Method for purifying organic waste salt and synchronously preparing graded porous carbon for recycling

Abstract

The invention belongs to the field of wastewater treatment, and discloses a method for purifying organic waste salt and synchronously preparing graded porous carbon for recycling. The method comprises the following steps: feeding salt-containing organic matter-containing wastewater and graded porous carbon-containing liquid into an adsorption / coagulative precipitation tank to obtain precipitated concentrated water and clear liquid; carrying out filter pressing treatment on the precipitated concentrated water to obtain a filter cake and filtrate; carrying out spray drying treatment on the clear liquid and the filtrate to obtain powdery organic waste salt; carrying out high-temperature pyrolysis treatment on the powdery organic waste salt under protective gas to obtain graded porous carbon salt powder; and mixing the graded porous carbon-containing salt powder with water to obtain a mixed solution, and performing solid-liquid separation through ultrafiltration to obtain ultrafiltration produced water and the graded porous carbon-containing liquid. Salt in organic waste salt serves as a pore-forming template, organic matter serves as a carbon source, salt powder containing graded porous carbon is obtained, the salt powder containing graded porous carbon is mixed with water, and liquid containing graded porous carbon is obtained and serves as an adsorbent to remove the organic matter in waste water.

Description

Technical Field

[0001] The invention belongs to the field of wastewater treatment, and more specifically, relates to a method for purifying organic waste salt and simultaneously preparing graded porous carbon for reuse. Background Art

[0002] Industrial waste salt is solid organic waste salt precipitated after wastewater is treated by evaporation and crystallization. It contains a large amount of toxic and harmful organic pollutants that are difficult to degrade. If it is not properly disposed of, it will cause serious pollution to water bodies, soil and atmosphere, and thus affect the balance of the ecosystem. However, with the rapid development of industrialization, the production efficiency of industries such as pesticides, pharmaceuticals, chemicals, and dyes has increased day by day, resulting in an increase in the output of organic waste salt year by year, which not only has a serious impact on the ecological environment, but also increases the burden on enterprises.

[0003] In 2016, the Ministry of Ecology and Environment included industrial waste salt in the National List of Hazardous Wastes, and by 2021, it was clearly stated that salt-containing waste liquid or solid waste salt containing toxic and harmful components generated during wastewater treatment is a hazardous waste and should be managed in accordance with the relevant requirements for hazardous waste. At present, there are mainly the following methods for treating organic waste salt at home and abroad:

[0004] The oxidation method, by adding oxidants, such as sodium hypochlorite, hydrogen peroxide, ozone and other chemical oxidants, during the cleaning process of saturated byproduct salt, oxidizes and removes organic pollutants, and finally obtains clean product salt. However, this method has limitations and can only process impurities containing a small amount of organic matter and must be easy to decompose.

[0005] Washing method, use water or suitable organic solvent to wash the waste salt, and use the principle of like dissolves like to remove the organic matter in the waste salt. Although the washing separation method is simple, it is only applicable to chemical waste salt with a single organic component.

[0006] The high-temperature pyrolysis method, in an oxygen atmosphere, oxidizes and decomposes the organic matter in the waste salt into carbon dioxide and water through high-temperature calcination, and removes it from the waste salt. However, the complete oxidation of organic pollutants requires a higher calcination temperature, and the waste salt is heated to a molten state, which corrodes equipment and consumes high energy.

[0007] From the perspective of treatment effect, cost and industrial scale, high-temperature pyrolysis is one of the most effective ways to achieve harmless and resource-based treatment of organic waste salt. However, during the pyrolysis process, organic matter is completely converted into CO2, resulting in energy waste.

[0008] Therefore, in order to address the high cost of purifying organic waste salts produced by evaporation and crystallization of high-salt and high-organic wastewater in existing wastewater treatment processes, it is urgent to propose a method for purifying organic waste salts and simultaneously preparing graded porous carbon for reuse. Summary of the invention

[0009] The purpose of the present invention is to address the deficiencies of the prior art and propose a method for purifying organic waste salt and simultaneously preparing graded porous carbon for reuse. The present invention uses salt in organic waste salt as a pore-forming template and organic matter as a carbon source to obtain salt powder containing graded porous carbon, mixes the salt powder containing graded porous carbon with water, and obtains a graded porous carbon liquid as an adsorbent to remove organic matter in wastewater.

