A method for pretreating semi-coking wastewater by a zero-valent iron process combined with ultrasonic-flocculation method

Abstract

The present application belongs to the technical field of wastewater treatment, and relates to a method for pretreating coking wastewater by zero-valent iron process combined with ultrasonic-flocculation method, comprising the following steps: 1) the wastewater is subjected to heating and ultrasonic degradation treatment; 2) air is introduced into the wastewater after ultrasonic degradation, and a composite flocculant, iron filings and coal-based acicular coke powder are sequentially added, and ultrasonic stirring and standing and sedimentation are performed to complete the pretreatment. The present application provides a method for pretreating coking wastewater by zero-valent iron process combined with ultrasonic-flocculation method, which effectively removes pollutants in the coking wastewater, improves the subsequent biodegradability of the wastewater, has low implementation cost, and has large-scale popularization and application value.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of wastewater treatment, and relates to a method for pretreating semicoke wastewater, in particular to a method for pretreating semicoke wastewater by combining a zero-valent iron process with an ultrasonic-flocculation method. BACKGROUND

[0002] Semicoke is a solid coke product produced by using low metamorphic coal as raw material and adopting a medium-low temperature dry distillation technology. A large amount of wastewater is generated in the production of semicoke and the conveying process of raw coal, mainly including semicoke quenching water, coal gas purification water and dust removal washing water. The dust removal washing water contains high-concentration suspended solid coal dust, semicoke particulate matter and the like, and can be reused after clarification. The composition of the coal gas purification water and the quenching water is extremely complex, and contains a large amount of non-degradable toxic pollutants, such as phenolic substances, single-ring aromatic hydrocarbons, polycyclic aromatic hydrocarbons, nitrogen-containing heterocyclic aromatic compounds, cyanide, thiocyanate and ammonia nitrogen and the like. If such wastewater is directly discharged without treatment, it will pollute natural water bodies, cause eutrophication of water bodies and bring serious hidden dangers to human health. In particular, the phenolic substances and their derivatives have high biological toxicity, not only have toxic effects on the human body and the water environment, but also have inhibitory and toxic effects on microorganisms in the biochemical process of water treatment. Therefore, it is necessary to pretreat the semicoke wastewater to reduce the pollution of the phenolic substances and their derivatives to the environment and reduce the influence on the subsequent treatment unit.

[0003] At present, the main methods of pre-treating the semi-coke wastewater are: negative pressure distillation method, solvent extraction method, flocculation precipitation method, etc. CN114349253A discloses that the wastewater tank containing phenolic wastewater to be treated is subjected to alkali treatment, the pH is adjusted to above 13, the treated wastewater is transported to an evaporator for evaporation, the temperature in the evaporator is below 60 DEG C, and the vacuum degree is less than or equal to -0.08 Mpa; the evaporated wastewater is subjected to alkali treatment again, the pH is adjusted to above 13, the treated wastewater is transported to a second evaporator for evaporation, the temperature in the second evaporator is below 41.5 DEG C, and the vacuum degree is less than or equal to -0.092 Mpa, and the product condensate is obtained by steam condensation recovery. CN110655259A discloses that the wastewater is subjected to oil removal treatment, the oil removal effluent is subjected to phenol extraction, and then subjected to ammonia evaporation treatment, the extracted liquid and the ammonia evaporation wastewater are subjected to heat exchange treatment, the extracted liquid after temperature rise is subjected to permeation vaporization treatment, so as to separate the extractant and the phenolic compounds; the extractant and the ammonia evaporation wastewater after heat exchange are subjected to secondary heat exchange, the final extractant is recovered, and the ammonia evaporation wastewater enters the next biochemical treatment. CN103553260B discloses that diisopropyl ether and methyl isobutyl ketone are used as extractants for synergistic extraction and phenol removal, the volume ratio of diisopropyl ether to methyl isobutyl ketone is 1:10-1:1, and the volume ratio of the extractant to water is 1:18-1:5.5; then the wastewater is pumped into a phenol tower for negative pressure flash evaporation, and the extractant is recycled after collection. Although the above method can remove part of the pollutants to a certain extent, it still has the technical problems of low pollutant removal efficiency, high cost, complex process, expensive equipment, high energy consumption, high cost and easy secondary pollution. SUMMARY

[0004] In view of the technical problems of low pollutant removal efficiency and high cost in the existing semi-coke wastewater pre-treatment, the present application provides a method for pre-treating semi-coke wastewater by combining zero-valent iron process and ultrasonic-flocculation method, which effectively removes pollutants in the semi-coke wastewater, improves the subsequent biodegradability of the wastewater, has low implementation cost and has great value for large-scale popularization and application.

