Recovery treatment method of pickling waste liquid for steel surface treatment

Abstract

The invention relates to a steel surface treatment pickling waste liquid recovery treatment method, and belongs to the technical field of steel pickling waste liquid treatment. The method comprises the following steps: adding hydrochloric acid into the pickling waste liquid to adjust the pH value, introducing oxygen and a catalyst, adding a modified adsorbent, stirring, evaporating and concentrating, adding a stabilizer into a concentrated solution, dropwise adding hydrochloric acid to adjust the pH value to generate polyferric chloride colloid, diluting the polyferric chloride colloid, and filtering to remove impurities to obtain a liquid polyferric chloride product. By optimizing oxidation, evaporation concentration and polymerization reaction processes, efficient recovery of waste acid is achieved, high-purity polyferric chloride is prepared, an iron oxide-carbon composite material oxidation catalyst is prepared from ferric salt and graphene, the catalytic efficiency is improved, mesoporous silica is modified by adopting sulfydryl and amino jointly, and high-purity polyferric chloride is obtained. High-selectivity adsorption on heavy metal under the low-pH condition is achieved, the pickling waste liquid generated in the steel surface treatment process is effectively treated, environmental pollution is reduced, polyferric chloride with the high additional value is recycled and generated, and cyclic utilization of resources is achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of steel pickling waste liquid recovery, and relates to a method for recovering and treating pickling waste liquid for steel surface treatment. Background Art

[0002] During the hot rolling, forging or long-term storage of steel, a dense iron oxide scale will form on the surface, which not only affects the mechanical properties and appearance quality of the steel, but also hinders the adhesion of subsequent processing (such as electroplating, painting). Therefore, pickling has become a key process for steel surface treatment. Usually, hydrochloric acid or sulfuric acid is used to dissolve the oxide layer to restore the cleanliness and activity of the metal matrix. The pickled steel surface is smooth and free of impurities, which can meet the strict requirements of the automotive manufacturing, building structure, machining and other industries for material properties. However, during the pickling process, a large amount of free acid and metal ions enter the waste liquid, forming a mixed system of high-concentration hydrochloric acid and heavy metals. If directly discharged, it will seriously pollute the water and soil environment, and there is an urgent need for efficient recovery and resource treatment.

[0003] Existing pickling waste liquid treatment technologies: The neutralization method adjusts the pH to neutral by adding lime or sodium hydroxide, so that metal ions form hydroxide precipitates, but it consumes a large amount of alkali agents and produces sludge with high water content (containing Fe(OH) 3 、Cr(OH) 3 etc.), with high treatment costs and no resource recovery; The evaporation method recovers hydrochloric acid by heating and concentrating the waste liquid, but the energy consumption is huge, and the high temperature leads to increased equipment corrosion. The heavy metals remaining in the concentrated liquid still need secondary treatment; The roasting method decomposes the waste liquid at high temperature (800 - 1000 °C). Although HCl gas can be recovered, it will produce toxic gases such as Cl 2 、dioxins, etc., and the tail gas treatment is complex and does not meet the requirements of green processes. In addition, although the existing redox method can partially recover Fe 3+ , there are problems such as slow reaction rate, high catalyst cost, and difficulty in controlling the basicity of the product, resulting in unstable quality of polyferric chloride.

[0004] Therefore, a process integrating efficient heavy metal separation, low-energy consumption oxidation and high-value product co-production is developed. The recovery value of pickling waste liquid is mainly reflected in hydrochloric acid regeneration and comprehensive utilization of metal components. Taking polyferric chloride as an example, as an efficient inorganic coagulant, it is widely used in the fields of municipal sewage and industrial wastewater treatment. The traditional process prepares polyferric chloride by oxidizing the waste liquid, followed by concentration, polymerization and other steps, converting metal ions into high-value-added products to achieve "treating waste with waste". However, this process needs to overcome technical difficulties such as interference of heavy metal impurities, low oxidation efficiency, and poor product stability. For example, if heavy metals such as residual Cr 3+ 、Zn 2+ in the waste liquid are not effectively removed, they will affect the purity and coagulation performance of polyferric chloride; Fe 2+ is oxidized to Fe3+ The rate and completeness directly determine the effect of the subsequent polymerization reaction, and the efficiency needs to be improved by optimizing the type of oxidant, reaction conditions, etc. Summary of the Invention

