WO2018164578A1

WO2018164578A1 - Combined metal recovery

Info

Publication number: WO2018164578A1
Application number: PCT/NL2018/050145
Authority: WO
Inventors: Roel Johannes Martinus Bisselink; Johan Gerrit Henricus Brouwer
Original assignee: Nederlandse Organisatie voor Toegepast Natuurwetenschappelijk Onderzoek TNO
Current assignee: Nederlandse Organisatie voor Toegepast Natuurwetenschappelijk Onderzoek TNO
Priority date: 2017-03-10
Filing date: 2018-03-09
Publication date: 2018-09-13
Anticipated expiration: 2019-09-10

Abstract

Metal recovery processes for recovering two or more metals from a metal- containing stream are provided. In, Ga, and Mo are recovered in an embodiment using solvent extraction.

Description

COMBINED METAL RECOVERY

The invention relates to the recovery of metals. In an example embodiment, a process is provided for recovering indium, gallium, and molybdenum from CIGS solar panel waste material.

The recovery of indium (In) and gallium (Ga) from streams and solid materials, such as from solar panel waste streams, is a desirable goal because these metals are economically valuable. It is also desired for environmental reasons. In particular, combined recovery of these and other metals from waste streams contributes to realizing a circular economy. In such recovery processes, multiple metals are recovered, each desirably with high purity and efficiency.

US Patent US 8834818 to Ferron (patent application published as

US 2014/0065037 and as WO 2012/068668) describes a hydrometaUurgical process of recovering In and Ga from metallurgical residue material with other metal values, comprising leaching, solvent extraction for In, increasing the pH and solvent extraction for Ga. The process of US 8834818 leaves room for improvement as to the recovery of certain metals, and also as to the purity. The document in particular does not take into account the effects of certain other components present in the pregnant leach solution obtained by the leaching.

An objective of the present invention is to provide a process for the combined recovery of at least In and Ga from a solution containing said metals and other metals, with high purity and efficiency.

The present application accordingly provides, in an aspect, a metal recovery process for recovering at least indium and gallium from a solution comprising at least said metals,

the process comprising providing said solution, optionally by:

a) leaching at least said metals from a solid material into a leaching liquid yielding a Pregnant Leach Solution (PLS) as said solution,

b) solid/liquid separation to remove solid components from said PLS, the process further comprising:

c) solvent extraction to remove indium from said solution, yielding an indium-rich liquid stream and an indium-depleted liquid stream,

d) solvent extraction to remove gallium from the indium-depleted stream,

wherein the process further comprises:

e) solvent extraction for removing molybdenum from the solution upstream of said solvent extraction to remove indium. The process comprises providing a solution comprising dissolved In and Ga, and recovering at least In an Ga from said solution. Generally, the solution that comprises dissolved In and Ga, is a Pregnant Leach Solution (PLS). The process accordingly optionally comprises one or more steps for providing a PLS, usually from a solid material. In particular, the process typically comprises leaching of solid material containing the metals to be recovered, to transfer the metals from the solid material into the liquid. The process typically further comprises solid- liquid separation to separate said material from said liquid, to give a solution (the PLS) having a relatively high concentration of the metals to be recovered.

The solid material typically contains In and Ga, and usually also contains Mo and Zn. The solid material is typically a waste material. The material can be provided in one or more batches and/or with a continuous supply (both can be referred to as "streams"). In a particular embodiment, the solid material is photovoltaic panel waste material, in particular from waste material from copper- indium-gallium-selenium (GIGS) solar panels. CIGS solar panels contain a relatively high amount of In, Ga, Mo and Zn, on metal basis. It is however desired that recovered In and Ga have no or only very low contaminations with in particular Mo and/or Zn.

The process comprises subjecting the solution, e.g. the PLS, to solvent extraction for removing In. Downstream of said solvent extraction for In, the solution is subjected to one or more Ga recovery steps.

In an embodiment of the present invention, Mo is removed from the solution, e.g. PLS, typically upstream of the solvent extraction for removing Ga. Mo is for example removed upstream of the solvent extraction for removing In, or is removed for example as part of the extractant recovery steps of the In solvent extraction. Mo is typically removed by solvent extraction. In this way, compared to US 8834818, the otherwise contaminating effect of Mo on the process is

advantageously avoided.

In further embodiments, contamination of the Ga product is reduced and a higher purity Ga product is obtained. In particular contamination with Zn is avoided. Zn contamination could result from Zn that is also contained in the solid material / waste material. The contamination is avoided by removal of Ga that is more selective for Ga than in e.g. US 8834818.

In an embodiment, the process includes a step for removing molybdate, upstream of the solvent extraction for indium, in particular with an additional solvent extraction step for Mo.