[0005] To achieve the above-mentioned purposes, the technical scheme adopted by the present application is as follows:

[0006] A method for pre-treating semi-coke wastewater by combining zero-valent iron process and ultrasonic-flocculation method, comprising the following steps:

[0007] 1) heating and ultrasonic degradation treatment of the wastewater;

[0008] 2) air is introduced into the wastewater after ultrasonic degradation in step 1), composite flocculants, iron filings and coal-based needle coke powder are sequentially added, and ultrasonic stirring and standing settlement are performed to complete the pre-treatment.

[0009] The composite flocculant comprises inorganic flocculant and organic flocculant; the inorganic flocculant is added in an amount of 1.0 g / L wastewater to 2.0 g / L wastewater; the organic flocculant is added in an amount of 20 mg / L wastewater to 30 mg / L wastewater; the iron scrap is added in an amount of 10 g / L wastewater to 40 g / L wastewater, and the coal-based needle coke powder is added in an amount of 0 g / L wastewater to 10 g / L wastewater.

[0010] Further limitation, the heating temperature in the step 1) is 40 DEG C to 60 DEG C, and the ultrasonic degradation parameters are as follows: frequency 400.0 KHz to 800.0 KHz, and degradation time 1h to 2h.

[0011] Further limitation, before the step 1), the pH of the wastewater needs to be adjusted to 4.0 to 6.0.

[0012] Further limitation, before the step 1), the pH of the wastewater needs to be adjusted to 5.0.

[0013] Further limitation, in the step 2), the inorganic flocculant is polyaluminum ferric chloride, and the organic flocculant is cationic polyacrylamide.

[0014] Further limitation, the resistivity of the coal-based needle coke powder is 300 u Omega.m.

[0015] Further limitation, in the step 2), the ultrasonic stirring conditions are as follows: frequency 60 kHz to 80 kHz, temperature 40 DEG C to 60 DEG C, stirring speed 40 r / min to 200 r / min, and stirring time 10 min to 15 min; and the standing time is 1h to 1.5h.

[0016] Compared with the prior art, the technical effect of the present application is:

[0017] 1、The present application adopts ultrasonic technology to assist in treating semi-coke wastewater, and ultrasonic waves can produce cavitation effect in wastewater, so that water molecules produce various free radicals to react with organic matters in the wastewater, so as to achieve the purpose of degrading and removing organic matters; in addition, the ultrasonic technology greatly improves the contact frequency between flocculants and substances in the wastewater, which is beneficial to enhancing the flocculation effect.

[0018] 2. The present invention utilizes both inorganic and organic flocculation to accelerate the settling of organic matter in pollutants. Specifically, a composite flocculation method employing inorganic and organic flocculants increases the hydrolysis rate. In particular, the composite flocculant of polyaluminum ferric chloride and cationic polyacrylamide (PAFC-CPAM) accelerates hydrolysis, forming large, dense flocs with rapid settling rates, minimal impact on water temperature fluctuations, and superior treatment effectiveness, saving 10-20% in costs compared to other flocculants. PAFC possesses the properties of both aluminum and iron salts, offering significant performance advantages. PAFC hydrolysis generates positively charged polynuclear hydroxyl coordination compounds, which adsorb and electrically neutralize negatively charged colloidal particles in the wastewater, rapidly destabilizing them and forming flocs. The amide groups of CPAM can form affinity with and adsorb to form hydrogen bonds with many substances in the wastewater, generating adsorption bridging. Furthermore, the positively charged groups of CPAM can neutralize negatively charged suspended particles, promoting floc aggregation and enhancing the flocculation effect.

