Chip wastewater resource utilization method and system thereof

Abstract

The application provides a chip wastewater resource utilization method and system, and steps of the method comprise the following: introducing chip production wastewater into a first adsorption column of a first treatment unit, the first adsorption column is internally provided with a calcium-magnesium composite adsorbent, when the chip production wastewater reaches preset transfer conditions, the chip production wastewater is transferred into a second adsorption column to obtain a primary treatment liquid; adding an acid treatment substance into the primary treatment liquid, and then transferring the primary treatment liquid into a composite biochar bed unit, the composite biochar bed unit comprises an upper treatment part and a lower treatment part, the upper treatment part is internally provided with a nitrogen-doped biochar layer, and the lower treatment part is internally provided with a high-aromaticity biochar layer, to obtain an intermediate treatment liquid; adding a coagulant into the intermediate treatment liquid, and then sequentially performing filtration, ultrafiltration and reverse osmosis operations to obtain resourceized water. The method fundamentally solves the defects that water quality is unstable after chip wastewater treatment in the prior art, and it is difficult to stably meet the reuse of ultrapure water.

Description

Technical Field

[0001] This invention belongs to the field of reclaimed water treatment technology, and particularly relates to a method and system for the resource utilization of chip wastewater. Background Technology

[0002] Semiconductor chip wastewater refers to industrial wastewater generated during the semiconductor chip manufacturing process. Chip production involves complex processes such as photolithography, etching, chemical vapor deposition, ion implantation, polishing (CMP), cleaning, and rinsing with large amounts of ultrapure water, all of which generate wastewater. Due to the diverse and sophisticated nature of these processes, semiconductor chip wastewater has an extremely complex composition, containing not only large amounts of inorganic salts and acids / alkalis, but also organic solvents, surfactants, metal ions, and particulate impurities.

[0003] Chip wastewater is characterized by large volume, significant fluctuations in water quality, and a wide variety of pollutants, and it requires extremely high quality after treatment. Therefore, wastewater often not only needs to meet discharge standards but also requires advanced treatment before reuse, and the effluent must meet both discharge and reuse requirements.

[0004] Existing methods for treating chip wastewater often employ single physicochemical approaches, such as lime precipitation for fluoride removal or conventional activated carbon adsorption for organic matter removal. While these methods can reduce pollutant concentrations to some extent, the wastewater composition is complex, containing fluoride ions, organic matter, metal ions, and particulate matter. These pollutants exhibit synergistic interference; for example, divalent metal ions form complexes with humic substances or low-molecular-weight organic matter, reducing the repulsion effect of subsequent membrane separation. Furthermore, other small-molecule organic matter has low adsorption efficiency on conventional activated carbon, easily causing membrane fouling when entering the reverse osmosis stage. Due to the combined effects of these multiple factors, traditional processes struggle to guarantee long-term, stable ultrapure water reuse standards. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method and system for the resource utilization of chip wastewater, which aims to solve the problem that the water quality of chip wastewater after treatment is unstable and it is difficult to meet the requirements for ultrapure water reuse in the prior art.

[0006] To solve the above-mentioned technical problems, the present invention is implemented as follows: a method for the resource utilization of chip wastewater is proposed, the steps of which include: S1. The chip manufacturing wastewater is introduced into the first adsorption column of the first treatment unit. The first adsorption column contains a calcium-magnesium composite adsorbent. When the chip manufacturing wastewater reaches the preset transfer conditions, it is transferred to the second adsorption column to obtain the primary treatment liquid. S2. Add acidic treatment material to the primary treatment solution and then transfer it to the composite biochar bed unit. The composite biochar bed unit includes an upper treatment section and a lower treatment section. The upper treatment section is provided with a nitrogen-doped biochar layer, and the lower treatment section is provided with a high-aromatic biochar layer to obtain the intermediate treatment solution. S3. Add coagulant to the intermediate treatment liquid, and then perform filtration, ultrafiltration and reverse osmosis operations in sequence to obtain resource-recovered water.

[0007] In some embodiments, step S1 includes: S1.1 The chip manufacturing wastewater is first introduced into the first adsorption column of the first treatment unit. The adsorption column is filled with calcium-magnesium composite adsorbent. The calcium-magnesium composite adsorbent is in the form of porous particles with a particle size range of 0.5~2mm. After passing through the first adsorption column, the first effluent is obtained. S1.2 When the fluoride ion concentration of the first effluent is detected to be greater than the preset first concentration, the first effluent is transferred to the second adsorption column; S1.3 When the concentration of fluoride ions in the liquid inside the second adsorption column is detected to be less than the preset second concentration, the liquid is discharged to obtain the primary treatment solution.

[0008] In some embodiments, steps S1.2 and S1.3 may further include: Inject the solution into the first adsorption column after draining the liquid, control the temperature at 20~40℃, maintain for 20~30min, then rinse with hydrochloric acid solution for 10~20min, and finally replace with water to obtain the regenerated solution.

