Method for removing coking wash oil by activating sodium percarbonate with ferrous ions

Abstract

The invention relates to the technical field of washing oil methods, and particularly discloses a method for removing coking washing oil by activating sodium percarbonate with ferrous ions, which comprises the following steps: mixing ferrous ions, sodium percarbonate and emulsified washing oil for degradation reaction to complete degradation of washing oil in water. According to the method, the ferrous ions, the sodium percarbonate and the washing oil-containing water body are directly mixed, the initial concentration of the ferrous ions in the system is controlled to be 24 mM to 96 mM, the initial concentration of the sodium percarbonate is controlled to be 36 mM to 144 mM, the ferrous ions can be used for efficiently activating the sodium percarbonate and forming free radicals (1O2,. OH and CO3.-), and then the free radicals are used for efficiently degrading the washing oil in the water body. The method has the advantages of being simple in process, convenient to operate, low in cost, high in practicability, wide in application range, high in treatment efficiency, good in degradation effect, environmentally friendly and the like, and therefore the method has good application prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of washing oil methods, and specifically discloses a method for removing coking washing oil by activating sodium percarbonate with ferrous ions. Background Art

[0002] With the rapid development of social economy, sudden oil pollution incidents occur frequently, which not only pose a serious threat to the environment, but also may have a significant impact on public health and ecological diversity. In addition, industries such as petroleum, food, textile, and steel will produce oil-containing wastewater, so the treatment of such oil-containing wastewater is very important globally. Coking washing oil is a by-product of the coking process and is a fraction mixture (230 - 300 °C) obtained during the treatment of coal tar, mainly used for absorbing light oil from coke oven gas. The composition of washing oil is complex and contains various valuable compounds such as acenaphthene, fluorene, and quinoline, which are also important basic aromatic chemicals. However, when these organic substances leak into the environment, they will cause serious harm to the environment. These organic compounds usually exist in water in dissolved or emulsified forms, are more toxic, and are more difficult to degrade. They have characteristics such as persistence, bioaccumulation, carcinogenicity, and mutagenicity in organisms such as bacteria, invertebrates, and fish, and have a serious ecological impact on marine species.

[0003] Currently, the methods for removing organic substances in water mainly include physical methods, biological methods, and chemical methods, etc. Among them, physical methods have disadvantages such as high cost, adding harmful chemical substances, ineffective degradation of pollutants, and generating sludge. Biological treatment processes have limitations at high pollutant concentrations. Compared with traditional technologies, chemical methods have more advantages. Among them, advanced oxidation processes (AOPs) have excellent degradation and mineralization efficiencies for pollutants in wastewater, so they are widely regarded as a promising technology. In AOPs, homogeneous Fenton catalytic oxidation systems can degrade various organic pollutants by generating hydroxyl radicals (·OH), and can convert non-biodegradable organic pollutants into biodegradable substances. Therefore, homogeneous Fenton catalytic oxidation is considered to be one of the best choices for repairing these pollutants. In particular, the Fenton reaction using hydrogen peroxide (H2O2) and ferrous (Fe(Ⅱ)) has the advantages of simple operation, rapid degradation, and wide applicability. However, H2O2 is unstable in sunlight or at high temperatures, so it must be transported in the dark below 40 °C. While the solid oxidant sodium percarbonate (SPC) has excellent stability, is easy to transport, and has good cost-effectiveness, thus highlighting its potential to replace H2O2 to reduce safety risks. So far, there has been no report on the use of ferrous ions to activate percarbonate for treating coking washing oil. Therefore, how to obtain a method for removing washing oil in water with simple process, short reaction time, good removal effect, wide pH application range, and environmental friendliness is of great significance for effectively treating washing oil in water. Summary of the Invention

[0004] The object of the present invention is to provide a method for removing washing oil in water by activating percarbonate with ferrous ions, which has simple process, short reaction time, good removal effect, wide pH application range and is environmentally friendly.

[0005] In order to achieve the above object, the present invention adopts the following technical scheme:

[0006] A method for removing coking washing oil by activating sodium percarbonate with ferrous ions, comprising the following steps:

[0007] Step 1, preparation of emulsified oil: Put 1.0 mL of coking washing oil into a beaker, add 0.1 g of emulsifier, and then add 99 mL of ultrapure water; Stir the mixture in an ultrasonic cleaner with a glass rod for 10 min to make it fully emulsified to obtain an oil-containing wastewater with a concentration of 10 g / L, and then dilute it with ultrapure water to 100 mg / L to obtain emulsified oil;

[0008] Step 2, removal of washing oil: Weigh ferrous sulfate heptahydrate FeSO4·7H2O, add it to the above emulsified oil, and then add an oxidant to start the reaction. Shake and react for 40 min at 25°C and 250 rpm to complete the removal of washing oil in the water body;

[0009] Step 3, sample at different time points, extract with n-hexane according to the method of "Determination of Petroleum in Water - Ultraviolet Spectrophotometry" (HJ970-2018), and measure the content at 225 nm using an ultraviolet-visible spectrophotometer.

