PUDAS JARMO (FI)
| WO2003021708A2 | 2003-03-13 | |||
| WO2005101564A1 | 2005-10-27 |
| EP0620607A1 | 1994-10-19 |
| Claims 1. A method for separation of metals in the black mass of spent alkaline batteries, the method comprising the steps of; a) crushing alkaline batteries and collecting the alkaline black mass resulting from the crushing process, b) magnetically removing ferrous material from the alkaline black mass. c) mixing the alkaline black mass with a leaching solution at acidic pH to dissolve metals present. d) gradually increasing the pH of the leaching solution by addition of a base to selectively precipitating the metals present in the leaching solution as their corresponding metal salts e) collecting the respective precipitates. 2. A method according to claim 1 , wherein the step a) may be preceded by a sorting step to separate alkaline batteries from other battery types such as e.g. lithium re-chargeable batteries. 3. A method according to claims 1 or 2, wherein the leaching solution comprises an acid, such as e.g. a carboxylic acids, sulphuric acid, persulphuric acid (also known as peroxymonosulfuric acid), a sulphonic acid, a sulphinic acid, nitric acid, nitrous acid, phosphoric acid, hypochlorous acid, chlorous acid, chloric acid, perchloric acid, perbromic acid, metaperiodic acid. 4. A method according to any of the preceding claims, wherein the acid is sulphuric acid. 5. A method according to any of the preceding claims, wherein the concentration of the acid in the leaching solution is the range of about 0.1 M to about 10 M, such as e.g. about 0.5 M to about 8M, such as e.g. about 1M to about 6M, such as about 2M to about 4M, or the acid solution may be of a concentration of at least 0.5M, such as e.g. at least about 1M, such as e.g. at least about 2M, such as e.g. at least about 3M such as e.g. at least about 4M, such as e.g. at least about 5M, such as e.g. at least about 6M, such as e.g. at least about 7M, such as e.g. at least about 8M, such as e.g. at least about 9M, such as e.g. at least about 10M. 6. A method according to any of the preceding claims, wherein the concentration of the acid in the leaching solution is about 1 M or such as e.g. about 2M, such as e.g. about 3M, such as e.g. about 4M, such as e.g. about 5M, such as e.g. about 6 , such as e.g. about 7M, such as e.g. about 8M, such as e.g. about 9M, such as e.g. about 10M. 7. A method according to any of the preceding claims, wherein the pH of the acidic leaching solution in step c) is in the range of e.g. about pH = -1 to about pH = 6, such as e.g. about pH = 0 to about pH = 5, such as e.g. about pH = 2 to about pH = 4, such as e.g. about pH = 2 to about pH = 3, or such as e.g. about pH = 1 to about pH = 2, such as e.g. about pH = 2 to about pH = 3, such as e.g. about pH = 3 to about pH = 4, or such as e.g. about pH = 4 to about pH = 5. 8. A method according to any of the preceding claims, wherein the ratio of the alkaline black mass to acid (measured as weight to weight % ratio; w/w %) of e.g. about 1 w/w%, such as e.g. about 5 w/w%, such as e.g. about 10 w/w%, such as e.g. about 15 w/w%, such as e.g. about 20 w/w%, such as e.g. about 25 w/w%, v such as e.g. about 30 w/w%, such as e.g. about 40 w/w%, such as e.g. about 50 w/w%, such as e.g. about 60 w/w%, such as e.g. about 70 w/w%, such as e.g. about 75 w/w%, as long as the molar equivalence of the acids is enough to dissolve the metals. 9. A method according to any of the preceding claims, wherein the reaction mixture during the leaching process may be in the range of e.g. about 5°C to about 100°C, such as e.g. about 10°C to about 90°C, such as e.g. about 20°C to about 80°C, such as e.g. about 30°C to about 70°C, such as e.g. about 40°C to about 60°C, or such as e.g. about 40°C to about 50°C, such as e.g. about 30°C to about 60°C. 10. A method according to any of the preceding claims, wherein the reaction time in the leaching step c) is in the range of e.g. about 30 minutes to about 24 hours, such as e.g. about 1 hour to about 10 hours, such as e.g. about 2 hours to about 3 hours, such as e.g. about 2 hours to about 9 hours such as e.g. about 3 hours to about 8 hours, such as e.g. about 4 hours to about 7 hours, such as e.g. 5 hours to about 6 hours. 11. A method according to any of the preceding claims, wherein the leaching step in c) is performed in presence of a gas such as e.g. oxygen (02) or sulphurdioxide (S02). 12. A method according to any of the preceding claims, wherein the leaching step in c) is performed in presence of a reducing agent such as e.g. hydrogen peroxide (H202) or S02, or it may be e.g. a carboxylic acid (mono-, di- or tri- carboxylic acid) such as e.g. perbenzoic acids such as metha-chloroperbenzoic acid, citric acid, oxalic acid, malonic acid, maleic acid, fumaric acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azaleic acid, tartaric acid, isocitric acid, aconitic acid, propane-1 ,2,3- tricarboxylic acid or trimesic acid or any combinations thereof 13. A method according to any of the preceding claims, wherein the reducing agent is hydrogen peroxide or citric acid. 14. A method according to any of the preceding claims, wherein the concentration of the reducing agent may be in the range of about 0.01 M to about 10 M, such as e.g. about 0.1 M to about 9M, such as e.g. about 0.12 M to about 8.5 , such as e.g. about 0.125 to about 8.45 M, such as e.g. 0.5 M to about 8M, such as e.g. about 1 M to about 6M, such as about 2M to about 4M, or may be of a concentration of at least 0.5M, such as e.g. at least about 1 M, such as e.g. at least about 2M, such as e.g. at least about 3M such as e.g. at least about 4M, such as e.g. at least about 5M, such as e.g. at least about 6M, such as e.g. at least about 7M, such as e.g. at least about 8M, such as e.g. at least about 9M, such as e.g. at least about 10M. 15. A method according to any of the preceding claims, wherein the ratio of the alkaline black mass to reducing agent, measured as weight to weight ratio %; is e.g. about 1 w/w%, such as e.g. such as about 2 w/w %, such as e.g. about 3 w/w%, such as e.g. about 5 w/w%, such as e.g. about 10 w/w%, such as e.g. about 15 w/w%, such as e.g. about 20 w/w%, such as e.g. about 25 w/w%, v such as e.g. about 30 w/w%, such as e.g. about 40 w/w%, such as e.g. about 50 w/w%, such as e.g. about 60 w/w%, such as e.g. about 70 w/w%, such as e.g. about 75 w/w%, as long as the molar equivalence of the acids is enough to dissolve the metals. 16. A method according to any of the preceding claims, wherein the ratio between the weight of alkaline black mass (in grams) to total liquid content in the leaching solution is e.g. about 1/0.5, such as e.g. about 1/1 , such as e.g. about 1/2, such as e.g. about 1/3, such as e.g. about 1/4, such as e.g. about 1/5, such as e.g. about 1/6, such as e.g. about 1/7, such as e.g. about 1/8, such as e.g. about 1/9, such as e.g. about 1/10. 17. A method according to any of the preceding claims, wherein the base in step d) is an organic or inorganic base such as e.g. amines or inorganic hydroxides such as e.g. sodium hydroxide or potassium hydroxide. 18. A method according to any of the preceding claims, wherein the concentration of the base in solution may be in range of at least 0.5 , such as e.g. at least about 1M, such as e.g. at least about 2M, such as e.g. at least about 3M such as e.g. at least about 4M, such as e.g. at least about 5M, such as e.g. at least about 6M, such as e.g. at least about 7M, such as e.g. at least about 8M, such as e.g. at least about 9M, such as e.g. at least about 10M, such as e.g. at least about 11 M, such as e.g. at least about 12M, such as at least about 13M, such as at least about 1 M depending on the based used. 19. A method according to any of the preceding claims, wherein the base is added slowly under controlled conditions while monitoring the pH of the solution and allowing the pH to equilibrate between additions of the base. 20. A method according to any of the preceding claims, wherein the metals present in the leaching solutions comprise zinc and/or manganese as their corresponding sulphates. 21. A method according to any of the preceding claims, wherein zinc is precipitated as zinc hydroxide in a pH interval of about 6.4 to about 6.7. 22. A method according to any of the preceding claims, wherein the manganese is precipitated as manganese hydroxide at a pH interval of about 7.6 to about 11. 23. A method according to any of the preceding claims, wherein the temperature of the leaching solution is about 50°C, the reaction time during leaching is about 3 h, the amount of alkaline black mass is about 20 g, the total volume of the leaching solution is about 100 ml, the concentration of sulphuric acid is about 2 M and the amount of citric acid is about 2.72 g. |
The present application relates to processes for recovery and recycling of metals found in spent alkaline batteries. Thus the processes and methods described herein primarily relates to spent alkaline batteries as opposed to e.g. re-chargeable lithium based batteries.
