Process and system for removing heavy metals from ink wastewater

Abstract

This invention relates to the field of wastewater treatment technology, specifically to a process and system for removing heavy metals from ink wastewater. It includes the following steps: coagulating ink wastewater with a metal composite coagulant, adsorbing and removing sludge wastewater with an ink sludge-based adsorbent, and filtering wastewater using a catechol-modified polyethersulfone membrane, followed by detection. This invention utilizes high-iron copper slag with titanium tetrachloride and acetylacetone to prepare a metal composite coagulant, transforming the copper slag into a high-value-added water treatment agent. This significantly reduces the production cost of the coagulant. Through the synergistic leaching of dilute sulfuric acid and hydrogen peroxide, the iron element in the copper slag is efficiently extracted and oxidized into Fe, which has a strong coagulation effect. 3+ The trace amounts of copper and other metal ions dissolved also provide a basis for subsequent composite reactions, thus improving the overall treatment efficiency and effluent quality of oily sludge wastewater.

Description

A process and system for removing heavy metals from ink wastewater Technical Field

[0001] This invention relates to the field of wastewater treatment technology, specifically to a process and system for removing heavy metals from ink wastewater. Background Technology

[0002] Ink wastewater is a complex industrial wastewater containing a large amount of heavy metal ions, organic pigments, resins, solvents, and stable emulsions. In existing technologies, methods such as chemical precipitation, adsorption, ion exchange, and membrane separation are often used to remove heavy metals. However, a single method is often insufficient to cope with the complex system of ink wastewater, and there are problems such as limited adsorbent capacity, serious membrane fouling, large sludge production, and failure to recover heavy metal resources.

[0003] In the pretreatment stage, coagulation and sedimentation are commonly used, but traditional coagulants have limited effectiveness in treating soluble heavy metals and stable emulsion systems. Adsorption methods are widely used, but commercial adsorbents are expensive and have poor tolerance to competitive adsorption of coexisting organic matter in ink wastewater. Membrane technology can achieve deep purification, but membrane fouling and concentrate treatment issues limit its widespread application. Furthermore, existing processes mostly focus on simple pollutant removal, failing to achieve waste resource utilization and resulting in high treatment costs.

[0004] Therefore, there is an urgent need to develop a high-efficiency, economical ink wastewater treatment process and system that combines deep removal of heavy metals with resource recovery. This invention aims to overcome the shortcomings of existing technologies by converting iron-copper slag into a high-efficiency composite coagulant and further recycling the resulting sludge into a high-performance adsorbent material. This provides a process and system for removing heavy metals from ink wastewater, thus addressing the deficiencies of existing technologies. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a process and system for removing heavy metals from ink wastewater.

[0006] A process for removing heavy metals from ink wastewater includes the following steps:

[0007] S1: Metal composite coagulant coagulates ink wastewater

[0008] Ink wastewater is collected in a collection tank and then pumped into a coagulation tank via a vacuum pump. 0.2-0.4 g / L of metal composite coagulant is added to the coagulation tank, stirred evenly, heated to 70-80℃ and kept at that temperature for 30-40 minutes, and then cooled to room temperature for mud-water separation to obtain sludge-removed wastewater and ink sludge. The ink sludge is filtered out and used to prepare ink sludge-based adsorbent, while the sludge-removed wastewater enters the sludge adsorption tank.

[0009] S2: Ink sludge-based adsorbent for adsorbing and removing sludge wastewater

[0010] Add 10-12 g / L of ink sludge-based adsorbent to the sludge adsorption tank and adsorb for 60-70 minutes. During this period, stir the sludge adsorption tank by pumping oxygen at a rate of 1.5-2.5 kg O2 / m³. 3 Then let it stand for 30-40 minutes, filter to remove sediment, and the filtrate enters the membrane filtration tank;

[0011] S3: Catechol-modified polyethersulfone membrane filtration and detection of wastewater

[0012] The membrane filtration tank is equipped with a catechol-modified polyethersulfone membrane. The filtrate is filtered through the catechol-modified polyethersulfone membrane. The filtered liquid enters the detection tank to test whether the heavy metal content meets the standard. If it does not meet the standard, the filtered liquid is returned to the sludge adsorption tank and the above steps are repeated. Once it meets the standard, it can be discharged.

[0013] Furthermore, the preparation method of the metal composite coagulant in step S1 specifically includes the following steps:

[0014] The copper slag is ground through a 200-mesh sieve to obtain fine copper slag. 100-110 parts by weight of fine copper slag, 300-310 parts by weight of dilute sulfuric acid and 5-9 parts by weight of hydrogen peroxide are mixed and leached at 80-90℃ for 2-3 hours. The filter residue is then removed by filtration to obtain copper slag leachate.

[0015] 60-70 parts by mass of TiCl4 were slowly added to 100-110 parts by mass of anhydrous ethanol and stirred to form a dispersion system. Then, 40-48 parts by mass of acetylacetone were slowly added and reacted in a water bath at 60-70°C for 1-2 hours to obtain a titanium complex solution.

