A solid phase-air floatation coupled treatment method for efficiently removing organic matters

Abstract

The application relates to the field of water treatment, and particularly discloses a treatment method for efficiently removing organic matters through solid-gas floating coupling, which comprises the following steps: S1, adding sodium chloride and a surfactant into wastewater to be treated, and then adding a solid floating agent; S2, introducing gas into the wastewater to be treated to perform gas floating treatment, and separating floating dregs above the wastewater through a filter screen to remove organic matters in the wastewater; wherein the solid floating agent in step S1 is obtained after a worm graphite carrier is treated in a mixed solvent of an organic amine, a diluent and a solubilizer. The application can realize efficient removal of multi-component high-concentration organic pollutants under strong acidic conditions.

Description

Technical Field

[0001] This application relates to the field of water treatment, and more specifically, to a solid-phase-air flotation coupled method for the efficient removal of organic matter. Background Technology

[0002] In industries such as chemical and pharmaceutical manufacturing, the high concentration of organic wastewater generated during production has become a major challenge for environmental governance. This type of organic wastewater typically exhibits strong acidity (pH ≤ 1.5), multi-component complex toxicity, and extremely high chemical oxygen demand (COD > 20000 mg / L), posing significant technical difficulties to traditional wastewater treatment technologies. Specifically, this wastewater uses strong acids such as hydrochloric acid and phosphoric acid as media and contains substances including hydrophobic benzenes, polar formic acid, basic dimethylamine, and highly toxic acrylonitrile (LC50 in fish). 50 It contains a variety of toxic and harmful pollutants, including acrolein (9 mg / L) and heterocyclic pyridine.

[0003] Therefore, existing water treatment methods for the above-mentioned types of organic wastewater have shortcomings. When using biochemical treatment, the cell structure of microorganisms is severely damaged in a highly acidic environment. Simultaneously, highly toxic substances such as acrylonitrile have a strong inhibitory effect on microorganisms, leading to the collapse of the biochemical treatment system and making it impossible to effectively remove organic pollutants from the wastewater. For advanced oxidation methods such as Fenton oxidation, chlorine free radicals are easily generated in chlorine-containing media, triggering a chain of chlorination side reactions that produce dioxins with toxicity equivalents increased by 10-100 times, causing serious secondary pollution.

[0004] When using solvent extraction to treat strongly acidic wastewater, amine extractants are prone to irreversible protonation, generating insoluble ion-pair compounds that result in the loss of organic phase partitioning. Furthermore, competition among multiple components leads to low extraction efficiency, and the reliance on energy-intensive distillation equipment hinders industrial application. Current literature describes the use of air flotation technology, which separates pollutants by capturing them with microbubbles. However, under strongly acidic conditions, the main functional components, anionic / cationic surfactants, are prone to protonation and precipitation, causing the gas-liquid interfacial tension regulation system to fail and severely impacting pollutant removal efficiency.

[0005] Given the limitations and difficulties of current water treatment methods in removing organic pollutants in strongly acidic environments, how to achieve efficient removal of multi-component, high-concentration organic pollutants under strongly acidic conditions has broad application prospects and significant environmental value in the field of water treatment. Summary of the Invention

[0006] In order to achieve efficient removal of multi-component high-concentration organic pollutants under strongly acidic conditions, this application provides a solid-phase-air flotation coupled method for efficient removal of organic matter.

[0007] This application provides a solid-phase-air flotation coupled method for efficient removal of organic matter, employing the following technical solution:

[0008] A method for efficiently removing organic matter using a solid-phase-air flotation coupling process includes the following steps:

[0009] S1. Add sodium chloride and surfactant to the wastewater to be treated, and then add solid flotation agent;

[0010] S2. Gas is introduced into the wastewater to be treated for flotation treatment. The scum on the surface of the wastewater is separated by a filter screen to remove organic matter from the wastewater.

[0011] In step S1, the solid flotation agent is obtained by treating worm graphite as a carrier in a mixed solvent of organic amine, diluent and solubilizer.

[0012] By adopting the above technical solution, this application uses worm graphite as a matrix and treats it with a mixed solvent of organic amine, diluent and solubilizer. The ultra-high specific surface area and extreme pH stability of worm graphite are used to construct a physical adsorption substrate. Its unique worm-like multi-level porous structure can form a three-dimensional entanglement space during the adsorption of organic matter, realizing the storage of organic matter. The mixed solvent is embedded into the mesoporous network of worm graphite, which significantly increases the capacity of the entanglement space. Moreover, the protonation of the amino group of its organic amine can enhance its electrostatic attraction with negatively charged organic matter, forming an acid-stable graphite hybrid material with both efficient physical adsorption and selective extraction functions. It is used as a solid flotation agent to realize the adsorption and extraction of organic matter in wastewater.

