A process for treating coking wastewater

Abstract

The application discloses a coking wastewater treatment process, which comprises the following steps: pretreating coking wastewater to obtain pretreated coking wastewater; adding modified carbonized coconut shell adsorbent into the pretreated coking wastewater, uniformly mixing, standing, filtering, and obtaining a first filtrate; adjusting the pH value of the first filtrate, adding hydrogen peroxide, uniformly mixing, standing, simultaneously performing light irradiation treatment, filtering after precipitation, and obtaining a second filtrate; performing electrochemical oxidation on the second filtrate, filtering, and discharging; wherein the modified carbonized coconut shell adsorbent is prepared by modifying carbonized coconut shell with 3,3',4,4'-benzophenonetetracarboxylic dianhydride; by adopting the coking wastewater pretreatment-modified carbonized coconut shell adsorbent adsorption flocculation-pH adjustment-hydrogen peroxide treatment-electrochemical oxidation-filtration-discharge, the content of COD, volatile phenol, cyanide, suspended solids and ammonia nitrogen in the coking wastewater can be effectively reduced to reach the discharge standard Cr . The application solves the technical problem that the existing coking wastewater treatment effect is poor.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of wastewater treatment, and particularly relates to a coking wastewater treatment process. BACKGROUND

[0002] In recent years, the coking industry has developed rapidly, and the treatment of coking wastewater has gradually become a problem in sewage treatment. Coking wastewater is a kind of industrial wastewater with high disposal difficulty, which is generated in the high-temperature dry distillation of coking and coal gas in the carbonization chamber of the coke oven and in the recovery and condensation process of by-products. It contains volatile phenol, polycyclic aromatic compounds, and heterocyclic compounds containing oxygen, sulfur, and nitrogen. It is a typical wastewater with high COD Cr , high volatile phenol, high ammonia nitrogen, and high cyanide.

[0003] At present, the traditional treatment of coking wastewater generally adopts biochemical treatment method. However, the simple biochemical treatment method can effectively remove volatile phenol and cyanide in coking wastewater, but the removal effect of COD Cr and ammonia nitrogen is poor, which cannot meet the new sewage discharge standard and seriously restricts the development of enterprises. SUMMARY

[0004] The present application provides a coking wastewater treatment process to solve the technical problem of poor treatment effect of coking wastewater.

[0005] Therefore, the present application provides a coking wastewater treatment process, which comprises the following steps:

[0006] S1: pretreating the coking wastewater to obtain pretreated coking wastewater;

[0007] S2: adding a modified carbonized coconut shell adsorbent to the pretreated coking wastewater, mixing uniformly, standing, filtering, and obtaining a first filtrate;

[0008] S3: adjusting the pH value of the first filtrate, adding hydrogen peroxide, mixing uniformly, standing, and performing light irradiation treatment at the same time. After precipitation, filtering is performed to obtain a second filtrate;

[0009] S4: electrochemically oxidizing the second filtrate, standing, and discharging after filtering;

[0010] The modified carbonized coconut shell adsorbent is prepared by modifying carbonized coconut shell with 3,3',4,4'-benzophenonetetracarboxylic dianhydride.

[0011] Further, a coking wastewater treatment process comprises the following steps:

[0012] S1: pretreating the coking wastewater to obtain pretreated coking wastewater;

[0013] S2: adding the modified carbonized coconut shell adsorbent into the pretreated coking wastewater, mixing uniformly, standing for 2-4 hours, filtering to obtain a first filtrate;

[0014] S3: adjusting the pH value of the first filtrate to 4-5 by using a 70% mass fraction sulfuric acid solution, adding hydrogen peroxide, mixing uniformly, standing for 1-2 hours, and performing light irradiation treatment, filtering after precipitation to obtain a second filtrate; wherein the light used for irradiation treatment is ultraviolet light with a wavelength of 250-260 nm and a power of 500-700 w, or an electron beam or other light;

[0015] S4: performing electrochemical oxidation on the second filtrate for 1-2 hours, standing for 1-2 hours, and discharging after filtering;

[0016] The modified carbonized coconut shell adsorbent is prepared by modifying carbonized coconut shell with 3,3',4,4'-benzophenonetetracarboxylic dianhydride; in step S2, 1 m 3 The adding amount of the modified carbonized coconut shell adsorbent in the pretreated coking wastewater is 0.04-0.06 kg; in step S4, 1 m 3 The adding amount of the polyacrylamide in the second filtrate is 0.03-0.05 kg.