[0016] The copper slag leachate and titanium complex solution were mixed at a volume ratio of (3-4):1, and the pH was adjusted to 2.5-3. The reaction was carried out for 1-2 hours, and the resulting product was aged at 60-64℃ for 24-30 hours to obtain a metal composite coagulant.

[0017] Furthermore, the preparation method of the ink sludge-based adsorbent in step S2 specifically includes the following steps:

[0018] Add 20-30 parts by weight of 1,2-dichloroethane to 10-16 parts by weight of ink sludge, heat in a water bath at 70-76℃ for 30-40 minutes, then slowly add 2-4 parts by weight of glucose, maintain the temperature at 70-76℃ and continue stirring for 10-20 minutes, then slowly add 16-20 parts by weight of 98wt% concentrated sulfuric acid, raise the temperature to 90-100℃, stir and react for 3-4 hours, cool to room temperature (23-25℃), filter, wash the filter residue with deionized water until the pH of the filtrate is neutral, filter by suction, dry, grind through a 100-mesh sieve, and store for later use to obtain ink sludge-based adsorbent.

[0019] Furthermore, the preparation method of the catechol-modified polyethersulfone film in step S3 specifically includes the following steps:

[0020] Add 2-2.4 g / L catechol and 2-2.4 g / L tetraethylenepentamine to Tris buffer, stir magnetically for 30-40 min until completely dissolved, and let stand for 10-15 min to obtain catechol-based coating solution.

[0021] The pretreated polyethersulfone membrane was completely immersed in the catechol-based coating solution and horizontally oscillated at 60-80 rpm at room temperature of 23-25℃ for 4-8 hours. After the reaction, the surface of the polyethersulfone membrane was rinsed with deionized water 2-3 times. Then, the polyethersulfone membrane was placed in an oven at 60-70℃ for 30-40 minutes for heat treatment, and then thoroughly dried in an oven at 40-50℃ to obtain the catechol-based modified polyethersulfone membrane.

[0022] Furthermore, the concentration of the dilute sulfuric acid is 10-15 wt%.

[0023] Furthermore, copper slag is the slag produced after refining copper ore, which contains 30-60 wt% iron and also contains calcium oxide, aluminum oxide, magnesium oxide, silicon dioxide, and copper.

[0024] Further, the specific steps for pretreatment of the polyethersulfone membrane are as follows: immerse the polyethersulfone membrane in 1M NaOH solution for 30-40 minutes, then remove it and immerse it in anhydrous ethanol for 15-25 minutes of ultrasonication, and finally immerse it in deionized water for 15-25 minutes of ultrasonication. After removal, dry it completely in an oven at 40-50℃ to obtain the pretreated polyethersulfone membrane.

[0025] Furthermore, the Tris buffer is specifically a Tris-HCl buffer with a pH of 8.5 and a concentration of 10 mM.

[0026] Furthermore, the polyethersulfone membrane has a pore size of 0.22 μm.

[0027] A system for removing heavy metals from ink wastewater, the system being capable of the above-mentioned process, the system comprising a collection tank, a coagulation tank, a sludge adsorption tank, a membrane filtration tank, and a detection tank;

[0028] The collection tank is used to collect ink wastewater. The outlet of the collection tank is connected to the inlet of the coagulation tank. The outlet of the coagulation tank is connected to the inlet of the sludge adsorption tank. The outlet of the sludge adsorption tank is connected to the inlet of the membrane filtration tank. The outlet of the membrane filtration tank is connected to the inlet of the detection tank. The detection tank has a first outlet and a second outlet. The first outlet of the detection tank is connected to the sludge adsorption tank. The second outlet of the detection tank is used to discharge the liquid in the tank.

[0029] The present invention has the following advantages:

[0030] 1. This invention utilizes high-iron copper slag with titanium tetrachloride and acetylacetone to prepare a metal composite coagulant, transforming the copper slag into a high-value-added water treatment agent. This not only significantly reduces the production cost of the coagulant, but also, through the synergistic leaching of dilute sulfuric acid and hydrogen peroxide, efficiently extracts and oxidizes the iron element in the copper slag into Fe, which has a strong coagulation effect. 3+ The trace amounts of copper and other metal ions dissolved also provide a foundation for subsequent composite reactions. The addition of acetylacetone and titanium tetrachloride for pre-complexation generates a stable titanium complex, effectively preventing premature hydrolysis and precipitation of titanium ions before mixing. This ensures that the titanium component can participate in subsequent reactions in a controllable manner and achieve uniform molecular-level composites with components such as iron and copper. Finally, under specific pH conditions and during aging, multiple metal ions, including iron, titanium, and copper, undergo copolymerization reactions to form an inorganic-organic hybrid polymer. This polymer contains iron and titanium... The inorganic-organic hybrid polymer of copper contains highly positively charged polynuclear hydroxy iron-titanium complexes, which can efficiently neutralize the negative charge on the surface of ink wastewater, fundamentally destroying the stability of the emulsion system and achieving oil-water separation. The hydrolysis products of the titanium component have a strong adsorption bridging effect, while the iron component is used to form dense hydroxide flocs. The two work together to form flocs with a fast settling speed, effectively capturing and sweeping away the demulsified oil droplets, fine suspended solids and colloids in the water, forming co-precipitates, thus improving the overall treatment efficiency and effluent quality of oil sludge wastewater.

