[0001] This application claims priority from Australian Provisional Patent Application No. 2021902174, the contents of which are hereby incorporated herein by reference.

TECHNICAL FIELD

[0002] The present invention relates to a gold recovery circuit and method.

[0003] More particularly, the present invention relates to a gold-copper recovery circuit having a reduced operating cost.

BACKGROUND ART

[0004] The following discussion of the background art is intended to facilitate an understanding of the present invention only. The discussion is not an acknowledgement or admission that any of the material referred to is or was part of the common general knowledge as at the priority date of the application.

[0005] The most prevalent hydrometallurgical method of extracting gold from ore is by cyanidation, also known as the MacArthur-Forrest Process.

[0006] During cyanidation, a slurry containing water and milled ore is combined with cyanide solution and transferred to a leaching circuit, most commonly a carbon-in-leach (CIL) circuit, although a variety of other types of leach circuits exist.

[0007] The cyanide in the solution acts as a solvent to dissolve, or leach, the gold from the ore.

[0008] Following leaching, the resulting gold-cyanide complex is separated from the slurry by adsorption onto an adsorbent. This is commonly achieved by adding activated carbon as an adsorbent to the slurry.

[0009] The most prevalent adsorbent remains activated carbon, which is partially selective and therefore adsorbs other metals in addition to gold, such as copper and silver. Other metals, such as base metals, may also be adsorbed dependent on the mineralisation of the ore or concentrate treated. [0010] Although alternative adsorbents are known, these are typically used under particular circumstances, for example with preg-robbing ores where a selective adsorbent is preferred.

[0011] One example of an alternative adsorbent is resin, used in resin-in-pulp (‘RIP’) or resin-in-leach (‘RIL’) circuits. A range of suitable resins is known to those skilled in the art of gold hydrometallurgy.

[0012] Resins used in such circuits are selective and chosen to target gold specifically, which is particularly useful with preg-robbing ores. However, secondary or further metals - that is metals other than gold or other precious metals and including base metals such as copper, zinc and nickel - are then left in the leach slurry and lost to the tailings. Alternatively, additional processes and associated cost are required to extract such secondary metals.

[0013] During leaching, cyanide complexes are attracted to the adsorbent, and the rate and amount of adsorption depends on a number of factors.

[0014] Once sufficiently loaded, the adsorbent is removed from the leaching circuit and transferred to an elution and electrowinning circuit, where the gold is eluted or stripped from the adsorbent into pregnant solution, and typically electrowon in an electrowinning cell.

[0015] A problem is encountered where quantities of copper, particularly cyanide soluble copper (CNsolCu) are present in the treated ore.

[0016] Where cyanide soluble copper is present in the ore, it is leached along with the gold. However, leaching of cyanide soluble copper usually requires much greater consumption of cyanide when present in elevated quantity.

[0017] As an example, the cyanide consumption specific to copper is approximately 3kg NaCN per 1kg CNsolCu, which approximates to a similar dollar value of copper and cyanide. Therefore, the leaching of the copper from the ore can consume its own value in cyanide.

[0018] Further problems are encountered in subsequent stages of the recovery process, with copper, in particular, being present on the adsorbent leading to problems with elution and electrowinning (or other) recovery processes. Low levels of copper recovery in the recovery stages often leads to high levels of cyanide copper complexes being directed to tails, with requirement for additional costs for detoxification.

[0019] From a geological perspective, the presence of cyanide soluble copper in an ore body is not always reliably determined, as uneven distribution means that drill samples may not provide a clear indication of the cyanide soluble copper levels present.

[0020] Consequently, many gold plants experience periods of severely limited throughput where quantities of cyanide soluble copper enter into the leach circuit.

[0021] During such periods, consumption of cyanide is significantly increased, and plant throughput may be decreased due to the capacity of a detoxification (‘detox’) circuit to remove the copper or related toxins from the tailings slurry.

[0022] Furthermore, large bodies of ore are known where a detected presence of copper means that extracting and processing the ore is not feasible with known technology.

[0023] The problem can, in part, be overcome with sufficient cyanide consumption, and the emergence of cyanide recycling technologies has led to improvements in the processing of gold ores containing quantities of cyanide soluble copper.

