A comprehensive treatment method for printed circuit board wastewater

Abstract

The application discloses a kind of printed circuit board wastewater comprehensive treatment methods, belong to wastewater treatment technical field, in comprehensive treatment method, nickel-containing wastewater and cyanide-containing wastewater are treated, complex wastewater and silver-containing wastewater are treated, and then mixed with organic wastewater to carry out biochemical treatment.This kind of comprehensive treatment method simplifies the process of various wastewater treatment, shortens the overall processing time, and reduces the consumption of acid-base reagents by using the acid-base characteristics of water quality, reducing the cost.Under the conditions of ultraviolet and ozone bubbling, the complex is broken and oxidized, and after the oxidation of cyanide, carbonate is formed to promote the removal of metal ions by precipitation;Under the conditions of ultraviolet and air aeration, ferric chloride is added for complex breaking treatment, reducing the consumption of ferric ions, achieving efficient removal of silver and copper, and the treated water quality meets the standard, and the treatment process is efficient and fast.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of wastewater treatment, and particularly relates to a comprehensive treatment method for printed circuit board wastewater. BACKGROUND

[0002] The wastewater generated in the production process of printed circuit boards mainly includes comprehensive wastewater (pretreatment before electroplating and copper-containing wastewater), organic wastewater, ink wastewater (high COD wastewater), complex wastewater, nickel-containing wastewater, cyanide-containing wastewater and ammonia-nitrogen wastewater, etc. These wastewaters have the characteristics of complex composition and high pollution degree, and the properties of each wastewater are different. The main pollutants include Cu, Ni, EDTA complex ions, acid, alkali, chemical oxygen demand (COD) and ammonia-nitrogen, etc., which are derived from cleaning wastewater of processes such as electroplating copper, acid etching, pickling, alkaline washing, copper plating, tin plating, speed-up, stripping and hanging frame, and wastewater of processes such as exposure and development, film removal, bulkiness, deslagging, and screen washing.

[0003] Due to the multiple types and complex composition of printed circuit board wastewater, the existing treatment process is to first perform separate treatment and then perform comprehensive treatment. In the actual treatment process, due to the certain fluctuation of the daily water inflow, the impact on the system is large, especially when the concentration of heavy metal ions in the complex wastewater inflow is high and the removal effect is limited, which will cause a large impact on the microbial system of the comprehensive treatment system, so that the effluent effect cannot be guaranteed. In addition, in addition to the comprehensive treatment system, other treatment systems basically use the method of adding chemicals to remove pollutants in the wastewater, and the amount of chemicals added for adjusting the acid and alkali in each system is particularly large. At the same time, a large amount of ferrous sulfate needs to be added for the reduction of copper ions in the wastewater, and a large amount of sodium sulfide and other reagents need to be added when the effluent effect is not good, and the consumption of reagents is the main reason for the high operation cost. SUMMARY

[0004] The purpose of the present application is to provide a comprehensive treatment method for printed circuit board wastewater, which combines the characteristics of different wastewaters for comprehensive treatment, guarantees the standard discharge of effluent, and reduces the operation cost and simplifies the treatment process.

[0005] The purpose of the present application can be achieved by the following technical solutions:

[0006] The present application provides a comprehensive treatment method for printed circuit board wastewater, which combines the treatment of nickel-containing wastewater and cyanide-containing wastewater, and the treatment of complex wastewater and silver-containing wastewater, including the following steps:

[0007] S1, after the nickel-containing wastewater and the cyanide-containing wastewater are uniformly mixed, the complexation oxidation is performed under the conditions of ultraviolet and ozone bubbling, the effluent is adjusted to a pH of 9.5-11, and after the precipitation is completed, the effluent is subjected to phosphorus removal and flocculation and sedimentation treatment to obtain first-stage treated water;

[0008] Under ultraviolet irradiation, ozone is accelerated to form hydroxyl radicals, which oxidize and destroy the complexing agent in the wastewater, release nickel ions, oxidize and degrade organic pollutants, and oxidize hypophosphite and phosphite into orthophosphate, which is convenient for phosphorus removal. At the same time, ozone first converts cyanide (CN - ) is oxidized to cyanate, which is then hydrolyzed to form carbonate and nitrogen. After adjusting the pH to 9.5-11, carbonate ions and hydroxide ions under strong alkaline conditions prompt nickel ions to combine to form nickel carbonate and nickel hydroxide precipitation. Other heavy metal ions in the wastewater are simultaneously formed into hydroxide precipitation and removed. When the pH value is high, the nickel carbonate crystals are petal-shaped, with large particles and compact structure. They can adsorb the surrounding precipitates to form large precipitation polymers, accelerate the precipitation in the wastewater, and improve the precipitation effect.

[0009] S2. After the complex wastewater and silver-containing wastewater are homogeneously mixed, ferric chloride is added under ultraviolet and air aeration conditions to perform complex breaking treatment;

[0010] When ferric chloride is added under UV irradiation and air aeration, the trivalent iron in the wastewater first displaces the copper and silver ions in the complex, forming an Fe(III)-EDTA complex. Under UV irradiation, the Fe(III)-EDTA complex then undergoes a ligand-to-metal charge transfer photochemical reaction (LMCT), directly photolyzing the Fe(III)-EDTA. Simultaneously, hydroxyl radicals generated under UV aeration attack the Fe(III)-EDTA complex, indirectly photolyzing the EDTA. The photolysis products of Fe(III)-EDTA include Fe(II), CO2, and HCHO. Due to the Fe(II) / Fe(III) redox cycle in the UV irradiation and air aeration process, the Fe(II) formed by the photolysis of Fe(III)-EDTA is oxidized back to Fe(III). The reformed Fe(III) then recombines with EDTA to sustain the LMCT reaction. Under this ferric iron recycling condition, the dosage of ferric chloride is relatively low, and no harmful precipitation occurs during the process.

