JPS59170225A - Treatment of dust - Google Patents

Abstract

PURPOSE:To separate and recover Fe, Zn, Pb and Ag at a high yield by subjecting iron and steel dust contg. Zn, Pb, Ag, etc. to a leaching treatment using sulfuric acid, a wet magnetic sepn. treatment, an alkali treatment and a chlorination treatment. CONSTITUTION:Dust contg. 15-40% Zn, 10-30% Fe, 1-6% Pb, 4-15% Cl, 0.1-0.5% F, 0.005-0.030% Ag, etc. is first treated with a sulfuric acid soln. of 2-4pH to leach 50-70% of the Zn contained therein. The dust is again treated with the sulfuric acid of 10-300g/l concn. to leach the remaining Zn of a zinc ferrite type in the 2nd stage. The Cl and F in the dust are leached away by >=(90-95%) by such operation. The residue of the leaching is then subjected to a wet magnetic sepn. to separate away the Fe-component contained therein and thereafter the remaining nonmagnetic material is treated with an alkali to leach and recover Pb. The residue is treated with CaCl2 and the Ag contained therein is recovered in the form of AgCl.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for treating dust. In particular, it relates to a method for treating dust that simultaneously contains iron and other valuable metals, such as steel dust.

Conventionally, dust containing a large amount of iron has often been treated using a dry method.

However, due to the rise in the unit price of electricity and the cost of reducing agents such as coke, a wet process is becoming desirable.

In addition, particularly when the dust has a zinc quality of 20% or less, it is often impossible to perform industrially desirable treatment by the above-mentioned dry method.

Furthermore, in order to efficiently recover the target metals to be recovered, such as zinc, lead, silver, etc., a wet processing method that can sufficiently increase the concentration of the target metals to be recovered has been desired.

The present invention answers such a need.

In this method, zinc is leached from the dust using a sulfuric acid solution, and then the leaching residue is subjected to wet magnetic separation treatment to recover silver, lead, etc.

In one embodiment of the present invention, there is a method of recovering lead by adding an alkaline agent to the non-magnetic material after the magnetic separation treatment.

In yet another embodiment, chlorine and/or chloride is added to the leaching residue after addition of the alkali agent.

There is a way to recover trace amounts of silver.

The present invention will be described in detail below.

The components of the dust to be treated in the present invention are as follows, for example. Namely.

Zinc 15 to 40 inches, iron 10 to 30 inches, lead 1 to 6 inches, chlorine 4 to 15 inches, fluorine 0.1 to 0.5 inches, silver 0.005 to
It is composed of o, osos, and other substances.

In particular, if the dust contains a large amount of zinc that is not in the form of acid-insoluble diinkzerite, etc., and the lead content is low, the process can be carried out efficiently.

The dust is first leached with a sulfuric acid solution. In the leaching, zinc, chlorine, fluorine, etc. are leached out. In particular, in order to prevent leaching of iron, it is preferable to carry out two-stage leaching.

That is, in the first stage of leaching, around 50 to 70 liters of zinc was leached out at pH = 2 to pH-4, and in the second stage, the residue was leached at a sulfuric acid concentration of 100 to 300 t/l, and a small amount of zinc was leached out. It also leaches out zinc in the form of diinkzerite, which can also be present.

The second-stage leaching liquid is used as an acid regulator in the first-stage leaching process in order to prevent the iron in the diinczerite from being mixed into the treatment liquid in the subsequent process.

By the above treatment, zinc can be leached out extremely efficiently. For example, leaching of 80 to 96 inches is possible. Also, chlorine is over 95, and fluorine? The upper part of the θ relation can be leached out. Zinc in the leachate can be converted into electrolytic zinc through electrolytic treatment, or can be efficiently recovered as zinc carbonate by adding soda carbonate.

Chlorine, fluorine, etc. in the leachate are treated with an alkaline agent such as caustic soda, sodium chloride, sodium fluoride, etc.

On the other hand, iron content is efficiently removed from the leaching residue through wet magnetic separation treatment, and lead and silver are recovered in non-magnetic materials.

