Abstract: A method of controlling chemical concentration in electrolyte includes measuring a chemical concentration in an electrolyte, wherein the electrolyte is contained in a tank; and increasing a vapor flux through an exhaust pipe connected to the tank when the measured chemical concentration is lower than a control lower limit value.

Abstract: A process for reducing arsenic content from arsenic-bearing gold concentrate or other arsenic-bearing gold materials to produce a low arsenic-bearing gold concentrate. The process may comprise adding oxygen, water, and/or acid to an acidulated arsenic-bearing gold concentrate slurry and reacting them together in an autoclave at an elevated pressure and temperature in a pressure oxidation step. In one or more examples, the process may further comprise processing the oxidized concentrate slurry in an arsenic re-dissolution step to dissolve unstable solid arsenic compounds, and applying a first solid/liquid separation and wash step to form a first washed slurry/solid and first acid-containing solutions. The process may further comprise reacting the first washed slurry/solid with sulfur dioxide in a reductive leach step, and applying a second solid/liquid separation and wash step to form a second washed slurry/solid and second acid-containing solutions.

Abstract: The present invention provides methods for enhancing chemical reactions of molecules, e.g., biomolecules, with destructible surfactants. The chemical reactions may involve and/or be associate with analysis, e.g., solubilizing, separating, purifying and/or characterizing the molecules. In one aspect, the anionic surfactants of the present invention may be selectively broken up at relatively low pH. The resulting breakdown products of the surfactants may be removed from the molecule/sample with relative ease. The invention has applicability in a variety of analytical techniques.

Abstract: A process for recovering a precious metal from ore includes adding process water containing thiocyanates to ore particles to obtain a pulp. The pulp having a basic pH is contacted with an oxidizing gas containing ozone; and the pulp is contacted with cyanide. Contacting the pulp with cyanide can include adding cyanide subsequently to contacting the pulp with the oxidizing gas containing ozone.

Abstract: A gold thiosulfate leaching process uses carbon to remove gold from the leach liquor. The activated carbon is pretreated with copper cyanide. A copper (on the carbon) to gold (in solution) ratio of at least 1.5 optimizes gold recovery from solution. To recover the gold from the carbon, conventional elution technology works but is dependent on the copper to gold ratio on the carbon.

Abstract: The present invention relates to solutions comprising water and at least one metal cyanide, at least a part of the water being obtained from wastewater which occurs as depleted wastewater in a process for extracting noble metals from noble metal-containing ores by the cyanide process, the process for the preparation of solutions according to the invention and to the use of the solutions according to the invention in a process for extracting noble metals from noble metal-containing ores by the cyanide process, to a process for extracting noble metals from noble metal-containing ores by the cyanide process, wherein the solution according to the invention is used, and to the use of depleted wastewater occurring in the extraction of noble metals from noble metal-containing ores by the cyanide process to the preparation of solutions comprising water and at least one metal cyanide.

Abstract: A method of biotreating and recovering metal values from metal-bearing refractrory sulfide ore using a nonstirred surface bioreactor is provided. According to the method, the surface of a plurality of coarse substrates is coated with a solid material to be biotreated to form a plurality of coated coarse substrates. The coarse substrates have a particle size greater than about 0.3 cm and the solid material to be biotreated has a particle size less than about 250 ?m. A nonstirred surface reactor is then formed by stacking the plurality of coated coarse substrates into a heap or placing the plurality of coated coarse substrates into a tank so that the void volume of the reactor is greater than or equal to about 25%. The solid material is biotreated in the surface bioreactor until the undesired compound in the solid material is degraded to a desired concentration.

Abstract: A process for the oxidative leaching of sulphide mineral species, the method characterized by the method steps of: leaching a slurry containing the mineral species in one or more reaction vessels; circulating a stream of leach liquor to a flash cooler; flashing the liquor in the flash cooler at a pressure less than atmospheric pressure so as to dissipate heat; and recirculating the liquor to the or each reaction vessel.

