Method for breaking and removing scaling ions and scale inhibitor in wastewater

Abstract

The invention relates to the technical field of sewage treatment, in particular to a complex breaking and removing method for scaling ions and a scale inhibitor in wastewater. The method comprises the following steps: putting an oxidizing agent, a seed crystal and a precipitator into the wastewater, carrying out oxidation complex breaking and nucleation granulation reaction, and carrying out solid-liquid separation after the reaction is finished, so as to obtain purified water. The method comprises the two steps of oxidation complex breaking and nucleation granulation, a complex structure is damaged through oxidation, then scale-causing ions and an intermediate product of the scale inhibitor are removed from water through nucleation granulation, the process is simple, the efficiency is high, and no secondary pollution is generated.

Description

Technical Field

[0001] The invention relates to the technical field of sewage treatment, and in particular to a method for breaking the complex between scale-causing ions and scale inhibitors in wastewater and removing them. Background Art

[0002] The petrochemical, photovoltaic, chip, new energy battery and other industries generate a large amount of industrial wastewater, which seriously endangers human health and the ecological environment. In the face of the environmental protection requirements of near-zero wastewater discharge, reverse osmosis and crystallization evaporation are usually used as the terminal treatment of wastewater to reduce the amount of wastewater. However, since the wastewater contains a large amount of scale-causing ions such as calcium, magnesium, silicon, copper, iron, and aluminum, it is easy to scale on the surface of the reverse osmosis membrane or inside the crystallization evaporator, seriously affecting production efficiency and production safety.

[0003] In order to remove scale-causing ions from water, researchers have proposed methods such as chemical precipitation, coagulation, adsorption, and ion exchange. Among them, the chemical precipitation method is widely used because of its simple process and easy operation. However, the large-scale use of some scale inhibitors in the production process causes the scale-causing ions in the water to form stable complexes with the scale inhibitors, and it is difficult to remove the ions by simple chemical precipitation. Therefore, it is necessary to first destroy the complex structure of the scale-causing ion-scale inhibitor, and then remove the two from the water. For example, CN201510926201.9 proposes a method for ozone complex breaking and simultaneous removal of heavy metals, in which the complexing agent is oxidized by ozone, and the ionic precipitates in the water are removed by microfiltration. However, it is difficult to mineralize the complexing agent by oxidation alone, and a large amount of organic intermediates will still remain in the water, and the microfiltration method is also prone to secondary pollution, increasing operating costs.

[0004] Therefore, it is desirable to provide a new method for simultaneously removing the scale-causing ions and the scale inhibitor after decomplexing the scale-causing ions and the scale inhibitor. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a method for breaking the complex and removing scale-causing ions and scale inhibitors in wastewater, including two steps of oxidative complex breaking and nucleus crystal granulation. The complex structure is destroyed by oxidation, and then the scale-causing ions and scale inhibitor intermediates are removed from the water by nucleus crystal granulation. The process is simple, efficient, and will not cause secondary pollution.

[0006] In the first aspect, the present invention provides a method for decomposing and removing scale-causing ions and scale inhibitors in wastewater, the method comprising: placing an oxidant, seed crystals and a precipitant in the wastewater to carry out oxidation decomposition and nucleation granulation reactions, and after the reaction is completed, solid-liquid separation is performed to obtain clean water.

[0007] The method of the present invention comprises two steps: oxidation and complex breaking, and nucleation and granulation. The oxidant attacks the binding sites of ions and scale inhibitors to destroy the complex structure, and then removes the scale-causing ions and scale inhibitor intermediates from the water through nucleation and granulation, thereby reducing the organic matter content. The process is simple, the operation is simple, the treatment efficiency is high, and no secondary pollution is generated. The flow chart is as follows: Figure 1 As shown, specifically:

[0008] The oxidant provided by the present invention can destroy the active sites of the scale inhibitor-scaling ion complex, thereby destroying the complex of the scale inhibitor and the scale ion, causing the ion to be separated from the complex, and further oxidizing the organic scale inhibitor. The inductive effect of the crystal seeds and the chemical action of the precipitant can convert the free scale ions generated by the complex destruction into insoluble crystals, and adsorb and co-precipitate with the oxidized scale inhibitor intermediate product to finally form a dense nucleus crystal granulation body. The scale ions and the scale inhibitor can be removed by solid-liquid separation. The process is simple and efficient, and no chemical sludge will be generated and no secondary pollution will be generated. It is of great significance to the treatment of industrial wastewater.

[0009] As a preferred technical solution of the present invention, the oxidant is selected from any one or more of hydrogen peroxide, ozone or sodium hypochlorite.

[0010] The oxidant provided by the present invention can destroy the active sites of the scale inhibitor-scale-causing ion complex, thereby blocking the complexation of the scale inhibitor with the scale-causing ion and destroying the stable structure of the scale inhibitor.

[0011] As a preferred technical solution of the present invention, the molar ratio of the oxidant to the scale inhibitor in the wastewater is 1 to 2:1, for example, 1:1, 1.2:1, 1.4:1, 1.6:1, 1.8:1, 2:1, etc.

