AU607523B2 - Metal value recovery - Google Patents

Description

607523

AUSTRALIA

Patents Act COMPLETWE SPECIFICATION

(ORIGINAL)

Class Int. Class Application Number: Lodged: Complete Specification Lodged: Accepted: Published: Priority Related Art: This document contains the amendments made under Section 49 and is correct for printing.

APPLICANT'S REFERENCE: ES-42 Name(s) of Applicant(s): Ensci, Inc Address(es) of Applicant(s): 6269 Variel, Suite

F,

Woodland 1ills, California, UNITED STATES OF AMERICA.

cucS Address for Ser'vice is: PHILLIPS OMONDE FITZPATRICK Patent and Trade Mark Attorneys 367 Collins Street Melbourne 3000 AUSTRALIA Complete Specification for the invention entitled: METAL VALVE RECWERY Our Ref 102407 POF Code: 70538/65478 The following statement is a full description of this invention, including the best method of performing it known to applicant(s).

6003q/1 -1 SES-42 RELATED APPLICATIONS This application is a cot 2 n'ation-i-part of copending application Serial No. ,130, filed January 20, 1987, and copending appl'ca-tion Serial No. 025,069, filed March 12, 1987.

Each I-these applications is hereby incorporated in its entirety eein/ by reforece.

BACKGROUND OF THE INVENTION This invention relates to a process for recovering at Lo least one metal, gold, silver, the platinum group metals and the like, from an ore containing reducible manganese and the metal. The invention also relkv es to a process for recovering at :least one metal, as noted above, from an ore containing metal sulfides and/or carbonaceous material and the metal to be recovered. In particular, the invention relakes to a process t 00 0o0oo° which involves processing a metal-containing ore so as to o facilitate the recovery of the metal from the ore.

o eo Reducible manganese-containing ores quite often contain °o 00 00ooo0 metal values which are difficult to recover because of the "locking" nature of the manganese in the ore. For example, the occurrence of manganese-locked silver ores has long been a 0000 0.o0 problem for ore processors. Conventional smelting can treat small, limited quantities of manganese-locked silver ores when processing conventional ores. The manganese must be properly slagged to prevent attack of the crucibles. This consumes silica, increases energy required, and contributes to metal loss in the slag. Manganese-locked silver ores may be leached with sodium cyanide to recover silver, but such recovery is often limited by the manganese content, Manganese in such ores "locks" the silver Zo in the ore by, for example, blocking access by the sodium cyanide solution to the silver-bearing or silvet minerals.

tj. la Metal sulfide-containing ores often contain metal values, such as gold, silver, the platinum group metals and the like, which are difficult to recover because of the "locking" nature of the metal sulfide in the ore. For example, the occurrence of insoluble metal sulfide-locked gold ores has long been a problem for ore processoi:s. In addition, electrumcontaining ores are also difficult to process for the recovery of precious metal values.

Use of sodium cyanide to remove silver from manganeseto locked silver ores or to remove gold from such gold metal sulfide-containing ores is usually uneconomical. Moreover, stringent air pollution control regulations and low metal prices o0000o have forced smelters to shut down or select ores from which metal 0 0 0000 ooo values can be recovered relatively easily. Ores which include o° "locking" manganese containing about 0.5% to about 35% by 0000 weight of manganese) ire often considered marginal and may not be 0000 0o000 processed. AJ, -752,32 4171 Commonly assigned U.S. patent A-a 0 00 -3 -8-58--0-6 and_. 858,369, filed April 30, 1986, disclose processes for the recovery of various metal values, silver, gold, and the a 00 0 00 °platinum group metal, involving the use of reducible manganese 00000 omponets.pfterts o° components, These l-aplaions- also include a more detailed 00 discussion of certain prior art references. Also, commnly- 0 00 o o sd U.S. I Pa t Apa-i,-a ,er-l-l-No-i-l 246, fi-l -Nveber 17, -3&8-6-)-d.igslo-sQs-a-p-oses- slfc- -o er-t-- e-0- feeaGl--pGeeu Al-e- are 0000 o o P incorporated in their entireties by reference herein. There continues to be a need for improved processing to recover metal values, in particular from reducible manganese-containing ores So and metal sulfide ores.

Carbonaceous ores, ores which contain elemental carbon graphite) and/or organic compounds, often contain valuable metals, such as gold, silver, the platinum group metals and the like. -One-characteristic of such ores which has made them difficult and expensive to process is that the presence of ES-42 I carbon and organic compounds inhibits metal recovery using conventional, cyanide, processing. In other words, the presence of organic material in such carbonaceous ores tends to interfere with metal extraction, by cyanidation. For example, a substantial amount of carbonaceous ore is not amenable to conventional cyanidation techniques because of the presence of carbon (which often acts like activated carbon), and relatively long chained organic hydrocarbon-type compounds containing sulfur, nitrogen, carboxylic acid groups and the like.

(r There is a growing world-wide interest in metal recovery from carbonaceous ores. Thus, in spite of the substantial work which has been done to provide for such metal recovery, a need currently exists to provide for a process for metal recovery from carbonaceous ores.

to,, gat SUMMARY OF THE INVENTION Io 0 A process for recovering at least one metal other than manganese from an ore containing the metal and reducible o manganese, manganese generally in the plus three or four oxidation state, and/or for recovering at least one 'Qo metal from an ore containing the metal and at least one of 0o O0 certain sulfides of a metal and/or carbonaceous material has been o discovered.

o000 o In -one-br-ae- eot,--the--pcess-i-nvolvers-t.ot±.Lg...co an ore containing the metal to be recovered and reducible manganese with an aqueous composition and a material-g., a 1"a metallurgical material, ore and the like, cont ng at least one metal sulfide in the presence of a metal ox couple more positive than about +0 versus th andard hydrogen electrode M. Latimer convention) a onditions effective to (1) 3o chemically reduce at 1 a portion of the manganese, (2) oxidize at least portion of the metal from the metal sulfide and/or the fide from the metal sulfide, and at least part y liberate the metal to be recovered from the ore; and ov ngthe--meta-fr-m-- -o ra--anthe- -as ES-42 I C1 According to the present invention, there is provided a process for recovering at l.east one first metal selected from the group consisting of gold, silver, the platinum group metals and mixtures thereof from an ore containing a reducible manganese component comprising contacting said ore with an aqueous composition and a material containing at least one metal sulfide in t 1 presence of at least one metal component at conditions effective to chemically reduce said manganese, (2) oxidize at least one of said metal from said metal sulfide and said sulfide from said metal sulfide, and liberate

O

0000 said first metal from said ore; said metal component being 0 oo selected from the group consisting of iron complexes with at least one ligand in which iron is present in an 000 a00 amount in the 3+ oxidation state effective to at least S o *o ,promote the oxidation of at least one of said metal from 0* o said metal sulfide and said sulfide from said metal sulfide, vanadium components in which vanadium is present in an amount effective to at least promote the oxidation of at least one of said metal from said metal sulfide and said sulfide from said metal sulfide, manganese complexes Swith at least one ligand in which manganese is present in 4 C, an amount in the 3+ oxidation state effective to at least S* promote the oxidation of at least one of said metal from said metal sulfide and said sulfide from said metal .t 80 sulfide and mixtures thereof; and recovering said first to a 0metal from said ore.

