JPS607952B2 - Method for treating wastewater containing polyvinyl alcohol - Google Patents

Description

[Detailed description of the invention] The present invention uses polyvinyl alcohol (hereinafter abbreviated as PVA).

) is brought into contact with oxygen in the presence of a Raney steel catalyst to oxidatively decompose PVA, thereby removing PVA from wastewater. In recent years, PVA has been widely used in films, paper coatings, warp glues, textile processing agents, adhesives, and the like.

In particular, PVA is often used as a warp sizing agent because it is a water-soluble synthetic polymer. However, when used as a thread sizing agent, it is necessary to wash the sizing after weaving, and PVA dissolves into the desizing washing wastewater. PVA has a low detection rate for biological oxygen demand (BOD), but has a low detection rate for chemical oxygen demand (C
Since the detection rate of OD) is high, treatment is required when discharging this PVA-containing wastewater. To date, the method of removing PVA from wastewater is to add PVA-assimilating bacteria to activated sludge and perform microbial decomposition (Hakama Kosho 55-82).
36-823y, Japanese Patent Publication No. 55-28756), a method of microbial decomposition using PVA assimilating bacteria (Hakama Kosho 5
5-123118), a method of concentrating and recovering PVA wastewater (Japanese Patent Publication No. 55-18551), and a method of adding and removing metal salts after irradiating PVA wastewater with electromagnetic radiation (Japanese Patent Publication No. 55-32436) Publication No.) etc. have been proposed.

However, the method of adding PVA assimilating bacteria to activated sludge to decompose it has disadvantages specific to microbial reactions, such as maintaining a pH suitable for microbial treatment and adding nutrients (nitrogen, phosphorus, etc.).
In addition to requiring complicated operations such as adjusting the activated sludge concentration (MBS) and treating excess sludge, there are various problems such as the need for dilution when the PVA concentration is high and the long contact time required for microbial decomposition. It has drawbacks and cannot be called an appropriate treatment method for PVA.

In addition, the method of decomposing PVA using only PVA-assimilating bacteria requires the growth of the assimilating bacteria using a culture solution containing nutrients and inorganic salts, and is therefore unsuitable for treating PVA-containing wastewater on a large scale.

Furthermore, even if a large amount of PVA-containing wastewater could be treated, since it is the same treatment method as the above-mentioned activated sludge method, it would have the same drawbacks. The method for concentrating and recovering PVA-containing wastewater is as follows:
This is a method of concentrating PVA-containing wastewater to a PVA concentration of 2 to 15% by weight through a concentration operation such as heating, and then fog-drying it to recover PVA, but heating concentration and fog-drying consume a large amount of energy. There are drawbacks such as. A method of removing PVA by adding metal salts to wastewater after irradiating it with ionizing radiation is a method of irradiating wastewater with radiation, adding metal salts, and separating the resulting sludge into solid-liquid, but it is not harmful to the human body. There are disadvantages such as the need to use radiation and the need to take into account the treatment of the generated sludge.

In order to overcome these drawbacks of conventional PVA treatment techniques and treat PVA-containing wastewater in a short time and effectively, the present inventors have developed a method of oxidizing PVA-containing wastewater in the presence of porous copper. was developed.

(Patent Application No. 55-62292). However, this method did not yield satisfactory results when the PVA concentration was high, so further research was conducted and the present invention was completed. The present invention is characterized in that wastewater containing polyvinyl alcohol is brought into contact with one or more selected from the group consisting of pure oxygen, oxygen-containing gas, and oxygen-generating substances in the presence of a Raney steel catalyst. The present invention provides a method for treating wastewater containing polyvinyl alcohol.

The Raney steel catalyst used in the present invention is an aqueous alkaline solution such as sodium hydroxide or an aqueous acid solution such as hydrochloric acid applied to an alloy of copper and metals such as magnesium, aluminum, zinc, iron, nickel, tin, and lead. The amount of metals other than copper eluted by alkali or acid is not particularly limited.