[0019] 3. The present invention further enhances the treatment effect of lignite wastewater by introducing air into the ultrasonically stirred wastewater and sequentially adding iron filings and coal-based needle coke powder. This is because coal-based needle coke is a high-quality electrode material prepared from coal tar. In this process, coal-based needle coke can not only effectively adsorb and remove organic matter and certain pollutants in the wastewater through macroscopic electrode reactions, but also protect zero-valent iron from damage, thereby extending its service life. Zero-valent iron can undergo redox reactions with pollutants in the lignite wastewater to degrade them, and can also adsorb difficult-to-degrade compounds such as heavy metals and organic matter in the water. In addition, this process produces some new ester compounds, thereby improving the biodegradability of the wastewater.

[0020] 4. When the present invention treats wastewater with a COD of 30,000 mg / L to 36,000 mg / L, the COD removal rate reaches up to 78%, the total phenol removal rate reaches 57%, and the BOD5 / COD is increased to 68%. This greatly reduces the difficulty of subsequent biochemical and deep treatment of high-concentration organic matter and is worthy of large-scale promotion and application. DETAILED DESCRIPTION

[0021] The present invention will now be described in detail with reference to the embodiments.

[0022] A method for pretreating semi-coal wastewater using a zero-valent iron process combined with an ultrasound-flocculation method comprises the following steps:

[0023] 1) The wastewater is treated by heating and ultrasonic degradation. The wastewater is semi-coal wastewater.

[0024] The heating temperature is 40° C. to 60° C., the ultrasonic degradation parameters are: frequency 400.0 to 800.0 KHz, and the degradation time is 1 to 2 hours.

[0025] In order to improve the degradation of the wastewater, the wastewater is acidized before step 1) to adjust the pH of the wastewater to 4.0-6.0. Preferably, the pH of the wastewater is adjusted to 5.0.

[0026] 2) Air is introduced into the wastewater after the ultrasonic degradation of step 1), and a composite flocculant, iron filings and coal-based needle coke powder are sequentially added, and ultrasonic stirring and standing and sedimentation are performed to complete the pretreatment.

[0027] In step 2), the composite flocculant comprises an inorganic flocculant and an organic flocculant; the inorganic flocculant is added in an amount of 1.0 g / L wastewater-2.0 g / L wastewater; and the organic flocculant is added in an amount of 20 mg / L wastewater-30 mg / L wastewater.

[0028] The inorganic flocculant is polyaluminum ferric chloride (PAFC), and the organic flocculant is cationic polyacrylamide (CPAM). The inorganic flocculant is added first, and then the organic flocculant is added.

[0029] In step 2), the iron filings are added in an amount of 10 g / L wastewater-40 g / L wastewater, and the coal-based needle coke powder is added in an amount of 0 g / L wastewater-10 g / L wastewater.

[0030] The ultrasonic stirring is performed at a frequency of 60 kHz-80 kHz, a temperature of 40℃-60℃, a stirring speed of 40 r / min-200 r / min, and for a time of 10 min-15 min; and the standing time is 1 h-1.5 h.

[0031] During the ultrasonic stirring, the stirring is performed at a high speed in the first half of the time period and at a low speed in the second half of the time period.

[0032] The coal-based needle coke powder used in the present application mainly has a requirement for electrical conductivity, and the resistivity is about 300 uΩ.m. In practice, the coal-based needle coke powder is prepared from coal tar.

[0033] In order to make the purpose, technical scheme and advantages of the present application more clear, the embodiments of the present application will be further described in detail below, but this should not be taken as a limitation on the protection scope of the present application.

[0034] The semi-coke wastewater in the following examples and comparative examples is from a semi-coke plant in Yulin, Shaanxi: it is black-red in appearance, has a pungent odor, has a pH of about 9, a COD of 30000 mg / L-36000 mg / L, a total phenol content of 9000 mg / L-10000 mg / L, and a BOD5 / COD value of 5%.