[0010] Further, in Step 1, the emulsifier is sodium dodecyl sulfate SDS;

[0011] Further, in Step 2, the concentration of ferrous sulfate heptahydrate FeSO4·7H2O is 24 mM to 96 mM; the concentration of sodium percarbonate SPC is 36 mM to 144 mM;

[0012] Further, in Step 1, the pH value of the obtained emulsified oil is 3 to 11;

[0013] Further, in Step 2, the oxidant is sodium percarbonate SPC;

[0014] Further, in Step 2, a radical scavenger is added, and the added radical scavenger is one of 30 mM tert-butanol, 30 mM L-histidine, 30 mM chloroform, and 10 mM p-nitroaniline.

[0015] Compared with the prior art, the beneficial effects of the present invention are:

[0016] 1) The raw materials used in the present invention are all common chemical reagents, which are widely sourced, inexpensive, readily available, safe, stable, and easy to store and transport;

[0017] 2) Sodium percarbonate used in the present invention has great advantages in terms of storage and transportation, is more convenient to use, and its reaction products such as CO2, H2O, CO3 2- and HCO3 - usually also exist in the natural environment.

[0018] 3) The method of using ferrous ions to activate sodium percarbonate to remove organic pollutants in water bodies of the present invention has the advantages of simple process, convenient operation, low cost, strong practicability, wide adaptability, high treatment efficiency, good degradation effect, environmental protection, etc., and can effectively degrade the organic matter in washing oil. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a comparison chart of the removal effects of different oxidants (sodium monopersulfate (PMS), sodium percarbonate (SPC), sodium persulfate (PDS)) with different concentrations on emulsified oil in Example 1 of the present invention;

[0020] Figure 2 It is a comparison chart of the removal effects of different pH values on emulsified oil in Example 2 of the present invention;

[0021] Figure 3 It is a comparison chart of the removal effects of emulsified oil under different reaction systems in Example 3 of the present invention;

[0022] Figure 4 It is a comparison chart of the removal effects of emulsified oil under different ferrous ion concentrations in Example 4 of the present invention;

[0023] Figure 5 It is a comparison chart of the removal effects of emulsified oil under different sodium percarbonate concentrations in Example 5 of the present invention;

[0024] Figure 6 It is a comparison chart of the removal effects of emulsified oil under different radical scavenger conditions in Example 6 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0025] The following is a specific introduction to the present invention in combination with the drawings and specific embodiments:

[0026] In order to deepen the understanding of the present invention, the following further detailed and complete description of the present invention is made in combination with the embodiments.

[0027] Example 1:

[0028] A method for using ferrous ions to activate sodium percarbonate to remove coking washing oil specifically includes the following steps:

[0029] Prepare 12 groups of 100 mL of wash oil with a concentration of 100 mg / L (the original pH value of this aqueous solution is 6.8). Add 72 mM of ferrous sulfate heptahydrate to each group of solutions. Among them, 3 groups use sodium peroxysulfate (PMS), sodium percarbonate (SPC), and sodium persulfate (PDS) as oxidants, so that their concentrations in the solution are all 48 mM. Shake and react for 40 min under the conditions of 25 °C and 250 rpm to complete the removal of wash oil in the water body.

[0030] In this example, according to the method of "Determination of Petroleum in Water - Ultraviolet Spectrophotometry" (HJ970 - 2018), n - hexane was used for extraction, and finally, an ultraviolet - visible spectrophotometer was used to measure the concentration of the remaining wash oil in the solution. According to the change in the concentration of wash oil in the solution before and after the reaction, the removal rate of wash oil was calculated.

[0031] Control group 1: Set the concentrations of PMS, SPC, and PDS to 36 mM, and other conditions are the same.

[0032] Control group 2: Set the concentrations of PMS, SPC, and PDS to 72 mM, and other conditions are the same.

[0033] Control group 3: Set the concentrations of PMS, SPC, and PDS to 144 mM, and other conditions are the same.

