Apparatus for separating entrained aqueous from loaded organic in an SX process

Apparatus for separating a lighter liquid and a heavier liquid may comprise a settling tank sized to receive a mixture of the lighter liquid and the heavier liquid. The settling tank permits the formation of a first upper liquid fraction and a first lower liquid fraction. A weir positioned adjacent the settling tank allows the first upper liquid fraction to flow over the weir. A trough positioned adjacent the weir receives the first upper liquid fraction and effects a secondary separation of the lighter and heavier liquids by allowing the first upper liquid fraction to form a second upper liquid fraction and a second lower liquid fraction. A first drain having an elevated inlet end is positioned in the trough so that the first drain removes the second upper liquid fraction from said trough. A second drain positioned in the trough has an inlet end that is positioned below the inlet end of the first drain so that the second drain removes the second lower liquid fraction from said trough.

FIELD OF INVENTION
 This invention relates to solvent extraction processes in general and more
 specifically to a process for separating the organic phase from the
 aqueous phase in a solvent extraction process for removing copper from raw
 ore.
 BACKGROUND
 The overall efficiency of a copper mining operation depends in part on the
 techniques which are used to separate the copper from the raw ore. Many
 different methods have been developed over time to accomplish copper
 removal with a maximum degree of effectiveness. Of primary interest are
 various techniques which are collectively known as "solvent extraction,"
 or "SX" for short, in which copper ions are leached or otherwise extracted
 from raw ore using chemical agents. Solvent extraction processes for
 removing copper ions are described in detail in U.S. Pat. No. 5,733,431,
 entitled "Method for Removing Copper Ions from Copper Ore Using Organic
 Extractions" which is incorporated herein by reference for all that it
 discloses.
 Most solvent extraction or SX processes currently being used in the copper
 industry utilize a multi-stage process in which the raw ore is first
 contacted with an initial leaching solution or lixiviant. Representative
 lixiviants include, but are not limited to, sulfuric acid, acidic chloride
 solutions, nitrate solutions, ammonia, and ammonium salt compositions. The
 lixiviant leaches copper ions from the ore to generate a lixiviant product
 which consists of a copper ion concentrate (also known as a "pregnant
 leach solution"). The lixiviant product/copper ion concentrate is
 thereafter combined (e.g., mixed) with an organic extractant. The organic
 extractant removes the copper ions from the lixiviant product to generate
 a copper ion-rich organic solution. Many different organic extractants
 exist and may be obtained from any of a wide variety of commercial
 sources. By way of example, most commercially available organic extractant
 compositions typically consist of a mixture containing about 90-95% of a
 petroleum dilutant (e.g., kerosene or tridecanol) and about 5-10%
 hydroxyphenyl oxime. Prior to the combination of the organic extractant
 and the lixiviant product, the organic extractant will contain little or
 no copper ions therein (depending on whether a fresh or recycled
 extractant supply is involved) and is also known as a "barren organic
 extractant." During the mixture of these components, copper ions within
 the lixiviant product are transferred directly into the barren organic
 extractant. As a result, an organic phase and an aqueous phase are
 produced. The organic phase (also known as a "loaded organic extractant")
 consists of the organic extractant which contains copper ions extracted
 from the lixiviant product. The aqueous phase (also known as a
 "raffinate") consists of the lixiviant solution which lacks any
 substantial or appreciable amounts of dissolved copper therein. The
 organic phase is thereafter separated from the aqueous phase and is
 retained for further processing to extract the copper. The aqueous phase
 (i.e., raffinate) may be discarded, stored for future use, or immediately
 reused on additional amounts of ore.
 A significant problem associated with the foregoing process relates to the
 separation of the organic phase (i.e., the loaded organic extractant) from
 the aqueous phase (i.e., the raffinate). While the two phases tend to
 separate into discrete layers based on substantial differences in polarity
 and other physical factors (e.g., specific gravity), as a matter of
 practice, some aqueous tends to remain with the loaded organic extractant
 and vice-versa. The presence of the aqueous phase in the organic phase can
 cause problems later on during the electrowinning process in which the
 copper is plated onto a cathode. For example, in some SX processes, the
 presence of the aqueous phase in the organic phase has the effect of
 transferring chloride into the pregnant electrolyte. In other processes,
 aqueous entrainment in the loaded organic has the effect of transferring
 iron to the pregnant electrolyte. Each contaminate has a negative effect
 on cathode quality, dictates a high plant bleed, and cuts production while
 increasing costs.
 Partly in an effort to solve some of the foregoing problems, some SX
 processes have resorted to the use of coalescers in an attempt to perform
 an additional separation of the aqueous phase from the organic phase.
