A method for recycling a paint-containing solution

Abstract

The present application relates to waste liquid treatment technical field, disclose a kind of paint-containing solution recycling method, the method includes: salt-tolerant surface active system is handled to waste liquid particle surface modification, salinity adaptive type ozone microbubble oxidation degradation organic pollutant, and the recovery of valuable components is combined by permeability pressure regulation biological flocculation and selective extraction;The present application solves the technical bottleneck of low efficiency of traditional treatment method under high salinity environment, significantly improves the treatment efficiency and resource recovery rate, reduces the processing cost, realizes the efficient reuse of paint-containing waste liquid.

Description

Technical Field

[0001] This invention relates to the field of waste liquid treatment technology, and more specifically, to a method for reusing paint-containing solutions. Background Technology

[0002] Paint-containing wastewater is a common industrial wastewater generated during the production processes of the coatings industry, automobile manufacturing, ship repair, and furniture production. It contains a large amount of valuable components such as recyclable solvents and resins. Currently, the main methods for treating paint-containing wastewater include chemical treatment and physical separation methods. While chemical treatment methods are highly efficient, they typically introduce large amounts of chemical reagents, causing secondary pollution. Physical separation methods, such as distillation and filtration, while having better environmental performance, suffer from high energy consumption, low recovery rates, and incomplete separation.

[0003] For the treatment of paint-containing wastewater, the industry has developed improved methods such as bioflocculation-extraction combined technology and surfactant modification-oxidative degradation technology. Bioflocculation-extraction combined technology utilizes the synergistic effect of bioflocculation agents and selective extractants to effectively reduce secondary pollution; the combination of surfactant modification and oxidative degradation improves treatment efficiency by altering particle surface properties and degrading organic matter. However, these technologies all exhibit significant limitations when dealing with high-salinity paint-containing wastewater (such as wastewater generated from marine engineering and ship repair industries). High salinity environments limit the effectiveness of surfactants, reduce oxidation efficiency, and inhibit the activity of bioflocculation agents, resulting in a significant decrease in the efficiency of traditional treatment processes. Summary of the Invention

[0004] This invention provides a method for reusing paint-containing solutions, solving the technical problem in related technologies of "how to develop a method for reusing paint-containing solutions that can operate efficiently in a high-salinity environment, taking into account the special characteristics of high-salinity paint-containing waste liquid, so as to achieve efficient recovery of valuable components and resource recycling".

[0005] A method for reusing paint-containing solutions includes the following steps:

[0006] Step 1: Pre-treat the high-salinity paint waste liquid to remove large particulate impurities and measure the basic parameters of the waste liquid.

[0007] Step 2: Add a salt-tolerant surfactant system to the pretreated waste liquid and stir and mix it at a temperature of 20-40℃ and a pH of 6-8 to ensure that the surfactant system is in full contact with the waste liquid and to complete the surface property modification.

[0008] Step 3: Place the waste liquid treated by the surface-active system into a reaction vessel, and introduce ozone microbubbles using a salinity-adaptive ozone generator and a microporous diffusion device. Carry out the oxidation reaction at a temperature of 20-35℃ until the COD reduction rate of the waste liquid reaches the preset value.

[0009] Step 4: Add an osmotic pressure control system and a biological flocculant to the oxidized waste liquid for flocculation treatment, so that the organic matter forms flocs, and let it stand to allow the flocs to mature.

[0010] Step 5: Selectively extract the layer or floc containing high concentrations of paint components to recover the paint components and solvents. The treated wastewater meets the discharge standards.

[0011] Preferred: The salt-resistant surfactant system includes a main surfactant, an auxiliary surfactant, an ion-shielding agent, and an interface stabilizer, and the amount added is 0.1-1% of the waste liquid volume.

[0012] Preferably, the main surfactant is selected from sodium dodecyl sulfate or sodium lauryl sulfate, the auxiliary surfactant is selected from polyoxyethylene ether or polyvinylpyrrolidone, the ion shielding agent is selected from calcium chloride or magnesium chloride, and the interface stabilizer is selected from α-cyclodextrin or β-cyclodextrin.

[0013] Preferred method: The stirring speed in step two is 100-200 rpm, the stirring time is 30-60 minutes, and the mixture is left to stand for 10-20 minutes after stirring.

[0014] Preferably, the salinity-adaptive ozone generator has a voltage range of 80-120V, a current range of 1.5-3.0A, and a microporous diffusion device with a pore size of 10-50μm.

[0015] Preferred method: In step three, the ozone gas flow rate is 0.5-2.0 L / min, the reaction time is 30-90 minutes, and the oxidation reaction is stopped when the COD reduction rate reaches 40-60%.

[0016] Preferably, step three also includes a sub-step of adding a catalyst to assist oxidation. The catalyst is hydrogen peroxide or a metal ion catalyst, wherein the amount of hydrogen peroxide added is 0.1-0.5% of the waste liquid volume, and the concentration of the metal ion catalyst is 5-20 mg / L.

[0017] Preferred: The osmotic pressure control system consists of polyethylene glycol, γ-cyclodextrin and sodium chloride in a mass ratio of 1:2:3, and its addition amount is 2-8% of the waste liquid volume.

[0018] Preferably, the bioflocculant is selected from chitosan derivatives or modified alginate, and its addition amount is 0.5-1.5% of the waste liquid volume.

[0019] Preferred method: In step five, selective extraction uses a mixture of ethyl acetate or butyl acetate and isopropanol as the extractant, with a volume ratio of extractant to the layer to be extracted of 1:2-2:1, an extraction temperature of 25-35℃, and an extraction time of 20-45 minutes.

[0020] The beneficial effects of this invention are as follows: the method for reusing paint solution proposed in this invention achieves efficient treatment and resource utilization of paint-containing waste liquid, and the specific technical effects are as follows:

[0021] In terms of processing efficiency:

[0022] The COD removal rate in the waste liquid reaches 85-95%, which is significantly higher than the 60-70% of conventional treatment methods;

[0023] The processing cycle has been shortened from 5-7 days using traditional methods to less than 24 hours;

[0024] The process energy consumption is reduced by 40-50%, mainly due to a significant reduction in the energy consumption of oxidation treatment.

[0025] Regarding high-salt adaptability:

[0026] This method can effectively treat paint-containing wastewater with a salinity of up to 50,000 mg / L, while conventional biochemical treatment methods are only suitable for wastewater with a salinity of less than 10,000 mg / L.

[0027] In the treatment of high-salinity wastewater with a salinity of 30,000-40,000 mg / L, the COD removal rate can still reach over 80%, while conventional methods typically achieve a removal rate of less than 30% at this salinity.

[0028] The treatment effect is not significantly affected by salinity fluctuations; when the salinity changes by ±5000 mg / L, the change in treatment effect does not exceed 5%.

[0029] Regarding resource recycling:

[0030] The paint component recovery rate reaches 65-80%, and the recovered paint components can be reused as paint additives.

[0031] The purity of the recovered solvent can reach over 95%, and it can be directly used in the production process;

[0032] The salt in the waste liquid can be recycled to produce industrial-grade sodium chloride with a purity of over 90%.

[0033] In terms of environmental friendliness:

[0034] The biotoxicity of the treated wastewater is reduced by more than 90%, and it can be safely discharged or further treated.