[0034] Figure 1 This is a comparison chart of the removal effects of wash oil under different oxidant conditions in Example 1 of the present invention. As Figure 1 can be seen, in the reaction system with PDS as the oxidant, the removal efficiency is relatively low, which indicates that under the current conditions, ferrous ions may not be able to effectively activate PDS to generate effective reactive species to remove wash oil. When the oxidant is PMS, the removal efficiency is only 60 - 80%, indicating that PMS can be activated by Fe(II) to remove a part of the wash oil. When the oxidant is SPC, the removal efficiency is high and low. When the concentration of SPC is 48 mM, the removal efficiency reaches 95.84%, indicating that in this example, this set of conditions has the best effect, and Fe(II) can maximize the activation of SPC to remove wash oil.

[0035] Example 2:

[0036] A method for removing coking wash oil by activating sodium percarbonate with ferrous ions, specifically including the following steps:

[0037] Prepare 5 groups of 100 mL of washing oil with a concentration of 100 mg / L (the original pH value of this aqueous solution is 6.8). Adjust its initial pH values to 3, 5, 7, 9, and 11. Add 72 mM of ferrous sulfate heptahydrate to each group of solutions. After mixing evenly, add 48 mM of sodium percarbonate, and shake and react under the conditions of 25 °C and 250 rpm for 40 min to complete the removal of washing oil in the water body.

[0038] In this example, according to the method of "Determination of Petroleum in Water - Ultraviolet Spectrophotometry" (HJ970 - 2018), n - hexane was used for extraction, and finally, an ultraviolet - visible spectrophotometer was used to measure the concentration of the remaining washing oil in the solution. According to the change in the concentration of washing oil in the solution before and after the reaction, the removal rate of washing oil was calculated.

[0039] Figure 2 This is a comparison chart of the removal effects of washing oil under different pH conditions in Example 2 of the present invention. From Figure 2 It can be seen that the removal rates of washing oil within 40 min are 98.69%, 93.00%, 95.82%, 93.06%, and 98.18% respectively, indicating that the SPC and Fe(Ⅱ) system can remove washing oil in a wide pH range, and the removal effect can reach more than 90%. When the pH is 3, the effect is the best, and the removal efficiency is 98.69%. This may be because under acidic conditions (pH < 7), iron exists in the form of Fe(Ⅱ), which is beneficial to the Fenton reaction and catalyzes SPC to generate more free radicals to degrade pollutants.

[0040] Example 3:

[0041] A method for removing coking washing oil by activating sodium percarbonate with ferrous ions specifically includes the following steps:

[0042] Prepare 3 groups of 100 mL of washing oil with a concentration of 100 mg / L (adjust the pH value to 3).

[0043] Add 72 mM of ferrous sulfate heptahydrate to one of the groups. After mixing evenly, add 48 mM of sodium percarbonate, and shake and react under the conditions of 25 °C and 250 rpm for 40 min to complete the removal of washing oil in the water body.

[0044] In this example, according to the method of "Determination of Petroleum in Water - Ultraviolet Spectrophotometry" (HJ970 - 2018), n - hexane was used for extraction, and finally, an ultraviolet - visible spectrophotometer was used to measure the concentration of the remaining washing oil in the solution. According to the change in the concentration of washing oil in the solution before and after the reaction, the removal rate of washing oil was calculated.

[0045] Control group 1: Do not use ferrous sulfate heptahydrate, and other conditions are the same.

[0046] Control group 2: Do not use sodium percarbonate, and other conditions are the same.

[0047] Figure 3 This is a comparison chart of the removal effect of wash oil under different reaction systems in Example 3 of the present invention. It can be seen from Figure 3 that when sodium percarbonate or Fe(II) is added alone, the removal rate of wash oil is less than 25%. This indicates that the ability of Fe(II) or SPC alone to decompose wash oil is very weak. The reason is that when Fe(II) or SPC is added alone, fewer active species are generated, and the degradation effect on wash oil is not obvious. When both Fe(II) and SPC exist in the reaction system, approximately 90% of the wash oil is removed within the first 1 minute, and the removal rate of wash oil is 98.69% within 40 minutes. This shows that Fe(II) can effectively activate SPC to generate active species that degrade wash oil. In addition, the degradation of wash oil shows a two-stage reaction. Approximately 90% of the wash oil is removed in the first stage, and the reaction rate is very fast, while the removal rate in the second stage is slower. This may be because: at the beginning of the reaction, the concentration of ferrous ions is relatively high, which has a good activation effect on SPC and a relatively fast degradation rate of wash oil; when the reaction reaches a certain extent, Fe(II) is converted to Fe(III), the active species are consumed by pollutants, and the degradation rate of wash oil gradually slows down.

