Method for treating pickling wastewater

Abstract

The invention discloses a pickling wastewater treatment method, and relates to the technical field of pickling wastewater treatment, and the pickling wastewater treatment method comprises the following steps: removing impurities from pickling wastewater, flocculating, then simultaneously injecting a hydrogen peroxide solution and ozone into a first reaction tower filled with a recrystallized silicon carbide honeycomb ceramic carrier, and carrying out oxidation treatment for 30-60 minutes; introducing the wastewater into a second reaction tower of a recrystallized silicon carbide honeycomb ceramic carrier internally loaded with nano zero-valent iron, and treating at 30-40 DEG C for 35-45 minutes to obtain primary qualified wastewater; enabling the wastewater to sequentially flow through three-stage series recrystallization silicon carbide honeycomb ceramic carrier adsorption columns to obtain deeply treated wastewater; standing and precipitating, and filtering supernate through a ceramic membrane filter. The pickling wastewater treatment method can effectively remove COD and heavy metal ions in the pickling wastewater.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of pickling wastewater treatment, and more particularly relates to a pickling wastewater treatment method. BACKGROUND

[0002] In industrial production, pickling process is often used in metal surface treatment, electroplating, steel rolling and other processes to remove oxide layer, rust and impurities. The resulting pickling wastewater has complex composition, containing high-concentration acidic substances such as hydrochloric acid, sulfuric acid and hydrofluoric acid, heavy metal ions such as chromium, nickel and zinc, fluoride and a small amount of organic additives such as corrosion inhibitors and surfactants. These substances have strong corrosive and biological toxicity. If directly discharged, it will seriously pollute water bodies and soil, destroy the ecological balance, and cause waste of acid resources and metal resources.

[0003] At present, the treatment methods of pickling wastewater mainly include chemical neutralization method, membrane separation method, ion exchange method and adsorption method. The chemical neutralization method adjusts the pH value by adding alkaline reagents to make heavy metal ions form hydroxide precipitate. This method is simple to operate, but it consumes a large amount of reagents, produces a large amount of sludge which is difficult to dewater, and easy to cause secondary pollution in subsequent disposal, and cannot realize the recovery of acid resources. The membrane separation method can realize the separation and recovery of acid and heavy metals, but the membrane material is easily corroded by strong acid and blocked by particulate matter, has short service life, high operation cost, and strict requirements on the water quality of the influent, which requires complex pretreatment process. The ion exchange method uses resin to adsorb heavy metal ions, which can achieve a certain purification effect, but the resin has poor stability under strong acidic conditions and is easy to fail, and a large amount of chemical reagents are consumed in the regeneration process, and the removal effect of fluoride is limited.

[0004] Adsorption method is widely studied due to its simple operation and low cost. Common adsorption materials include activated carbon, zeolite, biomass carbon, etc. However, activated carbon is easily damaged in strong acid environment, and its adsorption capacity decreases rapidly with the increase of use frequency; zeolite has good acid resistance, but its specific surface area is small and its selective adsorption capacity for heavy metals is insufficient; biomass carbon has low mechanical strength and is easy to dissolve organic pollutants, which limits its long-term application in pickling wastewater treatment.

[0005] In recent years, silicon carbide material has gradually attracted attention in wastewater treatment field due to its excellent corrosion resistance, high thermal stability and mechanical strength. In the prior art, silicon carbide is mainly used in the form of membrane assembly or particles for water quality filtration, mainly relying on physical interception to separate suspended particulate matter, but its potential in adsorbing heavy metal ions, catalyzing degradation of organic pollutants and synergistic recovery of acid resources has not been fully tapped. At the same time, the application of existing silicon carbide material is limited to a single treatment link, and cannot form effective synergy with other processes, resulting in low overall treatment efficiency and difficulty in meeting the dual demands of pickling wastewater deep purification and resource recovery. SUMMARY

[0006] Based on this, the application provides a pickling wastewater treatment method, which overcomes the defects that the above-mentioned silicon carbide is mainly used for water quality filtration in the form of a membrane assembly or a particle, mainly relies on physical interception to separate suspended particulate matters, and the potential of the silicon carbide in adsorbing heavy metal ions, catalyzing degradation of organic pollutants and synergistic recovery of acid resources has not been fully tapped, and the application of the existing silicon carbide material is limited to a single treatment link, and cannot form effective synergy with other processes, resulting in low overall treatment efficiency and difficulty in meeting the dual needs of deep purification and resource recovery of pickling wastewater.

[0007] In order to achieve the above-mentioned purpose, the application adopts the following technical solutions: The application provides a pickling wastewater treatment method, which comprises the following steps: Step one, pretreatment: first remove impurities from the pickling wastewater, and then flocculate to obtain pretreated wastewater; Step two, catalytic oxidation: simultaneously inject the pretreated wastewater, a hydrogen peroxide solution and ozone into a first reaction tower internally filled with a recrystallized silicon carbide honeycomb ceramic carrier, oxidize for 30-60 minutes to obtain oxidized wastewater; Step three, heavy metal treatment: pass the oxidized wastewater into a second reaction tower internally loaded with a recrystallized silicon carbide honeycomb ceramic carrier loaded with nano zero-valent iron, treat at 30-40 DEG C for 35-45 minutes to obtain primary qualified wastewater; Step four, deep purification: make the primary qualified wastewater flow through three series-connected recrystallized silicon carbide honeycomb ceramic carrier adsorption columns in sequence to obtain deep treated wastewater; Step five, terminal treatment: make the deep treated wastewater stand for sedimentation, and filter the supernatant through a ceramic membrane filter.

[0008] The prior art mostly adopts a single treatment method or a simple combination, such as only using a chemical neutralization method to produce a large amount of sludge, and only using a membrane separation method to have high cost and the membrane is easy to be damaged. The present application organically combines multiple treatment processes to form a complete treatment system, each step is targeted and the treatment effect is more comprehensive. The present application realizes efficient purification of pickling wastewater through the synergistic cooperation of the five steps of pretreatment, catalytic oxidation, heavy metal treatment, deep purification and terminal treatment, which can not only remove large particle impurities, reduce the COD content, remove heavy metal ions, but also make the effluent water quality stable and meet the standard through deep purification and terminal treatment, and reduce the risk of secondary pollution. Especially, the present application adopts the combined application of recrystallized silicon carbide honeycomb ceramics and recrystallized silicon carbide honeycomb ceramics loaded with nano zero-valent iron, and the process of oxidative treatment and heavy metal treatment is carried out in turn, compared with the prior art, has outstanding substantial features, the synergistic effect of the two kinds of honeycomb ceramics prolongs the service life of the carrier by 50%, the total removal rate of pickling wastewater COD and heavy metals reaches 98.4% and 96.5% respectively, which is 20%-25% higher than the additive effect of the two carriers used alone, and the effluent stability (continuous 30-day operation fluctuation) is controlled within ±3%. It needs to be emphasized that in the present application, the catalytic oxidation step and the heavy metal treatment step cannot be exchanged in order, the catalytic oxidation step first decomposes organic pollutants, eliminates the interference of the organic pollutants on the nano zero-valent iron, so as to maintain the reduction efficiency of the nano zero-valent iron on heavy metals (such as Cr 6+ , Ni 2+ ); The small molecule organic matter (such as carboxylic acid) produced by oxidation can be used as a chelating agent for heavy metal ions, and forms a stable precipitate with the reduced low-valence heavy metal in the subsequent heavy metal treatment step, which is adsorbed by the honeycomb ceramics, further improving the heavy metal removal effect. The treatment order breaks through the traditional "neutralization first and then treatment" or "oxidation-reduction disordered superposition" process logic, and realizes synergistic effect through targeted step-by-step treatment.

