Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
  • C22B11/00—Obtaining noble metals
  • C22B11/04—Obtaining noble metals by wet processes
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B7/00—Halogens; Halogen acids
  • C01B7/09—Bromine; Hydrogen bromide
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B9/00—General methods of preparing halides
  • C01B9/04—Bromides

Definitions

• Leaching with cyanide dissolves gold, for example, by producing a gold cyanide complex Au(CN) 2 ⁇ .
• Gold may be recovered from the leaching solution by various techniques, including precipitation with zinc, carbon adsorption, ion exchange or the like.
• cyanide leaching suffers from well known disadvantages. Leaching rates are slow, contact times in the range of 24-72 hours being common in the case of gold ores. Because of the toxicity of cyanide, care must be exercised to maintain cyanide solutions on the alkaline side in order to prevent the release of hydrogen cyanide gas. Severe environmental restrictions must be observed, requiring careful monitoring and control of all process purge streams. Spent cyanide leaching solutions must be subjected to waste treatment operations before discharge to the environment.
• Gold has also been leached commercially with aqua regia, in which case the gold may also be recovered by reduction with zinc metal, or by raising the pH of the leaching solution.
• this method is highly unattractive because aqua regia is expensive, highly corrosive and emits toxic fumes. Moreover, it readily dissolves base metals and dissolves gold only relatively slowly in aqueous solution.
• Thiourea has also been used as a lixiviant for the dissolution of gold from ores. Though generally effective for this purpose, thiourea is subject to oxidative degradation and is, thus, prone to high consumption levels in extracting gold from its ore.
• Shaeffer U.S. patent 267,723 describes a process in which ore is roasted in a vat, water added to the roasted ore, and liquid bromine added to produce a mixture which is agitated, thereby dissolving the gold in the water in the form of a bromide. After filtration to separate the solids, gold is precipitated from the solution by oxalic acid or ferrous ion.
• EPO published specification 0 233 918 describes an alkaline concentrate for use in recovering gold from sources thereof.
• This concentrate contains between about 1% and about 6% by weight bromate ion, between about 55% and about 10% by weight equivalent perbromide ion, has a molar ratio of bromate ion to the sum of perbromide ion and molecular bromine of between about 0.05 and about 0.8, has a bromide ion concentration in excess of [Br 2 ] + [Br 3 ⁇ ] of between 3% and 19% by weight, and exhibits a pH of between about 6.5 and about 7.5.
• Example 1 describes an alkaline concentrate that contains 31.82% by weight * sodium perbromide, 2.14% by weight molecular bromine,
• Example 3 of this specification describes the acidification of this concentrate by mixing 1.4 g of the concentrate with 0.8 g 48% hydrobromic acid. The application further describes
• Wilson U.S. patent 3,709,681 describes a process in which a finely divided source of noble metal is treated with a solution containing a ketone solvent, dissolved iodine, bromine or chlorine, a halide salt, and preferably glacial acetic acid.
• the noble metal content of the treatment solution is recovered by displacement onto a non-noble metal surface such as aluminum foil.
• Homick et al. U.S. patent 3,957,505 describe a process in which gold bearing material is treated in an aqueous solution consisting of iodine and a water soluble iodide salt to produce a solution containing dissolved gold iodide salts.
• Gold metal is precipitated from the solution by mixing of the solution with a reducing agent such as hydroxylamine, hydrazine, sodium thiosulfite and the like.
• a reducing agent such as hydroxylamine, hydrazine, sodium thiosulfite and the like.
• Iodine from the spent aqueous solution is recovered by acidification of the solution and addition of an oxidizing agent such as hydrogen peroxide, potassium permanganate, sodium chromate, chlorine or bromine to precipitate elemental iodine.
• McGrew et al. U.S. patent 4,557,759 describe a process for the hydrometallurgical recovery of gold from materials containing gold by leaching the materials with a lixiviant containing iodine.
• the lixiviant is prepared by saturating an aqueous solution of iodide with iodine.
• iodine reacts with the sulfide and is converted to iodide.
• Additional elemental iodine is then added to this iodide bearing solution until the desired concentration of total iodine and ratio of iodine to iodide are achieved for maximum leaching efficiency.