Abstract: A method is shown for raising the pH of a cyanide leach solution of the type used in a heap leaching mining operation. Lime slurry is mixed with a side stream of barren cyanide solution in a reactor vessel in order to remove carbonate hardness, to regenerate the hydroxide alkalinity and to raise the pH of the resulting recausticized leach solution. A portion of the calcium carbonate precipitate formed in the reactor vessel is retained in order to encourage further crystal growth. Overflow from the reactor vessel passes through one or more cyclone separation stages in order to remove particulate solids. A cyclone overflow stream is directed back to the process to upwardly adjust the pH of the bulk of the barren cyanide solution. A cyclone underflow stream is directed back to the reactor vessel to provide seed crystal nuclei for precipitate growth.

Abstract: The present invention is directed to a precious metal recovery process in which basic ferric sulphates and/or jarosites are controlled by a number of mechanisms, including control of the oxidation reaction conditions in the first autoclave compartment, hot curing of the autoclave discharge slurry, and/or contacting of the autoclave feed slurry with the hot cured discharge liquid.

Abstract: For removal of precious metal from thiocyanate leach solution, precious metal is transferred from precious metal-thiocyanate complex to precious metal-cyanide complex. Preparation of thiocyanate leach solution includes dissolving cyanide in an aqueous liquid and converting the cyanide to dissolved thiocyanate.

Abstract: A heap with precious metal-containing mineral material with precious metal locked within sulfide mineralization is subjected to bio-oxidation followed by acidic thiocyanate leaching to dissolve precious metal. Sulfide sulfur is oxidized during both of the bio-oxidation and the thiocyanate leaching.

Abstract: Precious metal-containing mineral material is subjected to an acidic thiocyanate leach to dissolve the precious metal as a precious metal-thiocyanate complex. A feed of the thiocyanate leach solution may include a large molar ratio of ferric iron to thiocyanate. Precious metal may be removed from pregnant thiocyanate leach solution, such as by transferring precious metal from precious metal-thiocyanate complex to precious metal-cyanide complex and then loading the precious metal-cyanide complex onto an adsorbent material. Remaining cyanide in the thiocyanate leach solution may be converted to thiocyanate for additional leaching of precious metal.

Abstract: A method of flotation processing ores and other mineral materials containing soluble nonferrous base metal and sulfide minerals involves dissolving the soluble nonferrous base metal and precipitating the soluble nonferrous base metal in the form of a floatable precipitate that is collected as part of a sulfide concentrate. The use of an oxygen-deficient flotation gas, such as nitrogen gas, promotes the precipitation of the floatable precipitate. A method for removing dissolved nonferrous base metal from solution involves contacting the solution with a particulate containing sulfide minerals under conditions promoting precipitation of the nonferrous base metal onto the sulfide mineral.

Abstract: Methods for inhibiting depletion of mineral values from pregnant lixiviant solutions comprise contacting the requisite metal ore with a preg-robbing inhibition agent (PRIA) comprising (I) alkyl polyglucoside surfactants; (II) imidazoline based amphoteric surfactants; (III) hydroformylation products of lower (C2–C8) alkanes in an organic solvent medium, and (IV) esters and aldehydes.

Abstract: Processes are provided for recovering precious metals from refractory materials using thiosulfate lixiviants. The processes can employ lixiviants that include at most only small amounts of copper and/or ammonia and operate at a relatively low pH, reduction of polythionates, inert atmospheres to control polythionate production, and electrolytic solutions which provide relatively high rates of precious metal recovery.

Abstract: A method for controlling the extraction of gold from a gold ore by the cyanidation process in which a leaching step including the addition of a lead compound, which is typically lead nitrate or other lead salt, is used. In order to maintain stable conditions in the leaching process, and to use the leaching reagents efficiently, an analysis step is used to monitor the concentration of thiocyanate in the cyanidation step. This value has been found to be directly related to the rate of addition of the lead compound in the pre-leaching or leaching step. Further, the rate of addition of lead compound is also directly related to both the time required for, and the efficiency of, the cyanidation step. By establishing a target value, and a preferred range, for the thiocyanate concentration based on the properties of the ore being processed, optimal extraction conditions can be established in the leaching process and maintained by monitoring the thiocyanate concentration.