 While such coalescers are generally effective in removing additional
 amounts of entrained aqueous from the loaded organic, they are expensive
 and can be difficult to operate.
 SUMMARY OF THE INVENTION
 Apparatus for separating a lighter liquid and a heavier liquid may comprise
 a settling tank sized to receive a mixture of the lighter liquid and the
 heavier liquid. The settling tank permits the formation of a first upper
 liquid fraction and a first lower liquid fraction. A weir positioned
 adjacent the settling tank allows the first upper liquid fraction to flow
 over the weir. A trough positioned adjacent the weir receives the first
 upper liquid fraction and effects a secondary separation of the lighter
 and heavier liquids by allowing the first upper liquid fraction to form a
 second upper liquid fraction and a second lower liquid fraction. A first
 drain having an elevated inlet end is positioned in the trough so that the
 first drain removes the second upper liquid fraction from said trough. A
 second drain positioned in the trough has an inlet end that is positioned
 below the inlet end of the first drain so that the second drain removes
 the second lower liquid fraction from said trough.
 Also disclosed is a method for separating a lighter liquid from a heavier
 liquid. First, the lighter liquid and the heavier liquid may be introduced
 into a settling tank and thereafter allowed to form a first upper liquid
 fraction and a first lower liquid fraction. The first upper liquid
 fraction may comprise the lighter liquid with residual amounts of the
 heavier liquid contained therein. The first upper liquid fraction is then
 decanted into a trough. The first upper liquid fraction decanted into the
 trough is then allowed to form a second upper liquid fraction and a second
 lower liquid fraction. The second lower liquid fraction may comprise the
 heavier liquid with residual amounts of the lighter liquid contained
 therein. The second lower liquid fraction is thereafter drained from the
 trough and allowed to form a third upper liquid fraction and a third lower
 liquid fraction.

DETAILED DESCRIPTION OF THE INVENTION
 Liquid separation apparatus 10 for separating a lighter liquid from a
 heavier liquid is shown and described herein as it could be used to
 separate an organic phase (i.e., the lighter liquid) from an aqueous phase
 (i.e., the heavier liquid) in a solvent extraction process for removing
 copper from raw ore. Alternatively, the liquid separation apparatus and
 method according to the present invention could be used in any of a wide
 range of other processes wherein it is necessary or desirable to separate
 a lighter liquid from a heavier liquid.
 Referring to FIGS. 1 and 2, the liquid separation apparatus 10 according to
 one preferred embodiment of the present invention may comprise a settling
 tank 12 sized to receive a mixture of a lighter liquid 14 and a heavier
 liquid 16. By way of example, in one preferred embodiment, the lighter
 liquid 14 may comprise a "loaded organic extractant" (i.e., the organic
 phase) whereas the heavier liquid 16 may comprise a "raffinate" (i.e., the
 aqueous phase). The settling tank 12 effects a first or primary separation
 of the lighter liquid 14 from the heavier liquid 16 in a quiescent zone
 18. The lighter liquid 14 generally rises to the top of the quiescent zone
 18 and forms a first upper liquid fraction 20, whereas the heavier liquid
 16 settles to the bottom of the quiescent zone 18 and forms a first lower
 liquid fraction 22. In most applications, a first interface 24 forms
 between the upper and lower liquid fractions 20 and 22.
 It should be noted that in most applications, a complete separation of the
 lighter and heavier liquids 14 and 16 generally will not occur in the
 settling tank 12. Accordingly, the upper liquid fraction 20 will also
 generally include residual amounts of the heavier liquid 16. That is, the
 upper liquid fraction 20 will generally comprise primarily the lighter
 liquid 14, but with residual amounts of the heavier liquid 16 entrained
 therein. Similarly, the lower liquid fraction 22 will generally comprise
 primarily the heavier liquid 16, but with residual amounts of the lighter
 liquid 14 entrained therein.
 A weir 30 positioned adjacent the outlet end 28 of the settling tank 12
 extends above the level of the first interface 24 separating the first
 upper and lower liquid fractions 20 and 22. Weir 30 allows substantially
 the first upper liquid fraction 20 to be removed (i.e., decanted) from the
 settling tank 12. A trough 26 positioned adjacent the weir 30 receives the
 first upper liquid fraction 20 discharged over the weir 30 and performs a
 secondary separation of the lighter and heavier liquids 14 and 16. That
 is, trough 26 permits the first upper liquid fraction 20 drawn from the
 settling tank 12 to separate into a second upper liquid fraction 20' and a
 second lower liquid fraction 22'. A second interface 24' may form between
 the second upper and lower liquid fractions 20' and 22'. As was the case
 for the first settling tank 12, the separation of the lighter and heavier
 liquids 14 and 16 effected in trough 26 is generally not complete. That
 is, the second lower liquid fraction 22' will generally comprise primarily
 the heavier liquid 16, but with residual amounts of the lighter liquid 14
 contained therein.
