Industrial wastewater treatment process

Abstract

The invention discloses an industrial wastewater treatment process, and belongs to the technical field of wastewater treatment.The industrial wastewater treatment process comprises the following steps that firstly, the pH value of wastewater is adjusted to be smaller than 5, microelectrolysis filler is added, and pretreated wastewater is obtained through stirring, standing and filtering; 2, carrying out Fenton oxidation treatment on the pretreated wastewater; according to the method, an iron-carbon micro-electrolysis-Fenton oxidation combined mode is adopted for treating the wastewater, the COD removal rate is high, granular iron-carbon filler (micro-electrolysis filler) used in the iron-carbon micro-electrolysis process has stable physical and chemical properties, and the long-term and efficient treatment effect can be guaranteed; according to the micro-electrolysis filler, the boron-nitrogen-doped carbon material is used for replacing a conventional carbon material, so that the treatment efficiency of the granular iron-carbon filler is improved, the treatment process can be better linked with a Fenton oxidation treatment process, and industrial treatment is facilitated.

Description

Technical Field

[0001] The invention belongs to the technical field of industrial wastewater treatment, and specifically relates to an industrial wastewater treatment process. Background Art

[0002] Printed circuit board (PCB) wastewater is one of the main types of wastewater in the electronics industry. PCB wastewater contains a large amount of pollutants such as ammonia nitrogen, COD, and copper. If these pollutants cannot be effectively removed, it will seriously pollute precious water resources.

[0003] The iron-carbon micro-electrolysis method uses the principle of metal corrosion. In the absence of electricity, the micro-electrolysis material filled in the wastewater generates a 1.2V potential difference to electrolyze the wastewater to achieve the purpose of degrading organic pollutants. PCB wastewater contains heavy metal ions and large molecular organic matter. When the wastewater is treated with micro-electrolysis technology, the potential difference formed by iron and carbon in the iron-carbon micro-electrolysis system loses two electrons. The heavy metal ions in the wastewater are prone to the following redox reaction and are reduced to metal elements or low-valent ions. At the same time, large molecular organic matter can be degraded into small molecular organic matter, improving the biodegradability of the wastewater. However, in actual operation, there are problems such as column blockage, iron filings agglomeration, water flow short circuit, and difficulty in replacing fillers, which greatly reduce the treatment effect. Summary of the invention

[0004] The purpose of the present invention is to provide an industrial wastewater treatment process to solve the problem that the iron-carbon micro-electrolysis method has a poor effect in treating PCB wastewater.

[0005] The purpose of the present invention can be achieved by the following technical solutions:

[0006] An industrial wastewater treatment process comprises the following steps:

[0007] The first step is to adjust the pH value of the wastewater to less than 5, add micro-electrolysis filler, stir for 0.5-1h, let stand for 0.5-1h, and filter to obtain pretreated wastewater;

[0008] The second step is to subject the pretreated wastewater to Fenton oxidation treatment;

[0009] The micro-electrolysis filler is prepared from boron-nitrogen doped carbon material, iron powder, mineral filler and pore former according to a mass ratio of 1-2g:6g:1.4-1.6g:0.1g.

[0010] Furthermore, the pH value is 1-4.

[0011] Further, the COD concentration in the wastewater is 6350-6520 mg / L;

[0012] The steps of the Fenton oxidation treatment are as follows: adding an aqueous hydrogen peroxide solution to the pretreated wastewater and stirring the reaction for 1-2 hours; the mass fraction of the aqueous hydrogen peroxide solution is 30%, and the volume ratio of the aqueous hydrogen peroxide solution to the pretreated wastewater is 5mL:1L.

[0013] Furthermore, the micro-electrolysis filler is prepared by the following steps:

[0014] Boron-nitrogen doped carbon material, iron powder, mineral filler and pore-forming agent are added into water, stirred and mixed to form particles. After drying at 100°C for 30-40 minutes, particles are calcined in a nitrogen atmosphere, heated to 300°C, maintained for 30 minutes, and then heated to 800°C and maintained for 2 hours. After calcination, particles are naturally cooled to obtain micro-electrolytic filler.

[0015] Furthermore, the boron-nitrogen doped carbon material is prepared by the following steps:

[0016] Urea, boric acid and plant straw powder are mixed in a mass ratio of 0.5:0.5-1.5:1g, and after grinding evenly, mixed salt is added and fully ground, and then the temperature is raised to 800°C in a nitrogen atmosphere and maintained for 2 hours, and then naturally cooled and ground, and after acid washing, the boron-nitrogen doped carbon material is washed with water until neutral. Excess mixed salt can be removed during the acid washing process.

[0017] Furthermore, the mineral filler is one of bentonite and montmorillonite. The mineral filler acts as a binder in the micro-electrolysis filler.