[0010] In order to achieve the above object, the present invention provides a method for purifying organic waste salt and simultaneously preparing hierarchical porous carbon for reuse, the method comprising the following steps:

[0011] S1: sending the wastewater containing salt and organic matter and the graded porous carbon liquid into an adsorption / coagulation sedimentation tank to obtain precipitated concentrated water and clear liquid; performing filter pressing treatment on the precipitated concentrated water to obtain a filter cake and a filtrate;

[0012] S2: spray drying the clear liquid and the filtrate to obtain powdered organic waste salt;

[0013] S3: subjecting the powdered organic waste salt to high-temperature pyrolysis treatment (carbonization) under protective gas to obtain graded porous carbon salt powder;

[0014] S4: mixing the graded porous carbon-containing salt powder with water to obtain a mixed liquid, and performing solid-liquid separation by ultrafiltration to obtain ultrafiltration product water and the graded porous carbon-containing liquid.

[0015] According to the present invention, preferably, the salt-containing and organic-containing wastewater is reverse osmosis wastewater concentrate obtained by reverse osmosis treatment of landfill leachate wastewater.

[0016] In the present invention, the graded porous carbon liquid is used as an adsorbent to adsorb and remove organic matter in the salt-containing and organic-containing wastewater. As a preferred embodiment, the adsorption time of the adsorbent is 0.5-1.5h.

[0017] According to the present invention, preferably, the filter cake is sent out.

[0018] According to the present invention, preferably, the spray drying process includes atomizing the clear liquid and the filtrate into droplets, and drying the droplets with high-temperature gas to obtain the powdered organic waste salt.

[0019] In the present invention, the method also includes using a condenser to condense the water vapor generated by the spray drying treatment to obtain condensed water as the water mixed with the graded porous carbon salt powder in step S4; and includes oxidizing the non-condensable gas flowing out of the condenser and the gas generated by the high-temperature pyrolysis treatment to remove VOCs through ultraviolet photolysis technology.

[0020] According to the present invention, preferably, the temperature of the high temperature gas is 400-800°C.

[0021] According to the present invention, preferably, the conditions of the high-temperature pyrolysis treatment include: the temperature of the high-temperature pyrolysis treatment is 450-800°C, the heating rate is 5-50°C / min, and the time of the high-temperature pyrolysis treatment is 0.5-3h.

[0022] According to the present invention, preferably, the protective gas is at least one of nitrogen, argon and ammonia.

[0023] According to the present invention, preferably, the ultrafiltration membrane used in the ultrafiltration is a ceramic ultrafiltration membrane.

[0024] According to the present invention, preferably, the method further comprises subjecting the ultrafiltration produced water to a salt separation treatment of NaCl and Na2SO4 through a nanofiltration membrane.

[0025] According to the present invention, preferably, the salt separation treatment obtains salt separation produced water and salt separation concentrated water;

[0026] Performing a first reverse osmosis treatment on the separated concentrated water to obtain first reverse osmosis product water and first reverse osmosis concentrated water; reusing the first reverse osmosis product water as purified water, and evaporating and crystallizing the first reverse osmosis concentrated water to obtain Na2SO4;

[0027] The salt-separated produced water is subjected to a second reverse osmosis treatment to obtain second reverse osmosis produced water and second reverse osmosis concentrated water; the second reverse osmosis produced water is reused as purified water, and the second reverse osmosis concentrated water is evaporated and crystallized to obtain NaCl.

[0028] The beneficial effects of the technical solution of the present invention are as follows:

[0029] The present invention utilizes salt in organic waste salt as a pore-forming template and organic matter as a carbon source to obtain salt powder containing graded porous carbon. The salt powder containing graded porous carbon is mixed with water to obtain a graded porous carbon liquid as an adsorbent to remove organic matter in wastewater, thereby reducing the overall treatment cost.

[0030] The method of the invention is characterized by high efficiency, economy and sustainability.

[0031] The innovation of the method of the present invention lies in its dual functions of simultaneous processing and resource recovery, which ultimately realizes the effective combination of environmental protection and resource recycling.

[0032] Other features and advantages of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The above and other objects, features and advantages of the present invention will become more apparent through a more detailed description of exemplary embodiments of the present invention with reference to the accompanying drawings.

[0034] Figure 1A flow chart of a method for purifying organic waste salt and simultaneously preparing graded porous carbon for reuse provided in Example 1 of the present invention is shown.

[0035] Figure 2 A flow chart of treating salt-containing and organic-containing wastewater using a traditional high-temperature pyrolysis method provided in Comparative Example 1 of the present invention is shown.

[0036] Figure 3 A scanning electron microscope (SEM) image of the hierarchical porous carbon solid obtained in the present invention is shown. DETAILED DESCRIPTION

[0037] The preferred embodiments of the present invention will be described in more detail below. Although the preferred embodiments of the present invention are described below, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to make the present invention more thorough and complete, and to fully convey the scope of the present invention to those skilled in the art.