In a number of waste streams that comprise indium, Mo is also present. For example, Mo may be present in solar panel waste streams in more than 50 mg/kg, such as 100 - 200 mg/kg. The material can for instance have a weight ratio Mo:In in the range 5:1 to 1:5, in particular 2: 1 to 1:2. This is for example often the case for CIGS photovoltaic material containing devices and panels.

For example, some CIGS solar panels comprise a CIGS stack between two glass sheets, wherein the CIGS stack is a stack of layers comprising a bottom Mo layer, a CIGS layer, and a transparent conductive oxide top layer. The bottom Mo layer is typically used as cell anode and may furthermore help reflect any unabsorbed light. The top layer can be e.g. an aluminium -doped ZnO layer, operating as cathode. In some embodiments, the process comprises leaching solid material comprising material from the CIGS layer as well as the Mo layer and ZnO based top layer, such that the resulting PLS comprises Zn and Mo besides In and Ga.

The solvent extraction for Mo comprises extraction with an extractant and the process preferably comprises stripping of the Mo loaded extractant. For example an organic extractant is used. The extractant for Mo should have no or limited ability to extract indium and gallium from the solution typically a PLS and typically comprising strong mineral acids, such as nitric acid and sulphuric acid solutions. Suitable extractants for solvent extraction of Mo include Cyanex 272 from Solvay and LIX63 from BASF. LIX63 is 5,8-diethyl-7-hydroxydodecan-6- oxime, usually in a high flash point hydrocarbon diluent. Suitable extractants include e.g. dialkyl phosphinic acid extractant. Cyanex 272 is bis(2,4,4- trimethylpentyl)phosphonic acid. The organic extractant is e.g. stripped with an inorganic hydroxide solution, e.g. alkali metal hydroxide or ammonium hydroxide.

This additional solvent extraction step for Mo elegantly prevents Mo poisoning of organic extractant, such as DEHPA, used in a downstream In solvent extraction step. DEHPA is di-(2-ethylhexyl)phosphoric acid. In particular for DEHPA, stripping with HC1 is efficient for In but not for Mo.

The method of the present embodiment advantageously allows for removing leached Mo. The Mo-rich liquid stream obtained with the additional solvent extraction, e.g. the Mo-rich organic extractant, can be subjected to stripping, such as with a base as stripping agent, for instance with an alkaline solution. Stripping can be carried for example with a hydroxide solution, in particular of an alkali metal hydroxide and/or ammonium hydroxide. The stripping may for instance involve two or more stripping steps in series using the same or a different stripping agent.

This embodiment is further illustrated in Figures 1-3, as solvent extraction step E and as stripping steps M-l and M-2.

In a further embodiment, Mo is removed in another way that can be used alternatively or in combination with solvent extraction for Mo. In this embodiment, the organic extractant of the solvent extraction to remove indium is first stripped to remove indium. Subsequently, the pH is increased, such as by adding an alkaline solution, for example to a pH of at least 4, at least 7, or at least 9. For example the extractant is treated with a hydroxide, e.g. with alkali hydroxide or ammonium hydroxide, to remove molybdenum. Hence, in this embodiment alkaline solution is added to the extractant to strip Mo as anionic molybdate species as aqueous phase. Hence, an aqueous phase comprising anionic molybdate species is obtained. In particular, pH increase causes formation of anionic molybdate species which are stripped into the aqueous phase, and the process typically comprises liquiddiquid separation of the aqueous phase from the organic extractant. Liquid/liquid separation may involve for example gravity -based separators such as settlers and centrifuges. After the removal of the molybdate species, the extractant is again available for use in solvent extraction.

The organic extractant with both In and Mo removed is returned to the solvent extraction for In.

This way of removing Mo can be used as alternative for the solvent extraction for Mo upstream of solvent extraction for In. Accordingly, the present application also provides as independent embodiment a process for removing metals from a solution, preferably a solution as described and provided as described, the process comprising solvent extraction for In with an organic extractant, and removal of Mo from the organic extractant. Preferably the method comprises first stripping the organic extractant to transfer In from the organic extractant to a stripping solution, and then adding alkaline solution to the organic extractant. This method can optionally be combined with the other steps and units as described in this application, especially the steps for removal of Ga.

A further embodiment relates to the solvent extraction of Ga. US 8834818 mentions that the pH can be increased after the In solvent extraction to enable a downstream Ga solvent extraction. Disadvantages of that approach include a higher chemical consumption and difficulties when trying to recycle process streams for recovery of chemicals. The present embodiment addresses these and also provides for high purity.