 Referring now primarily to FIG. 2, the first trough 26 may be provided with
 a first lighter fraction drain 38 having an inlet end 40 located at an
 elevated position above the floor 42 of trough 26. In one preferred
 embodiment, the elevated inlet end 40 of the first drain 38 is located
 above the second interface 24' contained within trough 26. Accordingly,
 the elevated inlet end 40 of first drain 38 removes from the trough 26
 substantially the second upper liquid fraction 20'. The second upper
 liquid fraction 20' may thereafter be directed to a lighter fraction
 container 62 (FIG. 1) and held for further processing, as will be
 described in greater detail below. Trough 26 may also be provided with a
 pair of sump drains or traps 44 and 46 located on the bottom 42 of trough
 26. The sump drains 44 and 46 are used to remove substantially the second
 lower fraction 22' from the trough 26.
 Each sump drain 44, 46 may be connected to a respective column separator
 48, 50 (FIG. 1), each of which performs a tertiary separation of the
 lighter and heavier liquids 14 and 16. That is, each column separator 48,
 50 permits the second lower liquid fraction 22' drawn from the trough 26
 to form a third upper liquid fraction 20" and a third lower liquid
 fraction 22". The first column separator 48 may be provided with a lighter
 fraction return line 52 for returning to the trough 26 quantities of the
 third upper liquid fraction 20". Column separator 48 may also be provided
 with a drain line 54 for draining the third lower liquid fraction 22" from
 the column separator 48. In one preferred embodiment, the drain line 54
 from column separator 48 may be connected to a second settling tank 56.
 The second column separator 50 may be essentially identical to the first
 column separator 48 and may comprise a lighter fraction return line 58 for
 returning to the trough 26 quantities of the third upper liquid fraction
 20". A drain line 60 may be used to drain to the second settling tank 56
 the third lower liquid fraction 22" from the second column separator 50.
 In the embodiment shown and described herein, the second settling tank 56
 may be used to perform a quaternary separation of the lighter and heavier
 liquids 14 and 16. That is, the second settling tank 56 permits the third
 lower liquid fraction 22" drawn from the column separators 48 and 50 to
 separate into a fourth upper liquid fraction 20"' and a fourth lower
 liquid fraction 22"'. The fourth upper liquid fraction 20"' may thereafter
 be directed to the lighter fraction container 62 and held for further
 processing. The fourth lower liquid fraction 22"' which comprises
 primarily the heavier liquid 16 (e.g., the aqueous phase or raffinate) may
 be withdrawn from the second settling tank 56 and reused or discarded,
 depending on the requirements of the particular process.
 The liquid separation apparatus 10 may also be provided with a heavier
 fraction container or tank 32 that is fluidically connected to the
 settling tank 12 so that the first lower liquid fraction 22 from the
 settling tank 12 flows into the heavier fraction container or tank 32. In
 one preferred embodiment, the container 32 may be provided with a second
 weir 34 which, together with the container 32, defines a second trough 36.
 The second trough 36 may be provided with a drain 64 for removing the
 heavier liquid 16 from the second trough 36. The heavier liquid 16 (e.g.,
 the aqueous phase or raffinate) withdrawn from the second trough 36 may be
 combined with the heavier liquid 16 withdrawn from the second settling
 tank 56 and reused or discarded, as the case may be.
 Operation of the liquid separation apparatus 10 according to the present
 invention may be understood by considering its operation in a solvent
 extraction (i.e., SX) process of the type that may be used to remove
 copper from raw ore. Referring now to FIG. 4, the first step in such a
 process typically involves contacting the raw ore with an initial leaching
 solution or lixiviant. In one preferred embodiment, the lixiviant may
 comprise primarily the heavier liquid 16 or raffinate recovered by the
 liquid separation apparatus 10. Additional amounts of new lixiviant added,
 if necessary, to compensate for process losses. The lixiviant leaches
 copper ions from the raw ore to generate a lixiviant product or "pregnant
 leach solution" 11. Thereafter, the pregnant leach solution 11 may be
 combined with a barren organic extractant 13 in a suitable mixing
 container 15. During the mixture of these components, copper ions
 contained in the pregnant leach solution 11 are transferred directly into
 the barren organic extractant 13. As a result, an organic phase (e.g., the
 lighter liquid 14) and an aqueous phase (e.g., the heavier liquid 16) are
 produced. The organic phase comprises primarily the loaded organic
 extractant (which contains copper ions captured from the pregnant leach
 solution). The aqueous phase (also known as raffinate) comprises primarily
 the lixiviant solution which lacks any substantial or appreciable amounts
 of dissolved copper therein.