[0035] The entire treatment process does not generate secondary pollution and has no harmful gas emissions;

[0036] More than 94% of the chemicals and materials used in the process are biodegradable or recyclable.

[0037] In terms of economic benefits:

[0038] Compared with traditional processing methods, the total processing cost is reduced by 30-40%;

[0039] Through resource recycling, 40-60% of the value can be recovered;

[0040] The payback period for equipment investment has been shortened to 1.5-2 years, significantly lower than the industry average.

[0041] In terms of scalability:

[0042] This process is applicable to the treatment of paint-containing waste liquids in various industries such as coatings, paints, and inks;

[0043] The processing capacity can be flexibly adjusted from small (1 ton / day) to large (100 tons / day);

[0044] The process flow can be modularly designed, making it easy to configure according to the characteristics of different waste liquids.

[0045] The significant advantage of this invention lies in solving the long-standing triple problem of "high salt, high COD, and poor biodegradability" in the field of paint wastewater treatment, and realizing the organic combination of wastewater treatment and resource recovery. Through the synergistic effect of three core steps—surfactant modification, salt-adaptive ozone microbubble oxidation, and osmotic pressure-controlled bioflocculation—it not only efficiently removes pollutants from wastewater but also selectively recovers valuable components, demonstrating the technical characteristics of being green, efficient, and economical. Attached Figure Description

[0046] Figure 1 This is a comparison of the COD removal efficiency of the treatment method under different salinity conditions of the present invention;

[0047] Figure 2 This describes the trend of biotoxicity changes during the treatment process of this invention;

[0048] Figure 3 This refers to the biodegradability of the materials used in the process of this invention. Detailed Implementation

[0049] The subject matter described herein will now be discussed with reference to exemplary embodiments. It should be understood that these embodiments are discussed only to enable those skilled in the art to better understand and implement the subject matter described herein, and changes may be made to the function and arrangement of the elements discussed without departing from the scope of this specification. Various processes or components may be omitted, substituted, or added as needed in the examples. Furthermore, some features described in the examples may be combined in other examples.

[0050] Example 1

[0051] This embodiment proposes a method for reusing paint-containing solutions, including the following steps:

[0052] Step 1: Pre-treat the high-salinity paint waste liquid to remove large particulate impurities and measure the basic parameters of the waste liquid.

[0053] Step 2: Add the salt-tolerant surfactant system to the pretreated waste liquid, stir and mix at 30℃ and pH 7, at a stirring speed of 150 rpm for 45 minutes, and let stand for 15 minutes after stirring to allow the surfactant system to fully contact the waste liquid and complete the surface property modification.

[0054] The salt-resistant surfactant system includes a main surfactant, auxiliary surfactants, ion-blocking agents, and interface stabilizers, and its addition amount is 0.5% of the waste liquid volume.

[0055] The main surfactant is selected from sodium dodecyl sulfonate, the ion shielding agent is selected from calcium chloride, the auxiliary surfactant is selected from polyoxyethylene ether, and the interface stabilizer is selected from α-cyclodextrin.

[0056] Step 3: Place the waste liquid treated by the surface-active system into a reaction vessel, and introduce ozone microbubbles using a salinity-adaptive ozone generator and a microporous diffusion device. Carry out the oxidation reaction at a temperature of 28°C until the COD reduction rate of the waste liquid reaches the preset value.

[0057] The salinity-adaptive ozone generator has a voltage range of 100V, a current range of 2.2A, and a microporous diffusion device with a pore size of 30μm.

[0058] The ozone gas flow rate was 1.2 L / min, the reaction time was 60 minutes, and the oxidation reaction was stopped when the COD reduction rate reached 450%.

[0059] This step also includes a sub-step of adding a catalyst to assist oxidation. The catalyst is hydrogen peroxide, and the amount of hydrogen peroxide added is 0.3% of the waste liquid volume.

[0060] Step 4: Add an osmotic pressure control system and a biological flocculant to the oxidized waste liquid for flocculation treatment, so that the organic matter forms flocs, and let it stand to allow the flocs to mature.

[0061] The osmotic pressure control system consists of polyethylene glycol, γ-cyclodextrin, and sodium chloride in a mass ratio of 1:2:3, and its addition amount is 5% of the waste liquid volume.

[0062] The bioflocculant is selected from chitosan derivatives, and its addition amount is 1.0% of the waste liquid volume.

[0063] Step 5: Selectively extract the layer or floc containing high concentrations of paint components to recover the paint components and solvents. The treated waste liquid meets the discharge standards.

[0064] Selective extraction used a mixture of ethyl acetate and isopropanol as the extractant, with a volume ratio of extractant to the layer to be extracted of 1:1.5, an extraction temperature of 30℃, and an extraction time of 32 minutes.

[0065] Example 2

[0066] The difference between this embodiment and Embodiment 1 is that:

[0067] In step two, a salt-tolerant surfactant system is added to the pretreated waste liquid. The mixture is stirred at 20°C and pH 6 for 30 minutes at a speed of 100 rpm. After stirring, the mixture is allowed to stand for 10 minutes to allow the surfactant system to fully contact the waste liquid and complete the surface property modification.

[0068] The salt-resistant surfactant system includes a main surfactant, auxiliary surfactants, ion-blocking agents, and interface stabilizers, and its addition amount is 0.1% of the waste liquid volume.

[0069] The main surfactant is selected from sodium lauryl sulfate, the ion-shielding agent is selected from magnesium chloride, the auxiliary surfactant is selected from polyvinylpyrrolidone, and the interface stabilizer is selected from β-cyclodextrin;

[0070] In step three, the oxidation reaction is carried out at a temperature of 20°C until the COD reduction rate of the waste liquid reaches the preset value.

[0071] The salinity-adaptive ozone generator has a voltage range of 80V, a current range of 1.5A, and a microporous diffusion device with a pore size of 10μm.

[0072] The ozone gas flow rate was 0.5 L / min, the reaction time was 30 minutes, and the oxidation reaction was stopped when the COD reduction rate reached 40%.

[0073] This step also includes a sub-step of adding a catalyst to assist oxidation. The catalyst is a metal ion catalyst with a concentration of 5 mg / L.

[0074] In step four, the amount of osmotic pressure control system added is 2% of the waste liquid volume;

[0075] The bioflocculant is selected from modified alginate, and its addition amount is 0.5% of the waste liquid volume.

[0076] In step five, selective extraction uses a mixture of butyl acetate and isopropanol as the extractant, with a volume ratio of extractant to the layer to be extracted of 1:2, an extraction temperature of 25°C, and an extraction time of 20 minutes.

[0077] Example 3

[0078] The difference between this embodiment and Embodiment 1 is that:

[0079] In step two, a salt-tolerant surfactant system is added to the pretreated waste liquid. The mixture is stirred at 40°C and pH 8 for 60 minutes at a speed of 200 rpm. After stirring, the mixture is allowed to stand for 20 minutes to allow the surfactant system to fully contact the waste liquid and complete the surface property modification.

[0080] The salt-resistant surfactant system includes a main surfactant, auxiliary surfactants, ion-blocking agents, and interface stabilizers, and its addition amount is 1% of the waste liquid volume;

[0081] In step three, the oxidation reaction is carried out at a temperature of 35℃ until the COD reduction rate of the waste liquid reaches the preset value.

[0082] The salinity-adaptive ozone generator has a voltage range of 120V, a current range of 3.0A, and a microporous diffusion device with a pore size of 50μm.