0"0 The present invention also provides a process for recovering at least one first metal selected from the group consisting of gold, silver, te platinum group metals and mixtures thereof from an ore containing said first metal and at least one metal sulfide of a metal other than manganese, said process comprising contacting said ore with an aqueous composition and at least one oxidant in the presence of at least one metal component at conditions effective to chemically reduce said oxidant, oxidize at least one of said metal from said metal sulfide and said sulfide froa said metal sulfide, 39 -3ai and liberate said first metal from said ore, said metal component being selected from the group consisting of iron complexes with at least one ligand in which iron is present in an amount in the 3+ oxidation state effective to at least promote the oxidation of at least one of said metal from said metal sulfide and said sulfide from said metal sulfide, vanadium components in which vanadium is present in an amount effective to at least promote the oxidation of at least one of said metal from said metal sulfide and said sulfide from said metal sulfide, manganese complexes with at least one ligand in which manganese is present in an amount in the 3+ oxidation state effective to at least promote the oxidation of at least one of said metal from said met 1 sulfide and said sulfide from said metal sulfide, and mixtures thereof; and recovering said first metal from said ore.

The present invention further provides a process for recovering at least one first metal selected from the 'ao 20 group consisting of gold, silver, the platinum group oo metals and mixtures thereof from an ore containing too* to o carbonaceous material comprising: contacting said ore with o: at least one metal component in an amount effective to at aoo least promote the oxidation of said carbonaceous material and at least one oxidant in an amount effective to provide .0 at least one of the following: form said metal 0O 0 0 component, regenerate said metal component, and (C) o o oxidize said carbonaceous material, said contacting occurring in the presence of an aqueous medium at conditions effective to chemically oxidize said carbonaceous material and liberate said first metal from said ore, said metal component being selected from the group consisting of iron complexes with at least one ligand in which iron is present in an amount in the 3+ oxidation state effective to at least promote the oxidation of said carbonaceous material, vanadium components in which vanadium is present in an amount effective to at least promote the oxidation of said 39 -3b-

AB

carbonaceous material, manganese complexes with at least one ligand in which manganese is present in an amount in the 3+ oxidation state effective to at least promote the oxidation of carbonaceous material and mixtures thereof; and recovering said first metal from said ore.

Accordingly, in one broad aspect, the process involves: contacting an ore containing the metal to be recovered and reducible manganese with an aqueous composition and a material, a metallurgical material, ore and the like, containing at least one metal C Csulfide in the presence of a metal redox couple preferably 0 0 O a o more positive than about +0.1 versus the standard hydrogen 0 0s 0 oao electrode Latimer convention) at conditions rro effective to chemically reduce at least a portion of Ro" 0 the manganese, oxidize at least a portion of the metal 0000 C C from the metal sulfide and/or the sulfide from the metal 0 sulfide, and at least partially liberate the metal to be recovered from the ore; and recovering the metal from the ore. In another broad aspect, the 0oo0 o 0 ')000 p0000 0 o 00 a 0 0 0 0 0 0 0 0 0 000000 0 0 O O 39 -3c-

/AB

E r ,:n 1 ~i 11~~1 present process involves: contacting an ore containing at least one metal tc be recovered and at least one sulfide of a metal with an aqueous composition and at least one reducible manganesecontaining material, a metallurgical material, ore and the like, in the presence of a metal redox coupleAmore positive than about +0.1 versus the standard hydrogen electrode M. Latimer convention) at conditions effective to chemically reduce at least a portion of the manganese, oxidize at least a portion of the metal from the metal sulfide and/or the sulfide from the 1r metal sulfide, and at least partially liberate the metal to be recovered from the ore; and recovering the metal from the ore.

Preferably, the above-noted contacting is conducted in the ooo presence of a metal redox couple more positive than about 0 0 oo. versus the standard hydrogen electrode M. Latimer oo convention).

0090 oo°o In a further broad aspect, the present process involves 0 contacting at least one ore containing at least one metal to be 0 00 oo o recovered and carbonaceous material with at least one added metal 0 00 Scomponent in an amount effective to at least promote the ao oxidation of the carbonaceous material. The contacting occurs at 0 conditions effective to chemically oxidize at least a portion of the carbonaceous material, and at least partially liberate the metal to be recovered from the ore. By liberation 0, is meant that the gold is more susceptible to recovery, for 0 example by cyanidation, than without pretreatment. The first metal is then recovered from the ore.

S° In one embodiment, the contacting occurs in the t000 presence of an additional oxidant, more preferably a gaseous source of oxygen, air, enriched/diluted air, oxygen and the 3o like.

In one embodiment, the redox couple or added metal component is preferably selected from at least one of the following: at ,Jeast one iron component, preferably an iron complexing agent, in which iron is present in an amount in the 3+ oxidation state effective to promote the oxidation of the metal ES-42 from the metal sulfide and/or the sulfide from the metal sulfide and/or the carbonaceous material; at least one vanadium component in which vanadium is present in an amount in the oxidation state effective to promote the oxidation of the metal from the metal sulfide and/or the sulfide from the metal sulfide and/or the carbonaceous material; at least one copper component in which copper is present in an amount in the 2+ oxidation state effective to promote oxidation of the metal from the metal sulfide and/or the sulfide from the metal sulfide to and/or the carbonaceous material; at least one cobalt component in which cobalt is present in an amount in the 2+ oxidation state effective to at least promote the oxidation of 0 0the metal from the metal sulfide and/or the sulfide from the O metal sulfide and/or the carbonaceous material; at least one manganese component in which manganese is present in an amount in the 3+ oxidation state effective to at least promote the Soo 0 oxidation of the metal from the metal sulfide and/or the sulfide 000 0o from the metal sulfide and/or the carbonaceous material; and S0° mixtures thereof. The ore or ores preferably contain precious o metals, such as gold, silver, the platinum group metals and the oO l1ke, which can be recovered using the process of this invention.

The various embodiments of this invention can be practiced singly 1 0 or in any combination of embodiments, with selection and o o optimization generally being a function of the ore type and desired metal value recovered.

The benefits resulting from the process of this oo invention, improved rate of oxidation including solubilization and/or conversion to a different form, i.e., solids, such as insoluble jarrosite, sulfates, arsenates and the 3o like, of the metal and/or sulfur species from the metal sulfide, improved rate of oxidation of the carbonaceous material and/or yield/recovery of desired metal as a function of time, are substantial. Without wishing to limit the invention to any specific theory of operation, it is believed that many of such benefits result from the promoting effect of one or more of the ES-42 above metal redox couples and/or metal components in the process of this inventica. The promoting effect of the presently useful redox couples and metal components allows the process to be effective, from the standpoint of improved recovery of desired metal as a function of time, on a wide variety of difficult to process ores.

improved yields or recoveries of metal are often achieved under less severe conditions by practicing the present process, especially when compared to recovering metal from the tocarbonaceous ore without utilizing the process of this invention.

The present process is relatively easy to operate and control, Relatively low concentrations of promoters are used and relatively mild operating conditions may be employed. With regard to carbonaceous ores, operating and capital costs are Soften reduced relative to previous chlorination/oxidation ,~procedures which require substantial amounts of chemicals aAid/or 0expensive metallurgy to combat corrosion problems. Thus, the Qpresent invention can provide a cost effective approach to metal 0" recovery from carbonaceous ores.

o,Ao,~ DETAILED DESCRIPTION OF THE INVENTION 0 The present procens provides substantial advantages.