Abstract: A method of biotreating a solid material to remove an undesired compound using a nonstirred surface bioreactor is provided. According to the method, the surface of a plurality of coarse substrates is coated with a solid material to be biotreated to form a plurality of coated coarse substrates. The coarse substrates have a particle size greater than about 0.3 cm and the solid material to be biotreated has a particle size less than about 250 ?m. A nonstirred surface reactor is then formed by stacking the plurality of coated coarse substrates into a heap or placing the plurality of coated coarse substrates into a tank so that the void volume of the reactor is greater than or equal to about 25%. The solid material is biotreated in the surface bioreactor until the undesired compound in the solid material is degraded to a desired concentration.

Abstract: A method of processing a mineral composition comprising a refractory material the method comprising milling the composition to a particle size of P80 of less than 25 microns and leaching said composition with a solution comprising lime and/or limestone in the presence of an oxygen containing gas.

Abstract: Precious metal-containing mineral material is subjected to an acidic thiocyanate leach to dissolve the precious metal as a precious metal-thiocyanate complex. A feed of the thiocyanate leach solution may include a large molar ratio of ferric iron to thiocyanate. Precious metal may be removed from pregnant thiocyanate leach solution, such as by transferring precious metal from precious metal-thiocyanate complex to precious metal-cyanide complex and then loading the precious metal-cyanide complex onto an adsorbent material. Remaining cyanide in the thiocyanate leach solution may be converted to thiocyanate for additional leaching of precious metal.

Abstract: The present invention relates to a method for producing a low temperature 0-3 composite material, comprising the steps of providing a mixture, wherein the mixture comprises a liquid phase and a particulate phase and wherein the liquid phase comprises a reactive metal alkoxide; depositing the mixture on to a plastic substrate; and consolidating the mixture to provide a 0-3 composite material, wherein the 0-3 composite material is suitable for use as an electronic component.

Abstract: Methods for inhibiting depletion of mineral values from pregnant lixiviant solutions comprise contacting the requisite metal ore with a preg-robbing inhibition agent (PRIA) comprising (I) alkyl polyglucoside surfactants; (II) imidazoline based amphoteric surfactants; (III) hydroformylation products of lower (C2-C8) alkanes in an organic solvent medium, and (IV) esters and aldehydes.

Abstract: Methods for inhibiting depletion of mineral values from pregnant lixiviant solutions comprise contacting the requisite metal ore with a preg-robbing inhibition agent (PRIA) comprising (I) alkyl polyglucoside surfactants; (II) imidazoline based amphoteric surfactants; and (III) hydroformylation products of lower (C2-C8) alkanes in an organic solvent medium.

Abstract: A method for the treatment of sulfide ores containing silver by pressure oxidation. The method includes the addition of a sulfate-binding material to reduce the formation of jarosite species during pressure oxidation. Silver can then be recovered from the solids portion of the discharge slurry. A jarosite reduction step, such as by a lime boil, that is typically required to recover silver after pressure oxidation can advantageously be eliminated.

Abstract: A method for controlling the extraction of gold from a gold ore by the cyanidation process in which a leaching step including the addition of a lead compound, which is typically lead nitrate or other lead salt, is used. In order to maintain stable conditions in the leaching process, and to use the leaching reagents efficiently, an analysis step is used to monitor the concentration of thiocyanate in the cyanidation step. This value has been found to be directly related to the rate of addition of the lead compound in the pre-leaching or leaching step. Further, the rate of addition of lead compound is also directly related to both the time required for, and the efficiency of, the cyanidation step. By establishing a target value, and a preferred range, for the thiocyanate concentration based on the properties of the ore being processed, optimal extraction conditions can be established in the leaching process and maintained by monitoring the thiocyanate concentration.

