Pre-oxidation-flocculent precipitation integrated treatment method for high-concentration polyvinyl alcohol wastewater

Abstract

The invention discloses a pre-oxidation-flocculation precipitation integrated treatment method for high-concentration polyvinyl alcohol wastewater, which comprises the following steps: adjusting the pH value of desizing wastewater by using hydrochloric acid, sequentially adding a ferrous chloride tetrahydrate solution and a calcium peroxide solution into the desizing wastewater for pre-oxidation, stirring at room temperature, and accurately controlling the oxidation degree; and then adjusting the pH value of the desizing wastewater again by using sodium hydroxide or potassium hydroxide, stirring, standing and precipitating, so that the macromolecular pollutants are quickly coagulated and precipitated. According to the PVA-containing desizing wastewater treatment method, H2O2 is released through CaO2 hydrolysis, oxidation active species are generated under the catalysis of Fe < 2 + >, the flocculability of PVA is enhanced, efficient flocculation and sedimentation are achieved through generated Fe < 3 + > and Ca < 2 + >, and the PVA-containing desizing wastewater treatment method is easy and convenient to operate, economical and practical.

Description

Technical Field

[0001] The present invention relates to the technical field of water treatment methods, and in particular to a method based on Fe 2+ An integrated treatment method of "pre-oxidation-flocculation sedimentation" for high-concentration polyvinyl alcohol wastewater in / CaO2 system. Background Art

[0002] In recent years, the environmental crisis caused by a large number of discarded polymer products has swept the world. In addition to the well-known "white" pollution and new pollutants such as microplastics, water-soluble synthetic polymers are also quietly invading the environment. Take polyvinyl alcohol (PVA) as an example. It has excellent film-forming properties, adhesion and surface activity, and is one of the most in-demand water-soluble polymers in the world. In my country, more than 20% of PVA is used in weaving pulp in the textile industry. The desizing wastewater generated contains more than 10g / L of PVA, and COD Cr The value is usually above 20000 mg / L and BOD5 / COD is often less than 0.1. Targeted wastewater treatment technology urgently needs breakthroughs.

[0003] PVA has a high degree of polymerization and is rich in hydroxyl groups in its molecular chain. It is easy to form a large number of intramolecular or intermolecular hydrogen bonds in water to form a stable network structure, which is the main reason why its wastewater is difficult to treat. In addition to exploring the fields of functional bacteria domestication, cross-linking precipitation and advanced oxidation processes (AOPs), researchers have also tried to recycle PVA through membrane separation, but the cost bottleneck is still difficult to overcome. In contrast, the use of AOPs technology such as Fenton to pretreat high-concentration PVA wastewater promotes the breakage of long chains of PVA and oxidation to generate aldehyde, ketone, and carboxyl structures, and then uses conventional flocculation treatment, which is cost-effective (PAN YT, LIU YB, WU DL, et al. Journal of Hazardous Materials, 2020, 389: 121866). However, the two-stage treatment operation of "pre-oxidation-flocculation precipitation" is relatively cumbersome, and the transformation requirements of the original physical and chemical treatment facilities of the enterprise are also high (Li Fang, et al. A pre-oxidation-high-efficiency coagulation method for desizing wastewater containing polyvinyl alcohol: CN109133419A). Therefore, it is particularly important to develop a technology that can integrate pre-oxidation and flocculation. Summary of the invention

[0004] The purpose of the present invention is to provide an economical and feasible method for integrated "pre-oxidation-flocculation sedimentation" treatment of desizing wastewater containing PVA, so that the PVA concentration and COD value of the desizing wastewater are effectively reduced, the slurry pollutants are quickly precipitated and separated, so as to improve the bottleneck of low treatment efficiency of desizing wastewater containing PVA.

[0005] At present, the oxidation system based on CaO2 has shown unique advantages in pollutant removal due to its special oxidation mechanism and composite properties. After CaO2 is hydrolyzed in water, it can release H2O2 evenly and slowly, and with the assistance of a catalyst, it can generate strong oxidizing active species such as hydroxyl radicals (·OH), which can efficiently oxidize difficult-to-degrade organic pollutants. Based on this, the present invention designs a type of Fe 2+ / CaO2 treatment system, integrated "pre-oxidation-flocculation sedimentation" treatment of high-concentration polyvinyl alcohol wastewater.