[0083] The ozone gas flow rate was 2.0 L / min, the reaction time was 90 minutes, and the oxidation reaction was stopped when the COD reduction rate reached 60%.

[0084] This step also includes a sub-step of adding a catalyst to assist oxidation. The catalyst is hydrogen peroxide, and the amount of hydrogen peroxide added is 0.5% of the waste liquid volume.

[0085] In step four, the amount of osmotic pressure control system added is 8% of the waste liquid volume;

[0086] The amount of bio-flocculator added is 1.5% of the waste liquid volume.

[0087] In step five, the volume ratio of the extractant to the layer to be extracted is 2:1, the extraction temperature is 35℃, and the extraction time is 45 minutes.

[0088] Example 4

[0089] The difference between this embodiment and Embodiment 1 is that:

[0090] In step three, the catalyst is hydrogen peroxide, and the amount of hydrogen peroxide added is 0.1% of the waste liquid volume.

[0091] In step five, the volume ratio of the extractant to the layer to be extracted is 1:1.5.

[0092] Example 5

[0093] The difference between this embodiment and Embodiment 1 is that:

[0094] In step three, the catalyst is a metal ion catalyst with a concentration of 20 mg / L.

[0095] Example 6

[0096] The difference between this embodiment and Embodiment 1 is that:

[0097] In step three, the catalyst is a metal ion catalyst with a concentration of 12 mg / L.

[0098] Example 7

[0099] This embodiment proposes a method for reusing paint-containing solutions, including the following specific steps:

[0100] 1. Raw material pretreatment

[0101] The collected high-salinity paint-containing wastewater underwent simple pretreatment, mainly including:

[0102] 1.1 Filtering removes large particulate impurities;

[0103] 1.2. Clear separation of insoluble heavy components by static sedimentation;

[0104] 1.3. Measure parameters such as salinity, pH value, COD value, and suspended solids content of the waste liquid to provide a basis for subsequent treatment.

[0105] These pretreatment steps are carried out using conventional methods, with the aim of removing coarse impurities that may affect subsequent treatment and obtaining basic information about the waste liquid.

[0106] 2. Salt-resistant surfactant system modification treatment

[0107] This step addresses the problem of complex particle surface properties in high-salinity paint wastewater and the limited effectiveness of traditional surfactants in high-salinity environments. It employs an optimized salt-resistant surfactant system for modification treatment. The specific steps are as follows:

[0108] Based on the salinity of the waste liquid measured in the pretreatment step, a suitable surfactant system is selected from a library of salt-tolerant surfactants. This system mainly consists of the following components:

[0109] Main surfactant: It has an optimized molecular structure, and the ratio and arrangement of hydrophilic and lipophilic groups have been adjusted to maintain activity in a high-salt environment. Sodium dodecyl sulfonate is selected.

[0110] Additive surfactants: They work synergistically with the main surfactant to enhance the overall salt resistance of the system; polyoxyethylene ethers are preferred.

[0111] Ion-shielding agents are divalent cationic coordination stabilizers that can reduce the interference of salt ions on the action of surfactants;

[0112] Divalent cation coordination stabilizers: via divalent cations (Ca... 2+ or Mg 2+It forms a weak coordination complex with the sulfonate or sulfate head group of anionic surfactants, maintaining the effective spatial orientation and charge distribution of the surfactant molecule in a high ionic strength environment, thus protecting its functional groups from a large number of monovalent salt ions (Na+). + Cl - The shielding deactivation caused by the compression of the electric double layer; specifically, calcium chloride (CaCl2) or magnesium chloride (MgCl2) are selected, and their amount is 15% to 25% of the mass of the main surfactant (usually dissolved separately and then mixed with the main surfactant); compared with adding more monovalent salts, divalent cations, due to their higher charge number and stronger coordination selectivity to ionic head groups, can more effectively stabilize the surfactant conformation without further increasing the overall ionic strength of the system at the same molar amount;

[0113] Interface stabilizer: To ensure the stability of the surface properties of the modified particles, α-cyclodextrin is selected.

[0114] The amount of surfactant added is determined according to the characteristics of the waste liquid, usually 0.6% of the waste liquid volume, and is added to the pretreated high-salinity paint-containing waste liquid.

[0115] The mixture was stirred at 30°C and pH 7 to ensure full contact between the surfactant system and the particles in the waste liquid. The stirring time was typically 45 minutes at a speed of 150 rpm.

[0116] After mixing, let stand for 15 minutes to allow the surfactant molecules to fully adsorb onto the particle surface, thus completing the surface property modification.

[0117] This step relies on the optimized molecular structure of the surface-active system used, enabling it to maintain effective modification of particle surfaces under high-salt conditions. Under high ionic strength conditions, the functional groups of conventional surfactants are often destroyed by a large number of monovalent salt ions (Na+). + The compressed electric double layer effect shielding significantly reduces surface activity. This system overcomes this limitation through synergy in three dimensions: the molecular structure of the main surfactant (sodium dodecyl sulfate or sodium lauryl sulfate) is optimized to achieve a hydrophilic / lipophilic group ratio suitable for high-salt environments; the auxiliary surfactant (polyoxyethylene ether or polyvinylpyrrolidone) forms mixed micelles between molecules, improving the overall salt resistance of the system; and the divalent cationic coordination stabilizer (CaCl2 or MgCl2) provides Ca... 2+ / Mg 2+ It forms a weak coordination complex with the head group of anionic surfactants, and its coordination selectivity is better than that of Na. + It can preferentially occupy the coordination sites of the head base in a high-salt environment, protecting the head base from Na+ contamination. +The induced double-layer compression deactivates the surfactant molecules, thereby maintaining their effective adsorption configuration on the particle surface. This step alters the surface properties of the particles in the wastewater, creating favorable conditions for subsequent ozone oxidation and bioflocculation.

[0118] 3. Salinity-adaptive ozone microbubble oxidation treatment

[0119] This step addresses the problem of difficult degradation of organic matter in high-salinity paint-containing wastewater by employing salinity-adaptive ozone microbubble oxidation technology. The specific operation is as follows:

[0120] Preparation for a salinity-adaptive ozone generator:

[0121] An ozone generator made with electrode materials that have salt resistance;

[0122] Based on the salinity of the waste liquid measured in the pretreatment step, adjust the voltage and current parameters of the ozone generator. Typically, the voltage range is 100V and the current range is 2.2A.

[0123] The generating unit is treated with anti-corrosion measures to ensure stable operation in a high-salt environment.

[0124] Setup of the microbubble diffusion device:

[0125] Install the microporous ceramic diffuser head (pore size approximately 10-50 μm) at the bottom of the reaction vessel;

[0126] Connect the ozone generator to the microporous diffuser to ensure unobstructed gas flow;

[0127] Adjust the ozone gas flow rate to 1.2 L / min.

[0128] Oxidation reaction process control:

[0129] Place the waste liquid after surface-active system treatment into a reaction vessel, with the liquid volume not exceeding 2 / 3 of the vessel's capacity;

[0130] Turn on the ozone generator, introduce ozone microbubbles, and begin the oxidation reaction;

[0131] The reaction temperature is controlled within the range of 28℃, and the reaction time is determined according to the COD value of the waste liquid, usually 60 minutes;

[0132] COD values ​​are sampled and tested every 15 minutes. The oxidation reaction is stopped when the COD decrease rate reaches 50%.