[0009] In some embodiments, the calcium-magnesium composite adsorbent includes a calcium-based component, a magnesium-based component, and a porous support. The calcium-based component includes at least one of calcium carbonate, calcium hydroxide, and calcium oxide. The magnesium-based component includes at least one of magnesium oxide, magnesium hydroxide, and magnesium carbonate. The porous support includes at least one of alumina, zeolite, and silica. The calcium-based component accounts for 30-60 wt%, the magnesium-based component accounts for 10-30 wt%, and the porous support accounts for 30-40 wt%.

[0010] In some embodiments, step S2 includes: S2.1 The acidic treatment materials include carbon dioxide and citric acid. The primary treatment solution is heated to 20~30℃. Carbon dioxide is introduced into the primary treatment solution and citric acid is added dropwise. The flow rate of carbon dioxide is 10~80mg / L and the concentration of citric acid is 5~20mg / L, until the pH of the primary treatment solution is between 6.6 and 7. S2.2 Transfer the primary treatment liquid after adding acidic treatment material to the upper treatment section of the composite biochar bed unit. Adjust the pressure in the composite biochar bed unit to 0.05~0.15MPa and maintain the temperature at 20~30℃. A water storage chamber is provided between the upper treatment section and the lower treatment section. An electric valve is provided in the water storage chamber. The electric valve is used to control the liquid flow between the upper treatment section and the lower treatment section. S2.3. Detect the 254nm ultraviolet light absorption rate of the primary treatment liquid that has not entered the upper treatment section and the 254nm ultraviolet light absorption rate of the primary treatment liquid in the water storage chamber respectively. When the difference between the two is greater than the preset difference, open the electric valve in the water storage chamber to connect the upper treatment section and the lower treatment section, so that the primary treatment liquid enters the lower treatment section. S2.4 The primary treatment solution is kept in the lower treatment section for 8~15 minutes, and the liquid is discharged to obtain the intermediate treatment solution.

[0011] In some embodiments, the method further includes the following after step S2.4: Close the electric valve to isolate the upper and lower treatment sections. Start the air-water backwash on the upper treatment section, controlling the air flow rate at 10-15 Nm³. 3 / m 2 • h, backwash water rate 10~15 m / h, last for 6~8 min. After backwashing, inject 0.1~0.5% sodium bicarbonate solution, control the temperature at 60~80℃, and maintain for 10~20 min. The lower treatment section is backwashed at a water speed of 8-12 m / h for 8-10 minutes. Then, it is purged with hot air at 60-80℃ for 10-15 minutes. Subsequently, a 0.1-0.5% sodium hydroxide solution is injected at a temperature of 50-60℃ for 15-20 minutes. The liquids in the upper and lower treatment sections are then discharged to obtain alkaline washing waste liquid.

[0012] In some embodiments, the nitrogen-doped biochar layer includes a nitrogen source modification component, a biochar matrix, and auxiliary functional additives. The nitrogen source modification component includes at least one of urea, melamine, and ammonium nitrate. The biochar matrix includes at least one of rice husk char, corn cob char, and sawdust char. The auxiliary functional additives include at least one of graphene oxide, zeolite powder, and titanium dioxide nanoparticles. The high-aromaticity biochar layer includes a high-aromaticity carbon skeleton, a stability enhancer, and a surface modification component. The high-aromaticity carbon skeleton includes at least one of petroleum coke, lignite, and lignin char. The stability enhancer includes at least one of activated alumina, silica gel powder, and ceramsite powder. The surface modification component includes at least one of ferric sulfate, manganese nitrate, and phosphoric acid. In the nitrogen-doped biochar layer, the nitrogen source modification component accounts for 5-20 wt%, the biochar matrix accounts for 70-90 wt%, and the auxiliary functional additives account for 5-15 wt%. In the high-aromaticity biochar layer, the high-aromaticity carbon skeleton accounts for 60-85 wt%, the stability enhancer accounts for 10-25 wt%, and the surface modification component accounts for 5-15 wt%.

[0013] In some embodiments, in step S3, the coagulant includes at least one of aluminum sulfate, polyaluminum chloride, ferrous sulfate, and ferric chloride.

[0014] This invention proposes a chip wastewater resource recovery system, which employs a chip wastewater resource recovery method as described above.

[0015] Compared with existing technologies, the chip wastewater resource utilization method and system of this invention have the following advantages: In this method, step S1 first treats the chip manufacturing wastewater using a calcium-magnesium composite adsorbent to rapidly reduce the concentration of fluoride ions, while simultaneously intercepting colloids and particulate matter through a porous carrier. Fluoride ions are a typical pollutant in chip wastewater; if not treated thoroughly, they will not only affect the stability of the subsequent adsorbent and biochar layer but also cause irreversible damage to the membrane material during the reverse osmosis stage. By setting up a dual adsorption column system that operates alternately, continuous and stable fluoride removal can be achieved, ensuring that the fluoride ion content in the primary treatment solution remains at a low level, providing reliable feed water conditions for subsequent processes.