[0006] A "pre-oxidation-flocculation precipitation" integrated treatment method for high-concentration polyvinyl alcohol wastewater comprises the following steps:

[0007] The pH value of the desizing wastewater is adjusted with hydrochloric acid, and ferrous chloride tetrahydrate solution and calcium peroxide solution are sequentially added to the desizing wastewater for pre-oxidation, and stirred at room temperature to precisely control the degree of oxidation; then, the pH value of the desizing wastewater is adjusted again with sodium hydroxide or potassium hydroxide, and the water is allowed to stand and precipitate after stirring, so that the high molecular weight pollutants are quickly precipitated.

[0008] Compared with the prior art, the beneficial effects of the present invention are as follows: the treatment method of the present invention is carried out at normal temperature and pressure, and H2O2 is produced by hydrolysis of CaO2. 2+ PVA is pre-oxidized under the catalytic action of , which improves the difficulty of PVA flocculation and precipitation. 3+ and Ca 2+ As a flocculant, it promotes the efficient precipitation of PVA after pre-oxidation, thereby realizing the integrated treatment of "pre-oxidation-flocculation precipitation" of PVA-containing desizing wastewater. This method is simple, easy to operate, and environmentally friendly. It can significantly improve the COD removal efficiency of PVA-containing desizing wastewater. It has great application potential in the field of textile dyeing and finishing wastewater treatment, and has good development prospects in the treatment of printing and dyeing desizing wastewater or other PVA-containing industrial wastewater. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 This is a diagram showing the phenomenon of pre-oxidation-coagulation treatment using actual desizing wastewater containing polyvinyl alcohol. DETAILED DESCRIPTION

[0010] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0011] A "pre-oxidation-flocculation precipitation" integrated treatment method for high-concentration polyvinyl alcohol wastewater comprises the following steps:

[0012] The pH value of the desizing wastewater is adjusted with hydrochloric acid, and ferrous chloride tetrahydrate solution and calcium peroxide solution are sequentially added to the desizing wastewater for pre-oxidation, and stirred at room temperature to precisely control the degree of oxidation; then, the pH value of the desizing wastewater is adjusted again with sodium hydroxide or potassium hydroxide, and the water is allowed to stand and precipitate after stirring, so that the high molecular weight pollutants are quickly precipitated.

[0013] Preferably, in the treatment method of the present invention, the concentration range of fabric slurry in the desizing wastewater is: polyvinyl alcohol content is 0-5 g / L, and the concentration of starch is 0-3 g / L.

[0014] Preferably, in the treatment method of the present invention, the pH value of the desizing wastewater is adjusted in the range of 2-4 using hydrochloric acid.

[0015] Preferably, in the treatment method of the present invention, during pre-oxidation, the dosage of the ferrous chloride tetrahydrate solution is 20 mmol / L-50 mmol / L; and the dosage of the calcium peroxide solution is 2-10 mmol / L.

[0016] Preferably, in the treatment method of the present invention, the pre-oxidation reaction time is 5-120 min.

[0017] Preferably, in the treatment method of the present invention, when the pH value of the desizing wastewater is adjusted again, the adjustment range of the pH value is 9-12.

[0018] Preferably, in the treatment method of the present invention, when the pH value of the desizing wastewater is adjusted again, the concentration of the sodium hydroxide or potassium hydroxide solution used is 0.1-4 mol / L.

[0019] Preferably, in the treatment method of the present invention, the stirring time before static sedimentation is 5-15 minutes.

[0020] Figure 1 This is a phenomenon diagram of pre-oxidation-coagulation treatment using actual desizing wastewater containing polyvinyl alcohol. The desizing wastewater before treatment is shown on the left side of the figure. The solution is milky white and thick, containing a large number of white flocs. After the integrated treatment of "pre-oxidation-flocculation precipitation", the supernatant of the wastewater is clarified, and the macromolecules such as PVA and starch in the water are separated. Most of the iron ions added during the pre-oxidation process are polymerized and precipitated, and the COD in the desizing wastewater is significantly reduced. The lower precipitate is brown-green, as shown on the right side of the figure.