[0005] The present invention relates to a method for recycling and treating pickling waste liquid on the surface of steel, belonging to the technical field of steel pickling waste liquid treatment. The present invention realizes the efficient recovery of waste acid and the preparation of high-purity polyferric chloride by optimizing the processes of oxidation, evaporation concentration and polymerization reaction. An iron oxide-carbon composite oxidation catalyst is prepared by using iron salt and graphene to improve the catalytic efficiency; mesoporous silica is modified by mercapto and amino groups to achieve high-selectivity adsorption of heavy metals under low pH conditions. It not only effectively treats the pickling waste liquid generated in the process of steel surface treatment, avoids environmental pollution, but also realizes the recycling of resources by recovering and generating polyferric chloride with high added value.

[0006] The object of the present invention can be achieved by the following technical solutions:

[0007] A method for recycling and treating pickling waste liquid on the surface of steel, comprising the following steps:

[0008] (1) Adjust the pickling waste liquid on the surface of steel to pH 1.5 - 2.0 by adding hydrochloric acid;

[0009] (2) Introduce oxygen and catalyst, control the oxidation-reduction potential to 650 - 680 mV, and oxidize for 2 - 4 h at a temperature of 60 - 80 °C;

[0010] (3) Add a modified adsorbent and stir evenly, and remove the adsorbed heavy metal ions by filtration;

[0011] (4) Perform evaporation concentration under reduced pressure, transport the condensate to the sewage treatment plant, and concentrate the concentrated liquid until the concentration of Fe 3+ reaches 10 - 16%;

[0012] (5) Add a stabilizer to the concentrated liquid, dropwise add hydrochloric acid to adjust the pH to 1.0 - 1.5, and stir at 50 - 60 °C for 1 - 2 h to generate polyferric chloride colloid;

[0013] (6) Dilute the polyferric chloride colloid to 10 - 12%, and obtain a liquid polyferric chloride product after filtering to remove impurities.

[0014] As a preferred technical solution of the present invention, the addition amount of the catalyst in step (2) is 1 - 5 g / L; the preparation steps of the catalyst are:

[0015] A1. Dissolve the iron salt in deionized water, stir evenly to obtain an iron salt solution;

[0016] A2. Disperse graphene in deionized water and perform ultrasonic treatment for 20 - 40 min to obtain a dispersion;

[0017] A3. Dropwise add an iron salt solution to the dispersion and continuously stir to ensure uniform mixing;

[0018] A4. Add sodium hydroxide to adjust the pH to 7 - 9 to form a precipitate of iron oxide precursor, heat to 80 - 90 °C, and keep warm for 2 - 4 h to promote the formation and crystallization of iron oxide;

[0019] A6. Filter and wash the reacted mixture, and dry it at 60 - 80 °C for 10 - 14 h to obtain a dried iron oxide - carbon precursor;

[0020] A7. Calcinate the dried precursor in an inert atmosphere at a temperature controlled at 300 - 500 °C for 2 - 3 h to form an iron oxide - carbon composite catalyst.

[0021] As a preferred technical solution of the present invention, the iron salt described in step A1 is FeCl 3 or Fe(NO 3 ) 3 , with a concentration of 0.1 - 0.3 M; the ratio of graphene to deionized water described in step A2 is 0.1 - 1.0 g / L.

[0022] As a preferred technical solution of the present invention, the mass ratio of the iron salt solution to the dispersion described in step A3 is 1:0.2 - 0.5.