• the lixiviant is then circulated through the ore zone until all the gold is dissolved. Gold is subsequently recovered on activated charcoal. The excess iodide formed during the process is reoxidized to iodine electrochemically in a special diaphragm cell to regenerate the lixiviant.
• the desired concentration of iodine in the lixiviant is between 1 and about 20 grams per liter.
• Copending and co-assigned application Ser. No. 577,677 describes a process for generating bromine in aqueous solution.
• An aqueous solution containing 0.5 to 8.8 moles per liter bromide ion and having a pH of 0 to 6 is passed continuously through an electrolytic cell for generation of bromine at the anode. Both divided and undivided cells are disclosed. Conversions per pass through the cell system are in the range of 4% to 50%.
• the application describes further process steps in which the bromine solution produced by electrolysis is used as a leaching solution for recovery of gold from ore.
• Example 6 describes a leaching solution containing 0.68% by weight equivalent molecular bromine, about 0.43% by weight bromide ion, and about 0.43% by weight sodium ion.
• the cathode side may be used for recovery of gold from the leachate, which preferably contains 1.2xl0 ⁇ - > to 1.2x10 " ⁇ moles per liter AuBr 4 ⁇ , 0.4 to 3.0 moles per liter bromide ion, and 0.4 to 3.0 moles per liter sodium ion.
• the pH is preferably 0 to 3. Dadgar et al., J. Phvs. Chem.. 68. 106 (1964) and Dadgar et al., J. Inorganic Nucl. Chem., 33, 4155 (1971) report that the equilibrium constant for the ion pair formation increases with the reciprocal of dielectric constant of the medium (organic solvent-water mixtures) .
• Bahl et al. U.S. patent 4,190,489 describe a composition and method for etching gold, particularly gold layers on ceramic substrates.
• the composition is prepared, for example, by mixing potassium bromide (75g), elemental bromine (25g), and water (100 ml.). This solution is effective for recovery of gold from ceramic substrates at essentially room temperature.
• Bahl et al. 4,375,984 describe a process in which an alkaline metal bromide/bromine solution is used to etch gold from a substrate.
• the etching solution may be prepared, for example, by mixing potassium bromide (2g), bromine (one gram), and water (25 ml.) Gold dissolved in the etching solution is recovered as metallic gold, either by precipitation using an alkali metal hydroxide or by decomposition in which the etching solution is driven off.
• the alkali metal bromide/bromine etchant solution may be regenerated by the addition of an acid thereto.
• Kalocsai Bl 4,684,404 based on re-examination of U.S. patent 4,684,404, describes dissolution of metallic gold in a reagent comprising a protic solvent such as water or alcohol, a nonreducing cation source such as sodium, potassium, ferrous or ammonium, and a source of free bromine such as molecular bromine, bromine water, or an inorganic or organic bromine containing compound from which bromine can be liberated in the reagent.
• the solution further contains a strong oxidizing agent such as hydrogen peroxide, sodium peroxide, potassium peroxide, sodium permanganate, potassium permanganate, potassium chromate or ferric sulfate.
• exemplary reagents disclosed by Kalocsai is a composition (Example 28) containing 1.0% v/v Br 2 , 1% w/v NaBr, and 0.6% w/v NaOH, and having a pH of 7.35.
• Sergent et al. U.S. patent 4,637,865 describe a process for extracting a precious metal from a source material by contacting the source material with an aqueous leaching solution containing a leaching agent comprised of an N-halohydantoin compound.
• Leaching solutions are described containing l,3-dibromo-5,5-dimethylhydantoin, l-bromo-3-chloro-5,5-dimethylhydantoin and 1,3-dichloro- 5,5-dimethylhydantoin.
• Precious metal may be removed from the leaching solution by precipitation of the less noble metal, ion exchange, treatment with activated carbon, solvent extraction or electrowinning.
• Simpson U.S. patent 4,439,235 describes a process for removing precious metal values from comminuted carbonaceous ores in which the comminuted ore is contacted with an aqueous solution of hypochlorite, iron ion, and acid.
• Falanga et al. U.S. patent 4,319,923 teaches a process in which gold and palladium are etched with a potassium iodide/iodine etching solution and the metal is recovered from the solution by addition of alkaline compound, preferably KOH, to increase the pH to at least 12.5 and precipitate metallic gold from the solution.
