A kind of agent for treating high suspended solids wastewater in oil production plants

Abstract

This application relates to the field of wastewater treatment technology, specifically disclosing a treatment agent for high suspended solids wastewater from oilfields. The agent comprises: 40-60 parts modified bentonite; 5-15 parts ferrous sulfate; 5-15 parts aluminum ferric sulfate; 1-5 parts ethylenediaminetetraacetic acid; 10-20 parts activated biochar material; 3-8 parts chitosan; and 5-10 parts flocculant. The modified bentonite is obtained by modifying bentonite with laccase and nano-zero-valent iron. The activated biochar material is obtained from waste biomass as raw material, after semi-carbonization and activation treatment. This wastewater treatment agent can be used to purify high suspended solids wastewater generated by oilfields and oil wells. It has a high removal efficiency for suspended solids and can effectively remove organic humic substances, thereby ensuring that the suspended solids content of the treated wastewater meets the standards.

Description

Technical Field

[0001] This application relates to the field of wastewater treatment technology, and more specifically, to a reagent for treating high suspended solids wastewater in oilfields. Background Technology

[0002] Wastewater from oilfields is characterized by its complex composition, high suspended solids content, high oil content, and the presence of various chemical substances. Suspended solids are a key pollutant, including rock fragments, clay particles, bacterial cells, corrosion products, and various organic and inorganic impurities. These substances increase the turbidity of the wastewater, affecting the effectiveness of subsequent treatment processes and even causing wear and blockages to equipment. For high-suspended-solids wastewater from oilfields, relying solely on natural sedimentation is too slow to achieve efficient solid-liquid separation, failing to meet the requirements of large-scale wastewater treatment. Currently, high-suspended-solids wastewater from oilfields is mainly treated by adding chemical agents for purification.

[0003] In related technologies, such as the patent document with announcement number CN109574118B, a wastewater treatment composite agent and its preparation method are disclosed. The technical solution adopted is: a wastewater treatment composite agent, which, by mass percentage, includes 85% to 94% bentonite, 0.5% to 2.5% sodium tartrate, 0.5% to 2.5% carboxyethyl thiosuccinic acid, 0.4% to 1.6% chitosan and 4% to 9% stearate; wherein the bentonite is inorganic modified bentonite.

[0004] However, this composite agent still has some shortcomings in its practical application to the treatment of high suspended solids wastewater in oilfields. The suspended solids composition of oilfield wastewater is complex, containing not only inorganic solid impurities but also abundant humic substances generated from the long-term natural decomposition and transformation of plant and animal remains in the strata. These humic substances have complex structures and high molecular weights, mainly composed of humic acid, fulvic acid, and humin, which exist in wastewater in colloidal or dissolved forms. While the bentonite and other components in the aforementioned composite agent exhibit some adsorption and flocculation capabilities for solid impurities, they are ineffective in removing humic substances. If humic substances are not effectively removed from wastewater, they will continue to decompose after being discharged into the natural environment. This process consumes a large amount of dissolved oxygen in the water, potentially leading to oxygen deficiency and causing negative impacts on aquatic ecosystems. Therefore, the current composite agent still has certain deficiencies in the efficient removal of humic substances from oilfield wastewater and requires further research and improvement. Summary of the Invention

[0005] Based on the above, in order to improve the removal effect of the treatment agent on humic substances in wastewater and ensure that the suspended solids content of the treated wastewater meets the standards, this application provides a treatment agent for high suspended solids wastewater in oilfields.

[0006] This application provides a technical solution for a high-suspended-solids wastewater treatment agent in oilfields:

[0007] An agent for treating wastewater with high suspended solids in oilfields is made from the following raw materials in parts by weight:

[0008] 40-60 parts of modified bentonite;

[0009] 5-15 parts of ferrous sulfate;

[0010] 5-15 parts aluminum ferric sulfate;

[0011] 1-5 parts of ethylenediaminetetraacetic acid;

[0012] 10-20 parts of activated biochar material;

[0013] 3-8 parts chitosan;

[0014] 5-10 parts flocculant;

[0015] The modified bentonite was obtained by modifying bentonite with laccase and nano-zero valent iron.

[0016] The activated biochar material is obtained from waste biomass through semi-carbonization and activation treatment.

