Extraction of trace metals from fly ash

• US 4,475,993 A
• Filed: 08/15/1983
• Issued: 10/09/1984
• Est. Priority Date: 08/15/1983
• Status: Expired due to Fees

• Current Assignee: United States Department of Energy (Government of the United States of America)
• Original Assignee: United States Department of Energy (Government of the United States of America)
• Inventors: Blander, Milton, Wai, Chien M., Nagy, Zoltan
• Primary Examiner(s): Andrews, R. L.
• Application Number:
  US06/523,492
• Time in Patent Office: 421 Days
• Field of Search: 75/25, 75/62, 75/63, 75/71-72, 75/83, 75/77, 75/78, 75/80, 75/86, 75/28, 204/64 R, 204/64 T, 204/66, 204/71
• US Class Current: 205/367
• CPC Class Codes: C01G 1/06 Halides
• CPC Class Codes: C22B 11/023 from pyrometallurgical residues, e.g. from ashes, dross, flue dust, mud, skim, slag, sludge
• CPC Class Codes: C22B 13/02 by dry processes
• CPC Class Codes: C22B 15/0056 Scrap treating
• CPC Class Codes: C22B 17/02 by dry processes
• CPC Class Codes: C22B 19/00 Obtaining zinc or zinc oxide
• CPC Class Codes: C22B 34/1222 using a halogen containing agent
• CPC Class Codes: C22B 47/00 Obtaining manganese
• CPC Class Codes: C22B 58/00 Obtaining gallium or indium treatment or purification of solutions by liquid-liquid extraction, by ion-exchange or by adsorption C22B3/20
• CPC Class Codes: C22B 7/02 Working-up flue dust
• CPC Class Codes: C25C 3/00 Electrolytic production, recovery or refining of metals by electrolysis of melts C25C5/00 takes precedence
• CPC Class Codes: Y02P 10/20 Recycling
• CPC Class Codes: Y10S 75/961 Treating flue dust to obtain metal other than by consolidation

Abstract

A process for recovering silver, gallium and/or other trace metals from a fine grained industrial fly ash associated with a process for producing phosphorous, the fly ash having a silicate base and containing surface deposits of the trace metals as oxides, chlorides or the like, with the process being carried out by contacting the fly ash with AlCl₃ in an alkali halide melt to react the trace metals with the AlCl₃ to form compositions soluble in the melt and a residue containing the silicate and aluminum oxide or other aluminum precipitate, and separating the desired trace metal or metals from the melt by electrolysis or other separation techniques.

Claims

1. A process for recovering one or more trace metals from a fine grained fly ash having a silicate base and a surface with deposits of the trace metals in a concentration less than about 1 wt. %, the trace metal being selected from the group consisting of Ag, Cu, Fe, Cd, Ga, Mn, Pb, Ti, Zn and mixtures thereof, comprising the steps of

contacting the fly ash with AlCl₃ in an alkali halide melt for a time sufficient for the AlCl₃ and trace metals to react and form trace metal compositions soluble in the melt and a silicate based residue, and

separating the residue from the melt.

2. The process of claim 1 wherein the contacting step is carried out at a temperature in the range of about 300°

-1000°

C.

3. The process of claim 1 including the step of separating one or more of the trace metals from the melt.

4. The process of claim 3 wherein the separation step is carried out by electrolysis to produce one or more of the trace metals.

5. The process of claim 4 wherein said trace metals include gallium.

6. The process of claim 4 wherein said trace metals include silver.

7. The process of claim 4 wherein said trace metals include cadmium.