Method for removing ferrous ions

Abstract

The invention discloses a method for removing ferrous ions. The method for removing the divalent iron ions is characterized by comprising the following steps: 1) carrying out oxidation treatment on divalent iron in raw water containing ferrous ions to form trivalent iron ions and obtain a system containing flocculent precipitates; the invention discloses a method for removing ferrous ions from a system containing flocculent precipitates, which comprises the following steps: 1) preparing a system containing flocculent precipitates, 2) carrying out coagulation treatment on the system containing flocculent precipitates through a coagulant and / or a flocculating agent to remove precipitates so as to obtain a system after coagulation treatment, and 3) filtering the system after coagulation treatment through manganese sand so as to obtain the water without ferrous ions The method has the advantages of wide treatment range, effective removal of pollutants and low treatment cost.

Description

Technical Field

[0001] The invention belongs to the technical field of water treatment and relates to a method for removing divalent iron ions. Background Art

[0002] During the oilfield production process, as the exploitation level increases, it is necessary to increase the formation pressure by injecting water into the formation. The injection water source is mainly the oilfield production water that has been treated to meet the standards. When the production water volume does not meet the injection requirements, other water sources, such as well water, are supplemented. When the well water contains ferrous ions (Fe 2+ ) when reacting with the sulfide ions (S 2- ) will generate a large amount of ferrous sulfide (FeS) precipitation, which will affect the water injection effect. Therefore, before the production water is mixed with the water source well water, the ferrous ions (Fe 2+ ) removal. At present, the traditional ferrous ion (Fe 2+ )The removal process has poor stability, unsatisfactory iron removal effect, high energy consumption, and the need to adjust the acid-base level of the wastewater. The operation is cumbersome and the overall application has certain limitations. An efficient ferrous ion removal method is urgently needed to meet the quality and water quantity requirements of oilfield reinjection water. Summary of the invention

[0003] The purpose of the present invention is to provide a method for removing divalent iron ions.

[0004] The present invention provides a method for removing divalent iron ions, comprising the following steps: 1) The divalent iron in the raw water containing ferrous ions is oxidized to form trivalent iron ions, thereby obtaining a system containing flocculent precipitates; 2) coagulating the system containing flocculent precipitate by means of a coagulant and / or a flocculant to remove the precipitate and obtain a coagulated system; 3) The system after the coagulation treatment is filtered through manganese sand to remove the precipitate, thereby obtaining water from which the divalent iron ions are removed.

[0005] In the above method, the oxidation treatment is selected from any one of ozone oxidation, electrochemical oxidation and chemical oxidation; The chemical agent includes sodium hypochlorite, hydrogen peroxide or potassium permanganate.

[0006] In the present invention, the conditions and usage of the oxidation treatment are all conventional methods in the art.

[0007] In the above method, the coagulant and the flocculant are selected from any one or more of polyaluminium chloride, polyferric sulfate, polyvinyl alcohol, polyaluminium sulfate and polyacrylamide; the coagulant first aggregates small particles into larger particles, and then the flocculant further enlarges and compacts these large particles to improve their sedimentation performance, and the two are used together to achieve effective removal of suspended particles in water.

[0008] In the above method, in the system containing flocculent precipitation, the dosage of the coagulant can be 20-80 mg / L, and the dosage of the flocculant can be 2-15 mg / L.

[0009] In the above method, the manganese sand is selected from manganese sands with different particle size gradations; The manganese sand with different particle size distributions can be manganese sand with at least one particle size of 0.2~0.5 mm, 1~2 mm, and 2~4 mm.

[0010] In the above method, when the manganese sand with different particle size gradations is composed of manganese sand with two or three particle sizes, the particle size decreases from bottom to top.

[0011] In the above method, the manganese sand with different particle size gradations consists of a manganese sand layer with a particle size of 0.2-0.5 mm, a manganese sand layer with a particle size of 1-2 mm, and a manganese sand layer with a particle size of 2-4 mm from top to bottom.

[0012] In the above method, when the manganese sand with different particle size gradations is composed of two or three kinds of manganese sand with particle sizes, the total thickness of the manganese sand layer is 20~60cm (specifically 30cm), and the thickness of each layer is the same; specifically, the total height is 30cm, if it is manganese sand with one particle size, its height is 30cm; if it is composed of manganese sand with two particle size gradations, the height is 15cm each; if it is composed of manganese sand with three particle size gradations, the height is 10cm each.

[0013] The present invention intercepts macromolecular suspended pollutants, organic matter and metal ions through the treatment of step 3).

[0014] The present invention has the following beneficial effects: 1. This method is suitable for the treatment of the same type of wastewater, with a wide treatment range, and is not limited to oilfield water; 2. The treatment process is simple and the effect is excellent. Through the combination of multi-stage methods, pollutants such as organic matter, suspended matter, and metal ions in water can be effectively removed; 3. The operating cost is low, and the facility occupies a small area, so there is no need for too many large equipment, which fully reduces energy consumption and expenditure.

