SU1435539A1 - Method of producing zinc oxide - Google Patents

Abstract

The invention relates to paints and rubber areas of industry and allows to obtain zinc oxide with a high degree of whiteness and a low amount of water-soluble impurities. The method is carried out. pre-drying the waste of sodium hydrosulfite production before oxidative roasting to a moisture content of 0.15-0.30% and mixing them with sodium carbonate in an amount of 5-7 wt.% of the amount of dried waste. 1 tab.

Description

cl

4; i. with joint venture

CO with

11435539

The invention relates to the production of zinc oxide, used, for example, in the paint or rubber industry as a filler.

As a source of raw materials in the proposed method using waste production of sodium hydrosulfite, which contains g} zinc oxide

iZnCOH) contaminated with powdered zinc — JQ complies with the requirements imposed on pigments, zinc salts, and related substances (lead, cadmium) of the sulfide, sulfite, thiosulfate, and sulfate series.

The aim of the invention is to reduce the content of water-soluble impurities in zinc oxide and increase its whiteness.

In the proposed method of producing zinc oxide, which includes oxidizing roasting of zinc-containing wastes, washing and drying, before oxidative roasting, drying is carried out to a moisture content of 0.15-0.3%, the dried waste is mixed from 5-7 May, 7c : sodium carbonate (on the amount of dry waste).

The transfer of waste to a moisture content of 0.15-0.30% is caused by the need to evenly distribute the addition of sodium carotenate throughout the waste. If the moisture in the waste contains more than 3.30%, it becomes very difficult to evenly distribute carbo: - sodium, which reduces the efficiency of oxidative roasting and degrades the quality of zinc oxide. Achieving a lower moisture content (0, i5%) does not allow the process equipment. I The addition of sodium carbonate to the produced waste leads to a more complete conversion of sulfur to the highest degree of Oxidation, which contributes to an increase in the whiteness of the target product, oxide zinc and a decrease in its water-soluble impurities.

Example 1.80 g dried in a vacuum dryer to a moisture content and 0.3% sodium hydrosulfite production waste, having the following composition,%:

Zinc oxide

General content

sulfur

Water soluble

impurities

Lead, cadmium

mixed with 4 g of sodium carbonate

(5 wt.%) And calcined for 2 i in

muffle furnace at 800 C. After that

the cooled zinc oxide is washed by repulping with hot water (80 ° C) at the ratio W: T 5: 1 for 40 minutes, filtered and dried at 120 ° C. 70.3 g of zinc oxide are obtained.

The obtained zinc oxide has a whiteness of 91 srv.ed., the content of water-soluble substances is 0.21% and is satisfactory

0 5

Q

five

0

0

five

mentally zinc oxide in relation to OST-6-10-449-83 (nd grade).

Example 2. The method is carried out as in Example 1, but the waste is dried to a moisture content of 0.15% and 7 wt.% Is added.

The whiteness of the treated zinc oxide is 91 conventional units, the content of water-soluble substances is 0.20%.

Example 3. The method is carried out analogously to Example 1, but the waste is dried to a moisture content of 0.22% and 3% by weight of Na is added. At the same time, deterioration of whiteness (89 used units) and the content of water-soluble substances in the obtained oxide are observed. zinc (0.30%).

Example 4. The process is carried out analogously to example 1, but the waste is dried to a moisture content of 0.15% and 10% by weight is added. In this case, there is also a deterioration in the content of water-soluble impurities (0.37%) and whiteness (90 conventional units),.

Example 5. 50 g of dried up to a moisture content of 0.20% waste without the addition of sodium carbonate is immediately burned, then washed by repulping with hot water (80 ° C) with a ratio G:. T 5: 1 for 40 minutes and dried at 120 ° C 42.7 g of zinc oxide are obtained. The whiteness of the product obtained turned out to be unsatisfactory with a satisfactory (87 used units), and, moreover, a high content of water-soluble substances — 0.50%.

Example 6. The steps were carried out analogously to example 1, but the waste was dried to a moisture content of 1% and 5% by weight added. At the same time, there is a deterioration in the indices of zinc oxide whiteness (89 conventional units) and the content of water-soluble impurities (0.30%).

Example 7 The preparation of zinc oxide was carried out in a manner known per se. In this case, take the same waste, the temperature of oxidative roasting

800 ° C, its duration is 2 hours. Washing and drying conditions. product similar to those described in the known method.

Comparative data on the qualitative parameters of the zinc oxides obtained in examples 1-7 are tabulated.

From the data in the table it can be seen that when the sodium carbonate content (examples 3,4) and the moisture content of the waste after pre-drying (examples 6) are exceeded, there is a deterioration in the whiteness and water-soluble substances. As follows from Example 5, merely pre-drying the waste without mixing it with sodium carbonate also does not achieve the purpose of the invention. The same is observed if only mixing with sodium carbonate is performed without pre-drying (example 6). From Example 6, it can be seen that even at a moisture content of 1% of pre-dried waste, there is no deterioration in the whiteness and water-soluble matter content.

White, used 86

91

97.6

98.8

The content of substances soluble in water,% 0.57 0.21 0.20 0.30. 0.37 0.50 0.30

The content in the wash water, mg / l, 47.4 44.8 45.4 46.7 - 47.8 0.43 47.6

Compiled by O. Zobnin Editor N. Gunko Tehred M. Khodanych Corrector V. But ha

Order 5604/19 Circulation 446 Subscription

VNIIPI USSR State Committee

for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab. 4/5

Thus, when drying the waste to a moisture content of 0.15-0.30% and adding 5 to 7 wt.% Sodium carbonate to the dried waste (examples I and 2), the whiteness is improved and the content of water-soluble impurities decreases to the values determined by OCT- 6-0-449-83, compared with the known method. In addition, the proposed method, in comparison with the known, allows to slightly increase the content of the basic substance in the obtained zinc oxide and reduce the loss of zinc with the wash water.

Claims (1)

Invention Formula The method of producing zinc oxide from sodium hydrosulfite production wastes by their oxidative roasting, washing and drying, characterized in that, in order to reduce the content of water-soluble impurities in the product and increase its whiteness, before oxidative roasting, the waste is dried to a moisture content of 0.15-0, 30% and mix them with 5-7% sodium carbonate on the amount of dried waste. 89 90 87 89 98.8 98.2 97.7 98.7