Method for treating wastewater containing ammonia and urotropine

Abstract

The invention provides a method for treating wastewater containing ammonia and urotropine, the method not only can effectively remove pollutants in the wastewater, but also can recover valuable chemical substances, and the method comprises the following specific steps: step 1, mixing the wastewater containing ammonia and urotropine with sulfuric acid for reaction, and controlling the pH value to be 2-6; and 2, after the reaction is completed, recovering ammonium sulfate and urotropine sulfate from the reacted wastewater by using a physical process or a membrane treatment technology. According to the method for treating the wastewater containing ammonia and urotropine, through a series of innovative steps, the dual problems of wastewater treatment and resource recovery in chemical production are effectively solved, and the method has important industrial application value and environmental protection significance.

Description

Technical Field

[0001] The present application relates to the field of chemical wastewater treatment, and in particular to a method for treating wastewater containing ammonia and hexamethylenetetramine. Background Art

[0002] Hexamethylenetetramine (Hexamethylenetetramine), a versatile chemical product, holds a crucial position in modern industry. Its applications span a wide range of fields, including, but not limited to, its use as a curing agent for phenolic resins and an accelerator for rubber vulcanization, as well as widespread use in the textile and pharmaceutical industries. The compound's versatility and high efficiency have made it an indispensable player in the chemical industry.

[0003] Hexamine is primarily produced via a liquid-phase process, using formaldehyde and liquid ammonia as raw materials to chemically react and produce an aqueous hexamine solution. To prevent the occurrence of a reverse reaction, the amount of ammonia added is typically controlled to a slight excess. Subsequently, solid hexamine is obtained through a series of physical processes, including evaporation, crystallization, centrifugation, and drying. Optimizing this process, including precise control of reaction conditions and improving the efficiency of subsequent processing steps, is crucial to ensuring hexamine yield and quality.

[0004] The production process of methenamine, particularly during the evaporation and crystallization steps, produces wastewater containing ammonia and methenamine. This wastewater is characterized by high concentrations of ammonia (approximately 0.1-1.5%) and methenamine (approximately 0.1-2%), as well as high levels of COD (chemical oxygen demand), ammonia nitrogen, and total nitrogen, all of which indicate that the wastewater is highly polluting. Due to the characteristics of these pollutants, direct biological treatment techniques are difficult to effectively treat this wastewater. It is typically necessary to dilute it with other wastewater to reduce the concentration of the pollutants before further treatment.

[0005] In order to solve the problem of treating hexamethylenetetramine production wastewater, the industry has tried to adopt membrane filtration technologies, such as reverse osmosis and nanofiltration membrane treatment. The goal of these technologies is to achieve resource utilization of wastewater and recover water resources and valuable compounds as much as possible. However, several major problems have been encountered in practice: high energy consumption, poor interception effect of small molecule ammonia, unsatisfactory retention rate of hexamethylenetetramine molecules, and easy clogging of membrane materials. These challenges limit the widespread application of membrane treatment technology.

[0006] In summary, providing a new treatment method that can treat the above wastewater has important significance and value to the industry. Summary of the Invention

[0007] The present invention aims to overcome at least one of the shortcomings of the prior art and provide a method for treating wastewater containing ammonia and hexamethylenetetramine, which is more efficient, low-cost and environmentally friendly.

[0008] To achieve the above objectives, the present application provides a method for treating wastewater containing ammonia and hexamethylenetetramine, which can not only effectively remove pollutants in the wastewater but also recover valuable chemical substances. The specific steps are as follows:

[0009] Step 1: mixing the wastewater containing ammonia and hexamethylenetetramine with sulfuric acid to react, and controlling the pH value within the range of 2-6;

[0010] Step 2: After the reaction is completed, ammonium sulfate and hexamethylenetetramine sulfate are recovered from the wastewater after the reaction using a physical process or membrane treatment technology.

[0011] Furthermore, as a preferred embodiment, before step 1, a pretreatment step is further included: collecting wastewater containing ammonia and hexamethylenetetramine, and removing large particle impurities through preliminary filtration.

[0012] Furthermore, in step 1, under the pH conditions, ammonia reacts with sulfuric acid to produce ammonium sulfate, and simultaneously urotropine reacts with sulfuric acid to produce at least one of urotropine sulfate monoamine salt, diamine salt, triamine salt and tetraamine salt.

[0013] Furthermore, the reaction temperature in step 1 is 10-60°C.