[0038] Example 1

[0039] This embodiment provides a method for purifying organic waste salt and simultaneously preparing hierarchical porous carbon for reuse, the method comprising the following steps:

[0040] S1: The landfill leachate wastewater is subjected to reverse osmosis treatment to obtain reverse osmosis wastewater concentrate, i.e., wastewater containing salt and organic matter; 250 mL of wastewater containing salt and organic matter and 50 mL of graded porous carbon liquid are sent to an adsorption / coagulation sedimentation tank for 1 hour of adsorption treatment to obtain precipitated concentrate and clear liquid; the precipitated concentrate is subjected to plate and frame filter pressing treatment to obtain filter cake and filtrate; the filter cake is sent out;

[0041] S2: spray drying the clear liquid and the filtrate, i.e., atomizing the clear liquid and the filtrate into droplets, and drying the droplets with high temperature gas (400-800° C.) to obtain powdered organic waste salt;

[0042] S3: 20 g of powdered organic waste salt is placed in a tubular furnace, and nitrogen protective gas is introduced to perform gradient temperature pyrolysis, the heating rate is 5 ° C / min, the pyrolysis temperature is 600 ° C, the pyrolysis time is 2 h, and after the pyrolysis is completed, it is naturally cooled to room temperature to obtain graded porous carbon salt powder;

[0043] S4: The graded porous carbon salt powder and 1 L of deionized water were magnetically stirred for 0.5 h to obtain a mixed solution, and the mixed solution was ultrafiltered through a ceramic ultrafiltration membrane for solid-liquid separation to obtain ultrafiltration product water and 50 mL of the graded porous carbon liquid.

[0044] The ultrafiltration produced water is subjected to a salt separation treatment of NaCl and Na2SO4 through a nanofiltration membrane, and the salt separation treatment obtains salt-separated produced water and salt-separated concentrated water;

[0045] Performing a first reverse osmosis treatment on the separated concentrated water to obtain first reverse osmosis product water and first reverse osmosis concentrated water; reusing the first reverse osmosis product water as purified water, and evaporating and crystallizing the first reverse osmosis concentrated water to obtain Na2SO4;

[0046] The salt-separated produced water is subjected to a second reverse osmosis treatment to obtain second reverse osmosis produced water and second reverse osmosis concentrated water; the second reverse osmosis produced water is reused as purified water, and the second reverse osmosis concentrated water is evaporated and crystallized to obtain NaCl.

[0047] This embodiment also includes using a condenser to condense the water vapor generated by the spray drying process to obtain condensed water as the water mixed with the graded porous carbon salt powder in step S4; and includes oxidizing the non-condensable gas flowing out of the condenser and the gas generated by the high-temperature pyrolysis treatment to remove VOCs through ultraviolet photolysis technology (dry gas purification).

[0048] Example 2

[0049] The only difference between this embodiment and embodiment 1 is that the high temperature pyrolysis treatment time is 1 hour.

[0050] Comparative Example 1

[0051] The difference between this comparative example and Example 1 is only that:

[0052] This comparative example uses the traditional high temperature pyrolysis method to treat the salt-containing organic wastewater of Example 1. The process is as follows: Figure 2 As shown, the specific steps are:

[0053] S1: The landfill leachate wastewater is treated by reverse osmosis to obtain reverse osmosis wastewater concentrate, i.e., wastewater containing salt and organic matter;

[0054] S2: spray drying the salt-containing organic wastewater, i.e., atomizing the salt-containing organic wastewater into droplets, and drying the droplets with high-temperature gas (400-800° C.) to obtain powdered organic waste salt;

[0055] S3: 20 g of powdered organic waste salt is placed in a tube furnace, and after passing air, a gradient temperature rise pyrolysis is performed, the heating rate is 5 ° C / min, the pyrolysis temperature is 600 ° C, the pyrolysis time is 2 h, and after the pyrolysis is completed, it is naturally cooled to room temperature to obtain salt powder;

[0056] S4: The salt powder and 1L of deionized water are magnetically stirred for 0.5h to obtain a mixed solution, and then the mixed solution is ultrafiltered through a ceramic ultrafiltration membrane for solid-liquid separation to obtain ultrafiltration product water and ultrafiltration concentrate. The ultrafiltration concentrate is subjected to plate and frame filter pressing to obtain a filter cake and a filtrate; the filter cake is sent out;

[0057] The ultrafiltration produced water and filtrate are subjected to a salt separation treatment of NaCl and Na2SO4 through a nanofiltration membrane, and the salt separation treatment obtains salt-separated produced water and salt-separated concentrated water;

[0058] Performing a first reverse osmosis treatment on the separated concentrated water to obtain first reverse osmosis product water and first reverse osmosis concentrated water; reusing the first reverse osmosis product water as purified water, and evaporating and crystallizing the first reverse osmosis concentrated water to obtain Na2SO4;

[0059] The salt-separated produced water is subjected to a second reverse osmosis treatment to obtain second reverse osmosis produced water and second reverse osmosis concentrated water; the second reverse osmosis produced water is reused as purified water, and the second reverse osmosis concentrated water is evaporated and crystallized to obtain NaCl.