[0011] S3. After the chelation treatment, the pH is adjusted to 9.0-10.0. After the precipitation is complete, the effluent is subjected to flocculation and sedimentation treatment to obtain secondary treated water;

[0012] After the decomplexation treatment, the water contains ferric, ferrous, copper, and silver ions. After adjusting the pH to alkaline, copper hydroxide, ferric, and ferrous hydroxide precipitates are formed. Furthermore, due to the presence of chloride ions in the ferric chloride added to the wastewater, they combine with the silver ions to form silver chloride. At high pH values, the solubility of silver chloride decreases because the presence of hydroxide ions forms a more stable complex with the silver ions, thereby reducing the solubility of silver chloride. Since the silver chloride precipitate is small, it is difficult to precipitate completely when precipitated alone. Ferric hydroxide, on the other hand, has large flocs and strong adsorption properties, which accelerates precipitation and removes heavy metals. At this point, silver and iron precipitate together. Due to the significant differences in the properties of the two metals, subsequent separation and recovery of the precipitate is simple.

[0013] S4. After acidification and sedimentation treatment, high-concentration organic wastewater is mixed with low-concentration organic wastewater. After acidification, Fenton oxidation and flocculation and sedimentation treatment, the first-level treated water and the second-level treated water are mixed and the pH is adjusted to 5.6-6.5. After hydrolysis and acidification, it enters the IBR biochemical pool. After biochemical treatment, it flocculates and precipitates, and the effluent meets the discharge standards.

[0014] High-concentration organic wastewater mainly comes from processes such as development, film stripping, oil removal, anti-oxidation, and glue removal. The organic pollutants and ammonia nitrogen content are high, and the pH value is relatively high. The acidification precipitation treatment is to add acid to adjust the pH to 3-4, add polyferric chloride, and make the oily organic matter in the wastewater condense into large particles that can be used for solid-liquid separation. Add alkali to adjust to 9-9.5, add PAC and PAM for coagulation and flocculation precipitation. The organic matter concentration in the effluent after solid-liquid separation is reduced and can be mixed with low-concentration organic wastewater for treatment.

[0015] Low-concentration organic wastewater mainly comes from the cleaning wastewater from the development and film stripping processes. It has a high organic matter content and is alkaline. The wastewater mixed with low-concentration organic wastewater after acidification and precipitation treatment has a high organic matter content and low biodegradability. It is first treated by acidification, Fenton oxidation and flocculation precipitation, and acid is added to adjust the pH to 3.0-4.0. Hydrogen peroxide is used as an efficient oxidant and ferrous sulfate as a catalyst. Under acidic conditions, divalent iron salts decompose hydrogen peroxide to generate free hydroxyl radicals. Hydroxyl radicals have extremely strong oxidizing properties, which oxidize the organic matter in the wastewater into small molecular organic matter, carbon dioxide and water. PAC and PAM are added for flocculation and precipitation to remove heavy metals.

[0016] The primary and secondary treated water are alkaline, neutralizing the water after the initial treatment of organic wastewater and reducing the amount of alkali added. The hydrolysis and acidification effect is optimal at a pH of 5.6 to 6.5. Under the action of hydrolytic bacteria, high molecules are converted into small molecules, improving biodegradability. The IBR biochemical tank is a continuously circulating activated sludge bioreactor with anaerobic, facultative, and aerobic reactions and sedimentation, capable of efficiently removing organic matter, nitrogen, and phosphorus. After biochemical treatment, further flocculation and sedimentation are used to remove residual heavy metal ions, suspended solids, and other large particulate impurities, ensuring that the effluent meets water quality standards.

[0017] Furthermore, in step S1, the pH of the nickel-containing wastewater and the cyanide-containing wastewater is maintained at 7 to 8 when being homogeneously mixed.

[0018] In the printed circuit board manufacturing process, nickel-containing wastewater mainly comes from the nickel plating process. The nickel plating waste liquid and the first rinse water of the nickel plating process are treated as hazardous wastes, and the remaining rinse water is treated as nickel-containing wastewater for comprehensive treatment. This type of wastewater is generally acidic, COD Cr It has a high nickel value and total nickel content, and also contains complexing agents, hypophosphite and sulfite.

[0019] Cyanide-containing wastewater mainly comes from the gold plating process. The gold plating solution contains a certain amount of potassium cyanide gold. The first water wash of gold plating uses non-flowing water in the tank for rinsing. When the gold-cyanide component in the rinsing water of the tank reaches a certain concentration, it is sent to a qualified unit for disposal and gold recovery together with the cyanide-containing electroplating waste liquid. The remaining rinsing wastewater is treated as cyanide-containing wastewater for comprehensive treatment. This type of wastewater is alkaline and has a high total cyanide content. Cyanide is extremely toxic and poses a serious threat to human body and the environment.

[0020] Under acidic conditions, cyanide will form hydrocyanic acid (HCN), which is a volatile gas. In order to prevent the escape and potential harm of hydrogen cyanide, further treatment is required under alkaline conditions to maintain the pH of the mixture at 7-8, which is conducive to the treatment of cyanide. In addition, too high a pH value will consume hydroxyl radicals in the water and reduce the effect of oxidation treatment.