[0021] The process of pre-oxidation-coagulation treatment of desizing wastewater containing polyvinyl alcohol according to the present invention is described in detail below with reference to specific embodiments.

[0022] Example 1

[0023] Take 50 mL of desizing wastewater containing 2 g / L PVA concentration and 1 g / L starch concentration, adjust the pH of the PVA solution to 3, add 20 mmol / L ferrous chloride tetrahydrate solution, and then add 2 mmol / L calcium peroxide solution, stir at room temperature for 30 minutes, adjust the solution pH to 10 after stirring, stir evenly at room temperature, let it stand after the reaction is completed, and determine the removal rates of PVA, starch and COD in the supernatant.

[0024] Example 2

[0025] Take 50 mL of desizing wastewater containing 2 g / L PVA concentration and 1 g / L starch concentration, adjust the pH of the PVA solution to 3, add 30 mmol / L ferrous chloride tetrahydrate solution, and then add 2 mmol / L calcium peroxide solution, stir at room temperature for 30 minutes, adjust the solution pH to 10 after stirring, stir evenly at room temperature, let it stand after the reaction is completed, and determine the removal rates of PVA, starch and COD in the supernatant.

[0026] Example 3

[0027] Take 50 mL of desizing wastewater containing 2 g / L PVA concentration and 1 g / L starch concentration, adjust the pH of the PVA solution to 3, add 50 mmol / L ferrous chloride tetrahydrate solution, and then add 2 mmol / L calcium peroxide solution, stir at room temperature for 30 minutes, adjust the solution pH to 10 after stirring, stir evenly at room temperature, let it stand after the reaction is completed, and determine the removal rates of PVA, starch and COD in the supernatant.

[0028] Comparative Example 1

[0029] Take 50 mL of desizing wastewater containing 2 g / L PVA concentration and 1 g / L starch concentration, adjust the pH of the PVA solution to 3, add 5 mmol / L ferrous chloride tetrahydrate solution, and then add 2 mmol / L calcium peroxide solution, stir at room temperature for 30 minutes, adjust the solution pH to 10 after stirring, stir evenly at room temperature, let it stand after the reaction is completed, and determine the removal rates of PVA, starch and COD in the supernatant.

[0030] Comparative Example 2

[0031] Take 50 mL of desizing wastewater containing 2 g / L PVA concentration and 1 g / L starch concentration, adjust the pH of the PVA solution to 3, add 10 mmol / L ferrous chloride tetrahydrate solution, and then add 2 mmol / L calcium peroxide solution, stir at room temperature for 30 minutes, adjust the solution pH to 10 after stirring, stir evenly at room temperature, let it stand after the reaction is completed, and determine the removal rates of PVA, starch and COD in the supernatant.

[0032] Comparative Example 3

[0033] Take 50 mL of desizing wastewater containing 2 g / L PVA concentration and 1 g / L starch concentration, adjust the pH of the PVA solution to 3, add 100 mmol / L ferrous chloride tetrahydrate solution, then add 2 mmol / L calcium peroxide solution, stir at room temperature for 30 minutes, adjust the solution pH to 10 after stirring, stir evenly at room temperature, let it stand after the reaction is completed, and determine the removal rates of PVA, starch and COD in the supernatant.

[0034] The removal rates of COD in the PVA, starch and desizing wastewater solutions were measured in the supernatants after the reactions of Examples 1, 2, 3 and Comparative Examples 1, 2, 3, respectively. The removal results are shown in Table 1.