For example, the use of at least one of certain promoting metal redox coup..s and promoting metal components, such as one or more iron components, vanadium components, copper components, cobalt components and manganese components (with or without complexing p~agents), provides for improved contacting, to increase the rate of metal and/or sulfide oxidation and/or cai~bonaceo~s Material oxidation and ultimately to improve the yield of metal or metals recovered. The improved rate of metal and/or sulfide 3o oxidation and/or carbonaceous material oxidation also results in significant process and cost economies. In addition, effective metal recoveries can be achieved utilizing low grade (heretofore difficult to process) reducible manganIese-containing ores, carbonaceous ores and relatively iteXpensive, plentiful metal ES-42 6 sulfide-containing ores. Further, the present process does not require the addition of sulfur dioxide or hydrogen sulfide to maintain or culture any bacteria.

The process of this invention is useful on any suitable recoverable metal, reducible manganese-containing ore, an ore containing oxidized manganese. At least a portion of the manganese included in this ore should be chemically reducible in the present contacting step. Typical examples of such ores are psilomelane, pyrolusite, manganite, birnessite and manganese- '1 bearing minerals from the spinel group. Particularly, the process is useful on silver, manganese-containing ores in which at least a portion of the silver is locked by the manganese- 0ooo bearing minerals such that at least a portion of the silver is 000o o not readily recovered using conventional techniques, e,g,, 00000 cyanide extraction, such silver, manganese-containing ores are ooo S00Q oo. ''preconditioned' in the present contacting step so that at least o000o a portion, preferably a major portion, of the silver is liberated oo 0 from the ore. By "liberated from the ore" is meant that the 0 Q 0 desired metal in the ore after the present contacting can be more S(ffectively recovered using conventional (preferably cyanide extraction) processing relative to the uncontacted ore, In 0 00 o °o certain embodiments of the process of this invention, a metal sulfide-containing material is contacted with the manganeseo00 o containing ore. The metal sulfide component which is used with the reducible manganese-containing ore in this invention may be any metallic sulfide ore, including, for example, Fe, Mo, As, Cu, oo Ni, Sn, Sb, Bi, Zn, Co, and mixtures thereof. The metal sulfide may be in any size or form. The metal sulfide component may be intermixed with the manganese-contaiinig ore or brought in a° contact with the manganese-containing ore by an aqueous composition which is, in turn, intermixed with the manganesecontaining ore. Metal sulfide components useful in this invention may include other minerals or compounds in amounts which do not substantially interfere or deleteriously affect the present process. Xn one embodiment, the metal sulfide has a i 1 formula of (Me)ySx wherein x and y are greater than zero, preferably x is greater than y, and Me is a metal selected from the group consisting of Fe, Mo, As, Cu, Ni, Sn, Sb, Bi, Pb, Zn, and mixtures thereof. Such metal sulfides preferably include at least one S-S (sulfur to sulfur) bond. Such sulfides include pyrites, mixed metal sulfides, iron pyrites and pyrite-like metal sulfides. Typical examples of metal sulfides and mixed metal sulfide ores are pyrite, pyrrhotite, marcasite, marionite, arsenopyrite, calcosite, chalcopyrite, covellite, bornite, sphalerite, pentlandite, millerite, cobaltite, galena, molybdenite, stannit, greenockite, argentite, stibnite, orpiment and realgar plus mixed metal sulfides. It has been found that sulfo salts, including silver sulfo salts are responsive to the process.

The recoverable metal, metal sulfide-containing ore which may be used in the process of this invention may be any suitable metallic sulfide ore. Preferably, this ore includes one Sor more iron sulfides, in particular iron pyrites. Metal sulfidecontaining ores useful in this invention may include other o minerals or compounds in amounts which do not substantially interfere or deleteriously affect the present process. The Spresent contacting step provides for at least partially liberating the metal or metals to be recovered from the sulfidecontaining ore. At least a portion, preferably a major portion of the metal to be recovered is liberated from the ore. This ore containing the desired or recoverable metal or metals, after Scontacting according to the present invention, is subjected to additional processing during which such metal or metals are recovered from the contacted ore.

8o The amount of metal sulfide employed with the reducible manganese-containing ore in the present contacting step should be sufficient to provide the chemical reduction/oxidation/metal liberation to the desired degree. Preferably, the amount of metal sulfide employed should be about 40% to about 250%, more preferably about 80% to 120%, of that required to achieve the ES-42 I I II I II II I desired degree of manganese chemical recuction. Substantial exce of metal sulfides should be avoided since such excesses may ,t in materials separation and handling problems, and may even result in reduced recovery of the desired metal or metals.

The amount of reducible manganese employed with the metal sulfide-containing ore in the present contacting step should be sufficient to provide the chemical reduction/oxidation/metal liberation to the desired degree. In such embodiments, the amount of reducible manganese employed is preferably about 40% to io about 250%, more preferably about 80% to 120%, of that required to achieve the desired degree of metal and/or sulfide oxidation.

Substantial excesses of reducible manganese should be avoided since such excesses may result in materials separation and handling problems, and may result in reduced recovery of the desired metal or metals. When the reducible manganese is regenerated in situ, with for example an additional oxidant such as air, from about 1 to about 50%, preferably from about 2 to o about 25%, by weight of that used without in situ regeneration can be used within the above ranges.

The process of the present invention is useful for o, metal recovery from carbonaceous ores, as defined herein. A large number of ore bodies and large amounts of carbonaceous ores are susceptible to be treated in accordance with the present process. Examples of such ores include: oxidized and carbonaceous ores from various locations in north central and northeastern Nevada, such as the Carlin ore, the Cortez ore and 0 the Witwatersrand ore; ores from the Prestea and Ashanti gold fields in Ghana; the Natalkinsk and Bakyrichik ores from the Soviet Union; various Canadian ores such as the gold ore from the McIntyre Mine, located near Schamacher, Ontario; and the like ores. The carbonaceous ores may include oxidized ore material, possibly even a major amount of oxidized ore material. Also, the carbonaceous ores may contain metal pyrites. The carbonaceous ore which contains metal pyrites may be processed for pyrite removal by physical and/or chemical means to reduce the pyrite ES-42 9 mae as muca i psilad-c acclimated as much as is possible and cost effective.

Alterna-F v g ptOha~iii," L i- 'rli 4 content of the ore prior to the contaoting step of the present invention or be processed along with the carbonaceous portion of the ore. Fr example, subjecting the ore to various procedures such as grinding, particle size fractionation, flo~tation and the like can reduce the amount of metal pyrites in, the ore.

The present process employs at least one of certain metal redox couples and/or metal components. Such metal components may inclu~de alkali and/or alkaline earth metals provided -that they also contain one or more additional metals 1- which are effective in the present inventirn. Such metal redox couples and/or metal components are presu-.t during the contacting step in an amount effective to at least promote the ox!d&tion of the metal and/or sulfide portions of the metal sulfide and/or the carbonaceous material in the ore. Thus, such metal roidox couples and/or components are present in an amount effective to promoto such oxidation and/or to oxidize the metal and/or sulfide portions of the metal sulfide and/or to oxidize the carbonaceous material in the ore.