[0060] This comparative example also includes using a condenser to condense the water vapor generated by the spray drying treatment to obtain condensed water as the water mixed with the salt powder in step S4; and includes oxidizing the non-condensable gas flowing out of the condenser and the gas generated by the high-temperature pyrolysis treatment to remove VOCs through ultraviolet photolysis technology (dry gas purification).

[0061] Under the premise of ensuring the same effect, the present invention calculates the ton water operation cost of the full process technology of Example 1, Example 2 and Comparative Example 1 respectively. Based on the operation cost of Comparative Example 1, the operation cost of Example 1 is 2.2% higher than the cost of Comparative Example 1, and the operation cost of Example 2 is 8.7% lower than the cost of Comparative Example 1. This is because: based on the cost of Comparative Example 1, Example 1 has the same calcination temperature and time as Comparative Example 1, but nitrogen needs to be introduced as a protective gas; compared with Example 1, the calcination time of Example 2 is changed to 1h, so the cost is reduced.

[0062] In the present invention, the graded porous carbon liquid obtained in Example 1 is not recycled to the adsorption / coagulation sedimentation tank, but the graded porous carbon liquid is filtered to obtain a filtered solid and placed in an oven for drying to obtain a graded porous carbon solid. The scanning electron microscope (SEM) image of the graded porous carbon solid is as follows: Figure 3 shown.

[0063] The embodiments of the present invention have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A method for purifying organic waste salt and simultaneously preparing graded porous carbon for reuse, characterized in that: The method comprises the following steps: S1: sending the wastewater containing salt and organic matter and the graded porous carbon liquid into an adsorption / coagulation sedimentation tank to obtain precipitated concentrated water and clear liquid; performing filter pressing treatment on the precipitated concentrated water to obtain a filter cake and a filtrate; S2: spray drying the clear liquid and the filtrate to obtain powdered organic waste salt; S3: subjecting the powdered organic waste salt to high-temperature pyrolysis treatment under protective gas to obtain graded porous carbon salt powder; S4: mixing the graded porous carbon-containing salt powder with water to obtain a mixed liquid, and performing solid-liquid separation by ultrafiltration to obtain ultrafiltration product water and the graded porous carbon-containing liquid.

2. The method for purifying organic waste salt and preparing hierarchical porous carbon for reuse according to claim 1, wherein: The salt-containing and organic wastewater is reverse osmosis wastewater concentrate obtained by reverse osmosis treatment of landfill leachate wastewater.

3. The method for purifying organic waste salt and preparing hierarchical porous carbon for reuse according to claim 1, wherein: The filter cake was sent out.

4. The method for purifying organic waste salt and preparing hierarchical porous carbon for reuse according to claim 1, wherein: The spray drying process includes atomizing the clear liquid and the filtrate into droplets, and drying the droplets with high-temperature gas to obtain the powdered organic waste salt.

5. The method for purifying organic waste salt and preparing hierarchical porous carbon for reuse according to claim 4, wherein: The temperature of the high temperature gas is 400-800°C.

6. The method for purifying organic waste salt and preparing hierarchical porous carbon for reuse according to claim 1, wherein: The conditions of the high temperature pyrolysis treatment include: the temperature of the high temperature pyrolysis treatment is 450-800° C., the heating rate is 5-50° C. / min, and the time of the high temperature pyrolysis treatment is 0.5-3 h.

7. The method for purifying organic waste salt and preparing hierarchical porous carbon for reuse according to claim 1, wherein: The protective gas is at least one of nitrogen, argon and ammonia.

8. The method for purifying organic waste salt and preparing hierarchical porous carbon for reuse according to claim 1, wherein: The ultrafiltration membrane used in the ultrafiltration is a ceramic ultrafiltration membrane.

9. The method for purifying organic waste salt and preparing hierarchical porous carbon for reuse according to claim 1, wherein: The method also includes subjecting the ultrafiltration produced water to a salt separation treatment of NaCl and Na2SO4 through a nanofiltration membrane.

10. The method for purifying organic waste salt and preparing hierarchical porous carbon for reuse according to claim 9, wherein: The salt separation treatment obtains salt separation produced water and salt separation concentrated water; Performing a first reverse osmosis treatment on the separated concentrated water to obtain first reverse osmosis product water and first reverse osmosis concentrated water; reusing the first reverse osmosis product water as purified water, and evaporating and crystallizing the first reverse osmosis concentrated water to obtain Na2SO4; The salt-separated produced water is subjected to a second reverse osmosis treatment to obtain second reverse osmosis produced water and second reverse osmosis concentrated water; the second reverse osmosis produced water is reused as purified water, and the second reverse osmosis concentrated water is evaporated and crystallized to obtain NaCl.

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