[0018] Furthermore, the pore-forming agent is one of ammonium oxalate and ammonium bicarbonate. The pore-forming agent generates gas during heating, which can form micropores during the micro-electrolytic filler molding process.

[0019] Furthermore, the mass ratio of the added amount of the mixed salt to the plant straw is 4-5:1, and the mixed salt is zinc chloride and magnesium chloride in a molar ratio of 1:1.

[0020] Furthermore, the plant straw powder is one of wheat straw powder, corn straw powder and rice straw powder.

[0021] Furthermore, the heating rate is 5°C / min.

[0022] Beneficial effects of the present invention:

[0023] The present invention provides an industrial wastewater treatment process to solve the problem of poor effect of treating PCB wastewater by iron-carbon micro-electrolysis. In the method, the wastewater is treated in a combined manner of iron-carbon micro-electrolysis-Fenton oxidation, and the COD removal rate is high. Granular iron-carbon fillers (micro-electrolysis fillers) are used in the iron-carbon micro-electrolysis process, which have stable physical and chemical properties and can ensure long-term and efficient treatment effects. Boron-nitrogen doped carbon materials are used in the micro-electrolysis fillers to replace conventional carbon materials to improve the treatment efficiency of the granular iron-carbon fillers, which can be better connected with the Fenton oxidation treatment process and is convenient for industrial treatment.

[0024] The granulated filler in the present invention is not easy to compact during the wastewater treatment process, which reduces the need for frequent backwashing and replacement of fillers, and improves treatment efficiency and stability. In addition, the ferrous ions generated during the iron-carbon micro-electrolysis process can participate in the Fenton oxidation process, further improving the COD removal rate. DETAILED DESCRIPTION

[0025] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] Preparation Example 1

[0027] The preparation of micro-electrolysis filler comprises the following steps:

[0028] Urea, boric acid and wheat straw powder were mixed in a mass ratio of 0.5g:0.5g:1g, and mixed salt (zinc chloride and magnesium chloride in a molar ratio of 1:1) was added and ground evenly, and the mass ratio of the added mixed salt to the wheat straw powder was 4:1. Then, the temperature was raised to 800°C (heating rate of 5°C / min) in a nitrogen atmosphere and maintained for 2h, and then ground after natural cooling, and then pickled with 6mol / L hydrochloric acid and washed with water until neutral to obtain a boron-nitrogen doped carbon material.

[0029] Boron-nitrogen doped carbon material, iron powder, bentonite and ammonium oxalate were added into water in a mass ratio of 1g:6g:1.4g:0.1g, stirred and mixed to form spherical particles with a diameter of about 1 cm. After drying at 100°C for 40 min, the particles were calcined in a nitrogen atmosphere, heated to 300°C (heating rate of 5°C / min), maintained for 30 min, and then heated to 800°C (heating rate of 5°C / min), maintained for 2 h. After the calcination, the particles were naturally cooled to obtain micro-electrolytic filler.

[0030] Preparation Example 2

[0031] The difference between this preparation example and preparation example 1 is that the mass ratio of urea, boric acid and wheat straw powder is 0.5g:1g:1g, and the other raw materials and preparation process remain the same as those in preparation example 1.

[0032] Preparation Example 3

[0033] The difference between this preparation example and preparation example 1 is that the mass ratio of urea, boric acid and wheat straw powder is 0.5g:1.5g:1g, and the other raw materials and preparation process remain the same as those in preparation example 1.

[0034] Preparation Example 4

[0035] The difference between this preparation example and preparation example 1 is that the mass ratio of the boron-nitrogen doped carbon material, iron powder, bentonite and pore-forming agent is 2g:6g:1.6g:0.1g, and the other raw materials and preparation process remain the same as those in preparation example 1.

[0036] Preparation Example 5

[0037] The difference between this preparation example and preparation example 1 is that the mass ratio of urea, boric acid and wheat straw powder is 0.5g:1g:1g;

[0038] The mass ratio of boron-nitrogen doped carbon material, iron powder, bentonite and pore former is 2g:6g:1.6g:0.1g, and the other raw materials and preparation process remain the same as those in Preparation Example 1.

[0039] Preparation Example 6

[0040] The difference between this preparation example and preparation example 1 is that the mass ratio of urea, boric acid and wheat straw powder is 0.5g:1.5g:1g;

[0041] The mass ratio of boron-nitrogen doped carbon material, iron powder, bentonite and pore former is 2g:6g:1.6g:0.1g, and the other raw materials and preparation process remain the same as those in Preparation Example 1.

[0042] Comparative Preparation Example 1

[0043] Compared with Preparation Example 1, this comparative preparation example does not add boric acid, and the remaining raw materials and preparation process remain the same as those of Preparation Example 1.