[0133] Adding a catalyst to assist oxidation (optional step):

[0134] For waste liquids with particularly high COD values ​​(5000 mg / L), hydrogen peroxide can be added as a synergistic oxidant at a concentration of 0.3% of the waste liquid volume (or metal ion catalysts such as iron and manganese ions can be added at a concentration of 18 mg / L to promote the generation of hydroxyl radicals).

[0135] Post-reaction processing:

[0136] After stopping the ozone supply, continue stirring for 5-10 minutes to allow the residual oxidant to react fully.

[0137] The COD, pH value, and suspended solids content of the treated wastewater were measured to confirm the oxidation effect.

[0138] This step utilizes an ozone generator adapted for high-salt environments and microbubble diffusion treatment, solving the problem of low efficiency in traditional ozone oxidation under high-salt conditions. Microbubble treatment increases the gas-liquid contact area, enhancing ozone mass transfer efficiency; simultaneously, the electrical parameters of the ozone generator are optimized, enabling it to stably produce high-concentration ozone under high-salt conditions. After this step, most of the organic matter in the waste liquid is oxidized and decomposed, significantly improving the biodegradability of the waste liquid and creating conditions for subsequent bioflocculation.

[0139] 4. Osmotic pressure-regulated bioflocculation and selective extraction

[0140] This step achieves efficient separation of organic matter from paint-containing wastewater through the synergistic effect of osmotic pressure regulation and bio-flocculation. The specific operation is as follows:

[0141] Preparation of osmotic pressure regulation system:

[0142] Prepare polyethylene glycol (PEG, molecular weight 1000-4000), γ-cyclodextrin and sodium chloride in a mass ratio of 1:2:3;

[0143] The above substances are mixed and dissolved in an appropriate amount of deionized water to form an osmotic pressure regulating mother liquor.

[0144] Adjust the pH of the mother liquor to 7.0-7.5.

[0145] Osmotic pressure regulating mother liquor metering addition:

[0146] Calculate the amount of osmotic pressure control mother liquor to be added based on the salinity of the waste liquid measured in the previous process.

[0147] The usual addition amount is 2-8% of the waste liquid volume. The specific addition amount is determined as follows:

[0148] When the salinity of the waste liquid is below 5000 mg / L, the addition amount is 2% of the waste liquid volume;

[0149] When the salinity of the waste liquid is between 5000 and 50000 mg / L, the amount added is [2 + (waste liquid salinity - 5000) × 0.001%]% of the waste liquid volume.

[0150] Slowly add the osmotic pressure regulating mother liquor to the waste liquid after ozone oxidation treatment, and stir at a speed of 60-100 r / min.

[0151] Preparation and addition of bio-flocculators:

[0152] Choose one of the following two bioflocculants:

[0153] Chitosan derivatives: Chitosan (degree of deacetylation ≥ 90%) was dissolved in 1% acetic acid solution at a concentration of 10 g / L;

[0154] Add the selected bio-flocculator slowly at a ratio of 0.5-1.5% of the waste liquid volume;

[0155] Stir rapidly at 100 rpm for 4 minutes, then reduce to 40 rpm and stir slowly for 18 minutes.

[0156] Floc formation and maturation process:

[0157] After stopping stirring, let it stand for 30 minutes to allow the flocs to fully mature;

[0158] During the maturation process, the osmotic pressure regulation system and the bioflocculant work together to promote the aggregation of organic matter into the flocs through the osmotic pressure gradient;

[0159] Observe the formation of flocs; the flocs should be brownish-red and have a compact structure.

[0160] Multilayer separation and selective extraction of paint components:

[0161] Based on the settling of the flocs, the waste liquid forms distinct stratification, usually 3-4 layers;

[0162] Collect each layer of liquid separately using a siphon method or a stratified sampling device;

[0163] The following method was used for selective extraction of layers containing high concentrations of paint components:

[0164] Add a mixture of ethyl acetate or butyl acetate and isopropanol (volume ratio 7:3) as an extractant, with the volume ratio of extractant to liquid layer being 1:3 to 3:1;

[0165] The extraction temperature was controlled at 30℃, and the extraction time was 25 minutes.

[0166] After extraction, the mixture is allowed to stand and separate into layers. The organic layer is then separated, and the solvent and paint components are recovered.

[0167] This step combines osmotic pressure regulation with bioflocculation, creating an osmotic pressure gradient to promote the directional migration of organic matter in the solution and its capture by the bioflocculator. This method overcomes the inefficiency of traditional flocculation techniques in high-salt environments while achieving selective recovery of paint components. Gamma-cyclodextrin in the osmotic pressure regulation system provides selective recognition of paint components, while polyethylene glycol regulates the osmotic pressure balance of the entire system; their synergistic effect makes the flocculation process more efficient and selective.

[0168] To verify the technical effectiveness of this invention, we conducted the following experiments and tests. Through experimental data and comparative analysis, we demonstrated the superior performance of this method in treating high-salinity paint-containing wastewater.

[0169] 1. Processing efficiency experiment

[0170] 1.1 Experimental Objective

[0171] The advantages of the method of the present invention in terms of COD removal rate, treatment cycle and energy consumption when treating paint-containing waste liquid were verified.

[0172] 1.2 Experimental Methods

[0173] Comparison group settings:

[0174] Method A (the method of this invention): Salt-tolerant surfactant system modification + salinity-adaptive ozone microbubble oxidation + osmotic pressure-controlled bioflocculation and extraction;

[0175] Method B (Traditional Chemical Treatment): Chemical coagulation + Advanced oxidation + Activated carbon adsorption;

[0176] Method C (traditional physical and biochemical method): membrane filtration + conventional biochemical treatment.

[0177] Experimental Samples: Three different sources of paint-containing wastewater samples were used. The characteristics of each sample are as follows:

[0178] Sample 1: Ship repair waste liquid, salinity 35000 mg / L, initial COD 14500 mg / L;

[0179] Sample 2: Automotive painting wastewater, salinity 15000 mg / L, initial COD 12000 mg / L;

[0180] Sample 3: Wastewater from paint production, salinity 25000 mg / L, initial COD 16000 mg / L.

[0181] Experimental steps:

[0182] Take 500 mL of each type of waste liquid sample and treat them using three different methods.

[0183] Each experiment was repeated three times, and the average value was taken as the final result.

[0184] Record the time, energy consumption, and COD value at each stage of the entire processing.

[0185] Test metrics:

[0186] COD removal rate: The COD values ​​before and after treatment were determined using the potassium dichromate method;

[0187] Treatment cycle: Record the time required from the start of treatment to achieving emission standards;

[0188] Energy consumption: Total electrical energy consumed during the recording and processing process (kWh / m³) 3 Waste liquid).

[0189] 1.3 Experimental Results

[0190] COD removal rate comparison

[0191]

[0192] Comparison of processing cycles

[0193]

[0194] Energy consumption comparison

[0195]

[0196] 1.4 Results Analysis

[0197] COD Removal Rate: The method of this invention (Method A) showed a significantly higher COD removal effect than the traditional method in all samples, with an average removal rate of 93.5%, while the traditional chemical treatment method (Method B) and the traditional physical-biochemical method (Method C) were only 68.0% and 53.3%, respectively. This proves that the method has a significant efficiency advantage in treating high-salinity paint-containing wastewater.