[0031] 2. This invention reacts ink sludge containing an iron-titanium-copper metal composite coagulant with 1,2-dichloroethane, glucose, and concentrated sulfuric acid. 1,2-dichloroethane acts as an extractant and pore-forming agent, removing organic impurities from the ink sludge and constructing a porous framework for subsequent reactions. Glucose, as an auxiliary carbon source, cokes in an acidic environment to form an amorphous carbon matrix, further optimizing the pore structure. Subsequently, concentrated sulfuric acid acts as a dehydrating agent to carbonize the organic matter, and a sulfonating agent introduces high-density hydrophilic sulfonic acid groups onto the formed carbon framework. The iron-titanium-copper composite coagulant pre-existing in the ink sludge acts as a highly efficient catalyst, significantly promoting the sulfonation reaction and ensuring more complete and robust grafting of the sulfonic acid groups. Simultaneously, the metal oxides / hydroxides formed by its hydrolysis constitute a robust inorganic framework, effectively preventing the collapse of the carbon framework during high-temperature acid treatment and ensuring the formation of a well-developed and stable pore structure. By utilizing the built-in metal component as a catalyst and structural enhancer, a highly efficient adsorbent with both well-developed pores and abundant functional groups is successfully prepared, improving the adsorption capacity for heavy metals.

[0032] 3. This invention pretreats and functionalizes the polyethersulfone (PES) membrane. Through the synergistic effect of catechol and tetraethylenepentamine, a functional coating capable of adsorbing heavy metal ions is constructed on the PES membrane surface. In the weakly alkaline Tris buffer solution, catechol is oxidized to highly reactive o-benzoquinone and combines with the amino groups in the tetraethylenepentamine molecule through an addition reaction. This process not only forms a stable three-dimensional cross-linked network on the membrane surface, but also introduces functional groups that efficiently adsorb heavy metals. The catechol groups of catechol have both complexing and reducing abilities for heavy metal ions; while the multiple amino groups of tetraethylenepentamine can strongly chelate with heavy metal ions. The two work together to construct a functional layer for capturing heavy metals on the membrane surface. By transforming the polyethersulfone membrane from passive sieving to active adsorption, it can efficiently and effectively remove various heavy metal ions in wastewater. In addition, the introduction of a large number of hydrophilic groups enhances the membrane's hydrophilicity, which helps to alleviate membrane pore clogging caused by organic pollutants in ink wastewater, improves antifouling ability, and ensures that the catechol-modified polyethersulfone membrane can maintain efficient operation for a longer period of time in complex ink wastewater environments, thus extending its service life. Attached Figure Description

[0033] Figure 1 is a process flow diagram of the removal of heavy metals from ink wastewater according to the present invention.

[0034] Figure 2 is a schematic diagram of the system for removing heavy metals from ink wastewater according to the present invention. Detailed Implementation

[0035] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of this invention.

[0036] Example 1:

[0037] A process for removing heavy metals from ink wastewater, as shown in Figure 1, includes the following steps:

[0038] S1: Metal composite coagulant coagulates ink wastewater

[0039] Copper slag is ground through a 200-mesh sieve to obtain fine copper slag. 100 parts by weight of fine copper slag, 300 parts by weight of 10 wt% dilute sulfuric acid and 5 parts by weight of hydrogen peroxide are mixed and leached at 80°C for 2 hours. The filter residue is then removed by filtration to obtain copper slag leachate.

[0040] 60 parts by mass of TiCl4 were slowly added to 100 parts by mass of anhydrous ethanol and stirred to form a dispersion system. Then, 40 parts by mass of acetylacetone were slowly added and reacted in a water bath at 60°C for 1 hour to obtain a titanium complex solution.

[0041] Copper slag leachate and titanium complex solution were mixed at a volume ratio of 3:1, and the pH was adjusted to 2.5. The reaction was carried out for 1 hour, and the resulting product was matured at 60°C for 24 hours to obtain a metal composite coagulant. The copper slag was the slag produced after copper ore refining, which contained 30 wt% iron, calcium oxide, aluminum oxide, magnesium oxide, silicon dioxide and copper.

[0042] Ink wastewater is collected in a collection tank and then pumped into a coagulation tank via a vacuum pump. 0.2 g / L of metal composite coagulant is added to the coagulation tank, stirred evenly, heated to 70°C and kept at that temperature for 30 minutes, and then cooled to room temperature for mud-water separation to obtain desludge wastewater and ink sludge. The ink sludge is filtered out and used to prepare ink sludge-based adsorbent, while the desludge wastewater enters the sludge adsorption tank.