 In the foregoing SX process, the organic phase is generally less dense than
 the aqueous phase and the two phases tend to separate into discrete layers
 based on substantial differences in specific gravity and other physical
 factors (e.g., polarity). However, as a matter of practice, some of the
 aqueous phase (i.e., the raffinate) tends to remain with the organic phase
 (i.e., the loaded organic extractant). The liquid separation apparatus 10
 according to the present invention is used to separate the aqueous and
 organic phases.
 Referring back now to FIG. 1, the pregnant leach solution 11 may be
 combined with the appropriate quantity of barren organic extractant 13 in
 a suitable mixing container 15. A mixer or agitator 17 may be used to mix
 together the pregnant leach solution 11 and the barren organic extractant
 13. During mixing, copper ions contained in the pregnant leach solution 11
 are transferred to the barren organic extractant 13, resulting in the
 formation of the organic phase (i.e., the lighter liquid 14) and the
 aqueous phase (i.e., the heavier liquid 16). The two phases (i.e., the
 organic and aqueous) resulting from the mixture of the pregnant leach
 solution 11 and barren organic extractant 13 are thereafter allowed to
 enter the settling tank 12. In the quiescent zone 18, the organic phase
 (i.e., the lighter liquid 14) begins to separate from the aqueous phase
 (i.e., the heavier liquid 16). The result of the separation is the
 formation of the first upper liquid fraction 20 and the first lower liquid
 fraction 22. In the example SX process shown and described herein, the
 first upper liquid fraction 20 will consist primarily of the organic phase
 with residual amounts of the aqueous phase contained therein, whereas the
 first lower liquid fraction 22 will consist primarily of the aqueous phase
 with residual amounts of the organic phase contained therein.
 The first weir 30 permits the first upper liquid fraction 20 contained
 within the quiescent zone 18 of settling tank 12 to be decanted into
 trough 26. The trough 26 effects a secondary separation of the organic and
 aqueous phases by allowing the first upper liquid fraction 20 drawn from
 the settling tank 12 to separate into a second upper liquid fraction 20'
 and a second lower liquid fraction 22'. Generally speaking, the secondary
 separation occurring in trough 26 will not be complete and, as a matter of
 practice, residual amounts of the organic phase will be retained in the
 second lower liquid fraction 22'.
 The second upper liquid fraction 20' is drained from the trough 26 by the
 first lighter fraction drain 38. However, since the inlet end 40 of first
 drain 38 is located above the second interface 24', the first drain 38
 removes primarily only the second upper liquid fraction 20', leaving
 behind the second lower liquid fraction 22'. The second upper liquid
 fraction 20' removed from the trough 26 may thereafter be discharged into
 the lighter fraction container 62 and held for subsequent processing. The
 second lower liquid fraction 22' contained in trough 26 is withdrawn via
 the two sump drains 44 and 46 and thereafter discharged into the two
 respective column separators 48 and 50. Each column separator 48, 50
 effects a tertiary separation of the organic and aqueous phases by
 allowing the second lower liquid fraction 22' drawn from the trough 26 to
 separate into a third upper liquid fraction 20" and a third lower liquid
 fraction 22". The third upper liquid fraction 20" (comprising primarily
 the organic phase, but with some residual aqueous phase contained therein)
 is returned to the trough 26 via the lighter fraction return lines 52 and
 58 associated with the respective column separators 48 and 50. The third
 lower liquid fraction 22" is drained from the column separators 48 and 50
 and is discharged into the second settling tank 56.
 The second settling tank 56 effects a quaternary separation of the organic
 and aqueous phases by allowing the third lower liquid fraction 22" to
 separate into a fourth upper liquid fraction 20"' and a fourth lower
 liquid fraction 22"'. The fourth upper liquid fraction 20"' may be
 directed to the lighter fraction container 62, whereupon it may be held
 for further processing. The fourth lower liquid fraction 22"' may be
 combined with the raffinate removed from the drain 64 associated with the
 second trough 36.
