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CN-122010362-A - Treatment method of hot galvanizing wastewater

CN122010362ACN 122010362 ACN122010362 ACN 122010362ACN-122010362-A

Abstract

The invention discloses a treatment method of hot galvanizing wastewater, which comprises the following steps of S1, mixing hot galvanizing acid washing wastewater with alkaline washing wastewater, regulating pH, then introducing air to obtain mixed wastewater liquid, S2, adding a composite additive A into the mixed wastewater liquid in the step S1, stirring for reaction, introducing CO 2 gas after the reaction is finished, controlling the pH of the wastewater to be 6-7, then carrying out standing sedimentation and filtering to obtain supernatant, S3, adding a composite additive B into the supernatant in the step S2, carrying out constant-temperature reaction, controlling the pH to be 8-9, and carrying out microfiltration membrane treatment after the reaction is finished. The steps of the treatment method are mutually linked in function positioning, so that the multistage cooperative removal of heavy metals and ammonia nitrogen in the hot galvanizing wastewater is realized, and the quality of the yielding water meets the corresponding emission standard requirements.

Inventors

  • NI HUAGANG
  • CHEN YULI
  • DING WENJIAN
  • PENG JINGPING

Assignees

  • 杭州汇能实业有限公司

Dates

Publication Date
20260512
Application Date
20260410

Claims (10)

  1. 1. The method for treating the hot galvanizing wastewater is characterized by comprising the following steps of: S1, mixing hot galvanizing pickling wastewater and alkaline washing wastewater, regulating pH, and then introducing air to obtain mixed wastewater liquid; S2, adding a composite additive A into the mixed wastewater in the step S1, stirring for reaction, introducing CO 2 gas after the reaction is finished, controlling the pH of the wastewater to be 6-7, then carrying out standing sedimentation, and filtering to obtain supernatant; And S3, adding a composite additive B into the supernatant in the step S2, performing constant-temperature reaction, controlling the pH to 8-9, and performing microfiltration membrane treatment after the reaction is completed.
  2. 2. The method for treating hot dip galvanizing wastewater according to claim 1, wherein in step S1, the pH is 4-6, the aeration amount of the air is 1-1.5L/(l·min), and the aeration time is 20-40min.
  3. 3. The method for treating hot dip galvanizing wastewater according to claim 1, wherein in step S2, the preparation method of the composite additive a is as follows: (1) Adding mesoporous silica into an ethanol water solution, then adding gamma-glycidol ether oxygen propyl trimethoxy silane, carrying out constant temperature reaction, and filtering, washing and drying after the reaction is finished to obtain pretreated mesoporous silica; adding pretreated mesoporous silica into DMF, then adding tri (2-aminoethyl) amine, heating for reaction, and filtering, washing and drying after the reaction is finished to obtain organized silica; (2) Adding 4-carboxyphenylboronic acid into MES buffer solution, then adding EDC and NHS, stirring for activation, then adding organic silicon dioxide, stirring for reaction, filtering, washing and drying after the reaction is finished to obtain a solid product, adding deionized water into the solid product, adjusting the pH to 11-12, then adding sodium chloroacetate for heating reaction, adjusting the pH to 7 after the reaction is finished, and filtering, washing and drying to obtain modified silicon dioxide; (3) Mixing the modified silicon dioxide, polyaluminium chloride and polyethylene glycol uniformly to obtain the composite material.
  4. 4. The method for treating hot galvanizing wastewater according to claim 3, wherein in the step (1), the mass ratio of mesoporous silica to gamma-glycidoxypropyl trimethoxysilane is 100:8-12, the temperature of the constant temperature reaction is 60-70 ℃ for 3-4 hours, the mass ratio of the pretreated mesoporous silica to tri (2-aminoethyl) amine is 100:15-25, and the temperature of the heating reaction is 75-85 ℃ for 4-5 hours.
  5. 5. The method for treating hot-dip galvanizing wastewater according to claim 3, wherein the mass ratio of the 4-carboxyphenylboronic acid, EDC, NHS and the organized silicon dioxide in the step (2) is 8-12:20-30:15-20:100, the temperature of the stirring reaction is 20-25 ℃ for 2-4 hours, the mass ratio of the solid product and sodium chloroacetate is 100:20-30, the temperature of the heating reaction is 60-70 ℃ for 8-10 hours.
  6. 6. The method for treating hot dip galvanizing wastewater according to claim 3, wherein the mass ratio of the modified silicon dioxide, the polyaluminum chloride and the polyethylene glycol in the step (3) is 15-25:30-50:5-10.
  7. 7. The method for treating hot dip galvanizing wastewater according to claim 1, wherein in the step S2, the addition amount of the composite additive A is 0.1-0.3% of the mass of the mixed wastewater liquid, the temperature of the stirring reaction is 40-50 ℃ and the time is 30-60min, the ventilation amount of the CO 2 is 0.3-0.5L/(L.min), and the time of standing sedimentation is 1-2h.
  8. 8. The method for treating hot dip galvanizing wastewater according to claim 1, wherein the preparation method of the composite additive B in step S3 is as follows: according to the weight portions, 35 to 50 portions of sodium bicarbonate, 15 to 25 portions of modified molecular sieve, 3 to 8 portions of cationic polyacrylamide, 8 to 15 portions of sodium carbonate and 20 to 30 portions of diatomite are evenly mixed, thus obtaining the catalyst.
  9. 9. The method for treating hot dip galvanizing wastewater according to claim 8, wherein the preparation method of the modified molecular sieve is characterized in that the 4A type molecular sieve is added into NH 4 Cl solution with the concentration of 1-2 mol/L, stirred for 4-5h at 80-90 ℃, and then calcined for 2-3h at 350-450 ℃ to obtain the modified molecular sieve.
  10. 10. The method for treating hot dip galvanizing wastewater according to claim 1, wherein in step S3, the addition amount of the composite additive B is 0.4-0.6% of the supernatant mass, the temperature of the constant temperature reaction is 55-65 ℃ for 1.5-2.5 hours, the pore diameter of the microfiltration membrane is 0.1-0.45 μm, the operating pressure is 0.05-0.15MPa, and the operating temperature is 50-60 ℃.