[0043] S2: Ink sludge-based adsorbent for adsorbing and removing sludge wastewater

[0044] Add 20 parts by mass of 1,2-dichloroethane to 10 parts by mass of ink sludge, heat in a water bath at 70°C for 30 minutes, then slowly add 2 parts by mass of glucose, maintain the temperature at 70°C and continue stirring for 10 minutes, then slowly add 16 parts by mass of 98wt% concentrated sulfuric acid, raise the temperature to 90°C, stir and react for 3 hours, cool to room temperature (23°C) and filter, wash the filter residue with deionized water until the pH of the filtrate is neutral, filter by suction, dry, grind through a 100-mesh sieve, and store for later use to obtain ink sludge-based adsorbent;

[0045] Add 10 g / L of ink-based sludge adsorbent to the sludge adsorption tank and allow it to adsorb for 60 minutes. During this time, stir the sludge adsorption tank by pumping oxygen at a rate of 1.5 kg O2 / m³. 3 After standing for 30 minutes, the sediment was removed by filtration, and the filtrate entered the membrane filtration tank.

[0046] S3: Catechol-modified polyethersulfone membrane filtration and detection of wastewater

[0047] Add 2 g / L catechol and 2 g / L tetraethylenepentamine to Tris buffer, stir magnetically for 30 min until completely dissolved, let stand for 10 min to obtain catechol-based coating solution. Specifically, the Tris buffer is a 10 mM Tris-HCl buffer with pH 8.5.

[0048] A polyethersulfone membrane with a pore size of 0.22 μm was immersed in 1M NaOH solution for 30 min, then removed and immersed in anhydrous ethanol and sonicated for 15 min. Finally, it was immersed in deionized water and sonicated for 15 min. After removal, it was completely dried in an oven at 40℃ to obtain a pretreated polyethersulfone membrane.

[0049] The pretreated polyethersulfone membrane was completely immersed in the catechol-based coating solution and horizontally oscillated at 60 rpm at 23°C for 4 hours. After the reaction, the surface of the polyethersulfone membrane was rinsed twice with deionized water. Then, the polyethersulfone membrane was placed in a 60°C oven for 30 min and thoroughly dried in a 40°C oven to obtain the catechol-based modified polyethersulfone membrane.

[0050] The membrane filtration tank is equipped with a catechol-modified polyethersulfone membrane. The filtrate is filtered through the catechol-modified polyethersulfone membrane. The filtered liquid enters the detection tank to test whether the heavy metal content meets the standard. If it does not meet the standard, the filtered liquid is returned to the sludge adsorption tank and the above steps are repeated. Once it meets the standard, it can be discharged.

[0051] A system for removing heavy metals from ink wastewater, which is capable of the above-mentioned process, as shown in Figure 2, includes a collection tank, a coagulation tank, a sludge adsorption tank, a membrane filtration tank, and a detection tank.

[0052] The collection tank is used to collect ink wastewater. The outlet of the collection tank is connected to the inlet of the coagulation tank. The outlet of the coagulation tank is connected to the inlet of the sludge adsorption tank. The outlet of the sludge adsorption tank is connected to the inlet of the membrane filtration tank. The outlet of the membrane filtration tank is connected to the inlet of the detection tank. The detection tank has a first outlet and a second outlet. The first outlet of the detection tank is connected to the sludge adsorption tank. The second outlet of the detection tank is used to discharge the liquid in the tank.

[0053] Example 2:

[0054] A process for removing heavy metals from ink wastewater, as shown in Figure 1, includes the following steps:

[0055] S1: Metal composite coagulant coagulates ink wastewater

[0056] The copper slag was ground through a 200-mesh sieve to obtain fine copper slag. 105 parts by weight of the fine copper slag, 305 parts by weight of 13 wt% dilute sulfuric acid and 7 parts by weight of hydrogen peroxide were mixed and leached at 85°C for 2.5 hours. The filter residue was then removed by filtration to obtain copper slag leachate.

[0057] 65 parts by mass of TiCl4 were slowly added to 105 parts by mass of anhydrous ethanol and stirred to form a dispersion system. Then, 44 parts by mass of acetylacetone were slowly added and reacted in a water bath at 65°C for 1.5 hours to obtain a titanium complex solution.

[0058] Copper slag leachate and titanium complex solution were mixed at a volume ratio of 3.5:1, and the pH was adjusted to 2.8. The reaction was carried out for 1.5 hours, and the resulting product was aged at 62°C for 27 hours to obtain a metal composite coagulant. The copper slag was the slag produced after copper ore refining, which contained 45wt% iron, calcium oxide, aluminum oxide, magnesium oxide, silicon dioxide and copper.