[0035] Example 1

[0036] 1) 1 L of semi-coke wastewater is taken, the pH is adjusted to 5.0, heated to 40℃, and ultrasonically treated at 600 kHz for 1 h.

[0037] 2) To the wastewater after ultrasonic treatment, pump in air, add 1.5 g / L of polymeric aluminum ferric chloride and 25 mg / L of cationic polyacrylamide, then add 10 g / L of iron filings and 5 g / L of coal-based needle coke powder, first stir at 200 r / min for 5 min under 50 kHz ultrasonic condition, then stir at 50 r / min for 5 min, stand for 1 h, and then take the supernatant for analysis.

[0038] Example 2

[0039] 1) Take 1 L of blue carbon wastewater, adjust the pH to 5.0, heat to 40℃, and ultrasonic treat for 1 h under 600 kHz condition.

[0040] 2) To the wastewater after ultrasonic treatment, pump in air, add 1.5 g / L of polymeric aluminum ferric chloride and 25 mg / L of cationic polyacrylamide, then add 20 g / L of iron filings and 5 g / L of coal-based needle coke powder, first stir at 200 r / min for 5 min under 50 kHz ultrasonic condition, then stir at 50 r / min for 5 min, stand for 1 h, and then take the supernatant for analysis.

[0041] Example 3

[0042] 1) Take 1 L of blue carbon wastewater, adjust the pH to 5.0, heat to 40℃, and ultrasonic treat for 1 h under 600 kHz condition.

[0043] 2) To the wastewater after ultrasonic treatment, pump in air, add 1.5 g / L of polymeric aluminum ferric chloride and 25 mg / L of cationic polyacrylamide, then add 30 g / L of iron filings and 5 g / L of coal-based needle coke powder, first stir at 200 r / min for 5 min under 50 kHz ultrasonic condition, then stir at 50 r / min for 5 min, stand for 1 h, and then take the supernatant for analysis.

[0044] Example 4

[0045] 1) Take 1 L of blue carbon wastewater, adjust the pH to 5.0, heat to 40℃, and ultrasonic treat for 1 h under 600 kHz condition.

[0046] 2) To the wastewater after ultrasonic treatment, pump in air, add 1.5 g / L of polymeric aluminum ferric chloride and 25 mg / L of cationic polyacrylamide, then add 40 g / L of iron filings and 5 g / L of coal-based needle coke powder, first stir at 200 r / min for 5 min under 50 kHz ultrasonic condition, then stir at 50 r / min for 5 min, stand for 1 h, and then take the supernatant for analysis.

[0047] The supernatant after the pretreatment of the above Examples 1-4 was analyzed to calculate the COD removal rate, total phenol removal rate, and BOD5 / COD improvement rate. The results are shown in Table 1.

[0048] Table 1 Pretreatment results of Examples 1-4

[0049] COD removal % Total phenol removal % COD removal % Total phenol removal % BOD5 / COD improvement % Example 1 67 50 55 Example 2 78 57 68 Example 3 75 58 69 Example 4 70 53 63

[0050] As shown in Table 1, with the increase of the amount of iron filings, the COD removal rate and the total phenol removal rate both showed a trend of first increasing and then decreasing, but the COD removal rate was more than 67%, and the total phenol removal rate was more than 50%. Preferably, when the amount of iron filings is 20-30 g / L, the COD and total phenol removal effects are better.

[0051] Example 5

[0052] 1) Take 1 L of blue coal wastewater, adjust the pH to 5.0, heat to 40°C, and ultrasonically treat for 1 h under the condition of 600 kHz.

[0053] 2) Pump air into the wastewater after ultrasonic treatment, add 1.5 g / L of polyaluminum ferric chloride and 25 mg / L of cationic polyacrylamide, then add 20 g / L of iron filings and 10 g / L of coal-based needle coke powder, stir at a high speed of 200 r / min for 5 min under the condition of 50 kHz ultrasonic, then stir at a low speed of 50 r / min for 5 min, and after standing and settling for 1 h, take the supernatant for analysis.