[0013] The treatment method in this application also incorporates sodium chloride and surfactants. In strongly acidic wastewater, many organic substances and colloidal particles carry charges, forming an electric double layer structure that keeps the colloids stable. After adding sodium chloride, the ion concentration in the solution increases, compressing the electric double layer of the colloidal particles, disrupting the colloidal stability, and causing colloidal ion aggregation. At the same time, the salting-out effect promotes the precipitation of hydrophobic organic substances from the aqueous phase, driving their directional migration, which is beneficial for the adsorption of organic substances with bubbles and solid flotation agents, ensuring the enrichment stability of organic pollutants. Meanwhile, the surfactant forms a stable film on the bubble surface, reducing the surface tension of the bubbles, making the bubbles more stable, and promoting the enrichment of hydrophobic organic substances on the bubble surface, enhancing the bubbles' ability to carry organic pollutants.

[0014] Ultimately, this application involves adding sodium chloride, surfactants, and solid flotation agents to wastewater, combined with air flotation treatment, to generate a large number of microbubbles. Hydrophobic organic matter in the wastewater is directly adsorbed onto the bubble surface, rises with the bubbles to the flotation layer, and dissolves there. Simultaneously, the solid flotation agent adsorbs and extracts organic matter from the wastewater, while the surfactant reduces the gas-liquid interfacial tension, making it easier for hydrophobic organic matter to adsorb onto the bubble surface. As the bubbles rise, the organic-adsorbed bubbles accumulate on the wastewater surface, forming scum. Utilizing the low density of worm graphite and the action of surfactants, the solid flotation agent also floats on the water surface, forming a flotation layer, further adsorbing organic matter. Finally, during the air flotation process, organic matter, under the synergistic effect of bubbles and solid flotation agents, forms a pollutant-rich scum that rises to the liquid surface. The scum is then separated from the wastewater by a filter screen, achieving separation of the flotation adsorption phase and the aqueous phase, thereby removing organic matter from the wastewater. This also solves the current problem of separating the aqueous phase in liquid flotation.

[0015] The method provided in this application utilizes the extreme pH stability of worm graphite and organic amines to overcome the challenge of removing multi-component organic pollutants under strongly acidic conditions, achieving efficient and low-cost wastewater treatment. Simultaneously, the solid flotation agent in this method has regenerative capabilities; it can be desorbed at 80℃ via backwashing with NaOH solution, achieving efficient solvent recovery and low-energy regeneration, further reducing treatment costs and improving the sustainability and economy of the method.

[0016] Optionally, the organic amine is selected from one or more of N235, N503, and N1923, more preferably N235; the diluent is selected from one or more of kerosene, n-hexane, cyclohexane, and toluene, more preferably a combination of kerosene and n-hexane; the solubilizer is selected from one or more of n-octanol, isooctanol, sec-octanol, cyclohexanol, and diethylene glycol monobutyl ether.

[0017] By adopting the above technical solution, tertiary amine organic amines such as N235 (trialkyl tertiary amine) are used as the main extractant. The tertiary amine group in the molecular structure is protonated under acidic conditions to form a positively charged cation, which can combine with organic substances such as dyes, phenols, and carboxylic acids in wastewater through electrostatic attraction or coordination bonds to form hydrophobic complexes. Meanwhile, n-octanol forms hydrogen bonds with polar organic substances to enhance their solubility in kerosene, which helps the above flotation reagents to capture organic substances. Moreover, it can eliminate the viscous third phase formed during N235 extraction, so that the complexes formed by organic amines are uniformly dispersed in kerosene.

[0018] Kerosene has good solubility for organic amines and organic complexes, forming a stable organic phase. At the same time, the low surface tension of kerosene helps bubbles to exist stably in the organic phase, improving the efficiency of air flotation separation. Moreover, by adjusting its viscosity, kerosene makes the bubbles adhere more firmly to the flotation reagent, which helps to increase the floating speed. During the air flotation process, the negatively charged surface of the microbubbles combines with the positively charged organic amine-organic complexes through electrostatic attraction to form a three-phase complex of bubble-extractant-organic matter, which can quickly float to the water surface.

[0019] Optionally, the organic amine is N235, the diluent is kerosene and n-hexane in a mass ratio of 1:(0.3-0.5), and the solubilizer is octanol.

[0020] By adopting the above technical solution, the viscosity of n-hexane is lower than that of kerosene, which can further reduce the viscosity of the system, making it more conducive to contact with wastewater and loading on worm graphite. Combined with the better compatibility and solubility of organic amines and solubilizers in kerosene, it promotes the stable existence of microbubbles in the organic phase.

[0021] Optionally, the solid flotation agent is prepared by the following method:

[0022] 1) Mix organic amine, diluent and solubilizer, and sonicate for 20-30 minutes to obtain a mixed solvent;

[0023] 2) After drying the worm graphite, immerse it in a mixed solvent and ultrasonically impregnate it for 20-30 minutes. Then, treat it under vacuum conditions of -0.1-(-0.2) MPa and 60±5℃ for 1.5-2.5 hours. Finally, filter to remove the solvent to obtain a solid flotation agent.