Background of the invention
Alkaline batteries make up about 80% of all collected spent batteries. Consequently, there is a need and interest of finding process for recovery of the metals used in alkaline spent batteries. Alkaline batteries are primarily batteries consisting mainly of zinc/zinc oxide and manganese dioxide (Zn/ZnO andMn0 2 ). in the alkaline battery, the anode (negative) is made of zinc powder, which gives more surface area for increased current, and the cathode (positive) is composed of manganese dioxide. In the alkaline battery cell (nominal voltage of a fresh alkaline cell is 1.5 V), there is an alkaline electrolyte of potassium hydroxide whereas zinc-carbon batteries have acidic electrolytes.
Half-reactions in the cell are:
Zn (s) + 20H- (aq)→ ZnO (s) + H 2 0 (I) + 2e- 2Mn0 2 (s) + H 2 0 (I) + 2e-→Mn 2 0 3 (s) + 20H- (aq)
On the other hand, dissolution of manganese oxides such as Mn 2 0 3 and Mn 3 0 4 is partial because Mn0 2 produced is insoluble.
Mn 2 0 3 + H 2 S0 4 → Mn0 2 + MnS0 4 + H 2 0
Mn 3 0 4 + H 2 S0 4 →Mn0 2 + 2MnS0 4 + 2 H 2 0 Hence, a reducing agent is required to leach all manganese. The reduction of manganese dioxide and hydrogen peroxide in acidic solution is given as follows:
Mn0 2 + H 2 S0 4 + H 2 0 2 → MnS0 4 + 2H 2 0 + 0 2 Previous related methods presented in the art are exemplified by e.g. EP0620607
Relating to a process in which spent batteries are crushed and the crushed particles are thereafter magnetically treated to separate ferrous material from Hg, Mn, Zn, Cd or Ni. Insoluble residues are then removed by a flotation process. The remaining solid residue is treated with a sulphuric acid solution adjusted to a pH of 2.5-4 to remove Hg. After removal of Hg, the remaining solution is further acidified by addition of more sulphuric acid. The solution is then subjected to electrolysis in which Zn is deposited on the cathode and Mn is deposited on the anode (which is thus the separation of the desired metals).
A further publication, WO 03021708, relates a process in which used cells are crushed and magnetically separated, or being subjected to a thermal treatment, are treated by alkalic attrition to remove any soluble salts (e.g. chlorides). The remaining solid is then leached by sulphuric acid under ultrasonication in presence of a reducing agent (such as e.g. hydrogen peroxide). From the solution is then removed Hg by addition of
2,5.dimercaptothiadiazol or Zn powder). Thereafter heavy metals are removed by Zn cementation (Zn powder under hot thermal conditions). Finally Zn and Mn are separated from of basic or neutral salts (Mn as MnC0 3 and Zn as a Zn-ammonia complex). In WO 05101564 relating to recycling of Li-batteries having an Li-anode and a cathode of Co, Ni, Mn or Fe. The batteries a cry crushed under an inert atmosphere (Argon and/or carbon dioxide). Magnetically separating (to remove any ferrous material) and thereafter hydrolysis in aqueous solution. The lithium metal is precipitated either as lithium phosphate or hexaflurophosphate. It appears that the remaining metals from the cathode are extracted from a 2N sulphuric acid solution at 80C in presence of steel shots, where the ratio of steel shots and powder (from the cathode) is 0.15 and the metals are collected by electrolysis.
An alternative route may be according to an article by Ferella et a/. Journal of Power Sources 183 (2008) 805-811 , suggesting a route where zinc is leached from crushed alkaline batteries using H 2 S0 4 and the remaining carbon and manganese is roasted at 900°C to produce manganese oxides and disposing the carbon residual as carbon dioxide. The zinc solution will contain zinc and sulfuric acid. The article suggests an electro winning (or electroextraction) route for zinc.
However all of the above methods either use electrolysis or use Zn power making them commercially less interesting. Consequently, there is a need for an efficient and cost effective method for recovery of metals present in alkaline batteries.
Description of the invention
Present invention relates to methods for recovery of metals from recycled spent alkaline batteries. Specifically the metals can be e.g. zinc and/or manganese.
In the process of recovery of metals from alkaline batteries a sorting process may optionally be employed as a first step. Such a sorting process has the aim of separating alkaline batteries from any other kinds of batteries such as e.g. re-chargeable lithium batteries. A sorting process that may be employed for this purpose is exemplified in PCT/EP2011/053963 by the same applicant.
In short this process can be described as a batch of mixed batteries entering the process. However, the batches with batteries may also contain non-battery items such as electronic devices containing batteries. Other assorted waste may also be present in these in the batch.
In a first step, the large waste mass to be recycled is sorted manually, to separate batteries from other electronic waste material.
Secondly different types of batteries are sorted and separated from alkaline batteries. These battery types may be lead-, Li-lon polymer-, Ni-Cd-, mercury-, Ni-Metal Hydride-, larger lithium primary, small Lithium primary batteries.
In a third step, the raw material is subjected to a sieve (shaking) system removing so called button cell batteries. This process removes the small lithium primary batteries, also known as button cell batteries. These are round, approximately a half inch in diameter and an eighth of an inch in width. They are used in many consumer electronic products, such as some cameras.
The button cell batteries are removed by passing through a metal "sieve." This sieve consists of approx. 15 V-shaped metal ridges, which are all connected such that the same piece of metal forms the left side of one ridge and the right side of another ridge. The left and right sides are at an approximately 45 degree angle such that any small object would fall to the middle of each ridge. The side of each ridge is approximately one inch long. The bottom of each ridge, what one could call the bottom of the "V," is empty. It is an open slot approximately one-quarter of an inch wide. Thus any small button cell battery which was on top of the "V" would slide to the bottom of the ridge, and then through it.
The metal bars which form the left side of one "V" and the right side of another are approximately each 10 feet long. These metal bars are placed directly next to the rubber conveyer belt of equal width. The batteries, when they first come into the plant, are placed on this conveyer belt and sorted as described above.
During the manual sorting step as described above, the smaller lithium button cell batteries are not dealt with. They remain on the conveyer belt and thus pass from the conveyer belt to the metal "V" shaped ridges. The bars which form the sides of the ridges shake at a moderate pace. This encourages the smaller batteries to fail to the bottom of the ridge and then through the ridge. They then fall into boxes placed below the ridge. Larger items do not fall though the ridges. These are alkaline batteries. Thus, because everything has been removed the process also sorts alkaline batteries.
Crush
To begin this process the batteries are put on a flat, rubber conveyor belt. This conveyer belt is approximately 20 feet long. The batteries fall off the end of the conveyor belt onto another rubber conveyor belt.
