Patent application title: USE OF OXYGENATED OR POLYOXYGENATED WEAK ACIDS, OR MINERALS, COMPOUNDS OR DERIVATIVES THAT GENERATE SAME, IN COPPER ELECTROWINNING PROCESSES IN CATHODES OR ANODES OF ELECTROLYTIC CELLS, ORIGINATING FROM THE LEACHING OF A COPPER MINERAL
Inventors:
IPC8 Class: AC25C112FI
USPC Class:
205101
Class name: Electrolytic coating (process, composition and method of preparing composition) treating process fluid by means other than agitation or heating or cooling regenerating or maintaining electrolyte (e.g., self-regulating bath, etc.)
Publication date: 2016-07-07
Patent application number: 20160194771
Abstract:
The invention relates to the use of oxygenated or polyoxygenated weak
acids, or minerals or compounds that generate the same to stabilize and
buffer the electrolyte solution, thereby improving its conductivity,
and/or catalytically promoting copper electrodeposition.
Additionally, a copper electrowinning procedure is described that
comprises the addition of a necessary quantity of an oxygenated or
polyoxygenated weak acid, or mineral or compound that generates the same,
to the electrodeposition process; wherein the necessary quantity of weak
acid will depend on the characteristics of the mineral, the electrolyte
solution, and the current density used.
In the invention, the addition of oxygenated or polyoxygenated weak
acids, minerals, compounds or derivatives that generate the same to the
charged electrolytes coming from the solvent extraction phase and
entering the electrowinning (EW) stage serves the purpose of homogenizing
the current density within the electrolytic cell, resulting in increased
electrical energy consumption efficiency versus the amount of copper
deposited.Claims:
1. Use of oxygenated or polyoxygenated weak acids, or minerals or
compounds that generate the same COMPRISING stabilization and buffering
of the electrolyte solution, thereby improving its conductivity, and/or
catalytically promoting copper electrodeposition, even in processes with
high current intensity and high speed cation deposition
2. Use of oxygenated or polyoxygenated weak acids, or minerals or compounds that generate the same in a copper electrodeposition process of claim 1 COMPRISING a weak acid that can be, among others, boric acid or phosphoric acid.
3. Use of oxygenated or polyoxygenated weak acids, or minerals or compounds that generate the same in a copper electrodeposition process of claim 1 COMPRISING a weak acid that is preferably boric acid, also called orthoboric acid.
4. Use of oxygenated or polyoxygenated weak acids, or minerals or compounds that generate the same in a copper electrodeposition process of claim 1 COMPRISING a weak acid that is preferably phosphoric acid, also called orthophosphoric acid.
5. Use of oxygenated or polyoxygenated weak acids, or minerals or compounds that generate the same in a copper electrodeposition process of claim 1 COMPRISING a material containing boron or phosphorus.
6. Use of oxygenated or polyoxygenated weak acids, or minerals or compounds that generate the same in a copper electrodeposition process of claim 1 COMPRISING a material containing boron.
7. Use of oxygenated or polyoxygenated weak acids, or minerals or compounds that generate the same in a copper electrodeposition process of claim 1 COMPRISING a material containing phosphorus.
8. Use of oxygenated or polyoxygenated weak acids, or minerals or compounds that generate the same in a copper electrodeposition process of claim 1 COMPRISING the mineral boron that can be selected, without limitation, from ulexite, colemanite, kernite, pandermite, bakerite, datolite, elbaite, admontite, aksaite, ameghinite, ammonioborite, aristarainite, avogadrite, axinite, bandylite, barberiite, behierite, berborite, biringuccite, boracite, boralsilite, borax, borazon, borcarite, bormuscovite, cahnite, calciborite, carboborite, chambersite, charlesite, congolite, danburite, datolite, diomignite, dravite, dumortierite, eremeevite, ericaite, ezcurrite, fabianite, ferruccite, flolovite, fluoborite, foitite, frolovite, garrelsite, gaudefroyite, ginorite, gowerite, halurgite, hambergite, heidornite, henmilite, hexahydroborite, hydroboracite, hydrochlorborite, hilgardite, holtite, howlite, hulsite, hungchaoite, inderborite, inderite, inyoite, jeremejevite, jimboite, kalborsite, karlite, katoite, kornerupine, kotoite, kurnakovite, lardarellite, ludwigite, lueneburgite, luidwigite, manandonite, mcallisterite, metaborite, meyerhofferite, moydite, nasinite, nifontovite, nobleite, nordenskjoeldine, olenite, oyelite, painite, pentahydroborate, pinnoite, povondraite, preobrazhenskite, priceite, pringleite, probertite, reedmergnerite, rhodozite, rivadavite, roweite, sabinite, sakhite, santite, sassolite, sborgite, schorl, seamanite, searlesite, serendibite, sibirskite, sinhalite, solongoite, spurrite, stillwellite, strontioborite, studenitsite, sturmanite, suanite, sulfoborite, sussexite, szaibelyite, teepleite, tertschite, tincalconite, tunellite, tusionite, tyretskite, uralborite, veatchite, boric vesuvianite, vistepite, volkovskite, vonsenite, warwickite, wawayandaite, wighmanite, wiluite, and wiserite, among others.