[0035] Table 1 Effect of the dosage of ferrous chloride tetrahydrate on the treatment efficiency of PVA desizing wastewater

[0036]

[0037]

[0038] As shown in Table 1, when the concentration of ferrous chloride tetrahydrate is between 20mmol / L and 50mmol / L, the removal rates of PVA and COD are relatively good. When the dosage of ferrous sulfate heptahydrate is too small, its ability to catalyze the decomposition of H2O2 to produce ·OH is insufficient; when the dosage is too large, the remaining Fe 2+ It will competitively consume ·OH, and the oxidation efficiency will also be reduced; both will lead to a slow reaction rate of oxidizing PVA, a decrease in oxidation efficiency, and it is not enough to oxidize a large number of hydroxyl groups in the PVA structure into structures such as carboxyl, aldehyde, and ketone, thereby significantly reducing the coagulation efficiency of the second stage. As shown in Comparative Example 3, when an excess of ferrous chloride tetrahydrate solution is added, the removal of PVA and COD in the desizing wastewater is very low. It can be seen that the pre-oxidation of PVA is controlled within an effective range, and the -OH in the PVA structure is oxidized into structures such as carboxyl, aldehyde, and ketone, making it easy to interact with calcium ions, thereby effectively enhancing the coagulation effect.

[0039] Example 4

[0040] Take 50 mL of desizing wastewater containing 2 g / L PVA concentration and 1 g / L starch concentration, adjust the pH of the PVA solution to 3, add 20 mmol / L ferrous chloride tetrahydrate solution, and then add 5 mmol / L calcium peroxide solution, stir at room temperature for 30 minutes, adjust the solution pH to 10 after stirring, stir evenly at room temperature, let it stand after the reaction is completed, and determine the removal rates of PVA, starch and COD in the supernatant.

[0041] Example 5

[0042] Take 50 mL of desizing wastewater containing 2 g / L PVA concentration and 1 g / L starch concentration, adjust the pH of the PVA solution to 3, add 20 mmol / L ferrous chloride tetrahydrate solution, then add 10 mmol / L calcium peroxide solution, stir at room temperature for 30 minutes, adjust the solution pH to 10 after stirring, stir evenly at room temperature, let it stand after the reaction is completed, and determine the removal rates of PVA, starch and COD in the supernatant.

[0043] Comparative Example 4

[0044] Take 50 mL of desizing wastewater containing 2 g / L PVA concentration and 1 g / L starch concentration, adjust the pH of the PVA solution to 3, add 20 mmol / L ferrous chloride tetrahydrate solution, then add 0.4 mmol / L calcium peroxide solution, stir at room temperature for 30 minutes, adjust the solution pH to 10 after stirring, stir evenly at room temperature, let it stand after the reaction is completed, and determine the removal rates of PVA, starch and COD in the supernatant.

[0045] Comparative Example 5

[0046] Take 50 mL of desizing wastewater containing 2 g / L PVA concentration and 1 g / L starch concentration, adjust the pH of the PVA solution to 3, add 20 mmol / L ferrous chloride tetrahydrate solution, and then add 1 mmol / L calcium peroxide solution, stir at room temperature for 30 minutes, adjust the solution pH to 10 after stirring, stir evenly at room temperature, let it stand after the reaction is completed, and determine the removal rates of PVA, starch and COD in the supernatant.

[0047] Comparative Example 6

[0048] Take 50 mL of desizing wastewater containing 2 g / L PVA concentration and 1 g / L starch concentration, adjust the pH of the PVA solution to 3, add 20 mmol / L ferrous chloride tetrahydrate solution, then add 20 mmol / L calcium peroxide solution, stir at room temperature for 30 minutes, adjust the solution pH to 10 after stirring, stir evenly at room temperature, let it stand after the reaction is completed, and determine the removal rates of PVA, starch and COD in the supernatant.

[0049] The removal rates of COD in the PVA, starch and desizing wastewater solutions were measured in the supernatants after the reactions of Examples 3, 4, 5 and Comparative Examples 4, 5 and 6, respectively. The removal results are shown in Table 2.

[0050] Table 2 Effect of calcium peroxide dosage on treatment efficiency of PVA desizing wastewater

[0051]

[0052] As shown in Table 2, when the concentration of calcium peroxide added is between 2mmol / L and 10mmol / L, the removal rates of PVA and COD are both relatively good. With the increase of CaO2 dosage, the removal rate of PVA gradually increases, while the removal rate of COD reaches a peak when the CaO2 concentration is 10mmol / L. Then, with the further increase of CaO2 dosage, the removal rate of PVA remains almost unchanged while the removal rate of COD decreases significantly. CaO2 can not only provide H2O2, an important oxidant in Fenton-like reactions, but also releases Ca 2+ It can also react with H2O2 to generate singlet oxygen 1 O2, 1 The increase of O2 can effectively promote the oxidation of PVA and enhance the subsequent aggregation and precipitation effect under alkaline conditions, but excessive oxidation will be detrimental to the coagulation and precipitation process and reduce the overall removal efficiency of COD.