[0023] As a preferred technical solution of the present invention, the inert gas described in step A7 is nitrogen or argon.

[0024] As a preferred technical solution of the present invention, the preparation method of the modified adsorbent described in step (3) is: disperse mesoporous silica in 1 M HCl solution, stir at 80 °C for 6 h for activation, then wash and dry, and then disperse it in toluene, perform ultrasonic treatment for 30 min, add 3 - aminopropyltriethoxysilane and 3 - mercaptopropyltrimethoxysilane, under nitrogen protection, reflux and stir at 110 °C for 24 h, and obtain the modified adsorbent after centrifugal washing and vacuum drying at 60 °C for 6 h.

[0025] As a preferred technical solution of the present invention, the mass ratio of silica, HCl solution, toluene, 3 - aminopropyltriethoxysilane, and 3 - mercaptopropyltrimethoxysilane is 1:40 - 50:80 - 100:0.5 - 0.7:0.1 - 0.3.

[0026] As a preferred technical solution of the present invention, the pressure under reduced pressure described in step (4) is: - 0.08 ~ - 0.06 MPa; the evaporation and concentration temperature is 70 - 90 °C.

[0027] As a preferred technical solution of the present invention, the stabilizer in step (5) is any one of disodium hydrogen phosphate, sodium citrate, polyvinyl alcohol, polyacrylic acid, and glycine.

[0028] Advantages of the present invention:

[0029] (1) The present invention strictly controls the pH value of the pickling waste liquid, the precise redox potential, vacuum evaporation and concentration, uses a highly efficient catalyst for low-energy consumption and high-efficiency oxidation, uses a stabilizer, and through the preparation of a bifunctional group synergistic coordination adsorbent, realizes the efficient recovery of waste acid and the preparation of high-purity polyferric chloride.

[0030] (2) By using iron salts and graphene to prepare an iron oxide-carbon composite oxidation catalyst to improve the catalytic efficiency, and modifying mesoporous silica with 3-aminopropyltriethoxysilane and 3-mercaptopropyltrimethoxysilane to form thiol and amino bidentate coordination, enhancing the binding stability of heavy metal ions. Fe 3+ Due to its high charge density and strong hydration effect, it is difficult to simultaneously satisfy the matching of the double coordination sites, resulting in adsorption hindrance, and then adsorbing and removing heavy metals, ensuring the purity of polyferric chloride, replacing traditional agents such as aluminum sulfate, reducing the sewage treatment cost, and realizing the circular economy model of "treating waste with waste" for waste acid. Specific embodiments

[0031] To further illustrate the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the following examples are provided to detail the specific embodiments, structures, features, and their effects according to the present invention.

[0032] Example 1

[0033] A method for recycling and treating pickling waste liquid from steel surface treatment, comprising the following steps:

[0034] (1) Adjust the pickling waste liquid from steel surface treatment to a pH of 1.8 by adding hydrochloric acid;

[0035] (2) Introduce oxygen and a catalyst, control the redox potential to 665 mV, and oxidize at a temperature of 70 °C for 3 h;

[0036] (3) Add the modified adsorbent and stir evenly, and remove the adsorbed heavy metal ions by filtration;

[0037] (4) Perform evaporation and concentration under reduced pressure, transport the condensate to the sewage treatment plant, and concentrate the concentrated liquid until the concentration of Fe 3+ reaches 14%;

[0038] (5) Add a stabilizer to the concentrated liquid, dropwise add hydrochloric acid to adjust the pH to 1.2, and stir at 55 °C for 1.5 h to generate polyferric chloride colloid;

[0039] (6) Dilute the polyferric chloride colloid to 13%, and obtain the liquid polyferric chloride product after filtering to remove impurities.