[0059] Ink wastewater is collected in a collection tank and then pumped into a coagulation tank via a vacuum pump. 0.3 g / L of metal composite coagulant is added to the coagulation tank, stirred evenly, heated to 75°C and kept at that temperature for 35 min, and then cooled to room temperature for mud-water separation to obtain sludge-removed wastewater and ink sludge. The ink sludge is filtered out and used to prepare ink sludge-based adsorbent, while the sludge-removed wastewater enters the sludge adsorption tank.

[0060] S2: Ink sludge-based adsorbent for adsorbing and removing sludge wastewater

[0061] Add 25 parts by mass of 1,2-dichloroethane to 14 parts by mass of ink sludge, heat in a water bath at 73°C for 35 minutes, then slowly add 3 parts by mass of glucose, maintain the temperature at 73°C and continue stirring for 15 minutes, then slowly add 18 parts by mass of concentrated sulfuric acid with a concentration of 98wt%, raise the temperature to 95°C, stir and react for 3.5 hours, cool to room temperature (24°C), filter, wash the filter residue with deionized water until the pH of the filtrate is neutral, filter by suction, dry, grind through a 100-mesh sieve, and store for later use to obtain ink sludge-based adsorbent;

[0062] Add 11 g / L of ink-based sludge adsorbent to the sludge adsorption tank and allow it to adsorb for 65 minutes. During this time, stir the sludge adsorption tank by pumping oxygen at a rate of 2 kg O2 / m³. 3 After standing for 35 minutes, the sediment was removed by filtration, and the filtrate entered the membrane filtration tank.

[0063] S3: Catechol-modified polyethersulfone membrane filtration and detection of wastewater

[0064] Add 2.2 g / L catechol and 2.2 g / L tetraethylenepentamine to Tris buffer, stir magnetically for 35 min until completely dissolved, and let stand for 13 min to obtain catechol-based coating solution. Specifically, the Tris buffer is a 10 mM Tris-HCl buffer with a pH of 8.5.

[0065] A polyethersulfone membrane with a pore size of 0.22 μm was immersed in 1M NaOH solution for 35 min, then removed and immersed in anhydrous ethanol and sonicated for 15-25 min. Finally, it was immersed in deionized water and sonicated for 20 min. After removal, it was completely dried in an oven at 45℃ to obtain a pretreated polyethersulfone membrane.

[0066] The pretreated polyethersulfone membrane was completely immersed in the catechol-based coating solution and oscillated horizontally at 70 rpm at 24°C for 6 hours. After the reaction, the surface of the polyethersulfone membrane was rinsed with deionized water 2-3 times. Then, the polyethersulfone membrane was placed in a 65°C oven for 35 minutes and then thoroughly dried in a 45°C oven to obtain the catechol-based modified polyethersulfone membrane.

[0067] The membrane filtration tank is equipped with a catechol-modified polyethersulfone membrane. The filtrate is filtered through the catechol-modified polyethersulfone membrane. The filtered liquid enters the detection tank to test whether the heavy metal content meets the standard. If it does not meet the standard, the filtered liquid is returned to the sludge adsorption tank and the above steps are repeated. Once it meets the standard, it can be discharged.

[0068] A system for removing heavy metals from ink wastewater, which is capable of the above-mentioned process, as shown in Figure 2, includes a collection tank, a coagulation tank, a sludge adsorption tank, a membrane filtration tank, and a detection tank.

[0069] The collection tank is used to collect ink wastewater. The outlet of the collection tank is connected to the inlet of the coagulation tank. The outlet of the coagulation tank is connected to the inlet of the sludge adsorption tank. The outlet of the sludge adsorption tank is connected to the inlet of the membrane filtration tank. The outlet of the membrane filtration tank is connected to the inlet of the detection tank. The detection tank has a first outlet and a second outlet. The first outlet of the detection tank is connected to the sludge adsorption tank. The second outlet of the detection tank is used to discharge the liquid in the tank.

[0070] Example 3:

[0071] A process for removing heavy metals from ink wastewater, as shown in Figure 1, includes the following steps:

[0072] S1: Metal composite coagulant coagulates ink wastewater

[0073] The copper slag was ground through a 200-mesh sieve to obtain fine copper slag. 110 parts by weight of fine copper slag, 310 parts by weight of 15 wt% dilute sulfuric acid and 9 parts by weight of hydrogen peroxide were mixed and leached at 90°C for 3 hours. The filter residue was then removed by filtration to obtain copper slag leachate.

[0074] 70 parts by mass of TiCl4 were slowly added to 110 parts by mass of anhydrous ethanol and stirred to form a dispersion system. Then, 48 parts by mass of acetylacetone were slowly added and reacted in a water bath at 70°C for 2 hours to obtain a titanium complex solution.

