JP2008231388A - Detoxifying treatment agent for hexavalent chromium-containing specific waste - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a detoxifying treatment agent for easily and quickly reducing to nontoxic trivalent chromium, without affecting human health, hexavalent chromium existing in hexavalent chromium-containing specific wastes as targets for detoxifying treatment, i. e. crematory bone ashes, leathers and waste liquids resulted by tanning leathers with chromiun as a tanning material, wastes associated with refractory chromium bricks, wastes including chromeplating waste liquids, wooden buildings-derived scrap wood, and soil backfill material wastes. <P>SOLUTION: The detoxifying treatment agent for hexavalent chromium-containing specific wastes comprises a solution containing, as the main component(s), one or more compounds selected from ascorbic acid and its isomers and sodium salts, potassium salts and ammonium salts thereof. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

Detailed Description of the Invention

  The present invention is intended for the detoxification treatment of the present invention other than the chromium-containing iron ore that is generated by heat treatment such as melting, rolling, welding, fusing, etc. of chromium-containing alloy steel such as stainless steel, ferrochrome, and metal chromium. Specific waste containing hexavalent chromium, such as cremation skeleton bone ash, waste liquid and leather after leather tanning using chrome tanning materials, and incineration ash, refractory chrome bricks, etc. Waste such as plating waste and other waste containing hexavalent chromium, such as waste materials from wooden buildings and their incineration ash, or soil backfilling agent of the company, and product name ferrosilt, waste sulfuric acid containing hexavalent chromium Intentionally mixed and sold as a backfill, used as landfill, and as a result, hexavalent chromium leached out and caused serious environmental pollution. Identify the more contaminated waste according to detoxification treatment agent to be processed this.

Regarding the detoxification treatment of chromium-containing iron ore generated by heat treatment such as melting, rolling, welding, fusing, etc. of chromium-containing alloy steels such as stainless steel, ferrochrome, and metal chromium, the prior application of the present applicant. The name of a certain invention, a treatment method for chromium-containing iron ore (Patent No. 3687014), has been developed and proposed a method of detoxifying extremely effectively. It turned out that there was no method and the extremely hazardous waste was left as it was, creating a dangerous environment.
The above-mentioned danger of hexavalent chromium to the human body may affect the mucous membranes and skin, and may cause perforation of the nasal septum and tumors in the nose, lungs, throat, etc.
He discovered that bone ash, one of the above specified wastes, also contains hexavalent chromium, and when colored in accordance with the diphenylcarbazite method, the color of reddish purple is clearly recognized. . This is because the grate inside the cremation pot is made of stainless steel or chrome steel, and during the cremation, the kettle becomes hot, the chromium of the grate steel is oxidized and turned into slag, dropped off and mixed into bone ash Estimated.
Similarly, when the chromium complex salt solution was absorbed as a tanning agent in the leather tanning process designated as specific waste, it was confirmed by the above inspection method that hexavalent chromium was mixed in the leather waste.
Similarly, among the various refractory bricks, refractory bricks mainly made of chromite are estimated to oxidize the chromic material exposed to high temperatures during firing and produce hexavalent chromium. Its existence was confirmed.
Furthermore, the plating bath in the chromium plating method uses a chromic acid with a small amount of acid radicals, but part of the chromium content is transformed into hexavalent chromium due to electrolysis and is present in the waste liquid. It was confirmed by the above inspection method.
In addition, the type of chemical that seems to have been applied to the waste materials of wooden buildings is not clear, but the presence of hexavalent chromium was confirmed from the waste materials and their incinerated ash by the same inspection method. .
As a means of modifying these hexavalent chromium to harmless trivalent chromium, conventionally, ferrous sulfate or sodium sulfite was used as a reducing agent, hexavalent chromium was reduced to trivalent chromium, and further slaked lime, etc. A method is employed in which chromium hydroxide is precipitated by adding an alkali agent, and this is separated and removed. However, such a treatment method is extremely complicated and troublesome, and these reducing agents have a mild chemical reaction. In addition, there are drawbacks that require a long time for processing, and in the case of ferrous sulfate, there is a disadvantage that a large amount of iron ions eventually precipitate as ferric hydroxide, and in the case of sodium sulfite, Since the sulfurous acid gas is generated during the handling, there is a disadvantage that it is harmful to the human body.
Because of these drawbacks, the above-described conventional processing method is not widespread, and is unavoidably ignored.

Problems to be solved by the invention

  In contrast to the above situation, the present invention is to provide a detoxifying agent capable of rapidly reducing hexavalent chromium in the specified waste to harmless trivalent chromium by an unprecedented simple method.

Means to solve the problem

  In view of the above problems, the following are proposed as means for solving this problem. That is, a solution for detoxification of specified waste containing hexavalent chromium comprising a solution mainly composed of one or more of ascorbic acid and its isomers or sodium salts, potassium salts and ammonium salts thereof. The main point.