[0044] Comparative Preparation Example 2

[0045] Compared with Preparation Example 1, this comparative preparation example does not add boric acid and urea, and the remaining raw materials and preparation process remain the same as those of Preparation Example 1.

[0046] Example 1

[0047] The pH value of the wastewater was adjusted to 1-4, and the micro-electrolysis filler prepared in Preparation Example 1 was added at a dosage of 5 g / L. After stirring for 0.5 h, it was allowed to stand for 0.5 h and filtered to obtain pretreated wastewater. The COD concentration of the wastewater inlet was 6350 mg / L, and the COD removal rate of the pretreated wastewater effluent was recorded. The results are shown in Table 1 below:

[0048] Table 1

[0049] pH COD removal rate / % 1 53 2 55 3 57 4 56

[0050] Comparative Example 1

[0051] Compared with Example 1, this comparative example adjusts the pH value of the wastewater to 3, adds the micro-electrolysis filler prepared in Comparative Preparation Example 1, and adds a dosage of 5 g / L. After stirring for 0.5 h, it is allowed to stand for 0.5 h and filtered to obtain pretreated wastewater; the COD concentration of the wastewater inlet is 6350 mg / L, and the COD removal rate of the pretreated wastewater effluent is recorded to be 51%.

[0052] Comparative Example 2

[0053] Compared with Example 1, this comparative example adjusts the pH value of the wastewater to 3, adds the micro-electrolysis filler prepared in Comparative Preparation Example 2, and adds a dosage of 5 g / L. After stirring for 0.5 h, it is allowed to stand for 0.5 h and filtered to obtain pretreated wastewater; the COD concentration of the wastewater inlet is 6350 mg / L, and the COD removal rate of the pretreated wastewater effluent is recorded to be 49%.

[0054] Example 2

[0055] This embodiment provides an industrial wastewater treatment process, comprising the following steps:

[0056] The first step is to adjust the pH value of the wastewater to 3, add the micro-electrolysis filler prepared in Preparation Example 1, and add 5 g / L of the micro-electrolysis filler. After stirring for 1 hour, let it stand for 1 hour, and filter to obtain pretreated wastewater.

[0057] The second step is to subject the pretreated wastewater to Fenton oxidation treatment: add hydrogen peroxide aqueous solution (mass fraction 30%) to the pretreated wastewater and stir the reaction for 2 hours; the COD concentration of the wastewater inlet is 6350 mg / L; adjust the volume ratio of the pretreated wastewater and the hydrogen peroxide aqueous solution to 1L:5mL.

[0058] Example 3

[0059] The difference between this embodiment and embodiment 2 is that the micro-electrolysis filler prepared in preparation example 2 is selected, and the other raw materials and preparation process are the same as those in embodiment 2.

[0060] Example 4

[0061] The difference between this embodiment and embodiment 2 is that the micro-electrolysis filler prepared in preparation example 3 is selected, and the other raw materials and preparation process are the same as those in embodiment 2.

[0062] Example 5

[0063] The difference between this embodiment and embodiment 2 is that the micro-electrolysis filler prepared in preparation example 4 is selected, and the COD concentration of the wastewater inlet is 6520 mg / L; the other raw materials and preparation process are the same as those in embodiment 2.

[0064] Example 6

[0065] The difference between this embodiment and embodiment 2 is that the micro-electrolysis filler prepared in preparation example 5 is selected, and the COD concentration of the wastewater inlet is 6520 mg / L; the other raw materials and preparation process are the same as those in embodiment 2.

[0066] Example 7

[0067] The difference between this embodiment and embodiment 2 is that the micro-electrolysis filler prepared in preparation example 6 is selected, and the COD concentration of the wastewater inlet is 6520 mg / L; the other raw materials and preparation process are the same as those in embodiment 2.

[0068] Comparative Example 3

[0069] The difference between this comparative example and Example 1 is that the micro-electrolysis filler prepared in Comparative Preparation Example 1 is selected, and the other raw materials and preparation process are the same as those in Example 2.

[0070] Comparative Example 4

[0071] The difference between this comparative example and Example 1 is that the micro-electrolysis filler prepared in Comparative Preparation Example 2 is selected, and the other raw materials and preparation process are the same as those in Example 2.

[0072] Comparative Example 5

[0073] The micro-electrolysis filler was replaced with iron powder and carbon powder with an iron-carbon mass ratio of 3:1, and the addition amount was 5 g / L. The remaining raw materials and preparation process were the same as those in Example 4.

[0074] Comparative Example 6

[0075] The micro-electrolysis filler was replaced with iron powder and carbon powder with an iron-carbon mass ratio of 2:1, and the addition amount was 5 g / L. The remaining raw materials and preparation process were the same as those in Example 4.