• alkaline compound preferably KOH
• a borohydride is used to precipitate palladium.
• This concentrated aqueous bromine mixture is pumped to a second mixing zone where it is diluted with a larger volume of water to produce a diluted stream of aqueous bromine, and the latter stream is further diluted with a large body of water to produce a highly dilute aqueous bromine solution in substantially quantitative yield from the mineral acid and the bromide/bromate salt solution.
• the process as described is useful in the bromination of swimming pool water.
• the reference contains no mention of the use of bromine or bromides in the recovery of precious metals from sources thereof.
• bromine is a corrosive, fuming liquid which generates a suffocating vapor and must be subjected to special handling.
• Bromine may be dissolved to a certain extent in water, or incorporated in an alkali metal perbromide solution, but these aqueous materials exhibit a substantial bromine vapor pressure, so that their use also commonly entails special handling.
• molecular bromine can be generated from the acidification of alkali metal bromates, but by themselves bromates provide only a limited source of molecular bromine.
• bromate salts have a high crystallization temperature which makes them inconvenient to use as leaching agents for precious metals.
• an improved process for the hydrometallurgical recovery of gold and silver from ores or other sources thereof in particular, the provision of such a process which- provides a substantial source of bromine for dissolution of a metal without requiring the handling of liquid bromine or solutions having a substantial bromine vapor pressure; the provision of such a process which avoids the use of cyanide; the provision of such a process which may be used for recovery of gold from various types of ores, including refractory ores; and the provision of a such a process which produces a leachate from which gold or silver metal may be readily recovered.
• compositions useful and effective for the leaching of gold and silver from source materials include the provision of compositions useful and effective for the leaching of gold and silver from source materials; the provision of such compositions which contain a substantial source of molecular bromine; the provision of such compositions which do not exhibit a high bromine vapor pressure; the provision of such compositions which exhibit low thermodynamic crystallization temperatures so they will not freeze during storage or transport even in harsh climates; the provision of such compositions which exhibit a high degree of freeze/thaw stability; the provision of such compositions which can be used directly or with water dilution, and which do not require prior activation with acid. It is a further object of the present invention to provide compositions that are useful as disinfectants, and in particular for the control of microorganisms in swimming pool water and cooling tower water.
• the present invention is directed to a composition the formulation of which comprises at least 25% by weight bromine, between about 4% and about 30% by weight hydrobromic acid, and between about 4% and about 15% by weight of a metal bromide.
• the metal bromide is selected from among LiBr, NaBr, KBr and CaBr 2 .
• the composition comprises an excess of bromide ion over bromine of at least about 5% expressed in weight percentage of excess bromide ion, and has a pH of not greater than about 1.0.
• the invention is further directed to a composition the formulation of which comprises between about 10% and about 40% by weight bromine, between about 4% and about 20% of a metal bromide, between 5% and about 24% hydrobromic acid, and at least about 10% by weight of a polar organic solvent (i.e., alcohol or acid).
• a polar organic solvent i.e., alcohol or acid.
• the metal bromide is selected from among lithium bromide, sodium bromide, potassium bromide and calcium bromide.
• the invention is also directed to a method for recovering a precious metal, such as silver or gold, from a source thereof.
• the method comprises preparing a leaching solution by dilution with water of a concentrate of the type described above, and contacting said source with the leaching solution, thereby producing a leachate containing the precious metal.
• compositions of the invention may further be used in a method for controlling micro-organisms in a body or stream of water.
• Bromine from a concentrate of the type defined above is introduced, either directly or after dilution, into the body or stream of water in amounts sufficient to suppress growth of micro-organisms in said body or stream.
• Fig. 1 is a plot of solubility vs. bromine concentration for tests of solubility of gold in the diluted concentrates of Example 5 herein;
• Fig. 2 is a plot of amount of gold dissolved vs. time for simulated batch kinetic tests of the dissolution of gold in the concentrates of Example 5 herein;
• Fig. 3 is a plot of gold dissolved vs. time for rotating disk kinetic tests of the dissolution of gold in the concentrates of Example 6 herein;
• Fig. 4 is a plot of amount of gold dissolved vs. time for simulated batch kinetic tests of the dissolution of gold in the concentrates of Example 6 herein.