[0040] The addition amount of the catalyst described in step (2) is 1 - 5 g / L; the preparation steps of the catalyst are as follows:

[0041] A1. Dissolve the iron salt in deionized water and stir evenly to obtain an iron salt solution;

[0042] A2. Disperse the graphene in deionized water and perform ultrasonic treatment for 30 min to obtain a dispersion;

[0043] A3. Drop the iron salt solution into the dispersion and continuously stir to ensure uniform mixing;

[0044] A4. Add sodium hydroxide to adjust the pH to 8, form a precipitate of iron oxide precursor, heat to 85 °C, and keep warm for 3 h to promote the formation and crystallization of iron oxide;

[0045] A6. Filter and wash the reacted mixture, and dry it at 70 °C for 12 h to obtain a dry iron oxide-carbon precursor;

[0046] A7. Calcinate the dried precursor in an inert atmosphere at a temperature controlled at 400 °C for 2.5 h to form an iron oxide-carbon composite catalyst.

[0047] The iron salt described in step A1 is FeCl 3 , with a concentration of 0.2 M; the ratio of graphene to deionized water described in step A2 is 0.5 g / L.

[0048] The mass ratio of the iron salt solution to the dispersion described in step A3 is 1:0.4.

[0049] The inert gas described in step A7 is nitrogen.

[0050] The preparation method of the modified adsorbent described in step (3) is as follows: Disperse the mesoporous silica in a 1 M HCl solution, stir at 80 °C for 6 h for activation, then wash and dry, and then disperse it in toluene, perform ultrasonic treatment for 30 min, add 3-aminopropyltriethoxysilane and 3-mercaptopropyltrimethoxysilane, under nitrogen protection, reflux and stir at 110 °C for 24 h, centrifuge and wash, and then vacuum dry at 60 °C for 6 h to obtain the modified adsorbent.

[0051] The mass ratio of the silica, HCl solution, toluene, 3-aminopropyltriethoxysilane, and 3-mercaptopropyltrimethoxysilane is 1:45:90:0.6:0.4.

[0052] The pressure under reduced pressure described in step (4) is: -0.07 MPa; the evaporation and concentration temperature is 80 °C.

[0053] The stabilizer described in step (5) is disodium hydrogen phosphate.

[0054] Example 2

[0055] A method for recycling and treating pickling waste liquid on the surface of steel, comprising the following steps:

[0056] (1) Adjust the pickling waste liquid on the surface of steel to pH 1.5 by adding hydrochloric acid.

[0057] (2) Introduce oxygen and a catalyst, control the oxidation-reduction potential to 650 mV, and oxidize for 2 h at a temperature of 60 °C.

[0058] (3) Add a modified adsorbent and stir evenly, and remove the adsorbed heavy metal ions by filtration.

[0059] (4) Perform evaporation and concentration under reduced pressure, convey the condensate to a sewage treatment plant, and concentrate the concentrated liquid until the concentration of Fe 3+ reaches 10%.

[0060] (5) Add a stabilizer to the concentrated liquid, dropwise add hydrochloric acid to adjust the pH to 1.0, stir at 50 °C for 1 h to form polyferric chloride colloid.

[0061] (6) Dilute the polyferric chloride colloid to 10%, filter to remove impurities, and obtain a liquid polyferric chloride product.

[0062] The addition amount of the catalyst described in step (2) is 1-5 g / L; the preparation steps of the catalyst are as follows:

[0063] A1. Dissolve iron salt in deionized water and stir evenly to obtain an iron salt solution.

[0064] A2. Disperse graphene in deionized water and perform ultrasonic treatment for 20 min to obtain a dispersion.

[0065] A3. Drop the iron salt solution into the dispersion and continuously stir to ensure uniform mixing.

[0066] A4. Add sodium hydroxide to adjust the pH to 7 to form a precipitate of iron oxide precursor, heat to 80 °C, and keep warm for 2 h to promote the formation and crystallization of iron oxide.

[0067] A6. Filter and wash the reacted mixture, and dry at 60 °C for 10 h to obtain a dried iron oxide-carbon precursor.

