JPS592558B2 - Method for treating aqueous wastewater containing dithiocarbamates - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a process for removing aqueous wastewater containing dithiocarbamates with potassium permanganate.

More specifically, the dithiocarbamate is produced by treating an aqueous waste solution containing the dithiocarbamate with potassium permanganate at pH 1 to 11, thereby decomposing the dithiocarbamate and separating and removing precipitated crystals from the waste solution. This relates to the method of treating wastewater contained in the wastewater.

Generally, wastewater containing dithiocarbamates produced in the chemical industry is treated physically, chemically, or biologically, but dithiocarbamates in industrial wastewater have recently been strictly regulated, and if the concentration exceeds the regulated value, is in a situation where it is inevitable that operations will be suspended.

Wastewater containing dithiocarbamates is extremely difficult to treat by the activated sludge method, which is a biological treatment method, because of its strong bactericidal action in any acidic, neutral or alkaline environment.

When applying wastewater containing these substances to activated sludge treatment, it is necessary to dilute them to a concentration that is no longer sterilizing, and depending on the concentration of these substances, a huge amount of dilution water is required, and in some cases, residual In practice, it is often difficult to apply biochemical treatment because dithiocarbamates and the like weaken the activity of bacteria.

Many other methods such as adsorption, extraction, and ion exchange methods are used to treat waste liquids containing dithiocarbamates, but all of them have drawbacks such as equipment cost, economic efficiency, and effectiveness.

As a result of various studies, the present inventors have found that if waste liquid containing dithiocarbamates at pH 1 to 11 is treated with potassium permanganate at -10 to 100°C,
It has been found that dithiocarbamates are almost completely removed.

When dithiocarbamates are oxidatively decomposed with potassium permanganate, the outstanding feature is that the treatment solution after oxidatively decomposed has almost no organic residue, and post-treatment is extremely easy.

That is, most of the dithiocarbamates are oxidized by potassium permanganate, and manganese mainly precipitates as manganese oxides as large floc-like precipitates with extremely good sedimentation properties, and is absorbed by the tear film without remaining in the water. .

After incineration, the excess p residue is recovered as manganese oxide or further treated as manganese sulfate.

Due to the desirable properties of such precipitate, it can be easily separated from waste liquid by furnace separation.

Therefore, the waste liquid treatment equipment is very advantageous because it does not require special equipment and is inexpensive compared to other treatment methods.

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

pH 1 to 1 for aqueous wastewater containing dithiocarbamates.
Add an aqueous solution of potassium permanganate to 1.
Stir at 0-100°C.

After the decomposition due to oxidation is completed, stirring is stopped and a precipitate separates into the lower layer.

This is passed through the ocean and separated from the waste liquid. In adjusting the pH, examples of acids and alkalis for acidification include sulfuric acid, hydrochloric acid, nitric acid, and phosphoric acid.

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

Dithiocarbamates can be treated in a range from a very small amount to around 10%, but from an economical perspective, it is preferable to use up to about a few percent.

By changing the amount of potassium permanganate used and the treatment conditions depending on the content of dithiocarbamates, dithiocarbamates can be removed to a few ppm or less.

When the content of dithiocarbamate is large, it is preferable to adjust the pH to acidic and remove the precipitate as free dithiocarbamate before treatment, from the viewpoint of processing operation and economical efficiency.

Since the remaining potassium permanganate is extremely small if used in an appropriate amount, it can be diluted with treated water, or it can be decomposed using a reducing agent or the like.

The filtration residue can be incinerated and recovered as manganese oxides or manganese sulfate after further processing.

The composition of the substance precipitated by oxidation mainly contains manganese dioxide, manganese monoxide, etc.

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

Example 1 2.5 parts by weight of concentrated sulfuric acid was added dropwise to 1000 parts by weight of a waste liquid (waste liquid A) containing 14000 ppm of ethylene bisdithiocarbamate while stirring at 5 to 10°C, and the mixture was stirred for 10 minutes.

After the stirring was stopped, the treated product became a floc of 2 to 5 iua and was easily separated from the water.

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

Next, 0.5 parts by weight of a 30% potassium permanganate aqueous solution was added to the P solution, and stirring was continued for 10 minutes.

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 P solution by forming a tear film using a filter paper.

The p solution is designated as sample A-1.

The above waste liquid was treated with 2.5 parts by weight of concentrated sulfuric acid.
1.67 parts by weight of potassium permanganate aqueous solution and 16,
Samples treated in the same manner with 7 parts by weight were A-2 and A-2, respectively.
-3.

The final pH of the sample was 6.5 to 7.5.

The results were as shown in the test examples.

The recovery rate of manganese was 82% as manganese dioxide.

Example 2 0.5 parts by weight of concentrated sulfuric acid was added dropwise to 1000 parts by weight of a waste liquid (waste liquid B) containing 1-28 ppm of dimethyldithiocarbamate while stirring at 5 to 10°C.

After stirring for 10 minutes, the treated product became a floc of 2 to 5 ynm and was easily separated from water.

The precipitate was separated from the P solution by filtration using P paper.

Next, 0.33 parts by weight of 30% potassium permanganate solution was added to the P solution, and stirring was continued for 10 minutes.

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

The precipitate was lacrimated with P paper and separated from the filtrate.

The P solution is designated as sample B-1.

Example 3 To 1000 parts by weight of a waste liquid containing 28 ppm of dimethyldithiocarbamate was added 301% of the solution while stirring at 5 to 10°C.
% potassium permanganate aqueous solution was added and stirred for 10 minutes.

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

The precipitate was lacrimated with P paper and separated from the filtrate.

This filtrate is designated as sample B-2.

About the test example filtrate Alternaria ma')
The spore germination rate was measured using the PFT method (
Poison Food Technique).

The results are shown in the table below. Comparative Example Similarly to Example 1, 2.5 parts by weight of concentrated sulfuric acid was added dropwise to 1,000 parts by weight of the waste liquid (containing 14,000 ppm of ethylene bisdithiocarbamate) with stirring at 5 to 10°C, and the mixture was stirred for 10 minutes.

After the stirring was stopped, the flocs were separated from the water.

Next, 0.5 part of 30% hydrogen peroxide solution was added to the mixture and stirred for 30 minutes.

Separately, 0.5 part of a hypochlorite solution (containing 10% available chlorine, Shogaku Kagaku ■ reagent) was added, and the mixture was similarly stirred for 30 minutes.

Next, a biological test similar to the above test example was conducted.

As shown in the above test example, the dithiocarbamate in the untreated waste liquid is almost completely removed as shown in the treated waste liquid, and the bactericidal activity is also extremely low compared to the untreated waste liquid. show.

Claims (1)

[Claims] 1. A method for treating a waste liquid that removes dithiocarbamates from the waste liquid by treating the aqueous waste liquid containing dithiocarbamates with potassium permanganate at pH 1 to 11.