WO2014165937A1

WO2014165937A1 - Apparatus and method for recovery of metals from a body of fluid by electrodeposition

Info

Publication number: WO2014165937A1
Application number: PCT/AU2014/000422
Authority: WO
Inventors: Andrew Baird
Original assignee: Ventseatech Pty Ltd
Priority date: 2013-04-12
Filing date: 2014-04-14
Publication date: 2014-10-16
Also published as: US20160060779A1

Abstract

The present invention relates to apparatus and methods for recovering metals from a body of fluid through the use of electrodeposition techniques, it has particular, although not exclusive application to the recovery of metals from underwater sources, such as oceanic sources, and especially from locations in the vicinity of hydrothermal vents located below the ocean surface. The invention generally provides an apparatus for recovering at least one target mete! substance from a body of a fluid, the apparatus comprising: (a) at least one pair of electrodes (in which each pair comprises a cathode and an anode), such that when the apparatus is used, at least one pair of the electrodes is presented to the body of fluid; and (b) means for generating an electrical potential difference across the at least one pair of electrodes, when at least one of the pairs of electrodes is presented to the body of fluid, so that the potential difference generated across the pair is such as to attract one or more target metal substance present in the body of fluid, for deposition on at least one cathode on the apparatus. The invention also generally provides a method for recovering metals from a body of fluid through the use of electrodeposition techniques and the apparatus described above.

Description

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Apparatus and method for recovery of metals from a body of fluid by eiectrodeposition Field of the invention

The present invention relates to apparatus and methods for recovering metals from a body of fluid through the use of eiectrodeposition techniques, it has particular, although not exclusive application to the recovery of metals from underwater sources, such as oceanic sources, and especially from locations in the vicinity of hydrothermal vents located below the ocean surface.

Background to the invention

Metals have been applied to many uses over the course of human history, and are increasingly of importance to modern commerce and technologies, especially with the modern widespread and growing use of computers and the internet. Copper for example, is nowadays used primarily for making electrical and data transmission cables, and the price per unit weight of copper has increased dramatically since around 2003. Therefore, variations in the cost of producing a unit of a metal species such as copper can have profound economic ramifications tor those who seek to purchase or use the metai. The cost of mining and recovering a metal such as copper can be considerable. Extracting metals from their natural sources (such as from ore deposits) can be a laborious and often a not inexpensive proposition, which is frequently fraught with danger, as episodes such as the Copiapo mining incident (at the San Jose copper-gold mine in Copiapo in Northern Chile in 2010, where 33 miners were trapped about 5 kilometres underground for over 60 days), serve to remind the World,

Most mining operations aimed at recovering metals have historically been, and continue to be, carried out on land. Land-based mining operations are well known and understood, and traditionally have been considered easier to conduct than those in a body of fluid (such as under-sea mining operations, for example). Land-based mining operations that aim to recover metals typically require a great deal of infrastructure and significant amounts of capital. The metallic species recovered from land mined sources typically include sulphides (for example, the metals concerned are either admixed within or complexed with sulphide moieties, or they take the form of sulphide tons of the metals concerned). Many metals that are recovered via land-based techniques include sulphide species, which require significant chemical processing to remove the sulphide ions present in them, and thereby, to yield commercially or technologically useful metals. The chemical removal of sulphide ions from recovered metals is both an expensive process, and one which is environmentally hazardous. It typically necessitates the use of significant quantities of sulphuric acid, which attracts cost, and at the same time, necessitates environmentally acceptable methods of disposing of the used acid.

As an alternative to utilising land-based mining techniques to recover metals, it would be possible in concept to attempt recovering them from underwater sources (e.g., from the surface floor of oceans). In order to contemplate a sub-sea mining technique for recovering metals, a suitable source of recoverable metals must first be found. In this regard, the floors of various oceans throughout the world include structures known as "hydrothermal vents" (which will also be called "sub-sea vents" interchangeably in this specification).

Hydrothermal vents are typically found under the surface of an ocean (at up to a depth of about 6 kilometres) near to geologically active sites, such as in or around areas where tectonic plates abut against and move relative to one another. At such locations, the ambient temperature of the water surrounding such a vent is typically of the order of -2° C to 2° C. A vent is formed when adjacent tectonic plates move and thus diverge from one another, thereby exposing (amongst other things) extremely hot magma exuding from the Earth's core. Such locations are therefore often volcanicaily active. The tectonic plate movement and/or associated volcanic activity results in the ejection of water and other substances from a vent. Water ejected from the vent is typically at a high temperature (this is usually between about 60° and 464° C), and at high pressure {for example, at 375° C and at a depth of 3000 metres below the ocean surface, saline water [which is more dense than fresh water] is at a pressure of up to 300 atmospheres). It is also known that the materials expelled from hydrotherma! vents under these conditions are potentially rich sources of metallic species (including, for example, copper, gold and silver, to name but a few) that originate from within the Earth's core or otherwise from the surrounds of the vent. Those material may contain the metallic species in association with sulphides, but as the materials originate from an aqueous environment (the locus of the deep sea vent), the concentration of sulphur-based materials will generally be tower than in the case of metals derived from land-mined metallic ores.

