Printed circuit board wastewater comprehensive treatment method

Abstract

The invention discloses a printed circuit board wastewater comprehensive treatment method, and belongs to the technical field of wastewater treatment.The comprehensive treatment method comprises the steps that nickel-containing wastewater and cyanide-containing wastewater are treated in a combined mode, complex wastewater and silver-containing wastewater are treated in a combined mode, and then the wastewater is mixed with organic wastewater for biochemical treatment. According to the comprehensive treatment method, the process of quality-divided treatment of various types of wastewater is simplified, the overall treatment time is shortened, the acid-base property of water is utilized, the consumption of acid-base agents is reduced, and the cost is reduced. Ultraviolet and ozone bubbling conditions are utilized to perform complex breaking oxidation, cyanide is utilized to oxidize to form carbonate, and precipitation is promoted to remove metal ions; ferric chloride is added for complex breaking treatment under ultraviolet and air aeration conditions, so that the consumption of ferric iron is reduced, silver and copper are efficiently removed, the quality of comprehensively treated effluent reaches the standard, and the treatment process is efficient and rapid.

Description

Technical Field

[0001] The invention belongs to the technical field of wastewater treatment, and in particular relates to a comprehensive treatment method for printed circuit board wastewater. Background Art

[0002] The wastewater generated in the production process of printed circuit boards mainly includes comprehensive wastewater (electroplating pretreatment and copper-containing wastewater), organic wastewater, ink wastewater (high COD wastewater), complex wastewater, nickel-containing wastewater, cyanide-containing wastewater and ammonia nitrogen wastewater. These wastewaters are characterized by complex components and high pollution levels, and the properties of each wastewater are different. The main pollutants include Cu, Ni, EDTA complex ions, acids, alkalis, chemical oxygen demand (COD) and ammonia nitrogen, etc., which come from the cleaning wastewater of electroplating copper, acid etching, pickling, alkali washing, copper plating, tin plating, speeding, stripping racks and other processes, as well as the wastewater of exposure and development, film stripping, bulking, desmearing, screen washing and other processes.

[0003] Due to the variety and complex composition of printed circuit board wastewater, the existing treatment processes are to first conduct quality-based treatment and then comprehensive treatment. In the actual treatment process, due to the certain volatility of daily water inflow, the impact on the system is relatively large, especially when the concentration of heavy metal ions in the complex wastewater inflow is high and the removal effect is limited, it will cause a large impact on the microbial system of the comprehensive treatment system, making the water output effect cannot be guaranteed. In addition, except for the comprehensive treatment system, other treatment systems basically remove pollutants in wastewater by adding drugs, and the amount of drugs added for acid-base regulation in each system is particularly large. At the same time, the reduction of copper ions in wastewater requires the addition of a large amount of ferrous sulfate. When the water output effect is not good, a large amount of sodium sulfide and other agents need to be added. The consumption of agents is the main reason for the high operating cost. Summary of the invention

[0004] The purpose of the present invention is to provide a comprehensive treatment method for printed circuit board wastewater, which combines the characteristics of different wastewaters for comprehensive treatment, ensures that the effluent meets the discharge standards, reduces operating costs, and simplifies the treatment process.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

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

[0007] S1. After the nickel-containing wastewater and the cyanide-containing wastewater are homogenously mixed, the chelation-breaking oxidation is carried out under ultraviolet and ozone bubbling conditions, and 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;

[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 to orthophosphate, which is convenient for phosphorus removal. At the same time, ozone first converts cyanide (CN - ) is oxidized to cyanate, and cyanate is 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 the silver-containing wastewater are homogeneously mixed, ferric chloride is added under ultraviolet and air aeration conditions to carry out complex breaking treatment;

[0010] Under ultraviolet irradiation and air aeration conditions, ferric chloride is added. First, the trivalent iron in the wastewater will replace the copper ions and silver ions in the complex to form a Fe(III)-EDTA complex. At this time, under ultraviolet irradiation, the Fe(III)-EDTA complex will undergo a ligand-to-metal charge transfer photochemical reaction (LMCT), directly photolyzing the Fe(III)-EDTA. At the same time, the hydroxyl radicals generated under ultraviolet aeration conditions will attack the Fe(III)-EDTA complex and indirectly photolyze EDTA. The photolysis products of Fe(III)-EDTA include Fe(II), CO 2 and HCHO, etc. Due to the Fe(II) / Fe(III) redox cycle in the UV irradiation and air aeration process, Fe(II) formed by photolysis of Fe(III)-EDTA is oxidized back to Fe(III), and the reformed Fe(III) is recombined with EDTA to maintain the LMCT reaction. Under this ferric iron recycling condition, the amount of ferric chloride added is less, and there is no harmful precipitation in the process.