[0076] The effluent COD concentrations of Example 1 to Example 7 and Comparative Example 3 to Comparative Example 6 were recorded, and the results are shown in Table 2:

[0077] Table 2

[0078]

[0079] According to the results recorded in Table 2, the present invention uses a micro-electrolysis filler (made into particles) to carry out an iron-carbon micro-electrolysis process, which has good treatment effect and adaptability in the wastewater treatment process. In Example 1-Example 6, the micro-electrolysis filler prepared by the boron-nitrogen-doped carbon material has good stability, good stability when treating wastewater of different concentrations, and good COD removal effect when matched with Fenton oxidation (hydrogen peroxide). In Comparative Examples 3 and 4, micro-electrolysis fillers undoped with boron and undoped with boron and nitrogen are selected, and the treatment effect is poor. The proportion of ferrous ions produced by low micro-electrolysis efficiency is relatively small, and the process of Fenton degradation is suppressed. Among them, in Comparative Examples 5-Comparative Examples 6, the micro-electrolysis process is carried out by adding iron powder and carbon powder. When the amount of iron powder added is too much, a large amount of ferrous ions will be produced under acidic conditions, which not only has an inhibitory effect on the micro-battery reaction, but also, in the subsequent Fenton oxidation process, ferrous ions catalyze hydrogen peroxide to produce hydroxyl radicals, and excessive ferrous ions will react with hydroxyl radicals, resulting in hydroxyl radicals failing to react with organic pollutants in time, resulting in low utilization of hydrogen peroxide. Adding in the form of carbon powder and iron powder is more suitable for a precisely controlled reaction system, otherwise it will increase the loss of iron powder, causing the iron ion content in the system to be too high, which can easily cause secondary pollution.

[0080] It should be noted that, in this article, relational terms such as first and second, etc. 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.

[0081] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. An industrial wastewater treatment process, characterized in that: The steps include: The first step is to adjust the pH value of the wastewater to less than 5, add micro-electrolysis filler, and obtain pre-treated wastewater after stirring, standing and filtering; The second step is to subject the pretreated wastewater to Fenton oxidation treatment; The micro-electrolysis filler is prepared from boron-nitrogen doped carbon material, iron powder, mineral filler and pore former according to a mass ratio of 1-2g:6g:1.4-1.6g:0.1g.

2. An industrial wastewater treatment process according to claim 1, characterized in that: The pH value is 1-4.

3. An industrial wastewater treatment process according to claim 1, characterized in that: The COD concentration in the wastewater is 6350-6520 mg / L; The steps of the Fenton oxidation treatment are as follows: adding an aqueous hydrogen peroxide solution to the pretreated wastewater and stirring the reaction for 1-2 hours; the mass fraction of the aqueous hydrogen peroxide solution is 30%, and the volume ratio of the aqueous hydrogen peroxide solution to the pretreated wastewater is 5mL:1L.

4. An industrial wastewater treatment process according to claim 1, characterized in that: The micro-electrolysis filler is prepared by the following steps: Boron-nitrogen doped carbon material, iron powder, mineral filler and pore-forming agent are added into water, stirred and mixed to form particles. After drying at 100°C for 30-40 minutes, particles are calcined in a nitrogen atmosphere, heated to 300°C, maintained for 30 minutes, and then heated to 800°C and maintained for 2 hours. After calcination, particles are naturally cooled to obtain micro-electrolytic filler.

5. The industrial wastewater treatment process according to claim 1, characterized in that: The boron-nitrogen doped carbon material is prepared by the following steps: Urea, boric acid and plant straw powder are mixed in a mass ratio of 0.5:0.5-1.5:1g, ground evenly, then mixed salt is added and ground thoroughly, then heated to 800°C under a nitrogen atmosphere and maintained for 2 hours, naturally cooled and then ground, and after acid washing, washed with water until neutral to obtain a boron-nitrogen doped carbon material.

6. An industrial wastewater treatment process according to claim 4, characterized in that: The mineral filler is one of bentonite and montmorillonite.

7. An industrial wastewater treatment process according to claim 4, characterized in that: The pore former is one of ammonium oxalate and ammonium bicarbonate.

8. An industrial wastewater treatment process according to claim 5, characterized in that: The mass ratio of the added amount of the mixed salt to the plant straw is 4-5:1, and the mixed salt is zinc chloride and magnesium chloride in a molar ratio of 1:

1.

9. An industrial wastewater treatment process according to claim 5, characterized in that: The plant straw powder is one of wheat straw powder, corn straw powder and rice straw powder.

10. An industrial wastewater treatment process according to claim 4 or 5, characterized in that: The heating rate is 5°C / min.

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