CN103043855A - Method for treating low-density polyethylene grafted maleic anhydride wastewater - Google Patents

Abstract

The invention relates to a method for treating low-density polyethylene grafted maleic anhydride wastewater, which comprises the following steps: firstly, adjusting the pH value of the low-density polyethylene grafted maleic anhydride wastewater to acidity, and adding H₂O₂And FeSO₄·7H₂Carrying out Fenton oxidation on O, and adjusting the pH value to be alkaline after the reaction is finished; secondly, placing the wastewater treated in the first step into an electrolytic bath, adjusting the pH value to 2-10, adding electrolyte sodium sulfate into the wastewater, and carrying out electrolytic reaction; and thirdly, placing the wastewater treated in the second step into an SBR reaction tank for reaction, and discharging after repeated aeration and precipitation to finish treatment. The invention is simple and feasible, and the water quality of the treated low-density polyethylene grafted maleic anhydride wastewater reaches the sewage discharge standard, thereby being beneficial to environmental protection.

Description

A kind of treatment method of low-density polyethylene grafted maleic anhydride waste water

technical field

The invention relates to a treatment method for organic wastewater, in particular to a treatment method for low-density polyethylene grafted maleic anhydride wastewater, which belongs to the technical field of sewage treatment.

Background technique

Water is a necessary condition for the survival and development of human beings. With the development of industrial production, the growth of population and other factors, the consumption of water resources is increasing year by year. Due to drought, water pollution and the distribution of water resources in time and region Due to inequality, the contradiction between supply and demand of water resources is intensifying. However, my country is one of the countries with the poorest per capita water resources in the world. In addition, our country has a large population and the distribution of water resources is seriously uneven. Water shortages have occurred in 1/3 of the large and medium-sized cities and some areas in the country. At the same time, the wanton production and domestic wastewater The discharge has worsened the water quality of limited fresh water resources, and the water resource crisis is hanging over our country.

With the rapid development of industries in various countries in the world, the types and discharge of wastewater are increasing day by day, and the composition is more complex. Wastewater often contains a large amount of organic matter that is difficult to biodegrade. Water pollution has become a global problem and a bottleneck restricting global social and economic development. At the same time, the emission standards and regulations on "three wastes" are more stringent. Therefore, it is necessary to develop a purification treatment method with good reliability and high treatment efficiency.

Polyethylene (PE) is currently one of the most widely used plastics. However, the non-polar and inert properties of polyethylene make it less compatible and adhesive with polar polymers, inorganic fillers and metals, which limits its application. Therefore, the functional modification of PE materials and the introduction of polar or functional side chains on the molecular chain have become one of the effective ways to expand the application of PE materials. After the PE macromolecule is modified by grafting, the reaction function and polarity are enhanced, and it shows good compatibility with other polar substances. The grafted polar groups (such as MAH) become the connection bridge between polyolefin and polar substances, and play a great role in the fields of PE alloys and blends, composite materials, adhesives and coatings. Therefore, it is widely used in the fields of composite materials, adhesives and coatings.

The modification of PE by suspension grafting is a simple and effective method to improve the function of PE. Therefore, it has received more and more attention from scholars in recent years, and its application in engineering has become more and more extensive. However, the production process of low-density polyethylene suspension grafted maleic anhydride (LDPE-g-MAH) will produce a large amount of organic wastewater. Generally, more than 7 tons of wastewater will be generated per ton of product produced. This type of wastewater contains a small amount of surfactants. , dispersant and a large amount of MAH, with high COD value and poor biochemical properties. If such waste water is discharged directly, it will cause serious pollution to the surrounding life and environment.

Fenton's reagent can effectively oxidize and remove refractory organic matter that cannot be removed by traditional wastewater treatment technology, and degrade macromolecular organic matter into small molecular organic matter or mineralize into inorganic matter such as C0 ₂ and H ₂ O. However, the cost of single-use Fenton oxidation method is high, and it is difficult to completely decompose organic matter. In January 2012, Li Qian of our research group published an article titled "Fenton Reagent Oxidation Method for Pretreatment of LDPE-g-MAH Process Wastewater" in the Journal of Nanjing University of Technology (Natural Science Edition), which discussed the use of Fenton Reagent Oxidation pretreatment of low-density polyethylene suspension grafted maleic anhydride wastewater is the best condition for various influencing factors, but the treated wastewater has not yet reached GB8978-1996 "Comprehensive Wastewater Discharge Standard".

After searching, it is found that the treatment method of low-density polyethylene grafted maleic anhydride wastewater is rarely reported, and the method of treating low-density polyethylene grafted maleic anhydride wastewater to meet discharge standards has not been reported.

Contents of the invention

The technical problem to be solved by the present invention is: to overcome the problems existing in the prior art, and to provide a treatment method for low-density polyethylene grafted maleic anhydride wastewater.