This second rubber conveyor belt is tilted upward at an approximately 45 degree angle. Every approximately 1.5 feet this conveyor belt has a slap of rubber attached to it. This slab is approximately 2 inches in height, is as long as the conveyor belt is wide, and is attached to the conveyor belt. This rubber slab picks up the batteries as they fall off the flat rubber conveyor belt. The second rubber conveyor belt is approximately 20 feet long. It takes the batteries this distance, where they fall into the first metal crusher.
First step
The first crusher crushes the batteries at 100-400 revolutions per minute. These batteries are crushed by a device with teeth or blades of approximately 8 inches long. The blades or teeth go into each battery, breaking the batteries into pieces.
A computer monitors and adjusts the speed of the crusher so the result is battery pieces of the right size.
This process crushes the batteries so that they are in pieces. Each piece is approximately 0.5 - 1.0 inches long (about 1.25 cm to about 2.5 cm). The temperature inside the chamber where the batteries are crushed reaches only 40-50 degrees Celsius.
As the batteries are crushed hydrogen and oxygen are released from the batteries.
Optionally, the released hydrogen and oxygen may be removed from the process. These gases mix with the air current the cyclone and are sucked out, as described below.
Oxygen can cause a fire. Removing the oxygen therefore significantly lowers the risk of fire. Moreover the low temperature of this process also reduces the risk of fire.
The air surrounding the crushing step is sucked up in a cyclone process expelling the air. The cyclone process pulls out metals still in dust. This consists of a spinning blade at the top of a chamber which is tapered so it gets narrower as the gases moves towards the bottom of the chamber. This creates a tornado-like effect which blows the air containing the gases down, through the chamber, and out of the chamber. The air containing the gases that has passed through the cyclone then goes to a filter. The air also contains may contain also light plastic or cardboard, which may be a battery component. It may be beneficial for the following process to have this material removed. The expelled air, which contains the hydrogen and oxygen, then goes into a tube which is connected to the outside atmosphere. A second filter catches any remaining particles, insuring that what is released to the atmosphere is only normal air, plus the hydrogen and oxygen present in the batteries. This mixture of light plastic and cardboard may be added to the process of recycling
Nickel Metal Hydride batteries as these small particles of plastic and paper may serve as attachment points of small particles of metals. This light plastic and cardboard may thus be thus be included along with the other parts of the recycled nickel metal hydride batteries, to a nickel smelter. Even very small amounts of other meta!s such as e.g. cobalt (2-4%) in the mixture, can thus be recycled.
At the end of the crushing chamber is a screen. This is adjusted so particles of different sizes can pass though, in this way the size of the battery pieces are regulated, making sure that only those that are small enough can pass through.
After passing through this first crushing chamber, the mix of battery pieces and dust passes into a tube. This tube is approximately 10 inches in diameter and is air-tight. The pieces and dust mixture will pass through this tube to the second crushing chamber, during which the dust is in this tube it is cooled down to room temperature.
Second crusher
The transfer tube brings the dust to a second crusher. This crusher is of the same basic design as the first crusher but is made to operate at higher speed. It turns at 1 ,000-1 ,200 revolutions per minute. This is the stronger crusher of the two crushers, it reduces the battery pieces to up to 6 mm in size.
The dust produced in this process is collected in a second cyclone. This second cyclone has two dust filters. Each dust filter is the same as the second filter from the first cyclone, as described above.
After crushing the remainder of the batteries, which are now a powder, moves along a device which could be called a "shaker-mover." It slowly shakes the powder in a way which causes it to move forward. The powder moves along a shaking conveyer belt. It moves along this belt for approximately 2.5 meters. While the powder is on this conveyer belt it passes under the magnetic separator in order to separate any ferrous material from the powder.
Magnetic separator The magnetic separator pulls the iron from the powder. This iron is in the form of flakes. The magnetic separator is positioned about 25 cm above the shaking conveyor belt. The magnetic separator is approximately a half meter wide and two and a half meters long, The key component of the magnetic separator is a magnet. The iron flakes are attracted to this magnet. As the iron flakes leave the powder and instead attach themselves to the magnet they are removed from the powder.
Below the magnet is a belt. The magnet behind the belt attracts and then holds the iron flakes onto the belt. The belt moves approx. 40 centimetres at which point it ends. When the belt ends there are no more magnets. The flakes then fall off the belt and are collected.
The starting material for the method according to the invention is Alkaline Black mass (denoted AB), which has been produced through dismantling and magnetic separation of iron metals as described above. The AB powder is a mixture of the cathodic (manganese oxide and graphite) and the anodic (zinc oxides and electrolytic solution) materials. The resulting material may optionally undergo a pre-treatment method in order to remove any no metallic material present in the batteries. These may be e.g. plastic films, paper pieces, electric wires etc from the dismantling operation non-woven cellulose or synthetic polymers. However, the material may also not be pre-treated in any way before use, and hence the material still contained plastic films, paper pieces, electric wires etc from the dismantling operation. The AB is then subjected to different methods to separate metals in the spent alkaline batteries. In its initial form the AB powder may have initial concentration of e.g. aluminum (in an amount of such as e.g. 1.2%), e.g. Iron (in an amount of e.g.
0.6%), manganese (in an amount e.g. 30%) and zinc (21.8 %).
The possible schematic routes to separation are e.g. as follows: A) Metals dissolution, H 2 S + Na 2 C0 3 to produce ZnS and MnC0 3
In this process the metals will be leached in H 2 S0 4 solution in combination with H 2 0 2 and/or S0 2 . After the leaching the solution will be filtrated to remove carbon and other insoluble materials. Using H 2 S gas ZnS can be precipitated from the solution at pH ~ 2. A filtration step is again needed to separate ZnS from the solution. The remaining manganese solution can be treated with Na 2 C0 3 to precipitate MnC0 3 , This method works well and it is possible to optimize for either ZnS or MnCC>3 purity by adjusting the pH at the ZnS precipitation step. B) Metals dissolution, NaOH to produce zinc and manganese hydroxides
The pH is elevated in steps after the dissolution of the metals. Zinc and manganese will precipitate at different pH values as hydroxides. The zinc will precipitate at a pH of about 7 while most manganese is still in solution. All manganese will have precipitated at pH 10.
C) Metals dissolution, Na 2 S or NaHS and Na 2 C0 3 to produce ZnS and MnC0 3
This route may be used to precipitate zinc as ZnS and manganese as MnC0 3 .By optimization of the parameters with respect to filtering and filter cakes such as e.g.
number of washings, pH of washing solutions etc, as precipitation of the respective zinc and manganese salts result. D) The precipitation of Mn as Mn0 2 using Caro's acid
This route aims to precipitate Manganese as Mn0 2 from the metals dissolution step using Caros's acid which is 26 % H 2 S0 5 , 58 % H 2 S0 4 and 2 % H 2 0 2 (according to preparation instructions from the literature). In this way the zinc containing solution could be sold and no waste water is left on the plant.
E) The precipitation of Mn as Mn0 2 by using 0 2 /S0 2 This is another possibility to remove manganese from the leaching solution. After the metals dissolution step 0 2 /S0 2 is used to precipitate Mn as Mn0 2j leaving a zinc containing solution. Thus there is no need to remove any waste water. This technique may be used for purification of solutions containing small amounts of manganese, such as e.g. in solutions containing residues of manganese or solutions which may have undergone any of the methods described herein wherein the majority of manganese have been removed and the method of E) is used as a complement to fully remove all manganese if required.