[0017] Optionally, the specific steps of the pretreatment in step S1 are as follows: naturally precipitating the coking wastewater, filtering, collecting the filtrate, and performing oil separation treatment on the filtrate to obtain the pretreated coking wastewater.

[0018] Further, the specific steps of the pretreatment in step S1 are as follows: naturally precipitating the coking wastewater for 6-8 hours, filtering, and performing oil separation treatment on the filtered liquid for 80-120 minutes to obtain the pretreated coking wastewater.

[0019] Optionally, the modified carbonized coconut shell adsorbent is prepared by the following method:

[0020] A1: crushing carbonized coconut shell, sieving to obtain crushed carbonized coconut shell;

[0021] A2: putting 3,3',4,4'-benzophenonetetracarboxylic dianhydride into an ethanol solution, mixing uniformly to obtain a mixed solution;

[0022] A3: putting the crushed carbonized coconut shell into the mixed solution, reacting, and performing microwave irradiation, after the reaction is completed, washing, drying to obtain the modified carbonized coconut shell adsorbent.

[0023] Further, the modified carbonized coconut shell adsorbent is prepared by the following method:

[0024] A1: crushing carbonized coconut shell, sieving through an 80-120 mesh sieve to obtain crushed carbonized coconut shell;

[0025] A2: Put 3,3',4,4'-benzophenonetetracarboxylic dianhydride into ethanol solution, mix uniformly to obtain a mixed solution;

[0026] A3: Put the crushed carbonized coconut shell into the mixed solution, react for 1-2h, and irradiate with microwave power of 500-700w for 30-50min, after the reaction is completed, wash with water for 3-5 times, dry to obtain the modified carbonized coconut shell adsorbent;

[0027] Among them, the mass fraction of ethanol solution is 40%, and the addition amount of ethanol solution in 1g of 3,3',4,4'-benzophenonetetracarboxylic dianhydride is 4-6mL.

[0028] Optionally, the weight ratio of the carbonized coconut shell and 3,3',4,4'-benzophenonetetracarboxylic dianhydride is 1:(0.7-1.0).

[0029] Optionally, the carbonized coconut shell is prepared by the following method: crushing the coconut shell, sieving, washing, drying, carbonizing, taking out after the carbonization is completed, and cooling to obtain the carbonized coconut shell.

[0030] Further, the carbonized coconut shell is prepared by the following method: crushing 8-12kg of coconut shell, sieving through a 40-60mesh sieve, washing with water, drying, carbonizing at a temperature of 400-600℃ for 80-120min, taking out after the carbonization is completed, and cooling to 22±3℃ to obtain the carbonized coconut shell.

[0031] Optionally, the coconut shell is further pretreated before use by the following method: placing the coconut shell in a mixed solution of lanthanum nitrate and cerium nitrate, ultrasonic oscillation, heating under the protection of inert gas, incubation, and cooling to obtain the pretreated coconut shell.

[0032] Further, the coconut shell is further pretreated before use by the following method: placing the coconut shell in a mixed solution of lanthanum nitrate and cerium nitrate, ultrasonic oscillation for 20-40min, heating to 80-120℃ under the protection of nitrogen, incubation for 20-40min, and cooling to 22±3℃ to obtain the pretreated coconut shell.

[0033] Among them, the addition amount of coconut shell in 1mL of the mixed solution of lanthanum nitrate and cerium nitrate is 0.2-0.4g.