[0048] Example 4:

[0049] A method for removing coking wash oil by activating sodium percarbonate with ferrous ions specifically includes the following steps:

[0050] Prepare 4 groups of 100 mL of wash oil with a concentration of 100 mg / L (adjust the pH value to 3).

[0051] Add different amounts of ferrous sulfate heptahydrate to each group of solutions so that the concentration of ferrous ions in the solution is 24 mM, 48 mM, 72 mM, and 96 mM; after mixing evenly, add 48 mM of sodium percarbonate, and oscillate and react at 25 °C and 250 rpm for 40 minutes to complete the removal of wash oil in the water body.

[0052] In this example, according to the method of "Ultraviolet Spectrophotometry for the Determination of Petroleum in Water" (HJ970-2018), n-hexane was used for extraction, and finally the concentration of the remaining wash oil in the solution was measured using an ultraviolet-visible spectrophotometer. Draw the change curve of the wash oil concentration under different ferrous ion concentrations, and the results are as Figure 4 shown.

[0053] Figure 4 This is a comparison chart of the removal effect of wash oil under different ferrous ion concentrations in Example 4 of the present invention. It can be seen from Figure 4It can be seen that as the concentration of Fe(II) increases from 24 mM to 72 mM, the removal rate of wash oil increases from 78.71% to 98.69%. The reason for the accelerated reaction rate may be that a higher concentration of Fe(II) promotes the generation of more reactive species by SPC, while when the concentration of Fe(II) is low, fewer reactive species are generated in this reaction system. In addition, when the concentration of Fe(II) reaches 96 mM, its removal efficiency decreases instead, because excessive Fe(II) will scavenge ·OH and H2O2 in the reaction system, thus inhibiting the generation of reactive species in the system and affecting oil removal.

[0054] Example 5:

[0055] A method for removing coking wash oil by activating sodium percarbonate with ferrous ions specifically includes the following steps:

[0056] Prepare 5 groups of 100 mL of wash oil with a concentration of 100 mg / L (adjust the pH value to 3).

[0057] Add 72 mM of ferrous sulfate heptahydrate to each group of solutions respectively. After mixing evenly, add different concentrations of sodium percarbonate so that the concentration of sodium carbonate in the solution is 36 mM, 40 mM, 48 mM, 72 mM, 144 mM; shake and react for 40 min under the conditions of 25 °C and 250 rpm to complete the removal of wash oil in the water body.

[0058] In this example, according to the method of "Determination of petroleum oil in water - Ultraviolet spectrophotometry" (HJ970 - 2018), n - hexane was used for extraction, and finally the concentration of the remaining wash oil in the solution was measured using an ultraviolet - visible spectrophotometer. Draw the change curve of the wash oil concentration under different ferrous ion concentrations, and the results are as Figure 5 shown.

[0059] Figure 5 is the comparison chart of the removal effect of wash oil under different sodium percarbonate concentrations in Example 5 of the present invention. It can be Figure 5 seen that as the concentration of SPC increases from 36 mM to 48 mM, the degradation efficiency of wash oil increases from 89.36% to 98.69% within 40 min. This may be because the increase in the concentration of SPC leads to an increase in the release of H2O2, and further releases more ·OH to degrade the target organic pollutants. However, as the concentration of SPC further increases, when the concentration of H2O2 reaches 144 mM, the removal efficiency drops to 79.9%. This phenomenon should be attributed to the fact that excessive H2O2 will produce a scavenging effect, resulting in free radical scavenging.

[0060] Example 6:

[0061] A method for removing coking wash oil by activating sodium percarbonate with ferrous ions specifically includes the following steps:

[0062] Prepare 5 groups of 100 mL of wash oil with a concentration of 100 mg / L (adjust the pH value to 3).

[0063] Add 72 mM of ferrous sulfate heptahydrate to each group of solutions. After mixing evenly, add 48 mM of sodium percarbonate; 4 groups of solutions are respectively added with tert-butanol, L-histidine, chloroform, and p-nitroaniline as radical scavengers, so that the concentrations of tert-butanol, L-histidine, and chloroform in the solution are 30 mM respectively, and the concentration of p-nitroaniline is 10 mM; react under the conditions of 25 °C and 250 rpm for 40 min to complete the removal of wash oil in the water body.