[0068] A7. Calcinate the dried precursor in an inert atmosphere at a temperature controlled at 300 °C for 2 h to form an iron oxide-carbon composite catalyst.

[0069] The iron salt Fe(NO 3 ) 3 in step A1 has a concentration of 0.1 M; the ratio of graphene to deionized water in step A2 is 0.1 g / L.

[0070] The mass ratio of the iron salt solution to the dispersion liquid in step A3 is 1:0.2.

[0071] The inert gas in step A7 is argon.

[0072] The preparation method of the modified adsorbent in step (3) is as follows: disperse mesoporous silica in 1 M HCl solution, stir at 80 °C for 6 h for activation, then wash and dry. Then disperse it in toluene, sonicate for 30 min, add 3-aminopropyltriethoxysilane and 3-mercaptopropyltrimethoxysilane, reflux and stir at 110 °C for 24 h under nitrogen protection, and vacuum dry at 60 °C for 6 h after centrifugal washing to obtain the modified adsorbent.

[0073] The mass ratio of the silica, HCl solution, toluene, 3-aminopropyltriethoxysilane, and 3-mercaptopropyltrimethoxysilane is 1:40:80:0.5:0.3.

[0074] The pressure under reduced pressure in step (4) is: -0.08 MPa; the evaporation and concentration temperature is 70 °C.

[0075] The stabilizer in step (5) is sodium citrate.

[0076] Example 3

[0077] A method for recycling and treating pickling waste liquid from steel surface treatment, comprising the following steps:

[0078] (1) Adjust the pickling waste liquid from steel surface treatment to pH 2.0 by adding hydrochloric acid;

[0079] (2) Introduce oxygen and a catalyst, control the oxidation-reduction potential to 680 mV, and oxidize at 80 °C for 4 h;

[0080] (3) Add the modified adsorbent and stir evenly, and remove the adsorbed heavy metal ions by filtration;

[0081] (4) Perform evaporation and concentration under reduced pressure, convey the condensate to the sewage treatment plant, and concentrate the concentrated liquid until the concentration of Fe 3+ reaches 16%;

[0082] (5) Add a stabilizer to the concentrated liquid, dropwise add hydrochloric acid to adjust the pH to 1.5, and stir at 60 °C for 2 h to generate polyferric chloride colloid;

[0083] (6) Dilute the polyferric chloride colloid to 12%, filter to remove impurities, and obtain a liquid polyferric chloride product.

[0084] The catalyst addition amount described in step (2) is 1 - 5 g / L; the preparation steps of the catalyst are as follows:

[0085] A1. Dissolve the iron salt in deionized water and stir evenly to obtain an iron salt solution;

[0086] A2. Disperse graphene in deionized water and perform ultrasonic treatment for 40 min to obtain a dispersion;

[0087] A3. Drop the iron salt solution into the dispersion and continuously stir to ensure uniform mixing;

[0088] A4. Add sodium hydroxide to adjust the pH to 9, form a precipitate of iron oxide precursor, heat to 90 °C, and keep warm for 4 h to promote the formation and crystallization of iron oxide;

[0089] A6. Filter and wash the reacted mixture, and dry it at 80 °C for 14 h to obtain a dried iron oxide-carbon precursor;

[0090] A7. Calcinate the dried precursor in an inert atmosphere at a temperature controlled at 500 °C for 3 h to form an iron oxide-carbon composite catalyst.

[0091] The iron salt described in step A1 is FeCl 3 , with a concentration of 0.3 M; the ratio of graphene to deionized water described in step A2 is 1.0 g / L.

[0092] The mass ratio of the iron salt solution to the dispersion described in step A3 is 1:0.5.

[0093] The inert gas described in step A7 is nitrogen.