 The loaded organic phase (i.e., the lighter liquid 14) recovered by the
 liquid separation apparatus 10 and contained in tank 62 may thereafter be
 processed to recover the copper ions contained therein by any of a wide
 range of processes that are well known in the art. For example, referring
 back now to FIG. 4, in one preferred embodiment, the loaded organic phase
 14 contained in container 62 may be "stripped" by combining it with a
 suitable electrolyte. The electrolyte strips the copper ions from the
 loaded organic phase to produce barren or "stripped" organic extractant
 and a pregnant electrolyte. The stripped organic extractant may then be
 recycled and reused in the SX process just described. The pregnant
 electrolyte may then be directed into suitable tanks or cells wherein the
 copper ions contained in the pregnant electrolyte are plated onto cathode
 mother blanks in a process commonly referred to as electrowinning.
 However, since such subsequent processing steps (e.g., stripping and
 electrowinning) are well-known in the art and are not required to practice
 the present invention, such subsequent processing steps will not be
 described in further detail herein.
 A significant advantage of the liquid separation apparatus 10 according to
 the present invention is that it effectively removes entrained aqueous
 from the organic phase, thereby reducing or eliminating the problems
 associated with the presence of entrained aqueous in the loaded organic
 phase, including problems associated with the presence of chloride and/or
 iron in the pregnant electrolyte solution. The present invention also
 requires no moving parts, and is thus easy and inexpensive to install and
 maintain.
 Having briefly described the liquid separation apparatus and method
 according to the present invention, as well as some of their more
 significant features and advantages, the various embodiments of the method
 and apparatus for separating a heavier liquid and a lighter liquid will
 now be described in detail. However, before proceeding with the
 description, it should be noted that while the present invention is shown
 and described herein as it could be used to separate the organic phase
 from the aqueous phase in a solvent extraction process for removing copper
 from raw ore, it is not limited to use with any particular process.
 Indeed, the present invention could be used in any of a wide range of
 applications and processes wherein it would be desirable to effect a more
 complete separation of lighter and heavier liquids. Consequently, the
 present invention should not be regarded as limited to the particular
 examples and applications shown and described herein.
 With the foregoing considerations in mind, the liquid separation apparatus
 10 may comprise a settling tank 12 sized to receive the lighter liquid 14
 and the heavier liquid 16. By way of example, in one preferred embodiment,
 the lighter liquid 14 may comprise a loaded organic extractant (e.g., an
 organic phase), whereas the heavier liquid 16 may comprise an aqueous
 phase or raffinate. In the embodiment shown and described herein, the
 settling tank 12 may be integrated with a mixing container 15 in which the
 pregnant leach solution 11 may be combined with the barren organic
 extractant 13. The mixing container 15 may be provided with a mechanical
 mixer or agitator 17 to more thoroughly mix the pregnant leach solution 11
 with the barren organic extractant 13.
 As was discussed above, the mixing of the pregnant leach solution 11 with
 the barren organic extractant 13 results in the formation of a loaded
 organic extractant (i.e., the organic phase) and a raffinate (i.e., the
 aqueous phase). The loaded organic extractant will be referred to
 hereinafter as the lighter liquid 14, whereas the raffinate will be
 referred to hereinafter as the heavier liquid 16. The mixture of the
 lighter and heavier liquids 14 and 16 may be directed to the settling tank
 12 after passing through one or more "picket fences" baffles 66.
 Continuing now with the description, the settling tank 12 extends
 essentially from the picket fence or baffle 66 to an outlet end 28. The
 settling tank 12 includes a quiescent zone 18 therein which permits the
 formation of a first upper liquid fraction 20 and a first lower liquid
 fraction 22. A first interface 24 separates the first upper and lower
 liquid fractions 20 and 22 and generally becomes more defined toward the
 outlet end 28 of settling tank 12.
 The settling tank 12 may comprise any of a wide range of dimensions and
 holding capacities depending on the requirements of the particular process
 in which the liquid separation apparatus 10 is to be employed.
 Consequently, the present invention should not be regarded as limited to a
 settling tank 12 having any particular length, width, and height
 dimensions, nor any particular volume capacity. However, by way of
 example, in one preferred embodiment, the settling tank 12 comprises a
 generally rectangular structure having a length 78 of about 105 feet, a
 height 80 of about 3.5 feet, and a width of about 45 feet. The settling
 tank 12 may be fabricated from any of a wide range of materials (e.g.,
 metals or concretes) suitable for the intended application. By way of
 example, in one preferred embodiment, the settling tank 12 is manufactured
 from 316 stainless steel, although other materials may also be used.