[0016] In step S2, acidification is performed by adding an acidic agent to stabilize the pH of the primary treated solution within the weakly acidic range. This operation disrupts the complex structure formed between divalent metal ions and humic organic matter, leaving the metal ions in a free state, which facilitates subsequent adsorption. Subsequently, the wastewater sequentially enters the upper and lower treatment sections of the composite biochar bed unit. The nitrogen-doped biochar in the upper layer achieves efficient adsorption of polar small-molecule organic matter through nitrogen functional groups, while the high-aromatic biochar in the lower layer utilizes its π–π interactions and hydrophobic properties to deeply remove aromatic and recalcitrant organic matter. Through the synergistic effect of the stratification function, the organic load and toxicity of the intermediate treated solution are significantly reduced, avoiding the water quality instability problems caused by residual organic pollutants and complexes in traditional processes.

[0017] In step S3, adding a coagulant to the intermediate-stage treated liquid further removes residual colloids and dissolved organic matter, reducing turbidity and organic carbon content. Then, combining filtration, ultrafiltration, and reverse osmosis operations, multi-stage removal of particulates, dissolved salts, and low-molecular-weight organic matter is achieved. Ultrafiltration effectively removes suspended solids and high-molecular-weight organic matter, while reverse osmosis has an extremely high rejection rate for dissolved salts and small-molecule pollutants, ensuring that the resistivity and organic matter content of the effluent meet the requirements for ultrapure water reuse. Through the continuous connection of S1, S2, and S3, this method can reduce fluoride ions at the source, precisely remove TMAH and organic matter, and finally achieve deep purification through multi-stage membrane separation, fundamentally solving the shortcomings of existing technologies in chip wastewater treatment where the water quality is unstable and difficult to reliably meet the requirements for ultrapure water reuse. Attached Figure Description

[0018] Figure 1 This is a schematic flowchart of a chip wastewater resource utilization method according to an embodiment of the present invention. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0020] This invention proposes a method for the resource utilization of chip wastewater, the steps of which include: S1. The chip manufacturing wastewater is introduced into the first adsorption column of the first treatment unit. The first adsorption column contains a calcium-magnesium composite adsorbent. When the chip manufacturing wastewater reaches the preset transfer conditions, it is transferred to the second adsorption column to obtain the primary treatment liquid.

[0021] Step S1 includes: S1.1 The chip manufacturing wastewater is first introduced into the first adsorption column of the first treatment unit. The adsorption column is filled with a calcium-magnesium composite adsorbent. The calcium-magnesium composite adsorbent is in the form of porous particles with a particle size range of 0.5~2mm. After passing through the first adsorption column, the first effluent is obtained. The calcium-magnesium composite adsorbent includes a calcium-based component, a magnesium-based component, and a porous carrier. The calcium-based component includes at least one of calcium carbonate, calcium hydroxide, and calcium oxide. The magnesium-based component includes at least one of magnesium oxide, magnesium hydroxide, and magnesium carbonate. The porous carrier includes at least one of alumina, zeolite, and silica. The calcium-based component accounts for 30~60wt%, the magnesium-based component accounts for 10~30wt%, and the porous carrier accounts for 30~40wt%.

[0022] After the chip manufacturing wastewater is introduced into the first adsorption column, the packed calcium-magnesium composite adsorbent begins to interact with fluoride ions and some colloidal particles in the wastewater. The calcium-based components (such as calcium carbonate, calcium hydroxide, and calcium oxide) release calcium ions, which combine with fluoride ions to form insoluble calcium fluoride precipitates, thus rapidly reducing the fluoride concentration in the wastewater. The magnesium-based components (such as magnesium oxide, magnesium hydroxide, and magnesium carbonate) provide a slower-release magnesium ion, which can form magnesium fluoride with fluoride and enhance removal capacity through surface complexation. It also has an adsorption and inhibition effect on some silicate ions and organic matter. The porous carrier (such as alumina, zeolite, and silica) provides a large specific surface area and physical channels, making it easier for fluoride ions and pollutants to be immobilized, thereby improving the overall removal rate and adsorption capacity. Through this combination, the fluoride ions in the wastewater are rapidly reduced, the effluent fluoride concentration decreases significantly, forming the first effluent and laying the foundation for subsequent processes.

[0023] S1.2 When the fluoride ion concentration of the first effluent is detected to be greater than the preset first concentration, the first effluent is transferred to the second adsorption column.