[0024] Flowever, the increased use of cyanide, and the difficulty or unreliability of recovery of copper from the adsorbent has meant that volumes of cyanide soluble copper are present post-processing, which then results in increased costs associated with the cyanide consumption and detox.

[0025] One known method of cyanide recovery, which further removes copper and other base metals, is available as the ReCYN™ process, practised by the present applicant. This process is specific to tailings and enables the recovery and detoxification of tailings by recovering problematic cyanide and residual copper from conventional leach and adsorption plants.

[0026] Flowever, the prior ReCYN™ process is specific to tailings processing, and is commonly commissioned on brownfield sites at additional capital cost, with the aim of increasing efficiency and recovering costs by recycling cyanide and recovering quantities of saleable copper. Further, even if the prior ReCYN™ process is used, the upstream portion of a plant remains conventional, and therefore carries the aforementioned disadvantages.

[0027] The present invention attempts to overcome, at least in part, the aforementioned disadvantages of previous gold recovery circuits by providing a circuit capable of recovering gold and cyanide soluble copper at lower cost than known circuits.

SUMMARY OF INVENTION

[0028] In accordance with one aspect of the present invention, there is provided a gold- copper recovery circuit comprising: an adsorption circuit; and an elution circuit; wherein the adsorption circuit is configured to receive: a slurry containing at least gold and copper in a cyanide solution; and a resin adsorbent; wherein the resin adsorbent is configured to adsorb at least gold, copper and free cyanide; wherein the adsorption circuit comprises a resin offtake to remove resin loaded with at least gold, copper and free cyanide, the resin offtake being configured to separate the loaded resin into a first portion and a second portion; wherein the elution circuit comprises: a copper elution column, wherein the copper elution column is configured to receive the first portion of the loaded resin and a copper eluant, the copper elution column being further configured to remove copper from the loaded resin and to produce a copper pregnant electrolyte solution and a copper eluted resin; a gold elution column configured to receive the copper eluted resin and a gold eluant, wherein the gold elution column is configured to remove gold from the copper eluted resin, and to produce a gold pregnant electrolyte solution and a gold eluted resin; and a cyanide elution column configured to receive the gold eluted resin and the second portion of the loaded resin, and a cyanide eluant, the cyanide elution column being further configured to remove cyanide from the gold eluted resin and the second portion of the loaded resin, and to produce a recovered cyanide solution and discharge resin adsorbent.

[0029] The slurry may, dependent on the ore or concentrate treated in a prior leaching step, also contain further metals such as those selected from the group consisting of precious metals and base metals such as zinc or nickel.

[0030] In accordance with another aspect of the present invention, there is provided a gold recovery circuit comprising: an adsorption circuit; and an elution circuit wherein the adsorption circuit is configured to receive: a slurry containing gold in a cyanide solution; and a resin adsorbent wherein the resin adsorbent is configured to adsorb at least gold and free cyanide; wherein the adsorption circuit comprises a resin offtake to remove resin loaded with gold and free cyanide, the resin offtake being configured to separate the loaded resin into a first portion and a second portion; wherein the elution circuit comprises: a gold elution column configured to receive the first portion of the loaded resin and a gold eluant, the gold elution column being further configured to remove gold from the loaded resin and to produce a gold pregnant electrolyte solution and a gold eluted resin; and a cyanide elution column configured to receive the gold eluted resin and the second portion of the loaded resin, and a cyanide eluant, the cyanide elution column being further configured to remove cyanide from the gold eluted resin and the second portion of the loaded resin, and to produce a recovered cyanide solution and discharge resin adsorbent.

[0031] Preferably, a slurry containing ore comprising at least gold is leached using cyanidation in leach tank(s) before being directed to the adsorption circuit.

[0032] Preferably, the loaded resin is moved through the copper elution column at a greater rate than the gold elution column.

[0033] Preferably, free cyanide is recovered and recycled from the recovered cyanide solution, wherein the recovered free cyanide is then directed to the adsorption circuit and/or the leach tank(s).

[0034] Preferably, the cyanide is recovered and recycled using a conventional cyanide recovery process.