[0017] The effects are as follows: Modified bentonite is obtained by modifying bentonite with laccase and nano-zero-valent iron. Laccase is a copper-containing polyphenol oxidase with a significant ability to degrade humic substances. Humic substances in oilfield wastewater have a complex structure, and laccase can catalyze the oxidation of phenols, aromatic amines, and other compounds in humic substances, decomposing them into smaller molecules. By degrading humic substances, and then using modified bentonite to adsorb and purify the degraded humic substances, the suspended solids content in oilfield wastewater is effectively reduced. Nano-zero-valent iron has abundant active sites on its surface, which can interact with laccase molecules through chemical bonding and electrostatic adsorption, thus firmly fixing the laccase to its surface. Simultaneously, when nano-zero-valent iron is mixed with bentonite, it can form a bridging effect between bentonite particles, allowing the laccase to be more stably loaded onto the bentonite, thereby improving the stability of the modification. Nano-zero-valent iron possesses strong reducing power. It can partially disrupt the complex structures in humic substances through reduction, thereby lowering the molecular weight and complexity of the humic substances and facilitating further degradation by laccase. Furthermore, the degraded humic products carry a certain electrical charge. The surface charge of nano-zero-valent iron can interact with these products through electrostatic attraction, thus enhancing the adsorption capacity of modified bentonite for the degradation products.

[0018] Ferrous sulfate and ferric aluminum sulfate hydrolyze in wastewater to form ferric hydroxide and aluminum hydroxide colloids. These colloids have strong adsorption and flocculation effects, enabling suspended solids in wastewater to coagulate into larger particles, thus facilitating sedimentation and removal. Ethylenediaminetetraacetic acid (EDTA) can form stable complexes with metal ions in wastewater, reducing the interference of metal ions on other components and also helping to remove some heavy metal ions. Chitosan has good flocculation and adsorption properties, and can combine with suspended solids and colloidal substances in wastewater to form flocs, accelerating the sedimentation process. Flocculants further enhance the flocculation effect of suspended solids in wastewater, increase the sedimentation rate, and ensure that the suspended solids content of the treated wastewater meets the standards. The treatment agent of this application has a highly efficient removal effect on humic substances in oilfield wastewater, and also has good adsorption and flocculation effects on other suspended solids, significantly reducing the suspended solids content and turbidity in wastewater.

[0019] Optionally, the modified bentonite is prepared by the following method:

[0020] A. Prepare an aqueous solution of laccase and an ethanol dispersion of nano-zero valent iron; add bentonite to deionized water, stir for 10-20 min, and then sonicate for 15-30 min to obtain a bentonite suspension;

[0021] B. Place the bentonite suspension in a nitrogen-filled reactor, add the ethanol dispersion of nano-zero valent iron under stirring conditions of 100-200 r / min, and then stir the reaction for 1-2 h. Next, add laccase aqueous solution to the reactor, maintain the reaction temperature at 30-40℃, and react for 2-4 h to obtain the intermediate solution.

[0022] C. Transfer the intermediate solution to a centrifuge tube and centrifuge at 3000-5000 r / min for 10-15 min under nitrogen protection to separate the solid precipitate. Then wash the solid precipitate and dry it under nitrogen atmosphere to obtain modified bentonite.

[0023] By employing the above technical solution, under nitrogen protection, nano-zero-valent iron is first mixed with bentonite, and its active sites bind to the bentonite surface. Subsequently, laccase is added, and the nano-zero-valent iron immobilizes the laccase through chemical bonding and electrostatic adsorption. Simultaneously, its bridging effect between bentonite particles ensures that the laccase is more stably loaded onto the bentonite, guaranteeing effective contact and decomposition of humic substances by the laccase. The nano-zero-valent iron also reduces humic substances, creating more favorable conditions for laccase activity. The modified bentonite prepared by this method not only exhibits good adsorption and flocculation effects on other suspended solids but also demonstrates good removal effects on humic substances in wastewater, thus contributing to the reduction of suspended solids content in oilfield wastewater.

[0024] Optionally, the concentration of the laccase aqueous solution in step A is 10-50 mg / mL; the concentration of the ethanol dispersion of nano-zero valent iron is 5-20 mg / mL; and the mass concentration of the bentonite suspension is 5%-10%.