Description

Treatment method of hot galvanizing wastewater Technical Field The invention belongs to the technical field of wastewater treatment, and particularly relates to a treatment method of hot galvanizing wastewater. Background The hot galvanizing process is one of the most widely used steel corrosion prevention treatment methods in industrial production, and the production process involves a plurality of procedures of pickling rust removal, plating assistant treatment, hot dip galvanizing and the like, and each procedure can generate a certain amount of wastewater. The quality of hot galvanizing wastewater has remarkable complexity that the pH of the wastewater generated in the pickling process is as low as 1-3, a large amount of Fe 2+、Fe3+ and Cl - are contained, the plating assisting agent used in the plating assisting process generally takes zinc chloride and ammonium chloride as main components, the residual liquid and flushing water of the plating assisting agent contain high-concentration Zn 2+ and NH 4+, and the alkaline washing wastewater has higher pH and contains suspended solids and a certain amount of organic matters. The wastewater is directly discharged without effective treatment, and the wastewater can cause serious pollution to the receiving water body. The existence form of Zn 2+ in hot galvanizing wastewater is a core problem for limiting the treatment effect. In actual production wastewater, zn 2+ is not entirely present in the free form, and a considerable proportion of Zn 2+ is present in the wastewater in the complex form. On one hand, NH 4+ in the plating assistant agent can be partially converted into free NH 3 under the weak alkaline condition to form a stable zinc ammonia complex with Zn 2+, and on the other hand, auxiliary residues such as an organic corrosion inhibitor, a surfactant and the like used in the production process contain a plurality of coordination groups such as hydroxyl, carboxyl, amino and the like, so that a stable organic complex can be formed with Zn 2+. The complex state Zn 2+ is more stable in thermodynamics than the free state Zn 2+, the condition stability constant is obviously higher than the reciprocal solubility product of precipitates such as Zn (OH) 2, znCO 3 and the like, so that the complex state Zn 2+ can not be effectively converted into the precipitate to be removed in the pH range (pH 8-10) of the conventional alkali precipitation treatment, and the total zinc concentration of the effluent is difficult to reach the standard stably. At present, the main method for industrially treating Zn 2+ in hot galvanizing wastewater is a chemical precipitation method, namely, zn 2+ is converted into Zn (OH) 2 or ZnCO 3 by adding alkaline reagents such as lime, naOH or Na 2CO3, and solid-liquid separation is carried out after precipitation. The method has good removal effect on the free Zn 2+, mature process, simple and convenient operation and low treatment cost, and is widely applied to practical engineering. However, the effect of removing the complex Zn 2+ in the wastewater is very limited, and researches show that when the proportion of the complex Zn 2+ in the wastewater to the total zinc exceeds 20%, the total zinc concentration of the effluent of the alkali precipitation method often exceeds the discharge standard requirement, and the reinforcement treatment is needed by other means. In addition, zn (OH) 2 belongs to amphoteric hydroxide, when the pH of wastewater exceeds 9, zn (OH) 2 is re-dissolved by amphoteric dissolution and re-converted into [ Zn (OH) 4]2- ], so that the concentration of zinc in the effluent is increased, and strict requirements are put on the addition amount and pH control of alkaline reagents. For the treatment of complex heavy metals, researchers have proposed various methods of enhancing the breaking of collaterals. The stripping-oxidation method enables free NH 3 in the wastewater to escape through aeration or heating, so that the balance of zinc ammonia complex is destroyed, but the method is only effective for ammonia complex wastewater, zn 2+ complexed by organic ligands cannot be acted, and ammonia-containing tail gas generated by stripping needs to be treated for the second time, so that the treatment cost is increased. The chemical oxidation method (such as Fenton oxidation and ozone oxidation) can oxidize and degrade the organic complexing ligand so as to release the complexing Zn 2+, but the method has the advantages of large medicament consumption, limited application range to the wastewater quality, higher running cost and poor economy when treating industrial wastewater with large water quantity. The ion exchange method and the membrane separation method have better deep removal capability for Zn 2+, but the former has the problems of frequent resin regeneration and insufficient selectivity, and the latter is easy to cause membrane pollution in hot galvanizing wastewater containing high-concentration suspended matters