[0014] In some embodiments, in step 1, the pH is 5-6. Under these conditions, the proton (H+) of the sulfuric acid first undergoes a protonation reaction with a nitrogen atom in the hexamethylenetetramine molecule to form an amine salt. In this environment, the reaction is relatively mild and the degree of protonation is low, thus primarily producing the amine salt.

[0015] In some embodiments, in step 1, the pH value is 4-5. Under such conditions, the protons (H+) in the sulfuric acid can undergo a protonation reaction with two or three nitrogen atoms in the hexamethylenetetramine molecule to form a diamine salt or a triamine salt.

[0016] In some embodiments, in step 1, the pH value is 2-3. Under such conditions, sulfuric acid can maximize its protonation effect and react almost completely with the nitrogen atom in the hexamine molecule to form a triamine salt or a tetraamine salt.

[0017] In some embodiments, the physical process used in step 2 is one of evaporation and crystallization centrifugation.

[0018] Specifically, in the physical process of evaporation, the wastewater after the reaction is fed into an evaporator. In the evaporator, heat is applied to evaporate the water, concentrating the solution containing ammonium sulfate and methenamine sulfate. The evaporation process requires temperature control to prevent decomposition or loss of the ammonium sulfate and methenamine sulfate.

[0019] Specifically, during the physical process of crystallization centrifugation, the concentrated solution is cooled to a suitable temperature to promote crystallization of ammonium sulfate and hexamethylenetetramine sulfate. The crystallized mixture is then fed into a centrifuge for separation. The centrifugal process utilizes centrifugal force to separate the solid ammonium sulfate and hexamethylenetetramine sulfate from the liquid. Preferably, stirring is performed during the cooling process to promote more uniform crystallization.

[0020] Preferably, the ammonium sulfate and hexamethylenetetramine sulfate solids separated in step 2 are washed to remove surface impurities and residual mother liquor. After washing, the solids are dried in a drying device to remove residual moisture, thereby obtaining high-purity, low-moisture ammonium sulfate and hexamethylenetetramine sulfate products. In other embodiments, membrane treatment technology is used to separate ammonium sulfate and hexamethylenetetramine sulfate in step 2 to improve separation purity and recovery efficiency.

[0021] In some embodiments, after the wastewater is treated in step 2, the wastewater from which ammonia and hexamine components have been removed is directly purified using biological water treatment technology to meet environmental emission standards.

[0022] In other embodiments, after the wastewater is treated in step 2, the wastewater is directly returned to the production system for use as absorption liquid, thereby realizing the recycling of water resources.

[0023] Compared with the prior art, this application has at least one of the following beneficial effects:

[0024] 1. Effectively remove pollutants: Through the mixed reaction with sulfuric acid, it can effectively convert ammonia and hexamine in wastewater into compounds that are easier to handle, such as ammonium sulfate and hexamine sulfate, thereby removing or greatly reducing the potential harm of these pollutants to the environment.

[0025] 2. Recovery of valuable chemicals: Through physical processes or membrane treatment technology, this method can recover ammonium sulfate and hexamethylenetetramine sulfate from treated wastewater. These recovered compounds can be re-entered into the production process as raw materials or intermediates, realizing the recycling of resources and reducing production costs.

[0026] 3. Environmentally friendly discharge and water resource recycling: The treated wastewater has been freed of ammonia and hexamine components and can be directly purified using biological water treatment technology to meet environmentally friendly discharge standards, or directly returned to the production system for use as absorption liquid, thus achieving efficient recycling of water resources and reducing dependence on and impact on external water resources.

[0027] 4. Dual advantages of economic benefits and environmental protection: This method not only reduces the cost of wastewater treatment, but also brings economic benefits to enterprises by recovering valuable chemical substances; at the same time, it reduces the burden on the environment and complies with the principles of green chemistry and sustainable development.

[0028] In summary, the method for treating wastewater containing ammonia and hexamethylenetetramine of the present application effectively solves the dual problems of wastewater treatment and resource recovery in chemical production through a series of innovative steps, and has important industrial application value and environmental protection significance. DETAILED DESCRIPTION

[0029] Several embodiments of the disclosure are described below. However, it should be understood that the disclosure can be presented in a variety of different ways and is not limited to the embodiments described below. In fact, the embodiments described below are intended to make the disclosure more complete and fully illustrate the scope of protection of the disclosure to those skilled in the art. It should also be understood that the embodiments disclosed herein can be combined in various ways to provide many additional embodiments.