[0009] In the traditional process, the oxidation and reduction steps have no clear sequence, and the treatment efficiency is often low due to the mutual interference of pollutants; according to the properties of pollutants (organic matter needs to be oxidized, heavy metal needs to be reduced), the present application first uses recrystallized silicon carbide honeycomb ceramic to cooperate with the oxidative cracking of organic pollutants, and then uses the same carrier loaded with nano zero-valent iron to specifically treat heavy metals, forming an ordered process chain of "functional complementation and interference avoidance"; the universality of recrystallized silicon carbide honeycomb ceramic (which can adapt to both oxidation and reduction reaction environments) makes the two-step treatment consistent in carrier material, reducing the mass transfer resistance and equipment compatibility problems caused by carrier differences. If the order is changed (first treated by recrystallized silicon carbide honeycomb ceramic loaded with nano zero-valent iron, and then oxidized), the organic pollutants in the pickling wastewater will undergo complexation reaction with nano zero-valent iron to form stable organic iron complexes, covering the surface of nano zero-valent iron and making it lose reduction activity (i.e. "poisoning"), greatly reducing the heavy metal removal efficiency; the ozone and hydrogen peroxide in the subsequent oxidation step will oxidize the nano zero-valent iron (Fe will be oxidized to Fe 2+ / Fe 3+ ), causing the consumption of nano zero-valent iron, and at the same time, a large amount of iron ion precipitation, blocking the pores of the subsequent oxidation reactor.

[0010] At the same time, due to the regular through-hole structure of recrystallized silicon carbide honeycomb ceramic, its porosity can reach 60%-70%, and this structure provides a smooth channel for the flow of wastewater in the first reactor, allowing wastewater to uniformly contact with ozone and hydrogen peroxide. At the same time, the honeycomb structure increases the contact area of gas-liquid-solid three phases, and the residence time of ozone and hydrogen peroxide on the ceramic surface is prolonged, providing sufficient reaction sites for the generation of hydroxyl radicals. Compared with the catalytic oxidation process using ordinary carriers, the oxidation rate of organic pollutants is increased by 40%-50% when recrystallized silicon carbide honeycomb ceramic is used in cooperation with the catalytic oxidation process, and the COD removal rate is increased from 60%-70% to more than 95%. Moreover, the catalytic effect of honeycomb ceramic enhances the utilization rate of ozone and hydrogen peroxide, and under the condition of achieving the same treatment effect, the ozone input amount can be reduced by 20%-25%, and the hydrogen peroxide addition amount can be reduced by 15%-20%, greatly reducing the treatment cost. The Fe 2+ / Fe 3+ ions produced by the reduction of nano zero-valent iron in the second reactor can form precipitates with residual phosphate ions, fluoride ions, etc. after the wastewater enters the adsorption column, and are intercepted by the third-stage recrystallized silicon carbide honeycomb ceramic adsorption column (large-particle-size carriers intercept large-particle-size precipitates, and small-particle-size carriers adsorb fine particles); at the same time, the porous structure of the adsorption column provides a "secondary reaction site" for the nano zero-valent iron that has not completely reacted, continuously removing trace heavy metals.

[0011] Specifically, the pretreatment: removing impurities can prevent the subsequent equipment from being blocked, and ensure the stable operation of the system; in the flocculation process, polyaluminum chloride can make the fine suspended particles and colloids in the wastewater coagulate into larger flocs, which is beneficial to subsequent separation, reduces the turbidity and the content of some pollutants of the wastewater, and reduces the load of the subsequent treatment unit.

[0012] Catalytic oxidation: the pretreated wastewater is reacted with hydrogen peroxide and ozone in a first reaction tower filled with recrystallized silicon carbide honeycomb ceramic carriers. The recrystallized silicon carbide honeycomb ceramic carriers have a large specific surface area, which can provide sufficient space for the reaction. The surface-coated titanium dioxide nanomembrane, under the excitation of ultraviolet light (partly from the ozone decomposition), cooperates with ozone and hydrogen peroxide to generate a large amount of hydroxyl radicals, which efficiently oxidize and decompose the organic matter and reducing substances in the wastewater, greatly reducing the COD and other pollutant indicators.

[0013] Heavy metal treatment: the oxidized wastewater enters a second reaction tower filled with recrystallized silicon carbide honeycomb ceramic carriers loaded with nano zero-valent iron. Nano zero-valent iron has strong reducing properties, which can reduce high-valence heavy metal ions to low-valence or elemental metal, facilitating subsequent separation; the adsorption of the recrystallized silicon carbide honeycomb ceramic carriers further assists in removing heavy metals and some residual pollutants, while the appropriate temperature and treatment time ensure that the reaction proceeds sufficiently, effectively reducing the content of heavy metals in the wastewater.

[0014] Deep purification: the primary qualified wastewater flows through three-stage serial recrystallized silicon carbide honeycomb ceramic adsorption columns, and different particle sizes of silicon carbide honeycomb ceramic particles form a gradient adsorption, further removing residual trace pollutants, pigments, odor substances, etc. in the wastewater, making the water quality more clear and the indicators closer to the discharge standard.

[0015] Terminal treatment: static sedimentation allows the suspended solids in the wastewater to fully settle, and the supernatant is filtered through a ceramic membrane filter, which can effectively intercept bacteria, viruses, and small particles, ensuring that the final effluent water quality meets the strict reuse or discharge requirements.

[0016] Further, in step one, the removal of impurities is by grid filtration to remove large particle impurities from the pickling wastewater; the flocculation is by adding polyaluminum chloride to the pickling wastewater, and the polyaluminum chloride dosage is 50-100 mg / L.

[0017] Compared with the prior art, the specific methods and parameters for removing impurities and flocculation in the pretreatment are defined. Grid filtration can effectively intercept large particle impurities with a diameter greater than the grid spacing, preventing the subsequent equipment from being blocked and ensuring the stable operation of the treatment system. At a dosage of 50-100 mg / L, polyaluminum chloride can fully play a flocculation role, making the colloidal particles and fine suspended substances in the wastewater coagulate into large flocs, which can be removed by subsequent separation, reducing the turbidity of the wastewater.

[0018] Further, in step two, the mass concentration of the hydrogen peroxide solution is 25%-27%; and the dosage of the hydrogen peroxide solution is 1ml-3ml / L of the pretreated wastewater; the ozone input amount is 10L-15L / L of the pretreated wastewater, and the pH value in the first reaction tower is 3-4; and the recrystallized silicon carbide honeycomb ceramic carrier is first soaked in a 0.1mol / L-0.3mol / L tetrabutyl titanate ethanol solution for 2h-3h before being filled into the first reaction tower.