[0012] The seeds and precipitants used in the nuclear crystal granulation of the present invention can be adjusted according to the type and concentration of the scale-causing ions.

[0013] As a preferred technical solution of the present invention, the seed crystal is selected from any one or more of garnet, zeolite, dolomite or diatomaceous earth.

[0014] As a preferred technical solution of the present invention, the mass ratio of the seed crystal to the wastewater is 0.1 to 0.2:1, for example, 0.1:1, 0.12:1, 0.14:1, 0.16:1, 0.18:1, 0.2:1, etc.

[0015] As a preferred technical solution of the present invention, the precipitant is selected from any one or more of sodium hydroxide, sodium carbonate or sodium aluminate.

[0016] As a preferred technical solution of the present invention, the molar ratio of the precipitant to the scale-causing ions in the wastewater is 1 to 1.2:1, for example, 1:1, 1.05:1, 1.1:1, 1.15:1, 1.2:1, etc.

[0017] The two steps of oxidation decomposition and nucleation granulation in the method provided by the present invention can be carried out simultaneously in the same device, and the precipitant and the seed crystal can promote the oxidant to produce active groups to enhance the decomposition effect.

[0018] As a preferred technical solution of the present invention, the reaction time of the oxidation complex breaking is 30 to 120 minutes, for example, 30 minutes, 60 minutes, 90 minutes, 120 minutes, etc.

[0019] As a preferred technical solution of the present invention, the reaction time of the core crystal granulation is 5 to 20 minutes, for example, 5 minutes, 10 minutes, 15 minutes, 20 minutes, etc.

[0020] The reaction time of oxidation decomposition and the reaction time of nucleation granulation in the present invention are the time required for the two reactions respectively, but in the actual reaction process, the two are carried out simultaneously, so the total reaction time is not the sum of the two reaction times.

[0021] As a preferred technical solution of the present invention, the scale-causing ions include any one or more of calcium ions, magnesium ions, silicon ions, copper ions, iron ions and aluminum ions.

[0022] As a preferred technical solution of the present invention, the scale inhibitor includes any one or more of citric acid, tartaric acid, EDTA and PDTA.

[0023] As a preferred technical solution of the present invention, the content of scale-causing ions in the wastewater is 100-10000 mg / L, for example, 100 mg / L, 500 mg / L, 1000 mg / L, 5000 mg / L, 10000 mg / L, etc.

[0024] As a preferred technical solution of the present invention, the content of the scale inhibitor in the wastewater is 50-500 mg / L, for example, 50 mg / L, 100 mg / L, 200 mg / L, 400 mg / L, 500 mg / L, etc.

[0025] The technical solution provided by the embodiment of the present invention has the following advantages compared with the prior art:

[0026] The present invention provides a method for breaking complexes and removing scale-causing ions and scale inhibitors in wastewater, comprising two steps of oxidative complex breaking and nucleus crystal granulation. The complex structure is destroyed by oxidation, and then the scale-causing ions and scale inhibitor intermediates are removed from the water by nucleus crystal granulation. The process is simple, efficient, and will not cause secondary pollution. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0028] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0029] Figure 1 This is a flow chart of the method for breaking the complex and removing scale-causing ions and scale inhibitors in wastewater described in Example 1 of the present invention. DETAILED DESCRIPTION

[0030] In order to more clearly understand the above-mentioned objectives, features and advantages of the present invention, the scheme of the present invention will be further described below. It should be noted that the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

[0031] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein; it is obvious that the embodiments in the specification are only part of the embodiments of the present invention, rather than all of the embodiments.

[0032] Example 1

[0033] This embodiment provides a method for breaking the complex between scale-causing ions and scale inhibitors in wastewater and removing them. The flow chart is as follows: Figure 1 As shown, the method comprises the following steps:

[0034] (1) Calcium-scale inhibitor wastewater was prepared with pure water, the calcium ion concentration was 200 mg / L, the scale inhibitor content was 100 mg / L, and the TOC content was 62 mg / L.

[0035] (2) With ozone as oxidant, garnet as seed crystal, sodium carbonate as precipitant, the molar ratio of ozone to scale inhibitor in wastewater is 1.5:1, the mass ratio of garnet to wastewater is 0.15:1, and the molar ratio of sodium carbonate to scale-causing ions in wastewater is 1.1:1. The oxidant, seed crystal and precipitant are added into the above wastewater to carry out oxidation decomposition and nucleation granulation reaction. The reaction time is 30 minutes, and the solid-liquid separation is carried out to obtain purified water, in which the calcium ion concentration is reduced to 20 mg / L, the scale inhibitor content is reduced to 0 mg / L, and the TOC content is 22 mg / L.

[0036] Example 2

[0037] This embodiment provides a method for breaking the complex between scale-causing ions and scale inhibitors in wastewater and removing them, the method comprising the following steps:

[0038] (1) Magnesium-scale inhibitor wastewater was prepared with pure water, the magnesium ion concentration was 200 mg / L, the scale inhibitor content was 100 mg / L, and the TOC content was 62 mg / L.