F) Liquid-liquid extraction
In the liquid-liquid extraction e.g. DEHPA or HDEHP (di-(2-ethylhexyl)phosphoric acid) may be used as extracting. When using e.g. DEHPA it may be necessary to remove any content of ferric iron as DEHPA extracts ferric iron. DEHPA-concentration could be e.g. about 35 % and aromatic free solvents should be used (such as e.g. kerosene). Four extraction steps in counter current series and two stripping steps, also counter current and in series should be used. The amount of steps depends on the required residual concentration of Zn. O/A ratio should be 2.5 with a temperature of 55°C. The stripping step will work at lower temperatures such as e.g. about 40-45°C. In the extraction steps the pH needs to be adjusted so that the leaving solution has of about e.g. pH 2. In this way zinc will be extracted while manganese stays in the aquatic phase.
For the stripping, an aqueous solution with a sulfuric acid concentration of 250 g/l may be used. The product would optimally contain 100 g/l zinc and 100 g/l sulfuric acid. This solution can be used as is. The original solution, now containing the manganese, may then be treated with Na 2 C0 3 to oduce MnC0 3 .
Consequently, present invention relates to a method for separating metals present in alkaline batteries. The method according to the invention comprises the following steps: a) crushing alkaline batteries and collecting the alkaline black mass resulting from the crushing process,
b) magnetically removing ferrous material from the alkaline black mass.
c) mixing the alkaline black mass with a leaching solution at acidic pH
d) gradually increasing the pH of the leaching solution by addition of a base to selectively precipitating the metals present in the leaching solution
e) collecting the precipitates.
Detailed description of the invention
Alkaline batteries make up about 80% of the collected batteries. They are primary batteries containing mainly of zinc/zinc oxide and manganese dioxide (Zn/ZnO andMn0 2 ). In the alkaline battery, the anode (negative) is made of zinc powder, which gives more surface area for increased current, and the cathode (positive) is composed of manganese dioxide. In the alkaline battery cell (nominal voltage of a fresh alkaline cell is 1.5 V), there is an alkaline electrolyte of potassium hydroxide whereas zinc-carbon batteries have acidic electrolytes.
Half-reactions in the eel! are:
Zn (s) + 20H- (aq)→ ZnO (s) + H20 (I) + 2e- 2Mn0 2 (s) + H 2 0 (I) + 2e-→ n 2 0 3 (s) + 20H- (aq)
Spent alkaline batteries are collected and may optionally be sorted prior to further actions in order to have alkaline batteries only as the starting material for preparation of the alkaline black mass. Alkaiine batteries are crushed to alkaline black mass (BM) in a mechanical process. Alkaline BM is produced in the recycling process of alkaline batteries. Iron is separated magnetically from the alkaline BM prior to the leaching process.
Alkaline black mass as a raw material Alkaline BM powder is a mixture of cathodic (manganese oxide and graphite) and anodic (zinc oxides and electrolytic solution) materials. In general it contains the following main metals; Al 1.2 %, Fe 0.6 %, Mn 30.0 % and Zn 21.8 % (vol%). However, it is to be clearly understood that any alkaline BM can be used according to the invention and in particular wherein the majority of metal content is Mn and/or Zn. The average particle size of alkaline BM is 250-500 μππ. Metals are known to be concentrated on the smaller fractions, however the method presented herein is suitable of use on any particle sizes raging from e.g. 0 to about 4000 μηι, such as e.g. about 20 μητι to about 3000 μιτι, such as e.g. about 60 μ η ι to about 2000 μι η , such as e.g. 125 μηη to about 1000 μηη, such as e.g. about 250 μηι to about 500 μιη. However, any particle sizes up to about 0.6 mm may be used in a process according o the invention. In the method according to the invention it is beneficial to have a small particle size so as to speed up the reaction in dissolving the metals present in the alkaline black mass. Even though, the alkaline biack mass may be used as is, the method may also involve any technique resulting in a smaller particle size, such as e.g. grinding of the alkaline black mass prior to the dissolution step of the metals.
As mentioned above, any ferrous material is removed magnetically as described above.
The vast majority of alkaline batteries contain mainly zinc and manganese in larger amounts. Thus present invention is mainly concerned with recovery of these metals. However, the inventive concept of this invention may very well be applied mutatis mutandis to other metals in recovery process not only limited to batteries, but in other recycling operations of any kind.
The chemical pathways to recovery of Zn and Mn.
According to the invention a method is presented based on an acidic reductive leaching system, based on sulphuric acid (H 2 S0 4 ). Zinc and manganese oxides can be
quantitatively dissolved by sulphuric acid according to:
ZnO + H 2 S0 4 → ZnS0 4 + H 2 0
MnO + H 2 S0 4 → MnS0 4 + H 2 0
On the other hand, the dissolution of manganese oxides such as e.g. Mn 2 0 3 and Mn 3 0 4 which may also be present in the alkaline black mass is only partial because Mn0 2 produced is insoluble:
Mn 2 0 3 + H 2 S0 4 →Mn0 2 + MnS0 4 +H 2 0
Mn 3 0 4 + H 2 S0 4 →Mn0 2 +2MnS0 4 + 2H 2 0 Hence, a reducing agent (e.g. hydrogen peroxide or S0 2 ) is required to leach all manganese from the sample. In this process other reducing agents may be used, such as e.g. citric acid, oxalic acid or isocitric acid etc. The reduction of manganese dioxide and hydrogen peroxide in acidic solution is given as follows:
Mn0 2 + H 2 S0 4 + H 2 0 2 → nS0 4 + 2H 2 0 + 0 2
There are several possibilities in the literature to recover Zn and Mn from spent alkaline batteries, e.g. dissolution with sodium compounds, liquid-liquid extraction. In present invention it has been surprisingly found that dissolution of alkaline BM in the presence of H 2 S0 and citric acid as a reducing agent followed by sequential precipitation results in a high yielding, environmentally friendly and safe process. This method also avoids the use of hydrogen peroxide which may be disadvantageous to use in larger scales for reasons of process safety and aspects of environment.
According to the method of present invention the leaching process may be performed by the use of an acid in order to dissolve the metals in the alkaline black mass. The acid may be any organic or inorganic acid and may typically be an oxoacid. Oxoacids acids or of organic or inorganic origin containing at least one oxygen atom, containing at least one other element, has at least one hydrogen atom bound to oxygen and form an ion upon loss of one or more hydrogen atoms (protons). Examples of oxoacids are, but not limited to, a carboxylic acids, sulphuric acid, persulphuric acid (also known as
peroxymonosulfuric acid), a sulphonic acid, a sulphinic acid, nitric acid, nitrous acid, phosphoric acid, hypochlorous acid, chlorous acid, chloric acid, perchloric acid, perbromic acid, metaperiodic acid. It is envisaged that the acids are used as an aqueous solution in various concentrations, but may also be in solution of mixtures of solvents of both organic and inorganic origin as long as solvent is inert to the reaction conditions. Moreover, it is also envisaged that the acid may be attached to a solid resin such as e.g. a poiymer or matrix.
The concentration of the solution of the acid used in the leaching process may be in the range of about 0.1 M to about 10 M, such as e.g. about 0.5 M to about 8M, such as e.g. about 1M to about 6M, such as about 2M to about 4M, or the acid solution may be of a concentration of at least 0.5M, such as e.g. at least about 1M, such as e.g. at least about 2M, such as e.g. at least about 3M such as e.g. at least about 4M, such as e.g. at least about 5M, such as e.g. at least about 6M, such as e.g. at least about 7M, such as e.g. at least about 8M, such as e.g. at least about 9M, such as e.g. at least about 10M. Moreover depending on the need to dissolve the metal, the concentration of the acid in solution may be e.g. about 1 M or such as e.g. about 2 , such as e.g. about 3M, such as e.g. about 4M, such as e.g. about 5M, such as e.g. about 6M, such as e.g. about 7M, such as e.g. about 8M, such as e.g. about 9M, such as e.g. about 10M.
