Method for extracting and recovering gold from aqueous solution

Patent metadata

Field	Value
Publication number	US-12577635-B2
Application number	US-202218022571-A
Country	US
Kind code	B2
Filing date	Oct 31, 2022
Priority date	Jun 28, 2022
Publication date	Mar 17, 2026
Grant date	Mar 17, 2026

Abstract

The present disclosure provides a method for extracting and recovering gold from an aqueous solution, the method including: (1) gold extraction from an aqueous solution through electrocoagulation, in which an electrocoagulation reaction is performed in an electrolytic cell to produce iron hydroxide in-situ, so as to capture gold in the aqueous solution and reduces the gold into gold nanoparticles in-situ; (2) pickling and liquefaction of the precipitated iron sludge, in which the obtained precipitate is dissolved in nitric acid to dissolve iron flocs after washing treatment; and (3) separation and recovery of gold through a nanofiltration membrane system, in which the resulting solution after pickling the precipitated iron sludge is subjected to cut-off treatment using a nanofiltration membrane to separate nano-sized elemental gold from the solution, and then the resultant is washed with water to obtain elemental gold.

First claim

What is claimed is:

1 . A method for extracting and recovering gold from an aqueous solution, the method comprising:
(1) gold extraction from an aqueous solution through electrocoagulation, comprising:
extracting gold from an aqueous solution through electrocoagulation using a sodium salt as an electrolyte under a direct-current stabilized voltage supply in an electrolytic cell;
(2) pickling and liquefaction of a precipitated iron sludge, comprising:
dissolving a resulting precipitate in nitric acid under ultrasonication treatment; and
(3) separation and recovery of gold through a nanofiltration membrane system, comprising:
subjecting a resulting solution after pickling the precipitated iron sludge to cut-off treatment using a nanofiltration membrane to separate nano-sized elemental gold from the solution.

2 . A method for extracting and recovering gold, the method comprising:
(1) performing gold extraction through an electrocoagulation reaction in a water-based solution containing gold using an electrolytic cell and an electrolyte under a direct-current stabilized voltage supply, to obtain a precipitate; (2) performing acid hydrolysis on a resulting precipitate in an acid to obtain a solution after pickling; and (3) filtering and cutting off the solution after pickling to separate nano-sized elemental gold from the solution.

3 . The method for extracting and recovering according to claim 1 , wherein
the electrolytic cell in step (1) comprises an anode and a cathode, and the anode is made of an anode material that can dissolve to release metal ions and produce electropositive colloidal oxides or hydroxides; optionally, the anode is made of a positive trivalent metal anode material; and optionally, the anode is an iron sheet.

4 . The method for extracting and recovering according to claim 1 , wherein
an anode in step (1) is an iron sheet, which undergoes an electrocoagulation reaction to generate an iron hydroxide so as to achieve capture and reduction of gold; and a cathode in step (1) is selected from any one of titanium plates, graphite, stainless steel, and copper sheets.

5 . The method for extracting and recovering according to claim 2 , wherein
the electrolyte is selected from any one of sodium salts, magnesium salts, calcium salts, and potassium salts.

6 . The method for extracting and recovering according to claim 1 , wherein
the electrolyte in step (1) is selected from any one of Na 2 SO 4 , NaCl, NaNO 3 , and Na 2 CO 3 .

7 . The method for extracting and recovering according to claim 1 , wherein
the electrolyte is Na 2 SO 4 , and a mass concentration of the electrolyte is 3.0%.

8 . The method for extracting and recovering according to claim 1 , wherein
the electrolyte is NaCl, NaNO 3 , or Na 2 CO 3 , and a mass concentration of the electrolyte is 0.5%-5.0%.

9 . The method for extracting and recovering according to claim 1 , wherein
an applied voltage for the electrolytic cell in step (1) is 0.5-4.0V.

10 . The method for extracting and recovering according to claim 1 , wherein
a pH range of the aqueous solution in step (1) is 3.0-10.0.

11 . The method for extracting and recovering according to claim 2 , wherein
the acid is an acid with a pH less than 2; and optionally, a concentration of the acid ranges from 1.0 mol/L to 8.0 mol/L.

12 . The method for extracting and recovering according to claim 1 , wherein
a concentration of the nitric acid in step (2) ranges from 3.0 mol/L to 6.0 mol/L; and a solid-liquid ratio of the precipitate and the nitric acid is 1:500-1:50.

13 . The method for extracting and recovering according to claim 2 , wherein
step (2) further comprises stirring or ultrasonication during the acid hydrolysis.

14 . The method for extracting and recovering according to claim 1 , wherein
a temperature of the ultrasonication treatment in step (2) is 50° C.-80° C., and an ultrasonication washing time is 0.5 h or longer.

15 . The method for extracting and recovering according to claim 1 , wherein
in step (3), a cut-off separation of nano-sized gold is carried out using a nanofiltration membrane, and the nanofiltration membrane has a pore size less than 4.0 nm.

16 . The method for extracting and recovering according to claim 2 , wherein
the electrolytic cell in step (1) comprises an anode and a cathode, and the anode is made of an anode material that can dissolve to release metal ions and produce electropositive colloidal oxides or hydroxides; optionally, the anode is made of a positive trivalent metal anode material; and optionally, the anode is an iron sheet.

17 . The method for extracting and recovering according to claim 2 , wherein
an anode in step (1) is an iron sheet, which undergoes an electrocoagulation reaction to generate an iron hydroxide so as to achieve capture and reduction of gold; and a cathode in step (1) is selected from any one of titanium plates, graphite, stainless steel, and copper sheets.

18 . The method for extracting and recovering according to claim 2 , wherein
the electrolyte is selected from any one of sodium salts, magnesium salts, calcium salts, and potassium salts.

19 . The method for extracting and recovering according to claim 2 , wherein
the electrolyte in step (1) is selected from any one of Na 2 SO 4 , NaCl, NaNO 3 , and Na 2 CO 3 .

20 . The method for extracting and recovering according to claim 2 , wherein
the electrolyte is Na 2 SO 4 , and a mass concentration of the electrolyte is 3.0%.

Assignees

• Univ China Mining

Inventors

• Li Peng
• Duan Chenlong
• Dai Guofu

Classifications

• B01D69/02

  characterised by their properties · CPC title

• C25C1/20 Primary

  of noble metals · CPC title

• C23G1/085

  solutions containing HNO3 · CPC title

• B01D2325/0283

  Pore size · CPC title

• B01D61/027

  Nanofiltration · CPC title