[0053] Example 6

[0054] Take 50 mL of desizing wastewater containing 2 g / L PVA concentration and 1 g / L starch concentration, adjust the pH of the PVA solution to 2, add 20 mmol / L ferrous chloride tetrahydrate solution, then add 10 mmol / L calcium peroxide solution, stir at room temperature for 30 minutes, adjust the solution pH to 10 after stirring, stir evenly at room temperature, let it stand after the reaction is completed, and determine the removal rates of PVA, starch and COD in the supernatant.

[0055] Example 7

[0056] Take 50 mL of desizing wastewater containing 2 g / L PVA concentration and 1 g / L starch concentration, adjust the pH of the PVA solution to 4, add 20 mmol / L ferrous chloride tetrahydrate solution, then add 10 mmol / L calcium peroxide solution, stir at room temperature for 30 minutes, adjust the solution pH to 10 after stirring, stir evenly at room temperature, let it stand after the reaction is completed, and determine the removal rates of PVA, starch and COD in the supernatant.

[0057] Comparative Example 7

[0058] Take 50 mL of desizing wastewater containing 2 g / L PVA concentration and 1 g / L starch concentration, adjust the pH of the PVA solution to 6, add 20 mmol / L ferrous chloride tetrahydrate solution, then add 10 mmol / L calcium peroxide solution, stir at room temperature for 30 minutes, adjust the solution pH to 10 after stirring, stir evenly at room temperature, let it stand after the reaction is completed, and determine the removal rates of PVA, starch and COD in the supernatant.

[0059] Comparative Example 8

[0060] Take 50 mL of desizing wastewater containing 2 g / L PVA concentration and 1 g / L starch concentration, adjust the pH of the PVA solution to 8, add 20 mmol / L ferrous chloride tetrahydrate solution, then add 10 mmol / L calcium peroxide solution, stir at room temperature for 30 minutes, adjust the solution pH to 10 after stirring, stir evenly at room temperature, let it stand after the reaction is completed, and determine the removal rates of PVA, starch and COD in the supernatant.

[0061] The supernatants after the reaction of Examples 5, 6, 7 and Comparative Examples 7, 8 were respectively taken to measure the removal rates of COD in PVA, starch and desizing wastewater. The removal results are shown in Table 3.

[0062] Table 3 Effect of pre-oxidation pH on treatment efficiency of PVA desizing wastewater

[0063]

[0064]

[0065] As shown in Table 3, when the pH value in the pre-oxidation stage is between 2 and 4, the pre-oxidation effect of the desizing wastewater is good. As the pH value decreases, the removal rate of PVA in the pre-oxidation stage gradually increases, reaching a peak value at a pH of 3. After further reducing the pH value, the removal rate does not change significantly. The COD concentration shows a trend of decreasing first and then increasing as the pH value gradually increases. This may be due to the neutral to weakly alkaline pH conditions, some Fe 2+ / Fe 3+ / Ca 2+ Hydroxide precipitates gradually formed, producing a certain flocculation effect and reducing the COD concentration in the supernatant.

[0066] Example 8

[0067] Take 50 mL of desizing wastewater containing 2 g / L PVA concentration and 1 g / L starch concentration, adjust the pH of the PVA solution to 3, add 20 mmol / L ferrous chloride tetrahydrate solution, then add 10 mmol / L calcium peroxide solution, stir at room temperature for 30 minutes, adjust the solution pH to 9 after stirring, stir evenly at room temperature, let it stand after the reaction is completed, and determine the removal rates of PVA, starch and COD in the supernatant.

