JPS5814272B2 - Method for treating aqueous wastewater containing dithiocarbamates - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a treatment method for removing aqueous wastewater containing dithiocarbamates using water-soluble copper salts or water-soluble iron salts.

More specifically, by treating an aqueous waste solution containing a dithiocarbamate with a water-soluble copper salt or a water-soluble iron salt at pH 1 to 11, the copper salt or iron salt of the dithiocarbamate is precipitated and separated and removed from the waste solution. The present invention relates to a method for treating dithiocarbamates characterized by:

Generally, wastewater containing dithiocarbamates produced in the chemical industry is treated physically, chemically, or biologically, but organic substances in industrial wastewater have recently been strictly regulated, and if they exceed the regulated value, It is inevitable that operations will be halted.

The activated sludge method, which is a biological treatment method, is a widely used treatment method because it has the effect of removing organic matter.

It is extremely difficult to treat wastewater containing dithiocarbamates by the activated sludge method, which is a biological treatment method, because of its strong bactericidal action whether it is acidic, neutral or alkaline.

When subjecting wastewater containing dithiocarbamates to activated sludge treatment, a huge amount of dilution water is required depending on the concentration of dithiocarbamates, and in some cases, residual dithiocarbamate weakens the activity of bacteria, so it is not practical. In many cases, it is difficult to apply biological treatment methods.

Many methods such as adsorption/extraction and ion exchange methods have been applied to treat waste liquids containing dithiocarbamates, but all of them have drawbacks such as equipment costs, economic efficiency, and effectiveness.

As a result of various studies, the present inventors have found that when a waste liquid containing dithiocarbamates at pH 1 to 11 is treated with a water-soluble copper salt or a water-soluble iron salt at a temperature of -10 to 100°C, the dithiocarbamates contained are I found that it was almost completely removed.

Considering that the copper or iron salts of dithiocarbamates are obtained by substitution reactions, this is an outstanding feature of the copper or iron salts of dithiocarbamates that are usually in a suspended state in dilute solutions. However, it is unexpected and surprising that large floc-like precipitates with extremely good sedimentation properties would be obtained in dilute solutions such as industrial wastewater.

Such crystals have desirable properties and can be easily separated from the waste liquid by Sawabetsu.

Therefore, the waste liquid treatment equipment does not require any special equipment, and since it is possible to recover the chemicals, the treatment cost is low compared to other treatment methods, which is extremely advantageous.

It is also extremely easy to recover copper or iron from the separated residue.

The method of the present invention will be described in detail below.

Aqueous wastewater containing dithiocarbamates has a pH of 1 to 11.
Add a water-soluble copper salt or an aqueous solution of a water-soluble copper salt to -
Stir at 10-100°C.

After the reaction completes precipitation of solid matter, stirring is stopped and the precipitate separates into the lower layer.

This is filtered and separated from the waste liquid.

In adjusting the pH, acids and alkalis include sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, etc. for acidification.

Examples of the alkali for alkalinization include caustic soda, caustic potash, soda carbonate, potassium carbonate, quicklime, slaked lime, and ammonia.

Both can be treated in solid form or in solution.

As water-soluble copper salts or water-soluble iron salts, copper sulfate, copper chloride, copper nitrate, ferrous sulfate, ferric chloride alum, mixtures of these salts, or solutions of several salts are used. Good too.

Although dithiocarbamate can be treated in a range from a very small amount to around 10%, it is economically preferable to use it in a range of several percent.

By changing the amount of water-soluble salts used and treatment conditions depending on the dithiocarbamate content, the dithiocarbamate content can be reduced to several ppm or less.

When the content of dithiocarbamate is large, it is preferable from the viewpoint of processing operation and economic efficiency to adjust the pH to 7 or less to precipitate most of the content as free dithiocarbamate, and then to treat it.

Residual water-soluble salts are extremely small if used properly;
Moreover, if the treated water is made alkaline, it can be removed at the same time as insoluble hydroxide.

The waste residue can be incinerated, and the residue can be treated with sulfuric acid, hydrochloric acid, nitric acid, etc. to recover it as a water-soluble salt, and the recovered copper salt or iron salt can of course be recycled.

The composition of the produced substance is complex and not clear, but it is presumed to contain copper or iron salts of dithiocarbamates, free dithiocarbamates, copper sulfide, or iron sulfide.

The present invention will be explained below with reference to Examples.

Example 1 Ethylene bisdiocarbamate 1 4 0 0 0 p
5 to 1 per 1000 parts by weight of waste liquid containing pm (waste liquid A)
While stirring at 0° C., 25 parts by weight of a 30% aqueous copper sulfate solution was added.

After stirring for 10 minutes, the stirring was stopped, and the treated material became a floc-like substance and was easily separated from water.

The precipitate was separated from the sap liquid using swab paper. This solution is designated as X-1.

Further, 1.5 parts by weight of a 37% ferric chloride aqueous solution was added dropwise to 1000 parts by weight of the above waste liquid at 5 to 10°C with stirring.
Stirring was continued for an hour.

After the stirring was stopped, the treated product became a floc-like substance and was easily separated from water.

The precipitate was separated from the r liquid using paper.

This solution is designated as sample Y-1. Example 2 2.5 parts by weight of concentrated sulfuric acid was added dropwise to 1000 parts by weight of a waste liquid containing 14000 ppm of ethylene bisdithiocarbamate while stirring at 5 to 10°C.

After stirring for 10 minutes, the treated product becomes a floc of 2 to 5 mm and is easily separated from the water.

The precipitate was separated from the r liquid by filtration using filter paper.

Next, 1.0 parts by weight of a 30% aqueous copper sulfate solution was added to the filtrate, and stirring was continued for 10 minutes.

Similarly, 0.58 parts by weight of a 37% ferric chloride aqueous solution was added to the p solution, and stirring was continued for 10 minutes.

In either case, after the stirring was stopped, the treated product became a floc-like substance and was easily separated from water.

The precipitate was filtered through filter paper and separated from the filtrate.

The former sample is referred to as X-2, and the latter sample is referred to as Y~2.

Example 3 Waste liquid 10 containing 28 ppm dimethyldithiocarbamate
00 parts by weight (waste liquid B), 0.4 parts by weight of 30% copper sulfate aqueous solution, 0.55 parts by weight of iron alum, 0.6 parts by weight of ferric sulfate, and 0.38 parts by weight of ferric chloride, respectively. It was treated in the same manner as in Example 1.

The respective sap liquids were added to X-3, Y''-3, Y-4 and Y-
5.

The spore germination rate of the test example filtrate was measured by the PFT method (Poisoned Food Technique) using Alternaria mali.

The results are shown in the table below. As shown in the above test example, the dithiocarbamate in the untreated waste liquid is almost completely removed as shown in the treated liquid, and the bactericidal activity is completely inhibited in the untreated waste liquid even if it is diluted 10 times. Nevertheless, the treatment solution shows extremely low bactericidal activity even in its original form.

Claims (1)

[Claims] 1. A waste liquid treatment method for removing dithiocarbamates in waste liquid by treating an aqueous waste liquid containing dithiocarbamates with a water-soluble copper salt or a water-soluble iron salt at pH 1 to 11.