[0035] Preferably, the cyanide recovery process is an acidification - volatilisation - regeneration (‘AVR’) process, resulting in free cyanide and a cyanide barren solution.

[0036] Preferably, the cyanide barren solution resulting from the cyanide recovery process is directed to a further metal electrowinning cell to produce an electrowon metal product from the cyanide barren solution and further metal barren electrolyte solution. The further metal may, for example, be zinc either where a zinc cyanide complex is used as eluant or where zinc is present in a treated ore or concentrate. The further metal may include another base metal.

[0037] Preferably, the further metal (e.g. zinc) barren electrolyte solution contains an acid, typically sulphuric acid (H2SO4).

[0038] Preferably, the further metal (e.g. zinc) barren electrolyte solution is used as the cyanide eluant and is directed to the cyanide elution column.

[0039] Preferably, the gold eluant contains Zn(CN)4.

[0040] Preferably, the copper eluant contains Zn(CN)4. The gold and copper eluants may be the same or different. [0041] Preferably, the gold pregnant electrolyte solution is directed to gold electrowinning cell(s) configured to recover gold from the solution and to discharge a gold barren electrolyte solution.

[0042] Preferably, the copper pregnant electrolyte solution is directed to copper electrowinning cell(s) to remove copper from the solution and to discharge a copper barren electrolyte solution.

[0043] Preferably, the gold barren electrolyte solution is combined with electrowon further metal product, for example zinc product, to form the gold eluant, wherein the gold eluant is fed back to the gold elution column.

[0044] Preferably, the copper barren electrolyte solution is combined with electrowon further metal product, for example zinc product, to form the copper eluant, wherein the copper eluant is fed back to the copper elution column.

[0045] Preferably, the adsorption circuit comprises a plurality of tanks arranged in train, advantageously having a co-current flow. A counter-current flow is not desirable in advantageous embodiments.

[0046] Preferably, the slurry cyanide solution and resin adsorbent are directed to a first tank in the train, wherein each tank conveniently feeds a subsequent tank in the train.

[0047] More preferably, a final tank in the train comprises the resin offtake.

[0048] More preferably, at least one tank comprises an agitation device to agitate or circulate the contents.

[0049] Preferably, the resin is a strong base anionic resin.

[0050] Preferably, the resin offtake comprises a screen configured to retain the resin and allow the slurry to pass.

[0051] Preferably, the resin adsorbent is in the form of beads which may have a diameter of between 0.5mm and 2.0mm, more preferably a diameter of between 1 2mm and 1 6mm. The latter size range facilitates separation by screening at the resin offtake where the resin offtake is a screen. Where a carbon in leach circuit is included, or metals are also recovered by adsorption onto activated carbon, resin bead size above about 1mm allows separation with reduced prospect of contamination by activated carbon.

[0052] Preferably, the resin is pre-conditioned with copper and treated with a mineral acid to enable the resin to adsorb free cyanide.

[0053] In accordance with another aspect of the present invention, there is provided a method of recovering at least gold and copper from an ore body, the method comprising the steps of: a. using cyanidation, desirably alkaline cyanidation, in a leaching circuit to leach at least gold and copper from a slurry containing the ore; b. using a resin adsorbent in an adsorption circuit to adsorb at least gold, copper and free cyanide from the slurry, forming a loaded resin; c. directing a first portion of the loaded resin to a copper elution column, and a second portion of the loaded resin to a cyanide elution column; d. recovering copper from the resin in the copper elution column, and subsequently directing copper eluted resin to a gold elution column; e. recovering gold from the resin in the gold elution column, and subsequently directing gold eluted resin to the cyanide elution column; f. recovering cyanide from the resin in the cyanide elution column, resulting in recovered cyanide and a discharge resin having reduced levels of cyanide; g. returning the discharge resin to the adsorption circuit; and h. recycling the recovered cyanide to the leach or adsorption circuit or to cyanide storage.