Accordingly, in a preferred embodiment, the process comprises solvent extraction to remove Ga, downstream of solvent extraction to remove In, wherein the solvent extraction to remove Ga uses octylphenyl acid phosphate (OPAP) as extractant, in particular mono octyphenyl acid phosphate and/or di-octylphenyl acid phosphate (DOPAP), or a mixture thereof. In this embodiment, the pH is preferably not increased by more than 2 between the In solvent extraction and the Ga solvent extraction, preferably not by more than 1.0 or more than 0.50 or more than 0.10. Preferably, the pH of the indium-depleted stream as supplied to Ga solvent extraction is within a range of +0.20 to -0.20 from the pH of said stream as obtained from In solvent extraction, more preferably not more than 0.10 lower or higher (including unchanged pH). In an embodiment, the pH is not increased by more than 0.50 between the In solvent extraction outlet and the Ga solvent extraction inlet in case of a continuous process or between the corresponding steps of a batch process. An advantage of using mono and/or di OPAP is that it enables solvent extraction at a pH where all other metals than Ga (such as Zn) remain essentially in the r affiliate.

This extractant can be used independently or in combination with the solvent extraction for Mo. More generally, the process preferably comprises solvent extraction of Ga downstream of solvent extraction of In at a pH at most 0.50 higher than the In solvent extraction step (e.g. at the same pH) preferably at most 0.20, and more preferably at most 0.10 higher (all including at equal pH), optionally using mono and/or di OPAP as extractant.

Preferably, with mono and/or di OPAP as extractant, the leaching comprises contacting solid material with a solution comprising H2O2 and sulphuric acid, wherein the concentration of sulphuric acid is less than 0.7 M, such as 0.4 - 0.6 M. This was found to give higher purity for Ga than when using 1.0 M sulphuric acid.

Figure 1 illustrates such embodiment, described hereinafter in more detail.

In yet a further embodiment, the recovery of gallium includes precipitated of a Ga-containing solid material. This embodiment can be combined with Mo solvent extraction, but can also be used without Mo-removal. The pH of the In-depleted stream from the In solvent extraction is increased to a pH of 2 or more, preferably 3 or more, usually by adding alkaline solution. The pH of the stream is increased in one or more steps sufficiently to precipitate a solid Ga-comp rising compound, e.g. pH of 5 to 9 or 6 to 8 or 6.5 to 7.5. Preferably at least 50 wt.% of Ga is precipitated, more preferably at least 75 wt.% or at least 95 wt.% or at least 99.0 wt.% of the Ga in the stream. For example, the pH of the indium-depleted liquid stream is increased to pH 6 or higher, resulting in precipitation of at least 90 wt.% of the Ga in said stream. The solid precipitate can be present e.g. as suspension. Thereafter, solid-liquid separation is typically performed, to separate precipitated solid from at least part of the liquid, preferably substantially complete separation (less than 10 wt.% liquid in the solid part). The solid material is then dissolved in hydrochloric acid. Preferably, the solid material is transferred, optionally with part of the liquid, to a separate unit or zone or a unit, e.g. as slurry or as substantially dry solid material. In the separate unit or separate zone in a unit, the Ga in the solid material is dissolved in hydrochloric acid. The resulting Ga -containing solution, in particular gallium chloride solution, can be subjected to solvent extraction, e.g. with an organic extractant such as DIBK (diisobutyl ketone). The extractant is then subjected to stripping e.g. with an aqueous liquid such as water. This embodiment provides for high purity of the obtained Ga. The embodiment is for instance used for GIGS solar panel waste material as the solid material that is leached. In such case, the Ga-rich extractant (e.g. DIBK) contains e.g. less than 50 mg Zn/kg such as less than 40 mg Zn / kg.

Figure 2 illustrates such embodiment, described hereinafter in more detail.

In yet a further embodiment, the process comprises leaching, solvent extraction for Mo and downstream thereof solvent extraction for In, yielding an aqueous stream with low pH that comprises Ga and that is depleted in Mo and In. In this embodiment, the pH of the stream is increased, e.g. to a pH of less than 2, typically more than 0.5 or more than 1.0, e.g. a pH of 0.5 - 1.5, by adding an alkaline solution, e.g. of a hydroxide salt, in particular of an alkali metal hydroxide or ammonia hydroxide. Thereafter, solvent extraction for removal of Ga is carried out, e.g. using DEHPA as extractant. The extractant can for instance be stripped with a mineral acid such as with hydrochloric acid. The stripping liquid loaded with Ga is e.g. subjected to solvent extraction, in particular with an organic extractant, such as with DIBK (diisobutyl ketone). The extractant is then subjected to stripping e.g. with an aqueous liquid such as water. Advantageously, the obtained Ga and In are very pure. Advantageously, the obtained Ga production has very low contamination with Zn in case of GIGS PV panels as solid material source. In a preferred embodiment, the second solvent extraction for Ga uses DIBK as extractant, and the Ga-rich aqueous stream comprises less than 20 mg Zn / kg, more preferably less than 10 mg Zn / kg liquid, or less than 2.0 or less than 1.0 mg Zn / kg.

