A method for treating UV light-cured monomer wastewater

Abstract

The application discloses a kind of UV light curing monomer wastewater treatment methods, wastewater pH is adjusted to 3.0~5.0 in the application, after using coagulant to remove suspended solids, into micro-nano bubble reactor carries out demulsification and preliminary chain breaking;Effluent enters the heterogeneous catalytic ozone reactor with manganese, cerium and other composite metal oxides as catalyst, macromolecular organic matter is degraded into small molecule with strong biodegradability;Finally, effluent is completed in SBBR reactor filled with biological affinity combined packing Complete biodegradation.The application can solve the problems such as low efficiency, easy to scale, and easy to collapse of biochemical system when the prior art is used to treat such wastewater through process coupling and strengthening, each unit synergistically, has the advantages of excellent treatment effect, stable operation, less secondary pollution, low cost, etc., and the effluent can be stably discharged up to standard.

Description

Technical Field

[0001] This invention relates to a method for treating UV-cured monomer wastewater, particularly a comprehensive treatment method for acrylate monomer wastewater, belonging to the field of industrial wastewater treatment. Background Technology

[0002] UV curing technology is widely used in coatings, inks, adhesives, 3D printing, and other fields due to its high efficiency, energy saving, and environmental friendliness. Its core raw material is UV-curable monomers, mainly acrylate compounds such as isobornyl acrylate, tripropylene glycol diacrylate, and trimethylolpropane triacrylate. The production process generates a large amount of wastewater containing a significant amount of acrylate monomers.

[0003] This type of wastewater has the following significant characteristics and treatment challenges: high toxicity, poor biodegradability, low chemical stability, and a tendency to polymerize.

[0004] Currently, the main treatment methods for this type of wastewater include: physical methods, such as distillation, but the monomers have high boiling points, are prone to polymerization and scaling, and consume a lot of energy; ordinary chemical oxidation methods, the monomers are highly hydrophobic, have poor dispersibility in the aqueous phase, and have limited contact with homogeneous catalysts and oxidants; and require a large amount of acid and alkali to adjust the pH value, generating a large amount of hazardous iron sludge; and biological methods, which directly use aerobic or anaerobic biological treatment, but microorganisms are easily poisoned and inactivated, making it difficult to start up and operate the system stably.

[0005] Therefore, developing an efficient, stable, economical method for treating UV-cured monomer wastewater with minimal secondary pollution has become a pressing technical challenge for the industry. Summary of the Invention

[0006] Purpose of the invention: The purpose of this invention is to overcome the shortcomings of the prior art and provide a combined treatment method for UV photocurable monomer wastewater that has high treatment efficiency, stable operation, and low secondary pollution.

[0007] Technical solution: To achieve the above objectives, the technical solution adopted by this invention is as follows:

[0008] A system for treating UV-cured monomer wastewater includes an equalization tank, a micro / nano bubble reactor, a heterogeneous catalytic ozone reactor, and a sequencing batch reactor connected in sequence.

[0009] A method for treating UV-cured monomer wastewater, the core of which lies in the combined process of "micro-nano bubble pre-oxidation and demulsification and preliminary chain breaking - heterogeneous catalytic ozone deep oxidation - sequencing batch biofilm reactor (SBBR) biochemical degradation", including the following steps:

[0010] (1) Pretreatment: Adjust the pH of the wastewater to 3-5, add composite coagulant (polyaluminum chloride PAC and diatomaceous earth in a mass ratio of 1:1) and coagulant aid polyacrylamide PAM, stir and let it stand to settle, and remove suspended solids and some colloidal pollutants.

[0011] Water is introduced into a micro-nano bubble reactor, ozone is introduced through a micro-nano bubble generator, and hydrogen peroxide is added. At the same time, a catalyst containing ferrous ions is added to the reactor to carry out a Fenton-like reaction. The reaction time is controlled to be 10-60 minutes, preferably 15-45 minutes.

[0012] (2) Heterogeneous catalysis: The effluent from step (1) is introduced into a fixed bed or fluidized bed reactor containing a supported particulate catalyst, and ozone is introduced from the bottom. The reaction time is 10 to 90 minutes, preferably 30 to 90 minutes.

[0013] (3) Sequencing batch biofilm reactor (SBBR) biochemical treatment: After adjusting the pH value of the effluent from step (2) to 7.0-8.5, it is introduced into a sequencing batch biofilm reactor (SBBR) for biochemical treatment. The reactor is filled with bio-affinity composite packing material and operates in a periodic circulation mode.

