Method for biological recovery of metals from electrical and electronic waste

Patent metadata

Field	Value
Publication number	US-2024141457-A1
Application number	US-202118273597-A
Country	US
Kind code	A1
Filing date	Jan 28, 2021
Priority date	Jan 28, 2021
Publication date	May 2, 2024
Grant date	—

Abstract

The present invention relates to a method for the biological recovery of metals in electric and electronic waste, which comprises a) inoculating a series of iron-oxidizing microorganisms and a mineral medium or fertilizers into an immobilized biomass column; b) performing a stage of biological oxidation of the iron II ions present in said mineral medium or fertilizers to iron III ions; c) irrigating a liquid phase into leaching columns that house an electrical material or one or more printed circuit boards from which metals are to be recovered, the iron III ions being reduced to iron II oxidizing the metals, and separating the metals by means of the dissolution thereof; and d) extracting the metals from the solution. The invention operates under a cyclic process that allows the iron II solution being re-circulated to the biomass column.

First claim

What is claimed is:

1 . A method for the biological recovery of metals in electric and electronic waste, comprising:
a) inoculating a series of aerobic iron-oxidizing microorganisms and a mineral medium formed by different salts in solution or fertilizers into an immobilized biomass column; b) performing, in the biomass column, a first stage of biological oxidation of iron II ions present in the mineral medium or fertilizer to iron III ions, the first stage being catalyzed by a metabolic activity of the iron-oxidizing microorganisms and performed within a previously fixed range of temperature, controlling the pH of the mineral medium or fertilizers, the first stage lasting for at least two hours; c) irrigating a liquid phase comprising the iron III ions into at least one leaching column configured for housing an electrical material or one or more printed circuit boards of an electrical material or electronic waste from which metals are to be recovered, the iron III ions being reduced to iron II oxidizing the metals, and separating the metals of interest using a dissolution thereof, the electrical material or the one or more printed circuit board or boards being in contact with the liquid phase inside the leaching column for at least one hour; and d) extracting the metals of interest from the solution.

2 . The method of claim 1 , wherein previous to step c) the method comprises separating the iron-oxidizing microorganisms that has been detached from the biomass column out of the biomass column, a solid phase comprising the iron-oxidizing microorganisms and the liquid phase comprising the iron III ions.

3 . The method according to claim 1 , wherein step d) comprises reducing the extracted metals of interest from soluble state to metallic state through a cementation process which provides a spontaneous reaction between soluble copper II, extracted from the electrical material or from the one or more printed circuit boards, and the metallic iron, wherein in the spontaneous reaction the soluble copper II is reduced to copper metal and the metallic iron is oxidized to soluble iron II.

4 . The method according to claim 1 , wherein step d) comprises reducing the extracted metals of interest from soluble state to metallic state through electrolysis using stainless steel or lead electrodes.

5 . The method according to claim 1 further comprising automatically tracking the biological oxidation of the iron II ions to iron III ions and a metal extraction in the at least one leaching column using one or more optical sensors that continuously and non-invasively monitor a color change of the liquid of the at least one leaching column as a result of the solubilization of the metals being extracted.

6 . The method according to claim 5 , wherein the tracking being executed simultaneously.

7 . The method according to claim 5 , wherein at least the tracked biological oxidation is further processed, calibrated and/or diagnosed using a processing unit operatively connected to the one or more optical sensors.

8 . The method according to claim 1 , wherein the irrigation of step c) is performed in batches programmed and controlled using an automatic control device.

9 . The method according to claim 1 , wherein in step c) the liquid phase is irrigated into two leaching columns, which automatically exchange the liquid phase from one column to the other by an automatic control device.

10 . The method according to claim 1 , wherein the different salts of the mineral medium include an iron II salt and salts that provide nitrogen, sulfur, phosphorus, magnesium, potassium, and calcium.

11 . The method according to claim 10 , wherein the mineral medium comprises the following composition: 15-60 g/L of FeSO 4 ·7 H 2 O, 3 g/L of (NH 4 ) 2 SO 4 , 0.5 g/L of MgSO 4 ·7H 2 O, 0.5 g/L of K 2 HPO 4 , 0.10 g/L of KCl and 0.01 g/L of Ca(NO 3 ) 2 ·4 H 2 O.

12 . The method according to claim 1 , further comprising tracking an activity of the iron-oxidizing microorganisms in the immobilized biomass column in the step b) by performing the following steps:
extracting and cleaning a support material from the biomass column; preparing a solution with a same mineral medium composition but without the iron salt FeSO 4 ·7 H 2 O; extracting a specific amount of sample, preferably 2 ml, from a liquid resulting from the cleaning of the support material and centrifuging it for 10 minutes at 5000 rpm; eliminating a surplus and adding another specific amount, preferably 2 ml, of the mineral medium but without the iron salt FeSO 4 ·7 H 2 O; stabilizing the temperature by putting the sample in a thermostatic bath at 30° C.; adding another specific amount, preferably 2 ml, of the mineral medium with the iron salt FeSO 4 ·7 H 2 O and performing homogenization; extracting a specific amount, preferably 1 ml, of the mineral medium and introducing it in a container which is again placed in said thermostatic bath under mechanical stirring; introducing an oxygen microsensor in the container until contacting the sample or introducing the sample in the container with a sensor adhered thereto; and recording a progression of the oxygen concentration via the microsensor or the sensor and determining a biological activity of the sample based on a time progression slope obtained.

13 . The method according to claim 12 , further comprising at least one of:
linking an activity of the sample with the concentration of iron-oxidizing microorganisms using a prior calibration; and calibrating the oxygen microsensor in an oxygen-free aqueous medium and under saturation conditions at a constant temperature.

14 . The method according to claim 1 , wherein step c) further comprises re-circulating iron III from a lower part of the at least one leaching column to an upper part thereof, step c) being performed at room temperature and at a pH less than 1.8.

15 . The method according to claim 1 , wherein the method further comprises: e) recirculating the solution to the biomass column.

Assignees

• Univ Catalunya Politecnica

Inventors

• Dorado Castaño Antonio David
• Gamisans Noguera Xavier
• Solé Sardans Montserrat
• Lao Luque Concepción
• Miquel Grau Ramon
• Escobet Canal Antoni
• Escobet Canal Teresa

Classifications

• C22B3/18 Primary

  with the aid of microorganisms or enzymes, e.g. bacteria or algae · CPC title

• C22B3/46

  by substitution, e.g. by cementation · CPC title

• C22B7/006

  Wet processes · CPC title

• C22B15/0065

  Leaching or slurrying (with organic compounds C22B3/16) · CPC title

• C22B15/0091

  by cementation · CPC title