[0094] The preparation method of the modified adsorbent described in step (3) is as follows: Disperse mesoporous silica in 1 M HCl solution, stir at 80 °C for 6 h for activation, then wash and dry, and then disperse it in toluene, perform ultrasonic treatment for 30 min, add 3-aminopropyltriethoxysilane and 3-mercaptopropyltrimethoxysilane, under nitrogen protection, reflux and stir at 110 °C for 24 h, and obtain the modified adsorbent after centrifugal washing and vacuum drying at 60 °C for 6 h.

[0095] The mass ratio of the silica, HCl solution, toluene, 3-aminopropyltriethoxysilane, and 3-mercaptopropyltrimethoxysilane is 1:50:100:0.7:0.5.

[0096] The pressure under reduced pressure described in step (4) is: -0.06 MPa; the evaporation and concentration temperature is 90 °C.

[0097] The stabilizer described in step (5) is polyvinyl alcohol.

[0098] Example 4

[0099] A method for recycling and treating pickling waste liquid on the surface of steel includes the following steps:

[0100] (1) Adjust the pickling waste liquid on the surface of steel to pH 1.7 by adding hydrochloric acid;

[0101] (2) Introduce oxygen and a catalyst, control the oxidation-reduction potential to 660 mV, and oxidize for 3 h at a temperature of 65 °C;

[0102] (3) Add a modified adsorbent and stir evenly, and remove the adsorbed heavy metal ions by filtration;

[0103] (4) Conduct evaporation and concentration under reduced pressure, transport the condensate to a sewage treatment plant, and concentrate the concentrated liquid until the concentration of Fe 3+ reaches 14%;

[0104] (5) Add a stabilizer to the concentrated liquid, dropwise add hydrochloric acid to adjust the pH to 1.2, stir at 52 °C for 1 h to generate polyferric chloride colloid;

[0105] (6) Dilute the polyferric chloride colloid to 10%, filter to remove impurities, and obtain a liquid polyferric chloride product.

[0106] The addition amount of the catalyst described in step (2) is 1-5 g / L; the preparation steps of the catalyst are as follows:

[0107] A1. Dissolve iron salt in deionized water, stir evenly to obtain an iron salt solution;

[0108] A2. Disperse graphene in deionized water and perform ultrasonic treatment for 25 min to obtain a dispersion;

[0109] A3. Drop the iron salt solution into the dispersion, continuously stir to ensure uniform mixing;

[0110] A4. Add sodium hydroxide, adjust the pH to 7 to form a precipitate of iron oxide precursor, heat to 82 °C, and keep warm for 2 h to promote the formation and crystallization of iron oxide;

[0111] A6. Filter and wash the reacted mixture, and dry at 65 °C for 13 h to obtain a dried iron oxide-carbon precursor;

[0112] A7. Calcinate the dried precursor in an inert atmosphere, control the temperature at 350 °C, and calcinate for 2 h to form an iron oxide-carbon composite catalyst.

[0113] The iron salt described in step A1 is Fe(NO 3 ) 3, the concentration is 0.3 M; the ratio of the graphene to deionized water described in step A2 is 0.8 g / L.

[0114] The mass ratio of the iron salt solution and the dispersion liquid described in step A3 is 1:0.3.

[0115] The inert gas described in step A7 is argon.

[0116] The preparation method of the modified adsorbent described in step (3) is as follows: disperse mesoporous silica in 1 M HCl solution, stir at 80 °C for 6 h for activation, then wash and dry, disperse in toluene, ultrasonic for 30 min, add 3-aminopropyltriethoxysilane and 3-mercaptopropyltrimethoxysilane, under nitrogen protection, reflux and stir at 110 °C for 24 h, centrifuge and wash, and then vacuum dry at 60 °C for 6 h to obtain the modified adsorbent.

[0117] The mass ratio of the silica, HCl solution, toluene, 3-aminopropyltriethoxysilane, and 3-mercaptopropyltrimethoxysilane is 1:40:100:0.5:0.4.