In this case, magnetic separation is performed with a magnetic force of 500 to 2000 Gauss. Most of the silver and lead are recovered in the non-magnetic material through the magnetic separation process. The amount of non-magnetic minerals to be processed at the same time is 6
As a result, the amount of alkaline agents or chlorides used in post-treatment steps can be reduced.

In addition, if enough zinc is leached into the magnetic material to concentrate the iron content, it can be used as a raw material for iron.

For non-magnetic materials, an alkaline agent is used to effectively leach and recover the lead contained therein. The amount of alkaline agent varies depending on the amount of residual zinc and lead content, but it is usually 30 to 70 f/1.
This is done using a leachate added to a L concentration. Due to the magnetic separation process, the amount of alkaline chemicals to be treated can be reduced because the amount of ore handled has been reduced, but a way to further reduce the amount is to wash the residue with water in advance to remove the sulfuric acid content. be.

Furthermore, in order to efficiently recover silver in the leaching residue after treatment with an alkaline agent, chlorine and/or chloride is added to effectively recover silver chloride.

More than 98 silver can be recovered.

As a chlorinating agent, for example, 1 to 10 parts of calcium chloride is added. The residue after the addition is chlorinated at a temperature of 900 to 1000° C. in a neutral or oxidizing atmosphere to recover silver chloride.

By implementing the present invention as described above, the following effects can be obtained.

(1) Dust containing valuable metals such as zinc, silver, and lead can be efficiently treated by wet processing.

(2) In particular, this is a preferred method with extremely low energy consumption when processing dust with a low zinc content of around 20 or so, and a low lead content.

(3) Furthermore, in the method of leaching and recovering lead using an alkaline agent, the present invention, which involves wet magnetic separation treatment in advance, is an effective method because it can reduce the amount of processed ore.

(4) Wet magnetic separation treatment can effectively concentrate lead and silver in non-magnetic materials.

(5) In addition, chlorine or fluorine, which are undesirable in terms of handling, can be removed in advance in the acid leaching step, which is the first step, and this is a preferred method.

Example steel dust (zinc 20.0%, iron 26.5%, lead 2.5%)
Ch, silver 0.011%, chlorine a2, fluorine 0.30%
) 100 K9 using 1 m' of sulfuric acid acid solution.

Acid leaching was performed for 1 hour while maintaining the pH of the solution at 2. As a result, 80% zinc, 99% chlorine, and 95% fluorine were leached.

The leachate was then filtered to obtain 9 out of 50 leach residues. 100% of lead and silver were recovered in the leaching residue.

After washing the leaching residue with water, it was treated by wet magnetic separation. Magnetic selection was carried out at 1100 Gauss using a magnetic material of 18F4. 32 kg of non-magnetic material was obtained.

In the magnetic material, iron was recovered at a high concentration of 60'lr. It could be used as a raw material for iron wire.

On the other hand, the non-magnetic materials contained lead and silver with a coefficient of 90 or more. The non-magnetic material was leached for 1 hour at room temperature with a solution of caustic soda having a concentration of 501/1. More than 75% of lead was leached out, and almost 100% of silver remained in the leaching residue.

In order to recover the silver in the alkali leaching residue, calcium chloride was mixed with α7' and roasted in an oxidizing atmosphere at a temperature of 1000° C. in a rotary kiln.

Through this treatment, 92% of silver 2 could be recovered as silver chloride.

Patent applicant: Japan Mining Co., Ltd. Agent: Patent attorney (7569) Keishi Namikawa

Claims (3)

[Claims] (1) A method for treating dust, which comprises leaching the dust with a sulfuric acid solution, and collecting the silver by subjecting the leaching residue to a wet magnetic separation process. (2) The method according to claim 1, in which lead is recovered by adding an alkaline agent to a non-magnetic material. (3) The method according to claim 2, in which a trace amount of silver is recovered by adding chlorine and/or chloride to the leaching residue after addition of an alkali agent.