[0014] As a preferred embodiment, in step (1) above, the composite coagulant is polyaluminum chloride (PAC) with a mass ratio of 1:(1~1.5) to diatomaceous earth, and the addition amount is 1~5 parts per ten thousand; the coagulant aid is polyacrylamide (PAM), and the addition amount is 1~5 parts per ten thousand; the micro-nano bubble generator has a micro-nano bubble diameter range of 50 nanometers to 50 micrometers; the molar ratio of hydrogen peroxide to ferrous ions in the ferrous salt is (2~4:1), preferably 3:1.

[0015] As a preferred embodiment, the active component of the supported catalyst in step (2) above is at least two of the oxides of manganese, cerium, and copper, wherein the loading of manganese is 1-5% by mass, the loading of cerium is 0.5-2% by mass, the loading of copper is 1-6% by mass, and the support is at least one or a mixture of several of activated alumina or molecular sieves.

[0016] As a preferred option, in step (3) above, the bio-affinity composite packing is a combination of polyurethane sponge blocks and polypropylene multifaceted hollow spheres, with a filling rate of 25% to 40% of the effective volume of the sequencing batch biofilm reactor. The single operating cycle of the sequencing batch biofilm reactor is 5 to 8 hours, of which the aeration reaction stage lasts for 4 to 8 hours.

[0017] The beneficial effects of this invention are as follows: This invention is the first to propose a relay-style combined process of "micro-nano bubble pre-oxidation - heterogeneous catalytic ozonation - SBBR biochemical treatment". Utilizing the unique physicochemical properties of micro-nano bubbles, the Fenton-like reaction is enhanced, reducing reagent dosage (saving 20-40% compared to the traditional Fenton method). Through the development of a manganese-cerium bimetallic supported catalyst, efficient activation of ozone and targeted attack on the organic molecular framework are achieved. Combined with the sequencing batch reactor (SBBR) operation mode, which offers advantages such as resistance to shock loads and long sludge age, and combined with high-affinity packing materials, a microbial ecosystem primarily degrading small molecule esters and alcohols can be rapidly established and stably maintained in wastewater, achieving true wastewater harmlessness, meeting low VOC emission requirements, and possessing significant economic value. This invention solves the problems of low efficiency, high cost, and severe secondary pollution associated with traditional processes for treating photocurable monomer wastewater, and has significant industrial application value. Detailed Implementation

[0018] The present invention will be further described below with reference to embodiments, but the embodiments do not constitute a limitation on the scope of protection of the present invention:

[0019] Example 1

[0020] A method for treating UV-cured monomer wastewater includes the following steps:

[0021] (1) When the acrylate monomer wastewater enters the equalization tank, the pH is adjusted to 4.2 with dilute sulfuric acid. Then, a composite coagulant (polyaluminum chloride PAC and diatomaceous earth in a mass ratio of 1:1) and a coagulant aid polyacrylamide PAM with a mass fraction of 0.03% are added. After stirring, the mixture is allowed to settle to remove suspended solids and some colloidal pollutants.

[0022] The wastewater was then introduced into a micro-nano bubble reactor, where ozone and hydrogen peroxide were introduced through a micro-nano bubble generator (bubble diameter approximately 200 nm to 20 μm). The ozone dosage was 4.5 g / L of wastewater, the hydrogen peroxide (30%) dosage was 8.5 mL / L, and the ferrous sulfate heptahydrate dosage was 3.8 g / L. The reaction was carried out for 30 minutes.

[0023] (2) The above effluent enters a fixed-bed catalytic ozone reactor filled with Mn-Ce catalyst (Mn loading 3%, Ce loading 1.2%) and active alumina as the carrier, and ozone gas (ozone concentration 40 mg / L) is introduced from the bottom and reacted for 60 minutes.

[0024] (3) After adjusting the pH of the above effluent to 7.8 with liquid alkali, it enters the SBBR reactor. The reactor is filled with a combination of polyurethane sponge and polypropylene hollow spheres (volume ratio 2:1), with a filling rate of 35%. The operating cycle is 8 hours, including 0.5 hours of influent (stirring), 6 hours of aeration reaction, 1 hour of sedimentation, and 0.5 hours of effluent discharge. After 20 days of acclimatization, the system operates stably.

[0025] After stable operation, in accordance with the HJ 828-2017 standard, the COD of the effluent was found to be below 10 mg / L, and the water was clear, transparent and odorless, meeting the Class I standard of the Integrated Wastewater Discharge Standard (GB8978-1996).

[0026] Example 2

[0027] The processing steps are basically the same as in Example 1, except that:

[0028] In step (1), the ozone dosage is increased to 7.0 g / L and the reaction time is extended to 40 minutes.