[0075] Copper slag leachate and titanium complex solution were mixed at a volume ratio of 4:1, and the pH was adjusted to 3. The reaction was carried out for 2 hours, and the resulting product was aged at 64°C for 30 hours to obtain a metal composite coagulant. The copper slag was the slag produced after copper ore refining, which contained 60 wt% iron, calcium oxide, aluminum oxide, magnesium oxide, silicon dioxide and copper.

[0076] Ink wastewater is collected in a collection tank and then pumped into a coagulation tank via a vacuum pump. 0.4 g / L of metal composite coagulant is added to the coagulation tank, stirred evenly, heated to 80°C and kept at that temperature for 40 minutes, and then cooled to room temperature for mud-water separation to obtain sludge-removed wastewater and ink sludge. The ink sludge is filtered out and used to prepare ink sludge-based adsorbent, while the sludge-removed wastewater enters the sludge adsorption tank.

[0077] S2: Ink sludge-based adsorbent for adsorbing and removing sludge wastewater

[0078] Add 30 parts by mass of 1,2-dichloroethane to 16 parts by mass of ink sludge, heat in a water bath at 76°C for 40 min, then slowly add 4 parts by mass of glucose, maintain at 76°C and continue stirring for 20 min, then slowly add 20 parts by mass of 98wt% concentrated sulfuric acid, raise the temperature to 100°C, stir and react for 4 hours, cool to room temperature (25°C) and filter, wash the filter residue with deionized water until the pH of the filtrate is neutral, filter by suction, dry, grind through a 100-mesh sieve, and store for later use to obtain ink sludge-based adsorbent;

[0079] Add 12 g / L of ink sludge-based adsorbent to the sludge adsorption tank and allow it to adsorb for 70 minutes. During this time, stir the sludge adsorption tank by pumping oxygen at a rate of 2.5 kg O2 / m³. 3 After standing for 40 minutes, the sediment was removed by filtration, and the filtrate entered the membrane filtration tank.

[0080] S3: Catechol-modified polyethersulfone membrane filtration and detection of wastewater

[0081] Add 2.4 g / L catechol and 2.4 g / L tetraethylenepentamine to Tris buffer, stir magnetically for 40 min until completely dissolved, and let stand for 15 min to obtain catechol-based coating solution. Specifically, the Tris buffer is a 10 mM Tris-HCl buffer with a pH of 8.5.

[0082] A polyethersulfone membrane with a pore size of 0.22 μm was immersed in 1M NaOH solution for 40 min, then removed and immersed in anhydrous ethanol for 25 min of sonication, and finally immersed in deionized water for 25 min of sonication. After removal, it was completely dried in an oven at 40℃ to obtain a pretreated polyethersulfone membrane.

[0083] The pretreated polyethersulfone membrane was completely immersed in the catechol-based coating solution and oscillated horizontally at 80 rpm at 25°C for 8 hours. After the reaction, the surface of the polyethersulfone membrane was rinsed three times with deionized water. Then, the polyethersulfone membrane was placed in a 70°C oven for 40 minutes and then thoroughly dried in a 50°C oven to obtain the catechol-based modified polyethersulfone membrane.

[0084] The membrane filtration tank is equipped with a catechol-modified polyethersulfone membrane. The filtrate is filtered through the catechol-modified polyethersulfone membrane. The filtered liquid enters the detection tank to test whether the heavy metal content meets the standard. If it does not meet the standard, the filtered liquid is returned to the sludge adsorption tank and the above steps are repeated. Once it meets the standard, it can be discharged.

[0085] A system for removing heavy metals from ink wastewater, which is capable of the above-mentioned process, as shown in Figure 2, includes a collection tank, a coagulation tank, a sludge adsorption tank, a membrane filtration tank, and a detection tank.

[0086] The collection tank is used to collect ink wastewater. The outlet of the collection tank is connected to the inlet of the coagulation tank. The outlet of the coagulation tank is connected to the inlet of the sludge adsorption tank. The outlet of the sludge adsorption tank is connected to the inlet of the membrane filtration tank. The outlet of the membrane filtration tank is connected to the inlet of the detection tank. The detection tank has a first outlet and a second outlet. The first outlet of the detection tank is connected to the sludge adsorption tank. The second outlet of the detection tank is used to discharge the liquid in the tank.

[0087] Comparative Example 1:

[0088] Compared with Example 1, the difference of Comparative Example 1 is that the mass of titanium tetrachloride in step S1 is replaced with titanium powder, while the other steps remain unchanged. This is referred to as Comparative Example 1.

[0089] Comparative Example 2:

[0090] Compared with Example 1, Comparative Example 2 differs in that the copper slag in step S1 is replaced with titanium tetrachloride, while the other steps remain unchanged. This is referred to as Comparative Example 2.

[0091] Comparative Example 3:

[0092] Compared with Example 1, Comparative Example 3 differs in that acetylacetone is not added in step S1, and anhydrous ethanol is replaced with an equal mass of acetylacetone. The remaining steps remain unchanged, and it is referred to as Comparative Example 3.