[0054] In accordance with a still further aspect of the present invention there is provided a method of recovering gold from an ore body, the method comprising the following steps: a. using cyanidation, desirably alkaline cyanidation, in a leaching circuit to leach gold from a slurry containing the ore; b. using a resin adsorbent in an adsorption circuit to adsorb gold and free cyanide from the slurry, forming a loaded resin; c. directing a first portion of the loaded resin to a gold elution column, and a second portion of the loaded resin to a cyanide elution column; d. recovering gold from the resin in the gold elution column, and subsequently directing gold eluted resin to the cyanide elution column; e. recovering cyanide from the resin in the cyanide elution column, resulting in recovered cyanide and a discharge resin having reduced levels of cyanide; f. optionally conditioning the discharge resin with copper; g. returning the discharge resin to the adsorption circuit; h. recycling the recovered cyanide to the leach or adsorption circuit or to cyanide storage.

BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Further features of the recovery circuits and methods of embodiments of the present invention are more fully described in the following description of several non limiting embodiments thereof. This description is included solely for the purposes of exemplifying the present invention. It should not be understood as a restriction on the broad summary, disclosure or description of the invention as set out above. The description will be made with reference to the accompanying drawings in which:

[0056] Figure 1 is a process flow diagram of a conventional gold recovery circuit showing a leach adsorption train and an elution and electrowinning cycle.

[0057] Figure 2 is a process flow diagram of a copper gold recovery circuit according to one embodiment of the present invention. [0058] Figure 3 is a process flow diagram of a gold recovery circuit according to another embodiment of the present invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

[0059] Referring to Figure 1 , there is shown a conventional gold recovery circuit 1010 including a counter current carbon in leach (CIL) train 1020, with the loaded carbon being directed from the first (upstream) tank to an elution and electrowinning cycle 1030.

[0060] The counter current CIL train 1020 requires an adsorbent (activated carbon in the case of CIL processes as known in the art of gold hydrometallurgy) to be transferred upstream from the final tank 1020a, via each tank 1020b in succession, to the first tank 1020c. The gold loaded carbon is then removed from the first tank 1020c and directed to the elution and electrowinning circuit.

[0061] The slurry 1022 containing ore and the cyanide solution 1024 are added to the first tank 1020c of the train and have the gold removed from the ore by the cyanidation and CIL adsorption process. The slurry 1022, which still retains cyanide and some gold, is then directed to tailings resulting in both environmental and cost problems due to the cyanide remaining in the slurry 1022. Lost gold and possibly further metals of value also represents a cost. Such metals may also be toxic. As detoxification is then necessary, additional cost is incurred for any detoxification processes that are employed.

[0062] Referring to Figure 2, there is shown a gold-copper recovery circuit 10 in accordance with one embodiment of the present invention. Gold-copper recovery circuit 10 includes a number of stages including an adsorption circuit 20 and an elution circuit 30.

[0063] The adsorption circuit 20 receives a slurry 22 containing at least gold and copper (other base and precious metals may be included dependent on minerals present within slurry 22) in an alkaline cyanide solution 24 and a resin adsorbent 100. The process is thus a resin-in-leach (‘RIL’) process. Resin adsorbent 100 is a strong anionic base resin which adsorbs gold, copper and free cyanide. A suitable proprietary resin is commercially available under the trade name Purolite ^® . Resins available under the trade name Amberlite ^® and from other suppliers may also be suitable. [0064] The adsorption circuit 20 further comprises a resin offtake 26 to remove resin loaded with at least gold, copper and free cyanide. Further metals such as base metals or silver may also be adsorbed by the resin.

[0065] The resin offtake 26 is configured to separate the loaded resin into a first portion 110 and a second portion 120.

[0066] The elution circuit 30 comprises a copper elution column 40 which receives the first portion of the loaded resin 110 and a copper eluant 42. The copper elution column 40 functions to remove copper from the loaded resin 110 and to produce a copper pregnant electrolyte solution 44 and a copper eluted resin 46.

[0067] The elution circuit 30 also comprises a gold elution column 50 which receives the copper eluted resin 46 and a gold eluant 52. The gold elution column 50 serves to remove gold from the copper eluted resin 46 and to produce a gold pregnant electrolyte solution 54 and a gold eluted resin 56.