9. Use of oxygenated or polyoxygenated weak acids, or minerals or compounds that generate the same in a copper electrodeposition process of claim 1 COMPRISING the mineral phosphorus that can be selected, without limitation, from aheylite, aldermanite, alforsite, alluaudite, althausite, amblygonite, anapaite, apatite, arctite, ardealite, arupite, augelite, autunite, babefphite, barbosalite, baricite, barringerite, bassetite, bauxite, bearthite, belovite, benauite, beraunite, berlinite, bermanite, bertossaite, beryllonite, beusite, biphosphamite, bobierrite, boggildite, bonshtedtite, brabantite, bradleyite, brazilianite, brianite, britholite, brushite, buchwaldite, cacoxenite, canaphite, cassidyite, chalcosiderite, cheralite, churchite, chlorapatite, coffinite, collinsite, coeruleolactite, corkite, cornetite, crandallite, crawfordite, curetonite, cyrilovite, diadochite, dittmarite, dorfmanite, dufrenite, dumontite, earlshannonite, ehrleite, eosphorite, fairfieldite, farringtonite, florencite, fluellite, fluorapatite, fluorellestadite, foggite, fornacite, francoanellite, fransoletite, frondelite, furongite, gainesite, galileiite, gatehouseite, gatumbaite, giniite, girvasite, glucine, gorceixite, gordonite, goyazite, graftonite, grattarolaite, grayite, hentschelite, herderite, heterosite, hinsdalite, holtedahlite, hopeite, hotsonite, hureaulite, hurlbutite, hydroxylapatite, hydroxylherderite, hydroxyl-piromorphite, isokite, jagowerite, kaluginite, kidwellite, kingite, kingsmountite, kintoreite, kleemanite, kolbeckite, koninckite, kosnarite, kovdorskite, kribergite, kryzhanovskite, kuksite, lacroixite, landesite, laubmanite, laueite, lazulite, lehnerite, lermontovite, leucophosphite, libethenite, likasite, lipscombite, liroconite, lithiophilite, lithiophosphatite, lithiophosphate, lomonosovite, ludlamite, luneburgite, magniotriplite, mahlmoodite, mangangordonite, maricite, matulaite, metaankoleite, metaswitzerite, metatorbenite, metavariscite, metavauxite, mimetite, mitridatite, monazite, monetite, montebrasite, montgomerite, moraesite, moreauite, morinite, mundite, nabaphite, nafedovite, nalipoite, nasicon, nastrophite, natrophilite, natrophosphato, nefedovite, newberyite, niahite, ningyoite, nissonite, olympite, overite, oxyapatite, parafransoletite, parahopeite, paravauxite, parsonite, paulkellerite, petersite, phosphammite, phosphoellenbergerite, phosphoferrite, phosphofibrite, phosphophyllite, phosphorroslerite, phosphosiderite, phosphovanadylite, phosphuranylite, phosinaite, phuralumite, phurcalite, pyromorphite, pyrophosphite, plumbogummite, pretulite, pseudolaueite, pseudomalachite, purpurite, reichenbachite, robertsite, rockbridgeite, rodolicoite, sabugalite, saleeite, sampleite, satterlyite, scholzite, schreibersite, scorzalite, seamanite, segelerite, senegalite, sengalite, sidorenkite, sieleckiite, sigloite, silicocarnotite, spencerite, stercorite, stewartite, strengite, strunzite, struvite, svanbergite, switzerite, taranakite, tarbuttite, tavorite, threadgoldite, tinsleyite, tinticite, triangulite, triphylite, triplite, triploidite, trolleite, turquoise, uralolite, ushkovite, vanmeerscheite, variscite, varulite, vashegyite, vayrynenite, veszelyite, viitaniemiite, vitusita, vivianite, vochtenite, voggite, vuonnemite, vyacheslavite, wagnerite, wardite, wavellite, whitmoreite, wolfeite, woodhouseite, wooldridgeite, ximengite, zairite, zapatalite, and zodacite, among others.