[0093] Comparative Example 4:

[0094] Compared with Example 1, the difference of Comparative Example 4 is that 1,2-dichloroethane is not added in step S2, but is replaced with an equal mass of dichloromethane. The other steps remain the same, and it is referred to as Comparative Example 4.

[0095] Comparative Example 5:

[0096] Compared with Example 1, Comparative Example 5 differs in that glucose is not added in step S2, but is replaced with an equal mass of ink sludge, while the other steps remain unchanged. It is referred to as Comparative Example 5.

[0097] Comparative Example 6:

[0098] Compared with Example 1, Comparative Example 6 differs in that tetraethylenepentamine is not added in step S3, but is replaced with an equal mass of catechol. The remaining steps remain unchanged, and it is referred to as Comparative Example 6.

[0099] Comparative Example 7:

[0100] Compared with Example 1, Comparative Example 7 differs in that catechol is not added in step S3, but is replaced with an equal mass of tetraethylenepentamine. The remaining steps remain unchanged, and it is referred to as Comparative Example 7.

[0101] Comparative Example 8:

[0102] Compared with Example 1, Comparative Example 8 differs in that catechins are not added in step S3, but are replaced with an equal mass of polydopamine. The remaining steps remain unchanged, and it is referred to as Comparative Example 8.

[0103] The total chromium, total lead, and total mercury content of the ink wastewater from Examples 1-3 and Comparative Examples 1-8 before step S1 and the total chromium, total lead, and total mercury content of the filtered liquid entering the detection pool in step S3 were tested, and the results are shown in Table 1.

[0104] The catechin-modified polyethersulfone membranes of Examples 1-3 and Comparative Examples 6-8 were reused 10 times, and the total chromium content in the ink wastewater before and after use was measured. The results are shown in Table 2.

[0105] Table 1 (Unit: mg / L)

[0106]

[0107] Table 2 (Unit: mg / L)

[0108]

[0109] As can be seen from Table 1, the total chromium, total lead, and total mercury in Examples 1-3 decreased to 0.36-0.41 mg / L, 0.24-0.31 mg / L, and 0.027-0.038 mg / L, respectively, after the treatment process. However, the total chromium, total lead, and total mercury in Comparative Examples 1-8 were all higher than those in the Examples. This proves that copper-titanium bimetallic synergistic flocculation is the key to the efficient capture of heavy metals in the coagulation stage. 1,2-Dichloroethane and glucose together determine the number of pores and surface functional groups of the adsorbent, directly affecting the secondary adsorption effect. Furthermore, the chelation and retention of heavy metals by the catechol-tetraethylenepentamine copolymer layer is also indispensable.

[0110] As shown in Table 2, after 10 consecutive uses, the total chromium content of the catechol-modified polyethersulfone membranes in Examples 1-3 only increased from approximately 0.4 mg / L to approximately 0.6 mg / L, indicating that the catechol-tetraethylenepentamine co-modified PES membrane has excellent cycling stability and antifouling ability. In contrast, the total chromium content of the membrane in Comparative Example 6, which lacks tetraethylenepentamine, was 1.41 mg / L after the first treatment, increasing to 2.37 mg / L after 10 cycles. In Comparative Example 7, which lacks catechol, the total chromium content was already as high as 1.18 mg / L after the first treatment, increasing to 2.08 mg / L after 10 cycles. In Comparative Example 8, where catechol was replaced with polydopamine, the total chromium content was 1.13 mg / L after the first treatment, increasing to 2.04 mg / L after 10 cycles. This demonstrates that the lack of either catechol or tetraethylenepentamine reduces the chelating sites in the coating, decreases hydrophilicity, and leads to increased membrane fouling and rapid performance degradation.

[0111] It should be understood that those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims. Parts not described in detail in this specification are prior art known to those skilled in the art.