[0024] Optionally, in the preparation of the solid flotation agent, the mixing volume ratio of organic amine, diluent and solubilizer in step 1) is (1-4):(2-5):1;

[0025] In step 2), the mass-to-volume ratio of worm graphite to mixed solvent is 20-40 mL / g.

[0026] By adopting the above technical solution, the worm graphite is first vacuum dried to remove the water adsorbed in the pores, and then it is subjected to ultrasonic permeation using a gradient loading of ultrasonic-vacuum regime. The cavitation effect of ultrasonic treatment is used to open the mesoporous channels for permeation. Then, it is impregnated under vacuum negative pressure to drive the mixed solvent to fill the deeper pores of the worm graphite and increase its adsorption capacity.

[0027] Optionally, in step S1, the surfactant is prepared as a surfactant solution of 1-10 wt% and added, and the volume ratio of the surfactant solution to the wastewater to be treated is (0.2-0.5):100.

[0028] Sodium chloride is prepared as a 1-10 wt% sodium chloride solution and added, with a concentration of 20-30 mg / mL in the wastewater to be treated;

[0029] The mass-volume ratio of the solid flotation agent added to the wastewater to be treated is 5-10 mg / mL.

[0030] By adopting the above technical solution, and through the synergistic control of interfacial tension by controlling the amount of surfactant and sodium chloride added, the capture of organic matter is synergistically enhanced.

[0031] Optionally, the surfactant may be an amphoteric surfactant.

[0032] By adopting the above technical solution, when selecting amphoteric surfactants, the self-balancing effect of charge can enhance the extraction of organic matter by acid-stable bifunctional graphite hybrid materials, i.e., solid flotation agents, and reduce gas-liquid interfacial tension, promoting the enrichment of hydrophobic organic matter. Ultimately, this improves the simultaneous removal efficiency of multi-component organic matter, including polar and hydrophobic organic matter, in this application. Moreover, it will not react with alkaline washing solution during the regeneration process, ensuring the cycle stability of the material.

[0033] Optionally, in step S2, the solid flotation agent in the scum is regenerated and recycled after being backwashed with sodium hydroxide and subjected to low-temperature thermal desorption treatment at 80±5℃.

[0034] By adopting the above technical solution, the solid flotation agent in the scum obtained after adsorbing organic matter in this application is treated by sodium hydroxide alkaline washing and backwashing. Through the bonding and dissociation of ion pairs, combined with low-temperature thermal desorption, the solvent molecules are efficiently recovered, and the solid flotation agent is regenerated, achieving efficient recycling, significantly reducing the cost of use, and overcoming the non-renewable defect of flotation solvent.

[0035] Optionally, during the preparation of the solid flotation agent, in step 2), after drying the worm graphite, it is first pretreated and then treated in a mixed solvent. The specific pretreatment operation is as follows:

[0036] The dried worm graphite was first impregnated in a 3-5% hydrogen peroxide solution for 30-40 minutes, then modified and impregnated in a modification solution containing aminosilane coupling agent, PAMAM, 4-mercaptobenzoic acid, terephthalic acid and genipin for 30-40 minutes, and then vacuum dried and treated in a mixed solvent.

[0037] By employing the above technical solution, worm-shaped graphite is first impregnated in hydrogen peroxide solution to introduce oxygen-containing functional groups such as hydroxyl and carboxyl groups onto the surface of the worm-shaped graphite. Then, it undergoes treatment with a modification solution. The addition of an aminosilane coupling agent in the modification solution introduces amino groups by binding to the surface of the worm-shaped graphite through silicon-oxygen bonds. PAMAM, as a dendritic amine molecule with a multi-level branched structure, especially containing multiple tertiary and secondary amine groups, can form stereoadsorption sites to enhance its ability to capture organic matter. Simultaneously, under the action of genipin, its amino groups can interact with organic amines such as N235 in the mixed solvent. The formation of cross-links enhances the adhesion of organic amines to worm graphite, further improving its organic matter capture and adsorption performance, and thus improving the removal effect of organic matter. The addition of 4-mercaptobenzoic acid and terephthalic acid, while the carboxyl and amino groups form chemical bonds, introduces benzene ring groups. Utilizing the π-π interaction between the benzene ring groups and organic matter, the adsorption of organic matter is enhanced. At the same time, its hydrophobicity is also improved, making it easier to adhere to air bubbles and promote air flotation separation. The introduction of carboxylic acid groups can enhance the polar interaction with organic matter, improve the adsorption of target pollutants, and improve the water treatment effect.

[0038] Optionally, the modified liquid is prepared by mixing the following raw materials in parts by weight:

[0039] 3-8 parts aminosilane coupling agent, 8-14 parts PAMAM, 1-3 parts 4-mercaptobenzoic acid, 3-5 parts terephthalic acid, 0.5-1.5 parts genipin, 25-35 parts water and 15-20 parts ethanol.