10. Use of oxygenated or polyoxygenated weak acids, or minerals or compounds that generate the same in a copper electrodeposition process of claim 1 COMPRISING a compound that can be, among others, a boron compound.
11. Use of oxygenated or polyoxygenated weak acids, or minerals or compounds that generate the same in a copper electrodeposition process of claim 1 COMPRISING a compound that can be, among others, a phosphorus compound.
12. Use of oxygenated or polyoxygenated weak acids, or minerals or compounds that generate the same in a copper electrodeposition process of claim 10 COMPRISING a compound that is a boron compound, selected preferably, without limitation, from borax, borates, and boranes, among others.
13. Use of oxygenated or polyoxygenated weak acids, or minerals or compounds that generate the same in a copper electrodeposition of claim 11 COMPRISING a compound that is a phosphorous compound, preferably selected, without limitation, from phosphates, phosphonates, phosphoranes, phosphides, sodium hypophosphite, phosphine oxide, phosphorus pentafluoride, phosphorus trichloride, hexafluorophosphoric acid, and phosphorus (III) and (V) oxide, among others.
14. Use of oxygenated or polyoxygenated weak acids, or minerals or compounds that generate the same in a copper electrodeposition process of claim 1 COMPRISING improved current consumption efficiency and increased copper recovery from the electrolyte solution.
15. A copper electrowinning procedure COMPRISING: Addition of a necessary quantity of an oxygenated or polyoxygenated weak acid, or a compound or a mineral that generate the same in said copper electrodeposition process where the necessary quantity of weak acid will depend on the characteristics of the mineral, the electrolyte solution, and the current density used.
16. A copper electrowinning procedure of claim 14 COMPRISING the addition of an oxygenated or polyoxygenated weak acid, preferably, to said electrodeposition chamber.
17. A copper electrowinning procedure of claim 15 COMPRISING said weak acid, preferably, boric acid or phosphoric acid.
18. A copper electrowinning procedure of claim 14 COMPRISING said mineral added to said electrodeposition process.
19. A copper electrowinning procedure of claim 17 COMPRISING said mineral, preferably, a boron or phosphorus mineral.
20. A copper electrowinning procedure of claim 17 COMPRISING said compound, preferably, a boron or phosphorus compound.
21. A copper electrowinning procedure of claim 17 COMPRISING said compound, preferably selected from borax, borates, and boranes, among others.
22. A copper electrowinning procedure of claim 17 COMPRISING said compound, preferably selected from borax.
23. A copper electrowinning procedure of claim 17 COMPRISING said compound, preferably selected from phosphates, phosphonates, phosphoranes, phosphites, phosphides, sodium hypophosphite, phosphine oxide, phosphorus pentafluoride, phosphorus trichloride, hexafluorophosphoric acid, and phosphorus (III) and (V) oxide, among others.
24. Use of oxygenated or polyoxygenated weak acids, or minerals or compounds that generate the same in copper electrowinning of claim 1 COMPRISING said acid having a dissociation constant that varies between 1.80.times.10.sup.-16 and 55.50.
Description:
[0001] The invention relates to the use of oxygenated or polyoxygenated
weak acids, minerals, compounds or derivatives that generate the same, at
any degree of concentration, in copper electrowinning processes in
cathodes or anodes of electrolytic cells from an electrolyte charged with
copper sulfate originating from the leaching of a copper mineral.
[0002] The invention relates to the addition of oxygenated or polyoxygenated weak acids, minerals, compounds or derivatives that generate the same, to the charged electrolytes coming from the solvent extraction phase and entering the electrowinning (EW) stage in order to homogenize the current density within the electrolytic cell, resulting in increased electrical energy consumption efficiency versus the amount of copper deposited.
[0003] Electrowinning (EW) or electrodeposition is one of the processes to recover-in pure form and selectively-metals that are in solution, and consists of recovering the metal from a properly conditioned leach solution (electrolyte solution), and depositing it on a cathode using an electrolysis process.