[0021] Furthermore, in step S1, the nickel-containing wastewater and the cyanide-containing wastewater are homogeneously mixed at a molar ratio of Ni:CN - It is 1:1~2.

[0022] When cyanide and nickel ions exist at the same time, the carbonate ions formed by oxidation treatment will form nickel carbonate precipitates with nickel ions. On the one hand, the cyanide-containing wastewater itself is alkaline, and excess cyanide can ensure that the wastewater is alkaline after mixing. On the other hand, when cyanide is excessive, the carbonate ion concentration in the water is high, which can promote the formation of nickel carbonate and further promote the precipitation and removal of heavy metals in the wastewater.

[0023] Furthermore, in step S1, the ORP control value is maintained at (+600 to +700) mV by adjusting the ozone dosage during the complex breaking oxidation.

[0024] ORP is a measure of the oxidation and reduction reaction capacity of water and is typically used to monitor and control oxidant concentrations in water. During the cyanide oxidation process, a high oxidant concentration is required to ensure the cyanide oxidation reaction. An ORP control value of 600mV or above is required to ensure complete oxidation of cyanate to carbonate and nitrogen. Furthermore, when the ORP value is greater than 500mV, ozone aqueous solution is capable of exterminating E. coli. The ORP control value should be set to ensure cyanide removal effectiveness while minimizing ozone dosage, thus controlling costs and treatment effectiveness.

[0025] Furthermore, in step S1, the duration of the complex breaking oxidation is 3 to 5 hours.

[0026] Furthermore, in step S2, the pH value of the complex wastewater and the silver-containing wastewater is maintained at 2 to 3 when they are homogeneously mixed.

[0027] In the printed circuit board (PCB) manufacturing process, complex wastewater primarily originates from the copper deposition process. This process uses a certain amount of complex copper, resulting in wastewater containing strong metal ion complexes (EDTA), making the wastewater alkaline. Silver-containing wastewater primarily originates from the electroplating and chemical silver deposition processes. During these processes, silver ions enter the wastewater system through cleaning and rinsing, making the wastewater acidic. The typical method for removing silver ions is to add sodium sulfide to form a silver sulfide precipitate. However, if sodium sulfide is exposed to air during storage, it releases toxic hydrogen sulfide gas with a rotten egg smell, which poses a threat to human health and environmental safety.

[0028] After the complex wastewater and silver-containing wastewater are mixed, the complex is broken under acidic conditions. Trivalent iron ions can better carry out LMCT reaction under acidic conditions, avoiding the formation of iron hydroxide precipitation and reducing the effect of replacing heavy metal ions. The formation of trivalent iron precipitation will destroy the Fe(II) / Fe(III) redox cycle, resulting in the need to add more ferric chloride. Acidic conditions can not only promote the complex breaking effect, but also reduce drug consumption.

[0029] Furthermore, in step S2, the amount of ferric chloride added is 5-10% of the molar amount of the complexing agent EDTA in the mixed wastewater.

[0030] Due to the Fe(II) / Fe(III) redox cycle in the UV and air aeration process, the actual amount of ferric chloride required is relatively low, and ferric iron can be recycled during the process. Too little ferric chloride can reduce complex breaking efficiency. Choosing the optimal dosage can ensure complex breaking and minimize resource waste.

[0031] Furthermore, in step S2, the ORP control value in the water is maintained at (+100 to +200) mV during the air aeration.

[0032] Under ultraviolet aeration conditions, it is necessary to maintain a high oxidation level in the wastewater to promote the generation of hydroxyl radicals and indirectly photolyze EDTA.

[0033] Furthermore, in step S2, the duration of the network breaking treatment is 0.5 to 1 hour.

[0034] Furthermore, the total nickel content in the primary treated water is <0.1 mg / L, the total cyanide content is <0.2 mg / L, and the total phosphorus content is <0.5 mg / L; the total silver content in the secondary treated water is <0.1 mg / L, and the total copper content is <0.3 mg / L.

[0035] Beneficial effects of the present invention:

[0036] (1) The present invention combines the treatment of various types of wastewater generated during the production of printed circuit boards based on their characteristics. Nickel-containing wastewater and cyanide-containing wastewater are combined for treatment, and complex wastewater and silver-containing wastewater are combined for treatment. The wastewater is then subjected to deep biochemical treatment with organic wastewater. This comprehensive treatment method simplifies the process of separate treatment of various types of wastewater, shortens the overall treatment time, and utilizes the acidity and alkalinity characteristics of water to reduce the consumption of acid and alkali reagents and reduce costs.

[0037] (2) When nickel-containing wastewater and cyanide-containing wastewater are treated together in the present invention, ultraviolet and ozone bubbling conditions are used to perform decomposition oxidation, and cyanide is oxidized to form carbonate to generate nickel carbonate precipitate. Compared with nickel hydroxide, its solubility in water is lower and the nickel ion removal effect is better. In addition, the large-particle nickel carbonate precipitate can promote the precipitation of other precipitates, accelerate the precipitation rate, and improve the precipitation effect.

[0038] (3) In the present invention, the complex wastewater and the silver-containing wastewater are treated together, and ferric chloride is added under ultraviolet and air aeration conditions to perform complex breaking treatment, forming an Fe(II) / Fe(III) redox cycle, while reducing the trivalent iron consumption while replacing the copper ions and silver ions in the complex, playing a complex breaking role. The chloride ions introduced by the added ferric chloride can combine with silver ions to form a precipitate under alkaline conditions, and the synchronously precipitated ferric hydroxide can accelerate the precipitation of copper hydroxide and silver chloride precipitation, thereby achieving efficient removal of silver and copper.