[0034] Optionally, the concentration ratio of lanthanum nitrate to cerium nitrate in the mixed solution of lanthanum nitrate and cerium nitrate is 1:(0.3-0.5).

[0035] Further, the concentration ratio of lanthanum nitrate to cerium nitrate in the mixed solution of lanthanum nitrate and cerium nitrate is 1:0.4.

[0036] Optionally, the concentration of hydrogen peroxide added in step S3 is 0.2-0.5 L / m 3 .

[0037] Further, the concentration of hydrogen peroxide added in step S3 is 0.4 L / m 3 .

[0038] Optionally, the filtration in step S4 is nanofiltration membrane filtration.

[0039] From the above technical solutions, the embodiments of the present application have the following advantages:

[0040] In the present application, a coking wastewater treatment process is provided, which first pretreats the coking wastewater to remove large particle suspended solids and oil; then uses a modified carbonized coconut shell adsorbent to adsorb COD Cr , ammonia nitrogen and other impurities in the coking wastewater; then adds hydrogen peroxide and performs ultraviolet light irradiation treatment, the hydrogen peroxide generates strong oxidizing hydroxyl radicals under light irradiation, which can efficiently decompose cyanide in the coking wastewater and convert it into low-toxicity or non-toxic substances; after precipitation, electrochemical oxidation is performed, which can further remove ammonia nitrogen and COD, and finally the coking wastewater is discharged after nanofiltration membrane filtration.

[0041] In addition, the modified carbonized coconut shell adsorbent is prepared by modifying the carbonized coconut shell with 3,3',4,4'-benzophenonetetracarboxylic dianhydride, which first uses coconut shell as an adsorbent, realizes waste utilization, saves resources and protects the environment, and secondly, the carbonized coconut shell has a larger surface area and more pore structures due to high-temperature treatment, thus having better adsorption than coconut shell and being able to more effectively remove COD Cr , ammonia nitrogen and other impurities in the coking wastewater; and then the carbonized coconut shell is modified with 3,3',4,4'-benzophenonetetracarboxylic dianhydride, which has carbonyl and hydroxyl groups, and after reaction with the carbonized coconut shell, the carbonyl and hydroxyl groups are introduced onto the carbonized coconut shell, further increasing the surface area and improving the adsorption; and microwave irradiation activation can generate more pore structures, thus doubling the adsorption capacity and facilitating better removal of COD Cr , ammonia nitrogen, volatile phenol and other impurities, so that the coking wastewater meets the discharge standard.

[0042] Furthermore, before use, the coconut shell is modified with a mixed solution of lanthanum nitrate and cerium nitrate, the lanthanum ions and cerium ions can fill in the pores of the coconut shell, significantly increasing the specific surface area of the coconut shell, increasing the mesopores and micropores inside the coconut shell, and thus further improving the adsorption of the coconut shell and the purification effect on the coking wastewater.

[0043] The application provides a coking wastewater treatment process, and aims to solve the technical problem of poor coking wastewater treatment effect. DETAILED DESCRIPTION

[0044] In order to enable the personnel in the technical field to better understand the application scheme, the technical scheme in the embodiments of the application is clearly and completely described below. Obviously, the described embodiments are only some of the embodiments of the application, but not all the embodiments. Based on the embodiments in the application, all other embodiments obtained by the personnel in the field without making creative efforts belong to the protection scope of the application. Unless otherwise specified, the various raw materials, reagents, instruments and equipment and the like used in the application can be purchased from the market or can be prepared by the existing method.

[0045] Preparation Example

[0046] Preparation Example 1

[0047] A carbonized coconut shell is prepared by the following method:

[0048] 10 kg of coconut shell is crushed, washed with water through a 50-mesh sieve, dried, carbonized at a temperature of 500 DEG C for 100 min, taken out after carbonization is completed, and cooled to 25 DEG C to obtain the carbonized coconut shell.