The indium-rich liquid stream from the In solvent extraction is typically stripped with mineral acid, such as with HQ.

Figure 3 illustrates such embodiment, described hereinafter in more detail.

The leaching of metals from the active layer of CIGS panels may comprise oxidation to oxidize the selenium. An acidic aqueous solution may be used, such as sulphuric acid, for example at 1 - 3 M, e.g. about 2 M. For example other mineral acids and alkaline solutions could also be used. The leaching solution may further comprise an oxidating species, such as added H2O2. For instance, a combination of sulphuric acid and a peroxide compound is used. Nitric acid can also be used, for example without oxidizing species.

The solid material to be leached for example comprises at least 10 mg In/kg, or at least 20 mg In/kg, or at least 50 mg In /kg, based on dry weight of the solid material. The solid material may comprise e.g. at least 10 mg Ga / kg, or at least 20 mg/kg, or at least 50 mg/kg. The solid material may comprise e.g. at least 10 mg Mo / kg, or at least 50 mg/kg, or at least 100 mg/kg of Mo. The slid material may comprise at least 10 mg Zn / kg, or at least 50 mg / kg 70 mg/kg, or at least 100 mg kg of Zn. The solid material may comprise such amounts of In, Ga, Mo, and Zn in combination. The solid material can for instance be provided as fragments having on average such concentrations of these metals and comprising for instance non-uniform fragment particles that can have higher and lower concentrations.

Further suitable waste streams and solid materials include for example parts of copper-indium-gallium (CIG), gallium-indium-zinc oxide (GIZO) and indium-gallium-selenium (IGS) solar panel cells in addition to CIGS solar panel materials.

The solid material that is optionally leached hence preferably comprises photovoltaic material, more preferably an indium and gallium based photovoltaic materials, such as CIGS material. Yet a further aspect relates to a pre-treatment for such metal recovery processes. In a preferred process, the process comprises, prior to the leaching step, a step of dismantlement of solar panels or other electronic waste to remove e.g. cables and frames, providing glass pieces. The process further comprises a thermal treatment step. The thermal treatment step is for example used to remove binder and separate glass layers of said glass piece. The treatment is e.g. at 300 - 600 °C, such as at 400 - 500 °C. The thermal treatment is usually for at least 1 hour at said temperatures, more preferably 2 - 48 h, or 18 - 36 h. The thermal treatment step is usually followed by size separation, such as by sieving. The size separation can be used to separate larger fragment of toughened glass from smaller glass fragments of non-toughened class that are rich in indium and gallium. Hence, fragments from various glass layers of the panel are separated. However, typically the cathode and anode of the solar panels are not separated from the In and Ga comprising photovoltaic material. The present invention elegantly combines this with highly selective recovery of In and Ga.

Preferably, the process comprises before the leaching subjecting glass pieces from GIGS photovoltaic panels to thermal treatment at 450 to 550 °C during 12 to 36 h to remove adhesive comprised in said glass pieces and preferably involve subsequently subjecting the glass pieces to size separation for separating of toughened glass fragments from non-toughened glass fragments comprised in said glass pieces. Separated non-toughened glass fragments can then be leached.

After the leaching, the solid components are furthermore typically removed from the pregnant leach solution (PLS) with a solid-liquid separation step. The solution can then be subjected to removal of metals such as In, Mo, and/or Ga, as described. Also disclosed is a process for recovery of at least In comprising such pre-treatment step, leaching, and solvent extraction to remove In.

The process also typically comprises solvent extraction to remove In.

Generally, solvent extraction comprises removing solutes from a liquid stream through contact with an immiscible liquid (extractant). Solvent extraction involves separating the two immiscible liquids (including keeping the liquids continuously separated from each other). he liquid stream which remains after at least some solutes are removed is the raffinate. The raffinate can be further treated. The extractant is usually regenerated, typically by stripping by contacting with a stripping agent (or strip liquor, or strip liquid) to transfer the solutes to the stripping agent. The recovered extractant is recycled. The extracting liquid may comprise an extractant such as DOPAP mixed with a liquid carrier. The liquid carrier is often a non-polar organic solvent. The liquid carrier may comprise, e.g. for at least 50 wt.% or at least 90 wt.%, of hydrocarbons such as Cll- C14 paraffins and naphthenes. An example is Shellsol™ D70 from Shell Chemicals. Solvent extraction may involve the formation of a complex between the metal ions to be removed and the extractant.