[0019] Compared with the prior art, the above technical solution limits the parameters of the key reagent in the catalytic oxidation step. The hydrogen peroxide solution with a mass concentration of 25%-27% has good stability, and the dosage of 1ml-3ml / L and the ozone input amount of 10L-15L / L are synergistic. In the acidic environment with a pH value of 3-4, a large number of hydroxyl radicals can be generated to strengthen the oxidation and decomposition capacity of organic pollutants, thereby improving the COD removal efficiency. At the same time, the pH value range is suitable for the catalytic activity of the recrystallized silicon carbide honeycomb ceramic carrier, ensuring efficient oxidation reaction.

[0020] Further, in steps two, three and four, the recrystallized silicon carbide honeycomb ceramic carrier is prepared as follows: (1) 70kg of micron-sized silicon carbide, 4kg of hydroxypropyl methyl cellulose, 5kg of plastic, and 13kg of boron carbide, and 8kg of glycerol are weighed; (2) All the materials are mixed to obtain a mixture, and the mixture is divided into two parts, one with a total mass of 80kg and the other with a total mass of 20kg. Then the first part of the mixture is added to a kneading machine for kneading for 4h; (3) The kneaded paste is extruded with a mold to obtain a green body with through holes, which is placed in an oven and raised to 160℃ at a rate of 10℃ / min and kept for 2h; (4) The dried green body is alternately plugged with the second part of the mixture, and then dried again; (5) The green body after alternating plugging is sintered according to the following temperature rising program: uniformly raised to 500℃ within 8h; then uniformly raised to 1100℃ within 8h; then uniformly raised to 1500℃ within 6h; then uniformly raised to 2000℃ within 8h; and finally uniformly raised to 2300℃ within 28h; and the sintered blank is naturally cooled to room temperature for discharge.

[0021] Compared with the prior art, the recrystallized silicon carbide honeycomb ceramic carrier prepared by the above scheme has nanoscale intrawall voids, can withstand a pressure of up to 25kg or more, and can realize the functions of microfiltration, ultrafiltration, nanofiltration and even reverse osmosis membrane in the field of water treatment, thereby successfully applied to the filtration of various water sources at the first and second stages, and realizing the reuse of water resources.

[0022] Further, in step three, the preparation method of the recrystallized silicon carbide honeycomb ceramic carrier loaded with nano zero-valent iron is as follows: Put the recrystallized silicon carbide honeycomb ceramic carrier into a 0.05 mol / L-0.15 mol / L ferrous sulfate solution, add a sodium borohydride solution, and react for 1h-2h under nitrogen protection, then rinse with deionized water and vacuum dry; wherein the molar ratio of sodium borohydride to ferrous sulfate is 2:1.

[0023] Compared with the prior art, the recrystallized silicon carbide honeycomb ceramic carrier loaded with nano zero-valent iron prepared by the method has uniform and firm loading of nano zero-valent iron.

[0024] Further, in step three, the loading amount of nano zero-valent iron is 3%-5% of the mass of the recrystallized silicon carbide honeycomb ceramic carrier.

[0025] Further, in step three, the oxidation wastewater is stirred after being passed into the second reaction tower of the recrystallized silicon carbide honeycomb ceramic carrier loaded with nano zero-valent iron inside, and the stirring speed is 100rpm-150rpm.

[0026] Further, in step four, the particle sizes of the recrystallized silicon carbide honeycomb ceramic carrier adsorption column are 5mm→3mm→2mm in turn, and the adsorption flow rate is 1BV / h-3BV / h; the ratio of the column height to the diameter of the adsorption column is 5:1-8:1, and the operating pressure of each stage of the adsorption column is controlled at 0.1MPa-0.2MPa. Compared with the prior art, the three-stage adsorption column realizes "staged capture" of pollutants through a particle size gradient (5mm→3mm→2mm), the large-particle-size carrier removes suspended and precipitated substances, the small-particle-size carrier adsorbs dissolved organic matter, and the load of terminal static precipitation is reduced; colloidal particles (particle size 0.1-1μm) that do not settle during the static stage can be retained by cross-flow filtration of the ceramic membrane, and the turbulence generated by membrane filtration can also flush the fine particles flowing out of the adsorption column, avoiding the formation of filter cake on the membrane surface.

[0027] Further, in step five, the static time is 30min-40min.

[0028] Further, in step five, the temperature during filtration with the ceramic membrane filter is 25℃-35℃, and a cross-flow filtration method is used during the filtration process, with a cross-flow speed of 1m / s-2m / s.

[0029] Compared with the prior art, the standing time of 30min-40min can make the suspended particles in the advanced treatment wastewater fully settle, reduce the burden of subsequent ceramic membrane filtration; the filtration temperature of 25 DEG C-35 DEG C and the cross-flow speed of 1m / s-2m / s can reduce the deposition of pollutants on the surface of the ceramic membrane, reduce the degree of membrane pollution, keep the filtration flux of the membrane stable, prolong the cleaning cycle of the membrane, and improve the terminal treatment efficiency.

[0030] Further, it also comprises: Step six, regeneration: the used recrystallized silicon carbide honeycomb ceramic carrier in step two and step three is pickled with 0.1mol / L-0.5mol / L sulfuric acid solution for 1h-2h to obtain a pickling solution; then the pickling solution is re-introduced into the first reaction tower for subsequent treatment.

[0031] Compared with the prior art, the regeneration step is pickled with 0.1mol / L-0.5mol / L sulfuric acid solution for 1h-2h, which can effectively remove the pollutants adsorbed on the surface of the recrystallized silicon carbide honeycomb ceramic carrier, restore the adsorption and catalytic performance of the carrier, and the treatment effect of the regenerated carrier is not more than 10% lower than that of the new carrier; the pickling solution is re-introduced into the first reaction tower for treatment, realizing the recycling of resources, reducing the treatment cost, and reducing the discharge of waste.

[0032] The second aspect of the application provides the application of the treatment method in treating pickling wastewater.

[0033] Compared with the prior art, the treatment method is specially designed for the characteristics of pickling wastewater, can effectively deal with the problems of high concentration of acid, heavy metal ions and organic pollutants in pickling wastewater, and has good applicability and stability in treating various pickling wastewater (such as steel pickling wastewater, stainless steel pickling wastewater, etc.), providing a reliable technical scheme for the standard treatment of pickling wastewater. DETAILED DESCRIPTION

[0034] The technical solutions in the embodiments of the application will be described clearly and completely below, obviously, the described embodiments are only part of the embodiments of the application, not all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor belong to the protection scope of the application.

[0035] The silicon carbide in the prior art is mainly used for water quality filtration in the form of a membrane assembly or particles, mainly relying on physical interception to separate suspended particulate matter, but its potential in adsorbing heavy metal ions, catalytic degradation of organic pollutants and synergistic recovery of acid resources has not been fully tapped, and the application of the existing silicon carbide material is mostly limited to a single processing link, and cannot form effective synergy with other processes, resulting in low overall processing efficiency, which cannot meet the dual needs of deep purification and resource recovery of pickling wastewater.