[0025] By adopting the above technical solution, the laccase aqueous solution of the above concentration ensures that laccase can fully participate in the decomposition reaction of humic substances; when the concentration of the nano-zero valent iron ethanol dispersion is within the concentration range provided above, its active sites can fully interact with laccase and bentonite; the bentonite suspension of a specific mass concentration makes the bentonite particles uniformly dispersed, providing sufficient contact sites for nano-zero valent iron and laccase, thereby enabling the modified bentonite to maintain a good modification effect.

[0026] Optionally, in step B, the mass ratio of bentonite suspension, ethanol dispersion of nano-zero valent iron, and laccase aqueous solution is 10:(0.5-1):(1-2).

[0027] Optionally, the activated biochar material is prepared by the following method:

[0028] Waste biomass is heated at 180-190℃ and with an oxygen volume concentration of 1%-5% for 2-3 hours to obtain semi-carbonized biomass. Then, the semi-carbonized biomass is soaked in potassium hydroxide solution for 12-24 hours. After soaking, the semi-carbonized biomass is dried and then calcined at 450-600℃ for 1-2 hours under anaerobic conditions to obtain activated biochar material.

[0029] By employing the above technical solutions, the activated biochar material prepared by the above methods possesses abundant pore structure and surface activity, enabling it to efficiently adsorb humic substances and other pollutants in wastewater, thereby improving the removal capacity of wastewater treatment agents for complex pollutants. After the waste biomass undergoes semi-carbonization and activation with potassium hydroxide under specific conditions, the potassium carbonate generated from the reaction of potassium hydroxide and carbon volatilizes during calcination, leaving behind abundant pores and increasing the specific surface area. Simultaneously, when the activated biochar material is mixed with modified bentonite and other components, the presence of the activated biochar material provides a stable microenvironment for active ingredients such as laccase, promoting the decomposition of humic substances by laccase.

[0030] Optionally, the mass concentration of the potassium hydroxide solution is 30%-40%, and the mass ratio of the semi-carbonized biomass to the potassium hydroxide solution is 1:(3-4).

[0031] Optionally, the waste biomass can be any one of rice husks, corn stalks, and sugarcane bagasse.

[0032] Optionally, the flocculant is either polyferric chloride or polyacrylamide.

[0033] Optionally, the viscosity of the chitosan is 0.7-1 Pa·s.

[0034] By employing the above technical solution, chitosan within this viscosity range exhibits suitable fluidity and molecular extensibility in solution, allowing its amino and hydroxyl groups on the molecular chain to interact more effectively with pollutants. During flocculation, it can synergistically work with flocculants to improve the removal efficiency of suspended solids and humic substances from wastewater.

[0035] This application also provides a method for preparing a reagent for treating high suspended solids wastewater in oilfields, using the following technical solution:

[0036] A method for preparing a reagent for treating high suspended solids wastewater in oilfields includes the following steps:

[0037] S1. Mix the modified bentonite and activated biochar materials and stir at 100-150 r / min for 5-10 min to obtain a premix.

[0038] S2. Mix ferrous sulfate, aluminum ferric sulfate, ethylenediaminetetraacetic acid, chitosan and flocculant with the premix and continue stirring for 20-30 minutes to obtain the mixture;

[0039] S3. Transfer the mixture to an extrusion granulator for extrusion granulation to obtain granular agent. Dry the granular agent at 60-80℃ for 3-5 hours to obtain an agent for treating high suspended solids wastewater in oilfields.

[0040] By adopting the above technical solution, the method utilizes multiple components synergistically. Ferrous sulfate, aluminum ferric sulfate, and other components, combined with modified bentonite and activated biochar, enhance the flocculation and adsorption capabilities for impurities in wastewater. The modified bentonite, modified with laccase and nano-zero-valent iron, can efficiently degrade and adsorb humic substances in wastewater, effectively reducing suspended solids content and improving wastewater purification efficiency.

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

[0042] 1. This application uses laccase and nano-zero-valent iron to modify bentonite. Laccase can catalyze the oxidation reaction of phenols, aromatic amines and other compounds in humic substances, decomposing them into small molecules. Nano-zero-valent iron can enhance the fixation and reduction of the complex structure of humic substances by laccase. The synergistic effect of the two enhances the effect of modified bentonite on the efficient degradation and adsorption of humic substances in oilfield wastewater, and can effectively reduce the content of suspended solids in wastewater.