The pH of the leaching solution during which the metal is to be dissolved may be in the range of e.g. about pH = -1 to about pH = 6, such as e.g. about pH = 0 to about pH = 5, such as e.g. about pH = 2 to about pH = 4, such as e.g. about pH = 2 to about pH = 3, or such as e.g. about pH - 1 to about pH = 2, such as e.g. about pH = 2 to about pH = 3, such as e.g. about pH = 3 to about pH = 4, or such as e.g. about pH = 4 to about pH = 5.
The leaching process may be performed in a ratio of the alkaline black mass to acid (measured as weight to weight % ratio; w/w %) of e.g. about 1 w/w%, such as e.g. about 5 w/w%, such as e.g. about 10 w/w%, such as e.g. about 15 w/w%, such as e.g. about 20 w/w%, such as e.g. about 25 w/w%, v such as e.g. about 30 w/w%, such as e.g. about 40 w/w%, such as e.g. about 50 w/w%, such as e.g. about 60 w/w%, such as e.g. about 70 w/w%, such as e.g. about 75 w/w%, as long as the molar equivalence of the acids is enough to dissolve the metals. The temperature of the reaction mixture during the leaching process may be in the range of e.g. about 5°C to about 100°C, such as e.g. about 10°C to about 90°C, such as e.g. about 20°C to about 80°C, such as e.g. about 30°C to about 70°C, such as e.g. about 40°C to about 60°C, or such as e.g. about 40°C to about 50°C, such as e.g. about 30°C to about 60°C, or about 30°C, about 40°C, about 50°C, about 60°C, about 70°C, about 80°C, about 90°C, about 100°C.
The reaction time during the leaching process may be in the range of any time to completely or almost completely dissolve the metals of the alkaline black mass. Such time ranges may be in the range of e.g. about 30 minutes to about 24 hours, such as e.g. about 1 hour to about 10 hours, such as e.g. about 2 hours to about 3 hours, such as e.g. about 2 hours to about 9 hours such as e.g. about 3 hours to about 8 hours, such as e.g. about 4 hours to about 7 hours, such as e.g. 5 hours to about 6 hours.
The reaction during the leaching step (i.e. the dissolution of the metal content of the alkaline black mass may optionally be performed in the presence of a gas such as e.g. oxygen (0 2 ) or sulphurdioxide (S0 2 ). During the leaching process a reducing agent may optionally be present in order to reduce any insoluble metal oxides formed by reaction of the acid (such as e.g. sulphuric acid). The reducing agent may be e.g. hydrogen peroxide (H 2 0 2 ) or S0 2 , or it may be e.g. a carboxylic acid (mon-, di- or tri- carboxylic acid) such as e.g. perbenzoic acids such as metha-ch!oroperbenzoic acid, citric acid, oxalic acid, malonic acid, maleic acid, fumaric acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azaleic acid, tartaric acid, isocitric acid, aconitic acid, propane-1 ,2,3-tricarboxylic acid or trimesic acid or any combinations thereof. The concentration of the reducing agent may be in the range of about e.g. 0.01 M to about 10 M, such as e.g. about 0.1 M to about 9M, such as e.g. about 0.12 M to about 8.5 , such as e.g. about 0.125 M to about 8.45 M, such as e.g. 0.5 M to about 8M, such as e.g. about 1 to about 6M, such as about 2 to about 4M, or may be of a concentration of at least 0.5M, such as e.g. at least about 1 M, such as e.g. at least about 2M, such as e.g. at least about 3M such as e.g. at least about 4 , such as e.g. at least about 5M, such as e.g. at least about 6M, such as e.g. at least about 7M, such as e.g. at least about 8M, such as e.g. at least about 9M, such as e.g. at least about 10M.
The leaching process may be performed in a ratio of the alkaline black mass to reducing agent (measured as weight to weight % ratio; w/w %) of e.g. about 1 w/w%, such as e.g. such as about 2 w/w %, such as e.g. about 3 w/w%, such as e.g. about 5 w/w%, such as e.g. about 10 w/w%, such as e.g. about 15 w/w%, such as e.g. about 20 w/w%, such as e.g. about 25 w/w%, v such as e.g. about 30 w/w%, such as e.g. about 40 w/w%, such as e.g. about 50 w/w%, such as e.g. about 60 w/w%, such as e.g. about 70 w/w%, such as e.g. about 75 w/w%, as long as the molar equivalence of the acids is enough to dissolve the metals.
At the completion of the leaching process, the entire metal content is in solution or at least about 60%, or at least about 70%, or at least about 80%, or at least about 85%, or at least about 90%, or at least about 95%, or at least about 00% of the metal content is in solution, i.e. have been converted to their respective cations in solution. It is to be clearly understood that of the metals present in the alkaline black mass, the dissolution percentages between the different metals may vary such that e.g. 85% of one metal may be in solution and 95% of another metal may be in solution after completion of the leaching process.
After completion of the leaching step any remaining residues may optionally be removed by e.g. filtration. These residues may be any insoluble remains such as metals, papers such as e.g. non-woven layers of cellulose or synthetic polymers.
The total amount of liquid solution in relation to the alkaline black mass (measured as the ratio of g of alkaline black mass to volume in ml of solution) may be e.g. about 1/0.5, such as e.g. about 1/1, such as e.g. about 1/2, such as e.g. about 1/3, such as e.g. about 1/4, such as e.g. about 1/5, such as e.g. about 1/6, such as e.g. about 1/7, such as e.g. about 1/8, such as e.g. about 1/9, such as e.g. about 1/10. For example, in a batch were 20 g of alkaline black mass is used a total volume of 100 ml of solution is used.
After completion of the leaching step, the pH of the resulting solution is altered.
Preferably, this is performed by raising the pH slowly and under controlled conditions, such as incrementally increasing the pH by portion wise addition of e.g. a base during careful monitoring of the pH of the resulting solution. This process may optionally be performed under stirring. This can be done by any well known techniques in the art such as e.g. automated drop-wise addition of the base while electronically monitoring the pH of the solution under e.g. magnetic stirring.
A suitable agent that may be used for raising the pH of the leaching solution may be any base. Such a base may be, but is not limited to organic or inorganic bases such as amines or inorganic hydroxides such as e.g. sodium hydroxide or potassium hydroxide. The addition of the base is primarily in the form of an aqueous solution of appropriate concentration. Moreover, the solution may be a mix of water and any other appropriate solvent, such as e.g. an alcohol in from of methanol or ethanol. However, it is also envisaged that that the base may be attached to a solid support, such as e.g. having an organic base attached to a polymer resin, wherein the immobilized base on solid support is contacted with the leaching solution. The addition of the base to the leaching solution is performed in order to bring about a selective precipitation of the metals present as cations in the leaching solution. If e.g. an inorganic hydroxide is used as base, the metal cation is converted into its corresponding hydroxide which is depending on its chemical nature soluble or insoluble at varying pH of the leaching solution. Consequently, by monitoring the pH a selective precipitation of separate metal hydroxides can be accomplished, thereby allowing collection of separate hydroxide fraction of metals. Thus the method according to the invention does not require electrolytic separation of the metals present in the leaching solution.
The concentration of the base in solution may be in range of at least 0.5 M, such as e.g. at least about 1 M, such as e.g. at least about 2 M, such as e.g. at least about 3 M such as e.g. at least about 4 M, such as e.g. at least about 5 M, such as e.g. at least about 6 M, such as e.g. at least about 7 M, such as e.g. at least about 8 , such as e.g. at least about 9 , such as e.g. at least about 10 M, such as e.g. at least about 11 M, such as e.g. at least about 12 M, such as at least about 13 M, such as at least about 14 M depending on the based used.