[0036] To overcome the above-mentioned defects, the first aspect of the embodiments of the present application provides a pickling wastewater treatment method, comprising the following steps: Step one, pretreatment: first remove impurities from the pickling wastewater, and then flocculate to obtain pretreated wastewater; Step two, catalytic oxidation: simultaneously inject the pretreated wastewater, hydrogen peroxide solution and ozone into a first reaction tower internally filled with recrystallized silicon carbide honeycomb ceramic carriers, and oxidize for 30-60 min to obtain oxidized wastewater; Step three, heavy metal treatment: pass the oxidized wastewater into a second reaction tower internally loaded with nano zero-valent iron on recrystallized silicon carbide honeycomb ceramic carriers, and treat at 30-40℃ for 35-45 min to obtain primary qualified wastewater; Step four, deep purification: make the primary qualified wastewater flow through three series of recrystallized silicon carbide honeycomb ceramic carrier adsorption columns in sequence to obtain deep treated wastewater; Step five, terminal treatment: let the deep treated wastewater stand and precipitate, and filter the supernatant through a ceramic membrane filter.

[0037] For example, the oxidation treatment time can be specifically selected as 30 min, 45 min, 60 min or a range value composed of any point value, and is preferably 45-60 min.

[0038] For example, the reaction temperature of the second reaction tower can be specifically selected as 30℃, 35℃, 40℃ or a range value composed of any point value, and is preferably 35-40℃.

[0039] For example, the treatment time in the second reaction tower can be specifically selected as 35 min, 40 min, 45 min or a range value composed of any point value, and is preferably 40-45 min.

[0040] When the above technical solution is adopted, the total removal rates of COD and heavy metals reach 98.4% and 96.5% respectively, which achieves an unexpected technical effect compared with the prior art.

[0041] In some embodiments, in step one, removing impurities is to remove large-particle impurities from the pickling wastewater by grid filtering; the flocculation is to add polyaluminum chloride to the pickling wastewater, and the polyaluminum chloride addition amount is 50 mg / L-100 mg / L. It should be understood that the grid spacing of the grid filtering device here is 0.6 mm.

[0042] For example, the polyaluminum chloride addition amount can be specifically selected as 50 mg / L, 65 mg / L, 100 mg / L or a range value composed of any point value, and preferably 60 mg / L-65 mg / L.

[0043] When the above technical solution is adopted, large-particle impurities with a diameter greater than the grid spacing are effectively intercepted. When the polyaluminum chloride addition amount is 50 mg / L-100 mg / L, the colloidal particles and fine suspended substances in the wastewater are coagulated into large flocs, which are removed by subsequent separation, thereby reducing the wastewater turbidity.

[0044] In some embodiments, in step two, the mass concentration of the hydrogen peroxide solution is 25%-27%; the hydrogen peroxide solution addition amount is 1 ml-3 ml / L of pretreated wastewater; the ozone inlet amount is 10 L-15 L / L of pretreated wastewater, and the pH value in the first reaction tower is 3-4; the recrystallized silicon carbide honeycomb ceramic carrier is first soaked in a 0.1 mol / L-0.3 mol / L tetrabutyl titanate ethanol solution for 2 h-3 h before being filled into the first reaction tower.

[0045] For example, the mass concentration of the hydrogen peroxide solution can be specifically selected as 25%, 26%, 27% or a range value composed of any point value, and preferably 2%-26%.

[0046] For example, the hydrogen peroxide solution addition amount in 1 L of pretreated wastewater is 1 ml, 2 ml, 3 ml or a range value composed of any point value, and preferably 1.ml-2 ml.

[0047] For example, the ozone inlet amount in 1 L of pretreated wastewater is 10 L, 12 L, 15 L or a range value composed of any point value, and preferably 12 L-15 L.

[0048] For example, the molar concentration of the tetrabutyl titanate ethanol solution is 0.1 mol / L, 0.2 mol / L, 0.3 mol / L or a range value composed of any point value, and preferably 0.1 mol / L-0.2 mol / L.

[0049] For example, the soaking time in the tetrabutyl titanate ethanol solution can be 2 h, 2.5 h, 3 h or a range value composed of any point value, and preferably 2.5 h-3 h.

[0050] When the technical scheme is adopted, the hydrogen peroxide solution with a mass concentration of 25%-27% has good stability, 1ml-3ml / L of the dosing amount cooperates with 10L-15L / L of the ozone passing amount, a large amount of hydroxyl radicals can be generated in the acidic environment with a pH value of 3-4, the oxidation and decomposition capacity on the organic pollutants is strengthened, and the COD removal efficiency is greatly improved.

[0051] In some embodiments, the preparation method of the recrystallized silicon carbide honeycomb ceramic carrier in steps two, three and four is as follows: (1) 70 kg of micron-sized silicon carbide, 4 kg of hydroxypropyl methyl cellulose, 5 kg of plastic, 13 kg of boron carbide and 8 kg of glycerol are weighed; (2) All the materials are mixed to obtain a mixture, the mixture is divided into two parts, one part with a total mass of 80 kg and the other part with a total mass of 20 kg, and then the first part of the mixture is added to a kneading machine for kneading for 4 hours; (3) The kneaded paste is extruded with a mold to obtain a green body with through holes, and is placed in an oven and raised to 160℃ at a rate of 10℃ / min and kept for 2 hours; (4) The dried green body is alternately plugged with the second part of the mixture, and then dried again; (5) The green body after alternating plugging is sintered according to the following temperature rising program: uniformly raised to 500℃ within 8 hours, then uniformly raised to 1100℃ within 8 hours, then uniformly raised to 1500℃ within 6 hours, then uniformly raised to 2000℃ within 8 hours, and finally uniformly raised to 2300℃ within 28 hours; the sintered blank is naturally cooled to room temperature and discharged.

[0052] The recrystallized silicon carbide honeycomb ceramic carrier prepared by the above scheme has nanoscale intrawall voids, can withstand a pressure of up to 25kg or more, and can realize microfiltration, ultrafiltration, nanofiltration or even reverse osmosis membrane function in the field of water treatment, thereby successfully applied to primary and secondary filtration of various water sources to realize the reuse of water resources.

[0053] In some embodiments, in step three, the preparation method of the recrystallized silicon carbide honeycomb ceramic carrier loaded with nano zero-valent iron is as follows: The recrystallized silicon carbide honeycomb ceramic carrier is placed in a 0.05mol / L-0.15mol / L ferrous sulfate solution, a sodium borohydride solution is added, and the reaction is carried out under nitrogen protection for 1h-2h, then washed with deionized water and vacuum dried; wherein the molar ratio of sodium borohydride to ferrous sulfate is 2:1.

[0054] For example, the molar concentration of the ferrous sulfate solution is 0.05 mol / L, 0.10 mol / L, 0.15 mol / L or any point value consisting of a range value, preferably 0.05 mol / L-0.10 mol / L.

[0055] For example, the reaction time is 1h, 1.5h, 2h or any point value consisting of a range value, preferably 1h-1.5h.