[0039] (4) The present invention uses a combination of ultraviolet and ozone / air aeration to oxidize wastewater. Compared with the traditional method of adding strong oxidants, no toxic by-products are produced, and the treatment process is efficient and fast. DETAILED DESCRIPTION

[0040] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0041] The water quality of the influent in the examples of the present invention and the comparative examples is shown in Table 1:

[0042] Table 1

[0043]

[0044] Example 1

[0045] This embodiment provides a comprehensive treatment method for printed circuit board wastewater, which combines nickel-containing wastewater and cyanide-containing wastewater for treatment, and combines complexing wastewater and silver-containing wastewater for treatment, including the following steps:

[0046] S1, nickel-containing wastewater and cyanide-containing wastewater are homogenized in a homogenization tank according to the molar ratio of Ni:CN - The mixture was homogeneously mixed in a ratio of 1:1, and the pH was maintained at 7-8 by adding sodium hydroxide. After mixing, the wastewater entered the oxidation tank and was irradiated with ultraviolet light while bubbling ozone. The ORP control value in the wastewater was maintained at +600mV by adjusting the ozone dosage, and the complex breaking oxidation was continued for 3 hours. After completion, the effluent entered the regulating tank and sodium hydroxide was added to adjust the pH to 9.5-11. The precipitation reaction was continued for 3 hours. The supernatant was used as the effluent and entered the phosphorus removal tank. 300mg / L of lime milk was added to the phosphorus removal tank to remove phosphorus. The effluent entered the callback tank and acid was added to adjust the pH to 6-7. It entered the coagulation tank and 1.0g / L of PAC was added. It then entered the flocculation tank and 0.5g / L of PAM was added. After sedimentation in the sedimentation tank, the effluent was the primary treated water. The water quality test results were: total nickel content = 0.072mg / L, total cyanide content = 0.123mg / L, and total phosphorus content = 0.284mg / L.

[0047] S2. The complex wastewater and silver-containing wastewater are mixed in equal volumes in a homogenization tank, sulfuric acid is added to maintain the pH at 2-3, and then enter the oxidation tank. Ferric chloride is added under ultraviolet irradiation and air aeration conditions. The amount of ferric chloride added is 5% of the molar amount of the complexing agent EDTA in the mixed wastewater. The ORP control value in the water is maintained at 100mV, and the complex breaking treatment is continued for 0.5h.

[0048] S3, the effluent after the breaking of the complex enters a reaction sedimentation tank, and is adjusted to pH 9.0-10.0 by adding alkali, and is continuously precipitated for 3 hours, the supernatant of the precipitation enters a flocculation sedimentation tank, and is treated by flocculation precipitation by adding 0.5 g / L PAM to obtain secondary treatment water, and the result of detecting the water quality is: total silver content = 0.085 mg / L, total copper content = 0.246 mg / L;

[0049] S4, the high-concentration organic wastewater enters an acidification tank to be adjusted to pH 3-4 by adding sulfuric acid, and then enters a sedimentation tank, and 1.5 g / L polymeric ferric chloride is added, and the organic matters in the sedimentation tank form large-particle suspended matters to precipitate, and the effluent enters a readjustment tank to be adjusted to pH 9-9.5 by adding sodium hydroxide, and is transported to a coagulation tank to add 0.5 g / L PAC, and then enters a flocculation tank to add 0.1 g / L PAM, and is treated by flocculation precipitation in a sedimentation tank to remove suspended matters, and divalent copper forms copper hydroxide precipitation to be removed, and the effluent is mixed with the low-concentration organic wastewater in equal volume to enter an acidification tank to be adjusted to pH 3.0-4.0 by adding sulfuric acid, and enters a Fenton oxidation tank to be treated by Fenton oxidation by adding hydrogen peroxide and ferrous sulfate, the concentration of the hydrogen peroxide is 30%, the molar ratio of the hydrogen peroxide to the ferrous sulfate is 3:1, and the hydrogen peroxide is added in equal mass according to the content of COD in the wastewater, and the treated effluent enters a flocculation sedimentation tank to be treated by flocculation precipitation by adding 0.5 g / L PAC and 0.3 g / L PAM, and the effluent is mixed with the primary treatment water and the secondary treatment water and is adjusted to pH 5.6-6.5, the volume ratio of the primary treatment water:the secondary treatment water:the organic wastewater = 1:2:6, and enters a hydrolysis acidification tank to be treated by hydrolysis acidification, the BOD5 / COD ratio of the effluent is controlled to be 0.4, and after the treatment, enters an IBR biochemical tank, and after the biochemical treatment, 0.3 g / L PAM is added to be treated by flocculation precipitation, and the effluent can be discharged up to the standard, and the result of detecting the water quality is shown in Table 2.

[0050] Table 2

[0051]

[0052] Example 2

[0053] The difference from Example 1 is that the molar ratio of Ni:CN in step S1 is 1:1.8. - The other conditions and steps are the same as those in Example 1. At this time, the result of detecting the water quality of the primary treatment water is: total nickel content = 0.025 mg / L, total cyanide content = 0.141 mg / L, and total phosphorus content = 0.336 mg / L. The water quality of the secondary treatment water is the same as that in Example 1.

[0054] The result of detecting the water quality of the comprehensive treatment effluent is shown in Table 3.