[0024] When the fluoride ion concentration in the first effluent rises above the set first concentration value, it indicates that the adsorption capacity of the first adsorption column is approaching saturation, and the fluoride removal capacity is gradually decreasing. Switching to the second adsorption column at this point prevents unremoved fluoride ions from directly entering the subsequent system, thus ensuring continuous and stable effluent quality. Simultaneously, the first adsorption column enters a regeneration state to prevent overload operation that could cause adsorbent structure collapse or scaling and clogging. This switching method utilizes online detection and valve group control to enable dynamic switching of adsorption units during uninterrupted system operation, ensuring continuous and effective fluoride ion reduction throughout the entire process.

[0025] In this embodiment, continuous online monitoring is performed using a fluoride ion-selective electrode (ISE), followed by verification using ion chromatography (IC) as the reference method, or SPADNS spectrophotometry as an alternative. Sampling points are arranged with one online ISE at each of the S1.1 effluent (first column effluent) and S1.3 effluent (second column effluent). IC sampling and comparison are performed once per shift. The online probe needs to be calibrated at two or three points using fluoride standard solutions of 1, 10, and 100 mg / L.

[0026] The steps between S1.2 and S1.3 also include: Inject the solution into the first adsorption column after draining the liquid, control the temperature at 20~40℃, maintain for 20~30min, then rinse with hydrochloric acid solution for 10~20min, and finally replace with water to obtain the regenerated solution.

[0027] After the first adsorption column stops operating, injecting an alkaline solution (such as sodium hydroxide solution) into the column and maintaining it at 20-40°C for 20-30 minutes dissolves or transforms the calcium fluoride and magnesium fluoride formed on the adsorbent surface, releasing the active sites of the adsorbent. Subsequently, rinsing with hydrochloric acid solution for 10-20 minutes removes residual alkaline deposits and restores the acid balance of the adsorbent surface, allowing it to regain its charge-carrying capacity and adsorption activity. Finally, rinsing with clean water removes residual reagents, preventing interference with the quality of subsequently treated water. The technical advantage of this series of steps is that the adsorbent can be recycled multiple times, reducing material costs while ensuring that the adsorption capacity is largely restored after regeneration, thereby improving the overall economy and sustainability of the system.

[0028] S1.3 When the concentration of fluoride ions in the liquid inside the second adsorption column is detected to be less than the preset second concentration, the liquid is discharged to obtain the primary treatment solution.

[0029] When the second adsorption column is running, fluoride ions in the wastewater are further removed by the calcium-magnesium composite adsorbent. When the effluent fluoride concentration is detected to be lower than the preset second concentration value, it can be confirmed that the treated water has reached stable compliance conditions. The discharged liquid at this time serves as the primary treated liquid for the next treatment stage, ensuring that the fluoride concentration remains within a safe range. Simultaneously, due to the relatively long empty bed contact time and unsaturated adsorbent active sites within the second adsorption column, some accompanying organic matter and divalent metal complexes are also reduced, thereby improving the influent conditions for the subsequent biochar bed and membrane system. The ultimate technical effect is to create a low-fluoride, low-organic-load primary treated liquid, ensuring the continuity, stability, and high treatment efficiency of the entire resource recovery treatment chain.

[0030] In this embodiment, the preset first concentration can be 5 mg / L. When the effluent from the first column reaches approximately 5 mg / L, it indicates that the effective sites at the front end are nearing saturation. Further pressure will carry unremoved fluoride into the subsequent carbon bed and increase the risk of calcium fluoride scaling in downstream equipment. Setting the preset first concentration at 5 mg / L balances treatment load and downstream safety. If the influent fluoride is particularly high (e.g., >150 mg / L), the preset first concentration can be optimized within a window of 3–8 mg / L.

[0031] The preset second concentration can be 1 mg / L, and can be further tightened to 0.5 mg / L for ultrapure water reuse scenarios. The purpose of this is to strictly intercept the fluoride load in the adsorption section, avoiding secondary scaling and clogging of sites in the subsequent carbon bed or membrane section with calcium and magnesium ions, while also providing stable low-fluoride feed water for coagulation and membrane sections.

[0032] S2. Add acidic treatment material to the primary treatment solution and then transfer it to the composite biochar bed unit. The composite biochar bed unit includes an upper treatment section and a lower treatment section. The upper treatment section contains a nitrogen-doped biochar layer, and the lower treatment section contains a high-aromatic biochar layer to obtain the intermediate treatment solution. The nitrogen-doped biochar layer comprises a nitrogen source modification component, a biochar matrix, and auxiliary functional additives. The nitrogen source modification component includes at least one of urea, melamine, and ammonium nitrate. The biochar matrix includes at least one of rice husk char, corn cob char, and sawdust char. The auxiliary functional additives include at least one of graphene oxide, zeolite powder, and titanium dioxide nanoparticles. The high-aromaticity biochar layer comprises a high-aromaticity carbon skeleton, a stability enhancer, and a surface modification component. The high-aromaticity carbon skeleton includes at least one of petroleum coke, lignite, and lignin char. The stability enhancer includes at least one of activated alumina, silica gel powder, and ceramsite powder. The surface modification component includes at least one of ferric sulfate, manganese nitrate, and phosphoric acid. In the nitrogen-doped biochar layer, the nitrogen source modification component accounts for 5-20 wt%, the biochar matrix accounts for 70-90 wt%, and the auxiliary functional additives account for 5-15 wt%. In the high-aromaticity biochar layer, the high-aromaticity carbon skeleton accounts for 60-85 wt%, the stability enhancer accounts for 10-25 wt%, and the surface modification component accounts for 5-15 wt%.