[0068] The elution circuit 30 further comprises a cyanide elution column 60 which receives the gold eluted resin 56, the second portion 120 of the loaded resin and a cyanide eluant 62. The cyanide elution column 60 functions to remove cyanide from the gold eluted resin 56 and the second portion 120 of the loaded resin, producing a recovered cyanide solution 64 and discharge resin adsorbent 100.

[0069] Referring to Figure 3, there is shown a gold recovery circuit 10 according to a further embodiment of the present invention. Gold recovery circuit 10 comprises an adsorption circuit 20 and an elution circuit 30.

[0070] The adsorption circuit 20 receives a slurry 22 containing gold in a cyanide solution 24 and a resin adsorbent 100. Resin adsorbent 100 is a strong anionic base resin, as described above, which adsorbs gold and free cyanide.

[0071] The adsorption circuit 20 further comprises a resin offtake 26 to remove resin loaded with gold and free cyanide. The resin offtake 26 separates the loaded resin into a first portion 110 and a second portion 120.

[0072] The elution circuit 30 comprises a gold elution column 50 and a cyanide elution column 60. [0073] The gold elution column 50 receives the first portion 110 of the loaded resin and a gold eluant 52. The gold eluant 52 conveniently contains Zn(CN)4. Gold elution column 50 removes gold from the loaded resin 110 and produces a gold pregnant electrolyte solution 54 and a gold eluted resin 56.

[0074] The cyanide elution column 60 receives the gold eluted resin 56 and the second portion 120 of the loaded resin and a cyanide eluant 62. The cyanide elution column 60 removes cyanide from the gold eluted resin 56 and the second portion 120 of the loaded resin and produces a recovered solution 64 and a discharge resin adsorbent 100.

[0075] Referring to Figures 2 and 3, free cyanide 24 may be recovered and recycled from the recovered cyanide solution 64. Free cyanide 24 can then advantageously be directed to the adsorption circuit 20 and/or the leach tank(s) (not shown). Free cyanide may be recovered using a conventional cyanide recovery process such as acidification - volatilisation - regeneration (AVR) to provide free cyanide 24 and a cyanide barren solution 63.

[0076] For recovery of zinc from the Zn(CN)4 used as eluant, cyanide barren solution 63 resulting from the cyanide recovery process may be directed to zinc electrowinning cell(s) 65 allowing production of an electrowon zinc product 68 from the recovered cyanide solution 64 and a zinc barren electrolyte solution 66. Other further metals of value, or which may be toxic, may also be removed either by electrowinning or other processes.

[0077] The zinc barren electrolyte solution 66 conveniently contains sulphuric acid (FI2SO4) which can be used as the cyanide eluant 62 and is therefore directed to the cyanide elution column 60. If necessary, the zinc barren electrolyte solution 66 may be further processed before being used as cyanide eluant 62.

[0078] The gold pregnant electrolyte solution 54 may be directed to gold electrowinning cell(s) 55 configured to remove gold 58 from the solution 54, and to discharge a gold barren electrolyte solution 57.

[0079] The gold barren electrolyte solution 57 may be combined with the electrowon zinc product 68 to regenerate the gold eluant 52, wherein the gold eluant 52 is fed back to the gold elution column 50. [0080] The adsorption circuit 20 may comprise a plurality of agitated tanks 20a-20c arranged in a train having, in contrast to the process flow diagram of Figure 1, a co current flow.

[0081] The slurry 22, cyanide solution 24 and resin adsorbent 100 are directed to a first tank 20c in the train wherein each tank 20a and 20b feeds a respective subsequent tank 20a, 20b in the train as shown in Figures 2 and 3.

[0082] Advantageously, the final tank 20a in the train of tanks comprises the resin offtake 26. The resin adsorbent 100 is in the form of beads which, in this embodiment, have diameter between 1.2mm and 1.6mm. The resin offtake 26 conveniently comprises a screen or screened launder which can easily retain the resin adsorbent beads, with diameter 1 2mm and 1 6mm, but allows the slurry to pass through. In other embodiments, the recovery circuit 10 could follow a carbon in leach circuit in which case screening above 1mm reduces prospect of contamination of the resin beads with activated carbon. Other modes of portioning the resin adsorbent could be employed.