[0054] Example 6

[0055] 1) Take 1 L of blue coal wastewater, adjust the pH to 5.0, heat to 40°C, and ultrasonically treat for 1 h under the condition of 600 kHz.

[0056] 2) Pump air into the wastewater after ultrasonic treatment, add 1.5 g / L of polyaluminum ferric chloride and 25 mg / L of cationic polyacrylamide, then add 20 g / L of iron filings and 10 g / L of coal-based needle coke powder, stir at a high speed of 200 r / min for 5 min under the condition of 50 kHz ultrasonic, then stir at a low speed of 50 r / min for 5 min, and after standing and settling for 1 h, take the supernatant for analysis.

[0057] The supernatant after the pretreatment of the above Examples 5-6 was analyzed to calculate the COD removal rate, total phenol removal rate, and BOD5 / COD improvement rate. The results are shown in Table 2.

[0058] Table 2 Pretreatment results of Examples 5-6

[0059] COD removal % Total phenol removal % COD removal % Total phenol removal % BOD5 / COD improvement % Example 5 79 56 66 Example 6 64 49 57

[0060] As can be seen from Table 2, when the coal-based acicular coke is not added in Example 6, the COD removal rate is 64%, the total phenol removal rate is 49%, and the BOD5 / COD improvement rate is 57%. After adding 5 g / L of coal-based acicular coke and 10 g / L of coal-based acicular coke, the COD removal rate, the total phenol removal rate and the BOD5 / COD improvement rate are all improved, but the difference is not large. When the coal-based acicular coke is 5 g / L, the removal effect is better.

[0061] Comparative Example 1

[0062] Different from the examples, iron filings and coal-based acicular coke are not added in the pretreatment process.

[0063] 1) Take 1L of blue charcoal wastewater, adjust the pH to 5.0, heat to 40℃, and ultrasonic treat for 1h under the condition of 600kHz.

[0064] 2) Pump air into the wastewater after ultrasonic treatment, add 0.5g / L of polyaluminum ferric chloride PAFC and 25mg / L of cationic polyacrylamide, first stir at a high speed of 200r / min for 5min under the condition of 50kHz ultrasonic, then stir at a low speed of 50r / min for 5min, and after standing and settling for 1h, take the supernatant for analysis.

[0065] Comparative Example 2

[0066] Different from Comparative Example 1, the adding amount of polyaluminum ferric chloride PAFC and cationic polyacrylamide is different.

[0067] 1) Take 1L of blue charcoal wastewater, adjust the pH to 5.0, heat to 40℃, and ultrasonic treat for 1h under the condition of 600kHz.

[0068] 2) Pump air into the wastewater after ultrasonic treatment, add 1.0g / L of polyaluminum ferric chloride PAFC and 25mg / L of cationic polyacrylamide, first stir at a high speed of 200r / min for 5min under the condition of 50kHz ultrasonic, then stir at a low speed of 50r / min for 5min, and after standing and settling for 1h, take the supernatant for analysis.

[0069] Comparative Example 3

[0070] Different from Comparative Example 1, the adding amount of polyaluminum ferric chloride PAFC and cationic polyacrylamide is different.

[0071] 1) Take 1L of blue charcoal wastewater, adjust the pH to 5.0, heat to 40℃, and ultrasonic treat for 1h under the condition of 600kHz.

[0072] 2) Pump air into the wastewater after ultrasonic treatment, add 1.5 g / L of polymeric aluminum ferric chloride PAFC and 25 mg / L of cationic polyacrylamide, first stir at 200 r / min for 5 min under 50 kHz ultrasonic condition, then stir at 50 r / min for 5 min, stand for 1 h after settling, and then take supernatant for analysis.

[0073] Comparative Example 4

[0074] Different from Comparative Example 1, the adding amount of polymeric aluminum ferric chloride PAFC and cationic polyacrylamide is different.

[0075] 1) Take 1 L of Lanmei carbon wastewater, adjust pH to 5.0, heat to 40℃, and ultrasonic treat for 1 h under 600 kHz condition.