The technical scheme that the present invention solves its technical problem is as follows:

A kind of processing method of low-density polyethylene grafted maleic anhydride waste water, it is characterized in that, comprises the following steps:

The first step is to adjust the pH value of the low-density polyethylene grafted maleic anhydride wastewater to acidity, put in H ₂ O ₂ and FeSO ₄ 7H ₂ O for Fenton oxidation, and adjust the pH value to alkaline after the reaction;

In the second step, the wastewater treated in the first step is placed in the electrolytic cell, the pH value is adjusted to 2-10, and the electrolyte sodium sulfate is added to the wastewater to carry out the electrolytic reaction;

In the third step, the wastewater treated in the second step is placed in the SBR reaction device for reaction, and discharged after repeated aeration and sedimentation, and the treatment is completed.

The further perfect technical scheme of the present invention is as follows:

1. In the first step, the H ₂ O ₂ is added in batches.

2. In the third step, the aeration is non-restrictive aeration.

3. The specific process of the first step is: take the low-density polyethylene grafted maleic anhydride wastewater with a volume of V, adjust the pH value of the wastewater to 2.0-6.0, keep stirring, and add 30% to the wastewater in batches at the same time H ₂ O ₂ , and then add FeSO ₄ 7H ₂ O to the wastewater according to the molar ratio n(H ₂ O ₂ )/n(Fe ²⁺ )=4:1～20:1 to carry out Fenton oxidation reaction, the reaction time 10 to 60 minutes; after the reaction, adjust the pH value to 8.0 to 9.0 with NaOH solution; add 30% H ₂ O ₂ at least three times, and the amount of each addition is 1-2% of the wastewater volume V. The total amount of addition is 4-8% of the waste water volume V, and the interval between two adjacent additions is at least 10 minutes.

4. The specific process of the second step is: place the wastewater treated in the first step in the electrolytic cell, adjust the pH value to 2-10; add electrolyte sodium sulfate to the wastewater to a final concentration of 3.75-8.75g/ L, keep stirring to carry out electrolysis reaction; the electrode plate distance of the electrolytic cell is 22-38mm, the cell voltage is 6-15V, and the reaction time is 20-100 minutes.

5. The specific process of the third step is: first adjust the pH value of the wastewater treated in the second step to 6-8, and then pump all the wastewater into the anoxic zone of the SBR reaction device at a rate of 3-8L/hour , stuffy exposure and stirring for at least 4 hours, then settling for at least 1 hour; then put all the wastewater into the SBR tank of the SBR reaction device, aerate for 4-12 hours, and at the same time make the dissolved oxygen DO value in the SBR tank greater than 2mg/L; aeration After the end, let it settle for 30 to 120 minutes, discharge the waste water, and complete the treatment.

6. In the third step, the water temperature of the constant temperature water bath used by the SBR reactor to accommodate the anoxic zone and the SBR tank is 25±5°C, and the sludge concentration in the anoxic zone of the SBR reactor and the SBR tank is 0.64-2.97g/L .

After repeated research and exploration by the applicant, it was surprisingly found that using the above-mentioned three methods in combination to treat low-density polyethylene grafted maleic anhydride wastewater in the above order can make its water quality reach the sewage discharge standard, which is a large-scale in the follow-up industrial production. Large-scale wastewater treatment provides basic data and technical support, which has important practical significance for promoting environmental protection.

In addition, the treatment method of the low-density polyethylene grafted maleic anhydride wastewater of the present invention is simple and feasible, has good treatment effect, and has good social and economic benefits.

Description of drawings

Fig. 1 is a structural diagram of the SBR reaction device in the embodiment of the present invention.

Detailed ways

The present invention will be further described in detail below with reference to the accompanying drawings and examples. However, the invention is not limited to the examples given.

Example

The treatment method of present embodiment low-density polyethylene graft maleic anhydride wastewater comprises the following steps:

1) Take low-density polyethylene grafted maleic anhydride wastewater with a volume of V (V=200ml in this example) into a container (such as a beaker, reaction kettle, reaction pool, etc.), and adjust the pH value of the wastewater to 2.0-6.0 , keep stirring, and at the same time add 30% H ₂ O ₂ to the waste water in batches, and then add it to the waste water according to the molar ratio n(H ₂ O ₂ )/n(Fe ²⁺ )=4:1～20:1 FeSO ₄ ·7H ₂ O, carry out Fenton oxidation reaction, the reaction time is 10-60 minutes; after the reaction is finished, adjust the pH value to 8.0-9.0 with NaOH solution.

Among them, 30% H ₂ O ₂ is added at least three times, and the amount of each addition is 1-2% of the wastewater volume V, and the total amount of addition is 4-8% of the wastewater volume V. The interval between two adjacent additions for at least 10 minutes. Specifically, the present embodiment is administered three times, 4ml, 4ml, and 2ml at intervals of 10 minutes, totaling 10ml.

2) Put the wastewater treated in the first step in the electrolytic cell, adjust the pH value to 2-10; add the electrolyte sodium sulfate to the wastewater to a final concentration of 3.75-8.75g/L, keep stirring, and carry out the electrolytic reaction; The pole plate spacing of the electrolytic cell is 22-38mm, the cell voltage is 6-15V, and the reaction time is 20-100 minutes.

