Specialized metallurgical processes – compositions for use therei – Processes – Free metal or alloy reductant contains magnesium
Reexamination Certificate
2000-10-11
2003-12-23
Anthony, Joseph D. (Department: 1714)
Specialized metallurgical processes, compositions for use therei
Processes
Free metal or alloy reductant contains magnesium
C075S961000, C423S109000, C423S150100, C252S184000
Reexamination Certificate
active
06666903
ABSTRACT:
TECHNICAL FIELD
The present invention relates to improved compositions and methods used for the extraction and recovery of metals from starting materials such as mineral ores, recyclable wastes, contaminated soils, toxic wastes such as dusts producing through steelmaking processes (such as electric arc furnace dusts and BOP dusts), and other materials. More particularly, the present invention relates to a methodology using caustic silica solution compositions that enhance the extraction and recovery of metals from mineral ores, recyclable wastes, contaminated soils, toxic wastes such as dusts producing through steelmaking processes (such as electric arc furnace dusts and BOP dusts), and other materials.
BACKGROUND OF THE INVENTION
A wide variety of methods for chemical extraction and/or recovery are known in the art, particularly in regard to extraction and recovery of metals from materials such as mineral ores, recyclable wastes, and contaminated soils. Such methods include, for example, amalgamation that often produces health hazards and clean-up hazards; flotation that requires finely ground, de-slimed, clean, free metal; cyanide treatment that offers specific extraction, but presents environmental hazards; centrifugal concentration which works primarily for free on heavy metals; electrolytic/electrowinning processes that are expensive and slow; thermal/furnace processes that are energy intensive and expensive; and chlorination/bromination processes that require high pressure digestors that are, in turn, expensive, hazardous, and leak-prone.
Representative of the prior art, Rizet, in U.S. Pat. No. 5,549,811, teaches a process for decontamination of soils polluted with metals, wherein the polluted soil is treated with a NaOH solution to remove contaminant metals. By leaching this contaminated soil with a soda-solution containing a concentration of about 6N NaOH, the contaminants are precipitated in the form of hydroxides metals and then extracted via simple solid-liquid separation techniques. Thus, Rizet attempts to prepare contaminant metals for subsequent extraction stages well known in the art.
It will be apparent to those skilled in the art that the extraction solution taught by Rizet contains 2% hydrogen peroxide, an oxidizer, and 25-30% sodium hydroxide. His procedure includes the application of lime in a sufficient quantity to remove silica from the extract solution by effectuating precipitation of aluminosilicates that may have become solubilized. Also included is a second wash of the soil that contains the precipitated aluminosilicates with a 6N soda-solution and pH of 14, thereby tending to redissolve some of the silica that has been precipitated by the lime. By sustaining a basic medium with a pH of 14, Rizet avoids the precipitation of lead in the form of hydroxide. Besides the recovered lead, silica remains in the wash liquid.
Also indicative of the art is European Patent No. 34137 in which Reiterer discloses a process for the hydrometallurgical treatment of materials that contain zinc, wherein pulverized zinc-containing materials are initially subjected to basic leaching with alkali hydroxide. Precipitate is separate from the liquid, and the liquid is diluted with water and acidified to a pH below 7 in order to precipitate SiO. Prior to this SiO precipitation, Cl− and NH+ ions are introduced into the solution. Then, once Cu and Cd have been separated, the Zn-containing solution is subjected to an ion exchange or solvent extraction process, and, if necessary, to an electrolytic purification process.
Since Rizet discloses that approximately 1-3 g/l silica is present in the post-leaching solution, the Examiner concludes that Applicant's caustic silica solution—inherent in Applicant's chemical processing step—and concomitant treatment methodology would have been obvious to those of ordinary skill in the art.
Each of these approaches use an initial alkali-based leaching step to attempt to solubilize the metal contaminant portion and the like so that it may be extracted from the contaminated material. Unfortunately, as will be appreciated by those skilled in the art, only limited extraction of metals from ores, dust, and the like has been hereinbefore obtained using conventional separation methods. It would be advantageous for promoting extraction of metals from such contaminated materials if a leaching solution and concomitant methodology were developed that is capable of achieving levels of metal extraction heretofore unknown in the art.
The present invention overcomes many of the disadvantages of known extraction and recovery methods by providing liquor compositions that, while leaching the contaminated materials under mild conditions, effect a chemical change in the underlying structure of the contaminated materials wherein a permanent proclivity for metal extraction and recovery is attained. The present invention performs this extraction and recovery function while generating relatively innocuous by-products or wastes.
SUMMARY OF THE INVENTION
One aspect of the present invention pertains to the use of liquor compositions for the extraction of preferably a metallic element from a metal-contaminated starting material comprising solids—containing this element—by effectuating preferably prolonged contacting of such starting material with the liquid or liquor to cause the underlying structure of the starting material to be broken down to an extent heretofore unknown in the art. As will be hereinafter described, this breakdown of the underlying, typically complex structure, renders the contaminated starting materials to be more susceptible to metal separation than has been hereinbefore believed possible. Once the starting material has thus been properly chemically treated preferably with a caustic silica solution as will be hereinafter described in detail, a mixture of solids and liquid is formed, thereby effectively solubilizing the metallic element in the liquid, wherein a liquid extract may be readily separated from this mixture of solids and liquid.
It will become clear to those skilled in the art that the compositions of caustic silicate solution of the present invention correspond essentially to saturating levels of silica. It has been discovered that the presence of such a constituted caustic silicate solution afford a synergy of chemical and physical properties that apparently vigorously attack the formerly stubborn, hard-to-crack underlying structure of the silica-containing starting material.
In some preferred embodiments, this caustic silica solution comprises 0.001% to about 5% w/w dissolved silica. In some preferred embodiments, this caustic silica solution comprises silica; and one or more of sodium hydroxide, potassium-hydroxide, and ammonium hydroxide. In some preferred embodiments, the caustic silica solution comprises silica; and one or more of sodium hydroxide, potassium hydroxide, and ammonium hydroxide. In some preferred embodiments, the caustic silica solution comprises silica; and an alkali metal hydroxide. In some preferred embodiments, this caustic silica solution comprises silica; and one or more of sodium hydroxide and potassium hydroxide. In some preferred embodiments, this caustic silica solution comprises silica; and sodium hydroxide. In some preferred embodiments, the caustic silica solution comprises silica and 1-60% w/w sodium hydroxide.
In some preferred embodiments, the leaching or contacting is performed at a temperature of 10-200° C. for a period of 10 minutes to 6 hours. In some preferred embodiments, this leaching or contacting is performed at a temperature of 10-200° C. for a period of 10 minutes to 6 hours under a pressure of 0.1 to 5 MPa. In some preferred embodiments, this starting material comprises a mineral ore, soil, toxic waste, or dust produced through steelmaking processes. As will be appreciated by those skilled in the art, some preferred embodiments are designed to perform the extraction of the present invention upon starting material that comprises dust produced by an electric arc furnace. Some
Anthony Joseph D.
Discovery Resources, Inc.
Harrison Law Office, PC
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