[0004] In the copper production process, electrowinning is a highly relevant stage, as copper for industrial use requires a purity grade established by electrolytic copper standards.
[0005] In the electrowinning (EW) process, a direct electric current of low voltage and high intensity circulates through the electrolytic solution between an anode, the solution itself, and a cathode. In this way, the metal ions of interest (cations) are attracted to the cathode (negatively charged pole), where they are deposited, and the impurities are dissolved in the electrolyte solution, or are precipitated as residue or anode slimes.
[0006] Through the electrowinning process, it is possible to recover metals-such as copper, gold, and silver-from leachable resources that would otherwise be unfeasible.
[0007] The processes of purification and concentration of leach solutions, such as solvent extraction (SX) for copper and activated carbon (AC) for gold, have broadened the scope of application of the electrowinning process to recover these metals. So much so that some metals, like zinc, rely almost exclusively on electrowinning to achieve a recovery that is economically viable.
[0008] The electrowinning process is also a very competitive alternative to treat copper-cobalt and nickel-cobalt combined minerals.
[0009] To perform the electrowinning process, electrolytic cells with electric circuitry are required to circulate a direct electric current of low voltage and high intensity.
[0010] So that the process is carried out efficiently, the following aspects must be considered:
[0011] a) Circuit Configuration: To provide the direct current required by the electrolysis process, current rectifier equipment is used to maintain constant electrical flow characteristics. The technology of rectifiers has evolved, and currently uses transistorized transformer rectifiers. The filter requirements for harmonic current control currently constitute the major factors in the increasing costs of these rectifiers. Filters are used to achieve a better effect with two units (electrowinning cells), instead of one.
[0012] b) Electrical connection characteristics: Electrowinning cell electrical connections are very simple, since they attempt to reduce the distances from rectifiers in direct current and high voltage.
[0013] The energy requirements, particularly for electrical current, necessary for the electrowinning process are significantly high compared to other types of industries. The invention is directed to make electrical energy consumption in copper mining more efficient, particularly in the electrowinning process, thereby solving a problem widely recognized in the industry.
[0014] Metal electrowinning is governed by Faraday's Law, which states that:
[0015] The amount of chemical change produced by an electrical current, i.e., the dissolved or deposited amount of a substance, is proportional to the amount of electricity passed.
[0016] The amounts of various substances deposited or dissolved by the same amount of electricity are proportional to their equivalent chemical weights.
[0017] Faraday's Law states:
md = P at .times. i cell .times. A t .times. t .times. .eta. c z .times. F = Q C i - C f ##EQU00001##
[0018] Where:
[0019] md=mass deposited [mass/time]
[0020] P.sub.at=molecular weight of the element in study
[0021] i.sub.cell=current density of the cell
[0022] A.sub.t=total area exposed to deposition
[0023] t=exposure time
[0024] .eta..sub.c=current efficiency (90-92%)
[0025] Z=number of electrons exchanged in the deposition reaction.
[0026] F=Faraday constant (96.500[c/g-eq]
[0027] Q=solution volumetric flow
[0028] [C.sub.i-C.sub.f]=change in concentration of the element of interest in the electrowinning stage.
[0029] The role played by oxygenated or polyoxygenated weak acids-such as boric acid or orthophosphoric acid-, minerals, compounds or derivatives of the same, at any degree of concentration in the electrowinning processes of metal ions in cathodes has a relationship with stabilizing and buffering the electrolyte solution, improving its conductivity, especially in near-surface electrode layers, as well as catalytically promoting electrodeposition, even in processes with high current intensity and high speed cation deposition.
[0030] Additionally, it controls and stabilizes the system's hydrogen ion discharge, as well as the homogenous distribution of current in the electrolytic cell, making current use more efficient.
[0031] The invention relates to the use of oxygenated or polyoxygenated weak acids, preferably, but not limited to boric acid and orthophosphoric acid in the copper electrowinning process in order to homogenize the current density in the electrolytic cell, resulting in increased electrical energy consumption efficiency versus the amount of copper deposited.
[0032] The invention also relates to a copper electrowinning process using oxygenated or polyoxygenated weak acid, or a mineral or compound that generates the same on the spot, whereby increased electrical energy consumption efficiency versus the amount of copper deposited is achieved.