Whether to disperse this detoxifying agent consisting of a solution containing ascorbic acid and its isomers or derivatives thereof such as sodium salt, potassium salt, ammonium salt, etc., alone or in combination to each waste specified in the present invention. It has the effect of reducing the hexavalent chromium contained in each waste to harmless trivalent chromium by the powerful and fast reducing power of ascorbic acid and its derivatives by means such as immersion. In addition, ascorbic acid is acidic with respect to the alkalinity of hexavalent chromium contained in the waste by adding and blending a pH indicator that changes color due to a change in pH into the above solution, the color tone changes when the solution is used. Therefore, it is extremely effective in determining an appropriate amount of the solution to be used.
The solvent of the solution is preferably water, but is not limited to this. It does not prevent the use of other solvents such as alcohol, and a surfactant is used to help the solution to penetrate. It is more effective if glycerin or the like is blended in order to impart the.
In addition, when the concentration of the ascorbic acid aqueous solution was examined for its effectiveness, the reduction effect was moderate at 0.1% by weight or less, but the amount used was large and there was a problem in practicality, but 0.5% by weight. % Or more, a remarkable reduction effect is recognized at moderate usage, and if the concentration is higher than that, the amount of waste to be treated and the hexavalent content to be treated, such as a smaller amount, is sufficient. What is necessary is just to select suitably according to the amount of chromium.

When a small amount of bone ash, which is one of the specific wastes to be treated according to the present invention, was collected and a 0.25% diphenylcarbaditone acetone solution was added dropwise thereto, a reddish purple color was clearly observed. Obviously, the presence of hexavalent chromium was confirmed.
Therefore, a 5% by weight aqueous solution of ascorbic acid was sprayed on the same bone ash, and after standing for several minutes, when the acetone solution was dropped, no reddish purple color was observed, and the presence of hexavalent chromium was complete. It was estimated that it was reduced to harmless trivalent chromium.

Chromium complex solution is used as a tanning agent in many tanning agents for leather, but leather tanned using this tanning agent, incineration ash, and acetone solution of the above hexavalent chromium detection agent in its waste liquid As a result, reddish purple color was clearly observed, and the presence of hexavalent chromium was clearly confirmed.
Therefore, as in Example 1, the same leather and its waste liquid were sprayed with a 5% by weight aqueous solution of ascorbic acid and allowed to stand for several minutes, and then the acetone solution was dropped. First, the absence of hexavalent chromium was confirmed.

When refractory bricks, commonly called chromium bricks, containing chromite ore as the main raw material were pulverized and the acetone solution as the hexavalent chromium detector was dropped onto the powder, reddish purple color was confirmed. Obviously, the presence of hexavalent chromium was confirmed.
Therefore, as in Examples 1 and 2, after spraying an aqueous solution of ascorbic acid having the same concentration, the mixture was allowed to stand for a while and the acetone solution was dropped, and no reddish purple color indicating the presence of hexavalent chromium was observed. . That is, hexavalent chromium was reduced to trivalent chromium.

After using the lead to be plated as the cathode and the lead plate as the anode, and adding a small amount of acid radicals to the chromic acid as the plating bath, and subjecting the material to be plated to chrome plating, The waste water after the plating treatment was washed was collected and an acetone solution, which is a hexavalent chromium detection agent having the above composition, was dropped, and a reddish purple color was observed. From this phenomenon, the presence of hexavalent chromium was clearly confirmed in the waste water after the plating treatment.
Therefore, when an aqueous solution of ascorbic acid having the same concentration as in the above examples was dropped and stirred, and after standing for a while, the acetone solution was dropped and the reaction was observed. The presence of hexavalent chromium could not be confirmed at all.

Recently, waste materials from wooden buildings were collected, and as a precaution, the presence or absence of hexavalent chromium was analyzed by the same inspection means as described above. As a result, there was a color reaction indicating the presence of hexavalent chromium.
Therefore, ascorbic acid having the same concentration as that shown in the above example was sprayed on the subject, and after standing for a while, the acetone solution was dropped to observe the presence or absence of a color reaction, but no color reaction was observed. In addition, the presence of hexavalent chromium was not observed. Similar results have been obtained for the incineration ash of the waste.

Ferrosilt, a soil backfill material that has caused serious environmental pollution problems due to the outflow of hexavalent chromium, is manufactured from waste sulfuric acid generated during the manufacturing process of titanium oxide, but is estimated to contain hexavalent chromium. This is an incident caused by mixing the unnecessary waste acid solution into the product without detoxifying it, but the cause is not in the ferrosilt itself, and the problem lies in the unnecessary waste sulfuric acid solution mixed in illegally. Since it has been found that hexavalent chromium is already present in this waste sulfuric acid solution, it can be estimated without deliberate experimentation that the detoxification treatment can be accomplished by employing the treatment agent of the present invention. It is.
In addition, it is considered that it is needless to say that the detoxification treatment of industrial waste containing hexavalent chromium similar to this can be treated by applying the detoxification treatment agent of the present invention.

  Instead of ascorbic acid in the above examples, erythorbic acid or ascorbic acid, or each derivative of sodium salt, potassium salt, ammonium salt, etc. of erythorbic acid is used alone or in combination of two or more by the same method. When the reduction effect of chromium was tested, it was confirmed that substantially the same reduction effect could be obtained by appropriately increasing the concentration, although the reduction effect was slightly inferior to that of the same amount of ascorbic acid.

The invention's effect

  According to the hexavalent chromium detoxifying treatment agent of the present invention, it is possible to easily and quickly detoxify the waste containing the hexavalent chromium specified in the present invention safely and without fear of hindering human health. It has been made possible, and is extremely useful in the industry for preventing serious environmental pollution caused by the presence of hexavalent chromium.

Claims (1)

  A detoxifying agent for specific waste containing hexavalent chromium, comprising a solution containing ascorbic acid and isomers thereof, or a sodium salt, potassium salt or ammonium salt thereof as a main component or two or more thereof.