In theory then, under sea operations aimed at recovering metallic species from in or near a sub-oceanic hydrothermal vent have some appeal, either as an alternative to land-based techniques, or in their own right. To date however, this appeal has been largely theoretical, because recovery operations associated with deep-sea hydrothermal vents encounter a number of significant practical problems, including the following:

(a) the environment in which hydrothermal vents {for example) are found is typically very deep (between 2000 and 6000 metres below the surface of the ocean);

(b) accordingly, those depths alone are such that direct human involvement in the environments concerned is rendered impossible; even at much shallower depths [eg, at depths between about 30 and 300 metres below the surface of the ocean], direct human involvement carries certain serious risks

[these risks include, for example, (1) that the most experienced human scuba divers can descend only as low as about 320 metres below the surface of the ocean at most (and even then, such descents are extremely dangerous); and (2) the potential for human divers to suffer from the physical effects of extreme depth, including nitrogen narcosis, decompression sickness (ie, "the Bends") and oxygen toxicity when seeking to return to the surface from such underwater depths;

(d) as explained earlier, the water temperature at locations in the vicinity of a hydrothermal vent situated at between about 2000 and 6000 metres below the surface of the ocean typically varies from being very cold (about -2° C to 2° C for the ambient water) to being extremely hot (about 80° and 464° C in the case of water ejected from the vent). These extremes of temperature alone pose significant challenges for the logistics of any recovery operation;

(e) in the case of very hot salt water ejected from the vent, as indicated earlier, at depths of 3000 metres below the surface of the ocean, the water is under very great pressure (typically, of the order of 300 atmospheres). When saline water is subjected to a combination of such high pressures and temperatures, it can become what is known as a "supercritical fluid", being one which possesses physical properties between those of a gas and a liquid. This too, presents challenges for recovery operations proposed for use in such extreme environments; and

(f) further, ver hot, supercritical saline water in or near a hydrothermal vent is also typically highly acidic, often having a pH value of approximately 2.8.

This constellation of problems means that devising and operating apparatus and/or methods for the extractive recovery of metal-containing materials from such locations runs into considerable difficulty, for one or more of the reasons previously discussed. In the alternative to using extractive processes at great depths below the surface of an ocean, as the environment in such locations is largety aqueous, the present applicant has conceived the idea of using the physico-chemical technique known as electrodeposition, as a means of recovering metals from such deep sea locations.

Electrodeposition (also known as electroplating) is a physical technique that utilises an electric current in order to facilitate the deposition of cations dissolved in an aqueous solution onto an electrode. Although ocean water - being a saline solution- should provide a suitable medium for conducting an electrodeposition procedure for the purpose of recovering dissolved cations of desired metallic species, in practice, the use of eiectrodeposition runs into serious practical problems. For example, a suitable power source to provide the electrical current required needs to be available at depths several kilometres below the surface of the ocean. It would be wholly impractical to run an eiectricai cable from a Sand based eiectricai power source to such a depth, for one thing. Further, sub-sea vents are often found in locations that are remote from land, it would be equally impractical to run a power cable from a boat or rig to a deep sea recovery apparatus located several kilometres below the water surface. Accordingly, powering a suitable apparatus to such depths is alone a significant obstacle. Secondly, even if suitable means to power such an under- sea electrodepositio technique could be found, there are fundamental questions about whether the technique would work in an environment like that surrounding a hydrothermal vent located several kilometres below the surface of the ocean. For one thing, the physical and chemical characteristics of such locations are extreme. As previously mentioned, the ambient water temperature in such deep sea environments is typically between -2" C to 2° C, whereas in the case of water ejected from the vent, the temperature typically ranges from about 60° C to about 464° C. This is an enormous range. It spans water that is very cold (at even below the freezing temperature of pure water) to wate that is at a temperature which is several times the magnitude of boiling. This range, coupled with the prevailing immense pressure of the water at such depths (the hydrostatic pressure of oceanic water can be up to 300 atmospheres at depths of 3000 metres, as explained previously), places extreme demands on the physical integrity and design of any apparatus that might be used to carry out the proposed eiectrodeposition in deep sea operations, as well as severely limiting the choice of materials from which suitable apparatus for use in the technique might be made. in addition, ocean water in or about the vicinity of deep sea hydrothermai vents is typically not in the same physical state as that found at or near to the ocean's surface, in environments (such as those in or surrounding a deep sea hydrothermai vent) where water is often at extremely elevated pressures and/or temperatures, the water is either in liquid form or frequently, it is in what is called a "supercritical^* state. Supercritical solutions of a fluid possess properties between those of a liquid and of a gas. At depths of 3000 metres below the surface of the ocean and at pressures of 300 atmospheres or greater, sea water reaches its critical point at 407' C, after which it becomes a supercritical fluid, increases in salinity at such depths have the tendency to push water closer to its critical point more easily. Thus, at least some of the water emerging from a deep sea vent will typically be supercriticaL Further, and as indicated earlier, deep sea water in this state is likely to be highly acidic. Whatever apparatus and techniques are adopted for eiectrodeposition in such environments must also accommodate such variations in the physico-chemical properties of the water prevailing in them.