[0039] (2) Using hydrogen peroxide as an oxidant, dolomite as a seed crystal, and sodium hydroxide as a precipitant, the molar ratio of hydrogen peroxide to the scale inhibitor in the wastewater is 1:1, the mass ratio of dolomite to the wastewater is 0.2:1, and the molar ratio of sodium hydroxide to the scale-causing ions in the wastewater is 1:1. The oxidant, seed crystals and precipitant are added to the above wastewater for oxidation and decomposition and nucleation granulation reaction. The reaction is carried out for 1 hour, and the solid-liquid separation is performed to obtain purified water, in which the magnesium ion concentration is reduced to 26 mg / L, the scale inhibitor content is reduced to 10 mg / L, and the TOC content is 25 mg / L.

[0040] Example 3

[0041] This embodiment provides a method for breaking the complex between scale-causing ions and scale inhibitors in wastewater and removing them, the method comprising the following steps:

[0042] (1) Prepare silicon-scale inhibitor wastewater with pure water, the silicon ion concentration is 200 mg / L, the scale inhibitor content is 100 mg / L, and the TOC content is 62 mg / L.

[0043] (2) Sodium hypochlorite is used as an oxidant, diatomaceous earth is used as a seed crystal, and sodium aluminate is used as a precipitant. The molar ratio of sodium hypochlorite to the scale inhibitor in the wastewater is 2:1, the mass ratio of diatomaceous earth to the wastewater is 0.1:1, and the molar ratio of sodium aluminate to the scale-causing ions in the wastewater is 1.2:1. The oxidant, seed crystals and precipitant are added to the above wastewater for oxidation and decomposition and nucleation granulation reaction. The reaction is carried out for 1 hour, and the solid-liquid separation is performed to obtain purified water, in which the silicon ion concentration is reduced to 22 mg / L, the scale inhibitor content is reduced to 8 mg / L, and the TOC content is 15 mg / L.

[0044] Comparative Example 1

[0045] This comparative example provides a method for breaking the complex between scale-causing ions and scale inhibitors in wastewater. The method is the same as that in Example 1, and the difference from Example 1 is that no seed crystals and precipitants are added in this comparative example.

[0046] After oxidation and decomposition treatment, the calcium ion concentration in the purified water is 200 mg / L, the scale inhibitor content is 1.5 mg / L, and the TOC content is 56 mg / L.

[0047] Comparative Example 2

[0048] This comparative example provides a method for removing scale-causing ions and scale inhibitors in wastewater. The method is the same as that in Example 1. The difference from Example 1 is that no oxidant is added in this comparative example.

[0049] After nuclear crystal granulation treatment, the calcium ion concentration in the obtained clean water is 200 mg / L, the scale inhibitor content is 100 mg / L, and the TOC content is 62 mg / L.

[0050] From the comparison between Example 1 and Comparative Examples 1-2, it can be found that the method provided by the present invention combines the two-step reactions of oxidation decomposition and nucleation granulation, and can effectively remove scale-causing ions and scale inhibitors in wastewater.

[0051] It should be noted that, in this article, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0052] The above description is only a specific embodiment of the present invention, so that those skilled in the art can understand or implement the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments described herein, but should conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for breaking the complex between scale-causing ions and scale inhibitors in wastewater and removing them, characterized in that: The method comprises: placing an oxidant, a crystal seed and a precipitant in the wastewater to carry out oxidation and decomposition and nucleation granulation reactions, and after the reaction is completed, solid-liquid separation is performed to obtain purified water.

2. The method according to claim 1, characterized in that: The oxidant is selected from any one or more of hydrogen peroxide, ozone or sodium hypochlorite.

3. The method according to claim 1 or 2, characterized in that: The molar ratio of the oxidant to the scale inhibitor in the wastewater is 1 to 2:

1.

4. The method according to any one of claims 1 to 3, characterized in that: The seed crystals are selected from any one or more of garnet, zeolite, dolomite or diatomaceous earth.

5. The method according to any one of claims 1 to 4, characterized in that: The mass ratio of the seed crystal to the wastewater is 0.1-0.2:

1.

6. The method according to any one of claims 1 to 5, characterized in that: The precipitant is selected from any one or more of sodium hydroxide, sodium carbonate or sodium aluminate.

7. The method according to any one of claims 1 to 6, characterized in that: The molar ratio of the precipitant to the scale-causing ions in the wastewater is 1 to 1.2:

1.

8. The method according to any one of claims 1 to 7, characterized in that: The reaction time of the oxidation and complex breaking is 30 to 120 minutes; And / or, the reaction time of the nucleus crystal granulation is 5 to 20 minutes.

9. The method according to any one of claims 1 to 8, characterized in that: The scale-causing ions include any one or more of calcium ions, magnesium ions, silicon ions, copper ions, iron ions and aluminum ions; And / or, the scale inhibitor includes any one or more of citric acid, tartaric acid, EDTA and PDTA.

10. The method according to any one of claims 1 to 9, characterized in that: The content of scale-causing ions in the wastewater is 100-10000 mg / L; And / or, the content of scale inhibitor in the wastewater is 50-500 mg / L.

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