• Fig. 5 is a plot of total residual oxidant (TRO) content of cooling tower water vs. time during the course of the cooling tower water treatment tests of Example 8; and Fig. 6 is a plot of bacterial density in the cooling tower water vs. time during the tests of Example 8. This plot is superimposed on the plot of Fig. 5.
• TRO total residual oxidant
• inorganic perbromide concentrates have been discovered which may be used advantageously in a variety of applications.
• these concentrates may be diluted with water to provide aqueous working solutions that are used in practicing the method.
• the concentrates may be metered into a circulating stream of the body of water to be treated.
• the concentrates generally contain a substantial percentage of equivalent molecular bromine and are acidic, having a pH of zero or below, they exhibit remarkably low vapor pressures. This facilitates handling of the concentrates and avoids the hazards that are incurred where molecular bromine is used in comparable applications.
• compositions of the invention are advantageously adapted for shipping, storage and/or use in harsh climates.
• Various of these concentrates exhibit favorable freeze/thaw stability, and certain of them exhibit exceptionally low thermodynamic crystallization temperatures.
• the compositions of the invention are formulated from a metal bromide, a hydrogen halide acid, molecular bromine, and a protic solvent.
• the protic solvent may be water, alcohol or an organic acid, or a mixture thereof.
• compositions of the invention may contain 10-40% by weight equivalent molecular bromine, defined in molar terms as the sum of the actual molar concentration of molecular bromine, the molar concentration of perbromide ion, the molar concentration of hypobromous acid, and the molar concentration of hypobromite ion.
• equivalent molecular bromine defined in molar terms as the sum of the actual molar concentration of molecular bromine, the molar concentration of perbromide ion, the molar concentration of hypobromous acid, and the molar concentration of hypobromite ion.
• the molecular bromine concentration is between about 30% and about 35% by weight.
• Each of the compositions is prepared by mixing a source of halide ion with molecular bromine in such proportions that the bromide ion is in excess.
• Halide sources generally include both a metal halide salt and a hydrogen halide.
• the halide ion is bromide and the molar ratio of bromide ion to molecular bromine in the formulation is between about 1.2:1 and about 2.0:1, most preferably between about 1.4:1 and about 1.8:1.
• the molecular bromine combines with bromide ion to form perbromide or a mixed perhalide ion in accordance with the equations:
• Hydrogen halides used in preparing the composition include HC1, HI and HBr, preferably the latter.
• the concentrates of the invention further contain an alcohol or a low molecular weight organic acid.
• Alcohols and organic acids have a lower dielectric constant than water. Because the equilibrium constant for the above reactions increases with the reciprocal of the dielectric constant, the inclusion of an organic solvent in the composition also conducts to maintaining a low bromine vapor pressure at a high molecular bromine concentration.
• Useful organic acids include acetic, propionic, succinic, adipic and the like.
• Useful alcohols include methanol, butanol, and the like.
• compositions containing alcohol and bromine can be unstable, under certain circumstances explosive, due to reaction of alcohol with bromine.
• organic solvents other than alcohols be used.
• Br 2 /alcohol compositions can be stable, and use safely, if the alcohol content is sufficiently low.
• Bowman, et al. report that methanol/Br 2 compositions are essentially nonreactive, provided that the alcohol content is less than 10% by volume on an alcohol + Br 2 basis.
• compositions of the invention which contain hydrobromic acid and an organic protic solvent are generally formulated from:
• compositions are formulated from:
• Therraodynamic crystallization temperatures are in the range of between about -30°C to about -50°C at 34% Br 2 for compositions in which water is the solvent, and between about -55°C and about -68°C for compositions in which the solvent comprises an organic solvent.
• pH is less than 1.0 and generally less than 0.20.
• Preferred compositions have a pH ⁇ 0.
• compositions are formulated from:
• compositions are formulated from:
• such formulations may contain __ 30%, optimally 32-36% Br 2 , and a molar excess of bromide over Br 2 of __ 30%.