Of necessity, these imponderables additionally impact on the design of, and the materials used to construct any apparatus used to carry out eiectrodeposition in such extreme environments. The prevailing environmental in such environments pose factors pose significant challenges for the design of, and the choice of materials used to carry out electrodeposition-mediated recover of metallic species from deep sea ocean water in the vicinity of a hydrothermai vent. The present invention therefore aims to overcome or alleviate at least one of these prior art problems. Summary of the Invention

The invention generally provides an apparatus for recovering at ieast one target metal substance from a body of a fluid, the apparatus comprising: (a) at least one pair of electrodes (in which each pair comprises a cathode and an anode), such that when the apparatus is used, at ieast one pair of the electrodes is presented to the body of fluid; and (b) means for generating an electrical potential difference across the at least one pai of electrodes, when at Ieast one of the pairs of electrodes is presented to the body of fluid, so that the potential difference generated across the pair is such as to attract one or more target metal substance present in the body of fluid, for deposition on at least one cathode on the apparatus.

The fluid will usually be a liquid. In most embodiments in which the apparatus and method of the invention will be deployed, the fluid will be or contain water. Water for this purpose includes natural and salt water (and combinations thereof, such as the kind of water which might be found where a fresh water source [eg, a river or lake] meets a salt water source [such as an ocean]). The invention may also be used in order to recover one or more target metal substances from other fluids however, and such fluids could (for example) include or contain liquid or gaseous carbon dioxide. For the purposes of the present invention, a "fluid" additionally includes a supercritical fluid, and thus it includes supercritical fiuidic forms of fresh and saline (including sea) water, as well as supercritical aqueous fluids (such as sea water) that include gases (such as carbon dioxide).

In most applications of the invention, the body of fluid is typically a natural sea or an ocean, in which case, the water will be salt water. Alternatively, the body of fluid may be a natural lake or a river or other natural water body. In some embodiments of the invention, at least part of the body of fluid may be man-made. As previously explained, in specific embodiments of the invention, the fluid is from (or from the vicinity of) either a shallow or a deep sea or oceanic hydrothermal vent. The target metal substance is one which is capable of being attracted by electrodeposition onto the cathode of at least one of the pair of electrodes, when an electrical potential difference of sufficient magnitude exists between the cathode and the anode of the pair. Preferred targe metal substances for the purposes of the invention include the following:

(a) Gold

(b) Silver

(c) Copper

(d) Nickel

(e) Iron

(f> Lead

(g) Platinum

(h) Ruthenium

(!) Rhodium

(i) Palladium

(k) Osmium

(1) Iridium

(m) one or more of the Rare Earth Elements of the Periodic Table;

(n) ions, chelates, complexed forms of, colloids and suspensions of, or other substances containing any one of, or combinations of two or more of (a) to (m); as well as

(o) combinations of any two or more of (a) to (n).

At the present time, Platinum, Gold and Palladium are the most commercially valuable target metal substances amongst those listed above. To that extent, they are presently the preferred substances that might be recovered by the use of the apparatus and methods of the invention. Next preferred at this time are the other Platinum Group Elements of the Periodic Table (namely, Ruthenium, Rhodium, Osmium and Iridium). The next preferred substances amongst those mentioned above are presently the Rare Earth Elements. Persons of ordinary skill in the art will readily appreciate that the nature of the preferred target metal substances for this purpose may vary over time, in accordance with technological and commercial developments.

Of necessity, the target metal substance will, in use of the apparatus and method aspects of the invention, be present at Ieast to some degree in cationic form in the body of fluid, so as to be amenable to recovery via electrodeposition.

!n some embodiments of the invention, the apparatus will comprise a main body portion. The body portion of the apparatus may take the form of a frame or other form of housing on which the at least one pair of electrodes is fitted or housed, or with which at least one of the at ieast one pair of electrodes is associated.

in other embodiments, the apparatus might comprise solely one electrode of the pair fitted on a main body or housing for the apparatus and the other electrode of the pair might form part of or take the form of a separate or accessory structure (a "satellite electrode"). In such an alternative embodiment, detent means could be used to retain the satellite electrode within proximity of the main body or housing, so thai in use of the apparatus, the pair of electrodes is able to define an electric field between each electrode. This might be achieved, for example, by generating a magnetic field between the main body or housing and the satellite electrode, so that the latter remains in sufficient proximity to the main body or housing at ail materia! times so that in use of the apparatus, an electric field of sufficient magnitude could be established between the pair of electrodes. Alternatively, in yet other embodiments, the satellite electrode could be linked to the main body or housing of the apparatus via a tethering means, for the same end purpose. in yet further embodiments of this aspect of the invention:

(1 ) the main body or housing could be fitted with more than one pair of electrodes, such that each of which pairs is capable of generating an electrical potential difference between its electrically opposite members; (2) alternatively, the main body or housing could be fitted with two or more instances of a first electrode in a pair, and where each electrode pair comprises a corresponding satellite electrode of opposite polarity within proximity of the main body or housing; or

(3) alternatively, the main body or housing could be fitted with at least one pair of the type of electrodes mentioned in paragraph (1 ) and at least one first electrode of the type mentioned in paragraph (2) and where the at least one or each first electrode has an associated satellite electrode of opposite polarity.

Irrespective of (A) the particular physical form of the body portion in any instance, or (B) the number or configuration of the pairs of electrodes in any embodiment, the apparatus is configured so that at least one of the pairs of electrodes is at least partially immersed in the body of fluid. Preferably further, at least part of the body or housing for the apparatus may be immersed in the body of fluid. In some particularly preferred embodiments, it is even further preferred that the apparatus be capable of being submerged completely within the body of fluid. It is more especially preferred that the apparatus be capable of being submerged to significant depths in the body of fluid.