[0015] Therefore, the present application has obvious advantages in terms of treatment range, treatment effect, treatment cost, etc., and provides a simple and efficient new method for oilfield reinjection water treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic flow chart of the method for removing divalent iron ions provided in the present application. DETAILED DESCRIPTION

[0017] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0018] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0019] The present invention is further described in detail below through specific implementation modes.

[0020] The present invention provides a method for removing divalent iron ions, comprising the following steps: 1) The divalent iron in the raw water containing ferrous ions is oxidized to form trivalent iron ions, thereby obtaining a system containing flocculent precipitates; 2) The system containing flocculent precipitates is subjected to coagulation treatment by a coagulant, and the flocculent precipitates are adsorbed and removed, thereby achieving rapid sedimentation, further reducing the content of organic and inorganic matter in the wastewater, alleviating the pressure of subsequent treatment, and obtaining a system after coagulation treatment; 3) The system after coagulation treatment is filtered through manganese sand to intercept the macromolecular suspended pollutants, organic matter and metal ions, further reducing the load of various indicators in the water, that is, obtaining water without divalent iron ions.

[0021] Furthermore, the oxidation method is selected from any one of ozone oxidation, electrochemical oxidation, and chemical oxidation.

[0022] In the following examples, the raw water containing ferrous ions is wastewater from a certain company containing 100.91 mg / L of divalent ferrous ions.

[0023] Example 1 This embodiment provides a method for removing ferrous ions (Fe 2+ ) includes the following steps: 1. Oxidation treatment: The raw water containing ferrous ions is treated by an oxidation method to oxidize the divalent iron in the water into trivalent iron, thereby achieving the removal of ferrous iron, and at the same time, the high-valent iron ions are precipitated in the form of ferric hydroxide precipitation. In this embodiment, the oxidation method is ozone oxidation, using oxygen as the gas source, the ozone output is 10 g / h, the gas flow rate is 2 mL / min, and the treatment is 5 min.

[0024] 2. Coagulation treatment: Add 4 mg / L polyacrylamide as a flocculant to the water after oxidation treatment, and use the adsorption and bridging effect of the flocculant to fully condense the sediment and suspended matter in the water into large flocs, thereby achieving rapid sedimentation.

[0025] 3. Filtration treatment: By using three different gradations of manganese sand (0.2~0.5 mm, 1~2 mm, 2~4 mm) for combined filtration and separation, it is used to intercept organic matter and macromolecular suspended pollutants in water and reduce the presence of particulate matter in water. The specific method of filtering with manganese sand of different gradations is as follows: first place the manganese sand layer with the largest particle size (2~4 mm) on the filter cushion layer, then the manganese sand layer with a medium particle size (1~2 mm), and the top layer is the manganese sand layer with the smallest particle size (0.2~0.5mm), and the thickness of each layer is 10 cm.

[0026] After the above three steps, the iron ion removal rate in the raw water reached 99%, meeting the requirements for oil field water injection.

[0027] Example 2 This embodiment provides a method for removing ferrous ions (Fe 2+ ) includes the following steps: 1. Oxidation treatment: The raw water containing ferrous ions is treated by oxidation method, and the divalent iron in the water is oxidized into trivalent iron, thereby achieving the removal of ferrous iron, and at the same time, the high-valent iron ions are precipitated in the form of ferric hydroxide. In this embodiment, the oxidation method is chemical oxidation, and the oxidant is sodium hypochlorite (NaClO), Fe 2+ The mass ratio of sodium hypochlorite is 1:1.2, and the reaction time is 5 min.

[0028] 2. Coagulation treatment: Add 40 mg / L polyaluminium chloride as a coagulant to the wastewater after oxidation treatment, and use the adsorption and bridging effect of the coagulant to fully condense the sediment and suspended matter in the water into flocs, thereby achieving rapid sedimentation.

[0029] 3. Filtration treatment: A 0.2~0.5 mm manganese sand layer (total thickness 30 cm) is placed on the filter pad for filtration separation to intercept organic matter and large molecular suspended pollutants in the mixed clean and dirty wastewater and reduce the presence of particulate matter in the water.

[0030] After the above three steps, the iron ion removal rate in the water is close to 100%, which meets the requirements of oil field water injection. The single layer of 0.2~0.5mm has the best effect, but the filtration speed is the slowest.

[0031] Example 3 This embodiment provides a method for removing iron from industrial wastewater, comprising the following steps: 1. Oxidation treatment: The industrial wastewater is treated by oxidation method, and the divalent iron in the industrial wastewater is oxidized into trivalent iron, thereby achieving the removal of ferrous iron, and at the same time, the high-valent iron ions are precipitated in the form of ferric hydroxide precipitation. In this embodiment, the oxidation method is ozone oxidation, using air as the gas source, the ozone output is 10 g / h, the gas flow rate is 2 mL / min, and the treatment is 10 min.