[0198] Processing cycle: The average processing time of the method of this invention is 18.7 hours, which is much shorter than the 48.0 hours of traditional chemical treatment methods and the 120.0 hours of traditional physical-biochemical methods. The processing cycle is shortened by 60-85%, which greatly improves the processing efficiency and reduces the storage space and time costs of waste liquid.

[0199] Energy consumption analysis: The average energy consumption of the method of this invention is 28.4 kWh / m². 3 This method saves approximately 46% of energy compared to traditional chemical treatment methods and approximately 57% of energy compared to traditional physical and biochemical methods. This is mainly due to the salinity-adaptive ozone microbubble technology, which improves oxidation efficiency, and the osmotic pressure-controlled bioflocculation, which reduces energy consumption in the separation process.

[0200] The experimental results above show that the method of the present invention has significant advantages in the efficiency of treating high-salinity paint wastewater. It not only has a high COD removal rate, but also a short treatment cycle and low energy consumption, fully realizing the performance indicators described in the technical effect.

[0201] 2. High salt adaptability experiment

[0202] 2.1 Experimental Objective

[0203] The effectiveness of the method of the present invention under different salinity conditions was verified, especially its adaptability and stability under high salinity conditions.

[0204] 2.2 Experimental Methods

[0205] Experimental Design:

[0206] Select paint waste liquid samples from the same source (paint factory waste liquid, initial COD 13500 mg / L).

[0207] The salinity of the waste liquid was adjusted to different levels by adding NaCl solutions of varying concentrations.

[0208] The samples were treated using the method of this invention and a control method (traditional biochemical treatment method), respectively.

[0209] The experiment was repeated 3 times under each salinity condition, and the average value was taken.

[0210] Salinity settings: Set up 5 waste liquid samples with different salinity levels:

[0211] Low salinity: 5,000 mg / L;

[0212] Low to medium salinity: 15,000 mg / L;

[0213] Medium salinity: 25,000 mg / L;

[0214] Medium to high salinity: 35,000 mg / L;

[0215] High salinity: 50,000 mg / L.

[0216] Test metrics:

[0217] Key indicator: COD removal rate;

[0218] Auxiliary indicators: biotoxicity removal rate, treatment time change rate.

[0219] Analysis method:

[0220] COD determination: potassium dichromate method;

[0221] Biotoxicity assay: luminescent bacteria inhibition method;

[0222] Data processing: Analysis of variance and regression analysis were used.

[0223] 2.3 Experimental Results

[0224] Comparison of COD removal rates under different salinities

[0225]

[0226] Salinity fluctuation adaptability test

[0227] To test the adaptability of the method of this invention to salinity fluctuations, we artificially adjusted the salinity of the waste liquid during the treatment process and observed the changes in COD removal rate. The specific settings are as follows:

[0228] Initial salinity: 25,000 mg / L;

[0229] During the treatment, the salinity was suddenly increased to 30,000 mg / L (+5,000).

[0230] During the treatment, the salinity was suddenly reduced to 20,000 mg / L (-5,000).

[0231]

[0232] Figure 1 The study compares the COD removal efficiency of different treatment methods under varying salinity conditions.

[0233] Correlation analysis between salinity and treatment efficiency:

[0234] By performing regression analysis on the experimental data, we derived prediction models for COD removal rates under different salinity conditions using the method of this invention and traditional methods:

[0235] The method of this invention: COD removal rate (%) = 98.5 - 0.00028 × salinity (mg / L);

[0236] Traditional biochemical treatment method: COD removal rate (%) = 90.2 - 0.00168 × salinity (mg / L);

[0237] As can be seen from the above regression equation, as salinity increases, the slope of the COD removal rate of the method of the present invention (0.00028) is significantly smaller than that of the traditional method (0.00168), which quantitatively proves the superior stability of the method of the present invention in a high-salt environment.

[0238] 2.4 Results Analysis

[0239] High-salt adaptability: The experimental results clearly show that as the salinity of the wastewater increases, the COD removal rate of traditional biochemical treatment methods drops sharply. When the salinity reaches 50,000 mg / L, the removal rate is only 8.5%, essentially failing. However, the method of this invention can maintain a COD removal rate of 84.2% even in high-salt environments, demonstrating extremely strong high-salt adaptability.

[0240] Salinity fluctuation stability: In the salinity fluctuation experiment, when the salinity changed suddenly, the processing efficiency of the method of the present invention changed by no more than 3%, while the traditional method changed by as much as 20.7%. This proves that the method of the present invention has a strong adaptability to salinity fluctuations and can effectively cope with the situation of unstable salinity in actual industrial production.

[0241] Processing efficiency gradient: As salinity increases, the efficiency gap between the method of the present invention and the traditional method gradually widens. Under extremely high salinity conditions of 50,000 mg / L, the efficiency of the method of the present invention is 9.91 times that of the traditional method, which fully demonstrates its significant advantages in high-salt environments.

[0242] Process Mechanism Analysis: Based on experimental data and processing mechanisms, the key to maintaining high efficiency in high-salt environments lies in the following:

[0243] Salt-resistant surfactant systems can maintain effective modification of particle surfaces even under high ionic strength;

[0244] Salinity-adaptive ozone microbubble technology ensures oxidation efficiency in high-salt environments;

[0245] Osmotic pressure regulation mechanisms enable bioflocculants to maintain their activity in high-salt environments.

[0246] This experiment fully verifies the adaptability and stability of the method of the present invention in high-salt environments. In particular, it can still maintain good treatment effect under extremely high salinity conditions where traditional methods are almost ineffective, providing an effective solution for the treatment of high-salinity paint waste liquid.

[0247] 3. Resource recycling experiment

[0248] 3.1 Experimental Objective

[0249] The effectiveness of the method of the present invention in resource recovery was verified, including the recovery rate of paint components, solvent purity, and feasibility of salt recovery.

[0250] 3.2 Experimental Methods

[0251] Experimental Design:

[0252] Three typical types of paint-containing wastewater were selected for treatment:

[0253] Epoxy paint waste liquid (EP): mainly contains epoxy resin and organic solvents;

[0254] Acrylic paint waste liquid (AC for short): mainly contains acrylic resin and water-soluble components;

[0255] Polyurethane paint waste liquid (PU for short): mainly contains polyurethane resin and mixed solvents;

[0256] Each type of waste liquid was treated using the method of this invention and a control method (conventional extraction method);

[0257] Each treatment method was repeated three times, and the average value was used to evaluate the resource recovery effect.

[0258] Resource recycling steps:

[0259] Paint component recovery: Collect the flocculent precipitate and extract the resin components using selective extraction;

[0260] Solvent recovery: The recovery of organic solvents separated during the treatment process through distillation;

[0261] Salt recovery: Inorganic salts are recovered from treated wastewater using an evaporation crystallization method.

[0262] Test metrics:

[0263] Paint component recovery rate (%): Amount of resin recovered / Total amount of resin in the original waste liquid × 100%;

[0264] The purity of the recovered solvent (%) was determined by gas chromatography.

[0265] Salt recovery rate (%): Amount of salt recovered / Total amount of salt in the original waste liquid × 100%;

[0266] Application performance of recycled materials: The reuse value of recycled materials is evaluated using standard testing methods.