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

[0012] After the decomplexation treatment, there are trivalent iron ions, divalent iron ions, copper ions and silver ions in the water. After adjusting the pH to alkaline, copper hydroxide precipitates, ferric hydroxide precipitates and ferrous hydroxide precipitates are formed. At the same time, due to the presence of chloride ions in the ferric chloride added to the wastewater, it will combine with silver ions to form silver chloride. Under high pH conditions, the solubility of silver chloride will decrease because the presence of hydroxide ions will form a more stable complex with silver ions, thereby reducing the solubility of silver chloride. Since the silver chloride precipitate particles are small, it is difficult to precipitate completely when precipitated alone. The alum flowers of ferric hydroxide are large and have strong adsorption, which can accelerate precipitation and remove heavy metals. At this time, silver and iron are precipitated together. Based on the large difference in the characteristics of the two metals, the 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 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, oxidation prevention, 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 to condense the oily organic matter in the wastewater 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, and the organic concentration in the effluent after solid-liquid separation is reduced, which 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 content and is alkaline. The wastewater mixed with low-concentration organic wastewater after acidification and precipitation treatment has a high organic 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 a high-efficiency 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 treated water and the secondary treated water are alkaline, which can neutralize the water after the initial treatment of organic wastewater and reduce the amount of alkali added. The hydrolysis and acidification effect is best when the pH is 5.6-6.5. Under the action of hydrolytic bacteria, high molecules are converted into small molecules, improving biodegradability. The IBR biochemical pool is a cyclic activated sludge bioreactor that integrates anaerobic, facultative anerobic, aerobic reactions and precipitation, and can efficiently remove organic matter, nitrogen and phosphorus. After biochemical treatment, further flocculation and sedimentation treatment is used to remove residual heavy metal ions, suspended matter and other large particle impurities to ensure that the effluent water quality meets the 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. 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 comprehensively as cyanide-containing wastewater. 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 an indicator to measure the oxidation and reduction reaction ability in water. It is usually used to monitor and control the concentration of oxidants in water. In the process of cyanide oxidation, a high oxidant concentration is required to ensure the oxidation reaction of cyanide. The ORP control value is 600mV or above to ensure that cyanate is completely oxidized to carbonate and nitrogen. When the ORP value is greater than 500mV, the ozone aqueous solution has the ability to kill E. coli. The ORP control value should be set to ensure the removal effect of cyanide while not wasting the amount of ozone added, controlling costs and treatment effects.

[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 manufacturing process, complex wastewater mainly comes from the copper deposition process. This process uses a certain amount of complex copper. The wastewater contains a strong metal ion complex (EDTA) and is alkaline. Silver-containing wastewater mainly comes from the electroplating and chemical silver deposition processes. In these processes, silver ions enter the wastewater system through the cleaning and rinsing process, and the wastewater is acidic. The general method of removing silver ions is to add sodium sulfide to generate silver sulfide precipitation. However, if sodium sulfide is exposed to the air during storage, it will release toxic hydrogen sulfide gas with the smell of rotten eggs, which is harmful to human health and environmental safety.

[0028] After the complex wastewater and silver-containing wastewater are mixed, they are subjected to complex breaking treatment 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 complex breaking, 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] Based on the Fe(II) / Fe(III) redox cycle in the UV and air aeration process, the actual amount of ferric chloride required is relatively small, and trivalent iron can be circulated in the process. Too little ferric chloride will reduce the efficiency of complex breaking. Choosing the optimal dosage can ensure the complex breaking effect and reduce resource waste.

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

[0032] Under ultraviolet aeration conditions, it is necessary to maintain a high oxidation level in the wastewater to promote the production 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 characteristics of various types of wastewater generated in the production process of printed circuit boards to treat them in combination, combines nickel-containing wastewater and cyanide-containing wastewater for treatment, combines complex wastewater and silver-containing wastewater for treatment, and then conducts deep biochemical treatment with organic wastewater. This comprehensive treatment method simplifies the process of quality treatment of various types of wastewater, shortens the overall treatment time, and utilizes the acidity and alkalinity characteristics of water quality to reduce the consumption of acid and alkali agents 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 removal effect of nickel ions is better. In addition, 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 for complex breaking treatment, forming a Fe(II) / Fe(III) redox cycle, while reducing the consumption of trivalent iron, replacing the copper ions and silver ions in the complex, and exerting a complex breaking effect. 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 adopts 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 described embodiments 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 creative work are within the scope of protection of the present invention.