Abstract: Roasting of ores with metal values such as precious metal ores for recovery of metal values with conversion of arsenic to an insoluble form in-situ in presence of an additive such as iron and in presence of oxygen injected initially or supplementally in a roaster such as in a circulating fluid bed roaster; volatilized arsenic in roasting of ores may also be converted to an insoluble form in gas phase in a two stage roaster process after removal of solids from a gas phase and contact with an additive at high oxygen concentration in a second stage roaster.

Abstract: A method of leaching sulphidic material that contains metals and arsenic under oxidising conditions and with the aid of microorganisms is characterised by mixing the material with an acid aqueous solution to form a pulp, and in that the material is leached in a first leaching stage at a pH of below 2 and at a temperature that ranges from room temperature to about 55° C. in the presence of an active quantity of microorganisms of the mesophilic and/or moderately thermophilic type, wherewith the major part of the arsenic content of the material and possibly also part of its metal content is/are leached-out and the arsenic leached from said material is oxidised successively to a pentavalent state.

Abstract: Briefly stated, there is provided a method for reducing cyanide consumption in precious metals mining extraction processes involving a sulfur bearing ore body, comprising the steps of providing a precious metal bearing material having intermediate sulfur oxidation products, and exposing the material to sulfur dioxide gas, bisulfite ions or sulfite ions, in a manner to cause at least a portion of the intermediate sulfur oxidation products to be rendered unreactive with cyanide.

Abstract: A method of biotreating a solid material to remove an undesired compound using a nonstirred surface bioreactor is provided. According to the method the surface of a plurality of coarse substrates is coated with a solid material to be biotreated to form a plurality of coated coarse substrates. The coarse substrates have a particle size greater than about 0.3 cm and the solid material to be biotreated has a particle size less than about 250 &mgr;m. A nonstirred surface reactor is then formed by stacking the plurality of coated coarse substrates into a heap or placing the plurality of coated coarse substrates into a tank so that the void volume of the reactor is greater than or equal to about 25%. The reactor is inoculated with a microorganism capable of degrading the undesired compound in the solid material, and the solid material is then biotreated in the surface bioreactor until the undesired compound in the solid material is degraded to a desired concentration.

Abstract: A method for reducing consumption of cyanide and level of carbon fouling during cyanide extraction of gold and silver from their ores by treating the ore or aqueous slurry of the ore with a water-soluble sequestering agent for the base metal species for a time sufficient for the sequestering agent to react with at least a portion of the base metal species.

Abstract: A process for the recovery of one or more metal values from a metal ore material comprising those of one or more values and a matrix material having a sulfur content wherein the sulfur is present in an oxidation-reduction state of zero or less comprising a. forming particulates from particles of said ore and an inoculate comprising bacteria capable of at least partially oxidizing the sulfur content; b. forming a heap of said particulates; c. biooxidizing the sulfur content and d. recovering those one or more metal values.

Abstract: A method for separating gold and/or silver from copper or other contaminant metals is provided in which a suitable filter membrane (64), particularly a nanofilter, is used to form a retentate (134) containing most of the multivalent metal cyanide complexes and a permeate (135) containing most of the precious metal cyanide complexes. The process is particularly applicable to the recovery of gold and/or silver from ores containing these metals and one or more contaminant metals. The precious metal can thereafter be recovered from the permeate (135) and the metal in the multivalent metal cyanide complex from the retentate (134).

Abstract: An ore separation process is provided which begins with a specially designed primary grinding mill. The primary grinding mill grinds the ore into a fine powder which is then blown into the primary sizing baghouse which separates the smaller particles from the larger particles. The oversized particles are channeled to the secondary grinding mill where they are ground again and blown to the secondary sizing baghouse. The grinding process is repeated until all the ore is the proper size. Once the ore has been ground to the proper size it is sent to the ore-roasting oven where it is mixed with a precise amount of air where it is flash heated which initiates the process of separating the values from the wastes. From the ore-roasting oven, the heated ore is channeled to the quench chambers where it is cooled very quickly which results in the breaking up of the ore into its constituent components.