[0033] Step S2 includes: S2.1 The acidic treatment materials include carbon dioxide and citric acid. The primary treatment solution is heated to 20~30℃. Carbon dioxide is introduced into the primary treatment solution and citric acid is added dropwise. The flow rate of carbon dioxide is 10~80mg / L and the concentration of citric acid is 5~20mg / L, until the pH of the primary treatment solution is between 6.6 and 7.

[0034] Passing carbon dioxide into the primary treatment solution and adding citric acid provides mild acidification and buffering. The dissolved carbon dioxide forms carbonic acid, providing a reversible weakly acidic environment that converts tetramethylammonium hydroxide (TMAH) in the wastewater into a cationic form, thus reducing its competition for adsorption sites. Citric acid, a polycarboxylic acid, forms a stable buffer system within a pH range of 6.6 to 7 and undergoes complexation reactions with metal ions (such as calcium and nickel), disrupting the stable complexation structure between metals and humic substances. This process not only stabilizes the acid-base environment of the wastewater but also releases divalent metal ions for subsequent adsorption, improving the influent conditions for the subsequent biochar bed.

[0035] In one embodiment, after the carbon dioxide is introduced in step S2.1, nitrogen is continuously introduced for 1 to 2 minutes to remove the supersaturated dissolved carbon dioxide.

[0036] S2.2 Transfer the primary treatment liquid after adding acidic treatment material to the upper treatment section of the composite biochar bed unit. Adjust the pressure in the composite biochar bed unit to 0.05~0.15MPa and maintain the temperature at 20~30℃. A water storage chamber is provided between the upper treatment section and the lower treatment section. An electric valve is provided in the water storage chamber to control the liquid flow between the upper treatment section and the lower treatment section.

[0037] The acidified primary treatment solution is fed into the upper treatment section of the composite biochar bed. By maintaining stable system pressure and temperature, uniform contact between the liquid and the adsorption layer is ensured. The nitrogen-doped biochar layer in the upper treatment section contains nitrogen-modified components (such as urea, melamine, and ammonium nitrate), introducing pyridine nitrogen and pyrrole nitrogen functional groups into the carbon skeleton. These sites have strong electron-donating capabilities, enabling them to form hydrogen bonds or electrostatic interactions with polar small-molecule organic matter and cationic pollutants. Simultaneously, auxiliary functional additives such as graphene oxide, zeolite powder, and titanium dioxide nanoparticles further increase the specific surface area and adsorption channels, resulting in the efficient removal of TMAH, urea, and low-molecular-weight organic matter. The water storage chamber and electric valve allow for controlled segmented operation of the upper and lower treatment sections, preventing the lower layer from being subjected to high loads prematurely and extending the overall adsorption life.

[0038] S2.3. Detect the 254nm ultraviolet light absorption rate of the primary treatment liquid that has not entered the upper treatment section and the 254nm ultraviolet light absorption rate of the primary treatment liquid in the water storage chamber respectively. When the difference between the two is greater than the preset difference, open the electric valve in the water storage chamber to connect the upper treatment section and the lower treatment section, so that the primary treatment liquid enters the lower treatment section.

[0039] By comparing the ultraviolet (UV) absorbance at 254 nm between the primary treatment solution (before entering the upper treatment section) and the liquid in the storage chamber, the effectiveness of organic matter removal can be reflected in real time. When the difference in UV absorbance exceeds a set value, it indicates that the upper treatment section has significantly reduced organic matter and protein-like substances. At this point, the electric valve is opened to allow the liquid to flow into the lower treatment section. 254 nm UV absorption primarily characterizes the content of aromatic and conjugated organic matter in the water; its reduction indicates that the biochar layer has effectively captured the target pollutants. This online optical criterion enables segmented connectivity between the upper and lower layers, ensuring that the organic matter load in the water entering the lower treatment section remains within a controllable range, preventing premature saturation or breakthrough of the lower layer.

[0040] In this embodiment, the preset difference can be 60% of the 254nm ultraviolet light absorption rate of the primary treatment liquid that has not entered the upper treatment section, that is, the difference between the two / the 254nm ultraviolet light absorption rate of the primary treatment liquid that has not entered the upper treatment section = 60%.

[0041] S2.4 The primary treatment solution is kept in the lower treatment section for 8~15 minutes, and the liquid is discharged to obtain the intermediate treatment solution.