[0118] The pressure under reduced pressure described in step (4) is: -0.08 MPa; the evaporation and concentration temperature is 75 °C.

[0119] The stabilizer described in step (5) is glycine.

[0120] Comparative Example 1

[0121] On the basis of Example 1, the catalyst uses an equal amount of FeCl 3 , and the rest is the same as Example 1.

[0122] Comparative Example 2

[0123] On the basis of Example 2, the catalyst uses an equal amount of Fe(NO 3 ) 3 , and the rest is the same as Example 2.

[0124] Comparative Example 3

[0125] On the basis of Example 1, the modified adsorbent does not add 3-aminopropyltriethoxysilane, and the mass ratio of silica to 3-mercaptopropyltrimethoxysilane is changed to 1:1, and the rest is the same as Example 1.

[0126] Comparative Example 4

[0127] On the basis of Example 1, the modified adsorbent does not add 3-mercaptopropyltrimethoxysilane, and the mass ratio of silica to 3-aminopropyltriethoxysilane is changed to 1:1, and the rest is the same as Example 1.

[0128] Comparative Example 5

[0129] On the basis of Example 1, the heavy metal adsorption in step (3) is not carried out, and the rest is the same as in Example 1.

[0130] Performance test:

[0131] After detection and analysis, the contents of various raw materials generated in the pickling waste liquid are as shown in Table 1 below:

[0132] Table 1 Contents of various raw materials generated in the pickling waste liquid

[0133] Fe / % <![CDATA[Fe 2+ / %]]> <![CDATA[H 2 SO 4 / %]]> HCl / % Cu / ppm Ni / ppm Zn / ppm 4.0 3.95 15.0 5.0 35 42 85

[0134] The total iron content, ferrous chloride content, basicity, and yield of Examples 1-4 and Comparative Examples 1-2 were detected according to the method of HG / T 4672-2022 "Water treatment agent - Polychlorinated iron", and the results are shown in Table 2.

[0135] Table 2 Total iron content, ferrous chloride content, basicity, and yield of Examples 1-4 and Comparative Examples 1-2

[0136]

[0137] Table 3 Heavy metal content detection results of Examples 1-3 and Comparative Examples 3-5

[0138] Cu / ppm Ni / ppm Zn / ppm Example 1 0.31 0.39 0.75 Example 2 0.32 0.41 0.81 Example 3 0.35 0.42 0.82 Comparative Example 3 1.71 3.65 8.14 Comparative Example 4 5.21 6.45 10.59 Comparative Example 5 12.54 18.75 43.94

[0139] From the results of the total iron content, ferrous chloride content, basicity, and yield of Examples 1-4 and Comparative Examples 3-5, it can be seen that the present invention prepares an iron oxide-carbon composite oxidation catalyst by using iron salt and graphene, improving the catalytic efficiency; by comparing the heavy metal content detection results of Examples 1-4 and Comparative Examples 3-5, it can be seen that the present invention modifies mesoporous silica with 3-aminopropyltriethoxysilane and 3-mercaptopropyltrimethoxysilane to form thiol and amino bidentate coordination, enhancing the binding stability of heavy metal ions. Fe 3+ Due to its high charge density and strong hydration effect, it is difficult to simultaneously meet the matching of the double coordination sites, resulting in adsorption hindrance, and then adsorbing and removing heavy metals, realizing the efficient recovery of waste acid and the preparation of high-purity polychlorinated iron.

