JPS6019092A - Treatment of waste liquid - Google Patents

Abstract

PURPOSE:To remove a metalloid or a noxious anion, by a method wherein alkali is added to a heavy metal-containing waste liquid having a ferrous salt added thereto to adjust the pH thereof to 8-12 and a soluble alkaline earth metal salt is further added to said waste liquid before a ferrous ion is oxidized. CONSTITUTION:A ferrous salt is added to a heavy metal-containing waste liquid and alkali is added thereto to adjust the pH thereof to 8-12. After a soluble alkaline earth metal salt is added, the treated waste liquid is brought into contacted with oxigen-containing gas or receives the addition of an oxidizing agent to oxidize a part of a ferrous ion and a spinnel ferrite precipitate is formed. After a heavy metal ion is taken in the aforementioned precipitated particle or adsorbed therewith, solid-liquid separation is performed. As the aforementioned soluble alkaline earth metal salt, there are halides represented by calcium chloride, strontium chloride or barium chloride or nitrate.

Description

[Detailed description of the invention] The present invention is directed to a method for treating waste liquid containing heavy metals.

Conventionally, single heavy metal-containing waste liquids have generally been treated by a neutralization coagulation-sedimentation method. The medium oro flocculation method is a method that
This is a treatment method in which H is adjusted to convert heavy metals into insoluble hydroxides or oxide precipitates, followed by solid-liquid separation. Although this method is easy to operate, it has the disadvantage that it cannot efficiently remove all the various types of heavy metals that coexist in one treatment because the optimum pH range for precipitation varies depending on the type of heavy metal. In addition, when the generated sludge is assimilated and dumped, it has the disadvantage that there is a great concern that it will be re-leached. On the other hand, some of the ferrous ions are removed by adding ferrous salt to the heavy metal waste liquid, adding an alkali to maintain the pH between 8 and 12, and contacting it with oxygen-containing gas or adding an oxidizing agent. A recently developed treatment method involves oxidizing spinel-type ferrite precipitates to form spinel-type ferrite precipitates, incorporating or adsorbing heavy metal ions into these precipitated particles, and then separating the solid-liquid. It has many advantages such as the ability to process, produce stable sludge, and perform drowsy solid-liquid separation, and is called the %7E2ite method.

However, this ferrite method is basically suitable for removing heavy metal ions that tend to form cations, but is not suitable for removing some metalloids that easily form anions or some harmful anions. There is a drawback that there is no

The present invention eliminates the above-mentioned drawbacks and provides a method for treating waste liquid that can remove some metalloids that tend to form anions and some harmful anions even if they contain heavy metals. .

The present invention adds ferrous salt to waste liquid containing heavy metals,
Add alkali to maintain pHff1'8 to 12, and oxidize some of the ferrous ions by contacting with oxygen-containing gas or adding an oxidizing agent to generate spinel-type ferrite precipitates and remove heavy metal ions. In the method for treating waste liquid, which involves solid-liquid separation after being incorporated or adsorbed into the precipitated particles, a soluble alkaline earth metal salt may be added to the waste liquid before oxidizing the ferrous ions. Features.

In this invention, typical ferrous salts used are:
ferrous chloride, ferrous sulfate and mixtures thereof.

A typical alkali is caustic soda, which is most commonly used, but milk of lime can also be used. If the waste liquid is originally strongly alkaline and its pH exceeds 12 even when all the ferrous salt is added, it is necessary to add an acid in advance. The invention can thus also be applied to alkaline waste liquids. The reason why the adjusted pH was limited to 8 or more and 12 or less was because p
If H is lower than 8, it is not only difficult to obtain ferrite precipitation in spinel pear by oxidation, but also the time required for oxidation is longer. This is because although a light precipitate is formed, a different phase is likely to be formed. Oxidation conditions should be optimally determined depending on the amount and concentration of waste liquid. In general, heating and air oxidation are appropriate for a small amount of high concentration waste liquid, while oxidation at room temperature is considered to be economical for a large amount of low concentration waste liquid. Also, certain oxidation salts such as hypochlorites, chromates, nitrates, etc. can be used. When oxidizing at room temperature using these oxidizing agents, the particles of the 7-elite precipitate produced are generally fine, so it is necessary to select oxidation conditions depending on the case. 7 in the generated precipitate
Since ELITE is a ferromagnetic material, it can be separated all at once, and of course, solid-liquid separation can be easily performed by methods such as sedimentation separation and vacuum P@. The most important requirement is to add a soluble alkaline earth metal salt during these treatment steps. Soluble alkaline earth metal salts include halides such as calcium chloride, strontecium chloride, barium chloride, nitrates, etc. Calcium sulfate, which has a relatively high solubility, may also be used in some cases.