[0042] The primary treatment solution is held in the high-aromatic biochar layer in the lower treatment section for 8 to 15 minutes to achieve deep organic matter polishing. The high-aromatic carbon framework (such as petroleum coke, lignite, and lignin char) possesses abundant aromatic structures, enabling efficient adsorption of low-molecular-weight aromatic organic compounds through π-π stacking and hydrophobic interactions. Stabilizers (such as activated alumina, silica gel powder, and ceramsite powder) enhance the structural strength of the bed, preventing collapse or clogging during long-term operation. Surface-modifying components (such as ferric sulfate, manganese nitrate, and phosphoric acid) introduce polar functional groups and complexation sites onto the carbon surface, further enhancing the removal efficiency for hydrophobic organic compounds and metal-organic complex pollutants. After polishing in the lower layer, the resulting intermediate treatment solution not only has a low fluoride content but also a significantly reduced total organic matter content, meeting the feedwater requirements for subsequent membrane treatment.

[0043] The process after step S2.4 also includes: Close the electric valve to isolate the upper and lower treatment sections. Start the air-water backwash on the upper treatment section, controlling the air flow rate at 10-15 Nm³. 3 / m 2 The backwash water flow rate is 10-15 m / h, lasting for 6-8 minutes. After backwashing, inject 0.1-0.5% sodium bicarbonate solution, keeping the temperature at 60-80℃ for 10-20 minutes.

[0044] After shutting off the electric valve to isolate the upper and lower treatment sections, the upper treatment section undergoes air-water backwashing. This effectively flushes out suspended solids and colloidal particles retained in the pores, preventing a continuous increase in bed pressure differential. Subsequently, a 0.1-0.5% sodium hydroxide solution is injected and maintained at 60-80 degrees Celsius for a certain period. This desorbs small molecule organics and TMAH firmly bound to nitrogen functional groups, restoring the active sites. Through this process, the adsorption capacity of the nitrogen-doped biochar layer is regenerated, extending its service life. Simultaneously, the collected alkaline washing solution is rich in polar organic matter and alkaline contaminants, facilitating subsequent sorting and treatment.

[0045] The lower treatment section is backwashed at a water speed of 8-12 m / h for 8-10 minutes. Then, it is purged with hot air at 60-80℃ for 10-15 minutes. Subsequently, a 0.1-0.5% sodium hydroxide solution is injected at a temperature of 50-60℃ for 15-20 minutes. The liquids in the upper and lower treatment sections are then discharged to obtain alkaline washing waste liquid.

[0046] Backwashing the lower treatment section removes colloids and deposits accumulated in the carbon pores, maintaining bed permeability. Hot air purging at 60-80 degrees Celsius removes weakly bound organic matter and physical water films adsorbed on the surface of highly aromatic carbon, preventing a decrease in re-adsorption efficiency. Subsequent injection of a 0.1-0.5% sodium hydroxide solution, maintained at 50-60 degrees Celsius for a certain period, desorbs aromatic DOM and hydrophobic organic matter, restoring the π-π stacked adsorption capacity of the carbon surface. The final alkaline washing wastewater, containing a high concentration of hydrophobic organic matter, is collected separately and is suitable for incorporating into the RO concentrate for centralized deep treatment, avoiding disruption to the biochemical system and achieving co-processing of the wastewater.

[0047] S3. Add a coagulant to the intermediate-stage treated liquid, and then perform filtration, ultrafiltration, and reverse osmosis operations in sequence to obtain resource-recovered water. The coagulant includes at least one of aluminum sulfate, polyaluminum chloride, ferrous sulfate, and ferric chloride.

[0048] Step S3 includes: S3.1 Adjust the pH of the intermediate treatment solution to 6.6-7, add the coagulant first, then add cationic polyacrylamide with a concentration of 0.1-0.5 mg / L, stir for 5-10 min to obtain the flocculated mixture; S3.2 Transfer the flocculated mixture to a filtration device containing filter particles, including anthracite and quartz sand, with a particle size of 0.6~1.6mm. After filtration, the filtrate is obtained. S3.3 Transfer the filtrate to an ultrafiltration device, which is equipped with an ultrafiltration membrane, including at least one of polyvinylidene fluoride ultrafiltration membrane, polyethersulfone ultrafiltration membrane, and polypropylene ultrafiltration membrane. The membrane pressure difference is set to 0.8 to 1.5 bar, and the temperature is set to 20 to 30°C to obtain ultrafiltrate. S3.4. Add a phosphorus-free scale inhibitor to the ultrafiltrate, then transfer the ultrafiltrate to a reverse osmosis unit. The reverse osmosis unit contains a reverse osmosis membrane, which includes at least one of an aromatic polyamide composite membrane, a polyamide composite antifouling membrane, and a cellulose acetate membrane. Pressurize the feed water pressure of the ultrafiltrate to 12-18 bar to obtain recycled water. The phosphorus-free scale inhibitor includes at least one of polyacrylic acid, polymethacrylic acid, acrylic acid-acrylamide copolymer, polycarboxyvinyl sulfonic acid, and 2-acrylamide-2-methylpropanesulfonic acid copolymer.