[0029] In step (2), the catalyst is replaced with Mn-Cu (Mn loading 3%, Cu loading 2%), the support is molecular sieve, and the ozone reaction time is extended to 80 minutes.

[0030] In step (3), the SBBR operating cycle is adjusted to 10 hours (7.5 hours of aeration).

[0031] After stable operation, the final effluent COD was tested using the same method as in Example 1 and found to be stable at 20–35 mg / L, meeting the discharge standards.

[0032] Comparative Example 1 (Traditional Fenton + Biochemical)

[0033] The same acrylate monomer wastewater as in Example 1 was used, but after treatment with only the conventional Fenton process (adjusting pH to 3.0, adding 12 mL / L FeSO4, and then adjusting pH back to 8 for precipitation), the effluent COD was 4800 mg / L, and a large amount of iron sludge was produced. This water sample was then further treated in an SBBR biological treatment system, where the microorganisms became severely poisoned and inactive after 5 days, leading to system collapse.

[0034] Comparative Example 2 (Ordinary microbubbles + ozone + biochemical)

[0035] The heterogeneous catalytic ozonation step is missing, meaning that the pH is directly adjusted after step (1) before entering the SBBR. Although the SBBR system has been acclimatized for up to 40 days, it can only remove about 45% of the COD, and the COD of the effluent is still around 1700 mg / L, which cannot meet the standard.

[0036] By comparing the examples and comparative examples, the indispensability and synergistic effect of each step of the combined process in this invention are demonstrated, especially the decisive role of heterogeneous catalytic ozonation in improving biodegradability in step (2), and the significant advantages of the entire process in treating such recalcitrant and highly toxic wastewater.

[0037] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A system for treating UV-curable monomer wastewater, characterized in that, It comprises a conditioning tank, a micro / nano bubble reactor, a heterogeneous catalytic ozone reactor, and a sequencing batch biofilm reactor connected in sequence.

2. A method for treating UV-cured monomer wastewater, characterized in that, Includes the following steps: Pretreatment: First, adjust the pH of the wastewater to 3-5, add composite coagulant and coagulant aid, stir and let it settle to remove suspended solids and some colloidal pollutants; introduce water into a micro-nano bubble reactor, introduce ozone through a micro-nano bubble generator and add hydrogen peroxide, and at the same time, add ferrous salt catalyst containing ferrous ions into the reactor to carry out a Fenton-like reaction, controlling the reaction time to 10-60 minutes; Heterogeneous catalysis: The effluent from step (1) is introduced into a fixed bed or fluidized bed reactor containing a supported particulate catalyst, and ozone is introduced from the bottom for a reaction time of 10 to 90 minutes. Sequencing batch biofilm reactor (SBBR) biochemical treatment: After adjusting the pH value of the effluent from step (2) to 7.0-8.5, it is introduced into a sequencing batch biofilm reactor (SBBR) for biochemical treatment. The reactor is filled with bio-affinity composite packing material and operates in a cyclic circulation mode.

3. The method for treating UV-cured monomer wastewater as described in claim 2, characterized in that, In step (1), the composite coagulant is polyaluminum chloride (PAC) with a mass ratio of 1:(1~1.5) to diatomaceous earth, and the addition amount is 1~5 parts per ten thousand. The coagulant is polyacrylamide (PAM), and the addition amount is 1 to 5 parts per ten thousand.

4. The method for treating UV-cured monomer wastewater as described in claim 2, characterized in that, In step (1), the diameter of the micro-nano bubble generator ranges from 50 nanometers to 50 micrometers; the molar ratio of hydrogen peroxide to ferrous ions in ferrous salt is (2~4:1).

5. The method for treating UV-cured monomer wastewater as described in claim 1, characterized in that, In step (2), the active components of the supported particulate catalyst are at least two of the oxides of manganese, cerium, and copper, wherein the loading of manganese is 1-5% by mass, the loading of cerium is 0.5-2% by mass, and the loading of copper is 1-6% by mass; the support is at least one or a mixture of several of activated alumina or molecular sieves.

6. The method for treating UV-cured monomer wastewater as described in claim 1, characterized in that, In step (3), the bio-affinity composite packing is a combination of polyurethane sponge blocks and polypropylene multifaceted hollow spheres, with a filling rate of 25% to 40% of the effective volume of the sequencing batch reactor.

7. The method for treating UV-cured monomer wastewater as described in claim 1, characterized in that, In step (3), the single operating cycle of the sequencing batch biofilm reactor is 5 to 8 hours, of which the aeration reaction stage lasts 4 to 8 hours.