[0040] By adopting the above technical solution and controlling the addition amount of PAMAM and 4-mercaptobenzoic acid, on the one hand, the chelation of thiol groups in 4-mercaptobenzoic acid with metal ions is prevented from increasing the density of worm graphite and affecting its flotation effect. Therefore, the addition of a small amount of 4-mercaptobenzoic acid in this application will not increase the density of worm graphite and affect its flotation treatment and subsequent separation. Moreover, the introduced thiol groups and carboxyl groups work synergistically to form "hydrophobic-polar" bifunctional adsorption sites, enhancing the adsorption capacity for organic matter. Furthermore, the cross-linking structure formed by thiol groups and amino groups can resist the competitive adsorption of metal ions and also help improve the stability of the above-mentioned modification on worm graphite, allowing for more effective and longer-lasting removal of organic matter. In addition, the dendritic structure of PAMAM and the porous structure of worm graphite in this application work synergistically to form a hierarchical adsorption space, increasing the adsorption sites and diffusion paths of organic molecules. The control of its addition amount prevents the excessive number of secondary amine groups from affecting the organic matter extraction and removal effect, ultimately resulting in better organic matter removal.

[0041] In summary, this application has the following beneficial effects:

[0042] 1. In this application, an organic flotation agent containing organic amines, solubilizers, and diluents is loaded onto highly adsorbent expanded worm graphite to form a composite medium as a solid flotation agent. This medium is added to organic wastewater, where it works synergistically with sodium chloride and surfactants, and gas is introduced. Under the action of the surfactants, the solid flotation agent floats on the water surface to form a flotation layer. Hydrophobic organic matter in the wastewater is adsorbed on the surface of the bubbles and floats to the surface of the aqueous phase with the bubbles, dissolving in the flotation layer. The separation of the flotation adsorbed phase and the aqueous phase is achieved through a filter screen, thereby achieving efficient removal of pollutants.

[0043] 2. The solid flotation agent in this application uses worm graphite as a matrix, which has extreme pH stability combined with the pH stability of organic amines. The resulting solid flotation agent is an acid-stable graphite hybrid material, which has excellent organic matter removal effect for wastewater systems where complex organic matter and strong acid coexist. Moreover, the separation operation is simple and fast, and the operating cost is low.

[0044] 3. The coupling of microbubble capture and surface-modified worm graphite achieves dual removal of hydrophobic and polar organic matter. The process does not require pre-neutralization, is compatible with conventional air flotation equipment, and the medium can be regenerated by alkali washing, which greatly reduces the overall treatment cost. It is suitable for the treatment of high-concentration oily wastewater. Moreover, it overcomes the problem of cumbersome separation of organic and aqueous phases after liquid phase solvent flotation, which increases the cost of wastewater treatment. At the same time, it also solves the problem that the slight solubility of flotation organic solvents in the aqueous phase increases the COD of wastewater. Detailed Implementation

[0045] The following detailed description of this application is provided in conjunction with the embodiments. It should be noted that: unless otherwise specified, the conditions in the following embodiments are performed under conventional conditions or conditions recommended by the manufacturer. Unless otherwise specified, the raw materials used in the following embodiments are all from commercially available sources.

[0046] The specific surface area of ​​the worm graphite in this application is ≥50m². 2 / g, expansion volume 200-300mL / g; the density of worm graphite in the following preparation examples is 0.7g / cm³. 3 .

[0047] The following preparation examples are examples of solid flotation agents.

[0048] Preparation Example 1

[0049] A method for preparing a solid flotation agent includes the following steps:

[0050] 1) Mix organic amine N235, diluent kerosene and solubilizer n-octanol in a volume ratio of 1:2:1, and sonicate at a frequency of 40kHz for 25 minutes to obtain a mixed solvent.

[0051] 2) After drying the worm graphite at 105℃ for 4 hours, it was immersed in a mixed solvent and ultrasonically impregnated at a frequency of 40kHz for 25 minutes. Then, it was treated at -0.1MPa and 60℃ for 2 hours. After removing the solvent by filtration, it was dried to obtain a solid flotation agent.

[0052] In step 2), the mass-to-volume ratio of worm graphite to mixed solvent is 30 mL / g, which means that 1 g of worm graphite is immersed in 30 ml of mixed solvent.

[0053] Preparation Example 2

[0054] A method for preparing a solid flotation agent includes the following steps:

[0055] 1) Mix organic amine N235, diluent kerosene and solubilizer n-octanol in a volume ratio of 2:3:1, and sonicate at a frequency of 40kHz for 20min to obtain a mixed solvent.

[0056] 2) After drying the worm graphite at 103℃ for 4 hours, it was immersed in a mixed solvent and ultrasonically impregnated at a frequency of 40kHz for 20 minutes. Then, it was treated under vacuum of -0.1MPa and 55℃ for 2.5 hours. After removing the solvent by filtration, it was dried to obtain a solid flotation agent.