[0055] Table 3

[0056]

[0057] Example 3

[0058] The only difference from Example 1 is that the molar ratio of Ni:CN in step S1 is - The ratio of the primary treated water to the secondary treated water was 1:2, and the other conditions and steps were the same as in Example 1. The results of the water quality test of the primary treated water at this time were: total nickel content = 0.018 mg / L, total cyanide content = 0.196 mg / L, and total phosphorus content = 0.485 mg / L. The water quality of the secondary treated water was the same as in Example 1.

[0059] The test results of the comprehensive treatment effluent quality are shown in Table 4:

[0060] Table 4

[0061]

[0062] Example 4

[0063] The only difference from Example 2 was that in step S1, the ORP control value was set at 650 mV, and the complex-breaking oxidation was continued for 4 hours. Other conditions and steps were the same as in Example 2. The water quality of the primary treated water at this time was tested: total nickel content = 0.022 mg / L, total cyanide content = 0.105 mg / L, and total phosphorus content = 0.154 mg / L. The water quality of the secondary treated water was the same as in Example 1.

[0064] The test results of the comprehensive treatment effluent water quality are shown in Table 5:

[0065] Table 5

[0066]

[0067] Example 5

[0068] The only difference from Example 2 was that in step S1, the ORP control value was set at 700 mV, and the complex-breaking oxidation was continued for 5 hours. Other conditions and steps were the same as in Example 2. The water quality of the primary treated water at this time was tested: total nickel content = 0.021 mg / L, total cyanide content = 0.099 mg / L, and total phosphorus content = 0.146 mg / L. The water quality of the secondary treated water was the same as in Example 1.

[0069] The test results of the comprehensive treatment effluent water quality are shown in Table 6:

[0070] Table 6

[0071]

[0072]

[0073] Example 6

[0074] The only difference from Example 5 is that in step S2, the amount of ferric chloride added is 8% of the molar amount of the complexing agent EDTA in the mixed wastewater. Other conditions and steps are the same as in Example 5. The water quality test results of the secondary treated water at this time are: total silver content = 0.061 mg / L, total copper content = 0.152 mg / L. The water quality of the primary treated water is the same as in Example 5.

[0075] The test results of the comprehensive treatment effluent quality are shown in Table 7:

[0076] Table 7

[0077]

[0078] Example 7

[0079] The only difference from Example 5 is that in step S2, the amount of ferric chloride added is 10% of the molar amount of the complexing agent EDTA in the mixed wastewater. Other conditions and steps are the same as in Example 5. The water quality test results of the secondary treated water at this time are: total silver content = 0.058 mg / L, total copper content = 0.149 mg / L. The water quality of the primary treated water is the same as in Example 5.

[0080] The test results of the comprehensive treatment effluent water quality are shown in Table 8:

[0081] Table 8

[0082]

[0083] Example 8

[0084] The only difference from Example 6 was that in step S2, the ORP control value was 150 mV and the chelation breaking treatment was continued for 0.8 h. Other conditions and steps were the same as in Example 5. The water quality of the secondary treated water at this time was tested: total silver content = 0.055 mg / L, total copper content = 0.127 mg / L. The water quality of the primary treated water was the same as in Example 6.

[0085] The test results of the comprehensive treatment effluent water quality are shown in Table 9:

[0086] Table 9

[0087]

[0088] Example 9

[0089] The only difference from Example 6 was that in step S2, the ORP control value was set to 200 mV and the chelation breaking treatment was continued for 1 hour. Other conditions and steps were the same as in Example 5. The water quality of the secondary treated water was tested: total silver content = 0.053 mg / L, total copper content = 0.119 mg / L. The water quality of the primary treated water was the same as in Example 6.

[0090] The test results of the comprehensive treatment effluent water quality are shown in Table 10:

[0091] Table 10

[0092]

[0093] Comparative Example 1

[0094] Compared with Example 1, the difference of this comparative example is that when nickel wastewater and cyanide-containing wastewater are treated together, alkaline chlorination is used instead of ultraviolet ozone method for treatment. The specific treatment steps are as follows:

[0095] S1, nickel-containing wastewater and cyanide-containing wastewater are homogenized in a homogenization tank according to the molar ratio of Ni:CN - The mixture is homogeneously mixed in a ratio of 1:1, and the pH is maintained at 10-11 by adding sodium hydroxide. After mixing, the wastewater enters the primary oxidation tank, and sodium hypochlorite is added. The ORP control value in the wastewater is maintained at 300mV by adjusting the amount of sodium hypochlorite added. The oxidation is continued for 1 hour to break the complex. After completion, the effluent enters the regulating tank and sulfuric acid is added to adjust the pH to 6.5-7. It enters the secondary oxidation tank and sodium hypochlorite is added. The ORP control value in the wastewater is maintained at 650mV by adjusting the amount of sodium hypochlorite added. The oxidation is continued for 1 hour to break the complex. The effluent enters the regulating tank and sodium hydroxide is added. The pH was adjusted to 9.5-11, and the precipitation reaction was continued for 3 hours. The supernatant was used as the effluent and entered the dephosphorization tank. 300 mg / L of lime milk was added to the dephosphorization tank to remove phosphorus. The effluent entered the adjustment tank, and acid was added to adjust the pH to 6-7. The effluent entered the coagulation tank, and 1.0 g / L of PAC was added. The effluent then entered the flocculation tank and 0.5 g / L of PAM was added. The effluent entered the sedimentation tank and after sedimentation, it became primary treated water. The water quality test results were: total nickel content = 0.165 mg / L, total cyanide content = 0.214 mg / L, and total phosphorus content = 0.526 mg / L.