[0049] In one embodiment, it is necessary to determine whether the coagulant added to the intermediate-stage treated liquid is an aluminum salt or an iron salt. The following equation is proposed to determine this: To be at wavelength The extinction coefficient at that point, in m. -1The sampling point was the intermediate treatment solution at point S2.4. (Before entering S3), the sample is filtered through a 0.45μm filter membrane at a temperature controlled at 20~25℃. A UV-Vis spectrophotometer (or an online UV probe) is used to scan at 250~280nm with a scan width of 1nm, and each scan is recorded. of And convert to The conversion formula is: , The optical path length is the effective path length of light through the sample in the detection cell. In the embodiments, The value can be as low as 0.1 μm. DOC stands for Dissolved Organic Carbon, measured in mg / L. When detecting DOC, a representative water sample must first be collected from the target effluent point of the process flow. During sampling, it is crucial to ensure the water sample is not subject to secondary contamination. Clean glass or PTFE bottles are typically used, ensuring the sample is completely filled and protected from light. The sample should be immediately placed in a 4°C refrigerator to prevent degradation of organic matter. Before testing, the collected water sample must be filtered through a 0.45 μm filter membrane to remove suspended particles and colloidal components, retaining only the true dissolved organic matter, which is the target for DOC detection. In the experimental preparation stage, the filtered sample needs to be adjusted to a pH close to 2 with the addition of hydrochloric acid or phosphoric acid to release bicarbonates and carbonates. Then, it is stripped with nitrogen or air for 3–5 minutes to remove inorganic carbon and strippable organic carbon, ensuring that the remaining portion consists of non-strippable dissolved organic carbon. Subsequently, the pretreated water sample was sent to a TOC / DOC analyzer. In high-temperature combustion-NDIR mode, the sample was injected into a quartz tube furnace, and organic carbon was completely oxidized to CO2 under the action of a platinum catalyst at 680~1000℃; or in UV / persulfate mode, CO2 was generated through 185 / 254nm UV irradiation and persulfate oxidation. The detection process used a non-dispersive infrared detector (NDIR) to quantitatively monitor the absorption peak area of ​​CO2 and compare it with a standard curve, finally converting it into DOC concentration, with the result expressed in mg / L (calculated as carbon). This represents the width of the integration band, in nm. In this embodiment, it is fixed at 30 nm, indicating a band width of 250 to 280 nm. UV absorbance, in L·mg -1 ·m -1 ,like ≤2.0L·mg -1 ·m -1If S > 2.0 L·mg⁻¹·m⁻¹, it indicates that the intermediate-stage treated liquid has low turbidity, mainly composed of hydrophilic / small-molecule dissolved organic matter, and that at least one of aluminum sulfate and polyaluminum chloride is used as the coagulant, resulting in clear effluent with low residue. If S > 2.0 L·mg⁻¹·m⁻¹, it indicates that the intermediate-stage treated liquid has high turbidity, with a high proportion of aromatic / hydrophobic dissolved organic matter, and that at least one of ferrous sulfate and ferric chloride is used as the coagulant.

[0050] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for resource recovery from chip wastewater, characterized by the following steps: include: S1. The chip manufacturing wastewater is introduced into the first adsorption column of the first treatment unit. The first adsorption column contains a calcium-magnesium composite adsorbent. When the chip manufacturing wastewater reaches the preset transfer conditions, it is transferred to the second adsorption column to obtain the primary treatment liquid. S2. Add acidic treatment material to the primary treatment solution and then transfer it to the composite biochar bed unit. The composite biochar bed unit includes an upper treatment section and a lower treatment section. The upper treatment section is provided with a nitrogen-doped biochar layer, and the lower treatment section is provided with a high-aromatic biochar layer to obtain the intermediate treatment solution. S3. Add coagulant to the intermediate treatment liquid, and then perform filtration, ultrafiltration and reverse osmosis operations in sequence to obtain resource-recovered water.

2. The method for resource recovery of chip wastewater according to claim 1, characterized in that, Step S1 includes: S1.1 The chip manufacturing wastewater is first introduced into the first adsorption column of the first treatment unit. The adsorption column is filled with calcium-magnesium composite adsorbent. The calcium-magnesium composite adsorbent is in the form of porous particles with a particle size range of 0.5~2mm. After passing through the first adsorption column, the first effluent is obtained. S1.2 When the fluoride ion concentration of the first effluent is detected to be greater than the preset first concentration, the first effluent is transferred to the second adsorption column; S1.3 When the concentration of fluoride ions in the liquid inside the second adsorption column is detected to be less than the preset second concentration, the liquid is discharged to obtain the primary treatment solution.