[0032] 2. Coagulation treatment: Add coagulants and flocculants to the wastewater after oxidation treatment, and use the adsorption and bridging effect of the coagulant to fully condense the sediments and suspended solids in the water into flocs, thereby achieving rapid sedimentation. In this embodiment, the coagulant is polyaluminum chloride and the flocculant is polyacrylamide, and the dosages are 20 mg / L and 2 mg / L respectively.

[0033] 3. Filtration treatment: Filtration and separation are performed by using manganese sands of different gradations to intercept organic matter and macromolecular suspended pollutants in the clean and polluted mixed wastewater, and reduce the presence of particulate matter in the water. In this embodiment, two manganese sands of different gradations (0.2~0.5 mm and 2~4 mm) are used for combined filtration. The specific method is to first place a manganese sand layer with the largest particle size (2~4 mm) on the filter cushion layer, and then a manganese sand layer with the smallest particle size (0.2~0.5 mm), and the thickness of each layer is 15 cm.

[0034] After the above three steps, the iron ion removal rate in industrial wastewater reached 99%, meeting the discharge-related water quality requirements.

[0035] Example 4 This embodiment provides a method for removing iron from industrial wastewater, comprising the following steps: 1. Oxidation treatment: The industrial wastewater is treated by oxidation method, and the divalent iron in the industrial wastewater is oxidized into trivalent iron, thereby achieving the removal of ferrous iron, and at the same time, the high-valent iron ions are precipitated in the form of ferric hydroxide precipitation. In this embodiment, the oxidation method is electrochemical oxidation (temperature 20-50°C, current 0.1-0.3A, treatment time 3-10min), specifically, the temperature can be 30°C, the current can be 0.3A, and the treatment time can be 10 min.

[0036] 2. Coagulation treatment: Add flocculants to the wastewater after oxidation treatment, and use the adsorption and bridging effect of the flocculants to fully condense the sediments and suspended solids in the water into large flocs, thereby achieving rapid sedimentation. In this embodiment, the flocculant is polyacrylamide, and the dosage is 4 mg / L.

[0037] 3. Filtration treatment: Filtration and separation are performed by using manganese sands of different gradations to intercept organic matter and macromolecular suspended pollutants in the clean and polluted mixed wastewater, and reduce the presence of particulate matter in the water. In this embodiment, three different gradations of manganese sand (0.2~0.5 mm, 1~2 mm and 2~4 mm) are used for combined filtration. The specific method is to first place a manganese sand layer with the largest particle size (2~4 mm) on the filter cushion layer, then a manganese sand layer with a medium particle size (1~2 mm), and the top layer is a manganese sand layer with the smallest particle size (0.2~0.5 mm), and the thickness of each layer is 10 cm.

[0038] After the above three steps, the iron ion removal rate in industrial wastewater reached 99%, meeting the discharge-related water quality requirements.

[0039] Example 5 After being treated by the scheme of Example 3 of the present invention, the amount of iron ions in the tail water measured was 0 mg / L, and the total iron content dropped from 100.91 mg / L to 0 mg / L, with a removal rate of 100%. Most of the iron ions were removed by oxidation treatment, and the precipitate of iron suspended in the waste water was settled by coagulation treatment technology, and finally, the remaining suspended matter in the water was thoroughly removed by further filtration of manganese sand, thereby achieving complete removal of the total iron in the effluent.

[0040] Comparative Example 1 This example provides a mixed water injection method for removing ferrous ions (Fe 2+ ) includes the following steps: 1. Oxidation treatment: The raw water containing ferrous ions is treated by oxidation method, and the divalent iron in the water is oxidized into trivalent iron, thereby achieving the removal of ferrous iron, and at the same time, the high-valent iron ions are precipitated in the form of ferric hydroxide. In this embodiment, the oxidation method is chemical oxidation, and the oxidant is sodium hypochlorite (NaClO), Fe 2+ The mass ratio of sodium hypochlorite is 1:0.77, and the reaction time is 5 min.

[0041] 2. Coagulation treatment: Add 2 mg / L polyacrylamide as a coagulant to the wastewater after oxidation treatment, and use the adsorption and bridging effect of the coagulant to fully condense the sediment, suspended matter, etc. in the water into flocs, thereby achieving sedimentation.

[0042] After the above two steps of treatment, the iron ion removal rate in the water is 62.5%.