The solvent extraction for In, Ga and Mo comprise, independently, preferably recovery of the extractant comprising stripping.

The solvent extraction, for In, Ga and/or Mo, for example involves pertraction, which is a membrane based solvent extraction technology. Pertraction involves liquid/liquid extraction with transfer of the solutes through a membrane. The membrane prevents the two liquid phases from mixing. The solvent extraction for instance involves slug flow pertraction as described in WO2012177134. The solvent extraction for example comprises a pertraction process for lowering the concentration of one or more target compounds in a feed solution, comprising flowing on a first side of one or more hollow fibre membranes a first liquid comprising extracting agent and a second liquid acting as strip liquid, wherein said first liquid is immiscible with said second liquid, and wherein said first liquid and second liquid flow on the first side of the one or more hollow fibre membranes in a slug flow and wherein at least part of the first liquid is present in pores of the membrane; and contacting the feed solution with the surface of a second side of the one or more hollow fibres.

The spent stripping solution for In solvent extractant, is preferably subjected to electrowinning to cause precipitation of metallic In. In electrowinning, a current is passed from an inert anode through a liquid solution containing the metal so that the metal is deposited in an electroplating process onto the cathode.

Some embodiments of processes according to the invention will now be further described in connection with the drawings (figures). These embodiments and drawings do not limit the invention or the claims. Steps and units for different streams in a figure can be used independently and in combination with each other. For example, processes may comprise units corresponding to different ones of Figures 1-3 in parallel. The particular compositions of streams shown in the drawings (such as acids and solvents) can be varied.

In the figures, percentages "E" are % of the metal that is extracted.

Percentages "P" are % of the metal that is precipitated. Other percentages

(underlined) are purities of the metal (wt.% based on total metals in the stream).

Drawings

Figure 1 shows an example embodiment comprising solvent extraction for Ga. The main steps are: A - dismantlement; B - thermal treatment; C - sieving; D - leaching; E - solvent extraction for Mo, F - solvent extraction for In, G - solvent extraction for Ga, H - In extractant stripping; Ml and M2 - Mo extractant stripping. Steps A, B, and C are each optional, and steps Ml, M2, and H are also each optional.

Herein, CIGS photovoltaic (PV) solar panel (or other solid material) 1 is subjected to dismantlement step A to separate glass fragments 3 from other components 2 such as cable and frames. Dismantlement step A may involve crushing. The glass fragments 3 are subjected to thermal treatment B at 400 - 500 °C, in particular at 450 °C, and the treated glass pieces 4 are subjected to sieving C to remove larger fragments 5, in particular of toughened glass used in CIGS solar panels (e.g. larger than 2 mm). The sieve fraction 6 of smaller glass fragments is supplied to leaching D. In leaching step D, acid 8 is used for leaching, e.g. H2SO4, e.g. at 0.1 - 2.0 M, such as 0.5 - 1.0 M. Leaching liquid 8 comprises e.g. also H2O2, such as 0.1 - 5 wt.%, e.g. about 2 wt.%. Leaching step D also involves solid-liquid separation, for removing solid components 7 from the pregnant leach solution (PLS) 9.

The PLS 9 is subjected to solvent extraction E with organic extractant 10 (e.g. LIX 63) to transfer Mo from the PLS to the extractant. The Mo-rich extractant 12 is partly stripped in stripping unit Ml using stripping liquid 13 yielding spent extractant 15. Spent extractant 15 is for example recycled to step E. The stripping in Ml also yields stripping liquid 16 containing recovered Mo. Another part of Mo- rich extractant 12 is stripped with ammonium hydroxide as stripping liquid 14, yielding spent extractant 17 and a stream 18 containing recovered Mo.

The Mo-depleted solution 11 from the Mo solvent extraction E is subjected to solvent extraction F with organic extractant 19 (DEHPA) to remove In, yielding In-depleted stream 20 and In-rich extractant 21. The In-rich extractant 21 is stripped H with stripping liquid 23, e.g. hydrochloric acid, to yield recovered extractant 22 and the stream 24 containing the recovered In. The In-depleted stream 20 is subjected to solvent extraction G to remove Ga from the stream, using a suitable extractant 25 such as DOPAP. Preferably the pH is not increased between solvent extraction F for removing In and solvent extraction G for removing Ga. The solvent extraction G yields a Ga-rich extractant 27 and a Ga- depleted aqueous stream 26.