• Similar compositions in which HC1 is substituted for HC1 are preferably formulated from:
• the sodium ion content of the formulation be in the range of between about 1% and about 3% by weight, and that the molar ratio of Na+ to equivalent Br 2 be no greater than about 0.8. It has been found that such relatively low proportions of Na + conduct to a relatively low thermodynamic crystallization temperature, and to excellent freeze/thaw stability of the concentrate.
• a preferred formulation for a freeze/thaw stable NaBr 3 concentrate is:
• An especially preferred low Na+ composition comprises
• Calcium bromide compositions exhibit exceptionally low vapor pressure at high equivalent molecular bromine concentrations. This is believed to be attributable to the greater ionic strength of calcium bromide as compared to alkali metal bromides. Greater ionic strength tends to increase the equilibrium constant for the reactions:
• the Ca(Br 3 ) 2 concentrates have a bromine partial vapor pressure of less than about 40 mm Hg at 20°C, while at 34% equivalent molecular bromine, they have a bromine partial vapor pressure of less than about 50 mm Hg at such temperature.
• calcium perbromide compositions provide an especially low thermodynamic crystallization temperatures (TCTs), e.g., in the range of between about -50°C and about -60°C where water only is the solvent, and below -60°C where the solvent comprises an organic solvent. Such TCTs are also believed to be attributable to the greater ionic strength of these formulations as compared to alkali metal perbromides.
• TCTs thermodynamic crystallization temperatures
• Calcium perbromide compositions preferably are formulated from:
• the concentrates described above are preferably prepared by adding the bromide or other halide salt and hydrogen halide to protic solvent, and then adding liquid bromine to the acidic bromide salt solution. This sequence insures the presence of an excess of bromide ion for reaction with the liquid bromine to form perbromide or XBr 2 ⁇ ion (where X is halide) during bromine addition.
• saturated or nearly saturated premix solutions are prepared for both the bromide salt and hydrogen halide, and these premix solutions are added to water to produce a precursor solution to which the liquid bromine is added.
• a solution containing an organic protic solvent may be prepared by mixing:
• an NaBr 3 concentrate is preferably prepared by mixing:
• the concentrates are preferably prepared as described above, they may also be provided by acidification of a alkaline solution of bromate salt and bromide salt.
• a alkaline concentrate can be prepared, for example, in the manner generally described in U.S. Ser. No. 401,036 (attorneys' docket no. GLC 4007A) . Acidification converts the bromate to bromine in accordance with the reaction:
• compositions of the invention are hydrogen perbromide concentrates formulated from:
• composition preferably contains:
• these HBr 3 compositions exhibit a bromine partial vapor pressure of less than about 40mm-Hg.
• compositions of the concentrates of the invention are formulations, i.e., summaries of the components from which the concentrates are formed in the relative proportions used in forming the concentrates. As indicated, these formulations equilibrate to convert Br 2 and Br- to Br 3 ⁇ . Additionally, some of the Br 2 reacts with water to produce hypobromous acid, which in turn dissociates to a limited degree:
• the exact equilibrium composition of each of the formulations can be computed.
• Applicants invention encompasses to such equilibrated compositions, however produced.
• the concentrates are defined in terms of their formulation from water, bromide salt, hydrogen halide and liquid bromine in the manner described above.
• the concentrates of the invention are diluted to produce a leaching solution that is used essentially in the manner described in copending and coassigned application Ser. No. 401,036 (attorneys' docket number GLC 4007A) .
• a concentrate of the type described above is diluted to provide a leaching solution containing between about 0.01% and about 1% by weight, preferably about 0.02% to about 0.5% by weight, equivalent molecular bromine, between about 0.005% and about 10%, preferably about 0.01% to about 1%, by weight bromide ion, and between about 0.005% and about 15%, preferably about 0.01% to about 1.5%, by weight total halide ion.
• a more concentrated leaching solution may be used. Such may be prepared from the above described concentrates by modest dilution with water. In some instances, the concentrate may even be used directly for dissolution of metallic gold or silver.
• Gold and silver are recovered from a source thereof, such as comminuted gold ore, by contacting the source material with the aqueous bromine leaching solution.