[0043] Example 6 Based on the method in Comparative Example 1, the difference is that after oxidation treatment and coagulation treatment, a manganese sand filter layer with different gradations is used for filtration treatment, as follows: Filtration treatment: After oxidation treatment and coagulation sedimentation, the water samples were treated by manganese sand filtration layers with different gradations (0.2~0.5mm, 2~4mm, 0.2~0.5mm and 1~2mm, 0.2~0.5mm and 2~4mm, 1~2mm and 2~4mm, 0.2~0.5mm, 1~2mm and 2~4mm) to intercept organic matter and macromolecular suspended pollutants in the clean and polluted mixed wastewater and reduce the presence of particulate matter in the water. Among them, the total thickness of manganese sand with different gradations is 30cm, and the thickness of each layer of manganese sand composed of multiple gradations is the same.

[0044] After the above three steps, the iron ion removal rates in the water were 100%, 80.7%, 97.1%, 92.74%, 90% and 96.18% respectively. Among them, the single layer of manganese sand with a grading of 0.2-0.5mm had the best effect, but the filtration speed was the slowest.

[0045] By comparing Example 6 with the comparative example, it can be seen that in the comparative example, only the ferrous iron oxidation treatment was performed and then the water sample was directly left to stand, and suspended flocs were still present in the water sample, affecting the overall turbidity of the water sample. At this time, the total iron removal rate in the water sample was positively correlated with the standing time, which would ultimately affect the total iron content of the effluent. However, after being treated by the method of the present invention, not only the total iron removal rate is high, but also the flowing water can be filtered to achieve efficient and rapid filtration.

[0046] Comparative Example 2 According to the method in Example 1 of the present invention, the difference is that step 2 and step 3 are not performed, and the details are as follows: In this comparative example, the oxidation method is ozone oxidation, using oxygen as the gas source, the ozone output is 10 g / h, the gas flow rate is 2 mL / min, and after 5 minutes of treatment, the iron ion removal rate in the raw water is 93.9%, which does not meet the requirements for oilfield water injection (iron ion content <0.3 mg / L).

[0047] Compared with Comparative Example 2, Example 6 of the present invention processes a large amount of water in actual production. If the flocs after coagulation cannot settle quickly and fully, the iron content of the effluent will inevitably be affected. Therefore, manganese sand is further used for filtration through the present invention, the purpose of which is to fully retain the flocs in the system after coagulation, thereby achieving a high removal rate of iron ions.

[0048] In summary, through oxidation treatment, coagulation treatment, filtration treatment and other steps, suspended matter and iron ions in the wastewater are effectively removed. The synergistic treatment of coagulation technology and filtration technology ensures the efficient removal of iron ions in this process, and is also the key to achieving efficient wastewater treatment.

[0049] This specific example is only an explanation of the present application, and it is not a limitation of the present application. After reading this specification, those skilled in the art can make modifications to the present embodiment without creative contribution as needed, but they are protected by the patent law as long as they are within the scope of the claims of the present application.

Claims

1. A method for removing divalent iron ions, characterized in that: The steps include: 1) The divalent iron in the raw water containing ferrous ions is oxidized to form trivalent iron ions, thereby obtaining a system containing flocculent precipitates; 2) coagulating the system containing flocculent precipitate by means of a coagulant and / or a flocculant to remove the precipitate and obtain a coagulated system; 3) The system after the coagulation treatment is filtered through manganese sand to obtain water from which the divalent iron ions are removed.

2. The method according to claim 1, characterized in that: The oxidation treatment is selected from any one of ozone oxidation, electrochemical oxidation and chemical oxidation; The chemical agent includes sodium hypochlorite, hydrogen peroxide or potassium permanganate.

3. The method according to claim 1 or 2, characterized in that: The coagulant and the flocculant are selected from any one or more of polyaluminium chloride, polyferric sulfate, polyvinyl alcohol, polyaluminium sulfate and polyacrylamide.

4. The method according to any one of claims 1 to 3, characterized in that In the system containing flocculent precipitation, the dosage of the coagulant is 20-80 mg / L. And / or, the flocculant dosage is 2-15 mg / L.

5. The method according to any one of claims 1 to 4, characterized in that The manganese sand is selected from manganese sands with different particle size gradations; The manganese sand with different particle size distributions is manganese sand with at least one particle size of 0.2-0.5 mm, 1-2 mm, and 2-4 mm.

6. The method according to claim 5, characterized in that When the manganese sand with different particle size gradations consists of manganese sand with two or three particle sizes, the particle sizes decrease from bottom to top.

7. The method according to claim 5 or 6, characterized in that The manganese sand with different particle size gradations consists of a manganese sand layer with a particle size of 0.2-0.5 mm, a manganese sand layer with a particle size of 1-2 mm, and a manganese sand layer with a particle size of 2-4 mm from top to bottom.

8. The method according to claim 6 or 7, characterized in that: When the manganese sand with different particle size gradations consists of manganese sand with two or three particle sizes, the total thickness of the manganese sand layer is 20-60 cm, and the thickness of each layer is the same.

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