As mentioned above, in the method according to the invention it is important to monitor the pH during the basification of the leaching solution as the inventors of present invention have surprisingly found that precipitation of different metal oxides occur in narrow pH ranges. If the metals to be regained form the alkaline black mass are e.g. zinc and manganese it has been found that zinc hydroxide is precipitated in a pH range of about 6.4 to about 6.7. In this pH range the manganese is still in solution and thus pure zinc hydroxide can be collected and separated by filtration form the leaching solution. Raising the pH to about 7,6 initiates precipitation of manganese to manganese hydroxide which continues to precipitate up to a pH of about 1. Thus depending on the composition of the alkaline black mass carefully monitoring the pH may enable selective precipitation of different meta!s as their respective salts, wherein the salt may be e.g. the corresponding hydroxide.
After precipitation of, the collected solid product (e.g. the corresponding metal hydroxide) may be washed.
According to the method of present invention, the aqueous solutions used during the entire process (leaching solutions and washing solutions) can be recycled, thereby minimizing the amount of waste water produced during the process and thus making the method according to the invention cost efficient and environmentally friendly.
It is to be clearly understood that all the above mentioned parameters in their respective intervals can be combined in any combinations, such as e.g. a reaction temperature in the leaching process (e.g. 50 °C) can be combined with a reaction time of e.g. 3 h, a concentration of citric acid (reducing agent) of e.g. 0.127 M, a sulphuric acid concentration of e.g. 2 M etc.
Legends to figures Figure 1. Illustrates the recovery process for zinc and manganese from spent alkaline batteries.
Figure 2. Illustrates the precipitation of zinc and manganese with NaOH from spent alkaline batteries (after dissolution in H 2 S0 4 ). The figure illustrates the narrow pH interval in which zinc is precipitated.
Figure 3. Illustrates the size distribution of particles in the alkaline black mass Figure 4. Illustrates the distribution of manganese (upper curve) and zinc (lower curve) according to the particle size distribution in the alkaline black mass.
The invention is further illustrated in the examples that are not intended to limit the invention in any way.
Examples Example 1 Alkaline BM was not pre-treated before the dissolution, I.e. any residues from the batteries such as e.g. cellulose or plastic polymers was not removed. Dissolution process was carried out in a reactor vessel containing a temperature control (under atmospheric pressure). In the reactor system, reaction temperature was carefully controlled and citric acid was added. Metal concentrations in the residues and liquids were determined by ICP- MS and AAS.
Dissolution process and recovery of Zn and n
Iron is first separated magnetically from the alkaline black mass and as described herein. Iron free alkaline black mass is leached with sulphuric acid (H 2 SC ). Leaching is a critical step because all metals should be in the liquid phase as metal sulphates (see Figure 1). The leaching reaction may be performed in the presence of a gas {such as e.g. oxygen or S0 2 ) or by using acids as a reducing agent. The use of acids make it a two-phase reaction in which mass and heat transfer phenomena are more easy to control (compared with a three-phase reactions with gas, i.e. a system wherein a solid, liquid and gas is used).
Leaching of alkaline black mass was done by mixing the black mass (10 g or 20 g) with the sulfuric acid (2 M), at pH from 1 to 2, with the ratio 20 w/w% (optimized aikaline BM to acid ratio). Leaching temperature around 40-50°C (exothermic); leaching time 2-3 hours (lab-scale batch operation). Leaching was made in the presence of reducing agent using citric acid as the reducing agent under stirring. The concentration of citric acid was 0.127 M or 2.72 g of citric acid to 20 g of alkaline black mass. The total leaching volume was 100 ml, i.e. in a ratio of 1/5 where 20 g of black alkaline mass was used. After leaching under these conditions, the near quantitative amount of Zn (96%) and Mn (76%) is in the solution compared to the respective metal contents of the alkaline black mass. Leaching residue (solid) of alkaline BM was around 22.5% of the aikaline black mass (raw material). This residue consists mostly of organic matter. Leaching residue contains e.g. material from the alkaline battery separator which is made of a non-woven layer of cellulose or a synthetic polymer etc, which is removed by filtration.
Zinc and manganese are separated from the leaching solution (acidic) by a two or three stage sequential precipitation procedure (see Figure 1). Sodium hydroxide (NaOH) is used as a precipitating agent in a concentration of 6 M and added slowly under controlled conditions and allowing the pH to stabilize between additions of further portions of NaOH. pH must be controlled very carefully as precipitation occurs in a very narrow pH window (see Figure 2). The precipitation is done as a batch process to get the optimized control for pH. In the first stage, in the pH range of 6.4-6.7, zinc hydroxide is precipitated well separated from manganese which, at this pH, stays in the solution.
In the second stage, manganese is precipitated as Mn(OH) 2 which is easily oxidised to Mn0 2 . pH is this stage is increased starting from 7.6 up to 11. Solid product, Mn(OH) 2 and Mn0 2 , may be used as raw material in various applications. Solid products are washed between the precipitations. This water can be recycled and reused in the batch process. The yield of zinc as Zn(OH) 2 quantitative in comparison with the zinc content of the leaching solution, and 97% of the manganese as Mn(OH) 2 in comparison with the leaching solution. The amount of waste material flows is minimized in the process by recirculation. Precipitation reactions are carried out at room temperature which also minimizes the energy need.
Example 2
Laboratory trials
A typical laboratory work setup is as follows. The desired amount of AB is placed in a beaker. The desired amount of sulphuric acid solution is poured into the beaker. The suspension is stirred by a magnetic stirrer and heated to the desired temperature.
Hydrogen peroxide is added into the beaker in small aliquots during the entire reaction time. The solids are removed from the liquor by filtration on a Buhner. The liquor is stored "as such" at room temperature. After metal analysis, Zinc and Manganese are precipitated from the solutions by a selection of routes. Typically, 50 - 100 ml of the solution is placed in a beaker and stirred by a heated magnetic stirrer. The desired precipitation agent is added by a peristaltic pump. After completed reaction the solids are separated from the liquor by filtration on a Buhner. All amounts are as described above.
Example 3
Digestion of the Alkaline Black with H 2 S0 4 and H 2 0 2
A series of digestion tests were performed to determine the yield of Zn, Mn, Al and Fe into the digestion liquors in different digestion conditions. The AB powder had the following initial concentrations:
Al 1.2 %, Fe 0.6 %, Mn 30.0 % and Zn 21.8 %.
The amount of H 2 0 2 , the concentration of H 2 S0 4 and the amount of the Alkaline Black were varied.
The leaching conditions are presented in Table 1 below.
* H202 was added
during 4 h.
** Alkaline black was added
during 4 h.
Table 1
Example 4
Optimization of the mass of Alkaline Black in digestions
To optimize the amount of Alkaline Black powder to be used in the leaching, four different leaching tests were performed changing the alkaline black powder mass (20, 25, 30 and 35 grams in each test). The AB powder had the following initial concentrations:
Al 1.2 %, Fe 0.6 %, Mn 30.0 % and Zn 21.8 %.
The leaching conditions were as presented in Table 2 below. The hydrogen peroxide was added with a peristaltic pump at a rate of 0.2 mi in every 90 seconds. Water was added into the liquor after the digestion before the filtration of the solids in two tests.
Table 2. The leaching conditions of the Alkaline black powder digestions (varying the mass of the alkaline black mass)
The starting materia! (the Alkaline Black powder) for these digestion tests and the solid residues of the tests 20 g and 35 g of starting material were analyzed by the OMG laboratory (XRF analysis). The concentrations of the elements in the starting material and in the solid residues are presented in the Table 3. The last column presents the concentrations of the elements reported by the supplier of the Alkaline Black powder (Akkuser Oy) and these should match the first column values.