An alternative embodiment comprises steps D (leaching), E (solvent extraction for Mo), and downstream thereof, step F (solvent extraction for F). A further embodiment comprises steps D, E and Ml and optionally M2. Figure 2 shows a further example embodiment comprising precipitation of

Ga. Steps A, B, and C, and Ml and M2 are the same as in Figure 1 and are optional. Step D uses a leaching liquid 8 containing a higher concentration LLSO4 , namely 1 M, in addition to 2 wt.% H2O2. Step F is solvent extraction for removal of In, as in Figure I. The In-depleted stream 20 is supplied to step H, where the pH is increased, e.g. to a pH of 2 or more, or 2.5 or more, in particular to pH = 3. This is done, by addition of a suitable base, such as an alkaline solution, in particular of NaOH solution. Stream 26 is e.g. Sn recovered by selective precipitation, by adding alkaline solution 25, such as at pH of about 3 (if Sn is present in the waste material and/or PLS)

Stream 27 comprising Ga from the CISG waste material is supplied to unit J where the pH is increased to e.g. 6 - 8, such as a pH of 7, by addition of a suitable base, such as NaOH. Precipitation of a Ga salt occurs in unit J. The remaining liquid stream 29 is disposed of. Stream 30 comprising precipitated Ga is supplied to unit K, where the pH is decreased and the Ga is dissolved. The Ga comprising liquid stream 32 is supplied to solvent extraction unit L with a suitable extractant 34 such as DIBK. The loaded extractant 35 is stripped in unit N, e.g. with water 37, to yield recovered extractant 36 and a stream 38 comprising Ga.

Figure 3 shows a further example embodiment comprising pH adjustment for Ga recovery.. Steps, A, B, C, D, E, F, H, Ml and M2 are the same as for figure 1. In unit I, the pH is adjusted to a pH of 1. The resulting stream is supplied to solvent extraction in unit O for Ga using a suitable extractant 27 such as DEHPA. The remaining stream 28 is disposed of. The Ga loaded extractant 29 is stripped in unit P with a suitable stripping liquid 30 such as HC1, to yield recovered extractant 31 and a liquid stream 32. The liquid stream 32 is subjected to solvent extraction in unit L with a suitable extractant 34, such as DIPK, to yield spent acid 33 and Ga loaded extractant 35. Extractant 35 is stripped in unit N with water 37 to yield a recovered extractant 36 and a stream 38 containing recovered Ga.

Examples

Embodiments of the invention are now further illustrated in the following examples, which do not limit the invention.

Example 1A

New GIGS PV panels of TSMC solar, type 145CT were purchased and the metal frame was removed by employing mechanical force. The recovered glass consisted of two glass layers adhered to each other probably by ethylene vinyl acetate (EVA) copolymer. Furthermore, the nature of the cracks indicated that one glass layer was toughened (3 mm thick) and the other layer being non-toughened (2 mm thick). Thermal treatment at 450°C during 24 h removed the adhesive and the subsequent size separation (3/8" mesh) allowed separation of toughened and non- toughened glass. The non-toughened glass contained the active CIGS layer. The appearance of white spots is attributed to the transparent conducting oxide (TCO) consisting of zinc oxide which was found to be present in the toughened as well as the non-toughened glass after thermal treatment (see Table 1A). Herein, note 1 denotes predominantly black (B) or white (W) surface. Table 1A illustrates the judicious insight to take into account the actual typical major leachable

components of CIGS PV panels into the design of the process of the invention, especially after mechanical and thermal treatment.

Table 1A

The metals were effectively leached from the obtained CIGS glass with 1 M

H2SO1 + 2% H2O2 using an S/L ratio of 1 at a temperature of 95°C during 24 hours. Filtration of the pregnant leach solution (PLS) using a glass filter enabled separation of liquid from the solid material. The PLS was contacted with an extractant (20% LIX63 in Shellsol D70) during 2 hours with the ratio PLS :

extractant being 1 : 4 under shake conditions. The extraction with LIX63 resulted in complete removal of molybdenum, while other metals remained in the aqueous solution. In the next step the raffinate was contacted with the next extractant (20% DEHPA in Shellsol D70) during 2 hours with the ratio PLS : extractant being 1 : 4 under shake conditions. The extraction with DEHPA resulted in near to complete removal of indium and also the trace amount of tin, while all other metals remained in the aqueous solution. The DEHPA extractant was contacted with a stripping acid (6 M HC1) during 2 hours with the ratio strip acid : extractant being 1 : 2 under shake conditions. Complete stripping of indium was achieved resulting in an indium containing solution with a concentration being a factor 8 higher than the PLS and a purity of 99.5% which is significantly higher than the PLS (16%). Percentages are indium as metal (i.e. In metal concentration divided by total metal concentration); on weight basis.