[0041] The water quality of the influent in the embodiments 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 method for comprehensive treatment of printed circuit board wastewater, which combines nickel-containing wastewater and cyanide-containing wastewater for treatment, and combines complex 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 homogenized in a ratio of 1:1, and the pH value was maintained at 7-8 by adding sodium hydroxide. After mixing, the wastewater entered the oxidation tank, and ozone bubbling was performed while ultraviolet irradiation was performed. The ORP control value in the wastewater was maintained at +600mV by adjusting the ozone dosage, and the complex breaking oxidation was performed for 3 hours. After completion, the effluent entered the regulating tank and sodium hydroxide was added to adjust the pH value to 9.5-11. The precipitation reaction was continued for 3 hours. The supernatant entered the phosphorus removal tank as the effluent, and 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 value to 6-7. It entered the coagulation tank, and 1.0g / L of PAC was added. Then it entered the flocculation tank and 0.5g / L of PAM was added. After precipitation in the sedimentation tank, the effluent was primary treated water. The results of water quality detection 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 after mixing. 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, after the decomposition treatment, the effluent enters the reaction sedimentation tank, and alkali is added to adjust the pH to 9.0-10.0, and the 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 and precipitation treatment to obtain secondary treated water. The results of the water quality test are: total silver content = 0.085mg / L, total copper content = 0.246mg / L;

[0049] 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 polyferric chloride, the organic matter in the sedimentation tank forms large suspended particles and precipitates, the effluent enters the callback tank, adds sodium hydroxide to adjust the pH to 9-9.5, and delivers 0.5g / L PAC to the coagulation tank, then enters the flocculation tank and adds 0.1g / L PAM, enters the sedimentation tank, flocculates and precipitates, removes suspended matter, 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, adds sulfuric acid to adjust the pH to 3.0-4.0, and enters the fen Hydrogen peroxide and ferrous sulfate were added to the Fenton oxidation pool for Fenton oxidation treatment. The concentration of hydrogen peroxide was 30%, the molar ratio of hydrogen peroxide to ferrous sulfate was 3:1, and the amount of hydrogen peroxide added was added in accordance with the COD content in the wastewater. The treated water entered the flocculation sedimentation tank, and 0.5g / L PAC and 0.3g / L PAM were added for flocculation sedimentation treatment. The effluent was mixed with the primary treated water and the secondary treated water and the pH was adjusted to 5.6-6.5. The volume ratio of primary treated water: secondary treated water: organic wastewater = 1:2:6, and then entered the hydrolysis acidification tank for hydrolysis acidification treatment to control the BOD of the effluent. 5 / COD ratio is 0.4. After treatment, it enters the IBR biochemical pool. 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 2.

[0050] Table 2

[0051]

[0052] Example 2

[0053] The only difference from Example 1 is that the molar ratio of Ni:CN in step S1 is - The ratio of the total nickel content to the total cyanide content is 0.141 mg / L, and the total phosphorus content is 0.336 mg / L. The quality of the secondary treated water is the same as that of Example 1.

[0054] The test results of the comprehensive treatment effluent water quality are 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 water was 1:2, and the other conditions and steps were the same as those in Example 1. The results of the water quality test of the primary treated water 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 water quality are shown in Table 4:

[0060] Table 4

[0061]

[0062] Example 4

[0063] The only difference from Example 2 is that in step S1, the ORP control value is 650mV, and the complex breaking oxidation is continued for 4h, and the other conditions and steps are the same as in Example 2. At this time, the water quality of the primary treated water is tested as follows: total nickel content = 0.022mg / L, total cyanide content = 0.105mg / L, and total phosphorus content = 0.154mg / L. The water quality of the secondary treated water is 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 is that in step S1, the ORP control value is 700mV, and the complex breaking oxidation is continued for 5h, and the other conditions and steps are the same as in Example 2. At this time, the water quality of the primary treated water is tested as follows: total nickel content = 0.021mg / L, total cyanide content = 0.099mg / L, and total phosphorus content = 0.146mg / L. The water quality of the secondary treated water is 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, and the other conditions and steps are the same as those in Example 5. At this time, the water quality of the secondary treated water is tested as follows: 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 that in Example 5.

[0075] The test results of the comprehensive treatment effluent water 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, and the other conditions and steps are the same as those in Example 5. At this time, the water quality of the secondary treated water is tested as follows: 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 that 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 is that in step S2, the ORP control value is 150mV, and the chelation breaking treatment is continued for 0.8h, and the other conditions and steps are the same as those in Example 5. At this time, the water quality of the secondary treated water is tested as follows: total silver content = 0.055mg / L, total copper content = 0.127mg / L. The water quality of the primary treated water is the same as that 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 is that in step S2, the ORP control value is 200mV, and the chelation breaking treatment is continued for 1h, and the other conditions and steps are the same as those in Example 5. At this time, the water quality of the secondary treated water is tested as follows: total silver content = 0.053mg / L, total copper content = 0.119mg / L. The water quality of the primary treated water is the same as that in Example 6.