[0056] The above technical solution prepares a nanometer zero-valent iron loaded recrystallized silicon carbide honeycomb ceramic carrier, and the nanometer zero-valent iron is uniformly dispersed and firmly loaded.

[0057] In some embodiments, in step three, the loading amount of nanometer zero-valent iron is 3%-5% of the mass of the recrystallized silicon carbide honeycomb ceramic carrier.

[0058] For example, the loading amount of nanometer zero-valent iron is 3%, 4%, 5% or any point value consisting of a range value, preferably 4%-5% of the mass of the recrystallized silicon carbide honeycomb ceramic carrier.

[0059] In some embodiments, in step three, after the oxidized wastewater is introduced into the second reaction tower of the recrystallized silicon carbide honeycomb ceramic carrier loaded with nanometer zero-valent iron inside, stirring is performed, and the stirring speed is 100 rpm-150 rpm.

[0060] For example, the stirring speed can be selected as 100 rpm, 120 rpm, 150 rpm or any point value consisting of a range value, preferably 120 rpm-150 rpm.

[0061] In some embodiments, in step four, the particle sizes of the recrystallized silicon carbide honeycomb ceramic carrier adsorption column are 5 mm→3 mm→2 mm in turn, the adsorption flow rate is 1 BV / h-3 BV / h, the ratio of the column height to the diameter of the adsorption column is 5:1-8:1, and the operating pressure of each stage of the adsorption column is controlled at 0.1 MPa-0.2 MPa.

[0062] For example, the ratio of the column height to the diameter of the adsorption column is 5:1, 6:1, 8:1 or any point value consisting of a range value, preferably (6-8):1.

[0063] The three-stage adsorption column realizes "graded capture" of pollutants through the particle size gradient (5 mm→3 mm→2 mm), the large-particle-size carrier removes suspended and precipitated matters, the small-particle-size carrier adsorbs dissolved organic matters, and the load of the terminal static precipitation is reduced; the colloidal particles (particle size 0.1-1 μm) that are not precipitated in the static stage can be retained by the cross-flow filtration of the ceramic membrane, and the turbulence generated by the membrane filtration can flush the small particles out of the adsorption column, thereby avoiding the formation of filter cake on the membrane surface.

[0064] In some embodiments, the standing time in step five is 30-40 minutes; the temperature during the filtration with the ceramic membrane filter is 25-35℃, and the cross-flow filtration is adopted during the filtration, and the cross-flow speed is 1-2 m / s.

[0065] For example, the standing time is 30 minutes, 35 minutes, 40 minutes or any point value range, preferably 3-40 minutes.

[0066] For example, the temperature is 25℃, 30℃, 35℃ or any point value range, preferably 30-35℃.

[0067] For example, the cross-flow speed is 1 m / s, 1.5 m / s, 2 m / s or any point value range, preferably 1.5-2 m / s.

[0068] When the above technical solution is adopted, the standing time of 30-40 minutes can make the suspended particles in the deep treatment wastewater fully settle, reducing the burden of the subsequent ceramic membrane filtration; the filtration temperature of 25-35℃ and the cross-flow speed of 1-2 m / s can reduce the deposition of pollutants on the surface of the ceramic membrane, reduce the degree of membrane pollution, keep the filtration flux of the membrane stable, prolong the cleaning cycle of the membrane and improve the terminal treatment efficiency.

[0069] In some embodiments, the method further comprises: Step six, regeneration: the used recrystallized silicon carbide honeycomb ceramic carrier in step two and step three is pickled with 0.1-0.5 mol / L sulfuric acid solution for 1-2 hours to obtain a pickling solution; then the pickling solution is re-introduced into the first reaction tower for subsequent treatment.

[0070] The regeneration step can effectively remove the pollutants adsorbed on the surface of the recrystallized silicon carbide honeycomb ceramic carrier by pickling with 0.1-0.5 mol / L sulfuric acid solution for 1-2 hours, so that the carrier restores the adsorption and catalytic performance, and the treatment effect of the regenerated carrier decreases by no more than 10% compared with the new carrier; the pickling solution is re-introduced into the first reaction tower for treatment, realizing the recycling of resources, reducing the treatment cost and reducing the discharge of waste.

[0071] The second aspect of the embodiment of the application provides the application of the treatment method in treating pickling wastewater. The treatment method is specially designed for the characteristics of pickling wastewater, can effectively deal with the problems of high concentration of acid, heavy metal ions and organic pollutants in pickling wastewater, and has good applicability and stability in treating various pickling wastewaters (such as steel pickling wastewater, stainless steel pickling wastewater, etc.), providing a reliable technical solution for the standard treatment of pickling wastewater.

[0072] In order to better illustrate the technical solutions of the present application, the following examples are provided, which are only for illustrating the technical solutions of the present application, and it should be understood that, unless specifically stated, the materials involved in the examples are all commercially available. Examples

[0073] A treatment method of pickling wastewater, comprising the following steps: Step one, pretreatment: first, the pickling wastewater is passed into a grid filter device to remove impurities, then 50mg / L polyaluminum chloride flocculation is added to obtain pretreated wastewater; the grid spacing of the grid filter device is 0.6mm; Step two, catalytic oxidation: the pretreated wastewater, hydrogen peroxide solution and ozone are simultaneously injected into a first reaction tower internally filled with recrystallized silicon carbide honeycomb ceramic carrier, and oxidized for 30min to obtain oxidized wastewater; the mass concentration of the hydrogen peroxide solution is 25%; the dosage of the hydrogen peroxide solution is 1ml of pretreated wastewater; the ozone input amount is 10L / L of pretreated wastewater, and the pH value in the first reaction tower is 3; before being filled into the first reaction tower, the recrystallized silicon carbide honeycomb ceramic carrier is first soaked in a 0.1mol / L tetrabutyl titanate ethanol solution for 2h; Step three, heavy metal treatment: the oxidized wastewater is passed into a second reaction tower internally loaded with nanometer zero-valent iron recrystallized silicon carbide honeycomb ceramic carrier, and treated at 100rpm and 30℃ for 35min to obtain primary qualified wastewater; Step four, deep purification: the primary qualified wastewater is sequentially flowed through three levels of recrystallized silicon carbide honeycomb ceramic carrier adsorption columns in series to obtain deep treated wastewater; the particle sizes of the recrystallized silicon carbide honeycomb ceramic carrier adsorption columns are 5mm→3mm→2mm in turn, and the adsorption flow rate is 1BV / h; the column height to diameter ratio of the adsorption column is 5:1, and the operating pressure of each level of adsorption column is controlled at 0.1MPa-0.2MPa; Step five, terminal treatment: the deep treated wastewater is allowed to stand and precipitate for 30min, and the supernatant is filtered through a ceramic membrane filter at 25℃; a cross-flow filtration method is adopted during the filtering process, and the cross-flow speed is 1m / s.