[0057] In step 2), the mass-to-volume ratio of worm graphite to mixed solvent is 20 mL / g, which means 1 g of worm graphite is immersed in 20 ml of mixed solvent.

[0058] Preparation Example 3

[0059] A method for preparing a solid flotation agent includes the following steps:

[0060] 1) Mix organic amine N235, diluent kerosene and solubilizer n-octanol in a volume ratio of 4:5:1, and sonicate at a frequency of 40kHz for 30 minutes to obtain a mixed solvent.

[0061] 2) After drying the worm graphite at 107℃ for 4 hours, it was immersed in a mixed solvent and ultrasonically impregnated at a frequency of 40kHz for 30 minutes. Then, it was treated under vacuum of -0.2MPa and 65℃ for 1.5 hours. After removing the solvent by filtration, it was dried to obtain a solid flotation agent.

[0062] In step 2), the mass-to-volume ratio of worm graphite to mixed solvent is 40 mL / g, which means that 1 g of worm graphite is immersed in 40 ml of mixed solvent.

[0063] Preparation Example 4

[0064] A method for preparing a solid suspension agent is carried out according to the method in Preparation Example 1, except that in step 1), the organic amine N235, the diluent kerosene, and the solubilizer n-octanol are mixed in a volume ratio of 4:5:1.

[0065] Preparation Example 5

[0066] A method for preparing a solid suspension agent is carried out according to the method in Preparation Example 1, except that in step 1), the organic amine N235, the diluent kerosene, and the solubilizer n-octanol are mixed in a volume ratio of 2:2:1.

[0067] Preparation Example 6

[0068] A method for preparing a solid suspension agent is carried out according to the method in Preparation Example 1, except that in step 1), the organic amine N235, the diluent kerosene, and the solubilizer n-octanol are mixed in a volume ratio of 1:5:4.

[0069] Preparation Example 7

[0070] A method for preparing a solid suspension agent is carried out according to the method in Preparation Example 1, except that in step 1), the diluent is kerosene and n-hexane with a mass ratio of 1:0.4.

[0071] Preparation Example 8

[0072] A method for preparing a solid suspension agent is carried out according to the method in Preparation Example 1, except that in step 1), the diluent is kerosene and n-hexane with a mass ratio of 1:0.3.

[0073] Preparation Example 9

[0074] A method for preparing a solid suspension agent is carried out according to the method in Preparation Example 1, except that in step 1), the diluent is kerosene and n-hexane with a mass ratio of 1:0.5.

[0075] Preparation Example 10

[0076] A method for preparing a solid suspending agent is carried out according to the method in Preparation Example 1, except that the organic amine in step 1) is primary amine N-1923.

[0077] Preparation Example 11

[0078] A method for preparing a solid suspending agent is carried out according to the method in Preparation Example 1, except that the specific operation of step 2) is as follows:

[0079] After drying the worm graphite at 105℃ for 4 hours, it was first impregnated in a 4% hydrogen peroxide solution for 35 minutes. The amount of hydrogen peroxide solution added was 7 times the mass of the worm graphite. Then, it was filtered to obtain activated worm graphite.

[0080] Then, a modification solution was prepared by mixing 5 parts of aminosilane coupling agent, 12 parts of PAMAM, 2 parts of 4-mercaptobenzoic acid, 4 parts of terephthalic acid, 1 part of genipin, 30 parts of water and 18 parts of ethanol. The prepared activated worm graphite was modified and impregnated in the modification solution for 35 minutes. The mass ratio of the modification solution to the activated worm graphite was 5:1, the impregnation temperature was 45℃, and the graphite was vacuum dried after impregnation to obtain pretreated worm graphite.

[0081] The pretreated worm graphite was then immersed in a mixed solvent for treatment, using the same method as in Preparation Example 1.

[0082] Preparation Example 12

[0083] A method for preparing a solid suspending agent is carried out according to the method in Preparation Example 1, except that the specific operation of step 2) is as follows:

[0084] After drying the worm graphite at 105℃ for 4 hours, it was first impregnated in a 3% hydrogen peroxide solution for 30 minutes. The amount of hydrogen peroxide solution added was 6 times the mass of the worm graphite. Then, it was filtered to obtain activated worm graphite.

[0085] Then, a modification solution was prepared by mixing 3 parts aminosilane coupling agent, 8 parts PAMAM, 1 part 4-mercaptobenzoic acid, 3 parts terephthalic acid, 0.5 parts genipin, 25 parts water and 15 parts ethanol. The prepared activated worm graphite was modified and impregnated in the modification solution for 30 min. The mass ratio of the modification solution to the activated worm graphite was 4:1, the impregnation temperature was 40℃, and the graphite was vacuum dried after impregnation to obtain pretreated worm graphite.