[0030] Example:

[0031] This embodiment is to minimize environmental pollutants while recovering valuable compounds in the treatment of wastewater containing ammonia and hexamethylenetetramine.

[0032] In this example, the concentrations of ammonia and urotropine in the wastewater were first measured to determine the exact amount of sulfuric acid required. This step was performed using a titration method to ensure that the amount of sulfuric acid added could completely react with the ammonia and urotropine in the wastewater.

[0033] More specifically, ammonia is measured separately from methenamine. When measuring ammonia, a representative sample is first collected from the wastewater and stored in a clean plastic or glass container. The sample is filtered through a 0.45-micron filter membrane to remove suspended matter and particles to avoid affecting the analysis results. A standard sulfuric acid or hydrochloric acid solution is used as a titrant, and its concentration must be calibrated in advance with a standard solution. Select an appropriate pH indicator, such as methyl orange or bromocresol green, which will show different colors when the pH value changes, making it easy to observe the end point. Add the indicator to the sample, and then slowly add the acidic titrant until the solution changes color, and record the volume of titrant consumed at this time. Based on the volume of titrant consumed and its concentration, the concentration of ammonia in the sample can be calculated.

[0034] When determining hexamethylenetetramine, there are a large number of mature determination methods that can be used, so a more detailed description is not given.

[0035] After the determination is completed, sulfuric acid is slowly added to the wastewater containing ammonia and hexamethylenetetramine while monitoring the pH value of the solution using a pH meter. To ensure safety and completeness of the reaction, the addition rate is controlled and the temperature of the reaction system is maintained at room temperature (about 25°C).

[0036] In the above reaction process, the neutralization reaction formula of ammonia is O: 2NH3+H2SO4→(NH4)2SO4

[0037] In the reaction between hexamethylenetetramine and sulfuric acid, different pH values ​​will produce different reaction results, as follows:

[0038] Formation of hexamethylenetetramine sulfate: C7H7N3O5+H2SO4→C7H8N3O5SO4

[0039] Produce hexamethylenetetramine sulfate: C7H7N3O5+2H2SO4→C7H9N3O5(SO4)2

[0040] Produce hexamethylenetetramine sulfate: C7H7N3O5+3H2SO4→C7H 10 N3O5(SO4)3

[0041] Formation of urotropine tetraammonium sulfate: C7H7N3O5+2H2SO4→C7H 11 N3O5(SO4)4

[0042] It should be understood that the amount of sulfuric acid added should be adjusted appropriately according to the progress of the reaction to maintain a pH value between 2 and 6. This range can optimize the formation of hexamethylenetetramine sulfate while avoiding the production of environmentally harmful by-products.

[0043] It's also important to understand that the pH at which hexamethylenetetramine sulfate is formed is relatively high (nearly neutral, approximately 5-6). The protons (H+) of the sulfuric acid first protonate a nitrogen atom in the hexamethylenetetramine molecule, forming the monoamine salt. Under these conditions, the reaction is mild and the degree of protonation is low, resulting in the formation of the monoamine salt.

[0044] The pH value is slightly lower (about 4-5) when forming the diamine salt of methenamine sulfate. As the pH decreases and the temperature increases moderately, the protons in the sulfuric acid can protonate with the two nitrogen atoms in the methenamine molecule to form the diamine salt. Under these conditions, the reaction is accelerated, allowing both nitrogen atoms to react with the sulfuric acid.

[0045] The pH value for the formation of hexamethylenetetramine sulfate is lower (approximately 3-4). In a more acidic environment and at higher temperatures, the protonation of sulfuric acid is enhanced, sufficient to react with the three nitrogen atoms in the hexamethylenetetramine molecule to form the triamine salt. Longer reaction times ensure sufficient reaction conversion rates.

[0046] The lowest pH value (2-3) is required to form hexamethylenetetramine sulfate. Under strong acidic conditions, high temperature, and prolonged reaction time, sulfuric acid can maximize its protonation effect, reacting with all four nitrogen atoms in the hexamethylenetetramine molecule to form the tetramine salt. Under these conditions, the reaction achieves the highest degree of protonation.

[0047] It is understood that all of these reactions involve protonation reactions between sulfuric acid and hexamethylenetetramine, and as the reaction conditions (especially pH) become more stringent, the number of protonated nitrogen atoms in the amine salts produced by the reactions increases.