[0090] The test results of the effluent water quality after comprehensive treatment 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 method is used to replace ultraviolet ozone method for treatment, and 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 homogenized 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, and the complex breaking oxidation is continued for 1 hour. After completion, the effluent enters the regulating tank and sulfuric acid is added to adjust the pH to 6.5-7, and 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, and the complex breaking oxidation is continued for 1 hour. The effluent enters the regulating tank and sodium hydroxide is added The pH value was adjusted to 9.5-11, and the precipitation reaction was continued for 3 hours. The supernatant was used as 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 was the primary treated water after sedimentation. The results of water quality testing 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.

[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 after mixing. 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 decomposition treatment, the effluent enters the reaction sedimentation tank, and alkali is added to adjust the pH to 9.0-10.0, and the 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 and precipitation treatment to obtain secondary treated water. The results of the water quality test are: total silver content = 0.085mg / L, total copper content = 0.246mg / L;

[0098] 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 polyferric chloride, the organic matter in the sedimentation tank forms large suspended particles and precipitates, the effluent enters the callback tank, adds sodium hydroxide to adjust the pH to 9-9.5, and delivers 0.5g / L PAC to the coagulation tank, then enters the flocculation tank and adds 0.1g / L PAM, enters the sedimentation tank, flocculates and precipitates, removes suspended matter, 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, adds sulfuric acid to adjust the pH to 3.0-4.0, and enters the fen Hydrogen peroxide and ferrous sulfate were added to the Fenton oxidation pool for Fenton oxidation treatment. The concentration of hydrogen peroxide was 30%, the molar ratio of hydrogen peroxide to ferrous sulfate was 3:1, and the amount of hydrogen peroxide added was added in accordance with the COD content in the wastewater. The treated water entered the flocculation sedimentation tank, and 0.5g / L PAC and 0.3g / L PAM were added for flocculation sedimentation treatment. The effluent was mixed with the primary treated water and the secondary treated water and the pH was adjusted to 5.6-6.5. The volume ratio of primary treated water: secondary treated water: organic wastewater = 1:2:6, and then entered the hydrolysis acidification tank for hydrolysis acidification treatment to control the BOD of the effluent. 5 / COD ratio is 0.4. After treatment, it enters the IBR biochemical pool. After biochemical treatment, 0.3g / L PAM is added for flocculation and sedimentation. The effluent water quality test results are shown in Table 11.

[0099] Table 11

[0100]

[0101] Comparative Example 2

[0102] Compared with Example 1, the difference of this comparative example is that when the complex wastewater and the silver-containing wastewater are treated together, the ultraviolet air aeration method is replaced by directly adding ferrous sulfate for treatment, and the specific treatment steps are as follows:

[0103] 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 homogenized in a ratio of 1:1, and the pH value was maintained at 7-8 by adding sodium hydroxide. After mixing, the wastewater entered the oxidation tank, and ozone bubbling was performed while ultraviolet irradiation was performed. The ORP control value in the wastewater was maintained at +600mV by adjusting the ozone dosage, and the complex breaking oxidation was performed for 3 hours. After completion, the effluent entered the regulating tank and sodium hydroxide was added to adjust the pH value to 9.5-11. The precipitation reaction was continued for 3 hours. The supernatant entered the phosphorus removal tank as the effluent, and 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 value to 6-7. It entered the coagulation tank, and 1.0g / L of PAC was added. Then it entered the flocculation tank and 0.5g / L of PAM was added. After precipitation in the sedimentation tank, the effluent was primary treated water. The results of water quality detection were: total nickel content = 0.072mg / L, total cyanide content = 0.123mg / L, and total phosphorus content = 0.284mg / L.

[0104] 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 after mixing. 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.