[0267] 3.3 Experimental Results

[0268] 1) Comparison of paint component recovery rates

[0269]

[0270] 2) Comparison of the purity of recovered solvents

[0271]

[0272] 3) Salt recovery effect

[0273]

[0274] 4) Performance testing of recycled resources

[0275] a: Performance test results of recycled resin components

[0276]

[0277] b: Results of solvent recovery application tests

[0278]

[0279] c: Results of salt recovery application tests

[0280]

[0281] 5) Economic Benefit Analysis of Resource Recycling

[0282] Taking the treatment of 100 tons of paint-containing waste liquid as an example, this paper compares the resource recovery value of different methods.

[0283]

[0284] Note: Market value is calculated based on the reuse value of recycled materials. Resin content is estimated at 20 yuan / kg, organic solvent at 10 yuan / kg, and inorganic salt at 0.5 yuan / kg.

[0285] 3.4 Results Analysis

[0286] Lacquer component recovery efficiency: The average recovery rate of lacquer components using the method of this invention reaches 75.5%, which is 33.7 percentage points higher than that of traditional extraction methods. This is mainly due to the efficient capture of lacquer components by the osmotic pressure-regulated bioflocculation system and the selective inclusion of lacquer components by γ-cyclodextrin, which significantly improves the collection efficiency of lacquer components.

[0287] Solvent recovery quality: The solvent recovered by the method of this invention has an average purity of 95.5%, which is 12.8 percentage points higher than that of traditional methods. This is because the ozone microbubble oxidation process of this method can selectively degrade pollutants without damaging the solvent structure, while the osmotic pressure control system can effectively reduce interference from non-target substances.

[0288] Innovative Salt Recovery: Traditional methods typically do not consider salt recovery, but this method achieves a salt recovery rate of up to 87.0% with a salt purity of 91.8%, which can be directly used for industrial applications, creating additional economic value.

[0289] The applicability of recycled resources:

[0290] The recycled resin components retain an average performance rate of 86.3%, making it suitable as an additive in new coatings or a main component in low-end coatings.

[0291] The recovered solvent has high purity and can be directly reused in the production process without additional purification;

[0292] The recovered salt can be used as industrial salt, achieving complete resource utilization of waste.

[0293] Economic Benefit Analysis: For the treatment of 100 tons of paint-containing waste liquid, the economic value created by the resource recovery method of this invention is 10,045 yuan higher than that of the traditional method, with a value-added rate of 85.4%. Among them, the added value brought by resin component recovery is the largest, while salt recovery is a value point completely ignored by the traditional method.

[0294] The experimental results show that the method of the present invention has comprehensive advantages in resource recycling. It not only has a high recovery rate and high purity of recycled materials, but also can achieve salt recovery that is difficult to achieve with traditional methods. Ultimately, it forms a green treatment model of "reducing pollutants and maximizing resource recycling", creating significant economic and environmental benefits.

[0295] 4. Environmental friendliness experiment

[0296] 4.1 Experimental Objective

[0297] The environmental friendliness of the method of the present invention is evaluated, including the biotoxicity of the treated waste liquid, secondary pollution, and the biodegradability of the materials used in the process.

[0298] 4.2 Experimental Methods

[0299] Biotoxicity assessment:

[0300] The biotoxicity of wastewater at different treatment stages was determined using the luminescent bacteria inhibition method (GB / T 15441-1995).

[0301] The ecotoxicity of the treated wastewater was assessed using the zebrafish embryo toxicity test (OECD 236).

[0302] Each waste liquid sample was tested three times, and the average inhibition rate and standard deviation were calculated.

[0303] Secondary pollution monitoring:

[0304] Gas emission monitoring: Gas composition generated during the treatment process is analyzed using gas chromatography-mass spectrometry (GC-MS).

[0305] Solid waste assessment: The characteristics of the generated solid waste were analyzed using leaching toxicity testing (HJ / T 300-2007);

[0306] Noise pollution measurement: Noise levels were measured at 1m, 5m, and 10m from the treatment equipment using a sound level meter.

[0307] Material degradability testing:

[0308] The biodegradability of the main chemicals and materials used in this process was evaluated using activated sludge degradation experiments.

[0309] The degradation effect was evaluated by changes in COD removal rate and BOD / COD ratio.

[0310] The final biodegradation rate of the materials used was determined using the OECD 301B method (carbon dioxide release test).

[0311] Compared with traditional methods:

[0312] Compare the differences in environmental friendliness indicators between the method of this invention and traditional chemical and physical-biochemical methods;

[0313] Calculate the comprehensive Environmental Friendly Index (EFI) for each method.

[0314] 4.3 Experimental Results

[0315] 1) Effect of reducing the biotoxicity of waste liquid

[0316]

[0317] 2) Comparison of biotoxicity of different treatment methods

[0318]

[0319] 3) Comparison of secondary pollution generation

[0320]

[0321] 4) Biodegradability of materials used in the process

[0322]

[0323] *Note: Ozone catalysts are inorganic substances and are not suitable for biodegradation tests, but they can be recycled and reused through physical methods.

[0324] 5) Comprehensive evaluation of environmental friendliness

[0325] Based on multiple environmental indicators (biotoxicity reduction rate, secondary pollution generation, material biodegradability, etc.), the comprehensive environmental friendliness index (EFI) of each treatment method was calculated:

[0326]

[0327] Figure 2 The trends in biotoxicity during the treatment process were shown;

[0328] Figure 3 The biodegradability of the materials used in the process is demonstrated.

[0329] 4.4 Results Analysis

[0330] Biotoxicity reduction effect: After treatment by the method of this invention, the inhibition rate of luminescent bacteria in the wastewater decreased from 92.5% to 4.2%, a reduction of 88.3%; the teratogenicity rate of zebrafish embryos decreased from 85.0% to 5.2%, a reduction of 79.8%. This result is far superior to traditional chemical treatment methods (toxicity reduction rate of 69.1%) and traditional physical-biochemical methods (toxicity reduction rate of 82.9%). The significant reduction in biotoxicity is mainly attributed to the synergistic effect of the three technical steps, especially the effective decomposition of toxic organic matter by ozone oxidation and the efficient removal of residual toxic substances by bioflocculation.

[0331] Secondary pollution control: Compared with traditional methods, the method of this invention shows significant advantages in indicators such as waste gas generation, VOCs content in waste gas, and solid waste generation, with reductions of 33.3-82.2%, 48.2-85.2%, and 58.4-72.2%, respectively. This is mainly due to:

[0332] The highly efficient oxidation and degradation of ozone microbubble technology reduces the release of volatile organic compounds;

[0333] The high selectivity of bioflocculants reduces the amount of solid waste generated;

[0334] The optimized design of the overall process has reduced energy consumption and noise levels.

[0335] Biodegradability of Materials: The main materials used in the method of this invention all exhibit good biodegradability, with a 28-day biodegradation rate between 85.4% and 98.2% and a half-life between 5.5 and 15.8 days, all meeting the OECD standards for readily biodegradable substances. Among them, the bioflocculant showed the best degradation performance (degradation rate of 98.2%), which ensures the long-term environmental safety of process residues.

[0336] Comprehensive Environmental Friendliness Evaluation: Through comprehensive evaluation of multiple environmental indicators, the Environmental Friendliness Index (EFI) of the method of this invention reached 9.28 (out of 10), significantly higher than that of traditional chemical treatment methods (6.18) and traditional physical and biochemical methods (7.78). Among the individual indicators, this method performs best in terms of reducing biotoxicity, material degradability, and resource recycling.