[0043] 2. In this application, activated biochar material is preferably prepared by semi-carbonizing waste biomass under specific conditions, soaking it in potassium hydroxide solution of a specific concentration, and calcining it at high temperature. Because this process forms a rich pore structure and a large specific surface area, and can provide a stable microenvironment for active ingredients such as laccase, activated biochar material can efficiently adsorb small molecules and other pollutants after the degradation of humic substances in sewage, and synergistically improve the effect of modified bentonite on the removal capacity of sewage treatment agents for complex pollutants.

[0044] 3. The method of this application involves mixing modified bentonite, activated biochar material, ferrous sulfate, aluminum ferric sulfate, ethylenediaminetetraacetic acid, chitosan, and flocculants in a specific ratio, and using a suitable preparation process. Each component exerts its own adsorption, flocculation, and complexation effects, working synergistically to prepare a treatment agent that has a good removal effect on humic substances and other suspended solids in oilfield wastewater. It can significantly reduce the suspended solids content and turbidity in wastewater, ensuring that wastewater meets discharge standards. Detailed Implementation

[0045] The present application will be further described in detail below with reference to the embodiments.

[0046] Preparation example of modified bentonite

[0047] Preparation Example 1

[0048] Modified bentonite was prepared by the following method:

[0049] A. Prepare an aqueous solution of laccase with a concentration of 10 mg / mL and an ethanol dispersion of nano-zero valent iron with a concentration of 5 mg / mL; add 5 kg of bentonite to 95 kg of deionized water, stir for 10 min, and then sonicate for 15 min to obtain a bentonite suspension with a mass concentration of 5%.

[0050] B. Place 10 kg of bentonite suspension in a nitrogen-filled reactor. Under stirring conditions of 100 r / min, add 0.5 kg of nano-zero valent iron ethanol dispersion and stir for 1 h. Then add 1 kg of laccase aqueous solution to the reactor and maintain the reaction temperature at 30℃. After 2 h of reaction, the intermediate solution is obtained.

[0051] C. Transfer the intermediate solution to a centrifuge tube and centrifuge at 3000 r / min for 10 min under nitrogen protection to separate the solid precipitate. Then wash the solid precipitate and dry it under nitrogen atmosphere to obtain modified bentonite.

[0052] Preparation Example 2

[0053] Modified bentonite was prepared by the following method:

[0054] A. Prepare an aqueous solution of laccase with a concentration of 30 mg / mL and an ethanol dispersion of nano-zero valent iron with a concentration of 12 mg / mL; add 8 kg of bentonite to 92 kg of deionized water, stir for 15 min, and then sonicate for 25 min to obtain a bentonite suspension with a mass concentration of 8%.

[0055] B. Place 10 kg of bentonite suspension in a nitrogen-filled reactor. Under stirring conditions of 150 r / min, add 0.8 kg of nano-zero valent iron ethanol dispersion and stir for 1.5 h. Then add 1.5 kg of laccase aqueous solution to the reactor and maintain the reaction temperature at 35℃. After 3 h, the intermediate solution is obtained.

[0056] C. Transfer the intermediate solution to a centrifuge tube and centrifuge at 4000 r / min for 12 min under nitrogen protection to separate the solid precipitate. Then wash the solid precipitate and dry it under nitrogen atmosphere to obtain modified bentonite.

[0057] Preparation Example 3

[0058] Modified bentonite was prepared by the following method:

[0059] A. Prepare an aqueous solution of laccase with a concentration of 50 mg / mL and an ethanol dispersion of nano-zero valent iron with a concentration of 20 mg / mL; add 10 kg of bentonite to 90 kg of deionized water, stir for 20 min, and then sonicate for 30 min to obtain a bentonite suspension with a mass concentration of 10%.

[0060] B. Place 10 kg of bentonite suspension in a nitrogen-filled reactor. Under stirring conditions of 200 r / min, add 1 kg of nano-zero valent iron ethanol dispersion and stir for 2 h. Then add 2 kg of laccase aqueous solution to the reactor and maintain the reaction temperature at 40℃. After 4 h of reaction, the intermediate solution is obtained.

[0061] C. Transfer the intermediate solution to a centrifuge tube and centrifuge at 5000 r / min for 15 min under nitrogen protection to separate the solid precipitate. Then wash the solid precipitate and dry it under nitrogen atmosphere to obtain modified bentonite.