The SX-DEHPA raffinate was contacted with the third extractant (0.3 M DOPAP (di(octylphenyl)phosphoric acid) in Shellsol D70) during 2 hours with the ratio PLS : extractant being 1 : 4 under shake conditions. DOPAP (purchased as hemi-calcium bis[4-(l, l,3,3-tetramethylbutyl)phenyl] phosphate from Sigma-

Aldrich) was dissolved in Shellsol D70 and converted to the corresponding acid by treatment with HC1. The extraction with DOPAP resulted in 14%) removal of gallium, while all other metals remained in the aqueous solution. Due to the low volume of stripping of the DOPAP extractant was not feasible. Based on simple mass balance calculations the purity of gallium in the organic phase is 91% which is significant increase compared to the PLS (3.4% purity). Table IB shows the metal contents of the liquid at the various steps in this example (corresponding to the liquid streams in case of a continuous process). In these examples, SX indicates solvent extraction. Effective removal of Mo is achieved.

Table IB

Example IB

This example is similar to the first example, except that a less concentrated leaching solution which was used, namely 0.5 M LLSO4 + 2% H2O2. Similar results are obtained for the molybdenum and indium extractions. The gallium extraction is however enhanced resulting in 41% removal and a slightly higher purity of 92%. Table 1C shows the metal contents of the streams in this example.

Table 1C

Example 2

In this example the 0.5 L raffinate of the indium extraction using DEHPA was used as starting material. The pH of the solution was set to pH 7 using 16 M NaOH resulting in complete precipitation of gallium and partial precipitation of the other metals. The precipitate was separated from the solution by means of filtration and washed using demineralized water. The washed precipitate was subsequently dissolved in 50 mL 4.5 M HC1. In the next step the solution was contacted with diisobutyle ketone (DIBK) as extractant during 2 hours with the ratio PLS : extractant being 1 : 4 under shake conditions. The extraction with DIBK resulted in 74% removal of indium and also in part selenium, while all other metals remained in the aqueous solution. The loaded DIBK extractant was contacted with demineralized water during 2 hours with the ratio water: extractant being 1 : 2 under shake conditions. Complete stripping of gallium was achieved resulting in a gallium containing solution with a concentration being a factor 79 higher than the PLS and a purity of 96% which is significantly higher that the PLS (3.4% purity). The metal contents of the liquid streams are shown in Table 2. Note (1): The value for Zn in SX-DIBK strip is based on the analytical detection limit. Table 2

Example 3

In this example the raffinate of the indium extraction using DEHPA was used as starting material. The pH of the solution was set to pH 1 using 16 M NaOH. In the next step the pH 1 solution was contacted with the extractant (20% DEHPA in Shellsol D70) during 2 hours with the ratio PLS : extractant being 1 : 4 under shake conditions. The extraction with DEHPA resulted in 25% removal of gallium and also 5% removal of zinc, while all other metals remained in the aqueous solution. The DEHPA extractant was contacted with a stripping acid (4 M HC1) during 2 hours with the ratio strip acid : extractant being 1 : 2 under shake conditions. Complete stripping of gallium and zinc was achieved. In the next step the solution was contacted with DIBK as extractant during 2 hours with the ratio PLS : extractant being 1 : 4 under shake conditions. The extraction with DIBK resulted in near to complete removal of gallium, while zinc remained in the aqueous solution. The loaded DIBK extractant was contacted with demineralized water during 2 hours with the ratio water: extractant being 1 : 2 under shake conditions. Complete stripping of gallium was achieved resulting in a gallium containing solution with a concentration being a factor 16 higher than the PLS and a purity of >99% which is significantly higher that the PLS (3.4% purity). The stream also has very low Zn contaminations. The metal contents of the streams in this example are shown in Table 3. The process is further illustrated in Figure 3. Table 3

Generally throughout the description, "preferably" indicates a non-essential feature that is optional. Phrases such as "generally", "usually", "suitably", "in particular", "typically", "can", "may" and "usually", and grammatical forms thereof, indicate non-essential features and illustrative or preferred embodiments that do not limit the invention. The term "or" indicates "and/or".

In the figures, flow connections between two units do not exclude further units or steps in between, but a disclosed embodiment is with a direct connection, in particular with no loss or addition of material in any shown flow connection.

The stream is preferably carried out as continuous process but may also be carried out as batch process, wherein references to material streams can be understood as batches. The terms "upstream" and "downstream" are used to encompass both continuous and batch processes. For batch processes, these indicate steps before and after each other. Fractions and percentages are based on weight, unless specified otherwise. For any ranges mentioned as a lower and upper limit, the open-ended ranges "higher than or equal to the lower limit" and "lower than or equal to the upper limit" are also disclosed.