Abstract: A process for refining noble metals from auriferous mines, wherein the auriferous material is first milled and treated with a cyanide solution, and comprising: a step for the pretreatment of the auriferous material, wherein the complexes of cyanide with noble metals are fixed on anionic resins and then incinerated; a predefining step, which comprises an etching of the materials incinerated during the pretreatment with a hydrochloric-nitric solution; and specific steps for refining the gold, palladium, platinum and silver.

Abstract: The process of the present invention is directed to the use of sulfuric acid and/or an organic acid to regenerate spent sorbent from a metal recovery process. The sorbent can be activated carbon.

Abstract: Refractory gold ores are roasted in the presence of added fuels in an oxidizing atmosphere in a fluidized bed at a temperature from 450 to 650° C., which is supplied with oxygen-containing gases; to achieve a low ignition and thus low roasting temperature, sulfur, pyrite or mixtures thereof are used as added fuels.

Abstract: A process for removing precious metals from activated carbon. The activated carbon is contacted with an aqueous solution of methyl ethyl ketoxime and sodium hydroxide.

Abstract: A method for controlling a froth flotation system in a mineral processing operation for recovering metal from a metal source. A rule-based expert system adjusts performance of the froth flotation system.

Abstract: A method for recovering gold from gold-loaded fine carbon residue from a coarse carbon gold recovery process is disclosed. The gold-loaded fine carbon residue is mixed with activated coarse carbon and an aqueous solution of a transfer reagent to form a slurry. In the slurry the reagent promotes transfer of gold from the fine carbon to the coarse carbon. After allowing time for the transfer, gold-loaded coarse carbon is separated from the slurry. Gold can then be recovered from the separated coarse carbon, for example by cyanide leaching followed by electrowinning. More gold can be recovered by adding further coarse carbon and repeating the transfer of gold to that coarse carbon. In one example 66% of gold was transferred from the fine carbon to the coarse carbon in one transfer cycle. About 89% and 96% of gold can be recovered after respectively second and third transfer cycles.

Abstract: A method is provided for flotation of refractory auriferous sulfide using an oxygen-deficient flotation gas. The method is particularly suited for non-selective flotation of different iron-containing sulfide mineral species. Comminution prior to flotation may be performed in an oxygen-deficient environment.

Abstract: An ion exchange resin comprising an ion exchange material dispersed or distributed throughout a polyurethane matrix. The ion exchange material is typically a second polymer which has been chemically modified after dispersion or distribution throughout the polyurethane matrix.

Abstract: The invention provides a process for recovering hydrogen cyanide from an aqueous solution by extracting the hydrogen cyanide into an organic solvent phase. The organic solvent may comprise a neutral organophosphorous compounds, such as compounds selected from the group consisting of alkyl or aryl substituted phosphates, phosphonates and phosphine oxides. In alternative embodiments the organophosphorous compound is tri-butyl phosphate, di-butyl-butyl-phosphonate or tri-alkyl phosphine oxides. The organic solvent may be diluted in an organic diluent, such as an aliphatic or kerosene-type diluent. Alternative dilutions may be used, such as 75%, 50% or 25%. In some embodiments, the pH of the aqueous solution containing dissolved cyanide may be adjusted to between 2 and 8, or between 3 and 7, or between 4 and 6. The organic solvent may be contacted following extraction with a basic aqueous solution to strip cyanide from the organic solvent into a basic aqueous cyanide strip solution.

Abstract: A sodium cyanide composition having a paste-like consistency is provided which comprises sodium cyanide, a base, water, and a rheology modifier. Also provided are processes for producing and using the composition. The composition can be used in applications that require sodium cyanide solution.

Abstract: A method of biotreating a solid material to remove an undesired compound using a nonstirred surface bioreactor is provided. According to the method the surface of a plurality of coarse substrates is coated with a solid material to be biotreated to form a plurality of coated coarse substrates. The coarse substrates have a particle size greater than about 0.3 cm and the solid material to be biotreated has a particle size less than about 250 .mu.m. A nonstirred surface reactor is then formed by stacking the plurality of coated coarse substrates into a heap or placing the plurality of coated coarse substrates into a tank so that the void volume of the reactor is greater than or equal to about 25%. The reactor is inoculated with a microorganism capable of degrading the undesired compound in the solid material, and the solid material is then biotreated in the surface bioreactor until the undesired compound in the solid material is degraded to a desired concentration.

