JPS5949291B2 - Method for recovering nickel and cadmium from waste nickel-cadmium storage batteries - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for recovering nickel and cadmium from waste nickel-cadmium storage batteries.

The main constituent materials of nickel-cadmium storage batteries are nickel and cadmium, and potassium hydroxide is used as the electrolyte, so throwing away waste batteries as they are may cause environmental pollution, and there are also concerns regarding resource recovery. It is also desired to recover valuable metals from

Conventional methods for recovering these metals from discarded cadmium storage batteries include disassembling the discarded battery, removing the cathode plate and anode plate, washing with water, roasting at 500 to 600°C, and then extracting cadmium with an aqueous ammonium nitrate solution. After that, cadmium is precipitated and separated as cadmium carbonate, and cadmium is recovered by a conventional method.
Nickel is separated and recovered from the extraction solution, nickel and cadmium mixed sludge from waste batteries is leached using zinc electrolysis waste solution, etc., and then filtered, and the R solution is replaced with zinc powder to create sponge cadmium, and nickel is leached out. Methods have been proposed to collect the waste as slag, but all of these methods involve complicated treatment processes and have many problems in terms of wastewater treatment.

The present invention overcomes the above-mentioned drawbacks and provides a method for recovering nickel and cadmium in a simple process and without any extraction process.

The inventor studied the structure of a nickel-cadmium storage battery, and found that cadmium is mainly impregnated and electrodeposited on the cathode plate in the form of cadmium salt, and that both the cathode plate and the anode plate are made of nickel or nickel alloy mesh with nickel fine powder. Since it is a sintered product, it can be heated at a temperature of 700 to 1,600°C in a non-oxidizing atmosphere after providing an opening by making a hole or cutting a hole in the outer shell case of the storage battery. The electrolytic solution consisting of an aqueous potassium hydroxide solution evaporates, and the cadmium salt becomes cadmium oxide.Due to the difference in affinity between cadmium and nickel for oxygen, nickel acts as a reducing agent, and the cadmium is reduced and volatilized. The present invention was developed based on the fact that if the contained gas is introduced into a condenser and cooled, metallic cadmium is recovered and nickel remains as a residue.

The purpose of making openings in the outer shell of the storage battery before heating is to facilitate the volatilization of the electrolyte and cadmium during heating, and it is preferable to make many holes in the outer shell or make cuts in multiple places. .

When processing electrode plate layers and the like generated during the battery manufacturing process, there is no need for openings because the outer shell is not configured as a battery.

The lower limit of the heat treatment temperature was set at 700°C because the reduction and volatilization of cadmium would not be sufficient at lower temperatures, and the upper limit was set at 1,600'C because at higher temperatures the heat treatment equipment would be damaged. Undesirable.

Regarding the atmosphere during heat treatment, a non-oxidizing atmosphere is sufficient as nickel in the material acts as a reducing agent and reduces cadmium, and there is no need to add a solid reducing agent such as carbonaceous material. If a reducing agent is added to create a reducing atmosphere, the processing time can be shortened.

Examples will be described below.

Example 1 20 nickel-cadmium waste batteries (each weighing 1460 P) were compressed using a hydraulic press, the outer shell of the battery was opened, the battery was charged into a test furnace, and the battery was heated at 900°C for 2 hours while flowing CO2 gas at 14/min.
After heating for several hours, metal cadmium was recovered in a condenser attached to the furnace.

When the recovered metal cadmium was analyzed, it was found that Ni, Fe
, C1l were all 0.001% or less, and Zn and Pb were each 0.005% or less (all by weight), and cadmium with good purity could be recovered.

In addition, the analysis value of the metal lump obtained by removing the residue after the heat treatment and heating and melting it was Ni49, 7%Fe48.7
%, CdO, 01% (both Tsume Denga), Cd could be sufficiently separated.

Example 2 A mixture 201 of negative and positive plate scraps generated in the manufacturing process of a nickel-cadmium storage battery was placed in an alumina boat, and CO2 gas was passed through it at a rate of 0.5 t/min in a quartz reaction tube.
The mixture was heated at 000 to 900° C. for 60 minutes to volatilize the cadmium.

When the heating residue was analyzed and the cadmium volatilization rate was determined, it was 94% at 700°C and 98% at 800°C and 900°C.
It was above the level of staff.

Example 3 The materials of Example 2 were co:co in a quartz reaction tube.

A mixed gas having a ratio of 2N2 of 1:1:4 was flowed at a rate of 0.6-7/min and heated at 800°C and 900°C to examine the relationship between heating time and volatility rate.

As a result, it was found that it takes 30 minutes at 800° C. and 20 minutes at 900° C. for the volatilization rate of cadmium to reach a factor of 95 or higher.

Example 4 Brown coal powder was added to a mixture 201 of negative and positive plate scraps generated in the manufacturing process of a nickel-cadmium storage battery at a ratio of 5 to 50% of the electrode plate scraps.
25% by weight was added and mixed, placed in an alumina boat, and mixed with 0.2 and N2 at a ratio of 1:10 in a quartz reaction tube.
55. ! /min (flowed with a calyx pick-up, heated at 800°C for 1 hour, and measured the volatilization rate of cadmium.

As a result, the volatility was 92% when the lignite mixture ratio was 5, and 9 when it was 10%.
At 5% and 15% or higher, scores of 99 or higher were obtained.

As mentioned above, from Example 1.2, the atmosphere for heating is as follows:
Most of the cadmium contained in J■u raw material can be recovered as metallic cadmium without converting it to Anewa Oki Oki 14 core raw material.

In addition, the recovered metal cadmium has a high purity, and nickel can be recovered from the heat-treated residue, making it possible to effectively and easily process nickel-cadmium waste batteries and reuse the resource. It is.

Claims (1)

[Claims] 1 Waste nickel cadmium, characterized in that at least a part of the outer shell of a waste nickel cadmium storage battery is opened and heat treated at a temperature of 700 to 1,600°C in a non-oxidizing atmosphere to volatilize and collect cadmium. How to recover nickel and cadmium from storage batteries.