WO2019180642A1 - Procédé de récupération sélective de l'étain et réacteur destiné à être utilisé dans ledit procédé - Google Patents

Procédé de récupération sélective de l'étain et réacteur destiné à être utilisé dans ledit procédé Download PDF

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Publication number
WO2019180642A1
WO2019180642A1 PCT/IB2019/052273 IB2019052273W WO2019180642A1 WO 2019180642 A1 WO2019180642 A1 WO 2019180642A1 IB 2019052273 W IB2019052273 W IB 2019052273W WO 2019180642 A1 WO2019180642 A1 WO 2019180642A1
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WIPO (PCT)
Prior art keywords
tin
oxide
granulate
lead
scrap
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PCT/IB2019/052273
Other languages
English (en)
Inventor
Wojciech Hyk
Konrad Kitka
Dariusz Rudnicki
Original Assignee
Uniwersytet Warszawski
Greenmet Technology Sp. Z O. O.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Uniwersytet Warszawski, Greenmet Technology Sp. Z O. O. filed Critical Uniwersytet Warszawski
Priority to EP19726139.9A priority Critical patent/EP3768869A1/fr
Publication of WO2019180642A1 publication Critical patent/WO2019180642A1/fr

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B25/00—Obtaining tin
    • C22B25/06—Obtaining tin from scrap, especially tin scrap
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B1/00—Preliminary treatment of ores or scrap
    • C22B1/005—Preliminary treatment of scrap
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B3/00—Extraction of metal compounds from ores or concentrates by wet processes
    • C22B3/02—Apparatus therefor
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B3/00—Extraction of metal compounds from ores or concentrates by wet processes
    • C22B3/04—Extraction of metal compounds from ores or concentrates by wet processes by leaching
    • C22B3/06—Extraction of metal compounds from ores or concentrates by wet processes by leaching in inorganic acid solutions, e.g. with acids generated in situ; in inorganic salt solutions other than ammonium salt solutions
    • C22B3/065—Nitric acids or salts thereof
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B3/00—Extraction of metal compounds from ores or concentrates by wet processes
    • C22B3/20—Treatment or purification of solutions, e.g. obtained by leaching
    • C22B3/44—Treatment or purification of solutions, e.g. obtained by leaching by chemical processes
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B7/00—Working up raw materials other than ores, e.g. scrap, to produce non-ferrous metals and compounds thereof; Methods of a general interest or applied to the winning of more than two metals
    • C22B7/006—Wet processes
    • C22B7/007—Wet processes by acid leaching
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/20—Recycling