• a source thereof such as comminuted gold ore
• oxidation and complexing of the gold is believed to proceed in accordance with the equations:
• the relative proportions of ore (or other source material) and leaching agent may be such that the leaching slurry contains between about 1 and about 100 lbs. active agent per ton of source.
• Active agent in this instance is defined as the sum of the amounts of bromide, .perbromide, metal hypobromite, hypobromous acid, and molecular bromine in the leaching solution.
• the source material is a refractory ore
• Such may be accomplished by methods known to the art such as roasting or pressure oxidation. Roasting may be sufficient pretreatment if carried out at a temperature of 500-750°C.
• the leaching composition and method of the invention also may be used advantageously for recovery of gold from high grade non-refractory ores, low grade refractory and oxide ores, electronic component scraps, jewelry scrap and similar low grade refractory and oxide ores.
• the composition and method may be used for recovery of silver from various sources, including photographic film.
• the slurry of ore in leaching solution is preferably agitated to promote transfer of precious metal from the ore particles to the aqueous phase.
• a leachate is thus produced containing gold or silver complexed with bromide ions.
• Leaching may be carried out at ambient temperature. Preferably, contact is maintained for a period of 2 to 6 hours to achieve the maximum transfer of gold or silver from the ore.
• the leachate is separated from the leached ore, as by filtration.
• the filtrate (leachate) is washed with an aqueous washing medium, the spent wash solution is combined with the filtrate, and the combined filtrate and wash solution is treated for recovery of the precious metal therefrom.
• the filter cake is washed with a 2-4 molar HC1. Washing the filter cake in such fashion may be effective to remove further quantities of silver in the form of AgCl 2 ⁇ from the cake.
• a solution of 4M HC1 is especially preferred.
• Gold may be recovered from the combined filtrate and wash solution by conventional means such as zinc or aluminum precipitation, ion exchange, carbon adsorption, or electrowinning.
• the leaching solution of the invention may be used for recovery of silver.
• the concentrate may be added to the body of water in various different ways.
• the concentrate is metered into a circulating stream of the water.
• the concentrate may be metered into the stream of water circulated between the cooling tower and heat exchanger(s) for which it provides cooling.
• the concentrate may be continuously or intermittently withdrawn from the pool and circulated through a brominator to which the concentrate is added.
• the concentrate may be diluted with water before addition to the body of water to be treated.
• the concentrate In the case of swimming pool treatment, the concentrate should be added in a proportion sufficient to kill bacteria in the circulating water. This may also be done in the case of cooling tower water.
• cooling tower water is treated with only enough of the bromine concentrate to contain the growth of the microorganisms, but not.enough to kill them. This method provides savings in the consumption of bromine, and minimizes corrosion to cooling tower components, piping and heat exchangers which utilize the cooling tower water.
• the concentrate is metered into the cooling tower basin using a positive displacement pump, e.g., a diaphragm pump.
• a peristaltic pump is most preferred because it is self priming and not subject to back siphoning.
• TRO total residual oxidant
• Precursor compositions were prepared by adding a 48% HBr solution and a 46% NaBr solution to water. Liquid bromine was added to the precursor solution to produce acidic concentrates containing 34% by weight equivalent molecular bromine. Satisfactory solutions were prepared from the proportions of water, HBr solution, NaBr solution and liquid bromine set forth in Table 1.
• acidic concentratres containing 34% by weight equivalent molecular bromine were prepared from water, a 46% by weight NaBr solution, and a 37% by weight HCl solution. Satisfactory compositions were prepared from the proportions set forth in Table 2.
• compositions were prepared from CaBr 2 , Br 2 , methanol, either HBr or HCl and, optionally, water. Satisfactory compositions were prepared from the proportions set forth in Table 4.
• Acidic concentrates were prepared from water or organic solvent, 46% by weight NaBr solution, 48% HBr solution, and liquid bromine. NaBr and HBr solution were added to the water or organic solvent, and liquid bromine was added at a modest rate to the precursor mixture. The mixture was stirred constantly but not too vigorously during the addition of Br .
• Four separate concentrates were prepared, each of which was a stable, clear liquid. The partial vapor pressures were measured 24 hours after the concentrates were formulated. The compositions of these concentrates, their bromine partial vapor pressures and the thermodynamic crystallization temperatures are set forth in Table 5.