[0074] The preparation process of the recrystallized silicon carbide honeycomb ceramic carrier is as follows: (1) 70kg of micron-sized silicon carbide, 4kg of hydroxypropyl methylcellulose, 5kg of plastic, 13kg of boron carbide and 8kg of glycerol are weighed; (2) all the materials are mixed to obtain a mixed material, the mixed material is divided into two parts, one part with a total mass of 80kg and the other part with a total mass of 20kg, then the first part of the mixed material is added to a kneading machine for kneading for 4h; (3) extruding the kneaded paste with a die to obtain a green body with through holes, and placing the green body in an oven, and increasing the temperature to 160°C at a rate of 10°C / min, and keeping for 2h; (4) plugging the through holes of the dried green body alternately with the second mixture, and drying again; (5) sintering the green body with the plugged through holes according to the following temperature increasing procedure: uniformly increasing the temperature to 500°C in 8h, then uniformly increasing the temperature to 1100°C in 8h, then uniformly increasing the temperature to 1500°C in 6h, then uniformly increasing the temperature to 2000°C in 8h, and finally uniformly increasing the temperature to 2300°C in 28h, and naturally cooling the sintered body to room temperature for discharging.

[0075] The preparation method of the recrystallized silicon carbide honeycomb ceramic carrier loaded with nano zero-valent iron is as follows: The recrystallized silicon carbide honeycomb ceramic carrier is placed in a 0.05 mol / L ferrous sulfate solution, a sodium borohydride solution is added, and the reaction is carried out under nitrogen protection for 1h, then the carrier is washed with deionized water and vacuum dried; the molar ratio of sodium borohydride to ferrous sulfate is 2:1; the loading amount of nano zero-valent iron is 3% of the mass of the recrystallized silicon carbide honeycomb ceramic carrier. Embodiment

[0076] A method for treating pickling wastewater, comprising the following steps: Step one, pretreatment: first, the pickling wastewater is passed through a grid filter device to remove impurities, then 100mg / L of polyaluminum chloride flocculation is added to obtain pretreated wastewater; the grid spacing of the grid filter device is 0.6mm; Step two, catalytic oxidation: the pretreated wastewater, hydrogen peroxide solution and ozone are simultaneously injected into a first reaction tower internally filled with recrystallized silicon carbide honeycomb ceramic carriers, and oxidized for 60min to obtain oxidized wastewater; the mass concentration of the hydrogen peroxide solution is 27%; the dosage of the hydrogen peroxide solution is 3ml of pretreated wastewater; the ozone input amount is 15L / L of pretreated wastewater, and the pH value in the first reaction tower is 4; before being filled into the first reaction tower, the recrystallized silicon carbide honeycomb ceramic carriers are first soaked in a 0.3mol / L tetrabutyl titanate ethanol solution for 3h; Step three, heavy metal treatment: the oxidized wastewater is passed through a second reaction tower internally loaded with nano zero-valent iron recrystallized silicon carbide honeycomb ceramic carriers, and treated at 150rpm and 40°C for 45min to obtain primary qualified wastewater; Step four, deep purification: the primary qualified wastewater flows through three levels of recrystallized silicon carbide honeycomb ceramic carrier adsorption column in series, to obtain deep treated wastewater; the particle size of each level of recrystallized silicon carbide honeycomb ceramic carrier adsorption column is 5mm→3mm→2mm in turn, and the adsorption flow rate is 3BV / h; the ratio of column height to diameter of the adsorption column is 8:1, and the operating pressure of each level of adsorption column is controlled at 0.1MPa-0.2MPa; Step five, terminal treatment: the deep treated wastewater is allowed to stand and settle for 40min, and the supernatant at 35℃ is filtered through a ceramic membrane filter, and a cross-flow filtration method is adopted during the filtration process, with a cross-flow speed of 2m / s.

[0077] The preparation process of the recrystallized silicon carbide honeycomb ceramic carrier is as follows: (1) 70kg of micron-sized silicon carbide, 4kg of hydroxypropyl methyl cellulose, 5kg of plastic, 13kg of boron carbide, and 8kg of glycerol are weighed; (2) All the materials are mixed to obtain a mixture, which is divided into two parts, one with a total mass of 80kg and the other with a total mass of 20kg. Then the first part of the mixture is added to a kneading machine for kneading for 4h; (3) The kneaded paste is extruded with a mold to obtain a green body with through holes, which is placed in an oven and raised to 160℃ at a rate of 10℃ / min and kept for 2h; (4) The dried green body is alternately plugged with the second part of the mixture, and then dried again; (5) The green body after alternating plugging is sintered according to the following temperature rising program: uniformly raised to 500℃ within 8h, then uniformly raised to 1100℃ within 8h, then uniformly raised to 1500℃ within 6h, then uniformly raised to 2000℃ within 8h, and finally uniformly raised to 2300℃ within 28h. The sintered blank is naturally cooled to room temperature and discharged.

[0078] The preparation method of the recrystallized silicon carbide honeycomb ceramic carrier loaded with nano zero-valent iron is as follows: The recrystallized silicon carbide honeycomb ceramic carrier is placed in a 0.15mol / L ferrous sulfate solution, and a sodium borohydride solution is added, and the reaction is carried out under nitrogen protection for 2h, then washed with deionized water and vacuum dried; the molar ratio of sodium borohydride to ferrous sulfate is 2:1; the loading amount of nano zero-valent iron is 5% of the mass of the recrystallized silicon carbide honeycomb ceramic carrier. Example

[0079] A method for treating pickling wastewater, comprising the following steps: Step one, pretreatment: first, the pickling wastewater is passed through a screen filter device to remove impurities, then 65mg / L of polyaluminum chloride flocculation is added to obtain pretreated wastewater; the grid spacing of the screen filter device is 0.6mm; Step two, catalytic oxidation: the pretreated wastewater, hydrogen peroxide solution and ozone are injected into the first reaction tower internally filled with recrystallized silicon carbide honeycomb ceramic carrier at the same time, and oxidized for 45 min to obtain oxidized wastewater; wherein the mass concentration of the hydrogen peroxide solution is 26%; and the dosage of the hydrogen peroxide solution is 2 ml of the pretreated wastewater; the ozone input amount is 12 L / L of the pretreated wastewater, and the pH value in the first reaction tower is 4; before being filled into the first reaction tower, the recrystallized silicon carbide honeycomb ceramic carrier is first soaked in a 0.2 mol / L tetrabutyl titanate ethanol solution for 2.5 h; Step three, heavy metal treatment: the oxidized wastewater is introduced into the second reaction tower internally loaded with nano zero-valent iron recrystallized silicon carbide honeycomb ceramic carrier, and treated at 120 rpm and 35℃ for 40 min to obtain primary qualified wastewater; Step four, deep purification: the primary qualified wastewater is sequentially flowed through three levels of recrystallized silicon carbide honeycomb ceramic carrier adsorption columns in series to obtain deep treated wastewater; the particle sizes of the recrystallized silicon carbide honeycomb ceramic carrier adsorption columns are 5 mm→3 mm→2 mm in turn, and the adsorption flow rate is 2 BV / h; the column height to diameter ratio of the adsorption column is 6:1, and the operating pressure of each level of adsorption column is controlled at 0.1-0.2 MPa; Step five, terminal treatment: the deep treated wastewater is allowed to stand and precipitate for 35 min, and the supernatant is filtered through a ceramic membrane filter at 30℃; and a cross-flow filtration method is adopted during the filtration process, and the cross-flow speed is 1.5 m / s.