Abstract: A method of biooxidizing sulfide minerals in a nonstirred bioreactor is provided. According to the disclosed method, a concentrate of sulfide minerals is coated onto a plurality of substrates, such as coarse ore particles, lava rock, gravel or rock containing a small amount of mineral carbonate as a source of CO.sub.2 for the biooxidizing bacteria. After the sulfide minerals are coated or spread onto the plurality of substrates, a heap is formed with the coated substrates or the coated substrates are placed within a tank. The sulfide minerals on the surface of the plurality of coated substrates are then biooxidized to liberate the metal value of interest. Depending on the particular ore deposit being mined, the sulfide mineral concentrates used in the process may comprise sulfide concentrates from precious metal bearing refractory sulfide ores or they may comprise sulfide concentrates from metal sulfide type ores, such as chalcopyrite, pyrite or sphalorite.

Abstract: A method for improving bacteria and reagent actions on mineral-bearing particles. In the heap leaching process, the method also increases percolation of the leach solution through the heaped ore without the use of high concentrations of cement, high concentrations of high molecular weight polymers, or high concentration of any other binding agents. The method is accomplished by a process comprising the applying of solutions of varying combinations of bacteria, bacterial nutrients, or leaching reagents, together with surface acting agents onto the ore particles before the ore is formed into a heap. The reagents are applied by spray or foggers or foam into the ore as the ore is mined, transported out of the mine, crushed, or transferred to the heap, and before it is formed into the heap.

Abstract: A process for treating ores or rocks is provided. The process comprises (1) combining the ores or rocks with an acid passivating agent to produce a first combination; (2) contacting the first combination with an aqueous solution comprising (a) manganate ions or source thereof and (b) a base whereby a second combination is produced; and (3) maintaining the pH of the second combination at about 11 to about 13.5. The process can also comprise (1) contacting the ores or rocks with the aqueous solution to produce a third combination; (2) contacting the third combination with an acid passivating agent to produce a fourth combination; and (3) maintaining the pH of the fourth combination at about 11 to about 13.5. The process can be used to prevent acid rock drainage of metal-bearing rocks or to produce a pretreated ore or rock which can further be contacted with a lixiviating agent such as, for example, sodium cyanide to extract metals such as, for example, gold and silver from the pretreated ore or rock.

Abstract: The invention relates to a method of recovering precious metals from oxidic or refractory or semi-refractory ore material containing precious metal. This recovery of precious metal takes place with optimal comminution work and with more efficient and more reliable leaching also of non-oxidic ore material in such a way that the ore material is subjected to material bed comminution in the grinding gap between two rollers which are pressed against one another under high pressure and revolve in opposite directions and afterwards the comminuted ore material is preferably leached using a stirring movement in a container.

Abstract: A method for separating gold from copper in a gold ore processing system. Gold ore containing elemental gold and elemental copper is treated with an aqueous cyanide solution to produce a liquid product containing a gold-cyanide complex and a copper-cyanide complex. The liquid product is then delivered to a nanofiltration membrane which prevents the copper-cyanide complex from passing therethrough while allowing passage of the gold-cyanide complex. Nanofiltration of the liquid product specifically produces (1) a retentate which contains the copper-cyanide complex; and (2) a permeate which contains the gold-cyanide complex. In this manner, the gold-cyanide complex is effectively separated from the copper-cyanide complex. The permeate is then treated (e.g. with activated carbon or elemental zinc) to ultimately obtain elemental gold therefrom. The copper-cyanide complex may either be discarded or treated to recover elemental copper from the complex.

Abstract: A process for treating gold bearing sulphide minerals wherein the minerals are subjected to biological oxidation, the product thereof is separated into light and heavy fractions and gold is recovered from the light fraction using a non-biological process.