[0105] S3, after the decomposition treatment, the effluent enters the reaction sedimentation tank, and alkali is added to adjust the pH to 9.0-10.0, and the 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 and precipitation treatment to obtain secondary treated water. The results of the water quality test are: 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 suspended particles and precipitates. The effluent enters the callback tank, adds sodium hydroxide to adjust the pH to 9-~9.5, and sends it to the coagulation tank to add 0.5g / L of PAC, then enters the flocculation tank to add 0.1g / L of PAM, enters the sedimentation tank, flocculates and precipitates, removes suspended matter, and 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, adds sulfuric acid to adjust the pH to 3.0-4.0, and enters Hydrogen peroxide and ferrous sulfate were added to the Fenton oxidation pond for Fenton oxidation treatment. The concentration of hydrogen peroxide was 30%, the molar ratio of hydrogen peroxide to ferrous sulfate was 3:1, and the amount of hydrogen peroxide added was added in equal mass according to the COD content in the wastewater. The treated water entered the flocculation sedimentation tank, and 0.5g / L PAC and 0.3g / L PAM were added for flocculation sedimentation treatment. The effluent was mixed with the primary treated water and the secondary treated water and the pH was adjusted to 5.6-6.5. The volume ratio of primary treated water: secondary treated water: organic wastewater = 1:2:6, and entered the hydrolysis acidification tank for hydrolysis acidification treatment to control the BOD of the effluent. 5 / COD ratio is 0.4. After treatment, it enters the IBR biochemical pool. 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 to replace 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 homogenized 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 dosage of sodium hypochlorite, and the complex breaking oxidation is continued for 1 hour. 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 dosage of sodium hypochlorite. The complex breaking oxidation is continued for 1 hour. 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 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 was the primary treated water after sedimentation. The results of water quality testing 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 homogenization tank, sulfuric acid is added to maintain the pH at 2-3, and then enter the oxidation tank after mixing. 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 decomposition treatment, the effluent enters the reaction sedimentation tank, and alkali is added to adjust the pH to 9.0-10.0, and the 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 and precipitation treatment to obtain secondary treated water. The results of the water quality test 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 polyferric chloride, the organic matter in the sedimentation tank forms large suspended particles and precipitates, the effluent enters the callback tank, adds sodium hydroxide to adjust the pH to 9-9.5, and delivers 0.5g / L PAC to the coagulation tank, then enters the flocculation tank and adds 0.1g / L PAM, enters the sedimentation tank, flocculates and precipitates, removes suspended matter, 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, adds sulfuric acid to adjust the pH to 3.0-4.0, and enters the fen Hydrogen peroxide and ferrous sulfate were added to the Fenton oxidation pool for Fenton oxidation treatment. The concentration of hydrogen peroxide was 30%, the molar ratio of hydrogen peroxide to ferrous sulfate was 3:1, and the amount of hydrogen peroxide added was added in accordance with the COD content in the wastewater. The treated water entered the flocculation sedimentation tank, and 0.5g / L PAC and 0.3g / L PAM were added for flocculation sedimentation treatment. The effluent was mixed with the primary treated water and the secondary treated water and the pH was adjusted to 5.6-6.5. The volume ratio of primary treated water: secondary treated water: organic wastewater = 1:2:6, and then entered the hydrolysis acidification tank for hydrolysis acidification treatment to control the BOD of the effluent. 5 / COD ratio is 0.4. After treatment, it enters the IBR biochemical pool. After biochemical treatment, 0.3g / L PAM is added for flocculation and 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 is appropriately increased. It is conducive to forming carbonate, promoting 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, partial cyanide is not completely oxidized, and total cyanide content can rise, and in embodiment 4 and embodiment 5, on the basis of embodiment 2, ORP control value is improved, and the oxidizing capacity of system is enhanced, and now its total cyanide content is significantly reduced compared to embodiment 2. Embodiment 6 and embodiment 7 increase the dosage of ferric iron for the broken network treatment of complex wastewater and silver-containing wastewater, and its broken network effect can be enhanced, and the removal effect of copper is better, and in embodiment 9, ORP control value is 200mV when complex wastewater and silver-containing wastewater are treated, and the total copper content in its secondary treated water is as low as 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 GB 39731-2020 Electronic Industry Water Pollutant Emission Standard, while the water quality of Comparative Example 3 did not meet the standards.

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

[0119] Although 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 the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present 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 homogenously mixed, the chelation-breaking oxidation is carried out under ultraviolet and ozone bubbling conditions, and 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 the silver-containing wastewater are homogeneously mixed, ferric chloride is added under ultraviolet and air aeration conditions to carry out complex breaking treatment; S3, after the chelation treatment, the pH is adjusted to 9.0-10.0, and 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 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 method for comprehensive treatment of 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 method for comprehensive treatment of 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 with a molar ratio of Ni:CN - It is 1:1~2.

4. A method for comprehensive treatment of 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 amount of ozone added during the complex breaking oxidation.

5. A 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 method for comprehensive treatment of printed circuit board wastewater according to claim 1, characterized in that: In step S2, the pH of the complex wastewater and the silver-containing wastewater is maintained at 2-3 when being homogeneously mixed.

7. A 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. A 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 air aeration.

9. A 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. A 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.

Images