In most embodiments, the body of fluid is a sea or ocean and comprises at least one floor surface comprising a hydrothermai vent. The apparatus is preferably capable of being submerged to depths of up to 5000 metres below the surface of the ocean, for use in sub-oceanic metal recovery operations. Most hydrothermai vents are located at a depth between 2000 and 5000 metres below the surface of the ocean. In this regard, the so-called "black smoker" sea vents in the Cayman Trough are believed to be the World's deepest hydrothermai vents, and are located at around 5000 metres below sea surface level. However, not all hydrothermai vents are located at these depths (some occur at much shallower depths). Nor is the presence of a hydrothermai vent a necessary pre-condition to the use of the invention. The application of the apparatus and method aspects of the invention is therefore by no means limited to locations where deep sea hydrothermai vents occur, and the present invention can be used at even much shallower depths than 2000 metres below the ocean's surface, and irrespective at any given depth, i l as to whether a hydrothermal vent is present at (or in the vicinity of) a location where the use of the invention is desired. So, for example, the invention may equally be used at depths of about 200 metres below the surface; through to depths as profound as 5000 metres, and whether or not a hydrothermal vent is present at (or in the vicinity of) the desired location or depth in an instance.

Rich sources of recoverable target metal species are known however, often to occur in locations in or proximate to sub-sea vents. Such regions are hostile and unpredictable environments however, in which water temperatures ma range from between -2⁴¹ and 464°C, and so an apparatus for use in the invention would need to be constructed to withstand the extreme physical and chemical demands that are typical of such harsh environments.

At depths of 2000 to 5000 metres below surface level, the embodiments of any suitable recovery apparatus would - amongst other things - need to be capable of withstanding significant water pressures, in the range of 200 to 500 atmospheres. In such embodiments, the apparatus would also need to be constructed from materials that would to enable it to be submerged and kept well beiow the surface of the sea/ocean for extended periods of time. These periods could be anything up to 5 years from the time when the apparatus is submerged in the body of fluid. In most applications however, the period of time could be anything between less than one day (eg, for testing purposes and/or at relatively shallow depths), up to 3 - 5 years. The particular period of time chosen in any instance would be selected according to criteria such as the nature and specific objectives of the particular recovery operation, the geological and environmental characteristics of the particular location in which the apparatus and method of the invention are to be deployed, and the materials from which the apparatus used in any such application is made. Suitable materials for this purpose would however generally be resistant to corrosion, to low pH values (ie, those in the range of from about 1 to 3) and would preferably include:

(a) for the body of the apparatus - powder coated metals such as steel, magnesium and aluminium; and (b) for the electrodes - steel, copper or other conductive metals {the nature of which would readily be apparent to ordinary persons of skill in the art). Particularly preferred materials for the electrodes include metal "wools" (such as "steel wool" and "copper wool"), which increase th surface area of the electrode that comes into contact with the fluid material in which the electrode is immersed. Copper woof is particularly preferred in this regard.

The means for presenting at least one pair of electrodes in or to the body of fluid may take any of a numbe of different forms, including disposing the electrodes on a lower surface of the apparatus, so that of necessity, in most situations, they will preferentially be immersed at least partially in the fluid Biasing the apparatus (eg, through predetermined differentials in weight distribution across the apparatus) so that when the apparatus is being used, the electrodes are at least partially disposed in or immersed in the fluid is another way in which to achieve the desired presentation of the electrodes to or within the fluid.

in most preferred embodiments of the invention however, the apparatus would be completely immersed in the body of fluid, and submerged to significant depths, as previously discussed. Submerging the apparatus to a desired depth and location could be achieved by any number of methods. In some simpler embodiments, this would be achieved by simply weighting the apparatus so that by reason of its weight, it is capable of being submerged to the desired depth, under the operation of gravity. In yet other embodiments, the apparatus could co-operate with a separate mechanism (for example, winch), in order to be installed in a desired location. In yet further embodiments, the apparatus could itself be provided with a motor, so that it can be propelled and directed to a desired location. In this last mentioned set of embodiments, electrical or other means could be used to propel and locate the apparatus in or to the desired location, preferably by remote control. Once installed in the desired location, the apparatus could also be fitted with stabilisation means, to enable it to be physically stabilised so as to operate in situ in the intended environment, without interruption from external forces (such as gravity or strong undersea currents). For this purpose, the apparatus would also preferably comprise features such as (1) leveling means, to ensure that the apparatus could be rested level o an uneven terrain, such as the ocean floor, and/or (2) securement means, such as (for example) one or more anchoring means, to enable it to be anchored at a desired location, so that strong currents or the pressures generated by expulsion of jets of water from hydrothermal vents, would not displace the apparatus such that it is moved away from a desired location or is rendered so as not to be able to operate in the manner intended in situ.

Whichever method is used however, from time to time, the apparatus will need to be retrieved from the environment in which it has been operating, and brought back to the surface of the body of fluid or onto land, for various purposes. These will include (i) most notably, recovery of target metals deposited on the electrodes, (ii) replacement of electrodes or other parts (such as, for example, replacing a generator fitted on the apparatus, or a battery forming part of such a generator) and/or (ii) services, repairs and maintenance. For this reason, the apparatus must be capable of retrieval, either by remote controlled propulsion, or by intervention through the use of a retrieval mechanism (such as a winch cable that is fitted with a hook on its end, and which can be submerged to pick up the apparatus by the hook engaging a mating structure on the apparatus, and then by winching it back to the surface).