Further, the weight ratio of copper to other metals is usually 1:1, but it is not limited to this ratio. An example of a Raney steel catalyst preparation method is that when a sodium hydroxide aqueous solution is applied to a copper-aluminum alloy at a weight ratio of 1:1, the elution reaction occurs rapidly, and more than 90% of the aluminum in the alloy is eluted. A Raney steel catalyst is obtained. In this way, the Raney copper catalyst becomes porous due to the elution of metals other than copper. The Raney copper catalyst obtained as described above is usually prepared to have a particle size of about 200 mesh from the standpoint of strength, but it is desirable to select an appropriate particle size depending on the contact reaction method with PVA-containing wastewater, and this is not necessarily the case. There is no need to be concerned about granularity. Next, the method of contacting the PVA-containing wastewater with the Raney copper catalyst is not particularly limited, and any method such as complete mixing, fixed bed, fluidized bed, or moving bed may be used.

Further, the oxygen required for oxidative decomposition may be dissolved in advance in raw water containing PVA-containing wastewater, or may be supplied in a reaction tank, and there are no particular limitations. Further, the oxygen may be pure oxygen gas, liquid oxygen, air, oxygen-containing waste gas, oxygen-generating substances such as hydrogen peroxide, etc., and may be used alone or in combination. The amount of oxygen supplied is based on the CO of PVA-containing wastewater to be treated on the basis of dissolved oxygen (DO).
It is sufficient to supply 1.2 times the amount of D or more.

Further, the reaction temperature and reaction pressure may be normal temperature or normal pressure, and there is no need to particularly raise the temperature or apply pressure. According to the present invention, PVA in PVA-containing wastewater can be easily removed by oxidative decomposition using oxygen in the presence of a Raney copper catalyst at room temperature and pressure. It has the advantage that it does not require complicated operations and can be disassembled in a short time. Furthermore, the reaction equipment is also smaller compared to microbial treatment. Furthermore, there is no need for the concentration operation as seen in Japanese Patent Publication No. 55-18551, and low-concentration products can be processed as they are.

Furthermore, unlike Japanese Patent Publication No. 55-32436, dangerous radiation is not used and sludge is not generated.
Furthermore, when the Raney copper catalyst contains aluminum, iron, etc., these are oxidized and eluted as hydroxides, which have the effect of coagulating suspended substances in wastewater. The present invention will be explained in detail below using examples. Example 1
1.3 liters of four types of PVA-containing wastewater with different concentrations (average degree of polymerization of PVA 2.000) were placed in each beaker,
Raney steel catalyst (particle size 200 mesh, copper content 96
．． 2Wt%, aluminum content 3. After adding 30 cc of PVA (manufactured by Kawaken Fine Chemicals), an oxidative decomposition experiment of PVA was conducted while expanding the frame by blowing air.

The results are shown in Table 1. As is clear from Table 1, approximately 180
It can be seen that most of the PVA-containing wastewater with a COD of about 100 to 400 feet was oxidized and decomposed with a contact time of 1 minute.

Table 1 TOO: Total organic carbon Example 2 In order to conduct a life test of Raney copper catalyst (same as Example 1), PVA-containing wastewater (average polymerization degree of PVA 2.00
0, COD approx. 10 melon blood) 1.3 Take the 2 pieces into a beaker, add 30cc of Raney steel catalyst, oxidize the PVA while blowing air, and after 3 hours of reaction, discard the treated water and make a new one. 1.3 liters of PVA-containing wastewater was added to the solution, and the same treatment was repeated nine times.

Note that the Raney steel catalyst lost during sampling was replenished for each repeated experiment, and the amount of catalyst in each experiment was always kept constant. The results are shown in Table 2. Table 2 As is clear from Table 2, even after 9 repeated experiments, the PV
It can be seen that most of A was oxidized and decomposed, and the catalyst was not deteriorated.

Further, since the amount of copper eluted in the treated water is 0.4 feet on average, there is no particular problem in terms of discharge. Comparative Example PVA-containing wastewater was treated using porous copper instead of Raney steel catalyst.

The results are shown in Table 3 together with the treatment results using the Raney steel catalyst. As is clear from Table 3, P with a COD of about 10Q
VA-containing wastewater can be oxidized and decomposed even with porous copper, but wastewater containing high concentrations of PVA cannot be sufficiently treated with porous copper.

Claims (1)

[Claims] 1. Polyvinyl alcohol, which is characterized by contacting wastewater containing polyvinyl alcohol with one or more selected from the group consisting of pure oxygen, oxygen-containing gas, and oxygen-generating substances in the presence of a Raney copper catalyst. Method for treating alcohol-containing wastewater.