[0033] In the invention, boric acid refers to H.sub.3BO.sub.3 (trioxoboric (III) acid, B(OH).sub.3, also called orthoboric acid), or their derivatives. Boron minerals refers, without limitation, to ulexite, colemanite, kernite, pandermite, bakerite, datolite, elbaite, admontite, aksaite, ameghinite, ammonioborite, aristarainite, avogadrite, axinite, bandylite, barberiite, behierite, berborite, biringuccite, boracite, boralsilite, borax, borazon, borcarite, bormuscovite, cahnite, calciborite, carboborite, chambersite, charlesite, congolite, danburite, datolite, diomignite, dravite, dumortierite, eremeevite, ericaite, ezcurrite, fabianite, ferruccite, flolovite, fluoborite, foitite, frolovite, garrelsite, gaudefroyite, ginorite, gowerite, halurgite, hambergite, heidornite, henmilite, hexahydroborite, hydroboracite, hydrochlorborite, hilgardite, holtite, howlite, hulsite, hungchaoite, inderborite, inderite, inyoite, jeremejevite, jimboite, kalborsite, karlite, katoite, kornerupine, kotoite, kurnakovite, lardarellite, ludwigite, lueneburgite, luidwigite, manandonite, mcallisterite, metaborite, meyerhofferite, moydite, nasinite, nifontovite, nobleite, nordenskjoeldine, olenite, oyelite, painite, pentahydroborate, pinnoite, povondraite, preobrazhenskite, priceite, pringleite, probertite, reedmergnerite, rhodozite, rivadavite, roweite, sabinite, sakhite, santite, sassolite, sborgite, schorl, seamanite, searlesite, serendibite, sibirskite, sinhalite, solongoite, spurrite, stillwellite, strontioborite, studenitsite, sturmanite, suanite, sulfoborite, sussexite, szaibelyite, teepleite, tertschite, tincalconite, tunellite, tusionite, tyretskite, uralborite, veatchite, boric vesuvianite, vistepite, volkovskite, vonsenite, warwickite, wawayandaite, wighmanite, wiluite, and wiserite, among others.
[0034] Boron compounds refers, without limitation, to borax (Na2B4O7.10H.sub.2O or pentahydrate, sodium borate, sodium tetraborate, sodium heptaoxotetraborate), borates (compounds that contain boron oxoanions, with boron in oxidation state +3), boranes (boron hydrides).
[0035] In the invention, phosphoric acid refers to H.sub.3PO.sub.4. (sometimes called orthophosphoric acid), copper compounds refers, without limitation, to phosphates, phosphonates, phosphoranes, phosphides, sodium hypophosphite, phosphine oxide, phosphorus pentafluoride, phosphorus trichloride, hexafluorophosphoric acid, phosphorus (III) and (V) oxide, among others. Phosphorus minerals refers, without limitation, to phosphoric rocks, such as, for example, lignite, andalusite, aheylite, aldermanite, alforsite, alluaudite, althausite, amblygonite, anapaite, apatite, arctite, ardealite, arupite, augelite, autunite, babefphite, barbosalite, baricite, barringerite, bassetite, bauxite, bearthite, belovite, benauite, beraunite, berlinite, bermanite, bertossaite, beryllonite, beusite, biphosphamite, bobierrite, boggildite, bonshtedtite, brabantite, bradleyite, brazilianite, brianite, britholite, Brushite, buchwaldite, cacoxenite, canaphite, cassidyite, chalcosiderite, cheralite, churchite, chlorapatite, coffinite, collinsite, coeruleolactite, corkite, cornetite, crandallite, crawfordite, curetonite, cyrilovite, diadochite, dittmarite, dorfmanite, dufrenite, dumontite, earlshannonite, ehrleite, eosphorite, fairfieldite, farringtonite, florencite, fluellite, fluorapatite, fluorellestadite, foggite, fornacite, francoanellite, fransoletite, frondelite, furongite, gainesite, galileiite, gatehouseite, gatumbaite, giniite, girvasite, glucine, gorceixite, gordonite, goyazite, graftonite, grattarolaite, grayite, hentschelite, herderite, heterosite, hinsdalite, holtedahlite, hopeite, hotsonite, hureaulite, hurlbutite, hydroxylapatite, hydroxylherderite, hydroxyl-piromorphite, isokite, jagowerite, kaluginite, kidwellite, kingite, kingsmountite, kintoreite, kleemanite, kolbeckite, koninckite, kosnarite, kovdorskite, kribergite, kryzhanovskite, kuksite, lacroixite, landesite, laubmanite, laueite, lazulite, lehnerite, lermontovite, leucophosphite, libethenite, likasite, lipscombite, liroconite, lithiophilite, lithiophosphatite, lithiophosphate, lomonosovite, ludlamite, luneburgite, magniotriplite, mahlmoodite, mangangordonite, maricite, matulaite, metaankoleite, metaswitzerite, metatorbenite, metavariscite, metavauxite, mimetite, mitridatite, monazite, monetite, montebrasite, montgomerite, moraesite, moreauite, morinite, mundite, nabaphite, nafedovite, nalipoite, nasicon, nastrophite, natrophilite, natrophosphato, nefedovite, newberyite, niahite, ningyoite, nissonite, olympite, overite, oxyapatite, parafransoletite, parahopeite, paravauxite, parsonite, paulkellerite, petersite, phosphammite, phosphoellenbergerite, phosphoferrite, phosphofibrite, phosphophyllite, phosphorroslerite, phosphosiderite, phosphovanadylite, phosphuranylite, phosinaite, phuralumite, phurcalite, pyromorphite, pyrophosphite, plumbogummite, pretulite, pseudolaueite, pseudomalachite, purpurite, reichenbachite, robertsite, rockbridgeite, rodolicoite, sabugalite, saleeite, sampleite, satterlyite, scholzite, schreibersite, scorzalite, seamanite, segelerite, senegalite, sengalite, sidorenkite, sieleckiite, sigloite, silicocarnotite, spencerite, stercorite, stewartite, strengite, strunzite, struvite, svanbergite, switzerite, taranakite, tarbuttite tavorite, threadgoldite, tinsleyite, tinticite, triangulite, triphylite, triplite, triploidite, trolleite, turquoise, uralolite, ushkovite, vanmeerscheite, variscite, varulite, vashegyite, vayrynenite, veszelyite, viitaniemiite, vitusita, vivianite, vochtenite, voggite, vuonnemite, vyacheslavite, wagnerite, wardite, wavellite, whitmoreite, wolfeite, woodhouseite, wooldridgeite, ximengite, zairite, zapatalite, zodacite.
[0036] In general, the solutions proposed by the industry to reduce the amount of energy (such as electric current) are aimed at physical changes in the electrowinning process. However, the use of weak acids, such as boric or phosphoric acid, to stabilize and buffer the electrolyte solution to improve its conductivity has not been described.
[0037] In U.S. Pat. No. 5,882,502 an electrochemical system that allows metals from other compounds to be separated and recovered through a chemical cell system consisting of an anode and a cathode with separate sections connected by a conductor is presented. Herein an alkaline electrolyte, consisting of ammonium, ammonium sulfate, or ammonium chloride, the metal ion to separate, and a halogen ion, such as bromine or a boron compound, as a reaction catalyst, is described. The extraction is from metal oxides, particularly nickel, cobalt, and copper.
[0038] However, in U.S. Pat. No. 5,882,502, no reference is made to particular boron compounds, let alone to the possibility of the presence of a weak acid such as boric or phosphoric acid, nor specific compounds that can be used. As a result, the choice of a weak acid, or a mineral that generates the same is not made clearly therein.
[0039] Borate compounds are used in the non-metallic mining industry. One of the main boron compound minerals is ulexite (NaCaB.sub.5O.sub.9.8H.sub.2O); this naturally-occurring borate is used in non-metallic mining to produce or extract boric acid, borax, and other derivatives.
[0040] The use of ulexite has been described on the industrial manufacturing level in agriculture and forestry as fertilizer material.
[0041] Other boron derivatives, such as borax and boric acid have been used as fertilizers and preservatives in the food industry.
[0042] Additionally, borax, which is a soluble borate, is used in mining together with ammonium as an iron and steel smelting mixture due to its ability to reduce the mixture melting point and thereby eliminate the iron oxide contaminant from the system. Additionally, the use of borax has been described in the smelting of gold and silver jewelry.
[0043] Boric acid, as such, is used in the manufacture of fiberglass, fire retardants, borosilicate glass, soaps, detergents, and certain pharmaceutical products. With regard to boric acid, it is used as an antiseptic, an antibacterial, to formulate insecticides, as well as in buffer solution compounds and as a food preservative. Industrially, boric acid is recognized as raw material in the manufacture of the monofibers that make up textile fiberglass, which is used as the structural base of plastics and circuitry. Additionally, the use of boric acid has been described as a manufacture material for dynamite and weapons of mass destruction.