3. The method for resource recovery of chip wastewater according to claim 2, characterized in that, The steps between S1.2 and S1.3 also include: Inject alkaline solution into the first adsorption column after draining the liquid, control the temperature at 20~40℃, maintain for 20~30 minutes, then rinse with hydrochloric acid solution for 10~20 minutes, and finally replace with clean water to obtain regenerated solution.

4. A method for resource recovery of chip wastewater according to claim 2 or 3, characterized in that, The calcium-magnesium composite adsorbent includes a calcium-based component, a magnesium-based component, and a porous support. The calcium-based component includes at least one of calcium carbonate, calcium hydroxide, and calcium oxide. The magnesium-based component includes at least one of magnesium oxide, magnesium hydroxide, and magnesium carbonate. The porous support includes at least one of alumina, zeolite, and silica. The calcium-based component accounts for 30-60 wt%, the magnesium-based component accounts for 10-30 wt%, and the porous support accounts for 30-40 wt%.

5. The method for resource recovery of chip wastewater according to claim 1, characterized in that, Step S2 includes: S2.1 The acidic treatment materials include carbon dioxide and citric acid. The primary treatment solution is heated to 20~30℃. Carbon dioxide is introduced into the primary treatment solution and citric acid is added dropwise. The flow rate of carbon dioxide is 10~80mg / L and the concentration of citric acid is 5~20mg / L, until the pH of the primary treatment solution is between 6.6 and 7. S2.2 Transfer the primary treatment liquid after adding acidic treatment material to the upper treatment section of the composite biochar bed unit. Adjust the pressure in the composite biochar bed unit to 0.05~0.15MPa and maintain the temperature at 20~30℃. A water storage chamber is provided between the upper treatment section and the lower treatment section. An electric valve is provided in the water storage chamber. The electric valve is used to control the liquid flow between the upper treatment section and the lower treatment section. S2.

3. Detect the 254nm ultraviolet light absorption rate of the primary treatment liquid that has not entered the upper treatment section and the 254nm ultraviolet light absorption rate of the primary treatment liquid in the water storage chamber respectively. When the difference between the two is greater than the preset difference, open the electric valve in the water storage chamber to connect the upper treatment section and the lower treatment section, so that the primary treatment liquid enters the lower treatment section. S2.4 The primary treatment solution is kept in the lower treatment section for 8~15 minutes, and the liquid is discharged to obtain the intermediate treatment solution.

6. The method for resource recovery of chip wastewater according to claim 5, characterized in that, The process after step S2.4 also includes: Close the electric valve to isolate the upper and lower treatment sections. Start the air-water backwash on the upper treatment section, controlling the air flow rate at 10-15 Nm³. 3 / m 2 • h, backwash water rate 10~15 m / h, last for 6~8 min. After backwashing, inject 0.1~0.5% sodium bicarbonate solution, control the temperature at 60~80℃, and maintain for 10~20 min. The lower treatment section is backwashed at a water speed of 8-12 m / h for 8-10 minutes. Then, it is purged with hot air at 60-80℃ for 10-15 minutes. Subsequently, a 0.1-0.5% sodium hydroxide solution is injected at a temperature of 50-60℃ for 15-20 minutes. The liquids in the upper and lower treatment sections are then discharged to obtain alkaline washing waste liquid.

7. A method for resource recovery of chip wastewater according to claim 5 or 6, characterized in that, The nitrogen-doped biochar layer comprises a nitrogen source modification component, a biochar matrix, and auxiliary functional additives. The nitrogen source modification component includes at least one of urea, melamine, and ammonium nitrate. The biochar matrix includes at least one of rice husk char, corn cob char, and sawdust char. The auxiliary functional additives include at least one of graphene oxide, zeolite powder, and titanium dioxide nanoparticles. The high-aromaticity biochar layer comprises a high-aromaticity carbon skeleton, a stability enhancer, and a surface modification component. The high-aromaticity carbon skeleton includes at least one of petroleum coke, lignite, and lignin char. The stability enhancer includes at least one of activated alumina, silica gel powder, and ceramsite powder. The surface modification component includes at least one of ferric sulfate, manganese nitrate, and phosphoric acid. In the nitrogen-doped biochar layer, the nitrogen source modification component accounts for 5-20 wt%, the biochar matrix accounts for 70-90 wt%, and the auxiliary functional additives account for 5-15 wt%. In the high-aromaticity biochar layer, the high-aromaticity carbon skeleton accounts for 60-85 wt%, the stability enhancer accounts for 10-25 wt%, and the surface modification component accounts for 5-15 wt%.

8. A method for resource recovery of chip wastewater according to claim 1, characterized in that, In step S3, the coagulant includes at least one of aluminum sulfate, polyaluminum chloride, ferrous sulfate, and ferric chloride.

9. A chip wastewater resource recovery system, characterized in that, The method for resource recovery of chip wastewater as described in any one of claims 1-8 is adopted.

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