[0049] Preparation Example 2

[0050] A modified carbonized coconut shell adsorbent is prepared by the following method:

[0051] A1: 2 kg of the carbonized coconut shell prepared by the preparation example 1 is crushed through a 100-mesh sieve to obtain the crushed carbonized coconut shell;

[0052] A2: 1.4 kg of 3,3',4,4'-benzophenonetetracarboxylic dianhydride is put into an ethanol solution with a mass fraction of 40%, and mixed uniformly to obtain a mixed solution; wherein the addition amount of the ethanol solution is 5 mL per 1 g of 3,3',4,4'-benzophenonetetracarboxylic dianhydride;

[0053] A3: the crushed carbonized coconut shell is put into the mixed solution, reacted for 1.5 h, and subjected to microwave irradiation with a microwave power of 600 W for 40 min; after the reaction is completed, the modified carbonized coconut shell adsorbent is obtained by washing with water for 5 times and drying.

[0054] Preparation Example 3

[0055] A modified carbonized coconut shell adsorbent, and the difference between the preparation example 2 is that the addition amount of 3,3',4,4'-benzophenonetetracarboxylic dianhydride is different, and the addition amount of 3,3',4,4'-benzophenonetetracarboxylic dianhydride in the preparation example 3 is 1.7 kg.

[0056] Preparation Example 4

[0057] A modified carbonized coconut shell adsorbent, which is different from that of Preparation Example 2 in that the amount of 3,3',4,4'-benzophenonetetracarboxylic dianhydride added is different, and the amount of 3,3',4,4'-benzophenonetetracarboxylic dianhydride added in Preparation Example 4 is 2 kg.

[0058] Preparation Example 5

[0059] A modified carbonized coconut shell adsorbent, which is different from that of Preparation Example 2 in that the amount of 3,3',4,4'-benzophenonetetracarboxylic dianhydride added is different, and the amount of 3,3',4,4'-benzophenonetetracarboxylic dianhydride added in Preparation Example 5 is 0.1 kg.

[0060] Preparation Example 6

[0061] A modified carbonized coconut shell adsorbent, which is different from that of Preparation Example 2 in that the amount of 3,3',4,4'-benzophenonetetracarboxylic dianhydride added is different, and the amount of 3,3',4,4'-benzophenonetetracarboxylic dianhydride added in Preparation Example 6 is 5 kg.

[0062] Example

[0063] Example 1

[0064] A coking wastewater treatment process, comprising the following steps:

[0065] S1: 10 m 3 The coking wastewater is naturally precipitated for 7 h, filtered, and the filtered liquid is subjected to oil separation treatment for 100 min to obtain pretreated coking wastewater;

[0066] S2: The modified carbonized coconut shell adsorbent prepared by Preparation Example 2 is added to the pretreated coking wastewater, mixed uniformly, and allowed to stand for 3 h, filtered to obtain a first filtrate;

[0067] S3: The pH value of the first filtrate is adjusted to 5 with a 70% by mass sulfuric acid solution, hydrogen peroxide is added to a concentration of 0.4 L / m 3 , mixed uniformly, allowed to stand for 1.5 h, and subjected to irradiation treatment with ultraviolet light of a wavelength of 255 nm and a power of 600 w, precipitated, and filtered to obtain a second filtrate;

[0068] S4: The second filtrate is subjected to electrochemical oxidation for 1.5 h, allowed to stand for 1.5 h, and discharged after being filtered by a nanofiltration membrane;

[0069] In step S2, the amount of modified carbonized coconut shell adsorbent added per 1 m 3 The amount of modified carbonized coconut shell adsorbent added to the pretreated coking wastewater is 0.05 kg, and in step S4, the amount of modified carbonized coconut shell adsorbent added per 1 m3 The amount of polyacrylamide added in the second filtrate is 0.04 kg.

[0070] Example 2-5

[0071] A treatment process of coking wastewater, which is different from example 1 in that the source of the modified carbonized coconut shell adsorbent is different, and the modified carbonized coconut shell adsorbent in examples 2-5 is prepared by preparation examples 3-6 respectively.