[0044] With regard to another weak acid that is particularly relevant to the invention, such as orthophosphoric acid and its derivatives, the use of polyphosphates due to their high solubility in concentrated liquid fertilizers has been specified, as well as their mining and industrial use as metal chelating agents. Additionally, the use of sodium and calcium polyphosphates in the food industry and in detergent preparation has been described. Other phosphates, in the form of ammonium salts are widely used as raw material in fertilizer manufacturing. In the mining and jewelry industry, phosphate compounds, such as manganese phosphate, are used to prevent metal corrosion and to improve lubrication. Similarly, zinc phosphate is used to prevent metal oxidation. Finally, phosphoric acid, as such, is used as an ingredient in soft drinks, as a water softener, in fertilizer and detergent production, and in the mining industry as an anticorrosive and antireduction substance, and as an agent to prevent gas evaporation.
[0045] In no case is the traditional use of oxygenated and polyoxygenated weak acids consistent with the proposed use and procedure of the invention.
[0046] Below are examples which illustrate the significant improvement that the use of oxygenated or polyoxygenated weak acids, particularly boric acid, provides in the electrowinning process.
EXAMPLE 1
Effect of the Addition of Boric Acid in the Copper Electrowinning Stage in the Metal Leaching Process
[0047] In this example, the effect of the addition of boric acid in the copper electrowinning process is illustrated, in contrast to a test without the addition of the acid. For the electrowinning, a synthetic electrolyte solution (10 L) composed of copper pentahydrate sulfate, water, and sulfuric acid (180 g/L) was prepared. Batch tests were prepared (5 batches), testing two systems with different current densities (320 and 390 A/m.sup.2,) simultaneously, with boric acid incorporated and without adding boric acid to the cell. For each system, the voltage and amperage were set at 2V and 2 A, respectively, allowing for continuous functioning for 10 hours at room temperature. Finally, to determine the amount of copper electrodeposited on the cathode, the initial mass of the electrode was subtracted from the final mass of the electrode.
[0048] The results indicate that the proposed addition of boric acid by the inventor progressively improves the electrowinning current efficiency in comparison to the electrolyte solution without the addition of the acid (FIG. 1). Additionally, electrowinning parameters in systems with different current densities were measured, both with and without the addition of boric acid during the process. As a result, an increase in the copper mass deposited experimentally by adding boric acid to the system was observed, independent of the current density applied. Thus, in the system with a current density of 320 A/m.sup.2, under normal conditions the deposited mass was observed to be 21.83 g, while the addition of boric acid increased the amount to 22.65 g (Table 1). When the cathode was operated at a current density of 390 A/m.sup.2, a copper deposit of 2.4416 g/h was obtained in the normal system without boric acid, in contrast to the 2.4896 g/h deposited with the addition of boric acid to the cathode (Table 2).
TABLE-US-00001 TABLE 1 Copper electrowinning parameters in cathodes with and without boric acid at a current density of 320 A/m.sup.2. Cathode without Cathode with Parameter boric acid boric acid Voltage 2.00 V 2.00 V Current density 320 A/m.sup.2 320 A/m.sup.2 Test time 10 hr 10 hr ER Cu Concentration 47.2 g/L 44.37 g/L EP Cu Concentration 41.31 g/L 38.45 g/L Theoretical mass of cathode 23.59 g 23.71 g according to Faraday's Law Experimental mass deposited 21.83 g 22.65 g Actual current efficiency 92.5% 95.5%
[0049] Where ER is electrolyte rich, and EP is electrolyte poor.
TABLE-US-00002 TABLE 2 Copper electrowinning parameters in cathodes with and without boric acid at a current density of 390 A/m.sup.2. Cathode without Cathode with Parameter boric acid boric acid Voltage 2.00 V 2.00 V Current density 390 A/m.sup.2 390 A/m.sup.2 Test time 10 hr 10 hr ER Cu Concentration 49.25 g/L 39.72 g/L EP Cu Concentration 41.47 g/L 32.09 g/L Theoretical mass of cathode 24.90 g 24.42 g according to Faraday's Law Experimental mass deposited 24.16 g 24.2 g Actual current efficiency 97.0% 99.1%
[0050] Where ER is electrolyte rich, and EP is electrolyte poor.