[0062] Preparation Example 4

[0063] The modified bentonite differs from preparation example 3 in that, in this preparation example, the mass ratio of bentonite suspension, ethanol dispersion of nano-zero valent iron, and laccase aqueous solution in step B is 10:3:3.

[0064] Preparation Example 5

[0065] The modified bentonite differs from Preparation Example 3 in that, in this preparation example, a urease aqueous solution with a concentration of 50 mg / mL is prepared in step A, and an equal amount of urease aqueous solution is used instead of laccase aqueous solution in step B to participate in the reaction.

[0066] Preparation Example 6

[0067] The modified bentonite differs from that in Preparation Example 3 in that, in this preparation example, an ethanol dispersion of nano-zero valent iron is added in step B. Specifically, step B is as follows:

[0068] 10 kg of bentonite suspension was placed in a nitrogen-filled reactor, and then 2 kg of laccase aqueous solution was added to the reactor. The reaction temperature was maintained at 40°C, and the reaction was carried out for 4 hours to obtain an intermediate solution.

[0069] Preparation example of activated biochar materials

[0070] Preparation Example 7

[0071] Activated biochar material is prepared by the following method:

[0072] Rice husks were heated at 180℃ and with an oxygen concentration of 1% for 2 hours to obtain semi-carbonized biomass. The semi-carbonized biomass was then soaked in a 30% potassium hydroxide solution for 12 hours, with a mass ratio of semi-carbonized biomass to potassium hydroxide solution of 1:3. After soaking, the semi-carbonized biomass was dried and then calcined at 450℃ for 1 hour under anaerobic conditions to obtain activated biochar material.

[0073] Preparation Example 8

[0074] Activated biochar material is prepared by the following method:

[0075] Corn stalks were heated at 185℃ and with an oxygen concentration of 3% for 2.5 hours to obtain semi-carbonized biomass. The semi-carbonized biomass was then soaked in a 35% potassium hydroxide solution for 18 hours, with a mass ratio of semi-carbonized biomass to potassium hydroxide solution of 1:3.5. After soaking, the semi-carbonized biomass was dried and then calcined at 550℃ for 1.5 hours under anaerobic conditions to obtain activated biochar material.

[0076] Preparation Example 9

[0077] Activated biochar material is prepared by the following method:

[0078] Corn stalks were heated at 190℃ and with an oxygen concentration of 5% for 3 hours to obtain semi-carbonized biomass. Then, the semi-carbonized biomass was soaked in a 40% potassium hydroxide solution for 24 hours, with a mass ratio of semi-carbonized biomass to potassium hydroxide solution of 1:4. After soaking, the semi-carbonized biomass was dried and then calcined at 600℃ for 2 hours under anaerobic conditions to obtain activated biochar material.

[0079] Preparation Example 10

[0080] The difference between this activated biochar material and Preparation Example 9 is that, in this preparation example, an equal amount of sodium hydroxide solution with a mass fraction of 40% was used to soak the semi-carbonized biomass.

[0081] Example

[0082] Example 1

[0083] A reagent for treating wastewater with high suspended solids in oilfields, the raw material components and dosages of which are shown in Table 1. Specifically, the modified bentonite is the modified bentonite prepared in Preparation Example 1; the activated biochar material is the modified biochar material prepared in Preparation Example 7; the chitosan has a viscosity of 0.7 Pa·s; and the flocculant is polyferric chloride.

[0084] A method for using a reagent for treating wastewater with high suspended solids in oilfields includes the following steps:

[0085] S1. Mix the modified bentonite and activated biochar materials and stir at 100 r / min for 10 min to obtain a premix.

[0086] S2. Mix ferrous sulfate, aluminum ferric sulfate, ethylenediaminetetraacetic acid, chitosan and flocculant with the premix and continue stirring for 20 minutes to obtain the mixture;

[0087] S3. Transfer the mixture to an extrusion granulator for extrusion granulation to obtain granular agent. Dry the granular agent at 60℃ for 5 hours to obtain an agent for treating high suspended solids wastewater in oilfields.

[0088] Example 2

[0089] A reagent for treating wastewater with high suspended solids in oilfields, the raw material components and dosages of which are shown in Table 1. Specifically, the modified bentonite is the modified bentonite prepared in Preparation Example 2; the activated biochar material is the modified biochar material prepared in Preparation Example 8; the chitosan has a viscosity of 0.8 Pa·s; and the flocculant is polyacrylamide.