The presently useful metal redox couples and metal components are preferably selected from the group consisting of iron components, copper components, cobalt components, vanadium components, manganese 3+ compoaents and mixtures thereof. more preferably, the metal redox couples and metal components are selected from the group consistingj of iron components in which iron is present in an amount la the 3+ oxidation state in an amount effective to at least promote the oxidation of at least one of the metal and sulfide of the metal sulfide and/or of the ore's carbonaceous material; copper components in which copper is 3o present in an amount in the 2+ oxidation state effective to at least promote the oxidation of at least one of the metal and sulfide of the metal sulfide and/or of the ore's carbonaceous material; cobal. components in which cobalt is present in an amount in the 2+ oxidation state effective to at least promote the oxidation. of at least one of the metal and ES-42 r sulfide of the metal sulfide and/or of the ore's carbonaceous material; vanadium components in which in which vanadium is present in the 4+ or preferably oxidation states in an amount effective to at least promote the oxidation of at least one of the metal and sulfide of the metal sulfide and/or of the ore's carbonaceous material; manganese components in which manganese is present in the 3+ oxidation state in an amount effective to at least promote the oxidation state in an amount effective to at least promote the oxidation of at least one of the metal and/or sulfide of the metal sulfide and/or of the ore's carbonaceous material, and mixtures thereof. Any suitable metal component may be employed provided that such component is capable of at least promoting the oxidation, noted above. Particularly useful vanadium 5+ components are vanadium pentoxide, V 2 0 5 o and the soluble vanadates and oxyanion derivatives thereof, and 0,00 complexes of vanadium 5+ with ligands.

The copper +2 components are particularly geffective oo when present in combination with an amount of ferric ion. In this embodiment, the copper +2 component acts to enhance the ao overall oxidation of the metal and/or sulfur from the metal o*°o sulfide and/or the carbonaceous material. If one or more ooOo vanadium and/or copper components are present in the contacting, the vanadium 5+ and/or copper 2+ concentration is preferably at least about 10 ppm.,, more preferably about 50 ppm. to about and still more preferably about 100 ppm. to about 0.1% or to about by weight of the aqueous composition present during the contacting, calculated as elemental vanadium and/or copper.

When vanadium 5+ and/or copper 2+ components are employed with a metal sulfide-containing ore, the reducible 3o manganese component is prc ferably capable of oxidizing and maintaining an effective amount of vanadium/copper component to the vanadium 5+ and/or copper 2+ oxidation states at the contacting conditions.

In one embodiment, the iron, copper and cobalt, vanadium and manganese components are soluble and ore preferably ES-42 selected from iron complexes with ligands, copper complexes with ligands, cobalt complexes with ligands, vanadium components with ligands, manganese components with ligands, and mixtures thereof.

Such complexes preferably include at least a portion, more preferably a major portion and still more preferably substantially all, of the metal in the preferred oxidation state, noted above.

Examples of iron complexes useful in the present invention include iron complexes with polyfunctional amines, for i 0 example, ethylenediamine, propylene diamine, ethanol amine, glycine and asparagine and salts thereof; phosphonic acids and phosphonic acid salts, for example, ethane-l-hydroxy-1, 1 diphosphoic acid; pyridine and substituted, chelating pyridine derivatives, for example, phenanthroline, 0-phenthroline, 2, 2 bipyridyl, glyoxime and salicylaldehyde derivatives; aquo; and SCN-. Among the particularly preferred iron complexing agents for I'a° use in the present invention are those selected from the group S consisting of substituted, chelating derivatives of pyridine, aquo, CN- and mixtures thereof.

Examples of copper complexes useful in the present o invention are copper, in particular copper complexes with pyridine, 1, 10-phenanthroline, imidazole, substituted, nonchelating derivatives thereof and mixtures thereof. These Koo derivatives include substituents such as hydroxy, carboxyl, amino, alkyl and aryl groups.

Cobalt, in particular cobalt complexes of chelating Schiff's bases are preferred. These ligands include, for example, ligands utilizing 1, 2 diarines, 1, 3-diamines, substituted 1, 2 dionemonoximes, substituted 1, 3-dionemonoximes, So substituted svlicylaldehydes and mixtures thereof, such as bis (salicylaldehyde) ethylenediamine and bis 3butandionemonoxime) ethylenediimine. Examples of vanadium and manganese complexes involving oxyonions are sulfate, nitrate, and carboxylates, acetates.

ES-42 As will be recognized by those skilled in the art, the stability of the complexes formed will often be affected by the pH of the aqueous composition employed in the present contacting step. Some stability of the complex or complexes may have to be sacrificed because of the pH of the aqueous composition during th, contacting, which pH may be preferred for various processing reasons. This reduced complex stability has surprisingly been found not to have an undue adverse effect on oxidation. The particular pH employed can also affect the salt form of the o complexing agent employed, and such complexing salts are complexing agents within the scope of this invention.

The presently useful metal complexes are preferably not f fully complexed, with, for example, partial ligand complexes, not fully complexed at a ratio of ligand to metal which .:Ia9t substantially reduces the redox cycling activity of the ligand complexes. This feature, active redox cycling complexes, apparently facilitates the ability of the metal species to 'aia :rapidly cycle between oxidation states and/or to promote the desired oxidation. With vanadium complexes, the mol ratio of .vanadium to ligand is more preferably about I to about 3, still amore preferably to about 2, with iron complexes the mol ratio of S iron to ligand is more preferably about 1 to about 3, more preferably to about 2, and with manganese complexes the mol ratio a 0 0 of manganese to ligand is more preferably about 1 to about still more preferably to about Any suitable ligand system may be employed. The .00 ligands are preferably derived from the group consisting of compounds containing actylacetonate functionality, carboxylic acid functionality (more preferably containing up to about %0 carbon atoms per molecule), poly, more preferably three, carboxylic acid functionalities, substituted carboxylic acid functionality (more preferably containing up to about 15 carbon atoms per molecule) poly, more preferably three, substituted carboxylic acid functionalities, and mixtures thereof.

Particularly useful lLgand systems are derived from the group ES-42 consisting of compounds containing acetylacetonate functionality, citric acid functionality, tartaric acid functionality, nitrilotriacetic acid functionality and mixtures thereof and their partial salts particularly sodium, potassium and ammonium partial salts, and partial esters and substituated derivatives thereof. Particularly preferred species are citric acid, tartaric acid and nitrilotriacetic acid and their partial salts and esters thereof as illustrated above.

The specific amount of the metal redox couple or metal ro component, metal, complex, employed may vary over a wide range and depends, for example, on the reducible manganesecontaining ore, the metal sulfide, the carbonaceous ore and/or the metal redox couple/metal component employed, and on the degree of oxidation desired.

In certain embodiments, preferred concentrations of the metal complex are in the range of about 150 to 10,000 ppm, more preferably about 200 to about 1,000 ppm., or to about 5000 ppm, by weight based upon the aqueous composition employed in the contacting, calculated as elemental metal. It is generally a convenient to provide the metal complex in combination with, preferably in solution in, the aqueous composition used in the contacting step.

The metal complex can be added to the contacting step and/or can be formed in situ prior to or in the course of the contacting.