[0051] In Tables 1 and 2,
[0052] Copper experimental mass deposited=Final cathode mass-initial cathode mass.
[0053] The experimental deposited mass is also calculated as the difference between the copper concentration of the electrolyte rich solution and the electrolyte poor solution by using the following equation:
[0054] masa.sub.depositada=(Cu.sub.ER-Cu.sub.EP)*Q*t, where Cu.sub.ER: is the copper concentration in the electrolyte rich solution; Cu.sub.EP: is the copper concentration in the electrolyte poor solution; Q: electrolyte flow; t: exposure time
Current efficiency = .eta. = 100 * masa experimental masa teorica . ##EQU00002##
[0055] Where:
[0056] theoretical mass=m=I*t*eq/F, where m: electrochemically reactive mass; I: current intensity; t: time; F: Faraday constant; eq: equivalents, where eq=PM/Z.
EXAMPLE 2
Effect of the Addition of Orthophosphoric Acid in the Copper Electrowinning Stage in the Leaching Process.
[0057] Following the same protocol described in Example 1, but now using orthophosphoric acid in the copper electrowinning stage in the leaching process.
[0058] Below are the results obtained, which illustrate how a greater mass of copper deposited was obtained using this weak acid.
TABLE-US-00003 TABLE 3 Copper electrowinning parameters in cathodes without orthophosphoric acid and with the addition of different volumes of the acid at a current density of 320 A/m.sup.2. Cathode Cathode with without Cathode with ortho- orthophosphoric orthophosphoric phosphoric Parameter acid acid (10 mL) acid (20 mL) Voltage (V) 2 2 2 Current density 320 320 320 (A/m.sup.2) Test time (hr) 10 10 10 Theoretical mass of 23.59 23.29 23.29 cathode according to Faraday's Law (g) Experimental mass 21.83 23 23 deposited (g) Actual current 92.5 92.4656 98.7661 efficiency (%)
TABLE-US-00004 TABLE 4 Copper electrowinning parameters in cathodes without orthophosphoric acid and with the addition of different volumes of the acid at a current density of 390 A/m.sup.2. Cathode Cathode with without Cathode with ortho- orthophosphoric orthophosphoric phosphoric Parameter acid acid (10 mL) acid (20 mL) Voltage (V) 2 2 2 Current density 390 390 390 (A/m.sup.2) Test time (hr) 10 10 10 Theoretical mass of 24.90 24.86 25.43 cathode according to Faraday's Law (g) Experimental mass 24.16 24.82 25.28 deposited (g) Actual current 97.0 99.8545 99.4295 efficiency (%)
[0059] In Table 5, the effect of the addition of orthophosphoric acid on copper electrowinning current efficiency is described, and an increase in current efficiency by using orthophosphoric acid in the process can be seen.
TABLE-US-00005 TABLE 5 Effect of the addition of orthophosphoric acid in copper electrowinning current efficiency. Cathode with Cathode with Current Cathode without orthophosphoric orthophosphoric density orthophosphoric acid acid (A/m.sup.2) acid (10 mL) (20 mL) 320 92.5 A/m2 92.46 A/m2 98.76 A/m2 390 97.0 A/m2 99.85 A/m2 99.43 A/m2
FIGURE DESCRIPTION
[0060] FIG. 1. Effect of the addition of boric acid on current efficiency in copper electrodeposition tests. The axes indicate current efficiency (%) with respect to current density (A/m.sup.2) generated in the electrolyte solution with boric acid and without boric acid. Where the line marked with.cndot.corresponds to the electrolyte solution when boric acid is added to the system, and the line marked with X corresponds to the electrolyte solution without boric acid treatment.
[0061] FIG. 2. Effect of the addition of orthophosphoric acid on current efficiency in copper electrodeposition tests. The axes indicate current efficiency (%) with respect to current density (A/m.sup.2) generated in the electrolyte solution without orthophosphoric acid and with the addition of 10 and 20 mL of orthophosphoric acid. Where the line marked with.cndot.corresponds to the electrolyte solution without orthophosphoric treatment, the line marked with X corresponds to the test adding 10 mL of orthophosphoric acid, and the line marked with .box-solid. corresponds to the test adding 20 mL of orthophosphoric acid.
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