 A weir 30 may be positioned adjacent the outlet end 28 of settling tank 12
 and extends above the level of the first interface 24 separating the first
 upper and lower liquid layers 20 and 22. See FIG. 1. Accordingly, the weir
 30 allows substantially the first upper liquid fraction 20 to be removed
 or decanted from the settling tank 12. By way of example, in one preferred
 embodiment, the weir 30 is located about 8-10 inches above the first
 interface 24, although the weir 30 may be positioned at other locations,
 so long as it is above the level of the first interface 24. A trough 26
 positioned adjacent the weir 30 receives the first upper liquid fraction
 20 discharged over the weir 30. As will be described in greater detail
 below, the trough 26 effects a secondary separation of the lighter and
 heavier liquids 14 and 16 by permitting the first upper liquid fraction 20
 to separate into a second upper liquid fraction 20' and a second lower
 liquid fraction 22'. The second upper and lower liquid fractions 20' and
 22' may become separated by a second interface 24', as shown in FIGS. 1
 and 2.
 The trough 26 may have overall dimensions and a volume capacity
 commensurate with the overall volume flow-rate of the first upper liquid
 fraction 20 that is expected to be produced by the settling tank 12.
 Consequently, the present invention should not be regarded as limited to a
 trough 26 having any particular dimensions or volume capacity. However, by
 way of example, in one preferred embodiment, the first trough 26 may have
 a width 68 (FIG. 2) commensurate with the width of the settling tank 12
 (e.g., about 45 feet) and a length 70 (FIG. 3) of about 39 inches. The
 height 72 of the weir 30 may be about 22 inches, whereas the height 74 of
 the end wall 76 is about 33 inches. The first trough 26 may be made from
 any of a wide range of materials (such as metals or plastics) suitable for
 the intended application. By way of example, in one preferred embodiment,
 the first trough 26 is fabricated from 316 stainless steel.
 The trough 26 may be provided with a first lighter fraction drain 38 having
 an inlet end 40 that is located at an elevated position above the floor 42
 of trough 26. Generally speaking, it will be preferable to position the
 elevated inlet end 40 of the first drain 38 so that it is located above
 the second interface 24' separating the second upper and lower liquid
 fractions 20' and 22', respectively. By way of example, in one preferred
 embodiment, the inlet end 40 of first drain 38 is positioned about 15
 inches above the floor 42 of the trough 26. The first drain 38 may
 discharge into a lighter fraction container 62, as best seen in FIG. 1.
 The trough 26 may also be provided with a pair of sump drains or traps 44
 and 46 located on the bottom 42 of trough 26. In the embodiment shown and
 described herein, the sump drains or traps 44 and 46 are positioned on
 either side of the first drain 38. Alternatively, the sump drains 44 and
 46 may be located at any convenient position along the bottom 42 of trough
 26. In still another arrangement, the sump drains 44 and 46 may be located
 on the lower portions of the sides of trough 26, so long as they are
 located below the second interface 24'. Referring now primarily to FIG. 3,
 the sump drains 44 and 46 are essentially identical and may comprise a
 sump portion 82 that opens into the trough 26. Drain pipes 90, 92
 connected to the respective sump drains 44, 46 may be used to direct
 liquid from the sump drains 44, 46 to the respective column separators 48,
 50.
 The sump drains 44, 46 may be made from any of a wide range of materials,
 such as metals or plastics, suitable for the intended application.
 Moreover, each sump drain 44, 46 may be sized to remove liquid at a rate
 sufficient to prevent the trough 26 from overflowing. Consequently, the
 present invention should not be regarded as limited to sump drains being
 fabricated from any particular material or to any particular size. By way
 of example, in one preferred embodiment, both sump drains 44, 46 are
 fabricated from 316 stainless steel. Each sump drain 44, 46 may have a
 length 84 of about 36 inches, a width 86 of about 4 inches, and a depth 88
 of about 4 inches. Drain pipes 90 and 92 may comprise pipes fabricated
 from PVC (polyvinylchloride) plastic and having diameters of about 2
 inches. Alternatively, pipes fabricated from other materials or having
 different sizes could also be used.
 Referring back now to FIG. 1, each sump drain 44, 46 discharges into a
 respective column separator 48, 50, each of which performs a tertiary
 separation of the lighter and heavier liquids 14, 16 contained in the
 second lower liquid fraction 22' drawn from the trough 26. That is, each
 column separator 48, 50 allows the second lower fraction 22' drawn from
 the trough 26 to form a third upper liquid fraction 20" and a third lower
 liquid fraction 22". A third interface 24" may form between the third
 upper and lower liquid fractions 20" and 22", respectively. The first
 column separator 48 may be provided with a lighter fraction return line 52
 located generally above the third interface 24" for returning to the
 trough 26 quantities of the third upper liquid fraction 20". Column
 separator 48 may also be provided with a drain line 54 for draining the
 third lower liquid fraction 22" from the column separator 48. The drain
 line 54 may discharge the third lower liquid fraction 22" into a second
 settling tank 56. The second column separator 50 may be essentially
 identical to the first column separator 48 and may include a lighter
 fraction return line 58 located above the third interface 24" for
 returning to the trough 26 quantities of the third upper liquid fraction
 20". A drain line 60 may be used to drain to the second settling tank 56
 the third lower fraction 22" from the second column separator 50.
