Freeport Research and Engineering Co.

Freeport Minerals Company

Freeport Research & Development Company

Phillip D Mollere

Tadeusz K Wiewiorowski

Vivian C Astley

Willis L Thornsberry, Jr

Jody J Taravella

Michael A Murray

David M Dyer

A process for producing high grade silica and fluorine-containing coproducts from fluosilicic acid is described. To produce silica, the fluosilicic acid is reacted with aqueous ammonia to produce a solid silica product and a solution of ammonium fluoride. The solid silica is washed under controlled conditions and further processed to produce a high grade product. The ammonium fluoride solution is concentrated and sold as a concentrated ammonium fluoride solution product or reacted with metal hydoxides or oxides to produce metal fluorides.

Production of silica and fluorine-containing coproducts from fluosilicic

The present invention relates to the processing of phosphoric acid by crystallization starting with phosphoric acid and adding relatively large amounts of fine, relatively pure seed crystals to acid which has been cooled to supersaturated conditions. Crystallization thereafter proceeds under conditions which substantially favor growth on the seeds which are added and disfavor secondary nucleation. The present invention particularly describes a seed crystal generator for use in the foregoing process in which relatively high purity phosphoric acid, containing 60% to 66% P.sub.2 O.sub.5 is cooled to a temperature of at least 5.degree. to 10.degree. C. below zero and thereafter nucleated under agitation for less than ten minutes in a small crystallizing vessel.

Process for seed crystal preparation for phosphoric acid crystallization

The present invention discloses a new method for obtaining a crystallized phosphoric acid of relatively high purity starting with conventional phosphoric acid. The new method is based on crystallization of orthophosphoric acid hemihydrate from the phosphoric acid. Massive nucleation which would lead to the formation of unprocessable masses is avoided in the new method by providing unusually large amounts of fine relatively pure seed crystals of orthophosphoric acid hemihydrate and operating the crystallization process under conditions which favor crystal growth on the seed crystals and disfavor the occurrence of secondary nucleation. To prevent the crystallizing magma from reaching a viscosity which would render further processing difficult the present invention provides for recycling raffinate in an amount sufficient to maintain the solids content of the crystallizing magma below about 40%.

Phosphoric acid crystallization process

A method for the recovery of precious metals such as gold and silver from various ore types is described which involves subjecting a slurry of the ore to a simultaneous leaching and electrodeposition process by mixing the slurry with a reagent such as an alkaline cyanide solution which provides for the leaching requirement and contacting said slurry with a metallic cathode with a negative electric potential applied thereto providing for the electrodeposition requirement. The cathode is made of a metal selected from the group consisting of cadmium, copper, iron, lead, molybdenum, tin, zinc, cobalt, nickel, silver, titanium, tungsten, vanadium and alloys and mixtures containing at least one of these metals. The simultaneous leaching and electrodeposition occur under conditions controlled to afford at least partial dissolution of the precious metal values from the ore, whereby continuous transfer of the precious metal from the ore onto the surface of the cathode is promoted. The resultant electrodeposition product, i.e., the cathode with precious metal values electrodeposited thereon, is then separated from the ore slurry and subjected to a subsequent precious metal recovery step by conventional methods.

Simultaneous leaching and electrodeposition of precious metals

A method for the recovery of precious metals such as gold and silver from various ore types is disclosed which involves subjecting a slurry of the ore to a simultaneous leaching and cementation process with a reagent such as an alkaline cyanide solution providing for the leaching requirement and a reducing metal affording cementation. The reducing metal is selected from the group consisting of cadmium, copper, iron, lead, molybdenum, tin, zinc and alloys and mixtures comprising at least two of these metals. The simultaneous leaching and cementation occur under conditions controlled to afford at least partial dissolution of the precious metal values from the ore, whereby continuous transfer of these values from the ore onto the surface of the reducing metal is promoted. The resultant cementation product, i.e., the reducing metal with precious metal values cemented thereon, is separated from the ore slurry and subjected to a subsequent precious metal recovery step by conventional methods.

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New Orleans, LA, United States of America

Phillip D Mollere