[0096] S2. The complex wastewater and silver-containing wastewater are mixed in equal volumes in a homogenization tank, sulfuric acid is added to maintain the pH at 2-3, and then enter the oxidation tank. Ferric chloride is added under ultraviolet irradiation and air aeration conditions. The amount of ferric chloride added is 5% of the molar amount of the complexing agent EDTA in the mixed wastewater. The ORP control value in the water is maintained at 100mV, and the complex breaking treatment is continued for 0.5h.

[0097] S3, after the chelation treatment, the effluent enters the reaction sedimentation tank, alkali is added to adjust the pH to 9.0-10.0, and precipitation is continued for 3 hours. The supernatant of the precipitation enters the flocculation sedimentation tank, and 0.5g / L PAM is added for flocculation precipitation to obtain secondary treated water. The results of water quality testing are: total silver content = 0.085mg / L, total copper content = 0.246mg / L;

[0098] S4, high concentration organic wastewater into the acidification tank with sulfuric acid to adjust the pH to 3-4, and then into the sedimentation tank, adding 1.5 g / L of polymeric ferric chloride, the organic matter in the sedimentation tank forms large particles of suspended matter, the effluent enters the back tank, adding sodium hydroxide to adjust the pH to 9-9.5, and then into the coagulation tank adding 0.5 g / L of PAC, and then into the flocculation tank adding 0.1 g / L of PAM, and then into the sedimentation tank for flocculation and sedimentation to remove suspended solids, and divalent copper forms copper hydroxide precipitate to remove, the effluent is mixed with low concentration organic wastewater in equal volume, and then into the acidification tank, adding sulfuric acid to adjust the pH to 3.0-4.0, and then into the Fenton oxidation tank adding hydrogen peroxide and ferrous sulfate for Fenton oxidation treatment, the concentration of hydrogen peroxide is 30%, the molar ratio of hydrogen peroxide to ferrous sulfate is 3:1, and the dosage of hydrogen peroxide is added in equal mass according to the COD content in the wastewater, the treated effluent enters the flocculation and sedimentation tank, adding 0.5 g / L of PAC and 0.3 g / L of PAM for flocculation and sedimentation treatment, the effluent is mixed with the first-stage treated water and the second-stage treated water and adjusted to a pH of 5.6-6.5, the volume ratio of first-stage treated water: second-stage treated water: organic wastewater = 1:2:6, and then into the hydrolysis acidification tank for hydrolysis acidification treatment, controlling the BOD5 / COD ratio of the effluent to be 0.4, and then into the IBR biochemical tank for biochemical treatment, adding 0.3 g / L of PAM for flocculation and sedimentation after biochemical treatment, and the water quality test results of the effluent are shown in Table 11.

[0099] Table 11

[0100]

[0101] Comparative Example 2

[0102] Compared with Example 1, the difference of the present comparative example is that when the complex wastewater and silver-containing wastewater are combined for treatment, ferrous sulfate is directly added instead of ultraviolet air aeration method for treatment, and the specific treatment steps are as follows:

[0103] S1, the nickel-containing wastewater and cyanide-containing wastewater are mixed in the homogenizing tank according to the molar ratio Ni: CN -The homogeneous mixing is carried out at 1:1, the pH is maintained at 7-8 by adding sodium hydroxide, after mixing, the wastewater enters the oxidation tank, ozone bubbling is carried out at the same time of ultraviolet irradiation, the ORP control value in the wastewater is maintained at +600mV by adjusting the ozone dosage, the breakage oxidation is carried out for 3h, after completion, the effluent enters the adjusting tank, the pH is adjusted to 9.5-11 by adding sodium hydroxide, the precipitation reaction is carried out for 3h, the supernatant is used as the effluent to enter the phosphorus removal tank, 300mg / L of lime milk is added to remove phosphorus in the phosphorus removal tank, the effluent enters the readjusting tank, the pH is adjusted to 6-7 by adding acid, enters the coagulation tank, 1.0g / L of PAC is added, then enters the flocculation tank, 0.5g / L of PAM is added, after entering the sedimentation tank, the effluent is the first-stage treated water, the water quality detection result is: total nickel content=0.072mg / L, total cyanide content=0.123mg / L, total phosphorus content=0.284mg / L.

[0104] S2, the complex wastewater and the silver-containing wastewater are mixed in equal volume in the homogeneous tank, sulfuric acid is added to maintain the pH at 2-3, after mixing, the wastewater enters the oxidation tank, ferrous sulfate is added, the ferrous sulfate dosage is 5% of the molar amount of the complexing agent EDTA in the mixed wastewater, the ORP control value in the water is maintained at 100mV, the breakage treatment is carried out for 0.5h.

[0105] S3, the effluent after the breakage treatment enters the reaction precipitation tank, the pH is adjusted to 9.0-10.0 by adding alkali, the precipitation is carried out for 3h, the supernatant of the precipitation enters the flocculation and precipitation tank, 0.5g / L of PAM is added to carry out the flocculation and precipitation treatment to obtain the second-stage treated water, the water quality detection result is: total silver content=0.168mg / L, total copper content=0.679mg / L;