[0072] Example 6

[0073] A treatment process of coking wastewater, which is different from example 2 in that the coconut shell is further pretreated by the following method before use: the coconut shell is placed in a mixed solution of lanthanum nitrate and cerium nitrate, ultrasonic oscillation for 30 min, heating to 100℃ under the protection of nitrogen, and keeping for 30 min, and cooling to 25℃ to obtain the pretreated coconut shell; wherein the amount of coconut shell added in 1 mL of the mixed solution of lanthanum nitrate and cerium nitrate is 0.3 g, and the concentration ratio of lanthanum nitrate and cerium nitrate in the mixed solution of lanthanum nitrate and cerium nitrate is 1:0.4.

[0074] Comparative example

[0075] Comparative example 1

[0076] A treatment process of coking wastewater, which is different from example 1 in that the modified carbonized coconut shell adsorbent in step S2 is replaced by an equal amount of carbonized coconut shell.

[0077] Comparative example 2

[0078] A treatment process of coking wastewater, which is different from example 1 in that the modified carbonized coconut shell adsorbent in step S2 is replaced by an equal amount of coconut shell.

[0079] Comparative example 3

[0080] A treatment process of coking wastewater, which is different from example 1 in that the modified carbonized coconut shell adsorbent in step S2 is replaced by an equal amount of activated carbon.

[0081] Performance detection test

[0082] The treated coking wastewater in examples 1-6 and comparative examples 1-3 is subjected to the following performance detection:

[0083] COD Cr : The COD in the treated coking wastewater is determined according to HJ828-2017 "Determination of Chemical Oxygen Demand in Water by Dichromate Method", and the detection results are shown in Table 1. Cr

[0084] ​Ammonia nitrogen: ammonia nitrogen in the treated coking wastewater was determined according to HJ535-2009 "Determination of ammonia nitrogen in water by Nessler's reagent spectrophotometry", and the detection results are shown in Table 1.

[0085] Volatile phenol: volatile phenol in the treated coking wastewater was determined according to HJ 503-2009 "Determination of volatile phenol in water by 4-aminoantipyrene spectrophotometry", and the detection results are shown in Table 1.

[0086] Cyanide: cyanide in the treated coking wastewater was determined according to HJ 484-2009 "Determination of cyanide in water by volumetry and spectrophotometry", and the detection results are shown in Table 2.

[0087] Suspended solids: suspended solids in the treated coking wastewater were determined according to GB / T11901-1989 "Determination of suspended solids in water by gravimetric method", and the detection results are shown in Table 2.

[0088] COD in the initial coking wastewater Cr was 2500 mg / L, ammonia nitrogen content was 350 mg / L, volatile phenol content was 20 mg / L, cyanide content was 100 mg / L, and suspended solids content was 3000 mg / L.

[0089] Table 1 detection results

[0090]

[0091] Table 2 detection results

[0092]

[0093]

[0094] It can be seen from Table 1 and Table 2 that the coking wastewater treatment process of the present application effectively reduces the contents of COD Cr , ammonia nitrogen, volatile phenol, cyanide and suspended solids in the coking wastewater through the synergistic effect between the steps, wherein the removal rate of COD Cr is 88.9-98.7%, the removal rate of ammonia nitrogen is 86.7-97.5%, the removal rate of volatile phenol is 90.5-99.3%, the removal rate of cyanide is 88.6-96.9%, and the removal rate of suspended solids is 91.3-99.4%.

[0095] It can be seen from Example 1 and Comparative Examples 1-3 that the COD CrThe removal rate of COD is 95.1%, the removal rate of ammonia nitrogen is 93.9%, the removal rate of volatile phenol is 96.2%, the removal rate of cyanide is 92.1%, and the removal rate of suspended solids is 96.2%, which is better than Comparative Examples 1-3, indicating that the modified carbonized coconut shell adsorbent is more suitable and can improve the removal rates of COD Cr , ammonia nitrogen, volatile phenol, cyanide and suspended solids in coking wastewater.