Tho, present contacting preferably takes place in the presence of an aqueous liquid medium or composition. The metal redox couples or metal components, which are preferably soluble in the aqueous medium, may be added to the aqueous medium prior 3o to the contacting. Any suitable, aqueous medium can be employed in th5 present process. The pH of the aqueous medium may be acidic, neutral or basic depending, for example, on the composition of the ore or ores being treated, the specific metal redox couple or metal component being employed, and the presence or absence of other components or entities during the contacting.

ES-42 14 L--~l~llll~l

I

Preferably, the pH of the aqueous composition is in the range of about 1 or less to about 13, about 10, or more. The pH of the aqueous medium may be adjusted or maintained, during the contacting step, for example, by adding acid and/or base.

In certain embodiments, the pH of the aqueous composition may be in the range of about 0.1, preferably about to about 5, or in the range of about 1.5 to about 4.5, or about 3.0 and lower. In other embodiments, the pH of the aqueous composition may be in the range of about 1 or 1.5 to about 3.0 or to about 1 or 1.5 to about In still other embodiments, the contacting preferably occurs at a slightly acidic pH, a pH no lower than about 6, or at an alkaline pH. If a vanadium complex is present, th contacting is more preferably conducted at a pH in the range of about 6 to about 13, while if an iron complex is present, the pH 2, is more preferably about 6.5 to about 9.5. For manganese complex 0 the pH is preferably about 7.5 to about 10.5. These more 4. preferred pH ranges are particularly useful when it is desired to maintain the metal redox couple or metal component substantially Zo soluble, in the aqueous medium, at the contacting oo% conditions.

600 The aqueous medium comprises water, preferably a major amount of water. The medium is preferably substantially free of 0° o ions and other entities which have a substantial detrimental effect on the present process. Any suitable acid and/or base or combination of acids and/or bases may be included in, or added 0 to, the medium to provide the desired pH. For example, hydrogen halides, preferably hydrogen chloride, sulfurous acid, sulfuric acid, metal salts which decompose (in the aqueous medium) to form 3o such acids, alkali metal hydroxides, alkaline earth metal hydroxides, ammonium hydroxide, metal salts which decompose (in the aqueous medium) to form such bases, their corresponding carbonates, preferably sodium carbonate, mixtures thereof and the like may be employed. The quantity and composition of the aqueous medium may be selected in accordance with the ES-42 -i _i _i i requirements of any given ore to be treated and as may be found advantageous for any given mode applying The present process in practice. In carrying out the present process, one or more wetting agents and/or sulfur dispersion agents can be included i.n, added to, the aqueous composition (in addition to the metal redox couples or metal components) to further enhance rates and/or yields. Examples of such agents include hydrocarbon sulfonates, lignosulfonates, alkyl substituted succinic anhydrides, alcohol ethoxylates and the like.

The amount of metal redox couples or metal components employed may vary widely provided that such amount is effective to function as described herein. Such metal redox couples or metal components are preferably present during said contacting in San amount less than about more preferably in the range of Sabout 10 ppm. to about 1% by weight, calculated as elemental Smetal, based on the amount of ore present and/or liquid present ~during conta(:ting such as a solution used In an agitated leach or during a vat or heap leach. one of the substantial advantages of bhe present process is that large amounts of metal redox couples D 'r metal components are not required although adjustments can be made depending on the metal sulfide and/or deleterious carbon concentration in the ore. Thus, in order to reduce costs still further while achieving benefits of the present invention, low Uy concei~itrations of such materials are preferably selected. The mol ratio of complexing agent to metal ion that is used to form the promoter component may be ILn the range of about 0.01 to for example about 0.5 to about 2.0. Preferred concentrations of metal redox couples or metal components are in the range of about to 10,000 ppm, more preferably about so to about 1,000 ppm. or 3oto about 5,000 ppm by weight, based upon the aqueous composition, calculated as elemental metal.

in one embodiment, the present contacting occurs in the presence of added ferriQ ion in an amount effective to facilitate the liberating of the metal or metals to be recovered from the ore or ores. The ferric ion may be added to the contacting step ES-42 vvp_ separately, as Fe(S0 4 3 and/or other compounds which produce the desired amount of ferric ion when combined with the present aqueous composition in the contacting step or may be generated in situ. In order to more effectively control the amount of ferric ion present and to provide improved contacting, it is preferred that the ferric ion be combined with the aqueous composition prior to the present contacting step or adjusted, while recycling the aqueous composition, during ore processing. The amount of ferric ion used in the present process to is typically minor, when compared to the amount of ore or ores and metal sulfide-containing material and/or reducible manganesecontaining material used, and may vary depending on many factors, for example, the composition of the ore or ores and of the metal sulfide-containing material and/or the reducible manganesecontaining material and the degree of metal liberation desired, Preferably, the added ferric ion is present in an amount of at least about 10 ppm. (by weight) of the aqueous composition. More preferably, the added ferric ion is present in an amount in the range of about 0.01% to about or even higher, for example ao to about by weight of the aqueous solution.

The present contacting is preferably conducted in the presence of at least one oxidant other than the metal redox couple or metal component or the reducible manganese. The oxidant is present in an amount effective to do at least one of the following: maintain or form the metal redox couple or metal component, produce or regenerate at least a portion of the metal redox couple or metal component, and/or oxidize at least a portion of the metal and/or sulfide portions of the metal sulfide and/or reduced manganese component (to produce reducible so manganese) and/or the carbonaceous material in the ore. The oxidant or oxidants may be present during the contacting step and/or during a separate step to form and/or regenerate the metal redox couple or metal component. Any suitable oxidant capable of performing one or more of the above-noted functions may be employed. The oxidant is preferably selected from the group ES-42 consisting of molecular oxygen in the form of air, dilute or enriched air, or other mixtures with nitrogen or carbon dioxide), singlet oxygen, ozone, inorganic oxidant components containing oxygen and at least one second metal and mixtures thereof. More preferably, the oxidant is selected from the group consisting of molecular oxygen, oxidant components containing oxygen and at least second metal and mixtures thereof. Still more preferably, the oxidant is selected from the group consisting of oxidant components containing oxygen and at least 1° one second metal and mixtures thereof. One particularly preferred system involves an oxidant component containing oxygen and at least one second metal, and molecular oxygen in an amount effective to maintain the oxidant component in tha desired oxidized state and/or to oxidize at least a portion of the metal and/or sulfide portions of the metal sulfide ar3/or reduced manganese component (to produce reducible manganese) and/or the carbonaceous material in the ore. Care should be exercised to avoid large excesses of the oxidant to as to minimize reactions that could solubilize deleterious elements, arsenic, etc.

The amount of oxidant employed is preferably in the range of about 10 to about 200%, preferably about 80% to about 140% of that needed to oxidize the metal and/or siilfide portions of the metal sulfide and/or reduced manganese component (to produce reducible manganese) and/or the carbonaceous ore to allow for improved liberation of the metal to be recovered in the present o, process.

The reducible second metal oxidants useful in the present invention may be chosen from a wide variety of materials, The second metal or metals are preferably not the same as the 3o metal or metals to be recovered from the ore or ores.