[0086] The pretreated worm graphite was then immersed in a mixed solvent for treatment, using the same method as in Preparation Example 1.

[0087] Preparation Example 13

[0088] A method for preparing a solid suspending agent is carried out according to the method in Preparation Example 1, except that the specific operation of step 2) is as follows:

[0089] After drying the worm graphite at 105℃ for 4 hours, it was first impregnated in a 5% hydrogen peroxide solution for 40 minutes. The amount of hydrogen peroxide solution added was 8 times the mass of the worm graphite. Then, it was filtered to obtain activated worm graphite.

[0090] Then, 8 parts of aminosilane coupling agent, 14 parts of PAMAM, 3 parts of 4-mercaptobenzoic acid, 5 parts of terephthalic acid, 1.5 parts of genipin, 35 parts of water and 20 parts of ethanol were mixed to prepare a modification solution. The prepared activated worm graphite was modified and impregnated in the modification solution for 40 min. The mass ratio of the modification solution to the activated worm graphite was 6:1, the impregnation temperature was 50℃, and the graphite was vacuum dried after impregnation to obtain pretreated worm graphite.

[0091] The pretreated worm graphite was then immersed in a mixed solvent for treatment, using the same method as in Preparation Example 1.

[0092] Preparation Example 14

[0093] A method for preparing a solid flotation agent is carried out according to the method in Preparation Example 11, except that 4-mercaptobenzoic acid and terephthalic acid are not added to the modified solution.

[0094] Preparation Example 15

[0095] A method for preparing a solid flotation agent is carried out according to the method in Preparation Example 11, except that 4-mercaptobenzoic acid in the modified solution is replaced with terephthalic acid in equal amounts.

[0096] Preparation Example 16

[0097] A method for preparing a solid flotation agent is carried out according to the method in Preparation Example 11, except that PAMAM is not added to the modified solution.

[0098] Example 1

[0099] A method for efficiently removing organic matter using a solid-phase-air flotation coupling process includes the following steps:

[0100] S1. Sodium chloride and an amphoteric surfactant are added to the wastewater to be treated, and then the solid flotation agent prepared in Preparation Example 1 is added. The amphoteric surfactant is specifically dodecyl dimethyl betaine BS-12.

[0101] In step S1, a surfactant solution of 5 wt% is prepared by mixing surfactant with water and added, and the volume ratio of the surfactant solution to the wastewater to be treated is 0.3:100.

[0102] Sodium chloride is mixed with water to prepare a 5 wt% sodium chloride solution, which is then added to the wastewater to be treated at a concentration of 25 mg / mL.

[0103] The mass-volume ratio of the solid flotation agent added to the wastewater to be treated is 8 mg / mL (that is, 8 mg of solid flotation agent is added to 1 ml of wastewater);

[0104] S2. Air is introduced into the wastewater to be treated for flotation treatment for 1 hour. The gas flow rate is 0.4 L / min·L wastewater (i.e., 0.4 liters of gas per minute per liter of wastewater). After the flotation treatment is completed, the scum on the top of the wastewater is separated by a filter screen to remove organic matter from the wastewater. The treated purified water is discharged from the overflow port at the top of the flotation unit.

[0105] Example 2

[0106] A method for efficiently removing organic matter using a solid-phase-air flotation coupling process includes the following steps:

[0107] S1. Sodium chloride and an amphoteric surfactant are added to the wastewater to be treated, and then the solid flotation agent prepared in Preparation Example 2 is added. The amphoteric surfactant is specifically dodecyl dimethyl betaine BS-12.

[0108] In step S1, a surfactant solution of 1 wt% is prepared by mixing surfactant with water and added, and the volume ratio of the surfactant solution to the wastewater to be treated is 0.5:100.

[0109] Sodium chloride is mixed with water to prepare a 1 wt% sodium chloride solution, and the concentration of sodium chloride added to the wastewater to be treated is 30 mg / mL.

[0110] The mass-volume ratio of the solid flotation agent added to the wastewater to be treated is 5 mg / mL (that is, 5 mg of solid flotation agent is added to 1 ml of wastewater);

[0111] S2. Air is introduced into the wastewater to be treated for flotation treatment for 1 hour. The gas flow rate is 0.3 L / min·L wastewater (i.e., 0.3 liters of gas per minute per liter of wastewater). After the flotation treatment is completed, the scum on the top of the wastewater is separated by a filter screen to remove organic matter from the wastewater. The treated purified water is discharged from the overflow port at the top of the flotation unit.

[0112] Example 3

[0113] A method for efficiently removing organic matter using a solid-phase-air flotation coupling process includes the following steps:

[0114] S1. Sodium chloride and an amphoteric surfactant are added to the wastewater to be treated, and then the solid flotation agent prepared in Preparation Example 3 is added. The amphoteric surfactant is specifically dodecyl dimethyl betaine BS-12.

