from the eluate, depending on their type, sorbents such as aluminum oxide or magnesium oxide and / or ion exchanger, for example KU-23, AN-21, can be used. In order to reduce analysis time and reduce solvent consumption, the concentration of petroleum products from water and the separation of substances that interfere with determination can be combined by placing a sorbent to remove interfering impurities in the cartridge for solid-phase concentration of petroleum products from below or on top of a sorbent based on a superthin quartz fibrous material with an amorphous structure (location sorbent for removing interfering impurities in the lower or upper part of the cartridge depends on the type of impurity). The actual determination of oil products in the eluate can be carried out, for example, by IR spectrophotometric method.

 The proposed method also allows for the concentration of organic compounds obtained before and after separation interfering with the determination of substances to obtain separately the content of polar (for example, surfactants) and non-polar organic compounds.

The use of SCR as a sorbent for solid-phase extraction of NP from water makes it possible to determine the total content of organic carbon by the amount of carbon dioxide released during thermo-oxidative regeneration (at 500-700 ^° C), while the material itself retains its structure due to thermal stability and mechanical strength and sorption properties.

Since SCR is pure quartz (SiO ₂ ), determining the elemental composition of NPs extracted from aqueous samples, for example, the Ni / V ratio, by X-ray analysis, it is possible to identify the type and origin of NPs and / or determine the source of environmental pollution.

 The following are examples illustrating the method.

 Example 1. Model wastewater is prepared by introducing a certain amount of I-20 oil in 250 ml of distilled water, placed in a separatory funnel. Water contaminated with oil is passed at a constant speed through a glass cartridge, 15 mm in diameter, filled with 1 g of superthin quartz fibrous material (SCRM). The height of the SCWM layer is 5 cm. The regeneration of the SCWM is carried out by eluting the oil concentrated with SCWM with a solvent - Freon 113. First, a separatory funnel is rinsed with 5 ml portions of each, and then the cartridge with the SCRM is washed with the same portion of solvent from the separatory funnel. This operation is carried out three times. The eluates are combined and the content of I-20 oil is determined in the final eluate on a Specord 75 IR IR spectrophotometer (the stage of separation of interfering impurities from the eluate is omitted, since they were not introduced into the model mixture. This stage is necessary for analyzing water of unknown composition).

The results of the determinations are presented in table. 1 and 2, where the root-mean-square deviations (S) and the values of Student's criteria t _{1 are given} for the probability P = 95%.

 The data presented in table. 1 and 2, show that SCWM has a good sorption capacity with respect to NPs of type I-20 oil. When the concentration of NP in water is up to 30 μl / 250 ml, the optimal filtration time is 6–7 min, which corresponds to a filtration rate of 35.7–41.7 ml / min.

 Example 2. The experimental conditions are the same as in example 1. Freon 113 and carbon tetrachloride are used as extractants. Petroleum products are a standard mixture (37.5% vol. Cetane; 37.5% vol. Isooctane and 25% vol. Benzene), gasoline, kerosene and I-20 oil. Measurements are carried out in parallel on Specord-75 IR and IKAN-1 devices (infrared oil analyzer manufactured by AOOT Zagorsk Optical and Mechanical Plant).

The results presented in table. 3 show that the concentration values obtained in parallel measurements on Specord-75 IR and IKAN-1 instruments practically coincide, as evidenced by the values of the Fisher test and t-test (F _exp <F _table , t _1.2 <t _table ) Based on the data table. 3, one can judge about satisfactory correctness (the error in determining Δ does not exceed 11%) and reproducibility of the method (relative standard deviation S _r = 0.1-0.19). As follows from the table. 3, only when determining kerosene t ₁ > t _tab , which indicates a systematic error (underestimation) of the determination results, however, this underestimation is significantly less when eluting oil from the cartridge with chladone 113 than when eluting with CCl ₄ . The underestimation of the results of the determination of kerosene in water is associated with the evaporation of volatile fractions during the experiment.

Example 3. In the table. 4 shows experimental data to compare the method for determining NP in water, based on liquid-phase extraction concentration of NP (according to OST 38.01378-85), and the proposed method. Model contaminated water contained 10 μl of the standard mixture in 250 ml of distilled water. The number of experiments for each method n = 10. The experimental conditions correspond to example 1. The average values of the found concentrations (C _av ) of the standard mixture are expressed in μl / 250 ml of water.