 The first and second column separators 48 and 50 may comprise any of a wide
 range of column separators well-known in the art and that are readily
 commercially available. Consequently, the present invention should not be
 regarded as limited to any particular type or style of column separator.
 By way of example, in the embodiment shown and described herein, each
 column separator 48, 50 may comprise a generally cylindrical member having
 a height of about 5 feet and a diameter of about 8 inches. The column
 separators 48 and 50 may be made from any of a wide range of materials
 suitable for the intended application, as would be obvious to persons
 having ordinary skill in the art. By way of example, each column separator
 48, 50 in one preferred embodiment is fabricated from HDPE (high-density
 polyethylene), although other materials could also be used. The various
 drain lines 52, 54, 58, and 60 may comprise PCV pipes having diameters of
 about 1 inches, although pipes fabricated from other materials and having
 different diameters could also be used.
 The drain lines 54 and 60 from the first and second column separators 48
 and 50 may be connected to the second settling tank 56. The second
 settling tank 56 may be used to perform a quaternary separation of the
 lighter and heavier liquids 14 and 16 contained in the third lower liquid
 fraction 22" drawn from the column separators 48 and 50. That is, the
 second settling tank 56 permits the third lower liquid fraction 22" drawn
 from the column separators 48 and 50 to separate into a fourth upper
 liquid fraction 20"' and a fourth lower liquid fraction 22"'. The fourth
 upper and lower liquid fractions 20"' and 22"' may become separated by a
 fourth interface 24"'. The fourth upper liquid fraction 20"' may
 thereafter be directed to the lighter fraction container 62. The fourth
 lower liquid fraction 22"', which comprises primarily the heavier liquid
 16 (e.g., the aqueous phase or raffinate), may be withdrawn from the
 second settling tank 56 and reused or discarded, depending on the
 requirements of the particular process.
 The second settling tank 56 and the lighter fraction container 62 may
 comprise any of a wide range of containers having sizes suitable for the
 liquid flow rates expected in the particular process. However, since such
 containers are well-known in the art and are readily commercially
 available, the second settling tank 56 and lighter fraction container 62
 utilized in one preferred embodiment of the invention will not be
 described in further detail herein.
 Still referring to FIG. 1, the liquid separation apparatus 10 may also be
 provided with a heavier fraction container or tank 32 that is fluidically
 connected to the settling tank 12 so that the first lower liquid fraction
 22 from the settling tank 12 flows into the heavier fraction container or
 tank 32. In one preferred embodiment, the container 32 comprises an
 integral extension of the settling tank 12, although other configurations
 are possible, as would be obvious to persons having ordinary skill in the
 art. The container 32 may be provided with a second weir 34 which,
 together with the container 32, defines a second trough 36. The second
 trough 36 may be provided with a drain 64 for removing the heavier liquid
 16 from the second trough 36. The heavier liquid 16 (e.g., the aqueous
 phase or raffinate) withdrawn from the second trough 36 may be combined
 with the heavier liquid 16 withdrawn from the second settling tank 56 and
 reused or discarded, as the case may be.
 Operation of the liquid separation apparatus 10 according to the present
 invention may be understood by considering its operation in a solvent
 extraction (i.e., SX) process of the type that may be used to remove
 copper from raw ore. Referring now to FIG. 4, the first step in such a
 process typically involves contacting the raw ore with an initial leaching
 solution or lixiviant. The lixiviant leaches copper ions from the ore to
 generate a lixiviant product or "pregnant leach solution" 11. The pregnant
 leach solution 11 thereafter may be combined with a barren organic
 extractant 13 in container 15. See also FIG. 1. During the mixture of
 these components, copper ions contained in the pregnant leach solution 11
 are transferred directly into the barren organic extractant 13. As a
 result, an organic phase and an aqueous phase are produced. The organic
 phase comprises primarily the loaded organic extractant (which contains
 copper ions captured from the pregnant leach solution). The aqueous phase
 (also known as raffinate) comprises primarily the lixiviant solution which
 lacks any substantial or appreciable amounts of dissolved copper therein.
 In the foregoing SX process, the organic phase is generally less dense than
 the aqueous phase and the two phases tend to separate into discrete layers
 based on substantial differences in specific gravity and other physical
 factors (e.g., polarity). However, as a matter of practice, some of the
 aqueous phase (i.e., the raffinate) tends to remain with the organic phase
 (i.e., the loaded organic extractant). The liquid separation apparatus 10
 according to the present invention is used to separate the aqueous and
 organic phases.