According to the method of the present invention described above, metals and semimetals such as selenium, tellurium, tungsten, and molybdenum, which have been insufficiently treated by conventional methods, can be removed at the same time. These metals and metalloids are not currently included in the urinary standards based on the Water Pollution Control Act, but they are equivalent to metals that are being considered as subject to future regulations. It is clear that the effectiveness of the present invention is not only present but will become increasingly important in the near future. This method also makes it possible to remove fluorine and phosphoric acid.

Next, embodiments of the present invention will be described.

[Example 1] Contains copper, hexavalent chromium, and zinc at a concentration of approximately 100 m9/13, and tungsten, tellurium, and molybdenum each at a concentration of 1/13.
Heavy metal waste liquid Il containing a concentration of OO da/l! After adding 0.1 mole of ferrous chloride, 2 g of barium chloride was added, and 10N caustic soda was added to adjust the pH to 10.
The temperature was maintained at 65°C, and air was blown at 21 °C per minute to form a 7-elite precipitate. Analysis of the p-liquid revealed copper and gold chromium.

Zinc is 0.03 m9/J or less, and tungsten.

The concentrations of tellurium and molybdenum are each 0.4 ta/l.
Less than > 4 my/i', less than 2 m9/If. still.

The water quality of the treated p-liquid without the addition of barium chloride was 0.03/e or less for copper, gold chromium, and zinc, but the concentration of tungsten, tellurium, and molybten was 7.
It was 0-80m971. When compared with the residual amount when barium chloride was added, which was 0.4'm9/l, it can be seen how great the effect of barium chloride addition is.

[Example 2] Manganese, cadmium, nickel''ff: 200m97
1. Add ferrous chloride to waste liquid 11 containing fluorine and phosphate ions at 50 μ/l each and molybdenum at 2007nfI//.
Add 0.2 mol of k and adjust the pH to 10 by adding caustic soda.
The liquid was oxidized by contacting the liquid surface with air, and after about 10 hours, 2 g of calcium chloride was added, and a permanent magnet was used to remove the precipitate along with the seven-grade light particles that had already formed. Analysis of the separated water that was removed revealed that manganese, cadmium, and nickel were less than 0,051n9/l, 7 elements was 0.5 ■/l, phosphoric acid was about 0.1 da/l, and molybdenum was less than 4Tn9/It. Ta. For comparison, a waste liquid having the same composition as above was subjected to the same treatment as above except that calcium chloride was not added, and approximately lsom// molybdenum remained in the separated water after treatment. Remaining amount when adding 1 liter of calcium chloride 4m9/1
When compared with 3, you can see how effective calcium chloride is.

As explained in detail above, the present invention relates to tellurium.

This method has the effect of effectively removing metals such as molybdenum and metals from waste liquids that have been difficult to remove in the past.

Procedural amendment (voluntary) 5! J, 'ICI, -, 4 Mr. 3, Commissioner of the Japan Patent Office, 1935, 3, Relationship with the case of the person making the amendment Applicant: No. 33-1 (423) Shiba 5-chome, Minato-ku, Tokyo Representative of NEC Corporation Person: Tadahiro Sekimoto 4, Agent: Sumitomo Mikuchi, 37-8 Shiba 5-chome, Minato-ku, Tokyo 108]
Building Kuchimoto Electric Co., Ltd. (6591) Patent Attorney Uchihara 5, Detailed explanation of the invention column 6 of the specification subject to amendment, page 5, line 6 of the specification of the contents of the amendment, 1. This is corrected as ``vacuum p excess''.

Representative Patent Attorney Extension - Everyone.

1.

1 ton/ 11-1

Claims (1)

[Claims] Ferrous salts are added to waste liquid containing heavy metals, alkali is added to maintain the pH between 8 and 12, and ferrous ions are produced by contacting with oxygen-containing gas or adding an oxidizing agent. In a waste liquid treatment method, a part of the soluble alkaline earth metal salt is oxidized to form a spinel-type ferrite precipitate, heavy metal ions are incorporated or adsorbed into the precipitated particles, and then solid-liquid separation is performed. A method for treating a waste liquid, which comprises adding iron ions to the waste liquid before oxidizing iron ions.