 As can be seen from the table. 4, at a concentration of a standard mixture of 10 μl / 250 ml of water, the results of the determination are somewhat underestimated, due to the evaporation of volatile benzene, which is one of the components of this mixture. The total measurement error (Δ), as can be seen from the table. 4 does not exceed 7% for the proposed method for determining oil products, which indicates a high accuracy of the method.

 Example 4. In the table. 5 presents the results of the determination of various NPs in water by the proposed method using various sorbents for solid-phase extraction of these NPs from water. Model contaminated NP water contained 1 μl of oil in 250 ml of distilled water. The number of experiments for each case is n = 10. The average NP concentration found in water is expressed in μl / 250 ml of water. DIAPAK - cartridges for solid-phase extraction of petroleum products containing KMK as a sorbent (prototype).

 As can be seen from the table. 5, SCWM in its sorption properties with respect to NP is not inferior to the sorbent in DIAPAK cartridges. However, SCRM retains its sorption properties during 500 cycles of sorption-desorption, and the sorption properties of DIAPAC fall after 10 such cycles.

 Example 5. In the table. Figure 6 presents the results of determining a standard mixture and I-20 oil in water in the presence of nonionic (OP-10, neonol AF9-10), anionic (sodium dodecyl sulfate - abbreviated as DDS) and cationic (alkamon or OS-2) surfactants (Surfactant) at pH 2 and pH 7. For each type of surfactant and the pH of the aqueous medium, 10 experiments were performed.

 Model contaminated NP and surfactant water contained 1 μl of oil and 0.25 mg of the corresponding surfactant in 250 ml. The prepared water was passed through a column filled with 1 g of SCWM (sorbent layer thickness 5 cm) to concentrate petroleum products. SQMs were regenerated by eluting petroleum products with three portions of Freon, 5 ml each. The eluate was passed through a column with a sorbent (aluminum oxide) to separate interfering determination of substances (surfactants). In the eluate purified from interfering with the determination of impurities, the content of petroleum products was determined by IR spectrophotometry.

 The data table. 6 show that the use of alumina to separate interfering substances in most cases leads to an improvement in the results of determination of petroleum products.

 Example 6. The effect of non-ionic (eg, neonol AF9-10) and cationic (eg, OS-2) surfactants on the results of determination of NP in water by the proposed method when they are concentrated by solid-phase extraction in a cartridge filled with 1-5 g SCRM and 2-10 g of cation exchanger KU-23 (cation exchanger was placed on top of the SCRM layer) at pH 2 and pH 7, are presented in table. 7. Model wastewater contained 1 μl NP (standard mixture) and the corresponding surfactant. The number of experiments for each case is n = 5. The sorbent was regenerated by elution with freon, the determination of oil products in the eluate was carried out by IR spectrophotometric method.

 Based on the data table. Figure 7 shows that the use of cation exchanger in a concentrating cartridge together with SCRM eliminates the interfering effect of the nonionic surfactant neonol AF9-10, in this case there is no need to pass the eluate through an alumina column in order to improve the determination results.

 In the presence of a cationic surfactant, the results of the determination of NP in all cases are overestimated, regardless of the pH of the medium. But in a neutral environment (pH 7), the use of an additional sorbent - alumina - improves the determination results.

 In an acidic medium (pH 2), the combined use of SCWM and KU-23 as a sorbent significantly improves the determination results (Table 7). But the best results are achieved when conducting analysis in a neutral environment with the combined use of sorbents SKVM + KU-23 and aluminum oxide.

 Example 7. The results of the determination of NP in water in the presence of nonionic (for example, neonol AF9-10) and anionic (for example, sodium dodecyl sulfate) surfactants by the proposed method when they are concentrated in a cartridge filled with 1-5 g of SCWM and 2-10 g of anion exchange resin AN- 21 are presented in table. 8. The conditions of the experiment are similar to example 6. The number of experiments for each case presented is n = 10.

 In the presence of a nonionic surfactant, the combined use of SLE with anion exchange resin as sorbents significantly improves the results of determining NP in water at pH 7.

 As can be seen from the table. 8, in the presence of an anionic surfactant, the combined use of SCRM with anion exchange resin as sorbents overestimates the results of determination of NP in water in a neutral medium.

 In an acidic environment, good results are obtained without the use of alumina. In the presence of anionic surfactants, the determination must be carried out at pH 2.

 Example 8. The oil is concentrated by solid-phase extraction on a superthin quartz fibrous material and X-ray radiometric determination of its elemental composition is carried out. The weight of the test sample of superthin quartz fibrous material with extracted oil is 0.33 g (see table 5a).