[0090] A method for using a reagent for treating wastewater with high suspended solids in oilfields includes the following steps:

[0091] S1. Mix the modified bentonite and activated biochar materials and stir at 120 r / min for 8 min to obtain a premix.

[0092] S2. Mix ferrous sulfate, aluminum ferric sulfate, ethylenediaminetetraacetic acid, chitosan and flocculant with the premix and continue stirring for 25 minutes to obtain the mixture;

[0093] S3. Transfer the mixture to an extrusion granulator for extrusion granulation to obtain granular agent. Dry the granular agent at 70℃ for 4 hours to obtain an agent for treating high suspended solids wastewater in oilfields.

[0094] Example 3

[0095] A reagent for treating wastewater with high suspended solids in oilfields, the raw material components and dosages of which are shown in Table 1. Specifically, the modified bentonite is the modified bentonite prepared in Preparation Example 3; the activated biochar material is the modified biochar material prepared in Preparation Example 9; the chitosan has a viscosity of 1.0 Pa·s; and the flocculant is polyacrylamide.

[0096] A method for using a reagent for treating wastewater with high suspended solids in oilfields includes the following steps:

[0097] S1. Mix the modified bentonite and activated biochar materials and stir at 150 r / min for 5 min to obtain a premix.

[0098] S2. Mix ferrous sulfate, aluminum ferric sulfate, ethylenediaminetetraacetic acid, chitosan and flocculant with the premix and continue stirring for 30 minutes to obtain the mixture;

[0099] S3. Transfer the mixture to an extrusion granulator for extrusion granulation to obtain granular agent. Dry the granular agent at 80℃ for 3 hours to obtain an agent for treating high suspended solids wastewater in oilfields.

[0100] Table 1. Raw material components and dosage (kg) of the treatment agents in Examples 1-3

[0101]

[0102] Example 4

[0103] A treatment agent for high suspended solids wastewater in oilfields, which differs from Example 1 in that the modified bentonite in this example is the modified bentonite prepared in Preparation Example 4.

[0104] Example 5

[0105] An agent for treating wastewater with high suspended solids in oilfields is different from Example 1 in that the activated biochar material in this example is the modified biochar material prepared in Preparation Example 10.

[0106] Example 6

[0107] An agent for treating wastewater with high suspended solids in oilfields, which differs from Example 1 in that aluminum sulfate is used as the flocculant in this example.

[0108] Comparative Example

[0109] Comparative Example 1

[0110] A treatment agent for high suspended solids wastewater in oilfields, differing from Example 1 in that an equal amount of unmodified bentonite is used instead of modified bentonite in this comparative example.

[0111] Comparative Example 2

[0112] A treatment agent for high suspended solids wastewater in oilfields is different from Example 1 in that an equal amount of coal-based activated carbon is used instead of biochar material in this comparative example.

[0113] Comparative Example 3

[0114] A treatment agent for high suspended solids wastewater in oilfields, which differs from Example 1 in that the modified bentonite in this comparative example is the modified bentonite prepared in Preparation Example 5.

[0115] Comparative Example 4

[0116] A treatment agent for high suspended solids wastewater in oilfields, which differs from Example 1 in that the modified bentonite in this comparative example is the modified bentonite prepared in Preparation Example 6.

[0117] Performance testing

[0118] In this embodiment, the equipment flushing wastewater generated from the drilling platform area during the drilling process was used as the wastewater sample to be tested. The suspended solids content of the sample is shown in Table 2.

[0119] Table 2. Suspended solids content in wastewater

[0120]

[0121] Detection methods

[0122] 1. Sample collection: After the above-mentioned wastewater samples to be tested are mixed evenly, they are divided into several equal portions, each with a volume of 500mL. The portions are sealed, stored and labeled.

[0123] 2. Addition and reaction of reagents: Take 10 500mL wastewater samples and add the reagents prepared in Examples 1-6 and Comparative Examples 1-4 in sequence, with an addition amount of 25g of reagent. Place the water samples on a magnetic stirrer and stir at 200r / min for 30min to ensure that the reagents and wastewater are fully mixed and reacted.