[0083] In some cases, the resin adsorbent 100 may be pre-conditioned with copper, and treated with mineral acid, to enable the resin adsorbent 100 to adsorb free cyanide. Flowever, where copper is already present in the resin adsorbent discharged from the cyanide elution column 60, the resin may adsorb free cyanide without such pre conditioning.

[0084] As the second portion 120 of the loaded resin is fed directly to the cyanide elution column 60, copper present in the second portion 120 of the loaded resin will still be present in the resin discharged from the cyanide elution column 60. Consequently, where the ore contains sufficient copper with the result that the resin holds sufficient copper to adsorb free cyanide, pre-conditioning is not required.

[0085] Referring further to Figure 2, where a copper elution column 40 is followed by a gold elution column 50, both columns 40, 50 may conveniently use the same eluant 42, 52. Both the copper eluant 42 and the gold eluant 52 may conveniently contain Zn(CN) .

[0086] The copper may be eluted before the gold, consequently the copper elution column 40 may primarily target the copper, whilst it is recognised that some quantities of gold are also eluted in the copper elution column 40. [0087] Similarly, it is also recognised that some copper may remain in the copper eluted resin 46, which may then be eluted in the following gold elution column 50.

[0088] It is also therefore recognised that some copper and/or gold may be present in the resin adsorbent 100 discharged from the cyanide elution column 60.

[0089] The parameters, including sizing and residence time, of the copper elution column 40 and the gold elution column 50 may be altered to more effectively target the copper and gold in each respective column 40, 50.

[0090] For example, the loaded resin 110 may be moved through the copper elution column 40 at a greater rate than the gold elution column 50.

[0091] The copper pregnant electrolyte solution 44 may be directed to copper electrowinning cell(s) 45 for removal of copper 48 from the solution 44, and to discharge a copper barren electrolyte solution 47. If further metals are present, these may be recovered - where present in sufficient quantity - by electrowinning or other suitable recovery method.

[0092] The copper barren electrolyte solution 47 may be combined with the above described electrowon zinc product 68 to regenerate the copper eluant 42 with the copper eluant 42 being fed back to the gold elution column 50.

[0093] Referring to Figure 3, where levels of copper in an ore body are relatively low, the gold recovery circuit 10 may not require or warrant a copper elution column 40.

[0094] In such cases, the first portion 110 of the loaded resin may be directed to the gold elution column 50 and the second portion 120 of the loaded resin may be directed to the cyanide elution column 60.

[0095] The resin adsorbent 100 discharged from the cyanide elution column 60 may, if necessary, be pre-conditioned with copper with a following mineral acid treatment before being directed to the adsorption circuit 20 to enable the resin to adsorb sufficient free cyanide 24 as described above. Flowever, the gold recovery circuit 10 purposefully does not include a copper recovery stage, such as electrowinning, and thus pre conditioning may not be required. [0096] Turning to the method of operation of circuits 10 as described above with reference to Figures 2 and 3, this may be described as follows. Gold and copper, and potentially further metals, may be recovered from an ore body (whether by treatment of product ore or concentrates) with a method comprising a number of steps.

[0097] The ore is treated using conventional cyanidation in a leach circuit (not shown) to leach gold and copper from a slurry 22 containing the ore and an alkaline cyanide solution.

[0098] Following leaching, the slurry 22 is directed to adsorption circuit 20 to adsorb at least gold, copper and free cyanide using a resin adsorbent 100 to form a loaded resin.

[0099] A first portion 110 of the loaded resin is directed to a copper elution column 40 and a second portion 120 of the loaded resin is directed to a cyanide elution column 60.

[00100] Copper is recovered from the resin adsorbent in the copper elution column 40 and the copper eluted resin 46 is subsequently directed to a gold elution column 50.

[00101] Gold is recovered from the resin in gold elution column 50 and the gold eluted resin 56 is subsequently directed to the cyanide elution column 60.

[00102] The gold eluted resin 56 is eluted in cyanide elution column 60, producing recovered cyanide solution 64 and a discharge resin adsorbent 100 having reduced levels of cyanide.