Definitions

  • the present invention provides a method for the selective recovery of tin from a tin-containing material, preferably electronic scrap, particularly printed-circuit boards, the method comprising pretreatment of the tin-containing material, selective solubilization of the pretreated material to precipitate selectively the tin compounds comprising exposing the pretreated tin-containing material to a washing bath containing nitric acid and isolation of tin from the washing bath as tin oxide.
  • the present invention provides also a reactor useful for the selective solubilization of the tin-containing material.
  • the invention provides also a method for the purification of tin oxide contaminated with lead oxides to give metal lic tin by thermal treatment conducted in the presence of a novel fluxing agent and use of a novel fluxing agent as an environment for conducting thermal reduction of tin dioxide to metallic tin.
  • the present invention finds application in a utilization process of electronic scrap and recovering from said scrap a valuable raw material comprising a tin material from electronic scrap.
  • Tin occurs in three known allotropic forms with different densities, crystallo graphic structures, and in consequence also physical forms.
  • the most abundant tin form is a beta variety/form which is stable at the room temperature. This is a form of a silver-grey metal with a density of 7,29 g/cm 3 i and a melting point of 23 l,88°C, characterized by its high forgeability and ductility.
  • the beta form stored for a longer period at tem peratures below l3°C display a tendency to convert into grey (alpha) tin, present as a dark grey powder. In practice, said process takes place with perceptible speed not before -40°C. This effect, denominated a contexttin pest”, is responsible for progressive destruction of objects made of this material.
  • Metallic tin heated to the high temperature and rapidly cooled to the low temperature is converted into a gamma form characterized by high fragility.
  • tin finds use in processes for the preparation of various types of chemical compounds.
  • Organometallic compounds of tin are used as pharmaceuti cals, plant protection agents, stabilizers or catalysts for the production of fertilizers.
  • Tin is a consultp” block element and form oxides at the oxidation state of +2 and +4. Tin oxides have an amphoteric character and consequently they can form a broad spectrum of various chemical compounds in reaction with both acids and bases.
  • Both natural and primary industrial source of tin is cassiterite, which is its diox- ide (Sn0 2 ). Deposits of this mineral created by hydrothermal processes are of the principal industrial importance.
  • tin-containing deposits are hydrothermal cassiterite-sulphide formation connected mainly to shallow magmatic centres.
  • a characteristic feature of thid kind of deposits is also, apart of Sn0 2 , the presence of stannite, tin and lead sulphides, mainly in a form of galena.
  • These are generally vein deposits of diversified thickness of from several metres and diversified lengths of the formed veins.
  • Such deposits constitute the third successive industrially important group of tin ores. They take the shape of quartz veins and cassiterite-impregnated zones. Average tin content in such deposits ranges from 0,2 to 0,3%.
  • solubilizing the solders comprising mainly tin and lead optionally omitting solubilization of other metals (such as copper);
  • hydrochloric acid is a hydracid, which enables selective solubilization of tin and lead (solder alloy components) without simultaneous disturbing other elements made of metals of higher (positive) stand- ard potential, such as for example copper. This allows to selective transfer both metals into the solution in the cation form simultaneously separating them from the matrix containing more noble metals.
  • Lead (II) chloride is relatively well soluble i aqueous solutions at significantly higher temperature. Cooling the solution will lead thus to precipitation of lead chloride as a white deposit.
  • electrolytic methods To selectively separate tin and lead compounds contained in the solution it is also proposed, apart of using specific reagents, use of electrolytic methods. For example, such methods, which allow relatively simple separation of tin from lead, are disclosed in the patent specifications PL-49664“Process for the production of secondary tin from met- allurgical waste” and US 3394061 A“Tin recovery” USA, 1968 r. and US 2319887 A “Hydrometallurgical process for the recovery of tin”, 1943 r.
  • the metallic form of tin is obtained by electrolysis of the concentrated solution thereof treated by an excess of HC1 to avoid uncontrolled increase of pH caused by the progressing electrolysis process.
  • chloride solutions in the presence of a great excess of hydrochloric acid chloride complexes of tin (II) are formed according to the following chemical reactions:
  • This rea- gent being an organic chloro derivative, is its high toxicity against living organisms and natural environment.
  • Use of trichloroacetic acid requires thus employment of strictly closed circulation during the tin recovery process.
  • a significant disadvantage of using trichloroacetic acid is also the high price of the reagent.
  • titanium (IV) salt in the highly acidic environment.
  • both titanium and tin present in the solution are not able to hydrolyse resulting in appearance of sparingly soluble hydroxysalt precipi tates.
  • the system containing the cations listed is subjected to hydrolysis in the final step, to isolate from it tin and lead as separate phases. Titanium (III) cations left in the solution can be oxidised in the highly acidic environment to titanium (IV) cations by activity of oxidis ing agents.
  • the patent application PL-408674 discloses a method for the re covery of tin material from the electronic scrap, according to which the electronic scrap containing tin material is provided, then the tin material from the electronic scrap is solu bilized by a solubilizing solution comprising the organic acid such as alkanosulphonic acid to give a solution for the electrolysis and the electronic scrap after the solubilization essen- tially free from the tin material, followed by passing the electronic scrap to the further pro cessing and subjecting the solution for the electrolysis to the electrolysis to provide the tin material and the spent solution after the electrolysis.
  • a solubilizing solution comprising the organic acid such as alkanosulphonic acid
  • the tin material obtained according to this electrolytic process and the spent electrolysis solution are passed to further processing.
  • the solubilization of tin-lead solders contained in the waste electronic materials is conducted according to this description in the solution of methanesulphonic acid containing additionally potassium nitrate as an oxidising agent.