Preferably, the second metal is a metal which forms reducible metal oxides which are reduced during the conduct of the prccess of this invention. Many of the transition metals have this property. Typical examples of metals which have this property include minerals and other compounds which are generally solids ES-42 18 under the condition of the process, such as, manganese, tin, lead, bismuth, germanium, antimony, indium and certain of the rare earth metals and minerals, cerium, praseodyminium and terbium and mixtures of rare earth minerals which typically have varying ratios of lanthanum, cerium, etc. Such reducible second metal components are preferably capable of becoming at least partially reduced at the present contacting conditions to form a reduced second metal component.

The present contacting results in at least a portion of S o the reducible second metal component being chemically reduced to form a reduced second metal component. This reducible/reduced second metal component can exit the contacting zone and be separated from the ore or ores, in particular the contacted ore .io or ores, partial to substantial separation. This component can be used on a once-through basis, or may be regenerated to reducible second metal component, in situ or externally and Srecycled to the contacting zone. In the case of a once-through basis, it is preferred to minimize the amount of reduced second metal component exiting with the ore or ores. Such regeneration oa can be done by electrochemically (preferably external) oxidizing the reduced second metal component or oxidizing the reduced second metal component with molecular oxygen, in situ or external, preferably promoted for purposes of enhanced yield and rate, at ambient and/or elevated temperatures to convert the reduced second metal component to a reducible second metal component.

Manganese is a more preferred second metal. In one embodiment, the reducible manganese component includes manganese in the 4+ oxidation state. One particularly useful reducible 3o manganese component is manganese (manganic) dioxide and its pyrolusite, manganite, birnessite and manganese-bearing minerals from the spinel group. Silver, manganese-containing ores in which at least a portion of the silver is locked by the manganese-bearing minerals are particularly useful in combination with ores containing carbonaceous material, as described herein.

ES-42 A second preferred embodiment is redox active manganese +3 where the manganese is complexed as above and is capable of reoxidizing one of the other metal complexes and/or metal components set forth above such as vanadium under the process condition of pH, for example, at pH's greater than about 7. It is contemplated that the first and second reducible manganese components can be the same or different or mixtures thereof, In the above embodiment, it is preferred to have present molecular oxygen during processing, The latter system provides substantially Io soluble components for recovery of metal.

The amount of oxidant employed in the present invention is chosen to facilitate the desired functioning of the present contacting step. Without limiting the invention to any specific theory or mechanism of operation, it may be postulated that when oxidant is employed such oxidant acts in conjunction with the 0. metal redox couple or metal component to oxidize at least a portion of the metal and/or sulfide of the retal sulfide and/or S the carbonaceous material in the ore and "liberate" the metal to be recovered from the ore. Although the metal redox couple or oo metal component may take an active part in the oxidation and liberation functioning, when oxidant is employed, such metal Sredox couple or metal component preferably acts as a catalyst and may be, and preferably is, used more than once in the present contacting step, is recycled to the present contacting step or is employed to contact more than one increment of the ore or ores.

The amount of oxidant employed preferably acts to facilitate the desired oxidation of at least a portion of the metal and/or sulfide of the matal sulfide and/or carbonaceous %o material and liberation of metal to be recovered from the ore.

The specific amount of oxidant employed varies depending on many factors, for example, the specific ore or ores being treated, the specific metal redox couple, metal component and oxidant being employed, and the specific degree of oxidation and metal liberation desired. If a reducible second metal oxidant is used, ES-42 I Ir~

I

it preferably is used in an amount in the range of about 0.1% or less to about 10% or more to about 150% by weight of the metal sulfide or deleterious carbon content of carbonaccous ore.

Preferably, the amount of second metal component employed in the present contacting step should be sufficient to provide the oxidation/metal liberation to the desired degree. More preferably, the amount of second metal component employed should bs about 40% to about 250%, more preferably about 80% to 120%, of that required to achieve the desired degree of metal and/or fo sulfide and/or carbon oxidation. Substantial excesses of second metal component should be avoided since such excesses may result in materials separation and handling problems, and may result in reduced recovery of the desired metal or metals.

Although one or more of the oxidants may be utilized in a separate oxidation or regeneration step, it is preferred that such oxidants, and in particular reducible second metal components, be present and effective during the contacting step of the present invention, In one embodiment, the present contacting occurs in the .h presence of at least one species of Thiobacillus bacteria in an amount effective to facilitate the liberating of the metal or metals to be recovered from the ore or ores. Since, in certain embodiments, the contacting preferably results in at least a portion of the manganese in the reducible manganese-containing ore or reducible manganese-containing material being dissolved in the aqueous composition and since the bacteria is preferably present in an acidic composition, the bacteria are preferably tolerant (remain active) in such manganese-containing compositions. The aqueous compositions and the bacteria 2s contained therein are maintained under regeneration conditions, at conditions conducive to the propagation of bacteria, during the contacting step.

As the contacting step progresses, the aqueous composition (the lixiviant solution) preferably becomes ES-42 increasingly concentrated in dissolved manganese from the reducible manga- ese-containing ore or reducible manganesecontaining material, in the form of manganese sulfate if sulfuric acid is employed. Above certain high concentrations of manganese, the buildup of manganese will in turn reduce the activity of the Thiobacillus bacteria. In practice, the contacting step is controlled, particularly through its initial stage, to produce effective quantities of adequately manganese tolerant bacteria, for example and preferably, by controlling the ratio of reducible t4 manganese-containing ore or ores to metal sulfide-containing material or of reducible manganese-containing material to aqueous composition and/or the bleed rate of the manganese-containing aqueous composition to insure a safe buildup rate of manganese ions in the aqueous composition. By increasing the proportion of solids to liquid, the manganese buildup rate in the aqueous composition is increased and vice versa. The manganese concentration, the total dissolved solid, and the bacterial activity in the aqueous composition can be monitored on a periodic basis as an aid to process control.

In instances where it is not practicable or dasirable to exercise the required degree of c-ntrol of the contacting step throughout the period of time required for developing suitably tolerant bacteria and where, consequently, it is preferred to commence the contacting step with an adequate supply of suitably tolerant bacteria, cultures of such bacteria nay be prepared by S known methods. Normally, the Thiobacillus bacteria can tolerate manganese in concentrations as high as 2.5 weight percent. In concentrations above 2.5 weight percent, the growth of the bacteria is slowed to a point at which bacteria become 3o inactive. However, the bacteria can be and preferably are acclimated to higher concentrations of manganese ion by slowly increasing the manganese ion concentration level in the aqueous, acidic composition. By normal acclimation techniques, the manganese tolerance of the bacteria can be increased to greater than about 4 weight percent. The bacterie are preferably ES-42 22 acclimated as much as is possible and cost effective.

Alternately, Thiobacillus bacteria may be acclimated to higher manganese levels using chemostate techniques operating in a continuous mode.

Sources of the Thiobacillus bacteria useful in this invention include sources such as the American Type Culture Center and bacteria found to be naturally occurring in ore bodies. Of the Thiobacillus ferrooxidans bacteria available from the American Type Culture Center, cultures ATCC-14119, ATCC- I 19859, ATCC-21834, and ATCC-33020 have been used in the process of this invention. All of these cultures have been found to be satisfactory.

The pH necessary for the bacterial action may oo preferably be as low as about 1.5 and as high as about 4.5 for the Thiobacillus ferrooxidans bacteria. However, if the bacteria are acclimated to a lower pH, the pH of the aqueous composition a in the present contacting step may be adjusted accordingly.