Claims

1. A process for removing heavy metals from ink wastewater, characterized in that, Specifically, the following steps are included: S1: Metal composite coagulant coagulates ink wastewater. The ink wastewater is collected in a collection tank and then pumped into a coagulation tank through a vacuum pump. 0.2-0.4 g / L of metal composite coagulant is added to the coagulation tank, stirred evenly, heated to 70-80℃ and kept at that temperature for 30-40 minutes, and then cooled to room temperature for mud-water separation to obtain desludge wastewater and ink sludge. The ink sludge is filtered out and used to prepare ink sludge-based adsorbent, while the desludge wastewater enters the sludge adsorption tank. S2: For the adsorption of sludge-based wastewater by ink sludge-based adsorbent, add 10-12 g / L of ink sludge-based adsorbent to the sludge adsorption tank and adsorb for 60-70 minutes. During this period, stir the sludge adsorption tank by pumping oxygen at a rate of 1.5-2.5 kg O2 / m³. 3 After standing for 30-40 minutes, filter to remove sediment, and the filtrate enters the membrane filtration tank; S3: Catechol-modified polyethersulfone membrane filtration and testing. The membrane filtration tank is equipped with a catechol-modified polyethersulfone membrane. The filtrate is filtered through the catechol-modified polyethersulfone membrane, and the filtered liquid enters the testing tank to test whether the heavy metal content meets the standard. If it does not meet the standard, the filtered liquid is returned to the sludge adsorption tank and the above steps are repeated. After meeting the standard, it can be discharged; The preparation method of the metal composite coagulant in step S1 specifically includes the following steps: grinding copper slag through a 200-mesh sieve to obtain fine copper slag, mixing fine copper slag, dilute sulfuric acid and 5-9 parts by weight of hydrogen peroxide, stirring and leaching at 80-90℃, then filtering to remove the filter residue to obtain copper slag leachate; slowly adding TiCl4 to anhydrous ethanol, stirring to form a dispersion system, and then slowly adding 40 -48 parts by mass of acetylacetone are reacted in a water bath at 60-70℃ to obtain a titanium complex solution; copper slag leaching solution and titanium complex solution are mixed at a volume ratio of (3-4):1, and the pH is adjusted to 2.5-3. The product obtained from the reaction is matured at 60-64℃ to obtain a metal composite coagulant; the preparation method of ink sludge-based adsorbent in step S2 specifically includes the following steps: 1,2-dichloroethane is added to ink sludge and heated in a water bath at 70-76℃. Then glucose is slowly added, and the temperature is maintained at 70-76℃ while stirring. Then concentrated sulfuric acid with a concentration of 98wt% is slowly added, the temperature is raised to 90-100℃, the reaction is stirred, and after cooling to room temperature of 23-25℃, the mixture is filtered. The filter residue is washed with deionized water until the pH of the filtrate is neutral. The residue is then filtered, dried, ground through a 100-mesh sieve, and stored for later use to obtain the ink sludge-based adsorbent.

2. The process for removing heavy metals from ink wastewater according to claim 1, characterized in that, The mixture consists of 100-110 parts by weight of fine copper slag, 300-310 parts by weight of dilute sulfuric acid, and 5-9 parts by weight of hydrogen peroxide, with a stirring leaching time of 2-3 hours; 60-70 parts by weight of TiCl4, 100-110 parts by weight of anhydrous ethanol, and 40-48 parts by weight of acetylacetone, with a water bath reaction time of 1-2 hours; the reaction time of the copper slag leaching solution and the titanium complex solution is 1-2 hours, and the aging time is 24-30 hours.

3. The process for removing heavy metals from ink wastewater according to claim 1, characterized in that, The ingredients are: 10-16 parts by weight of ink sludge, 20-30 parts by weight of 1,2-dichloroethane, heated in a water bath for 30-40 minutes, 2-4 parts by weight of glucose, stirred for 10-20 minutes, and 16-20 parts by weight of concentrated sulfuric acid, stirred for 3-4 hours.

4. The process for removing heavy metals from ink wastewater according to claim 1, characterized in that, The preparation method of the catechol-modified polyethersulfone membrane in step S3 specifically includes the following steps: Add 2-2.4 g / L catechol and 2-2.4 g / L tetraethylenepentamine to Tris buffer solution, stir magnetically for 30-40 min until completely dissolved, and let stand for 10-15 min to obtain a catechol-based coating solution; completely immerse the pretreated polyethersulfone membrane in the catechol-based coating solution, and oscillate horizontally at 60-80 rpm at room temperature of 23-25℃ for 4-8 hours. After the reaction, rinse the surface of the polyethersulfone membrane 2-3 times with deionized water, then place the polyethersulfone membrane in a 60-70℃ oven for heat treatment for 30-40 min, and then thoroughly dry it in a 40-50℃ oven to obtain the catechol-modified polyethersulfone membrane.

5. The process for removing heavy metals from ink wastewater according to claim 2, characterized in that, The concentration of dilute sulfuric acid is 10-15 wt%.

6. The process for removing heavy metals from ink wastewater according to claim 3, characterized in that, Copper slag is the slag produced after refining copper ore, which contains 30-60 wt% iron and also contains calcium oxide, aluminum oxide, magnesium oxide, silicon dioxide, and copper.

7. The process for removing heavy metals from ink wastewater according to claim 4, characterized in that, The specific steps for pretreatment of polyethersulfone membrane are as follows: immerse the polyethersulfone membrane in 1M NaOH solution for 30-40 minutes, then remove it and immerse it in anhydrous ethanol for 15-25 minutes by sonication, and finally immerse it in deionized water for 15-25 minutes by sonication. After removal, dry it completely in an oven at 40-50℃ to obtain the pretreated polyethersulfone membrane.

8. The process for removing heavy metals from ink wastewater according to claim 4, characterized in that, The Tris buffer is specifically a 10mM Tris-HCl buffer with a pH of 8.

5.

9. The process for removing heavy metals from ink wastewater according to claim 4, characterized in that, The polyethersulfone membrane has a pore size of 0.22 μm.

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