[0064] In this example, according to the method of "Determination of petroleum in water - Ultraviolet spectrophotometry" (HJ970-2018), n-hexane is used for extraction, and finally the concentration of the remaining wash oil in the solution is measured by an ultraviolet-visible spectrophotometer. According to the change of the wash oil concentration in the solution before and after the reaction, draw the change curve of the wash oil concentration under the addition of different types of radical scavengers, and the results are as Figure 6 shown.

[0065] Figure 6 This is a comparison chart of the removal effects of wash oil under different radical scavengers in Example 6 of the present invention. From Figure 6 it can be seen that tert-butanol is a typical hydroxyl radical scavenger. After adding tert-butanol, it can be observed that the degradation efficiency of wash oil decreases from 98.69% to 71.47%, indicating that a large amount of hydroxyl radicals (·OH) are generated during the degradation reaction, and ·OH plays an important role in the degradation of wash oil. p-Nitroaniline is usually used as a scavenger for carbonate radicals. When p-nitroaniline is added, it can be observed that the degradation efficiency of wash oil decreases from 98.69% to 84.31%, confirming that carbonate radicals (CO3 ·- ) are generated during the degradation reaction and play a role in the degradation of wash oil. L-Histidine is a selective 1 O2 scavenger. After L-histidine is added, the removal efficiency of wash oil decreases significantly, indicating that 1 O2 also plays an important role in the degradation of wash oil. Chloroform is used as a scavenger for O2 ·- . After adding chloroform, the oxidation activity in the Fe(Ⅱ) / SPC system hardly decreases, indicating that there is no O2 ·- in the degradation system, or its concentration is relatively low.

[0066] Therefore, the removal of wash oil by SPC is mainly due to the rapid activation of SPC by Fe(Ⅱ) to generate radicals( 1 O2, CO3 ·-And ·OH), hydroxylate the benzene ring or C=C bond, resulting in the cleavage of the benzene ring and the production of compounds such as aldehydes and esters. Finally, it is mineralized into CO2 and H2O under the continuous attack of free radicals.

[0067] The above are only embodiments of the present invention, and do not limit the patent scope of the present invention accordingly. Any equivalent structure or equivalent process transformation made by using the content of the specification and drawings of the present invention, or directly or indirectly applied in other related technical fields, shall be equally included in the patent protection scope of the present invention.

Claims

1. A method for removing coking wash oil by activating sodium percarbonate with ferrous ions, characterized in that It includes the following steps: Step 1, preparation of emulsified oil: Put 1.0 mL of coking wash oil into a beaker, add 0.1 g of emulsifier, and then add 99 mL of ultrapure water; stir the mixture in an ultrasonic cleaner with a glass rod for 10 min to make it fully emulsified to obtain oil-containing wastewater with a concentration of 10 g / L, and then dilute it with ultrapure water to 100 mg / L to obtain emulsified oil; Step 2, removal of wash oil: Weigh ferrous sulfate heptahydrate FeSO4·7H2O and add it to the above emulsified oil, then add sodium percarbonate SPC to initiate the reaction, and shake and react at 25 °C and 250 rpm for 40 min to complete the removal of wash oil in the water body; Step 3, sample at different time points, extract with n-hexane according to the method of "Determination of Petroleum in Water - Ultraviolet Spectrophotometry" (HJ970-2018), and finally determine the content with an ultraviolet-visible spectrophotometer at 225 nm.

2. The method for removing coking wash oil by activating sodium percarbonate with ferrous ions according to claim 1, characterized in that: In Step 1, the emulsifier is sodium dodecyl sulfate (SDS).

3. A method for removing coking wash oil by activating sodium percarbonate with ferrous ions according to claim 1, characterized in that: In Step 2, the concentration of ferrous sulfate heptahydrate FeSO4·7H2O is 24 mM to 96 mM; the concentration of sodium percarbonate SPC is 36 mM to 144 mM.

4. A method for removing coking wash oil by activating sodium percarbonate with ferrous ions according to claim 1, characterized in that: In Step 1, the pH value of the obtained emulsified oil is 3 to 11.

5. A method for removing coking wash oil by activating sodium percarbonate with ferrous ions according to claim 1, characterized in that: In Step 2, the oxidant is sodium percarbonate SPC.

6. A method for removing coking wash oil by activating sodium percarbonate with ferrous ions according to claim 1, characterized in that: In Step 2, add a radical scavenger, and the radical scavenger added is one of 30 mM tert-butanol, 30 mM L-histidine, 30 mM chloroform, and 10 mM p-nitroaniline.

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