[0096] As can be seen from Examples 1-5, the removal rate of COD Cr in Example 2 is 97.5%, the removal rate of ammonia nitrogen is 97.3%, the removal rate of volatile phenol is 99.1%, the removal rate of cyanide is 96.5%, and the removal rate of suspended solids is 99.1%, which is better than other examples, indicating that the modified carbonized coconut shell adsorbent prepared by Preparation Example 3 is more suitable, and the addition amount of 3,3',4,4'-benzophenone tetracarboxylic dianhydride in Preparation Example 3 is more suitable, which can improve the removal rates of COD Cr , ammonia nitrogen, volatile phenol, cyanide and suspended solids in coking wastewater.

[0097] As can be seen from Examples 2 and 6, the removal rate of COD Cr in Example 6 is 98.7%, the removal rate of ammonia nitrogen is 97.5%, the removal rate of volatile phenol is 99.3%, the removal rate of cyanide is 96.9%, and the removal rate of suspended solids is 99.4%, which is better than Example 2, indicating that the coconut shell is more suitable for pretreatment before use, which can improve the purification treatment effect of coking wastewater.

[0098] The above examples are only used to illustrate the technical solutions of the present application, but not to limit it; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that they can modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A process for the treatment of coking wastewater, characterized in that, The method comprises the following steps: S1: pretreating coking wastewater to obtain pretreated coking wastewater; S2: adding modified carbonized coconut shell adsorbent to the pretreated coking wastewater, mixing uniformly, standing, filtering, and obtaining a first filtrate; S3: adjusting the pH value of the first filtrate, adding hydrogen peroxide, mixing uniformly, standing, and performing light irradiation treatment at the same time, filtering after precipitation to obtain a second filtrate; S4: performing electrochemical oxidation on the second filtrate, standing, and discharging after filtering; Wherein, the modified carbonized coconut shell adsorbent is 3,3 ’ ,4,4 ’ -benzophenone tetracarboxylic dianhydride modified carbonized coconut shell; The modified carbonized coconut shell adsorbent is prepared by the following method: A1: crushing carbonized coconut shells, sieving, and obtaining crushed carbonized coconut shells; A2: 3,3 ’ ,4,4 ’ benzophenonetetracarboxylic dianhydride was put into an ethanol solution, mixed uniformly to obtain a mixed solution; A3: putting the crushed carbonized coconut shells into a mixed solution, reacting, and performing microwave irradiation, washing and drying after the reaction is completed to obtain the modified carbonized coconut shell adsorbent; The carbonized coconut shell and 3,3 ’ ,4,4 ’ - benzophenone tetra carboxylic dianhydride are in a weight ratio of 1 : (0.7-1.0); The carbonized coconut shells are prepared by the following method: crushing coconut shells, sieving, washing, drying, carbonizing, taking out after the carbonization is completed, cooling, and obtaining the carbonized coconut shells; The coconut shells are further pretreated by the following method before use: putting the coconut shells into a mixed solution of lanthanum nitrate and cerium nitrate, ultrasonic oscillation, heating under the protection of inert gas, heat preservation, cooling, and obtaining pretreated coconut shells; The concentration ratio of lanthanum nitrate to cerium nitrate in the mixed solution of lanthanum nitrate and cerium nitrate is 1: (0.3-0.5).

2. The treatment process of coking wastewater according to claim 1, characterized in that: The specific steps of the pretreatment in step S1 are as follows: naturally precipitating the coking wastewater, filtering, collecting the filtrate, and performing oil separation treatment on the filtrate to obtain the pretreated coking wastewater.

3. The treatment process of coking effluents according to claim 1, characterized in that: The concentration of hydrogen peroxide added in step S3 is 0.2-0.5 L / m 3 .

4. The treatment process of coking effluent as claimed in claim 1 wherein: The filtering in step S4 is nanofiltration membrane filtering.

Images