Both the temperature extremes and the preferred temperature rangts may be adjusted if the bacteria are acclimated to different ranges.

0:0:00The bacteria are typically cultivated with nitrogen, phosphorous and sulfate, or utilize naturally occurring 0000 nutrients. Any suitable combination of compounds or components containing these constituents may be used to culture the bacteria. Suitable compounds include ammonia, ammonium sulfate, ammonium phosphate, alkali and acid phosphates, mixtures thereof i4 and the like. Preferably, magnesium is also included in the culturing compounds or components and suitable magnesium content may be provided by adding magnesium sulfate.

In utilizing the process of this invention, certain precautions should preferably be taken to improve performance.

For example, the raw materi is and equipment utilized throughout the processing circuit should normally be such as will not release or act as bactericides under the conditibns prevailing during the process. Minerals which may be harmful to the ES-42 bacteria include the elements cobalt, zinc, nickel, copper, mercury, and molybdenum. Concentrations of these minerals found in pyrites normally do not exceed levels which would be harmful to the bacteria. Element concentrations which would be harmful to the bacteria are illustrated in Zeitzrhriferology Microbiology, 12/72, 310. However, as with the manganese, these concentrations may be exceeded by the use of bacteria which have been acclimated, to the harmful mineral.

The contacting of the present invention takes place at a temperature and prassure and for a time sufficirint to obtain the desired results. A combination of temperature and pressure effective to maintain water (the aqueous medium) in the liquid ostate is preferred. in one embodiment, temperature:. of about 200 0 to about 140 0 C. with temperatures in the range of about 20 0 C. to 2~about 110 0 C. and in particular between about 25 0 C. to about 80 0

C.

being especially useful. Contacting pressure may be in the range of about atmospheric to about 500 psia or more. Pressures in the range of atmospheric to about 100 psia have been found to provide satisfactory results.

Contacting times vary widely depending, for example, on O the mode in which the contacting is performed. Such contacting time may range from minutes to weeks or even months. For 0 example, if the contacting occurs in a stirred tank with the ore or ores present in a slurry with the aqueous medium and the metal redox couple or metal component, the contacting time preferably is in thie range of about 0.1 hours to abeiit 60 hours, more preferably about 1 hour to about 24 hours. or, the other hand, if the contacting takes place with the ore or ores placed in a heap with the aqueous medium and metal redox couple or metal component 110 being made to f.Iow through the heap, the contacting time is preferably in the range of about 1 day to about 6 months, more preferably about 7 days to about 60 days.

The present process may be conducted on a batch or continuous basis. The present contacting step may be conducted on a pad, with the ore or ores to be treated situated in a heap; ES-42 I- or in a vat, tank or other suitable arrangement. The primary criterion for the contacting step is that the desired manganese chemical reduction/metal and/or sulfide oxidation (solubilization)/carbonaceous material oxidation and metal liberation take place. Preferably, the metal, manganesecontaining ore and metal sulfide-containing material and/or the metal, metal sulfide-containing ore and reducible manganesecontaining material and/or the metal-containing carbonaceous ore and the oxidant and the metal redox couple or metal component are ir brought together to form an intimate admixture generally with the aqueous composition. The ore or ores are preferably subjected to particle size reduction, by crushing, grinding, milling and the like, prior to contacting to render the ore or ores more easily and/or effectively processed in the present contacting step. Air or other gaseous oxidant may be dispersed through, or otherwise contacted with, this admixture during the contacting step to achieve the desired result. Amounts of acid and/or base and/or ferric ion can be added to the initial admixture and/or may be added during the contacting to provide the desired pH and L. ferric ion concentration.

The pH of the aqueous liquid medium may be adjusted or maintained during the contacting step, for example, by adding one or more basic components to the aqueous liquid medium. Any suitable basic component or combination of such components may be included in, or added to, this medium to provide the desired basicity. For example, basic alkali metal and alkaline earth metal components, hydroxides, silicates, carbonates and bicarbonates, mixtures thereof and the like may be employed.

Because of cost, availability and performance considerations, 3c calcium hydroxide, sodium hydroxide, sodium carbonate, and mixtures thereof are preferred.

If bacteria are employed, it is preferred that this intimate admixture also include the bacteria. If bacteria are utilized, the aqueous composition preferably includes one or more nutrients useful by the bacteria. One or more of these nutrients ES-42 may be included with one or more of the ores, sulfide material, reducible manganese-containing material, intimate admixture and aqueous composition.

The solid ore/material remaining after the contacting step may be subjected to any suitable metal recovery processing step or steps for the recovery of the metal, silver, gold, the platinum group metals and the like. For example, this solid ore/material may be neutralized with any suitable acidic or basic material, such as sulfuric acid, carbonates, bicarbonates io white lime or milk of lime, and then subjected to a conventional sodium cyanide extraction, followed by activated carbon treatment and zinc dust precipitation. Alternately, the solid ore/material after contacting can be neutralized and subjected to an ammonium thiosulfate or an acid thiourea extraction followed by zinc dust precipitation. Still further, the solid ore/material after contacting can be subjected to a brine extraction followed by ion exchange to recover the desired metal or metals. The conditions at which these various recovery processing steps take place are conventional and well known in the art, and therefore are not described in detail here. However, it is important to note that conducting the metal recovery processing on the ore/material after the contacting of the present invention provides improved metal recovery performance relative to conducting the same metal recovery processing without this contacting.

In a further embodiment of this invention the contacting step and metal, silver, gold, platinum group metals and the like, recovery step can be practiced at the same time in the same processing system, agitated, vat or heap.

The pH of both systems should be similar to avoid any deleterious 3o side reactions eg., destruction of the cyanide solution or thiourea. For example, the metal redox couples and metal components which are effective at higher pH's, about 7 to about 13, can be used in the presence of cyanide leaching solution to provide both liberation and recovery of metals in the same system. Particularly preferred metal complexes are the ES-42 soluble redox active complexes of vanadium, iron, manganese and mixtures thereof, in particular those complexes wherein the ligands are derived from compounds having polycarboxylic acid functionalites and substituted polycarboxylic acid functionalities and the preferred ranges, substituents and species as set forth above.

One processing arrangement which provides outstanding results involves the agglomeration of, for example, the metal, manganese-containing ore and the metal sulfide-containing 1° material and/or the metal, metal sulfide-containing ore and the reducible manganese-containing material and/or the metalcontaining carbonaceons are and reducible second metal component.

The ore, ore and/or materials are preferably subjected to crushing, grinding, or the like processing to reduce particle size to that desired optimum metailurgical liberation, generally a maximum particle diameter of about 1/2 inch or less. The solid particles are mixed with sufficient aqueous liquid and if desired, promoter and bacteria. This intimate admixture is formed into agglomerates by conventional processing, such as agglomeration, extruding, pilling, tableting and the like.

The agglomerates are placed on a pad, to form a heap which is built up by addition of agglomerates, preferably over a period of time in the range of about 15 days to about 60 days.