Element: Alkaline Black Residue 1 Residue 2 Reported by the
powder (20 g of AB) (35 g of AB) supplier of AB
Mn 36,3 0,6 45,2 33,7
Zn 37,4 0,4 24,9 27,5
Si 0,08 0,2 21 ,1
C 8,3 87 18,6 7,69
Table 3. The concentrations of the elements in the alkaline black powder/mass and in the solid residues after digestions. Example 5
The precipitation ofZn as ZnS and Mn as MnC0 3 using H 2 S
A precipitation test was made in the laboratory of OMG with 2-component solution {Zn 64 g/l and Mn 40 g/l) to precipitate Zn first as ZnS and then Mn as MnCC>3 from a sulphuric acid solution using H 2 S. 400 ml of solution was heated to 70°C. H 2 S was sparged into the solution at a rate of 22 liters/h for 1 hour at pH 2.5. (The theoretical amount of H 2 S to precipitate Zn is 11 liters/h.) A solution of 220g/l NaOH was used to control the pH. The precipitate was filtered and weighed. The mass of the ZnS precipitate was 4 .7 g. The calculated yield was 09 %. The filtrate had 20 mg/l of Zn left. The concentration of Zn in the precipitate was 61.1 % and the theoretical concentration in ZnS is 67 %. The concentrations of Mn and Na in the precipitate were 0.36 % and 0.15 % respectively. 400 ml of the filtrate from the ZnS precipitation was used to precipitate Mn as MnC0 3 . 321 ml of 140 g/l Na z C0 3 was added into the filtrate at 70 °C. The solution was agitated with a propeller type stirrer and the reaction time was 0.5 h. Approximately 20 g of precipitate was formed. The filtrate had 8 mg/l of Mn left. The concentration of Mn in the precipitate was 43.3 % while the theoretical amount of Mn in MnC0 3 is 47.7 %. The concentrations of Zn and Na in the precipitate were 0.016 % and 1.16 % respectively. Fresh precipitate of MnC0 3 is difficult (slow) to filtrate.
The experiment was repeated using liquor from alkaline black + H2O2 leachings.
- 500 ml. Liquor from AB leaching
- Propeller mixing
- T: 60°C
- H 2 S gas feed 15.5 l/h
- Neutralization with NaOH (220 g/l) pH set to 2.0 -. consumption: 125 ml.
- Time 1h.
- Final ZnS precipitate: 29. Og.
Table 4, ZnS precipitation
- 400ml of the final solution from previous step
- Propeller mixing
- T: 60°C
- 200 ml. Na 2 C0 3 solution (140 g/l) -+ added slowly until temperature reached.
- Final solution 570 ml.→ pH. 9,5
- Final precipitate (MnC0 3 ): 24.8g.
Example 6
The precipitation ofZn as ZnS and Mn as MnC0 3 using Na 2 S, NaHS and
Na 2 CQ 3
A series of experiments have been performed to test the separation of Zn as ZnS and the separation of Mn as MnC0 3 from digestion liquors. NaHS and Na 2 S were used to precipitate ZnS and Na 2 C0 3 was used to precipitate MnC0 3 .
A known volume of leaching liquor was measured into a 200 - 500 ml beaker. The liquor wasstirred with a magnetic stirrer and heated with a heating plate if necessary. pH was measured with a SenTix 81 pH electrode.
A precipitating reagent was added into the liquor in 0.1 - 0.5 ml portions at a defined rate and pHwas adjusted after each addition in ZnS precipitations. In MnC0 3 precipitations pH was notcontrolled. After the addition of the defined amount of precipitating reagent the solution was cooled and filtered. Zn, Mn, AI and Fe were analyzed from the filter cakes and the filtrates.
The conditions and the results of the precipitation tests are in Tables 6 and 7
Table 6. Conditions and the analysis of the precipitation tests (ZnS and Mn0 3 precipitations)
Table 7. Conditions and the analysis of the precipitation tests (ZnS, Mn0 3 and Mn(OH) 2 precipitations) Example 7
The precipitation of Mn as Mn0 2 by using 0 S0 2
A 400-ml solution containing 38.5 g/I of Mn was sparged at 70°C with 0 2 /S0 2 mixture (8,2 liters/h of 0 2 and 0.25 liters/h of S0 2 ). The pH was continuously adjusted to 3.5 using 220 g/I NaOH solution. The Mn concentration of the solution was monitored at 1 , 3, and 4.5 hours and the concentration was 33.5 g/l 35 g/l and 33.1 g/l, respectively.
The mass of the collected precipitate was 14.6 g and the concentrations of Mn and Zn in it were 43% and 5.4 %, respectively. Example 8
The precipitation of Mn as Mn0 2 using Cam's acid
Caro's acid was used in an experiment to precipitate Mn0 2 from a leaching liquor of the Alkaline Black. The composition of Caro's acid was 26 % H 2 S0 5 , 58 % H 2 S0 4 and 2 % H 2 0 2 (according to preparation instructions from the literature).
50 % of the stoichiometric amount of Caro's acid was used. 50 mi of liquor (containing 68.0 g/l Mn and 63.6 g/l Zn) was measured into an erienmeyer flask. The pH is adjusted to 2.5 - 3 by H 2 S0 4 solution or 50 % NaOH solution. The solution was agitated by a magnetic stirrer at room temperature. 40.7 g of Caro's acid was added drop wise into the liquor and the pH was kept between 2.5 - 3. The stirring continued 2 hours after the last drops of Caro's acid. Solids were separated by vacuum filtration. The filtrate and the precipitate were analyzed for Zn and Mn. The precipitate was washed with 146 ml of water (+75°C) and twice with 100 ml of 5 M H 2 S0 4 solution. Zn and Mn were analyzed from the washing water and the washing acids. The solids were dried in an oven at +105°C.
The Mn0 2 precipitate (8.99 g) contained 304.2 mg/g of Mn and 40.2 mg/g of Zn. The filtrate (0.22 liters) contained 0.25 mg/i Mn and 1645 mg/l Zn. 80 % of Mn and 11 % of Zn were found from the precipitate. 80 % of Zn and 0.002 % of Mn were found from the filtrate.
The Zn and Mn contents of the washing water and 5 M H2SO4 solutions were the following:
washing 1 : +75 °C (146 ml): Mn 0.037 mg; Zn 146 mg
washing 2: 5 M H 2 S0 4 (100 ml): Mn 3.0 mg: Zn 151 mg
washing 3: 5 M H 2 S0 4 (100 ml): Mn 3.2 mg; Zn 8 mg.
Example 9
The precipitation of Mn as Mn(OH) 2 and Zn as Zn(OH) 2
An initial amount of 20 g of Alkaline Black was washed with 100 ml MilliQ water and mixed for 5 minutes. The mixture was filtered and the washed Alkaline Black was then subjected to 600 ml of an acid solution consisting of 3 % H 2 S0 4 and 2 % H 2 0 2 for 20 min. The insoluble material was filtered out and analyzed. In ICP-MS analysis, the following elements were found: Fe 6.8 g/kg.
Ba 2.6 g/kg.
A1 2.3 g/kg.
K 1 .8 g/g.
Si 1.6 g/kg.
Zn 1.2 g/kg.
Mn 1.1 g/kg.
Pb 0.7 g/kg.
Ca 0.5 g/kg and
Hg 0.3 g/kg.
Also carbon was most likely in this fraction but it was not analysed.
The acid solution was then combined with the wash water to elevate the pH and an additional amount of 90 ml 10 NaOH was added to get to the final pH of 11.5. At this pH Mn precipitates as Mn(OH) 2 , and Zn stays in solution as zincate ions. The precipitate was filtered and analyzed. The Mn precipitate contained 31 % Mn, 21 % Zn, 4.8 % Na and traces of K, Fe and other metals.
To the remaining filtrate HzS04 was added until the pH dropped to 8 where Zn was allowed to precipitate as Zn(OH) 2 The precipitate was found to be fairly pure with 44% Zn and less than 0.2% Mn. The precipitate also contained 3.6% Na.
Solution was filtered and pH of filtrate lowered to 6 to precipitate Zn(OH) 2 and then filtered again.
Table 8. Elemental distribution in the process expressed in ppm. Fe 6.8 g/kg.
Ba 2.6 g/kg.