[0337] Process safety assessment: Toxicity change curves at each stage of treatment show that toxicity is significantly reduced mainly during ozone oxidation and bioflocculation, demonstrating the rationality of the process design and the effectiveness of the treatment mechanism. Furthermore, the low toxicity of the final treated wastewater ensures its safe discharge, meeting or even exceeding relevant national emission standards.

[0338] The experimental results above demonstrate that the method of this invention not only has advantages in processing efficiency and resource recovery, but also significantly outperforms traditional methods in terms of environmental friendliness. Its characteristics of low secondary pollution, low biotoxicity, and high material biodegradability make it a truly green treatment process, consistent with the concepts of circular economy and sustainable development.

[0339] 5. Scalability Experiment

[0340] 5.1 Experimental Objective

[0341] The adaptability and scalability of the method of the present invention under different industries, different treatment scales, and different waste liquid characteristics were verified.

[0342] Example 1: Treatment of high-salinity paint-containing wastewater generated from ship painting and maintenance.

[0343] A ship repair shop generates a large amount of high-salinity paint-containing wastewater during painting and repair processes. The main characteristics of this wastewater are: salinity 38000 mg / L, COD 15000 mg / L, pH 7.2, and it contains epoxy resin paint components, organic solvents, heavy metal ions, etc. The treatment method of this invention comprises the following specific steps:

[0344] Step 1: Modification of salt-tolerant surfactant system

[0345] Reagent preparation:

[0346] A surfactant composite system containing 3.5% sodium dodecyl sulfonate and 1.5% polyoxyethylene ether was prepared, and 0.8% calcium chloride was added as a synergist.

[0347] Add 1.0% β-cyclodextrin to the above solution and mix thoroughly to obtain a surface-active system.

[0348] Processing procedure:

[0349] 300L of paint-containing waste liquid was placed in a 500L reactor, and the temperature was controlled at 25±2℃.

[0350] Add 15L of the prepared surfactant system to make its concentration in the waste liquid 5%.

[0351] Use a mechanical stirrer to stir at 200 rpm for 30 minutes to ensure that the surfactant and waste liquid are fully mixed.

[0352] Let it stand for 60 minutes to allow the surfactant to fully interact with the organic components in the paint waste liquid.

[0353] Effect detection:

[0354] Samples were taken from the top, middle and bottom of the reactor, 100 mL each, mixed thoroughly and then measured.

[0355] The surface tension decreased from 65 mN / m in the original waste liquid to 32 mN / m.

[0356] The dispersion of organic matter was improved, and the particle size decreased from an average of 2.8 μm to 0.8 μm.

[0357] The transparency of the waste liquid increased by 30%, and the turbidity decreased by 45%.

[0358] Step 2: Salinity-Adaptive Ozone Microbubble Oxidation

[0359] Equipment preparation:

[0360] A ceramic porous membrane microbubble generator was used (average bubble diameter: 50 μm).

[0361] Ozone generator parameter settings: concentration 80mg / L, flow rate 2L / min.

[0362] Prepare 5 L of a catalytic solution containing 0.5% ferrous sulfate.

[0363] Oxidation treatment:

[0364] A catalytic solution was added to the waste liquid modified with surfactant to achieve an iron ion concentration of 200 mg / L.

[0365] Ozone microbubbles are introduced, and the reaction temperature is controlled at 30±2℃.

[0366] The oxidation reaction lasted for 120 minutes, during which the COD value was measured every 30 minutes.

[0367] The oxidation reaction is stopped when the COD reduction rate reaches 70% or more.

[0368] Effect detection:

[0369] COD decreased from 15000 mg / L to 4200 mg / L, a reduction rate of 72%.

[0370] The organic solvent content is reduced by 85%, and the decomposition rate of the main solvent components is >90%.

[0371] The color of the waste liquid changed from dark brown to light yellow, and the transparency increased by 65%.

[0372] The biological toxicity of the waste liquid was reduced by 75%, and the BOD / COD ratio increased from 0.15 to 0.48.

[0373] Step 3: Osmotic Pressure Regulation for Bioflocculation and Selective Extraction

[0374] Preparation of osmotic pressure regulation system:

[0375] Prepare 20 L of an osmotic pressure regulating solution containing 2.0% polyethylene glycol (molecular weight 4000), 0.5% γ-cyclodextrin and 3.0% sodium chloride.

[0376] Prepare 15 L of a bioflocculant suspension containing immobilized Trichoderma brasiliensis and Pseudomonas aeruginosa (mass ratio 3:2) with a bacterial concentration of 5 g / L.

[0377] Flocculation treatment:

[0378] The oxidized waste liquid was cooled to 25°C and then transferred to a 400L flocculation reactor.

[0379] First, add the osmotic pressure regulating solution and stir slowly (60 rpm) for 15 minutes.

[0380] Then add the bio-flocculating agent suspension, stir at 100 rpm for 10 minutes, and then stir slowly at 40 rpm for 50 minutes.

[0381] After standing for 2 hours to settle, the supernatant was separated from the precipitate.

[0382] Selective extraction:

[0383] The resin components were extracted by adding an ester solvent (ethyl acetate) to the flocculated precipitate, with a solvent-to-precipitate ratio of 2:1 (volume ratio).

[0384] Extraction was carried out at 30°C for 45 minutes with a stirring speed of 150 rpm.

[0385] The extract is filtered and distilled to recover the solvent and resin components.

[0386] Effect detection:

[0387] The COD of the supernatant was further reduced to 1150 mg / L, with a total reduction rate of 92.3%.

[0388] The recovered resin has a purity of 88% and a recovery rate of 75%, and can be used as a coating additive.

[0389] The recovered solvent has a purity of >95% and can be directly reused in production.

[0390] The salt concentration in the treated wastewater remains essentially unchanged, allowing for further separation and recovery or discharge in compliance with standards.

[0391] Example 2: Treatment of paint-containing wastewater from a paint manufacturing company

[0392] A paint manufacturer generates paint-containing wastewater during the production of water-based acrylic paint. The wastewater is characterized by a COD of 18500 mg / L, a salinity of 12000 mg / L, and a pH of 6.8, and contains acrylic resin, pigments, dispersants, and other components. The method of this invention is used to treat the wastewater, and the specific steps are as follows:

[0393] Step 1: Modification of salt-tolerant surfactant system

[0394] Reagent preparation:

[0395] A surfactant complex system containing 2.8% sodium lauryl sulfate and 2.0% polyvinylpyrrolidone was prepared, with 0.6% magnesium chloride added as a synergist.

[0396] Add 1.2% α-cyclodextrin to the above solution and mix thoroughly to obtain a surface-active system.

[0397] Processing procedure:

[0398] 200L of paint-containing waste liquid was placed in a 300L reactor, and the temperature was controlled at 23±2℃.

[0399] Add 10L of the prepared surfactant system to make its concentration in the waste liquid 5%.

[0400] Use a mechanical mixer to stir at 180 rpm for 25 minutes.

[0401] Let it stand for 45 minutes to allow the surfactant to fully interact with the organic components in the paint waste liquid.

[0402] Effect detection:

[0403] The surface tension decreased from 58 mN / m in the original waste liquid to 30 mN / m.

[0404] The dispersion of organic matter was improved, and the average particle size decreased from 2.5 μm to 0.65 μm.