[0124] 3. After the reaction was completed, the water sample was centrifuged again at 4000 r / min for 15 min, and the supernatant was collected. The turbidity of the treated water sample was measured using a turbidimeter; the absorbance of humic substances in the treated water sample was measured using a spectrophotometer, and the humic substance content was calculated according to the standard curve; the supernatant was filtered through a 0.45 μm filter membrane, and the suspended solids content of the treated water sample was determined by gravimetric method. The results are shown in Table 3.

[0125] Table 3 Detection Results

[0126]

[0127] In Examples 1-3, the suspended solids removal rate of the wastewater was above 98%, with Example 1 achieving the highest rate of 99.08%. This indicates that the specific proportions of modified bentonite, activated biochar, and other compounded agents significantly remove suspended solids from the wastewater used for flushing drilling platform equipment. The laccase and nano-zero-valent iron in the modified bentonite synergistically degrade and adsorb humic substances, while the rich porous structure of the activated biochar adsorbs small molecule pollutants. The colloids produced by the hydrolysis of ferrous sulfate and aluminum ferric sulfate, along with the flocculation effect of the flocculant, collectively promote the coagulation and sedimentation of suspended solids. After wastewater treatment in Examples 1-3, the inorganic solids particle content was 8 mg / L, 10 mg / L, and 13 mg / L, respectively. Modified bentonite and activated biochar have a certain adsorption effect on inorganic solids particles, while the flocculant causes the inorganic particles to coagulate and settle, resulting in a synergistic reduction in the inorganic solids particle content. After wastewater treatment in Examples 1-3, the organic humic substance content was reduced to a low level, at 3 mg / L, 5 mg / L, and 4 mg / L, respectively. This is due to the oxidative decomposition of phenolic and aromatic amine compounds in humic substances by laccase, the enhancement of laccase activity by nano-zero valent iron and the reduction of the complex structure of humic substances, making them easier to decompose and adsorb, and the further adsorption of small molecules after the degradation of humic substances by activated biochar materials, thereby effectively reducing the content of organic humic substances in wastewater.

[0128] In Example 4, the suspended solids removal rate of the wastewater decreased to 96.58%, a decrease compared to Examples 1-3. This may be due to the change in the mass ratio of bentonite suspension, ethanol dispersion of nano-zero valent iron, and laccase aqueous solution in Preparation Example 4. This change affected the synergistic effect of laccase and nano-zero valent iron in the modified bentonite, leading to a decrease in the degradation and adsorption capacity for humic substances, thus affecting the overall suspended solids removal effect. The organic humic substance content increased to 25 mg / L after treatment, indicating that this change in mass ratio was unfavorable for the decomposition and adsorption of humic substances, resulting in a poorer humic substance removal effect.

[0129] The organic humic matter content in the treated wastewater in Example 5 was 29 mg / L, indicating that the adsorption capacity of the treatment agent prepared in this example for humic matter degradation products was weakened. Because sodium hydroxide solution was used instead of potassium hydroxide solution in Preparation Example 10 to prepare the activated biochar material, the pore structure and surface properties of the activated biochar material were altered, resulting in a decrease in its adsorption capacity and thus affecting the removal efficiency of suspended solids and humic matter.

[0130] In Example 6, the suspended solids removal rate of the treated wastewater was 96.16%. This indicates that when aluminum sulfate was used instead of polyferric chloride as a flocculant, the flocculation effect of aluminum sulfate was slightly inferior, resulting in a decrease in the overall suspended solids removal rate.

[0131] The suspended solids removal rates of the treated wastewater in Comparative Examples 1-4 were basically 94.41% and below. Compared with Examples 1-3, the suspended solids removal rate of the wastewater was significantly reduced. It can be seen that the main reason is that the content of organic humic substances in the wastewater of Comparative Examples 1-4 was still relatively high after treatment. This indicates that the treatment agents prepared in Comparative Examples 1-4 cannot effectively remove organic humic substances, thus leading to a decrease in the suspended solids removal rate.

[0132] The suspended solids removal rate of Comparative Example 1 was 93.82%, significantly lower than that of the Example. Using unmodified bentonite, which lacks the degradation and adsorption effects of laccase and nano-zero-valent iron on humic substances, the adsorption capacity of bentonite alone is insufficient to effectively remove humic substances from wastewater, thus affecting the overall suspended solids removal efficiency.