Thus, the proposed method allows you to:
- with IR-spectrophotometric termination, to ensure the accuracy of the determination of NP, not exceeding the error in liquid-phase extraction, and significantly less than when using other sorbents for TFE;
- determine the total content of petroleum products by the amount of carbon dioxide released during thermo-oxidative regeneration;
- repeatedly use the sorbent for concentration of the NP (up to 500 times during regeneration during the elution of concentrated NP with a solvent);
- to carry out the identification of concentrated nanopowders by the X-ray radiometric method, since SCWM is chemically pure quartz;
- reduce the amount of solvent spent on one determination 3-5 times compared with the method of liquid-phase extraction;
- combine the stage of concentration and separation of substances that interfere with the determination.

SOURCES OF INFORMATION
1. Unified methods for the study of water quality. Part 1. Methods of chemical analysis of water. Ed. 3rd - M .: 1974. 831 s.

 2. T.V. Avgul, T.V. Gudyko, M.M. Senyavin. Sorption concentration of normalized organic compounds from water as a stage of their chromatographic determination. On Sat Tr.: Concentration of organic compounds. - M .: 1990, v. 10, p. 211-220.

 3. Ya. I. Korenman, N. N. Selmanschuk. Concentration of traces of petroleum products in the analysis of water. On Sat Tr.: Concentration of organic compounds. - M .: 1990, v. 10, p. 221-228.

 4. N.M. Kuzmin. Concentration in organic analysis. On Sat Tr.: Concentration of organic compounds. - M .: 1990, v. 10, p. 5-27.

 5. A.A. Serdan, G.V. Lisichkin. Concentration of organic compounds on chemically modified silicas. On Sat tr .: Concentration of organic compounds.- M .: 1990, T.10, p. 28-43. (Prototype).

Claims (8)

 1. A method for determining oil products in water, including solid-phase extraction of oil products by passing contaminated water through a cartridge filled with a sorbent based on silicon dioxide, regenerating the sorbent, removing interfering impurities and measuring the content of oil products, characterized in that the super thin quartz fiber material is used as a sorbent an amorphous structure with a fiber diameter of up to 0.5 μm 7 to 14 wt.%, with a diameter of 0.5 to 1.0 μm 31 to 48 wt.% and not more than 7 μm - the rest. 2. The method according to claim 1, characterized in that the superthin quartz fibrous material with an amorphous structure has a specific surface area of 2 m ² / g and the following fiber diameter distribution, wt.%: 0.0 - 0.5 μm - 7 - 14 ; 0.5 - 1.0 μm - 31 - 48; 1.5 - 2.0 microns - 5.6 - 22.5; 2.0 - 2.5 microns - 5.1 - 8.5; 2.5 - 3.0 microns - 2.1 - 7.6; 3.0 - 3.5 microns - 2.1 - 2.5; 3.5 - 4.0 microns - 2.8 - 3.6; 4.0 - 4.5 microns - 1.4 - 2.5; 4.5 - 5.0 microns - 2.1 - 2.5; 5.0 - 5.5 microns - 0.7 - 2.0; 5.5 - 6.0 microns - 0 - 0.5; 6.0 - 6.5 microns - 0 - 0.7; 6.5 - 7.0 μm - 1 - 1.4.  3. The method according to claim 1, characterized in that the regeneration is carried out by treating the sorbent with freons selected from the range: 1,2,2-trifluoro-1,1,2-trichloroethane, tetrafluorodibromoethane.  4. The method according to any one of claims 1 to 3, characterized in that the removal of interfering impurities is carried out by passing the eluate after regeneration through a column filled with a sorbent selected from: aluminum oxide or magnesium oxide, magnesium silicate and / or ion exchange resin.  5. The method according to any one of claims 1 to 4, characterized in that the removal of interfering impurities is carried out by passing water through a cartridge filled with a superthin quartz fiber material and a sorbent selected from: cation exchange resin, anion exchange resin placed below or on top of the superthin quartz fiber material .  6. The method according to any one of paragraphs. 1 to 5, characterized in that the determination of petroleum products is carried out at a pH of contaminated water 2 to 7.  7. The method according to claims 1 and 2, characterized in that the regeneration of superthin quartz fibrous material is carried out by thermal oxidation and the determination of oil products is carried out according to the amount of carbon dioxide formed.  8. The method according to p. 1, characterized in that after passing water through a superthin quartz fibrous material, it is subjected to X-ray radiometric elemental analysis.

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