[0140] The above is only a preferred embodiment of the present invention, and it does not impose any form of limitation on the present invention. Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or equivalent changes within the scope of the technical solution of the present invention by using the above-disclosed technical content. However, as long as it does not depart from the technical solution content of the present invention, any indirect modification, equivalent change, and modification made to the above embodiments based on the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A method for recycling pickling waste liquid from steel surface treatment, characterized in that: The following steps are involved: (1) adding hydrochloric acid to the steel surface treatment pickling waste liquid to adjust the pH to 1.5-2.0; (2) introducing oxygen and catalyst, controlling the redox potential to 650-680 mV, and oxidizing at a temperature of 60-80° C. for 2-4 h; (3) adding the modified adsorbent and stirring evenly, and removing the adsorbed heavy metal ions by filtering; (4) Evaporation and concentration are carried out under reduced pressure, and the condensate is transported to a sewage treatment plant, and the concentrate is concentrated to Fe 3+ The concentration reaches 10-16%; (5) adding a stabilizer to the concentrate, adding hydrochloric acid dropwise to adjust the pH to 1.0-1.5, stirring at 50-60° C. for 1-2 hours to generate polyferric chloride colloid; (6) diluting the polyferric chloride colloid to 10-12%, filtering and removing impurities to obtain a liquid polyferric chloride product.

2. The method for recycling steel surface treatment pickling waste liquid according to claim 1, characterized in that: The catalyst addition amount in step (2) is 1-5 g / L; the catalyst preparation steps are: A1. Dissolve the iron salt in deionized water and stir evenly to obtain an iron salt solution; A2, dispersing graphene in deionized water, and ultrasonically treating for 20-40 min to obtain a dispersion; A3. Add the iron salt solution dropwise into the dispersion and continue stirring to ensure uniform mixing; A4, adding sodium hydroxide, adjusting the pH to 7-9, forming an iron oxide precursor precipitate, heating to 80-90°C, and keeping warm for 2-4 hours to promote the formation and crystallization of iron oxide; A6. Filter and wash the reaction mixture, and dry it at 60-80° C. for 10-14 h to obtain a dry iron oxide-carbon precursor; A7. Calcine the dried precursor in an inert atmosphere at a temperature of 300-500° C. for 2-3 hours to form an iron oxide-carbon composite catalyst.

3. The method for recycling steel surface treatment pickling waste liquid according to claim 2, characterized in that: The iron salt in step A1 is FeCl3 or Fe(NO3)3, and the concentration is 0.1-0.3M; the ratio of graphene to deionized water in step A2 is 0.1-1.0g / L.

4. The method for recycling steel surface treatment pickling waste liquid according to claim 2, characterized in that: The mass ratio of the iron salt solution to the dispersion in step A3 is 1:0.2-0.

5.

5. The method for recycling steel surface treatment pickling waste liquid according to claim 2, characterized in that: The inert gas in step A7 is nitrogen or argon.

6. The method for recycling steel surface treatment pickling waste liquid according to claim 1, characterized in that: The preparation method of the modified adsorbent in step (3) is as follows: dispersing mesoporous silica in 1M HCl solution, stirring at 80°C for 6 hours to activate, washing and drying, then dispersing in toluene, ultrasonicating for 30 minutes, adding 3-aminopropyltriethoxysilane and 3-mercaptopropyltrimethoxysilane, and refluxing at 110°C for 24 hours under nitrogen protection. After centrifugal washing, vacuum drying at 60°C for 6 hours is obtained to obtain the modified adsorbent.

7. The method for recycling steel surface treatment pickling waste liquid according to claim 6, characterized in that: The mass ratio of the silicon dioxide, the HCl solution, the toluene, the 3-aminopropyltriethoxysilane and the 3-mercaptopropyltrimethoxysilane is 1:40-50:80-100:0.5-0.7:0.3-0.

5.

8. The method for recycling steel surface treatment pickling waste liquid according to claim 1, characterized in that: The pressure under reduced pressure conditions in step (4) is: -0.08 to -0.06 MPa; and the evaporation concentration temperature is 70-90°C.

9. The method for recycling steel surface treatment pickling waste liquid according to claim 1, characterized in that: The stabilizer in step (5) is any one of disodium hydrogen phosphate, sodium citrate, polyvinyl alcohol, polyacrylic acid, and glycine.

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