 Referring now to FIG. 1, the pregnant leach solution 11 may be combined
 with the appropriate quantity of barren organic extractant 13 in the
 container 15, whereupon they are mixed together with the aid of the mixer
 or agitator 17. During the mixing process, copper ions contained in the
 pregnant leach solution are transferred to the barren organic extractant
 13 to form the organic phase (i.e., the lighter liquid 14) and the aqueous
 phase (i.e., the heavier liquid 16). The two phases (i.e., the organic and
 aqueous) resulting from the mixture of the pregnant leach solution 11 and
 barren organic extractant 13 are thereafter allowed to enter the settling
 tank 12 after passing through the baffle or "picket fence" 66 separating
 the settling tank 12 from the mixing container 15. Once in the settling
 tank 12, the organic phase (i.e., the lighter liquid 14) begins to
 separate from the aqueous phase (i.e., the heavier liquid 16), ultimately
 forming the first upper liquid fraction 20 and the first lower liquid
 fraction 22. In the example SX process shown and described herein, the
 first upper liquid fraction 20 will consist primarily of the organic phase
 with residual amounts of the aqueous phase contained therein, whereas the
 first lower liquid fraction 22 will consist primarily of the aqueous phase
 with residual amounts of the organic phase contained therein.
 The first weir 30 permits the first upper liquid fraction 20 contained
 within the quiescent zone 18 of settling tank 12 to decant into trough 26.
 The trough 26 effects a secondary separation of the organic and aqueous
 phases by allowing the first upper liquid fraction 20 drawn from the
 settling tank 12 to separate into a second upper liquid fraction 20'
 (comprising primarily the organic phase) and a second lower liquid
 fraction 22' (comprising primarily the aqueous phase). Generally speaking,
 the secondary separation occurring in trough 26 will not be complete and
 residual amounts of the organic phase will be retained in the second lower
 liquid fraction 22'.
 The second upper liquid fraction 20' is drained from the trough 26 by the
 first lighter fraction drain 38. However, since the inlet end 40 of first
 lighter fraction drain 38 is positioned above the second interface 24',
 the first drain 38 removes primarily only the second upper liquid fraction
 20'. The second upper liquid fraction 20' removed from the trough 26 by
 the first drain 38 thereafter may be discharged into the lighter fraction
 container 62 and held for subsequent processing. The second lower liquid
 fraction 22' from trough 26 is withdrawn via the two sump drains 44 and 46
 and thereafter discharged into the two respective column separators 48 and
 50. Each column separator 48, 50 effects a tertiary separation of the
 organic and aqueous phases by allowing the second lower liquid fraction
 22' from the trough 26 to separate into a third upper liquid fraction 20"
 and a third lower liquid fraction 22". The third upper liquid fraction 20"
 (comprising primarily the organic phase, but with some residual aqueous
 phase contained therein) is returned to the trough 26 via the lighter
 fraction return lines 52 and 58. The third lower liquid fraction 22" is
 drained from the column separators 48 and 50 and is discharged into the
 second settling tank 56.
 The second settling tank 56 effects a quaternary separation of the organic
 and aqueous phases by allowing the third lower liquid fraction 22" to
 separate into a fourth upper liquid fraction 20"' and a fourth lower
 liquid fraction 22"'. The fourth upper liquid fraction 20"' may be
 directed to the lighter fraction container 62 and held for further
 processing. The fourth lower liquid fraction 22"' may be combined with the
 raffinate removed from the drain 64 associated with the second trough 36.
 The loaded organic phase (i.e., the lighter liquid 14) recovered by the
 liquid separation apparatus 10 and contained in tank 62 thereafter may be
 processed to recover the copper ions contained therein. For example,
 referring back now to FIG. 4, in one preferred embodiment, the loaded
 organic phase 14 contained in tank 62 may be "stripped" by combining it
 with a suitable electrolyte. The electrolyte strips the copper ions from
 the loaded organic phase to produce barren or stripped organic extractant
 and a pregnant electrolyte. The stripped organic extractant may then be
 recycled and reused in the SX process just described. The pregnant
 electrolyte may then be directed into suitable tanks or cells wherein the
 copper ions contained in the pregnant electrolyte are plated onto cathode
 mother blanks in a process known generally as electrowinning.
 It is contemplated that the inventive concepts herein described may be
 variously otherwise embodied and it is intended that the appended claims
 be construed to include alternative embodiments of the invention except
 insofar as limited by the prior art.