[0106] S4, high concentration organic wastewater enters the acidification tank and adds sulfuric acid to adjust the pH to 3-4, then enters the sedimentation tank, adds 1.5g / L of polyferric chloride, and the organic matter in the sedimentation tank forms large particles of suspended solids and precipitates. The effluent enters the callback tank, adds sodium hydroxide to adjust the pH to 9-~9.5, and is transported to the coagulation tank to add 0.5g / L of PAC. Then it enters the flocculation tank and adds 0.1g / L of PAM. After entering the sedimentation tank for flocculation and precipitation, the suspended solids are removed. Divalent copper forms copper hydroxide precipitation and is removed. The effluent is mixed with low concentration organic wastewater in equal volumes and enters the acidification tank. Sulfuric acid is added to adjust the pH to 3.0-4.0. It enters the Fenton oxidation tank and adds hydrogen peroxide and ferrous sulfate for Fenton oxidation treatment. The concentration of hydrogen peroxide is 30%. The molar ratio of hydrogen peroxide and ferrous sulfate is 3:1. The amount of hydrogen peroxide added is equal to the COD content in the wastewater. The treated effluent enters the flocculation sedimentation tank, and 0.5g / L PAC and 0.3g / L PAM are added for flocculation and sedimentation treatment. The effluent is mixed with the first-level treated water and the second-level treated water and the pH is adjusted to 5.6-6.5. The volume ratio of first-level treated water: second-level treated water: organic wastewater is 1:2:6. The effluent enters the hydrolysis and acidification tank for hydrolysis and acidification treatment. The BOD5 / COD ratio of the effluent is controlled at 0.4. After treatment, the effluent enters the IBR biochemical tank. After biochemical treatment, 0.3g / L PAM is added for flocculation and sedimentation. The effluent can meet the discharge standards. The water quality test results are shown in Table 12.

[0107] Table 12

[0108]

[0109] Comparative Example 3

[0110] Compared with Example 1, the difference of this comparative example is that when nickel wastewater and cyanide-containing wastewater are treated together, alkaline chlorination is used instead of ultraviolet ozone method for treatment, and when complex wastewater and silver-containing wastewater are treated together, ferrous sulfate is directly added to replace ultraviolet air aeration method for treatment. The specific treatment steps are as follows:

[0111] S1, nickel-containing wastewater and cyanide-containing wastewater are homogenized in a homogenization tank according to the molar ratio of Ni:CN -The mixture is homogeneously mixed in a ratio of 1:1, and the pH is maintained at 10-11 by adding sodium hydroxide. After mixing, the wastewater enters the primary oxidation tank, and sodium hypochlorite is added. The ORP control value in the wastewater is maintained at 300mV by adjusting the amount of sodium hypochlorite added. The oxidation is continued for 1 hour to break the complex. After completion, the effluent enters the regulating tank and sulfuric acid is added to adjust the pH to 6.5-7. It enters the secondary oxidation tank and sodium hypochlorite is added. The ORP control value in the wastewater is maintained at 650mV by adjusting the amount of sodium hypochlorite added. The oxidation is continued for 1 hour to break the complex. The effluent enters the regulating tank and sodium hydroxide is added to adjust the pH. The pH value was set at 9.5-11, and the precipitation reaction was continued for 3 hours. The supernatant was used as the effluent and entered the dephosphorization tank. 300 mg / L of lime milk was added to the dephosphorization tank to remove phosphorus. The effluent entered the adjustment tank and acid was added to adjust the pH value to 6-7. The effluent entered the coagulation tank and 1.0 g / L of PAC was added. The effluent then entered the flocculation tank and 0.5 g / L of PAM was added. The effluent entered the sedimentation tank and the sedimentation was precipitated as primary treated water. The water quality test results were as follows: total nickel content = 0.165 mg / L, total cyanide content = 0.214 mg / L, and total phosphorus content = 0.526 mg / L.

[0112] S2. The complex wastewater and silver-containing wastewater are mixed in equal volumes in a homogenizing tank, sulfuric acid is added to maintain the pH at 2-3, and then enter the oxidation tank. Ferrous sulfate is added. The amount of ferrous sulfate added is 5% of the molar amount of the complexing agent EDTA in the mixed wastewater. The ORP control value in the water is maintained at 100mV, and the complex breaking treatment is continued for 0.5h.

[0113] S3, after the chelation treatment, the effluent enters the reaction sedimentation tank, alkali is added to adjust the pH to 9.0-10.0, and precipitation is continued for 3 hours. The supernatant of the precipitation enters the flocculation sedimentation tank, and 0.5g / L PAM is added for flocculation precipitation to obtain secondary treated water. The results of water quality testing are: total silver content = 0.085mg / L, total copper content = 0.246mg / L;

[0114] S4, high concentration organic wastewater enters the acidification tank and adds sulfuric acid to adjust the pH to 3-4, then enters the sedimentation tank, adds 1.5g / L of polyferric chloride, and the organic matter in the sedimentation tank forms large particles of suspended solids and precipitates. The effluent enters the callback tank, adds sodium hydroxide to adjust the pH to 9-9.5, and is transported to the coagulation tank to add 0.5g / L of PAC. Then it enters the flocculation tank and adds 0.1g / L of PAM. After entering the sedimentation tank, flocculation and precipitation are carried out to remove suspended solids. Divalent copper forms copper hydroxide precipitation and is removed. The effluent is mixed with low concentration organic wastewater in equal volumes and enters the acidification tank. Sulfuric acid is added to adjust the pH to 3.0-4.0. It enters the Fenton oxidation tank and adds hydrogen peroxide and ferrous sulfate for Fenton oxidation treatment. The hydrogen peroxide concentration is 3 0%, the molar ratio of hydrogen peroxide and ferrous sulfate is 3:1, the amount of hydrogen peroxide added is added in equal mass according to the COD content in the wastewater, the treated effluent enters the flocculation sedimentation tank, 0.5g / L PAC and 0.3g / L PAM are added for flocculation sedimentation treatment, the effluent is mixed with the first-level treated water and the second-level treated water and the pH is adjusted to 5.6-6.5, the volume ratio of first-level treated water: second-level treated water: organic wastewater = 1:2:6, and enters the hydrolysis acidification tank for hydrolysis acidification treatment, and the BOD5 / COD ratio of the effluent is controlled to 0.4. After treatment, it enters the IBR biochemical tank, and 0.3g / L PAM is added after biochemical treatment for flocculation sedimentation. The effluent water quality test results are shown in Table 13.