[00103] The discharge resin adsorbent 100 is returned to the adsorption circuit 20.

[00104] Alternatively, where levels of copper in the ore are sufficiently low that extracting the copper is not economically feasible, gold and cyanide may be recovered from an ore body (whether by treatment of product ore or concentrates) by the following method.

[00105] The ore is treated using conventional cyanidation in a leach circuit (not shown) to leach gold and copper from a slurry 22 containing the ore and an alkaline cyanide solution.

[00106] Following leaching, the slurry is directed to adsorption circuit 20 to adsorb gold and free cyanide using a resin adsorbent 100 to form a loaded resin. Little or no copper is adsorbed in this embodiment. [00107] A first portion 110 of the loaded resin is directed to a gold elution column 50 and a second portion 120 of the loaded resin is directed to a cyanide elution column 60.

[00108] Gold is recovered from resin in the gold elution column and the gold eluted resin 56 is subsequently directed to the cyanide elution column 60.

[00109] The gold eluted resin 56 is eluted in cyanide elution column 60, producing recovered cyanide solution 64 and a discharge resin adsorbent 100 having reduced levels of cyanide.

[00110] Optionally, and if necessary to increase free cyanide adsorption, the discharge resin adsorbent 100 may be pre-conditioned with copper followed by an acid treatment.

[00111 ] The discharge resin adsorbent 100 is returned to the adsorption circuit 20.

[00112] Further steps may involve recovering cyanide 24 from the recovered cyanide solution 64 before recycling the recovered cyanide 24 to the leach circuit or adsorption circuit 20 or to cyanide storage.

[00113] The resin adsorbent 100 may be added to the first tank 20c of the train of the adsorption circuit 20. The slurry 22 containing cyanide solution 24 and gold bearing ore is also added to the first tank 20c in this embodiment. It will be understood that reagents may be added to subsequent tanks in some embodiments.

[00114] The slurry 22 containing cyanide solution 24 and resin adsorbent 100 may travel co-currently from each tank 20c to the subsequent tank 20b and 20a and may pass from one tank to the next by overflow launders or other convenient delivery means. Overflow launders cause slurry 22 from the top of a tank to be passed to a subsequent tank.

[00115] The cyanide solution 24 leaches gold and other metals from the ore in the slurry 22, resulting in a liquor containing free cyanide, metal complexed cyanide and relatively barren slurry solids. The metals may include, in particular, gold and cyanide soluble copper as well as any further metals, for example zinc or other base or precious metals. Copper, which is not cyanide soluble, may not be dissolved and remain in the slurry unless an additional extraction process is used. The requirement for an additional extraction process would typically be dictated by the quantities of non-cyanide soluble copper and the feasibility of recovering such quantities.

[00116] Resin adsorbent 100 adsorbs at least the gold complexed cyanide, the copper complexed cyanide and the free cyanide. The capacity for loading of the resin adsorbent 100 is dictated by the available adsorption sites on the resin molecules, as opposed to the capacity of activated carbon which is once equilibrium is reached. The improved resin capacity for adsorption means that sufficient adsorption can be achieved by a co-current adsorption train in adsorption circuit 20.

[00117] The use of a co-current adsorption circuit 20 removes significant cost from the gold plant because the more conventional counter current design requires intertank screens to prevent the adsorbent travelling down the train and transfer pumps to transfer the adsorbent upstream from one tank to the next.

[00118] The adsorption circuit 20 may also be designed using tanks which are smaller than tanks which would be used in a counter-current circuit of comparative processing capacity. The use of smaller tanks is a further cost saving and requires less space on site.

[00119] The resin offtake 26 is advantageously located on the final tank 20a in the adsorption circuit 20 train. This allows the resin adsorbent 100, in a co-current process, to adsorb free cyanide and metal complexes over a long duration, the duration being the combined residence time of all the tanks in the train.

[00120] Conventional CIL processes involving activated carbon requires the flow of carbon to be counter current to the slurry, which involves greater complexity of the adsorption circuit and requires additional hardware.

[00121] Conventional CIL practice also leaves the cyanide in the slurry which can therefore require additional treatment to recover the cyanide following the adsorption circuit to enable recovery of cyanide before the slurry is directed to tailings.