[0076] 2) Pump air into the wastewater after ultrasonic treatment, add 2.0 g / L of polymeric aluminum ferric chloride PAFC and 25 mg / L of cationic polyacrylamide, first stir at 200 r / min for 5 min under 50 kHz ultrasonic condition, then stir at 50 r / min for 5 min, stand for 1 h after settling, and then take supernatant for analysis.

[0077] Analyze the supernatant after the pretreatment of Comparative Examples 1-4 above, calculate the COD removal rate, total phenol removal rate and BOD5 / COD improvement rate, and the results are shown in Table 3.

[0078] Table 3 Pretreatment results of Comparative Examples 1-4

[0079]

[0080]

[0081] As can be seen from Table 3, when the adding amount of polymeric aluminum ferric chloride in the flocculant is 0.5-2.0 g / L, the pretreatment effect shows a trend of first increasing and then decreasing, and the effect is best when the adding amount is 1.5 g / L, the COD removal rate, total phenol removal rate and BOD5 / COD improvement rate are 47%, 33% and 35% respectively; it can be known from the comparison between Example 2 and Comparative Example 3 that after the addition of coal-based needle coke and iron filings, the pretreatment effect is significantly improved, which is because the coal-based needle coke can effectively adsorb and remove organic matter and certain pollutants in the wastewater through macro-electrode reaction; zero-valent iron can oxidize and reduce pollutants in the Lanmei carbon wastewater to make them degrade, and can also adsorb heavy metals, organic matter and other refractory compounds in water, in addition, the process can produce some new ester compounds, thereby improving the biodegradability of the wastewater.

[0082] Comparative Example 5

[0083] The treatment method is the same as that of Example 2, except that no ultrasonic treatment is performed.

[0084] 1) Take 1 L of Lan coal wastewater, adjust the pH to 5.0, heat to 40°C, and treat for 1 h.

[0085] 2) Pump air into the treated wastewater, add 1.5 g / L of polyaluminum ferric chloride and 25 mg / L of cationic polyacrylamide, and then add 20 g / L of iron filings and 5 g / L of coal-based needle coke powder. Stir at 200 r / min for 5 min and then at 50 r / min for 5 min under 50 kHz ultrasonic conditions. After standing and settling for 1 h, take the supernatant for analysis.

[0086] Comparative Example 6

[0087] The treatment method is the same as that of Example 2, except that no acidification treatment is performed.

[0088] 1) Take 1 L of Lan coal wastewater and heat to 40°C. Ultrasonically treat under 600 kHz conditions for 1 h.

[0089] 2) Pump air into the ultrasonically treated wastewater, add 1.5 g / L of polyaluminum ferric chloride and 25 mg / L of cationic polyacrylamide, and then add 20 g / L of iron filings and 5 g / L of coal-based needle coke powder. Stir at 200 r / min for 5 min and then at 50 r / min for 5 min under 50 kHz ultrasonic conditions. After standing and settling for 1 h, take the supernatant for analysis.

[0090] Comparative Example 7

[0091] The treatment method is the same as that of Example 2, except that no flocculant is added.

[0092] 1) Take 1 L of Lan coal wastewater, adjust the pH to 5.0, heat to 40°C, and treat for 1 h under 600 kHz ultrasonic conditions.

[0093] 2) Pump air into the ultrasonically treated wastewater, add 20 g / L of iron filings and 5 g / L of coal-based needle coke powder. Stir at 200 r / min for 5 min and then at 50 r / min for 5 min under 50 kHz ultrasonic conditions. After standing and settling for 1 h, take the supernatant for analysis.

[0094] The supernatant after pretreatment of the above Comparative Examples 5-7 is analyzed, and the COD removal rate, total phenol removal rate, and BOD5 / COD improvement rate are calculated. The results are shown in Table 4.