3) First adjust the pH value of the wastewater treated in the second step to 6-8, and then pump all the wastewater into the anoxic zone of the SBR reaction device at a rate of 3-8L/hour (4L/hour in this example) , stuffy exposure and stirring for at least 4 hours, then settling for at least 1 hour; then put all the wastewater into the SBR tank of the SBR reaction device, aerate for 4-12 hours, and at the same time make the dissolved oxygen DO value in the SBR tank greater than 2mg/L; aeration After the end, let it settle for 30 to 120 minutes, and then pump out the discharged wastewater through a peristaltic pump to complete the treatment.

As shown in Figure 1, the used SBR reaction device of the present embodiment comprises a constant temperature water bath, is placed in the anoxic zone and the SBR tank in the constant temperature water bath, and there is an air pipeline connected with an external air pump in the SBR tank, and the air pipeline has the function of controlling dissolved oxygen in the SBR tank. DO value rotameter; the anoxic tank has a waste water pipeline connected to an external water inlet device, and the waste water pipeline has a peristaltic pump; the SBR tank also has a sampling port 1 and a sampling port 2, which are used to connect with the external water outlet device through the drainage pipe. The drain line has a peristaltic pump. The above three steps can run a cycle every day.

Table 1 The COD value and MAH concentration of wastewater after each treatment step and the removal rate of COD and MAH

The water quality treated by the method of this embodiment has reached the sewage discharge standard.

In addition to the above-mentioned embodiments, the present invention can also have other implementations. All technical solutions formed by equivalent replacement or equivalent transformation fall within the scope of protection required by the present invention.

Claims (7)

1. a treatment method of low-density polyethylene grafted maleic anhydride waste water, is characterized in that, comprises the following steps: The first step is to adjust the pH value of the low-density polyethylene grafted maleic anhydride wastewater to acidity, put in H ₂ O ₂ and FeSO ₄ 7H ₂ O for Fenton oxidation, and adjust the pH value to alkaline after the reaction; In the second step, the wastewater treated in the first step is placed in the electrolytic cell, the pH value is adjusted to 2-10, and the electrolyte sodium sulfate is added to the wastewater to carry out the electrolytic reaction; In the third step, the wastewater treated in the second step is placed in the SBR reaction device for reaction, and discharged after repeated aeration and sedimentation, and the treatment is completed. 2. according to the processing method of the described low-density polyethylene grafted maleic anhydride waste water of claim 1, it is characterized in that, in the first step, described H ₂ O ₂ The dosing mode is gradation dosing. 3. according to the processing method of the described low density polyethylene graft maleic anhydride wastewater of claim 2, it is characterized in that, in the 3rd step, described aeration is unrestricted aeration. 4. according to the processing method of the described low-density polyethylene grafted maleic anhydride wastewater of claim 1, it is characterized in that, the concrete process of the first step is: get the low-density polyethylene grafted maleic anhydride wastewater that volume is V , adjust the pH value of the wastewater to 2.0-6.0, keep stirring, and add 30% H ₂ O ₂ to the wastewater at the same time, and then according to the molar ratio n(H ₂ O ₂ )/n(Fe ²⁺ )=4: 1～20:1 FeSO ₄ 7H ₂ O is added to the wastewater to carry out Fenton oxidation reaction, the reaction time is 10～60 minutes; after the reaction, adjust the pH value to 8.0～9.0 with NaOH solution; 30% H ₂ Dosing of _O2 at least three times, each dosage is 1-2% of the wastewater volume V, the total dosage is 4-8% of the wastewater volume V, and the interval between two adjacent dosages is at least 10 minutes. 5. according to the processing method of the described low-density polyethylene grafted maleic anhydride waste water of claim 1, it is characterized in that, described second step specific process is: the waste water treated through the first step is placed in electrolyzer, adjusts The pH value is 2-10; the electrolyte sodium sulfate is added to the wastewater to a final concentration of 3.75-8.75g/L, and the electrolytic reaction is carried out with continuous stirring; the distance between the plates of the electrolytic cell is 22-38mm, and the cell voltage is 6 ～15V, the reaction time is 20～100 minutes. 6. according to the processing method of the described low-density polyethylene graft maleic anhydride waste water of claim 1, it is characterized in that, the concrete process of the 3rd step is: first the waste water pH value that is processed through the second step is adjusted to 6- 8. Pump all the wastewater into the anoxic zone of the SBR reactor at a rate of 3-8L/hour, expose and stir for at least 4 hours, then let it settle for at least 1 hour; then put all the wastewater into the SBR of the SBR reactor In the pool, aerate for 4-12 hours, and at the same time make the dissolved oxygen DO value in the SBR pool greater than 2mg/L; after the aeration is completed, let it settle for 30-120 minutes, and then discharge the wastewater to complete the treatment. 7. according to the processing method of the described low-density polyethylene graft maleic anhydride waste water of claim 6, it is characterized in that, in the 3rd step, the water temperature of the constant temperature water bath that SBR reaction unit is used to accommodate anoxic zone and SBR pool is 25 ±5°C, the sludge concentration in the anoxic zone of the SBR reactor and in the SBR tank is 0.64-2.97g/L.

Images