[0115] Table 13

[0116]

[0117] As shown in the above-mentioned water quality test results, when increasing nickel-containing wastewater and cyanide-containing wastewater mixing in embodiment 1-embodiment 3, the proportion of cyanide, cyanide appropriately increases.It is conducive to forming carbonate, promotes the formation of nickel carbonate precipitation, and the removal rate of total nickel increases, but when cyanide is too much, due to ultraviolet ozone oxidation limit, causes partial cyanide to be incompletely oxidized, total cyanide content can rise, and in embodiment 4 and embodiment 5, on the basis of embodiment 2, improve ORP control value, the oxidizing power of system is enhanced, now compared to embodiment 2 its total cyanide content obviously declines.Example 6 and embodiment 7 are directed to the broken network treatment of complex wastewater and silver-containing wastewater and increase the dosage of ferric iron, and its broken network effect can enhance, and the removal effect of copper is better, and in embodiment 9, when complex wastewater and silver-containing wastewater are processed, ORP control value is 200mV, and the total copper content in its secondary treated water is low to 0.119mg / L, and treatment effect is best. Based on the commonly used cyanide breaking and complex breaking methods in the prior art, Comparative Example 1 and Comparative Example 2 respectively replaced the methods by alkaline chlorination and direct addition of ferrous sulfate. The results showed that the treatment effects in Comparative Example 1 and Comparative Example 2 were significantly inferior to those in Example 1. In Comparative Example 3, due to the simultaneous replacement of the two methods, the concentration of heavy metal ions increased during biochemical treatment, which had an impact on the microbial treatment process. The water quality in the embodiment met the requirements of the "GB 39731-2020 Electronic Industry Water Pollutant Discharge Standard", while the water quality in Comparative Example 3 did not meet the standards.

[0118] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus.

[0119] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A comprehensive treatment method for printed circuit board wastewater, characterized in that: The nickel-containing wastewater and the cyanide-containing wastewater are treated together, and the complex wastewater and the silver-containing wastewater are treated together, including the following steps: S1. After the nickel-containing wastewater and the cyanide-containing wastewater are homogeneously mixed, the chelation oxidation is carried out under ultraviolet and ozone bubbling conditions. The pH of the effluent is adjusted to 9.5-11. After the precipitation is complete, the effluent is subjected to phosphorus removal and flocculation precipitation treatment to obtain primary treated water; S2. After the complex wastewater and silver-containing wastewater are homogeneously mixed, ferric chloride is added under ultraviolet and air aeration conditions to perform complex breaking treatment; S3. After the chelation treatment, the pH is adjusted to 9.0-10.

0. After the precipitation is complete, the effluent is subjected to flocculation and sedimentation treatment to obtain secondary treated water; S4. After acidification and sedimentation treatment, high-concentration organic wastewater is mixed with low-concentration organic wastewater. After acidification, Fenton oxidation and flocculation and sedimentation treatment, the first-level treated water and the second-level treated water are mixed and the pH is adjusted to 5.6-6.

5. After hydrolysis and acidification, it enters the IBR biochemical pool. After biochemical treatment, it flocculates and precipitates, and the effluent meets the discharge standards.

2. A comprehensive treatment method for printed circuit board wastewater according to claim 1, characterized in that: In step S1, the pH value of the nickel-containing wastewater and the cyanide-containing wastewater is maintained at 7-8 when they are homogeneously mixed.

3. A comprehensive treatment method for printed circuit board wastewater according to claim 1, characterized in that: In step S1, the nickel-containing wastewater and the cyanide-containing wastewater are homogeneously mixed at a molar ratio of Ni:CN - It is 1:1~2.

4. A comprehensive treatment method for printed circuit board wastewater according to claim 1, characterized in that: In step S1, the ORP control value is maintained at (+600 to +700) mV by adjusting the ozone dosage during the complex breaking oxidation.

5. The method for comprehensive treatment of printed circuit board wastewater according to claim 1, characterized in that: In step S1, the duration of the complex breaking oxidation is 3 to 5 hours.

6. A comprehensive treatment method for printed circuit board wastewater according to claim 1, characterized in that: In step S2, the complex wastewater and the silver-containing wastewater are homogeneously mixed while maintaining a pH of 2 to 3.

7. The method for comprehensive treatment of printed circuit board wastewater according to claim 1, characterized in that: In step S2, the amount of ferric chloride added is 5-10% of the molar amount of the complexing agent EDTA in the mixed wastewater.

8. The method for comprehensive treatment of printed circuit board wastewater according to claim 1, characterized in that: In step S2, the ORP control value in the water is maintained at (+100 to +200) mV during the air aeration.

9. The method for comprehensive treatment of printed circuit board wastewater according to claim 1, characterized in that: In step S2, the duration of the network breaking treatment is 0.5 to 1 hour.

10. The method for comprehensive treatment of printed circuit board wastewater according to claim 1, characterized in that: The total nickel content in the primary treated water is <0.1 mg / L, the total cyanide content is <0.2 mg / L, and the total phosphorus content is <0.5 mg / L; the total silver content in the secondary treated water is <0.1 mg / L, and the total copper content is <0.3 mg / L.

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