The means for generating an electrical potential difference across the at least one pair of electrodes, when the pair of electrodes is presented to the body of fluid, may also take any number of forms, in some embodiments, this would be achieved by providing an electrical generator or battery on or to work in association or co-operation with the apparatus, to generate the potential difference. For this purpose, a generator or battery would need to:

(A) be capable of resisting corrosion, as well as the temperatures, pressures and pH ranges and in the extreme deep sea environments previously mentioned, and in addition, over extended periods (up to 5 years at a time); (B) accordingly, be operable in those environments for periods of up to 5 years at a time; and

(C) be capable of generating a potential, difference across at least one pair of electrodes, of at least 12 Volts when the apparatus is used in the intended environments. Preferably however, the apparatus wouid be capable of generating more than 100 Volts, in some preferred embodiments, the apparatus would be capable of generating anything up to 1000 Volts, because in general (and putting aside the potential impact of other factors or variables) the greater the Voltage that is used, the more rapid will be the electrodeposition of target metal substances on the electrodes.

in some embodiments, the recovery apparatus of the invention would be presented in or to the body of fluid for:

(a) One day;

(b) One month; (c) One year;

(d) Two years;

(e) Three years; or

(f) U to five years from the time when it was first presented to the body of fluid. in embodiments of the invention, the, generator, battery or other source of electrical energy wouid be capable of generating a potential difference of at least:

(a) 12 Volts;

(b) 100 Volts; (c) 200 to 999 Volts; or

(d) 1000 Volts across the at least one pair of electrodes, when used in the body of fluid.

in order to be operable in the harsh deep sea environments in which the Applicant envisages the apparatus would often be used, the generator or battery would normall take the form of a substantially (if not completely) sealed unit or assembly. The Applicant has found that a suitable generator for this purpose is manufactured by Corvus Energy of Canada (whose web site is located at www.corvus-energy.com). In other embodiments, both a generator and a battery (or more than one of each) might be used. In yet other embodiments, and particularly those where the apparatus would be submerged to shallower depths, the means for generating electrical potential difference across the electrodes could include powering the apparatus via an electrical cable connected between the apparatus and an electrical power source located on a boat or on a land source. Due to the depths to which the apparatus would often be submerged in most applications of the invention however, this is a less preferred option to providing the apparatus with a generator or battery.

Where a generator or a battery is provided for use in association with the apparatus, it would be desirable for the apparatus additionally to comprise means for communicating information about its operations to a remote monitoring means. For example, it would be desirable for the apparatus to be provided with radio communications means, so that the apparatus could communicate information about the status of the apparatus to a remote monitor. For this purpose, the apparatus might— for example - comprise sensors for detecting the charge level of a battery included in a generator fitted to the apparatus, so that a computer or a human being on a boat or a remote Sand monitoring system could maintain a watch on the level of the charge of the battery. Similarly, sensors could be provided on the apparatus for monitoring other critical functions, so that warnings could be remitted to a remote monitor when certain parameters were detected. Preferably, the apparatus could also include yet other sensors or detection means (such as, for example, one or more remotely operable video cameras) to enable inspections of the status of the apparatus or its operations to be monitored from a remote monitoring station located either on a water vessel or on land. In such a case, the apparatus coufc! also be fitted with robotic or other remotely operable means for effecting minor repairs to the apparatus. In each of these embodiments, the means for providing the electrical potential difference to the one or more pairs of electrodes (for example, a generator provided on the apparatus) could also power the operation of one or more sensors, detectors, monitoring means (such as video cameras), communications means or repair means provided on or in association with the apparatus, to enable its status and certain operations to be remotely monitored and controlled from a distant location.

The invention also generally provides a method for recovering at least one target metal substance from a body of a fluid, the method comprising the ste s of:

(a) presenting a metal recovery apparatus to a body of fluid, where the apparatus comprises:

(1 ) at least one pair of electrodes (in which each pair comprises a cathode and an anode), such that when the apparatus is used, at least one pair of the electrodes is presented to the body of fluid; and

(2) means for generating an electrical potential difference across the at least one pair of electrodes; and (b) operating the metal recovery apparatus so that at least one of the pairs of electrodes is presented to the body of fluid, and an electrical potential difference is generated across the at least one pair, so that the potential difference is such as to attract one or more target metal substances present in the body of fluid, for deposition on at least one cathode on the apparatus; and (c) recovering the target metal substance from the apparatus. Preferably, the fluid is a liquid. The liquid is preferably water, eithe fresh or salt water.

Preferably, the body of fluid is a natural sea or ocean.

The target metal substance is as previously described, The preferred features of the apparatus are also as previously described.

The means for generating an electrical potential difference across the at least one pair of electrodes are also as previously described.

Preferably, the recovery of the one or more target metal substance(s) from the at least one pair of electrodes involves first, the step of retrieving the apparatus from the body of fluid. Preferably further, the target metal substance(s) is (or are) recovered from the electrodes by techniques that would be known to and readily understood by ordinary persons of skill in the art, including (for example) hydrolysis and electrolytic refining. Hydrolysis techniques generally involve dissolving the recovered target substance (s) in an acidic solution and then changing the pH of the solution gradually over time so as to allow the target metal substance(s) to precipitate out of solution.