As used herein, the phrases "rich" and "poor" in a metal for liquid stream indicates that the concentration of the metal (e.g. mg/ml) is higher in the rich stream than in the poor stream and higher than in originating stream, and is lower in the poor stream than in the rich stream and lower than in said originating stream. The originating stream is e.g. the stream subjected to solvent extraction.

In some embodiments, the Mo removal is omitted. Hence, the invention also relates to a process for recovery of In and Ga, comprising optionally leaching a solid material, solvent extraction to remove In, and removal of Ga by precipitation and/or solvent extraction as described. In sum, generally described are metal recovery processes for recovering two or more metals from a metal-containing stream are provided. In, Ga, and Mo are recovered in an embodiment using solvent extraction.

Claims

1. A metal recovery process for recovering at least indium and gallium from a solution comprising at least said metals,

the process comprising providing said solution, optionally by:

d) solvent extraction to remove gallium from the indium-depleted stream,

wherein the process further comprises:

e) solvent extraction for removing molybdenum from the solution upstream of said solvent extraction to remove indium.

2. A process according to claim 1, wherein the solid material comprises copper-indium-gallium selenide photovoltaic material.

3. A process according to claim 2, wherein the process comprises said steps a) and b), to give said PLS, and wherein said step e) of solvent extraction for removing Mo is carried out on said PLS.

4. A process according to any of the preceding claims, wherein the solvent extraction to remove indium also involves removal of Mo and comprises:

- solvent extraction to transfer indium from the solution into an organic extractant,

- stripping the extractant to transfer indium from the extractant to an acid solution as aqueous phase,

- thereafter adding alkaline solution to the extractant to strip Mo as anionic molybdate species as aqueous phase, and - liquid/liquid separation to remove the aqueous phase from the organic extractant.

5. A metal recovery process according any of the preceding claims, wherein the solvent extraction to remove gallium from the indium-depleted liquid stream uses mono-octylphenyl acid phosphate, di-octylphenyl acid phosphate, or a mixture thereof, as extractant.

6. A process according to claim 5, wherein the pH is not increased by more than 0.5 between the solvent extraction for In and the solvent extraction for Ga.

7. A metal recovery process according to any of claims 1-5,

further comprising increasing the pH of the indium-depleted liquid stream to precipitate a solid Ga-containing compound.

8. A metal recovery process according to claim 7, wherein the process further comprises:

separating the precipitated solid from at least part of the liquid, dissolving the separated solid in hydrochloric acid, yielding a Ga-containing solution,

solvent extraction of the Ga-containing solution, to yield a Ga-rich extractant, and

stripping the Ga-rich extractant with aqueous stripping liquid.

9. A process according to claim 8, wherein the pH of the indium- depleted liquid stream is increased to pH 6 or higher, resulting in precipitation of at least 90 wt.% of the gallium in said stream.

10. A process according to claim 9, comprising said steps a) and b) of claim 1, wherein the solid material of step a) comprises copper-indium-gallium- selenium (GIGS) solar panel waste material.

11. A process according to claim 10, wherein the solvent extraction for removing Ga uses diisobutyl ketone as extractant and wherein the Ga-rich extractant contains less than 50 mg Zn / kg.

12. A metal recovery process according to any of preceding claims, further comprising increasing the pH of the indium-depleted liquid stream, and solvent extraction of the indium-depleted liquid stream with increased pH to remove Ga, thereby yielding a Ga-rich extractant, and subjecting the Ga-rich extractant to stripping with a mineral acid as stripping liquid, to yield Ga-rich stripping liquid.

13. A metal recovery process according to claim 12,

further comprising subjecting the Ga-rich stripping liquid to a second solvent extraction with an organic extractant, to yield a second Ga-rich extractant, and stripping the second Ga-rich extractant to a second stripping with aqueous stripping liquid to yield a Ga-rich aqueous stream.

14. The process according to claim 13, wherein the second solvent extraction for Ga uses diisobutyl ketone as extractant, and wherein the Ga-rich aqueous stream comprises less than 10 mg Zn / kg.

15. A process according to any of the preceding claims, comprising said step a) of leaching, and before said leaching subjecting glass pieces from GIGS photovoltaic panels to thermal treatment at 450 to 550 °C during 12 to 36 h to remove adhesive comprised in said glass pieces and subsequent size separation for separating toughened from non-toughened glass fragments comprised in said glass pieces, and subjecting separated non-toughened glass fragments to said leaching.