[00122] Conventional RIP circuits also feature counter current flow of resin and tends to be used more commonly with preg-robbing ores where the selective adsorbent is used to target the gold, but as a result, further or secondary metals remain in the slurry and are directed to tailings where they are lost unless further costly processing is used to recover them.

[00123] The recovery circuits 10 of the present invention recover free cyanide, and a range of potential metal cyanide complexes, leaving a slurry with low levels of toxicity which is sent to tailings with no further processing required. Multiple metals, including zinc as referred to in the above embodiment, can also be removed in the form of cyanide complexes.

[00124] As described above, once removed from the adsorption circuit, the loaded resin is sent to the elution circuit 30. Importantly, the loaded resin is split into two portions before entering the elution circuit 30. The first portion 110 is directed to the copper elution column 40 and the second portion 120 is directed to the cyanide elution column 60. Such separation of the resin into portions 110 and 120 ensures that the second portion 120 of the loaded resin bypasses the copper (where present) and gold elution columns 40, 50 and is directed to the cyanide elution column 60.

[00125] Consequently, where copper is present in sufficient quantity, the copper content of the second portion 120 of loaded resin is not removed from the stream by elution, thus ensuring that a quantity of resin copper retained is returned to the adsorption circuit 20. The copper retained on the resin allows the resin to adsorb free cyanide once returned to the adsorption circuit 20.

[00126] The cyanide may be adsorbed by the resin in the adsorption circuit 20 according to the formula: where R refers to the resin.

[00127] As described in above embodiments, the first portion 110 of loaded resin 110 may undergo two successive elution processes (i.e. gold and copper elution) before being directed to the cyanide elution column 60.

[00128] Alternatively, where copper levels in the ore body do not warrant or require a second elution cycle, the first portion 110 of loaded resin may undergo a single elution process before being directed to the cyanide elution column 60. [00129] Where copper elution is used, the copper pregnant electrolyte solution 44 may then be sent for further processing to remove the copper content, for example by electrowinning in copper electrowinning cell(s) 45, or otherwise, for example by precipitation.

[00130] The copper eluted resin 46 from the copper elution column 40, having had substantial quantities of copper removed is then directed to the gold elution column 50. Gold elution column 50 may be eluted from the resin in substantially conventional manner.

[00131] The gold pregnant electrolyte solution 54 may then have gold recovered by electrowinning in gold electrowinning cell(s) 55.

[00132] The gold eluted resin 56 is transferred to the cyanide elution column 60 in which a further elution process removes the cyanide.

[00133] Cyanide elution in cyanide elution column 60 may proceed according to the formula: where R refers to the resin.

[00134] The recovered cyanide solution 64 may require further processing to recover cyanide of sufficient strength and purity for use in the leach and/or adsorption circuit. The further processing may involve cyanide recovery which may be conducted by conventional means, for example by the acidification - volatilisation - regeneration (AVR) process. The recovered cyanide 24 is then directed to the leach and/or adsorption circuit 20 thereby reducing overhead costs due to cyanide usage.

[00135] The recovery circuits and methods of the present invention allow recovery of gold, copper and free cyanide with lower levels of product loss and lower detox requirements, and therefore lower cost, than prior methods.

[00136] Those skilled in the art will appreciate that the recovery circuits and methods described herein are susceptible to variations and modifications other than those specifically described. The invention includes all such variation and modifications. The invention also includes all of the steps, features, formulations and compounds referred to or indicated in the specification, individually or collectively and any and all combinations or any two or more of the steps or features.

[00137] Throughout this specification, unless the context requires otherwise, the word "comprise" or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.

[00138] The invention described herein may include one or more range of values (e.g. bead size). A range of values will be understood to include all values within the range, including the values defining the range, and values adjacent to the range which lead to the same or substantially the same outcome as the values immediately adjacent to that value which defines the boundary to the range.

[00139] Other definitions for selected terms used herein may be found within the detailed description of the invention and apply throughout. Unless otherwise defined, all other scientific and technical terms used herein have the same meaning as commonly understood to one of ordinary skill in the art to which the invention belongs.