Other target metal substances (for example, copper) could be recovered by electrolytic refining, in the use of electrolytic refining to recover copper from a copper-containing body, the copper-containing body is used effectively as the anode in an electrodeposition process, in which a pure copper cathode is used. The electrolyte is typically a copper sulphate solution. By passing electricity through a cell (the cell being defined by these electrodes when immersed in the electrolyte, and when to a source which passes an electric current through the other components of the cell}, pure copper is dissolved from the anode and deposited on the cathode. Impurities from the anode remain either in the electrolyte solution or as insoluble solids in the solution. The nature of these and other techniques for recovering the target meta! suhstance(s) would be understood by and known to persons of ordinary skill in the art. All such suitable techniques are embraced within the scope of the present invention, Brief description of the Drawings

Preferred embodiments of the Invention will now be described by way of example only, with reference to the accompanying drawings, in which:

Detailed description of preferred embodiments of the invention Referring now to the drawings, Fig 1 depicts an apparatus (generally denoted 1 ) for recovering one or more target metal substances from a body of a fluid (denoted generally as 3), such as an ocean, As shown in Fig 1 , the ocean 3 has a floor (generally denoted 5) and the area of ocean floor depicted features a hydrotherma! vent (generally denoted 7).

As depicted in Fig 1 , the exemplary apparatus comprises a body portion (generally denoted 9) which is in the form of a frame (generally denoted 11 ). Configuring the body of the apparatus 1 in the form of a frame means that the apparatus will be of relatively light weight, and will encounter relatively little hydraulic resistance when moving through the water to a desired location. Similarly, retrieving the apparatus 1 from a desired location is enhanced by its relatively light weight and frame-like design.

The body portion 9 comprises a base frame element 13 and an upper frame element 15, In Fig 1 , the apparatus 1 is situated above the ocean floor 5, and is shown as descending towards the ocean floor, where it will engage the floor when it reaches it, The motion of the apparatus 1 towards the ocean floor could be achieved by lowering the apparatus 1 by mechanical means, such as by a winch and cable (not shown in the accompanying drawings) and by weighting the apparatus 1 , or by providing the apparatus with a motor (also not shown in the accompanying drawings) and propelling and guiding it to the desired location (for example, through a remote control mechanism, as previously described in this specification), !n the embodiment of the apparatus shown in the drawings, the apparatus 1 also comprises a crown frame element 17, which is generally in the form of an arch. The crown arch 17 is configured so that it could be releasably secured (for example, by a hook engaging the "eye" portion 19 of the arch) to a winch and cable, to enable the apparatus to be lowered from the surface of the ocean to its desired resting location, and then retrieved at a desired later time.

As shown in Figs 2 and 3, the crown arch 17 of the apparatus may pivot about an axis defined by a spaced apart pair of hinges 21 disposed on the frame 11 of apparatus 1 , from a generally upright orientation (as shown in Fig 1 ) to a generally horizontal orientation (as shown in Figs 2 and 3). In the generally horizontal orientation, the apparatus 1 is more stable in an underwater environment, as it is less likely to be vulnerable to the impact of forces (such as sub-sea seismic activity or ocean currents) of a kind that would tend to move the apparatus 1 laterally or vertically from a static position on the ocean floor. When the crown arch 17 is in the generally horizontal orientation, the vertical height of the apparatus 1 is reduced, thus rendering it less likely to any positional displacement by virtue of the impact of such forces. The movement of the crown arch 17 from the generally upright to the generally horizontal orientation (or vice-versa) could be achieved by either using a remote controllable motorised mechanism to pivot the arch from one orientation to the other, or by using an accessory structure (such as the hook on the end of a winch cable) to raise or lower the crown arch.

As shown in Figs 1 to 3, the body portion of apparatus 1 additionally comprises three legs (each denoted 23). Each leg 23 depends from a central circumferentially extending platform 25 defined by the configuration of the frame 11 of the apparatus 1 . In the embodiment of the apparatus 1 shown in the accompanying drawings, each leg 25 comprises 3 portions. The first is a leg portion proper (denoted 28). Each leg portion has a generally tubular shaft 28 at its distal extremity. Each tubular shaft 28 is designed to receive a vertically extending rod 30 through its bore, where each rod (A) has a foot 27 at its lowermost extremity and (B) at the same time defines an upwardly extending arm at its upper end 32.

The arrangement of these features is such that each rod could be adjusted so as to raise or lower the apparatus 1 vertically along and within the axis A-A defined by each rod 30, so as to stablise the apparatus laterally on the ocean floor or another surface engaged by the feet 27. Each rod 30 is able to be adjusted independently of the other rods. Adjustment of the rods couid be achieved either manually (that is, before the apparatus is immersed initially into the body of fluid, if [for example] the particular resting contour of the ocean floor at a particular desired location is known in advance) or desirably, by remote controlled motorised means, so that lateral stablisation of the apparatus may be achieved (and indeed, customised) in situ as desired in any given instance. Indeed, Figs 2 and 3 depict two different feg configurations for the apparatus 1 , reflecting two different terrains on which such an apparatus might be located. As Fig 1 shows, each foot 27 may also be formed so as to have a ground-penetrating point 33 on its underneath surface, to assist further in locating the apparatus upon, and stabiising the apparatus on the prevailing terrain at a particular location. For this purpose, as discussed previously, the apparatus 1 could also comprise leveling means in order further to stablise it for use at the desired location.