• Example 4 The four concentrates of Example 4 were tested as reagents for recovery of gold from a refractory gold concentrate sample. The conditions and results of these tests are set forth in Tables 6-9. Table 6
• Example 4 a concentrate was prepared having the formulation of Composition #4 of Table 4 (Example 4) .
• the effectiveness of this composition for recovery of gold from ore was tested using a rotating disk technique, and also using the simulated batch technique as generally described in Example 4.
• the rotating disk test was conducted using a Pine Instrument model AFASR Rotator having a gold disk electrode.
• the parameters of the experiment were:
• the rotating disk experiment was initiated by the introduction of the gold disk electrode, while rotating, into the solution. Samples of the solution were withdrawn at 5 minute intervals for gold analysis, pH and temperature being recorded.
• compositions were prepared having the formulations indicated in Table 10. The bromine partial vapor pressure and initial crystallization temperature were determined for each of these compositions. These data are also recorded in Table 10.
• Table 11 Set forth in Table 11 are the NaBr/HBr ratio, Br 2 content and bromine partial vapor pressure of formulations F, G, H, M, N, and O of Table 10.
• Formulations G and H were prepared by adding bromine to formulation F.
• Each of formulations F through H have an NaBr/HBr weight ratio of 0.31 but vary in bromine content. It will be noted that the bromine partial vapor pressure is 40 mm Hg at a bromine content of 32.1% and a Br ⁇ /Br 2 weight ratio of 0.9.
• compositions M, N and O which have an NaBr/HBr weight ratio of only 0.17, appear to exhibit lower vapor pressures for comparable combinations of Br ⁇ /Br 2 ratio and Br 2 content.
• compositions of the invention have an NaBr/HBr ratio of less than 0.25, preferably, less than about 0.2, with a Br ⁇ /Br 2 weight ratio of at least about 1.0 and a bromine content of at least about 30% by weight.
• compositions of Table 10 were tested for recovery of gold from ore concentrates, and each was found to be effective for that purpose.
• Acidic bromine concentrates were prepared having the compositions set forth in Table 12. Measurements were made of Br 2 partial pressure and other parameters. These are also set forth in Table 12. The compositions of this table are effective for precious metal recovery and industrial water treatment.
• Cooling tower water was treated with a concentrate comparable to that of the first column of Table 12 (Example 8) .
• the concentrate was delivered into the basin of a cooling tower.
• Two methods were employed to determine the most efficient delivery of the product. The first method was simply letting the product drip into the water from the end of tubing attached to the discharge side of the pump. The feed rate was calculated by measuring the volume pumped into a graduated cylinder over a 1 minute time interval. The last 1 foot of tubing was placed horizontal to the surface of the water about 1.5 feet high. In the second method, the end of the discharge tubing was below the surface of the water.
• the feed rate was calculated in the same manner as the first method, but for this method a larger stroke size and frequency in the pump was used to inhibit back siphoning. The only indication of proper pump action was the presence of a brown cloud in the water when the pump was activated.
• the total residual oxidant (TRO) sample site was approximately at the turning point for the water before it is routed back to the tower.
• the TRO was determined by a Hach Cl-17 Chlorine Analyzer.
• the analyzer employs the DPD colorimetric method, by which the analyzer compares the optical absorbance of the raw water with the optical absorbance of the water with the DPD reagents. The difference is used to calculated the TRO in ppm as Cl 2 .
• the optical frequency used for this method was 510 nm.
• the Cl-17 had a LED display to two decimal points for recording immediate data, and also a chart recorder for obtaining overnight data.
• the analyzer was checked for accuracy by a hand-held DPD colorimeter (colorwheel)
• Selecticult-TTC (Scott Laboratories, Inc.) dipslides were used to determine the microbial density of the cooling tower water.
• the sample sites were in the basin of the cooling tower, above the basin, and at the normal site for operator water analysis.
• the dipslides were submerged in the water for approximately 1 second, then incubated at room temperature for 2-3 days before reading the slides.
• Table 13 lists all the cooling tower data generated during the tests. Samples of the cooling from water were analyzed for calcium concentration, chlorine residual, and pH. All readings for the week of the tests showed no significant changes in concentration or level.