[0095] Table 4 Pretreatment results of Comparative Examples 5-7

[0096] COD removal % Total phenol removal % COD removal % Total phenol removal % BOD5 / COD improvement % Comparative Example 5 60 41 58 Comparative Example 6 58 37 55 Comparative Example 7 47 33 49

[0097] From table 4, it can be seen that the comparative example 5 does not use ultrasonic treatment, and the pretreatment effect is reduced, which is due to the lack of ultrasonic cavitation effect on the degradation of pollutants, and the reduction of the contact frequency of other added substances and pollutants; from the comparative example 6, it can be seen that the pretreatment effect is reduced without acidification treatment, which is due to the fact that the flocculation and zero-valent iron process need a certain acidic condition to play the effect; from the comparative example 7, it can be seen that the pretreatment effect is obviously reduced without adding flocculants, which is due to the fact that the hydrolysis of PAFC in the flocculant can generate positively charged multi-nuclear hydroxyl complex, which can adsorb and electrically neutralize the negatively charged colloidal particles in the wastewater, so that the colloidal particles are quickly destabilized to form flocs; the amide group of CPAM can be affinity, adsorption and hydrogen bond with many substances in the wastewater, so that the adsorption bridge effect occurs; in addition, the group of CPAM has positive charge, which can neutralize the charge of the negatively charged suspended particles, promote the coagulation of the flocs, and enhance the flocculation effect.

[0098] The above comparison data can show that in the high-COD blue charcoal wastewater pretreatment method provided by the application, acidification, ultrasonic, composite flocculation and sedimentation, and the selective addition of iron filings and coal-based needle coke are all indispensable, and have a synergistic effect, which can promote the removal of COD and total phenol in high-concentration COD wastewater through the treatment mode of ultrasonic-assisted-composite flocculation degradation-iron filings and coal-based needle coke powder combination.

[0099] Through the blue charcoal wastewater pretreatment method of the application, the COD removal rate of high-COD blue charcoal wastewater can reach 78%, the total phenol removal rate can reach 57%, and the BOD5 / COD can be increased by 68%, which greatly reduces the difficulty of subsequent biochemical and deep treatment, and is worthy of large-scale popularization and application.

[0100] The above is part of the embodiment of the application, and the technical solution of the blue charcoal pretreatment method of the application should not be limited to the above-mentioned examples. Any replacement or modification made under the guidance of the technical idea of the application should fall within the protection scope of the technical solution of the application.

Claims

1. A method for pretreating semi-coke wastewater using a zero-valent iron process combined with ultrasound-flocculation, characterized in that: The following steps are involved: 1) The wastewater is heated and subjected to ultrasonic degradation. The ultrasonic degradation parameters are: frequency 400.0 kHz to 800.0 kHz, and degradation time 1 hour to 2 hours. Prior to step 1), the pH of the wastewater is adjusted to 4.0 to 6.

0. 2) introducing air into the wastewater after ultrasonic degradation in step 1), adding a composite flocculant, iron filings, and coal-based needle coke powder in sequence, and performing ultrasonic stirring and static sedimentation to complete the pretreatment; The composite flocculant includes an inorganic flocculant and an organic flocculant; the dosage of the inorganic flocculant is 1.0g / L to 2.0g / L of wastewater; the dosage of the organic flocculant is 20mg / L to 30mg / L of wastewater; the amount of iron filings added is 10g / L to 40g / L of wastewater, and the amount of coal-based needle coke powder added is 5g / L to 10g / L of wastewater; the inorganic flocculant is polyaluminum ferric chloride, and the organic flocculant is cationic polyacrylamide; the resistivity of the coal-based needle coke powder is 300uΩ.m.

2. The method for pretreating semi-coke wastewater by combining zero-valent iron process with ultrasound-flocculation method according to claim 1, characterized in that: Step 1), the heating temperature is 40℃~60℃.

3. The method for pretreating semi-coke wastewater by using a zero-valent iron process combined with ultrasound-flocculation method according to claim 2, characterized in that: Before step 1), the pH of the wastewater needs to be adjusted to 5.

0.

4. The method for pretreating semi-coke wastewater by using a zero-valent iron process combined with ultrasound-flocculation method according to claim 3, characterized in that: The ultrasonic stirring conditions in step 2) are as follows: frequency 60 kHz to 80 kHz, temperature 40° C. to 60° C., stirring speed 40 r / min to 200 r / min, stirring time 10 min to 15 min; and standing time 1 h to 1.5 h.

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