!n the apparatus depicted in the accompanying drawings, the apparatus is shown as having three legs. In alternative embodiments, an apparatus for use in accordance with the invention could have more than three legs, as would be apparent to those of skill in the art. As depicted in each of Figs 1 to 3, the apparatus 1 additionally includes at least one pair of electrodes 34. In each of the drawings, the electrodes 34 comprise at least one pair, in which each pair in turn comprises:

(a) a cathode; and

(b) an anode.

In the embodiments of the apparatus 1 shown i each of Figs 1 to 3, the pairs of electrodes are depicted as forming part of a general eiectrode assembly 35 (which might contain many pair of electrodes). In the illustrated embodiments, the electrode assembly 35 is shown as being of generally cylindrical shape and located or seated on the central platform 25 of the body portion 9 of apparatus 1. in this arrangement, the electrode assembly disposes the electrodes 34 in a generally upright orientation relative to the plane B-B defined by the central platform 25. In alternative embodiments of the invention, the apparatus might be configured differently however. By way of non-limiting example, the following alternatives (amongst other possibilities) might be deployed in particular instances:

(1 ) by providing the recovery apparatus 1 with only one pair of electrodes;

(2) by providing the recovery apparatus 1 with more than one pair of electrodes;

(3) in the case of either (1 ) or (2), by locating the electrodes elsewhere on the apparatus (ie, on a structure other than the central platform 25);

(4) by providing one or more "satellite" electrodes, as described previously in this specification; or

(5) in the case of any of the preceding alternatives, by configuring one or more of the electrodes so as to depend or project downwardly or outwardly relative to the body of the apparatus.

The choice of which of these (or indeed any other suitable) eiectrode configurations is adopted in any instance is a matter that ordinar persons of skill in the art wouid readily be able to resolve.

The apparatus 1 would also be provided with means for generating an electrical potential difference between at least one anode and one cathode fitted on or in association with the apparatus. The nature of the means that could be used to generate an electrical potential difference across at least one anode and one cathode fitted on or in association with the apparatus has previously been discussed. Briefly, an electrical generator or battery wouid be used in most embodiments of the invention, and the battery or generator would either be fitted on the apparatus or would rest on the ocean floor in proximity to the apparatus, in other embodiments, electrical cables connected to an on-land or on-sea vessel source of electrical power could be used, in suitable embodiments (eg, in those embodiments where the depth to which the recov ry apparatus is submerged, is relatively shallow and where the use of an electrical cable or conduit would be practicable. All suitable such means for generating an electrical potential difference across at least one pair of electrodes of opposite polarit fitted onto or in association with the recovery apparatus are however embraced within the scope of the present invention.

As explained earlier in this specification, preferably, a recovery apparatus made in accordance with the invention would also comprise means for sensing or monitoring critical (or even non-criticai) functions of the apparatus, and for communicating information about the operational status of the apparatus (or about any functional parameter concerning the apparatus) to a remote monitoring means located either or land or on a vessel that is capable of operating on the body of fluid (eg, a ship or a submarine). Those sensing, monitoring and communication means would, desirably, co-operate with apparatus or systems provided on the recovery apparatus itself, in order (where appropriate) to actuate a response to a pre-determined state of any monitored parameter of the apparatus. For example, those means could communicate status information to a remote monitoring station and then trigger a response that might alter some operational function on the recovery apparatus (eg, to operate a video camera provided on the apparatus to detect whether the recovery apparatus may have sustained damage requiring repairs).

A recovery apparatus made in accordance with the invention would be used by first eating it at a desired destination or place (eg, by propelling it to a pre-determined sub-sea location that is near to a hydrothermal vent). Once the apparatus has been installed at the desired location and is ready to commence operations, according to the invention, the apparatus is intended to be used to carry out a method for recovering one or more target metal substances present at that location. The method involves:

(a) presenting the recovery apparatus to the body of fluid (eg, sea water in the situation where the body of fluid is an ocean);

(b) (b) operating the metal recovery apparatus so that at least one of the pairs of electrodes on or associated with the recovery apparatus is presented to the body of fluid, and an electrical potential difference is generated across the at least one pair, so that the potential difference is such as to attract one or more target metal substances present in the body of fluid, for deposition on at least one cathode on the apparatus; and

(c) recovering the target metal substance(s) from the apparatus. Recovering the target metal substance(s) from the apparatus involves:

(1 ) retrieving the recovery apparatus when desired, from its operating location; and

(2) recovering the target metal substance(s) from deposits formed on one or more of the cathodes on or associated with the recovery apparatus.

This latter step (step (2)) would involve the use of suitable chemical, physical or physico-chemical techniques for recovering the target metal substance(s). The techniques that could be used for this purpose include electrolytic refining and hydrolysis, as described earlier in this specification.

The nature of suitable materials from which a recovery apparatus in accordance with the invention could be made has been described previously in this specification. So too have the characteristics of suitable materials for making the electrodes for use in the invention. Interpretation of this specification it will therefore be understood that the invention could take many forms and be put to many different uses. All such forms and uses are embodied within the spirit and scope of the invention, which is to be understood as not being limited to the particular constructional details of the embodiments discussed above, but which extends to each novel feature and combination of features disclosed in or evident from this specification and the accompanying claims and drawings. All of these different combinations constitute various alternative aspects of the invention.