[0068] Example 9

[0069] Take 50 mL of desizing wastewater containing 2 g / L PVA concentration and 1 g / L starch concentration, adjust the pH of the PVA solution to 3, add 20 mmol / L ferrous chloride tetrahydrate solution, then add 10 mmol / L calcium peroxide solution, stir at room temperature for 30 minutes, adjust the solution pH to 12 after stirring, stir evenly at room temperature, let it stand after the reaction is completed, and determine the removal rates of PVA, starch and COD in the supernatant.

[0070] Comparative Example 9

[0071] Take 50 mL of desizing wastewater containing 2 g / L PVA concentration and 1 g / L starch concentration, adjust the pH of the PVA solution to 3, add 20 mmol / L ferrous chloride tetrahydrate solution, then add 10 mmol / L calcium peroxide solution, stir at room temperature for 30 minutes, adjust the solution pH to 6 after stirring, stir evenly at room temperature, let it stand after the reaction is completed, and determine the removal rates of PVA, starch and COD in the supernatant.

[0072] Comparative Example 10

[0073] Take 50 mL of desizing wastewater containing 2 g / L PVA concentration and 1 g / L starch concentration, adjust the pH of the PVA solution to 3, add 20 mmol / L ferrous chloride tetrahydrate solution, then add 10 mmol / L calcium peroxide solution, stir at room temperature for 30 minutes, adjust the solution pH to 8 after stirring, stir evenly at room temperature, let it stand after the reaction is completed, and determine the removal rates of PVA, starch and COD in the supernatant.

[0074] In Examples 5, 8, 9 and Comparative Examples 9 and 10, the supernatant after the reaction was taken to measure the removal rate of COD in PVA, starch and desizing wastewater solution. The removal results are shown in Table 4.

[0075] Table 4 Effect of flocculation precipitation pH on treatment efficiency of PVA desizing wastewater

[0076]

[0077] It can be seen from Table 4 that the removal rates of PVA and COD in desizing wastewater are the highest when the pH is 9-12. Since calcium ions and iron ions have low solubility under alkaline conditions, they are more likely to precipitate from wastewater and quickly flocculate after combining with pre-oxidized PVA and starch.

[0078] Example 10

[0079] Take 50 mL of desizing wastewater containing 2 g / L PVA concentration and 1 g / L starch concentration, adjust the pH of the PVA solution to 3, add 20 mmol / L ferrous chloride tetrahydrate solution, then add 10 mmol / L calcium peroxide solution, stir at room temperature for 5 minutes, adjust the solution pH to 10 after stirring, stir evenly at room temperature, let it stand after the reaction is completed, and determine the removal rates of PVA, starch and COD in the supernatant.

[0080] Embodiment 11

[0081] Take 50 mL of desizing wastewater containing 2 g / L PVA concentration and 1 g / L starch concentration, adjust the pH of the PVA solution to 3, add 20 mmol / L ferrous chloride tetrahydrate solution, then add 10 mmol / L calcium peroxide solution, stir at room temperature for 15 minutes, adjust the solution pH to 10 after stirring, stir evenly at room temperature, let it stand after the reaction is completed, and determine the removal rates of PVA, starch and COD in the supernatant.

[0082] Example 12

[0083] Take 50 mL of desizing wastewater containing 2 g / L PVA concentration and 1 g / L starch concentration, adjust the pH of the PVA solution to 3, add 20 mmol / L ferrous chloride tetrahydrate solution, then add 10 mmol / L calcium peroxide solution, stir at room temperature for 60 min, adjust the solution pH to 10 after stirring, stir evenly at room temperature, let stand after the reaction is completed, and determine the removal rates of PVA, starch and COD in the supernatant.

[0084] Example 13

[0085] Take 50 mL of desizing wastewater containing 2 g / L PVA concentration and 1 g / L starch concentration, adjust the pH of the PVA solution to 3, add 20 mmol / L ferrous chloride tetrahydrate solution, then add 10 mmol / L calcium peroxide solution, stir at room temperature for 120 min, adjust the solution pH to 10 after stirring, stir evenly at room temperature, let stand after the reaction is completed, and determine the removal rates of PVA, starch and COD in the supernatant.

[0086] The pre-oxidation stirring reaction time was changed in Example 5, 10, 15, 30, 60, and 120 min. The supernatant was taken to measure the removal rate of COD in PVA, starch, and desizing wastewater solution. The removal results are shown in Table 5.