During the time the heap is being built up, and preferably for a period of time ranging up to about 3 months, more preferably about 2 months to about 3 months after the last agglomerates are added to the heap, an aqueous composition containing the metal redox couple and/or component and preferably adjusted for pH, ferric ion and/or the presence of air, is made to flow through 3o the heap, from the top to the bottom of the heap. If bacteria are used, the aqueous composition includes one or more nutrients for the bacteria,, After contacting the heap, the aqueous composition is collected and processed for disposal; or processed for manganese, second metal and/or metal redox couple and/or metal component metal recovery, regeneration and/or ES-42 27 1 recycling to the heap. This contacting provides another important benefit in that at least a portion of the "cyanacides," such as copper, which may be present in the ore and/or metal sulfide-containing material is removed and/or deactivated. Such "cyanacides" cause substantial increases in cyanide consumption if present in cyanide extraction processing. Therefore, removing and/or deactivating cyanacides in the present contacting step provides for more effective metals recovery by cyanide extraction.

to After the heap-aqueous composition contacting has proceeded to the desired extent, an aqueous basic white O lime, milk of lime or the like basic components) composition is contacted with the heap to neutralize the heap if a pH below 7 oo was used. After this neutralization, the agglomerates may be o 0 placed on a second heap, which is preferably larger than the heap o o, previously described.

In addition, the neutralized agglomerates may be broken apart and reagglomerated prior to being placed on the second heap to provide for any incidental neutralization and/or to expose the .kOi treated ore for subsequent cyanidation. This can be done using conventional means, such as subjecting the agglomerates to grinding, milling or the like processing, and then forming the second agglomerates by agglomeration, extruding, tableting, pilling, pelletizing or the like processing.

In any event, if a second, preferably larger, heap is formed on a pad, or if one heap is used, then a dilute aqueous cyanide, preferably sodium cyanide, solution is made to contact the heap. Typically, this cyanide contacting is performed in the presence of air. Preferably, the cyanide solution is percolated ,o through the heap. The cyanide solution, after being contacted with the heap, contains the metal or metals to be recovered.

This solution is collected and sent to conventional further processing for recovery of the metal or metals.

Both heaps are preferably maintained at ambient conditions of temperature and pressure. Also, both heaps ES-42 may be built up and worked (contacted) with the aqueous composition and the cyanide solution for as long as the economics of the particular application involved remain favorable.

When an agitated leach in vessels is used for the process, contact times may vary depending, for example, on the specific ore or ores being contacted, the other components present during the conitacting and the degree of metal recovery desired. Contact times in the range of about 5 minutes or less to about 48 hours or more may be used. Preferably, the contact to time is in the range of about 4 hours to about 36 hours, more preferably about 8 hours to about 24 hours. During this time, agitation can be advantageously employed to enhance contacting.

Known mechanical mixers can be employed.

While the present invention has been described with respect to various specific examples and embodiments, it is to be understood that the present invention is not limited thereto and that it can be variously practiced within the scope of the following claims.

ES-42

Claims (8)

1. 2. A process for recovering at least one first metal selected from the group consisting of gold, silver, the platinum group metals and mixtures thereof from an ore containing said first metal and at least one metal sulfide of a metal other than manganese, said process comprising contacting said ore with an aqueous composition and at least one oxidant in the presence of at least one metal component at conditions effective to chemically reduce said oxidant, oxidize at least one of said metal from said metal sulfide and said sulfide from said metal sulfide, and liberate said first metal from said ore, 39 IIZ :r.;.irisr*i~,wrun~Llr. said metal component being selected from the group consisting of iron complexes with at least one ligand in which iron is present in an amount in the 3+ oxidation state effective to at least promote the oxidation of at least one of said metal from said metal sulfide and sa.id sulfide from said metal sulfide, vanadium components in which vanadium is present in an amount effective to at least promote the oxidation of at least one of said metal from said metal sulfide and said sulfide from said metal sulfide, manganese complexes with at least one ligand in which manganese is present in an amount in the 3+ oxidation state effective to at least promote the oxidation of at least one of said metal from said metal sulfide and said ;ulfide from said metal sulfide, and mixtures thereof; and recovering said first metal from 4444 said ore. S 3. A process for recovering at least one first metal selected from the group consisting of gold, silver, the platinum group metals and mixtures thereof from an ore containing carbonaceous material comprising: contacting 4 said ore with at least one metal component in an amount effective to at least promote the oxidation of said carbonaceous material and at least one oxidant in an S0o amount effective to provide at least one of the following: form said metal component, regenerate said metal component, and oxidize said carbonaceous l 0 material, said contacting occurring in the presence of an aqueous medium at conditions effective to chemically oxidize said carbonaceous naterial and liberate said first metal from said ore, said metal component being selected from the group consisting of iron complexes with at least one ligand in which iron is present in an amount in the 3+ oxidation state effective to at least promote the oxidation of said carbonaceous material, vanadium components in which vanadium is present in an amount effective to at least promote the oxidation of said carbonaceous material, manganese complexes with at least one ligand in which manganese is present in an amount in 39 -31- AB (I 4 B f; T ^v the 3+ oxidation state effective to at least promote the oxidation of carbonaceous material and mixture' thereof; and recovering said first metal from said ore.
2. 4. The process of claim 1, 2 or '3 wherein said vanadium components are vanadium complexes with at least one ligand. The process of claim 4, wherein said iron complexes, said vanadium complexes and said manganese 3+ complexes are partial complexes.
3. 6. The process of claim 4 or 5, wherein at least one of said iron complexes, said vanadium complexes and ""ao said manganese complexes include a ligand derived from the group consisting of compounds containing acetylacetonate functionality, carboxylic acid o*u functionality, polycarboxylic acid functionalities, *tO 0 substituted carboxylic acid functionality and substituted C O polycarboxylic acid functionalities and mixtures thereof.
4. 7. The process of claim 6, wherein the compounds containing carboxylic acid functionality substituted carboxylic acid functionality, polycarboxylic acid oo functionalities and substituted carboxylic acid functionalities and substituted polycarboxylic acid functionalities contain up to 15 carbon atoms per molecule, 4 48. The process of claim 4 or 5, wherein at least one of said iron complexes, said vanadium complexes and said manganese complexes include a ligand derived a a from the group consisting of compounds with S. acetylacetonate functionality, citric acid functionality, tartaric acid functionality, nitrilotriacetic acid functionality and mixtures thereof. 9, The process of claim 1, 4, 5, 6, 7, or 8, wherein said contacting occurs in the presence of at least one oxidant. The process of any one of claims 1 to 9, wherein said recovering step comprises contacting said ore with aqueous cyanide solution to solubilize at least a portion of said first metal.
5. 11. The process of claim 2, wherein said oxidant is 39 -32- AB Mz i, selected from the group consisting of molecular oxygen, singlet oxygen, ozone, oxidant components containing oxygen and at least one second metal, and mixtures thereof.
6. 12. The process of claim 2, wherein said oxidant comprises a reducible manganese-containing component.
7. 13. The process of claim 12, wherein said oxidant further comprises molecular oxygen.
8. 14. The process of claim 13, wherein molecular oxygen acts to oxidize a reduced manganese component to form at least a portion of said reducible manganese component. The process of claim 12, wherein said reducible manganese component is regenerated by oxidation of a reduced manganese component. DATED: 10 AUGUST, 1990 PHILLIPS ORMONDE FITZPATRICK Attorneys For: 0 04 20 ENSCI INC. SQo 00 a 00 C0 o 04 0 0 1971Z a A*