[0115] In step S1, a surfactant solution of 10 wt% is prepared by mixing surfactant with water and added, and the volume ratio of the surfactant solution to the wastewater to be treated is 0.2:100.

[0116] Sodium chloride is mixed with water to prepare a 10 wt% sodium chloride solution, which is then added to the wastewater to be treated at a concentration of 20 mg / mL.

[0117] The mass-volume ratio of the solid flotation agent added to the wastewater to be treated is 10 mg / mL (that is, 10 mg of solid flotation agent is added to 1 ml of wastewater);

[0118] S2. Air gas is introduced into the wastewater to be treated for flotation treatment for 1 hour. The gas flow rate is 0.5 L / min·L wastewater (i.e., 0.5 liters of gas per minute per liter of wastewater). After the flotation treatment is completed, the scum on the top of the wastewater is separated by a filter screen to remove organic matter from the wastewater. The treated purified water is discharged from the overflow port at the top of the flotation unit.

[0119] Example 4-16

[0120] A solid-phase-air flotation coupled method for efficient removal of organic matter is provided, which is carried out according to the method in Example 1, except that the solid flotation agent added in step S1 is selected from the solid flotation agents prepared in Examples 4-16.

[0121] Comparative Example 1

[0122] A solid-phase-air flotation coupled method for efficient removal of organic matter is provided, which is carried out according to the method in Example 1, except that sodium chloride is not added in step S1.

[0123] Comparative Example 2

[0124] A solid-phase-air flotation coupled method for efficient removal of organic matter is provided, which is carried out according to the method in Example 1, except that no amphoteric surfactant is added in step S1.

[0125] Comparative Example 3

[0126] A solid-phase-air flotation coupled method for efficient removal of organic matter is carried out according to the method in Example 1, except that the solid flotation agent in step S1 is replaced by an equal amount of mixed solvent, and the mixed solvent is obtained by mixing tertiary amine N235, kerosene and n-octanol in a volume ratio of 2:3:1.

[0127] Comparative Example 4

[0128] A solid-phase-air flotation coupled method for efficient removal of organic matter is carried out according to the method in Example 1, except that the solid flotation agent in step S1 is replaced by an equal amount of a mixture of worm graphite and a mixed solvent. The mixed solvent is obtained by mixing tertiary amine N235, kerosene and n-octanol in a volume ratio of 2:3:1, and the mass ratio of worm graphite to the mixed solvent is 1:25.

[0129] Comparative Example 5

[0130] A solid-phase-air flotation coupled method for efficient removal of organic matter is provided, which is carried out according to the method in Example 1, except that the solid flotation agent in step S1 is replaced by an equal amount of worm graphite.

[0131] Performance testing

[0132] The ultra-high concentration wastewater with a pH of 1.5 and a COD content of 153820 mg / L was treated according to the methods in the above examples and comparative examples. The COD removal rate after 1 hour of air flotation treatment was statistically analyzed, and the results are shown in Table 1 below.

[0133] Table 1:

[0134]

[0135] Based on the test results in Table 1 above, the solid flotation agent formed by worm graphite loaded with organic amines such as tertiary amine N235 and a mixed solvent of kerosene and octanol in this application embodiment has excellent treatment stability for strongly acidic wastewater with a pH of 0-2 and high concentration of wastewater. When forming an acid-stable hybrid material, it has a stable and excellent treatment effect for removing organic matter.

[0136] Combining the test results of Examples 1 and 4-6, it can be seen that the proportion of N235 added in the mixed solvent has a significant impact on its removal effect. In Example 6, the effect is weakest when the proportion of N235 is too small. In Example 1, the removal effect is better when the mass ratio of N235:octanol:kerosene is 1:1:2. Furthermore, combining the test results of Examples 7-9, the use of a mixture of kerosene and n-hexane as a diluent improves the final organic matter removal effect compared to kerosene alone. Combining the test results of Example 10, tertiary amines are used for water treatment removal, which is more effective than primary amines. Combining the test results of Examples 11-13, the pretreatment of worm graphite before the preparation of the mixed solvent not only helps introduce active functional groups to improve the adsorption of organic matter but also improves the binding strength between the mixed solvent and worm graphite, further enhancing the organic matter removal effect, ultimately leading to a further improvement in the organic matter removal efficiency. Combining the test results of Examples 11, 14, and 15, the removal of organic matter was reduced when no benzene-containing substances or mercaptobenzoic acid were added to the modified solution. Combining the test results of Example 16, the removal of organic matter was significantly reduced when PAMAM was not added to the modified solution.