[0080] Step six, regeneration: the used recrystallized silicon carbide honeycomb ceramic carrier in step two and step three is pickled with a 0.2 mol / L sulfuric acid solution for 1.5 h to obtain a pickling solution; and then the pickling solution is introduced into the first reaction tower for subsequent treatment.

[0081] The preparation process of the recrystallized silicon carbide honeycomb ceramic carrier is as follows: (1) 70 kg of micron-sized silicon carbide, 4 kg of hydroxypropyl methylcellulose, 5 kg of plastic, and 13 kg of boron carbide, and 8 kg of glycerol are weighed; (2) all the materials are mixed to obtain a mixture, and the mixture is divided into two parts, one part with a total mass of 80 kg and the other part with a total mass of 20 kg, and then the first part of the mixture is added to a kneading machine for kneading for 4 h; (3) the kneaded paste is extruded with a mold to obtain a green body with through holes, which is placed in an oven and raised to 160℃ at a rate of 10℃ / min and kept for 2 h; (4) the dried green body is alternately plugged with the second part of the mixture, and then dried again; (5) The green body with the alternating hole blocking is sintered according to the following temperature rising procedure: uniformly rising to 500 DEG C within 8h; then uniformly rising to 1100 DEG C within 8h; then uniformly rising to 1500 DEG C within 6h; then uniformly rising to 2000 DEG C within 8h; finally uniformly rising to 2300 DEG C within 28h; and the sintered blank is naturally cooled to room temperature and discharged.

[0082] The preparation method of the recrystallized silicon carbide honeycomb ceramic carrier loaded with nano zero-valent iron is as follows: The recrystallized silicon carbide honeycomb ceramic carrier is put into a 0.10 mol / L ferrous sulfate solution, a sodium borohydride solution is added, and the reaction is carried out for 1.5h under nitrogen protection, then the recrystallized silicon carbide honeycomb ceramic carrier is washed with deionized water and vacuum dried; wherein the molar ratio of sodium borohydride to ferrous sulfate is 2:1; the loading amount of nano zero-valent iron is 4% of the mass of the recrystallized silicon carbide honeycomb ceramic carrier.

[0083] Comparative Example 1 Taking Example 3 as an example, compared with Example 3, the difference lies in that the heavy metal treatment is performed first, and then the catalytic oxidation step is performed, and the rest of the process remains unchanged.

[0084] Comparative Example 2 Taking Example 3 as an example, compared with Example 3, the difference lies in that the recrystallized silicon carbide honeycomb ceramic carrier in step two is replaced by a recrystallized silicon carbide honeycomb ceramic carrier loaded with nano zero-valent iron, and the rest of the process remains unchanged.

[0085] Comparative Example 3 Taking Example 3 as an example, compared with Example 3, the difference lies in that the recrystallized silicon carbide honeycomb ceramic carrier loaded with nano zero-valent iron in step three is replaced by a recrystallized silicon carbide honeycomb ceramic carrier, and the rest of the process remains unchanged.

[0086] Comparative Example 4 Taking Example 3 as an example, compared with Example 3, the difference lies in that the recrystallized silicon carbide honeycomb ceramic carrier in steps two and three is replaced by a commercially available silicon carbide ceramic membrane.

[0087] Comparative Example 5 Taking Example 3 as an example, compared with Example 3, in step two, the sodium hypochlorite solution and oxygen are used to replace the hydrogen peroxide solution and ozone respectively.

[0088] Comparative Example 6 Taking Example 3 as an example, compared with Example 3, the difference lies in that the process of catalytic oxidation in step two is removed.

[0089] Comparative Example 7 Taking Example 3 as an example, compared with Example 3, the difference lies in that the process of heavy metal treatment in step three is removed.

[0090] Comparative Example 8 is the same as Example 3 except that step four is eliminated.

[0091] The COD removal rate and heavy metal ion removal rate of the pickling wastewater obtained by the above treatment method were determined, and the test process was as follows: Water samples were collected from the original pickling wastewater before treatment and the final treated effluent of each example and comparative example, and each group of samples was collected in triplicate, numbered and stored in a refrigerator (4°C). The determination was completed within 24 h.

[0092] COD removal rate determination (potassium dichromate method, according to GB 11914-89): 20.0 mL of water sample was placed in a refluxing conical flask, 10.0 mL of 0.25 mol / L potassium dichromate standard solution, 30 mL of silver sulfate-sulfuric acid solution (catalyst) was added, shaken well, and connected with reflux condenser, heated and refluxed for 2 h. After cooling to room temperature, 90 mL of water was added to the mouth of the condenser to wash the wall, the conical flask was removed, 3 drops of phenanthroline indicator were added, and 0.1 mol / L ferrous ammonium sulfate standard solution was titrated to the end point when the solution changed from yellow to blue green to red brown. The consumption volume was recorded. At the same time, a blank test was carried out (20 mL of distilled water was used instead of water sample, and the rest of the steps were the same).

[0093] Calculation of COD value: (wherein: V0 is the blank consumption of ferrous ammonium sulfate volume, V1 is the water sample consumption volume, c is the ferrous ammonium sulfate concentration, V is the water sample volume, and 8 is the molar mass of oxygen).

[0094] COD removal rate: Metal ion removal rate determination (atomic absorption spectrophotometry, according to GB 11912-89): The raw water and effluent were pretreated: 50 mL of water sample was taken, 10 mL of nitric acid was added, and the solution was heated and digested until it was clear. After cooling to room temperature, it was diluted to 100 mL with deionized water. The ion concentration of Fe² + , Cr³ + , Ni² + , Cu² + in the digested solution was determined by atomic absorption spectrophotometer (model: AA-6300) (according to the characteristics of pickling wastewater, typical heavy metal ions were selected), and the total metal ion concentration (sum of ion concentrations) was calculated.

[0095] Metal ion removal rate: The determination results (the raw water COD was 500 mg / L, and the total metal ion concentration of the raw water was 100 mg / L) are shown in Table 1.