[0087] Table 5 Effect of pre-oxidation time on treatment efficiency of PVA desizing wastewater

[0088]

[0089]

[0090] As shown in Table 5, when the pre-oxidation time is 5-120min, the removal effects of PVA and COD are both greater than 70%. Moreover, when the pre-oxidation time is less than 15 minutes, the removal rates of PVA and COD increase rapidly, then the growth rate gradually slows down, and stabilizes at 60 minutes. This shows that insufficient pre-oxidation will significantly affect the effect of subsequent flocculation and sedimentation, while sufficient pre-oxidation can significantly improve the aggregation and sedimentation performance of PVA.

[0091] The present invention discloses an integrated treatment method of "pre-oxidation-flocculation precipitation" for high-concentration polyvinyl alcohol wastewater, including: using hydrochloric acid to adjust the pH value of desizing wastewater, adding ferrous chloride tetrahydrate solution and calcium peroxide solution to the desizing wastewater in sequence for pre-oxidation, stirring at room temperature, and accurately controlling the degree of oxidation; then using sodium hydroxide or potassium hydroxide to adjust the pH value of the desizing wastewater again, stirring and then standing to precipitate, so that high-molecular pollutants are rapidly flocculated. The present invention releases H2O2 by hydrolysis of CaO2, and in Fe 2+ Oxidative active species are generated under catalysis, which enhances the flocculation of PVA and generates Fe 3+ and Ca 2+ The method can achieve efficient flocculation and sedimentation, which is an easy-to-operate, economical and practical method for treating PVA desizing wastewater.

Claims

1. A "pre-oxidation-flocculation precipitation" integrated treatment method for high-concentration polyvinyl alcohol wastewater, characterized in that: The following steps are involved: The pH value of the desizing wastewater is adjusted with hydrochloric acid, and ferrous chloride tetrahydrate solution and calcium peroxide solution are sequentially added to the desizing wastewater for pre-oxidation, and the solution is stirred at room temperature to precisely control the degree of oxidation; Then, sodium hydroxide or potassium hydroxide is used to adjust the pH value of the desizing wastewater again, and the wastewater is allowed to settle after stirring, so that the high molecular weight pollutants are rapidly precipitated.

2. The "pre-oxidation-flocculation precipitation" integrated treatment method for high-concentration polyvinyl alcohol wastewater according to claim 1 is characterized in that: The fabric slurry concentration range of the desizing wastewater is: polyvinyl alcohol content is 0-5g / L, and starch concentration is 0-3g / L.

3. The "pre-oxidation-flocculation precipitation" integrated treatment method for high-concentration polyvinyl alcohol wastewater according to claim 1 is characterized in that: The pH value of the desizing wastewater is adjusted in the range of 2-4 using hydrochloric acid.

4. The "pre-oxidation-flocculation precipitation" integrated treatment method for high-concentration polyvinyl alcohol wastewater according to claim 1 is characterized in that: In the pre-oxidation, the dosage of the ferrous chloride tetrahydrate solution is 20 mmol / L-50 mmol / L; the dosage of the calcium peroxide solution is 2-10 mmol / L.

5. The "pre-oxidation-flocculation precipitation" integrated treatment method for high-concentration polyvinyl alcohol wastewater according to claim 1 is characterized in that: The reaction time of the pre-oxidation is 5-120 min.

6. The integrated treatment method of high-concentration polyvinyl alcohol wastewater "pre-oxidation-flocculation precipitation" according to claim 1 is characterized in that: When the pH value of the desizing wastewater is adjusted again, the adjustment range of the pH value is 9-12.

7. The integrated treatment method of high-concentration polyvinyl alcohol wastewater "pre-oxidation-flocculation precipitation" according to claim 1 is characterized in that: When the pH value of the desizing wastewater is adjusted again, the concentration of the sodium hydroxide or potassium hydroxide solution used is 0.1-4 mol / L.

8. The "pre-oxidation-flocculation precipitation" integrated treatment method for high-concentration polyvinyl alcohol wastewater according to claim 1 is characterized in that: The stirring time before the static precipitation is 5-15 minutes.

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