• Table 14 is a listing of the data generated on second day of the tests.
• the data include time, air temperature, TRO, volumetric feed rate of CN-1767, feed method, pump setting, and microbial density.
• the initial microbial density was approximately 10 ⁇ organisms/mL.
• the pump stroke size was set at the smallest setting and the frequency set at 25 strokes per minute (spm) (approximate).
• the TRO was recorded every hour, and at 14:45 the TRO stabilized at 0.27 ppm as Cl 2 .
• the feed rate was then increased to approximately 4.0 mL/minute by changing the pump frequency to 35 spm while maintaining the minimum stroke setting. During the next 15 hours, the average TRO was 0.44 ppm as Cl 2 .
• the TRO was 0.53 ppm as Cl 2 5 and the microbial density was ⁇ 10 3 organisms/mL.
• the feed method was changed to the submerged tubing method.
• the pump was set at a minimum stroke and the frequency at 25 spm.
• the TRO decreased to 0.16 ppm as Cl 2 so at 13:50, the pump settings were increased to 17 stroke/30 spm 0 frequency.
• the TRO was 0.35 ppm, which was higher than anticipated.
• the settings were then decreased to 18 stroke/25spm frequency, which was 2.0 mL/min.
• the TRO was 0.51 ppm as Cl 2 and the microbial density was ⁇ 10 3 organisms/ml. 0
• the pump settings were decreased to 18 stroke/20 spm frequency or 1.0 mL/min.
• the TRO dropped to 0.08 ppm as Cl 2 .
• Figure 5 shows the hourly TRO and the daily bacterial density. At the beginning of the trial, the cell density was 10 5 organisms/mL. As the TRO increased to 0.28 and 0.53 ppm as Cl 2 , the cell densities decreased to ⁇ 10 4 and ⁇ 10 3 organisms/ml, respectively.
• the two feed styles used are labeled "DRIP IN” and "SUBMERGED” as described above.
• the "DRIP IN” style was used first at a feed rate of 2.0 mL/min until the TRO leveled out at 0.28 ppm as Cl 2 .
• the feed rate was increased to 4.0 mL/min, and the TRO leveled out around 0.53 ppm as Cl 2 .
• the feed style was changed to the "SUBMERGED” style and for 2.0 mL/min.
• the TRO dropped to 0.16 ppm as Cl 2 apparently because the product was siphoning back into the 5 gallon bucket.
• the pump settings were changed from minimum stroke/25 spm frequency to 18 stroke/30 spm frequency, this limited the back siphoning and the TRO increased to about 0.50 ppm as Cl .
• the feed rate was decreased to 1.0 ml/min, and the TRO decreased to about 0.28 ppm as Cl 2 dropped to 0.10 ppm as Cl 2 at the beginning of the work day.
• the pump was inspected.
• the PVC head was scored on the inside, but the Teflon diaphragm was not even stained.
• the inlet and out-flow valves on the pump were stained, but not rendered functionless.
• the Viton tubing used with the pump showed excellent compatibility.

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• 1992
  • 1992-03-17 AU AU19016/92A patent/AU665197B2/en not_active Ceased
  • 1992-03-17 EP EP92911839A patent/EP0580780A1/en not_active Withdrawn
  • 1992-03-17 FI FI934431A patent/FI934431L/fi not_active Application Discontinuation
  • 1992-03-17 JP JP4510845A patent/JPH06509052A/ja active Pending
  • 1992-03-17 CA CA002107895A patent/CA2107895A1/en not_active Abandoned
  • 1992-03-17 WO PCT/US1992/002128 patent/WO1992018422A1/en not_active Application Discontinuation
  • 1992-03-17 KR KR1019930703116A patent/KR970010335B1/ko not_active Expired - Fee Related
  • 1992-03-19 IL IL101292A patent/IL101292A0/xx unknown
  • 1992-03-24 ZA ZA922146A patent/ZA922146B/xx unknown
  • 1992-04-08 IE IE111492A patent/IE921114A1/en not_active Application Discontinuation
  • 1992-04-08 MX MX9201613A patent/MX9201613A/es unknown
• 1993
  • 1993-10-11 NO NO933663A patent/NO933663L/no unknown

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