KR940010114B1 - Method for the preparation iron oxide microparticles - Google Patents

Abstract

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Description

Heat-resistant dark brown synthetic iron oxide fine particle manufacturing method

The present invention relates to a method for producing heat-resistant dark brown synthetic iron oxide fine particles by synthesizing pickling waste liquid and chromium plating waste of steel. In the steel industry, it is necessary to remove iron oxide from the steel surface before machining steel for the purpose of improving the properties of the product. The pickling treatment method is widely used. It causes pollution of groundwater or seawater.

Fe-oxide + … … … … … … … … … … … … … (One)

Fe-oxide + … … … … … … … … … … … … … (2)

During the pickling process of steel, it reacts mainly in the formula (1) and very small amount reacts in the formula (2). Moreover, since the acid is required in order to accelerate the reaction in the forward direction and improve the pickling rate, in general, 8 to 10% of the excess acid remains and waste liquid is generated. On the other hand, hexavalent chromium is used in acid solution in the industry where chromium plating is applied to steel surface to extend the life of steel. However, the plating component Fe and the like are easily dissolved and mixed in the chromium plating solution during the plating process, and the plating performance becomes difficult when the amount of the mixture is more than a predetermined value.

In this process, a plating waste liquid in which hexavalent chromium and Fe, which is a component to be plated, are dissolved, is generated. Since hexavalent chromium is extremely dangerous in this plating waste, chromium was reduced from hexavalent to trivalent by reducing agents such as sulfurous acid gas and sodium sulfite in aqueous solution as shown in the following formulas (3), (4) and (5). Next, by reacting with alkali such as NaOH, Ca (OH) ₂ and the like, chromium is precipitated and separated into Fe (OH) ₂ with chromium hydroxide of Cr (OH) ₃ to generate waste of sludge.

H ₂ Cr ₂ O ₇ +3 Na ₂ SO ₃ + 3H ₂ SO ₄ ... … … Cr ₂ (SO ₄ ) ₃ +3 Na ₂ SO ₄ + 4H ₂ O... … (3)

Cr ₂ (SO ₄ ) ₃ +6 NaOH. … … … … … … 2Cr (OH) ₃ + 3Na ₂ SO ₄ ... … … … … (4)

Fe (SO ₄ ) + 2 NaOH... … … … … … … … Fe (OH) ₂ + Na ₂ SO ₄ ... … … … … … (5)

This waste is generated by containing 2-6% of Cr, 1-3% of Fe and 80-92% of water as in the formulas (3), (4) and (5). Thus, pickling liquor and chromium plating waste of steel produced as in the following formulas (1), (2), (3), (4) and (5) mainly cause heavy metal pollution.

The present invention relates to a method for producing heavy added heat-resistant dark brown synthetic iron oxide fine particles by preventing heavy metal pollution caused by pickling waste liquid and chromium plating waste of steel as described above and by synthetically processing these wastes. The pickling liquor of steel consists mainly of divalent Fe ions and very few trivalent Fe ions, while the chromium plating waste consists mainly of Cr (OH) ₃ and some Fe (OH) ₂ . After being stirred mixture so that the two waste as it mixed with 12-25% of the Cr / Fe ratio by weight component ratio KOH, NaOH and _{Ca (OH) 2, NH 4} OH , such as alkali (OH ^-) in a pH 7 by addition of a solution Set to -8 to sediment and separate heavy metals from the two wastes. The precipitate is heated, burned, and dried in the air at a low temperature of 20-90 ° C. to obtain ultrafine heat resistant dark brown synthetic iron oxide fine particles. The microparticles | fine-particles obtained as mentioned above have heat resistance which does not discolor black-brown to 1,000 degreeC, and has the reflectance of 11.0-12.5% at the wavelength of 680-700 nm of black-brown. The particle size is in the range of 0.08-0.30 µm.

When mixing the two wastes, brown of the final precipitate having a Cr / Fe ratio of 12% or less decays and becomes red, and 25% or more of brown decays and green. After mixing the two wastes, Fe and Cr are dissolved at a pH below 7 and Cr is easily dissolved at a pH above 8, which may cause pollution problems of water pollution.

The present invention is made of a high value-added heat-resistant dark brown synthetic iron oxide fine particles by mixing and processing steel pickling waste liquid and chromium-plated waste sludge, which not only enhances waste treatment of waste generating companies but also relies on imports from foreign countries. Localization of the fine particles not only can reduce foreign currency, but it is also a very useful invention that can fundamentally solve the pollution problem of heavy metal pollution among the problems of environmental preservation in Korea.

EXAMPLE

In mixing the pickling liquid of the steel and the chromium plating waste sludge, the mixing ratio of Cr / Fe is mixed to 18% by weight, followed by stirring with alkaline (OH ⁻ ) solutions such as KOH, NaOH, Ca (OH) ₂ , and NH ₄ OH. By adding to pH 7 to precipitate and separate heavy metals from these wastes. The precipitate is heated and burned in air at 200 ° C. to obtain heat-resistant dark brown synthetic iron oxide fine particles.

These fine particles have heat resistance that black brown does not discolor until 1,000 ° C., and has a reflectance of 11.0-12.5% at a wavelength of 700 nm of black brown.

Particle size of 0.08-0.30 µm is obtained. Meanwhile, the residual heavy metal component in the supernatant produced was purified as shown in Table 1, and no other metal components were detected. This result is excellent in purifying water quality to a value much lower than the current environmental conservation allowances indicated in Table 1 below. Therefore, the effluent produced by the present method has no problem of environmental conservation.

Table 1 Residual Heavy Metal Content in Supernatant (ppm)

Permissible value under the Water Quality Preservation Act

Claims (1)

When mixing pickling waste liquid generated during processing of steel and waste waste generated during chromium plating, the mixing ratio of Cr / Fe is adjusted to 12-25% by weight ratio and stirred and mixed, followed by KOH, NaOH and Ca (OH) ₂ , NH ₄ OH, etc. of alkali (OH ^-) solution was added to adjust to PH 7-8 by separating the precipitated heavy metal components and then to the precipitate in air heated to a temperature of 20-90 ℃, burning and drying of the polar fine heat resistance hameuroseo And black brown, a method for producing heat-resistant dark brown synthetic iron oxide fine particles having a particle size of 0.08-0.30 μm that does not discolor even at 1,000 ° C. having a reflectance of 11.0-12.5% at a wavelength of 700 nm.