[0405] The transparency of the waste liquid increased by 35%, and the turbidity decreased by 50%.

[0406] Step 2: Salinity-Adaptive Ozone Microbubble Oxidation

[0407] Equipment preparation:

[0408] A titanium alloy microporous plate microbubble generator was used (average bubble diameter: 45μm).

[0409] Ozone generator parameter settings: concentration 70mg / L, flow rate 1.8L / min.

[0410] Prepare 4 L of a composite catalytic solution containing 0.4% ferrous sulfate and 0.1% hydrogen peroxide.

[0411] Oxidation treatment:

[0412] A composite catalytic solution was added to the waste liquid modified with surfactants.

[0413] Ozone microbubbles were introduced, and the reaction temperature was controlled at 28±2℃.

[0414] The oxidation reaction lasted for 90 minutes, during which the COD value was measured every 30 minutes.

[0415] The oxidation reaction is stopped when the COD reduction rate reaches 65% or more.

[0416] Effect detection:

[0417] COD decreased from 18500 mg / L to 6100 mg / L, a reduction rate of 67%.

[0418] The organic solvent content is reduced by 80%, and the decomposition rate of the main solvent components is >85%.

[0419] The color of the waste liquid changed from dark blue to light blue, and the transparency increased by 60%.

[0420] The biological toxicity of the waste liquid was reduced by 70%, and the BOD / COD ratio increased from 0.18 to 0.52.

[0421] Step 3: Osmotic Pressure Regulation for Bioflocculation and Selective Extraction

[0422] Preparation of osmotic pressure regulation system:

[0423] Prepare 15 L of an osmotic pressure regulating solution containing 1.8% polyethylene glycol (molecular weight 6000), 0.6% γ-cyclodextrin and 2.5% sodium chloride.

[0424] Prepare 10 L of a bioflocculant suspension containing immobilized white-rot fungi and Bacillus (mass ratio 2:3) with a bacterial concentration of 4.5 g / L.

[0425] Flocculation treatment:

[0426] The oxidized waste liquid was cooled to 23°C and then transferred to a 250L flocculation reactor.

[0427] First, add the osmotic pressure regulating solution and stir slowly (55 rpm) for 12 minutes.

[0428] Then add the bio-flocculator suspension, stir at 90 rpm for 8 minutes, and then stir slowly at 35 rpm for 40 minutes.

[0429] After standing for 1.5 hours to settle, the supernatant was separated from the precipitate.

[0430] Selective extraction:

[0431] The resin components were extracted by adding a mixed solvent (butyl acetate: isopropanol = 7:3) to the flocculated precipitate, with a solvent-to-precipitate ratio of 1.8:1 (volume ratio).

[0432] Extraction was carried out at 32°C for 40 minutes with a stirring speed of 140 rpm.

[0433] The extract is filtered and distilled to recover the solvent and resin components.

[0434] Effect detection:

[0435] The COD of the supernatant was further reduced to 1350 mg / L, with a total reduction rate of 92.7%.

[0436] The recovered resin has a purity of 85% and a recovery rate of 70%, and can be used as a coating additive.

[0437] The recovered solvent has a purity of >93% and can be directly reused in production.

[0438] The treated wastewater meets the industrial wastewater discharge standards.

[0439] Through comparative analysis of these two embodiments, it can be seen that the method of the present invention has good treatment effect on different types of paint-containing waste liquids and has strong adaptability. It can be adjusted according to the characteristics of the waste liquid and has broad practical value.

[0440] The embodiments of the present invention have been described above. However, the embodiments are not limited to the specific implementation methods described above. The specific implementation methods described above are merely illustrative and not restrictive. Those skilled in the art can make more equivalent embodiments under the guidance of the present embodiments, and all of them are within the protection scope of the present embodiments.

Claims

1. A method for reusing paint-containing solutions, characterized in that, Includes the following steps: Step 1: Pre-treat the high-salinity paint waste liquid to remove large particulate impurities and measure the basic parameters of the waste liquid. Step 2: Add a salt-tolerant surfactant system to the pretreated waste liquid and stir and mix it at a temperature of 20-40℃ and a pH of 6-8 to ensure that the surfactant system is in full contact with the waste liquid and to complete the surface property modification. Step 3: Place the waste liquid treated by the surface-active system into a reaction vessel, and introduce ozone microbubbles using a salinity-adaptive ozone generator and a microporous diffusion device. Carry out the oxidation reaction at a temperature of 20-35℃ until the COD reduction rate of the waste liquid reaches the preset value. Step 4: Add an osmotic pressure control system and a biological flocculant to the oxidized waste liquid for flocculation treatment, so that the organic matter forms flocs, and let it stand to allow the flocs to mature. Step 5: Selectively extract the layer or floc containing high concentrations of paint components to recover the paint components and solvents. The treated wastewater meets the discharge standards.

2. The method for reusing a paint-containing solution according to claim 1, characterized in that, The salt-resistant surfactant system includes a main surfactant, an auxiliary surfactant, an ion-shielding agent, and an interface stabilizer, and the amount added is 0.1-1% of the waste liquid volume.

3. The method for reusing a paint-containing solution according to claim 2, characterized in that, The main surfactant is selected from sodium dodecyl sulfate or sodium lauryl sulfate, the auxiliary surfactant is selected from polyoxyethylene ether or polyvinylpyrrolidone, the ion shielding agent is selected from calcium chloride or magnesium chloride, and the interface stabilizer is selected from α-cyclodextrin or β-cyclodextrin.

4. The method for reusing a paint-containing solution according to claim 1, characterized in that, In step two, the stirring speed is 100-200 rpm and the stirring time is 30-60 minutes. After stirring, let it stand for 10-20 minutes.

5. A method for reusing a paint-containing solution according to claim 1, characterized in that, The salinity-adaptive ozone generator has a voltage range of 80-120V and a current range of 1.5-3.0A, and the microporous diffusion device has a pore size of 10-50μm.

6. A method for reusing a paint-containing solution according to claim 1, characterized in that, In step three, the ozone gas flow rate is 0.5-2.0 L / min, the reaction time is 30-90 minutes, and the oxidation reaction is stopped when the COD reduction rate reaches 40-60%.

7. A method for reusing a paint-containing solution according to claim 1, characterized in that, Step three also includes a sub-step of adding a catalyst to assist oxidation. The catalyst is hydrogen peroxide or a metal ion catalyst, wherein the amount of hydrogen peroxide added is 0.1-0.5% of the waste liquid volume, and the concentration of the metal ion catalyst is 5-20 mg / L.

8. A method for reusing a paint-containing solution according to claim 1, characterized in that, The osmotic pressure control system consists of polyethylene glycol, γ-cyclodextrin and sodium chloride in a mass ratio of 1:2:3, and its addition amount is 2-8% of the waste liquid volume.

9. A method for reusing a paint-containing solution according to claim 1, characterized in that, The bio-flocculator is selected from chitosan derivatives or modified alginate, and its addition amount is 0.5-1.5% of the waste liquid volume.

10. A method for reusing a paint-containing solution according to claim 1, characterized in that, In step five, selective extraction uses a mixture of ethyl acetate or butyl acetate and isopropanol as the extractant, with a volume ratio of extractant to the layer to be extracted of 1:2-2:1, an extraction temperature of 25-35℃, and an extraction time of 20-45 minutes.

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