Amax Incorporated

Ranko P Crnojevich

Edward I Wiewiorowski

Peter H Yu

Luther R Tinnin

Andrew B Case

Eddie C Chou

Felix D Rando

Courtney S Simons

John D Sweeney

Donald H Wilkinson

Harold Koehler

Jorge L Blanco

The present invention is directed to a method for treating a sludge containing substantial amounts of chromium, aluminum, calcium, iron, and phosphorous. The method comprises forming a slurry of the sludge; reacting the slurry with an acid to dissolve substantially all the aluminum and chromium and provide a solids residue comprising mostly calcium sulfate; separating the chromium/aluminum-containing solution from the solids residue; raising the pH of the chromium/aluminum solution to precipitate chromium as chromium hydroxide; and separating the chromium hydroxide from the remaining aluminum-containing solution. The chromium hydroxide is then enriched with an alkali or earth alkali compound and calcined in an oxidizing atmosphere to convert the chromium to a chromate. The calcine is leached in an aqueous medium at a controlled pH to yield a high concentration, high purity chromate solution suitable for producing metallic chromium or a variety of chromium chemicals.

Recovery of chromium in high purity state from waste materials of

A method is provided for treating sludge containing substantial amounts of chromium, aluminum and iron and residuals of other elements. The method comprises forming a slurry of the sludge in water at a temperature ranging from ambient to 150.degree. F. with the specific gravity of the slurry ranging from about 1.05 to 1.25, and adding a mineral acid to the slurry to provide a pH ranging from about 0.1-3 to dissolve selectively the aluminum and the chromium and leave a solids residue containing gangue material comprising an oxidized iron compound, calcium sulfate, calcium fluoride, calcium silicate among other solids. The pH of the solution is controlled at range of about 2 to 3.5 to precipitate undesirable elements, including iron, without substantially adversely affecting the dissolved chromium and aluminum. The chromium/aluminum-containing solution is separated from the solids therein to provide a substantially purified solution of chromium/-aluminum, and the pH of the solution raised to a range of about 12 to 13.8 to precipitate chromium as chromium hydroxide and provide a pregnant aluminate solution. The chromium hydroxide-containing solution is then subjected to solid/liquid separation to extract chromium hydroxide therefrom and providea pregnant aluminate solution which is thereafter treated to recover alumina therefrom.

Reclaiming of aluminum-chromium waste materials from etching operations

Metal values and alumina are recovered from spent, usually oily, catalysts by oxygen pressure leaching with sodium hydroxide and/or sodium aluminate to dissolve molybdenum, vanadium and/or tungsten and provide a solid, filterable residue containing alumina and cobalt and/or nickel, the residue is digested with sodium hydroxide to give a sodium aluminate solution and a residue enriched in nickel and/or cobalt, alumina is recovered from the sodium aluminate solution as a solid and the remaining supernatant solution is recycled to the oxygen pressure leaching step wherein the alumina content of the aluminate solution is precipitated and a bleed for metals in the aluminate solution is provided.

Cyclic process for recovering metal values and alumina from spent

Selenium is precipitated from solutions containing at least one metal selected from the group consisting of nickel, cobalt, copper, iron, zinc, manganese, magnesium, chromium and cadmium by adding chromous sulfate to the solution to precipitate selenium therefrom.

Production of metals with low selenium contents

Selenium is precipitated from solutions or slurries containing nonferrous metals, particularly nickel by contacting the solution or slurries with a semimetallic chromous precipitant of the nonferrous metal, particularly nickel, which has a nonferrous metal to chromium ratio between about 10:1 and about 200:1 and which has a metallic content between about 50% and about 90%. The semimetallic chromous precipitant of the nonferrous metal is prepared by hydrogen reducing a solution of the nonferrous metal or slurries containing chromous salts in amount to provide the aforementioned nickel to chromium ratios.

Production of nonferrous metals with low selenium contents

A method is provided for the recovery of cobalt from nickel solutions, wherein cobalt is separated from said solution as a precipitate containing cobaltic hydroxide precipitate and also containing nickel, the method comprising dissolving the precipitate for the subsequent recovery of cobalt therefrom by reducing trivalent metal in said precipitate to the divalent state. This is achieved by forming an aqueous slurry of said precipitate acidified with sulfuric acid to a pH ranging from about 0.1 to 2, subjecting the precipitate of said aqueous slurry to electrolytic reduction at the cathode of an electrolytic cell having an insoluble anode, said precipitate being isolated from said anode during said electrolytic reduction and continuing the electrolytic reduction of said precipitate from the trivalent to the divalent state and effect the dissolution thereof.

Cathodic dissolution of cobaltic hydroxide

A method is provided for effecting the dissolution of a cobaltic hydroxide-containing precipitate which may also contain nickel, wherein an aqueous slurry of the precipitate containing trivalent metal is acidified to a pH of from about 0.1 to 2, and the aqueous slurry then treated with an organic reductant to effect substantial reduction of the trivalent metal to the divalent state and hence the dissolution of said precipitate.

Dissolution of cobaltic hydroxide with organic reductant

A method is provided for decreasing the silicon content of relatively pure nickel and/or cobalt powder, wherein silicon is present as an impurity substantially in the oxidic state. The method comprises mixing the metal powder in an aqueous solution of an alkali metal hydroxide, e.g. sodium hydroxide, with the temperature of the solution ranging from ambient to below boiling and maintaining the powder in contact with the solution until the silicon content of the powder has been reduced to the desired level.

Purification of nickel and cobalt metal powders by a caustic wash

A multi-stage leaching process is provided for leaching and refining nickel-copper-sulfur concentrates, a substantial portion of the total nickel present being in an acid-soluble metallic form. The process employs a first stage atmospheric leach in combination with two serially coupled second and third stage high pressure oxidation leaching steps in which process streams are recycled within the overall process, such that a purified nickel solution is continually drawn from atmospheric leach and a purified copper product recovered from a pregnant solution obtained in the third stage leach, a spent copper-sulfuric acid being formed which is recycled back into the process for the recovery of metal values therefrom.

Hydrometallurgical leaching and refining of nickel-copper concentrates,

An improved method is provided for efficiently precipitating metal powder selected from the group consisting of nickel, cobalt and copper from aqueous solutions using sulfur-free hydrogen at elevated pressure and temperature, the improvement residing in adding to the solution a small but effective amount of a catalyst as an anti-plating agent, said catalyst comprising an alkali metal or ammonium salt of a copolymer of maleic acid anhydride and an unsaturated branched chain aliphatic olefinic hydrocarbon containing 4 to 10 carbon atoms.

Growing community of inventors

Gretna, LA, United States of America

Ranko P Crnojevich