[0137] Combining the test results of Example 1 with those of Comparative Examples 1 and 2, the removal efficiency of organic matter was significantly reduced when sodium chloride and surfactant were not added to the wastewater. The combination of sodium chloride, surfactant, and the solid flotation agent in this application improved the removal efficiency of organic matter. Furthermore, considering the test results of Comparative Example 3, when the mixed solvent was directly added as a liquid flotation agent, its removal efficiency of organic matter was reduced. More importantly, in Example 1, the separation of the solid flotation phase from the aqueous phase was simpler and more convenient, while in Comparative Example 3, the separation was inconvenient when using upper overflow for liquid flotation. Combining the methods in Comparative Examples 4 and 5, in Comparative Example 4, worm graphite and the mixed solvent were directly added to the wastewater for treatment without loading. This still resulted in difficulties in subsequent separation of the liquid flotation agent in the wastewater, leading to liquid flotation agent residue in the aqueous phase and a significant reduction in the removal efficiency of organic matter. Finally, considering the test results of Comparative Example 5, the removal efficiency was also significantly reduced when only worm graphite was used for flotation to remove organic matter.

[0138] In addition, the solid flotation agent in the scum of the treatment methods in Examples 1 and 11 was washed with a 5% sodium hydroxide solution, then regenerated after heat treatment at 80°C for 2 hours, and reused. The COD removal rate after 5 repeated regenerations was calculated. The COD removal rate after treatment with the method in Example 1 was 25.6%, and the COD removal rate in Example 11 was 44.8%. The solid flotation agent in Example 11 had a better removal effect after regeneration.

[0139] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A method for efficiently removing organic matter using a solid-phase-air flotation coupling process, characterized in that, Includes the following steps: S1. Add sodium chloride and surfactant to the wastewater to be treated, and then add solid flotation agent; S2. Gas is introduced into the wastewater to be treated for air flotation treatment. The scum on the surface of the wastewater is separated by a filter screen to remove organic matter from the wastewater. The solid flotation agent in step S1 is prepared by the following method: 1) Mix organic amine, diluent and solubilizer, and ultrasonically treat for 20-30 min to obtain a mixed solvent; 2) After drying worm graphite, immerse it in the mixed solvent, ultrasonically impregnate for 20-30 min, and then treat it under vacuum of -0.1-(-0.2) MPa and 60±5℃ for 1.5-2.5 h. Then filter to remove the solvent to obtain the solid flotation agent. The organic amine is selected from one or more of N235, N503, and N1923; the diluent is selected from one or more of kerosene, n-hexane, cyclohexane, and toluene; and the solubilizer is selected from one or more of n-octanol, isooctanol, sec-octanol, cyclohexanol, and diethylene glycol monobutyl ether. When preparing the solid flotation agent, in step 2), after drying the worm graphite, it is first pretreated and then treated in a mixed solvent. The specific pretreatment operation is as follows: The dried worm graphite is first impregnated in a 3-5% hydrogen peroxide aqueous solution for 30-40 minutes, then modified and impregnated in a modified solution containing aminosilane coupling agent, PAMAM, 4-mercaptobenzoic acid, terephthalic acid and genipin for 30-40 minutes, and then vacuum dried and treated in a mixed solvent.

2. The method for efficient removal of organic matter using a solid-phase-air flotation coupling according to claim 1, characterized in that: The organic amine used is N235, the diluent is kerosene and n-hexane in a mass ratio of 1:(0.3-0.5), and the solubilizer is octanol.

3. The method for efficient removal of organic matter using a solid-phase-air flotation coupling according to claim 1, characterized in that: When preparing the solid flotation agent, the mixing volume ratio of organic amine, diluent and solubilizer in step 1) is (1-4):(2-5):1; the mass-volume ratio of worm graphite to mixed solvent in step 2) is 20-40 mL / g.

4. The method for efficient removal of organic matter using a solid-phase-air flotation coupling according to claim 1, characterized in that: In step S1, the surfactant is prepared as a 1-10 wt% surfactant solution and added, with the volume ratio of the surfactant solution to the wastewater to be treated being (0.2-0.5):100; the sodium chloride is prepared as a 1-10 wt% sodium chloride solution and added, with the concentration of sodium chloride added to the wastewater to be treated being 20-30 mg / mL; the mass-volume ratio of the solid flotation agent added to the wastewater to be treated is 5-10 mg / mL.

5. The method for efficient removal of organic matter using a solid-phase-air flotation coupling according to claim 1, characterized in that: The surfactant selected is an amphoteric surfactant.

6. The method for efficient removal of organic matter using a solid-phase-air flotation coupling according to claim 1, characterized in that: In step S2, the solid flotation agent in the scum is regenerated and recycled after being backwashed with sodium hydroxide and subjected to low-temperature thermal desorption treatment at 80±5℃.

7. The method for efficient removal of organic matter using a solid-phase-air flotation coupling according to claim 1, characterized in that: The modified liquid is prepared by mixing the following raw materials in parts by weight: 3-8 parts aminosilane coupling agent, 8-14 parts PAMAM, 1-3 parts 4-mercaptobenzoic acid, 3-5 parts terephthalic acid, 0.5-1.5 parts genipin, 25-35 parts water and 15-20 parts ethanol.

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