It will also be understood that the term "comprises" (or its grammatical variants), as used in this specification, is equivalent in meaning to the term "includes" and should not be taken as excluding the presence of other elements or features. Further, wherever used in this specification, the term "includes" is not a term of limitation, and is not to be taken as excluding the presence of other elements or features. it is further to be understood that any discussion in this specification of background o prior art documents, devices, acts, information, knowledge or use ('Background information') is included solely to explain the context of the invention. Any discussions of such Background Information is not be taken as an admission in any jurisdiction that any such Background Information constitutes prior art, part of the prior art base or the common general knowledge in the field of the invention on or before the priority date of the appended claims or any amended claims later introduced into this specification.

Claims

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:

An apparatus for recovering at least one target metal substance from a body of a fluid, the apparatus comprising:

(a) at least one pair of electrodes (in which each pair comprises a cathode and an anode), such that when the apparatus is used, at least one pair of the electrodes is presented to the body of fluid; and

(b) means for generating an electrical potential difference across the at ieast one pair of electrodes, when at least one of the pairs of electrodes is presented to the body of fluid, so that the potential difference generated across the pair is such as to attract one or more target metal substance present in the body of fluid, for deposition on at Ieast one cathode on the apparatus.

An apparatus as claimed in claim 1 , in which the fluid is a liquid.

An apparatus as claimed in claim 2, in which the fluid is water.

An apparatus as claimed in claim 3, in which the fluid is fresh water.

An apparatus as claimed in claim 3, in which the fluid is salt water.

An apparatus as claimed in claim 3, in which the fluid comprises both fresh water and salt water.

An apparatus as claimed in any one of the claims 1 to 3, 5 or 6, in which the body of fluid is a sea or an ocean.

8. An apparatus as claimed in any one of the preceding claims, in which the body of fluid comprises at Ieast one hydrothermal vent.

9. An apparatus as ciaimed in any one of the preceding ciaims, in which the at least one target metal substance is one which is capable of being attracted by eiectrodeposition onto the cathode of at least one of the pair of electrodes, when an electrical potential difference of sufficient magnitude exists between the cathode and the anode of the pair,

10. An apparatus as claimed in any one of the preceding claims, in which the at least one target metal substance comprises any one of the following:

(a) Gold

(b) Silver

(c) Copper

(d) ickel

(e) Iron

(f) Lead

(g) Platinum

(h) Ruthenium

(i) Rhodium (j) Palladium (k) Osmium (I) Iridium

(m)one or more of the Rare Earth Elements of the Periodic Table; (n) ions, chelates, complexed forms of, colloids and suspensions of, or other substances containing any one of, or combinations of two or more of (a) to (m); and

(o) combinations of any two or more of (a) to (n).

11. An apparatus as claimed in any one of the preceding claims, in which the apparatus comprises a main body portion.

12. An apparatus as ciatmed in claim 1 , in which the main body portion of the apparatus comprises a frame or other form of housing on which the at least one pair of electrodes is fitted or housed, or with which at least one of the at least one pair of electrodes is associated.

13. An apparatus as ciaimed in claim 11 or claim 12, in which the apparatus comprises at least one pair of electrodes of opposed polarity, and in which one of the electrodes in the at least one pair is fitted on the main body portion of the apparatus, and the other electrode is a satellite electrode (as defined in this specification).

14. An apparatus as claimed in any one of claims 11 to 13, in which at least one of the pairs of electrodes is at least partially immersed in the body of fluid

15. An apparatus as claimed in any one of claims 1 1 to 13, in which at least one of the pairs of electrodes is completely immersed in the body of fluid.

16. An apparatus as ciaimed in any one of the preceding claims, in which the capable of being submerged and operated in order to conduct a method of recovering at least one target metal substance at depths of up to 5000 metres below the surface of the body of fluid. 7. An apparatus as claimed in any one of the preceding claims, in which the means for generating an electrical potential difference across the at least one pair of electrodes, when the pair of electrodes is presented to the body of fluid, comprises providing an electrical generator or battery on or to work in association or co-operation with the apparatus, to generate the potential difference. 18. An apparatus as claimed in claim 17, in which the means for generating an electrical potential difference across the at least one pair of electrodes is capable of generating a potential, difference across the at least one pair of electrodes, of at least;

(a) 12 Volts;

(b) 100 Volts;

(c) 200 to 999 Volt!

(d) 1000 Volts when used Sn the body of fluid.

19. An apparatus as claimed in any one of the preceding claims, in which the apparatus is able to be immersed and operated in order to conduct a method of recovering at least one target metal substance from a body of fluid for up to 5 years from the time of initial presentation of the apparatus to the body of fluid.

20. An apparatus as claimed in claim 19, in which the apparatus is able to be immersed and operated in order to conduct a method of recovering at least one target metal substance from a body of fluid for up to

(a) One day;

(b) One month;

(c) One year; (d) Two years; or

(e) Three years from the time of initial presentation of the apparatus to the body of fluid, 21 , A method for recovering at least one target metal substance from a body of a fluid, the method comprising the steps of:

(1) at least one pair of electrodes (in which each pair comprises a cathode and an anode), such that when the apparatus is used, at least one pair of the electrodes is presented to the body of fluid; and

(2) means for generating an electrical potential difference across the at least one pair of electrodes; and (b) operating the metal recovery apparatus so that at least one of the pairs of electrodes is presented to the body of fluid, and an electrical potential difference is generated across the at least one pair, so that the potential difference is such as to attract one or more target metal substances present in the body of fluid, for deposition on at least one cathode on the apparatus; and

(c) recovering the target metal substance from the apparatus