[0096] Table 1 COD removal rate Metal ion removal rate Example 1 96.7 95.3 Example 2 95.8 92.4 Example 3 98.4 96.5 Comparative Example 1 56.4 90.1 Comparative Example 2 71.5 74.6 Comparative Example 3 78.3 75.8 Comparative Example 4 82.6 83.5 Comparative Example 5 72.8 90.7 Comparative Example 6 63.7 90.4 Comparative Example 7 70.3 42.3 Comparative Example 8 75.6 92.1 The analysis of the results in Table 1 shows that the removal rates of Comparative Example 1 decrease due to the reversal of the "catalytic oxidation" and "heavy metal treatment" steps, which causes mutual interference between organic matter and heavy metals. In Comparative Example 2, the recrystallized silicon carbide honeycomb ceramic carrier in Step 2 is replaced by a recrystallized silicon carbide honeycomb ceramic carrier loaded with nano zero-valent iron, and in Comparative Example 3, the recrystallized silicon carbide honeycomb ceramic carrier loaded with nano zero-valent iron in Step 3 is replaced by a recrystallized silicon carbide honeycomb ceramic carrier, at this time, the COD removal rate and the metal ion removal rate are both significantly reduced, which shows that the recrystallized silicon carbide honeycomb ceramic carrier loaded with nano zero-valent iron must be used in conjunction with the recrystallized silicon carbide honeycomb ceramic carrier to play a role in simultaneously removing COD and metal ions; in Comparative Example 4, a commercially available silicon carbide ceramic membrane is used, and due to insufficient pore structure and active sites, the removal effect is poorer than that of the self-made recrystallized silicon carbide ceramic carrier. In Comparative Example 5, sodium hypochlorite and oxygen, which also have oxidation properties, are used to replace hydrogen peroxide solution and ozone, and the final results are very different from those of Example 3, which shows that the self-made recrystallized silicon carbide ceramic carrier in the present application can only be used in conjunction with hydrogen peroxide and ozone to significantly remove COD in pickling wastewater; in Comparative Examples 6-8, after removing a certain process, the COD removal rate or the metal ion removal rate is reduced, which shows that the process steps in the present application have a synergistic effect, and only when they are combined together can the pickling wastewater be effectively treated.

[0097] The above description of disclosed embodiments enables one of ordinary skill in the art to make or use the application. Various modifications to these embodiments will be readily apparent to those of ordinary skill in the art, and the generic principles defined herein can be applied to other embodiments without departing from the spirit or scope of the application. Accordingly, the application is not to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for treating pickling wastewater, characterized in that, Includes the following steps: Step 1, Pretreatment: First, remove impurities from the pickling wastewater and then flocculate it to obtain pretreated wastewater; Step 2, Catalytic oxidation: The pretreated wastewater, hydrogen peroxide solution and ozone are simultaneously injected into the first reaction tower filled with recrystallized silicon carbide honeycomb ceramic carrier, and the oxidation treatment is carried out for 30 min-60 min to obtain oxidized wastewater; Step 3, Heavy metal treatment: The oxidized wastewater is passed into the second reaction tower with a recrystallized silicon carbide honeycomb ceramic carrier internally loaded with nano-zero valent iron, and treated at 30℃-40℃ for 35min-45min to obtain primary qualified wastewater; Step 4, Deep Purification: The primary qualified wastewater is sequentially passed through a three-stage series recrystallized silicon carbide honeycomb ceramic carrier adsorption column to obtain deeply treated wastewater; Step 5, Terminal Treatment: The deep-treated wastewater is allowed to settle and the supernatant is filtered through a ceramic membrane filter.

2. The method for treating pickling wastewater according to claim 1, characterized in that, In step one, the removal of impurities involves filtering the pickling wastewater through a screen to remove large particulate impurities. And / or, The flocculation is achieved by adding polyaluminum chloride to the pickling wastewater, and the dosage of polyaluminum chloride is 50 mg / L-100 mg / L.

3. The method for treating pickling wastewater according to claim 1, characterized in that, In step two, the mass concentration of the hydrogen peroxide solution is 25%-27%; and the dosage of the hydrogen peroxide solution is 1 ml-3 ml / L of pretreated wastewater; and / or, The ozone injection rate is 10L-15L / L of pretreated wastewater, and the pH value in the first reaction tower is 3-4; and / or.

4. The method for treating pickling wastewater according to claim 1, characterized in that, In step two, the recrystallized silicon carbide honeycomb ceramic carrier is first soaked in a 0.1 mol / L - 0.3 mol / L tetrabutyl titanate ethanol solution for 2 h - 3 h before being filled into the first reaction tower.

5. A method for treating pickling wastewater according to any one of claims 1-4, characterized in that, In steps two, three, and four, the preparation method of the recrystallized silicon carbide honeycomb ceramic carrier is as follows: (1) Weigh out 70 kg of micron-sized silicon carbide, 4 kg of hydroxypropyl methylcellulose, 5 kg of plastic, 13 kg of boron carbide, and 8 kg of glycerin; (2) Mix all the materials to obtain a mixture. Divide the mixture into two parts, one with a total mass of 80 kg and the other with a total mass of 20 kg. Then add the first part of the mixture to the kneader and knead for 4 hours. (3) The kneaded paste is extruded with a mold to obtain a green body with through holes. It is placed in an oven and heated to 160°C at a rate of 10°C / min and kept for 2 hours. (4) Use the second mixture to alternately plug the holes in the dried green body, and then dry it again; (5) The green billet with alternating plugs is sintered according to the following heating procedure: the temperature is raised to 500℃ at a constant rate within 8 hours; then the temperature is raised to 1100℃ at a constant rate within 8 hours; then the temperature is raised to 1500℃ at a constant rate within 6 hours; then the temperature is raised to 2000℃ at a constant rate within 8 hours; and finally the temperature is raised to 2300℃ at a constant rate within 28 hours. The sintered billet is then cooled to room temperature and discharged.

6. The method for treating pickling wastewater according to claim 5, characterized in that, In step three, the preparation method of recrystallized silicon carbide honeycomb ceramic carrier loaded with nano-zero valent iron is as follows: The recrystallized silicon carbide honeycomb ceramic carrier was placed in a 0.05 mol / L-0.15 mol / L ferrous sulfate solution, and sodium borohydride solution was added. The reaction was carried out under nitrogen protection for 1-2 hours, followed by rinsing with deionized water and vacuum drying. The molar ratio of sodium borohydride to ferrous sulfate was 2:

1. And / or, The loading of nano-zero-valent iron is 3%-5% of the mass of the recrystallized silicon carbide honeycomb ceramic carrier; and / or, The oxidized wastewater is fed into the second reaction tower, which is internally supported by a recrystallized silicon carbide honeycomb ceramic carrier loaded with nano-zero valent iron, and then stirred at a speed of 100-150 rpm.

7. The method for treating pickling wastewater according to claim 5, characterized in that, In step four, the particle sizes of the recrystallized silicon carbide honeycomb ceramic carrier adsorption columns are 5mm→3mm→2mm respectively, and the adsorption flow rate is 1BV / h-3BV / h; the column height to diameter ratio of the adsorption column is 5:1-8:1, and the operating pressure of each adsorption column is controlled at 0.1MPa-0.2MPa.

8. The method for treating pickling wastewater according to claim 5, characterized in that, In step five, the settling time is 30-40 minutes; and / or, The temperature during filtration using the ceramic membrane filter is 25℃-35℃, and a cross-flow filtration method is adopted during the filtration process, with a cross-flow velocity of 1m / s-2m / s.

9. The method for treating pickling wastewater according to claim 1, characterized in that, Also includes: Step 6, Regeneration: The recrystallized silicon carbide honeycomb ceramic carrier used in Steps 2 and 3 is acid-washed with 0.1mol / L-0.5mol / L sulfuric acid solution for 1-2 hours to obtain an acid washing solution; then the acid washing solution is reintroduced into the first reaction tower for subsequent processing.

10. The application of the treatment method according to any one of claims 1-9 in the treatment of pickling wastewater.