A1 2.3 g/kg.
K 1 .8 g/g.
Si 1.6 g/kg.
Zn 1.2 g/kg.
Mn 1.1 g/kg.
Pb 0.7 g/kg.
Ca 0.5 g/kg and
Hg 0.3 g/kg.
Also carbon was most likely in this fraction but it was not analysed.
The acid solution was then combined with the wash water to elevate the pH and an additional amount of 90 ml 10 M NaOH was added to get to the final pH of 11.5. At this pH Mn precipitates as Mn(OH) 2 , and Zn stays in solution as zincate ions. The precipitate was filtered and analyzed. The Mn precipitate contained 31 % Mn, 21 % Zn, 4.8 % Na and traces of K, Fe and other metals.
To the remaining filtrate HzS04 was added until the pH dropped to 8 where Zn was allowed to precipitate as Zn(OH) 2 The precipitate was found to be fairly pure with 44% Zn and less than 0.2% Mn. The precipitate also contained 3.6% Na.
Solution was filtered and pH of filtrate lowered to 6 to precipitate Zn(OH) 2 and then filtered again.
Table 8. Elemental distribution in the process expressed in ppm.
Table 9. Main component distributions expressed in percentages.
Conclusions:
• Leaching step is very effective
• Zn precipitate is quite pure but about 20% Zn is lost yielding an 80% total recovery
• Mn precipitate has excellent recovery rate but still contains 21% Zn
• Hg remains mainly in insoluble mass and a small amount is transferred to the wash water
• Iron remains in the insoluble mass but also present in Mn precipitate as impurity (~0.2%)
• Waste water contains 1.8% Na but very little anything else.
Two Mn-hydroxide precipitation tests were performed at pH 12 and at pH 9 and the yields of Mn,
Zn, Fe and Al into the hydroxide precipitation were calculated. The conditions and yields are presented in Table 7.
Powdered AB composition
• Mn: 34.6 % (30.0 %).
· Ζη: 27.2 % (21.8 %).
• Fe: 0.6 % (0.6 %).
• Al: 0.1 % (1.2 %).
(coarse material composition in parentheses) Reductive leaching of powdered AB by H2S04 + S02
• - 80 g of AB + 400 ml of H2S04 (cone. 200 g/l) + approx. 30 ml/min S02 ,room temperature, 4 hours reaction time
• - leaching liquor (recovery % in parentheses):
• Zn: 48 g/l (89 %)
· Mn: 61 g/l (88 %)
• Fe: 1 g/l (83 %)
• Al: 0,2 g/l (90 %) • - left in filter cake:
• Zn: 0.08 %
• Mn: 0.09 %
• Fe: 0.38 %
• Al: 0.28 %
Alkaline Black Mass Size and elemental distributions
The alkaline black mass was sieved and the fractions were collected. Every fraction was individually dissolved using microwave oven and aqua regia. The sample solutions were diluted and measures using ICP-MS.
Table 10. Elemental distributions in alkaline black mass size fractions.
Example 10
Plant trial
Leaching:
The plant trials were conducted as follows. Three different leaching trials were performed with slightly different recipes. On the plant a 4 m3 reactor was charged with the desired amount of sulphuric acid (200 g/l). The temperature of the reactor was ambient (~20°C). The AB powder was charged to the reactor using a vacuum transported. When the reactor was charged the stirring was continued for another hour (1 H). During addition of AB the temperature rose to 55- 60°C. The temperature was kept at 60°C for the remaining of the trial. After completed leaching the content of the reactor was emptied into filtration big bags to separate the bulk of the undissolved mate al. The liquor was finally filtered though a bag filter (5 μιτι) and a polishing filter.
Table 1 1. Conditions and results from the plant trials. Example 11
Separation ofZn as Zn(OH) 2
A trial was conducted to precipitate Zn as Zn(OH) 2 by raising the pH of the solution to 7 by addition of Sodium hydroxide. The trial was conducted on 1000 I of the leach solution from the previous step.
The solution was filtered by using a Nutsche type filter, plate filter and a drum filter. The best results were obtained with the drum filter giving a dry content between 50 - 70 %. The dry content using a plate filter was around 35 %. Separation of Mn as MnC0 3
The pH of the filtered solution from previous step was increased to 10 using sodium carbonate to precipitate Mn as MnC0 3 . A very fine precipitate was formed.
In Specific Embodiments the present invention also relates to the following items: Items
I . A process for the selective recovery of metal ions from alkaline batteries, comprising the steps of:
(a) magnetically separating iron metals from dismantled alkaline batteries to produce an alkaline black mass;
(b) treating the alkaline black mass with an acid;
(c) treating the alkaline black mass with a reducing agent;
(d) filtering the product of step (c);
(e) from the filtered product of step (d), selectively precipitating the
solubilized metal ions with a precipitating agent to form a precipitate; and,
(f) collecting the precipitate. 2. The process of item 1 , wherein the metal ions comprise Zn(ll) ion.
3. The process of item I, wherein the metal ions comprise Mn(ll) ion.
4. The process of item 1 , wherein the metal ions comprise Zn(ll) and Mn(ll) ions.
5. The process of item 1 wherein the acid is sulfuric acid.
6. The process of item 1 wherein the reducing agent is hydrogen peroxide. 7. The process of item 1 herein the acid is sulfuric acid and the reducing agent is hydrogen peroxide.
8. The process of item 1 wherein the precipitating agent comprises hydrogen sulfide, H 2 S.
9. The process of item 1 wherein the precipitating agent comprises a salt of carbonate ion, C0 2 2 .
10. The process of item 1 wherein the precipitating agent comprises a mixture of hydrogen sulfide, H 2 S, and a salt of carbonate ion, C0 2 2" .
I I . The process of item 1 wherein the precipitating agent comprises hydroxide ion. 12. A process for the selective recovery of metal ions from alkaline batteries, comprising the steps of:
(a) magnetically separating iron metals from dismantled alkaline batteries to produce an alkaline black mass;
(b) extracting the alkaline black mass with an ionic liquid so as to selectively extract the metal ions;
(c) treating the alkaline black mass with an acid;
(d) treating the alkaline black mass with a reducing agent;
(e) filtering the mixture of step (c);
( f ) from the filtered mixture of step (d), selectively precipitating the
solubilized metal ions with a precipitating agent to form a precipitate; and,
(g) collecting the precipitate.
13. The process of item 12, wherein the metal ions comprise Zn(ll) ion.
14. The process of item 12, wherein the metal ions comprise Mn(ll) ion.
15. The process of item12, wherein the metal ions comprise Zn(ll) and Mn(ll) ions. 16. The process of item 12 wherein the acid is sulfuric acid.
17. The process of item 12 wherein the reducing agent is hydrogen peroxide.
18. The process of item 12 wherein the acid is sulfuric acid and the reducing agent is hydrogen peroxide.
19. The process of item 12 wherein the precipitating agent comprises hydrogen sulfide, H 2 S. 20. The process of item 12 wherein the precipitating agent comprises a salt of carbonate ion, C0 2 2" .
21. The process of item 12 wherein the precipitating agent comprises a mixture of hydrogen sulfide, H 2 S, and a salt of carbonate ion, C0 2 2" .
22. The process of item 12 wherein the precipitating agent comprises hydroxide ion. 23. A process for the recovery of Zn(ll) and Mn(ll) ions from alkaline batteries, comprising the steps of:
(a) magnetically separating iron metals from dismantled alkaline batteries to
produce an alkaline black mass;
(b) treating the alkaline black mass with sulfuric acid;
(c) treating the alkaline black mass with hydrogen peroxide;
(d) filtering the product of step (c);
(e) from the filtered product of step (d), precipitating the solubilized Zn(ll)
and Mn(ll) ions with hydroxide ion to form a precipitate; and,
(f) collecting the precipitate.