Cost-effective method for recovering precious metals in circuit board components

Patent metadata

Field	Value
Publication number	US-2023175096-A1
Application number	US-202217975606-A
Country	US
Kind code	A1
Filing date	Oct 28, 2022
Priority date	Dec 3, 2021
Publication date	Jun 8, 2023
Grant date	—

Abstract

The invention discloses a cost-effective method for recovering precious metals in circuit board components, and belongs to the area of waste resource recovery. The method mainly solves the problem of selective recovery of precious metals in chlorination leachate, utilizes the basic principle of oxidation-reduction reaction, adopts a mixed solution of sulfuric acid and hydrogen peroxide and a mixed solution of hydrochloric acid, sodium chloride and sodium chlorate, and also adopts ammonia water and formaldehyde to reduce silver. According to the characteristic that the redox potential of gold and palladium ions is higher, the gold and palladium ions in the chlorination leaching solution are selectively reduced into elements by using a reducing agent which is low in price and moderate in reducibility, then the elements are separated through filtration to realize resource recycling. The whole recycling process is greatly shortened, combined with the lower price of reducing agents, leading to the low cost of process. The method is commercially viable and is beneficial to industrialization. Meanwhile, a large amount of tail liquid is prevented from being generated to pollute the environment in the recycling process.

First claim

We claim:

1 . A cost-effective method for recovering precious metals in circuit board components, comprising the following steps:
(1) leaching: add metal powder after crushing and magnetic separation to a mixed solution of sulfuric acid and hydrogen peroxide, and react at 70-90° C. for 2-3 hours; a liquid-solid ratio between the metal powder and the mixed solution is 4:1-8:1; after filtration, filter residue is added with a mixed solution of hydrochloric acid, sodium chloride and sodium chlorate to react at 70-90° C. for 2-3 hours to obtain a metal chloride leaching solution, a liquid-solid ratio is 5:1-9:1; (2) precipitation: the metal chloride leaching solution of step (1) is cooled to room temperature and filtered to obtain solid silver chloride, wherein the solid silver chloride is added into ammonia water and formaldehyde to obtain silver element; a filtrate obtained by cooling the metal chloride leaching solution to room temperature and filtering is added to organic reduction reaction with reagents, keep temperature at 50-70° C. for 6-10 hours, filter out precipitation material, including gold, palladium and tin dioxide, after washed with hydrochloric acid, gold and palladium is obtained; (3) circulation: the filtrate obtained from the reaction of metal chloride leaching solution and organic reducing agent in step (2) is added to an extractant for extraction, an organic phase is separated from the extractant and the organic reducing agent by decompression distillation, and the organic reducing agent is reused in step (2); after extraction, add hydrochloric acid, sodium chlorate into water phase until a concentration of hydrochloric acid, sodium chlorate and sodium chloride equal to the mixed solution in step (1); the water phase after extraction and circulations is regarded as last tail liquor, sodium chloride is recovered from the tail gas by evaporative crystallization.

2 . The cost-effective method for recovering precious metals in circuit board components according to claim 1 , wherein in sulfuric acid and hydrogen peroxide mixed solution of step (1): concentration of sulfuric acid is 1.5 mol/L-3 mol/L, a mass percentage concentration of hydrogen peroxide is 20%-30%, and a volume ratio between sulfuric acid and hydrogen peroxide is 2:1-4:1.

3 . The cost-effective method for recovering precious metals in circuit board components is according to claim 1 , wherein in step (1), the concentration of hydrochloric acid in the mixed solution is 0.5-1.5 mol/L, the concentration of sodium chloride is 120-190 g/L, and the concentration of sodium chlorate is 6.82-20.46 g/L.

4 . The cost-effective method for recovering precious metals in circuit board components according to claim 1 , wherein the organic reducing agent in step (2) refers to one or more of amide organic compounds, such as
N,N-Dimethylformamide (DMF), N,N-dimethylacetamide (DMA).

5 . The cost-effective method for recovering precious metals in circuit board components according to claim 1 , wherein the extraction agent in step (3) refers to one or more of dichloromethane, chloroform and benzene.

Assignees

• Univ Beijing Technology

Inventors

• Yu Jiamei
• Guo Jiaqi

Classifications

• Y02P10/20

  Recycling · CPC title

• C22B7/007

  by acid leaching · CPC title

• C22B11/046 Primary

  from manufactured products, e.g. from printed circuit boards, from photographic films, paper or baths · CPC title

• C22B7/005 Primary

  Separation by a physical processing technique only, e.g. by mechanical breaking · CPC title