[0133] The suspended solids removal rate of Comparative Example 2 was 93.49%. Coal-based activated carbon, instead of biochar, had a different pore structure and surface functional groups than activated biochar, resulting in a weaker adsorption capacity for humic degradation products and other pollutants, thus affecting the removal of suspended solids.

[0134] The suspended solids removal rate of Comparative Example 3 was 94.16%. In Preparation Example 5, urease was used instead of laccase. Urease cannot effectively catalyze the oxidation of phenolic and aromatic amine compounds in humic substances like laccase, and therefore cannot degrade humic substances, thus reducing the removal efficiency of suspended solids.

[0135] The suspended solids removal rate of Comparative Example 4 was 94.41%. In Preparation Example 6, no nano-zero valent iron was added, which reduced the stability and activity of laccase, thus weakening its ability to degrade humic substances and consequently affecting the removal of suspended solids.

[0136] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A reagent for treating wastewater with high suspended solids in oilfields, characterized in that, It is made from the following raw materials in parts by weight: 40-60 parts modified bentonite; 5-15 parts ferrous sulfate; 5-15 parts aluminum ferric sulfate; 1-5 parts ethylenediaminetetraacetic acid; 10-20 parts activated biochar material; 3-8 parts chitosan; and 5-10 parts flocculant. The modified bentonite was prepared by the following method: A. Prepare an aqueous solution of laccase and an ethanol dispersion of nano-zero valent iron; add bentonite to deionized water, stir for 10-20 min, and then sonicate for 15-30 min to obtain a bentonite suspension; the concentration of the laccase aqueous solution is 10-50 mg / mL; the concentration of the ethanol dispersion of nano-zero valent iron is 5-20 mg / mL; the mass concentration of the bentonite suspension is 5%-10%; B. Place the bentonite suspension in a nitrogen-filled reactor. Under stirring conditions of 100-200 r / min, add the ethanol dispersion of nano-zero valent iron and stir for 1-2 h. Then add laccase aqueous solution to the reactor and maintain the reaction temperature at 30-40℃ for 2-4 h to obtain an intermediate solution. The mass ratio of bentonite suspension, ethanol dispersion of nano-zero valent iron and laccase aqueous solution is 10:(0.5-1):(1-2). C. Transfer the intermediate solution to a centrifuge tube and centrifuge at 3000-5000 r / min for 10-15 min under nitrogen protection to separate the solid precipitate. Then wash the solid precipitate and dry it under nitrogen atmosphere to obtain modified bentonite. The activated biochar material was prepared by the following method: Waste biomass is heated at 180-190℃ and with an oxygen volume concentration of 1%-5% for 2-3 hours to obtain semi-carbonized biomass. Then, the semi-carbonized biomass is soaked in potassium hydroxide solution for 12-24 hours. After soaking, the semi-carbonized biomass is dried and then calcined at 450-600℃ for 1-2 hours under anaerobic conditions to obtain activated biochar material. The flocculant is either polyferric chloride or polyacrylamide.

2. The agent for treating high suspended solids wastewater in oilfields according to claim 1, characterized in that, The mass concentration of the potassium hydroxide solution is 30%-40%, and the mass ratio of the semi-carbonized biomass to the potassium hydroxide solution is 1:(3-4).

3. The agent for treating high suspended solids wastewater in oilfields according to claim 1, characterized in that, The waste biomass can be any one of rice husks, corn stalks, and sugarcane bagasse.

4. The agent for treating high suspended solids wastewater in oilfields according to claim 1, characterized in that, The viscosity of the chitosan is 0.7-1 Pa·s.

5. A method for preparing a high-suspended-solids wastewater treatment agent for oilfields according to any one of claims 1-4, characterized in that, Includes the following steps: S1. Mix the modified bentonite and activated biochar materials and stir at 100-150 r / min for 5-10 min to obtain a premix. S2. Mix ferrous sulfate, aluminum ferric sulfate, ethylenediaminetetraacetic acid, chitosan and flocculant with the premix and continue stirring for 20-30 minutes to obtain the mixture; S3. Transfer the mixture to an extrusion granulator for extrusion granulation to obtain granular agent. Dry the granular agent at 60-80℃ for 3-5 hours to obtain an agent for treating high suspended solids wastewater in oilfields.

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