[0048] After the above chemical reaction is completed, the ammonium sulfate and hexamethylenetetramine sulfate need to be recovered through a physical separation process, while ensuring that the wastewater meets the standards for safe discharge or further treatment.

[0049] Specifically,

[0050] First, use a rotary evaporator to evaporate some of the water at a controlled temperature (no higher than 60°C) to concentrate the sulfate in the solution. This step reduces the volume required for subsequent crystallization and improves efficiency. The concentrated solution is then cooled to 5°C to promote sulfate crystallization. Mechanical stirring is used to ensure a uniform crystallization process.

[0051] After crystallization is complete, the mixture is transferred to a centrifuge for separation. The centrifugation speed is set to 4000 rpm and the duration is 10 minutes to ensure effective separation of solid and liquid.

[0052] The separated solid was then washed with deionized water to remove the mother liquor remaining on the surface and then dried in a vacuum drying oven at 80°C to a constant weight to obtain pure ammonium sulfate and hexamethylenetetramine sulfate.

[0053] Although exemplary embodiments of the present disclosure have been described, it will be understood by those skilled in the art that various changes and modifications may be made to the exemplary embodiments of the present disclosure without departing substantially from the spirit and scope of the present disclosure. Therefore, all such changes and modifications are intended to be within the scope of protection of the present disclosure as defined by the appended claims. The present disclosure is defined by the appended claims, and equivalents of these claims are intended to be included therein.

Claims

1. A method for treating wastewater containing ammonia and hexamethylenetetramine, characterized in that: The specific steps are as follows: Step 1: mixing the wastewater containing ammonia and hexamethylenetetramine with sulfuric acid to react, and controlling the pH value within the range of 2-6; Step 2: After the reaction is completed, ammonium sulfate and hexamethylenetetramine sulfate are recovered from the wastewater after the reaction using a physical process or membrane treatment technology.

2. A method for treating wastewater containing ammonia and hexamethylenetetramine as claimed in claim 1, characterized in that: Before step 1, a pretreatment step is also included: collecting wastewater containing ammonia and hexamethylenetetramine, and removing large particle impurities through preliminary filtration.

3. A method for treating wastewater containing ammonia and hexamethylenetetramine as claimed in claim 1, characterized in that: In step 1, under the pH conditions, ammonia reacts with sulfuric acid to generate ammonium sulfate, and simultaneously urotropine reacts with sulfuric acid to generate at least one of urotropine sulfate monoamine salt, diamine salt, triamine salt and tetraamine salt.

4. A method for treating wastewater containing ammonia and hexamethylenetetramine as claimed in claim 1, characterized in that: The reaction temperature in step 1 is 10-60°C.

5. A method for treating wastewater containing ammonia and hexamethylenetetramine as claimed in claim 1, characterized in that: In step 1, the pH is 5-6. Under these conditions, the protons (H+) of the sulfuric acid first react with a nitrogen atom in the hexamethylenetetramine molecule to form an amine salt. Under these conditions, the reaction is mild and the degree of protonation is low, so the amine salt is primarily produced.

6. A method for treating wastewater containing ammonia and hexamethylenetetramine as claimed in claim 1, characterized in that: In step 1, the pH value is 4-5. Under such conditions, the protons in the sulfuric acid can undergo a protonation reaction with two or three nitrogen atoms in the hexamethylenetetramine molecule to form a diamine salt or a triamine salt.

7. A method for treating wastewater containing ammonia and hexamethylenetetramine as claimed in claim 1, characterized in that: In step 1, the pH value is 2-3. Under such conditions, sulfuric acid can exert its protonation effect to the greatest extent and react almost completely with the nitrogen atom in the hexamine molecule to form a triamine salt or a tetraamine salt.

8. A method for treating wastewater containing ammonia and hexamethylenetetramine as claimed in claim 1, characterized in that: The physical process adopted in step 2 is one of evaporation and crystallization centrifugation.

9. A method for treating wastewater containing ammonia and hexamethylenetetramine as claimed in claim 1, characterized in that: After the wastewater is treated in step 2, the wastewater from which the ammonia and hexamine components are removed is directly purified using biological water treatment technology to meet environmental emission standards.

10. A method for treating wastewater containing ammonia and hexamethylenetetramine as claimed in claim 1, characterized in that: After the wastewater is treated in step 2, it is directly returned to the production system for use as absorption liquid, thus realizing the recycling of water resources.