  • Such processing results in obtaining well soluble methanesulphonate salts of lead (II) and tin (II).
  • Isolation of the tin from lead salt is carried out by precipitating out a sparingly sol- uble tin salt with oxalic acid.
  • a reduction of the obtained oxide with carbon is carried out at relatively low temperatures below 600°C.
  • the presented solu- tion is actually well developed and leads to good final outcome.
  • a disadvantages of this procedure is its multistep character and costs, since use of oxalic acid, which is not sub- jected to regeneration, raises the price of the recovered tin.
  • nitric acid A component commonly used in such solutions is nitric acid.
  • nitric acid has a number of advantages as a solubilizing agent for processing the e-waste. First of all, many, if not all, metal nitrates prepared by dissolving metals in nitric acid are soluble in the same acid and do not form precipitates.
  • any undesired releasing of hydrogen is ob- served (apart of a few exceptions comprising some transition metals 3d, 4d and 5d and lanthanides), and thereby no depletion of the acid takes place and there is no need to make it up continuously (as it is the case for mineral acids such as sulphuric, phosphoric or al- ready mentioned hydrochloric acid.
  • the publication WO 2009/129271 discloses a method for the recovery of a metal, such as tin, in the form of its oxide or nitrate utilizing as a sol- ubilizing solution for metals a nitric acid bath, where precipitation is conducted by raising pH of the bath by adding a base such as potassium hydroxide, ammonia, potassium car bonate or ammonium carbonate, or else by changing the temperature of the solution.
  • a base such as potassium hydroxide, ammonia, potassium car bonate or ammonium carbonate, or else by changing the temperature of the solution.
  • the method pertains to recovery of a metal from the scrap, such as the electronic scrap, which is subjected to comminution in the particularly preferred embodiment.
  • a method is proposed, as described in the application WO2013/104895, providing use of a regenerative solution with a particular composition, such as a solution comprising nitric acid and iron (III) chloride.
  • a regenerative solution with a particular composition, such as a solution comprising nitric acid and iron (III) chloride.
  • a strong inorganic acid such as hydrochloric acid.
  • Metals, particularly ones present in the alloys used for the manufacture of the printed-circuit boards, are separated by gradual, stepwise raising pH of the regenerative solution.
  • the method is relatively inefficient, with about 30-40% of metals being left in a sludge.
  • tin is contaminated with other elements such as iron.
  • the present inventors discovered unexpectedly that due to adequate selection of a washing bath based on environmentally safe diluted nitric acid, it is possible in a safe, environmentally friendly and economical way to isolate selectively tin as tin oxide of a high level of purity from tin-containing materials such as the electronic scrap. Moreover, due to a proposed specific environment for conducting thermal decomposition of tin oxide to metallic tin which allows the temperature of such decomposition to be lowered, the method is much safer and energy efficient. Object of the invention
  • the present invention provides a method for the selective recovery of tin from a tin-containing material, comprising: pretreatment of the tin-containing material comprising its comminution and removal of ferromagnetic grains and non-ferromagnetic metals, solu bilization of the pretreated material comprising exposing the treated tin-containing material to the operation of a washing bath containing nitric acid, and isolation of tin from the washing bath in the form of tin dioxide and optionally further steps of converting tin diox ide to metallic tin wherein in the method: a) the tin-containing material is subjected to initial selection and comminuted into a granulate, which finally in its largest dimension does not exceed 3 mm;
  • the material comminuted into the granulate is purified by rinsing with an organic solvent selected from common alcohols, inorganic solvents such as bases and their aqueous solutions to remove varnish films present on the tin-containing material; e) the rinsed and stripped from outer varnish films, free from ferromagnetic grains and non-ferromagnetic metals tin-containing comminuted material is solubilized by ex posing it to the operation of a washing bath containing diluted nitric (V) acid for the selective solubilization of tin and isolating it in the form of tin dioxide; followed by optionally purifying the obtained tin dioxide; and
  • step f) the purified tin dioxide obtained in step e) is smelted to give metallic tin; and g) water comprising an environment for the purification and solubilization steps is re generated by recycling it into the solution to dilute concentrated nitric (V) acid to prepare the diluted nitric acid solution as the washing bath.
  • the tin-containing material comprises preferably the electronic scrap, and ele ments of the electronic scrap such as printed-circuit boards.
  • the tin-containing material is com minuted by means of a hammer and knife mill.
  • the sol- vent used for purifying in step d) the granulate of the tin-containing material before sub- jecting to solubilization in step e) is a common alcohol selected from methanol, ethanol, mixtures and aqueous solutions thereof.
  • the solvent is a base selected from aqueous solutions of NaOH, KOH and mixtures thereof, preferably comprising an aqueous NaOH solution.
  • a washing bath for the selective solubilization of tin from a tin- containing material the aqueous solution of nitric (V) acid of the concentration of 1-5% by volume, preferably of the concentration of 2% by volume is used.
  • the magnetic separation of the tin-containing material is conducted by using one or an assembly of permanent magnets.
  • the electrodynamic separation is conducted by using a separator with magnetoelectric induction.
  • the granulate free from the ferromagnetic grains and non-ferromagnetic metals removed in steps b)-c) is subjected to assessment of its chemical composition to demonstrate absence in the granulate of ferromagnetic metals and aluminium.
  • the assessment of the chemical composition of the granulate indicates the presence of ferromagnetic metals and aluminium
  • the granulate is again subjected to the magnetic and electrodynamic separation defined in steps b) and c) of the method.
  • the solubilization step e) is con- ducted at the temperature not higher than the room temperature to restrict conversion lead (V) nitrate to lead oxide and lead dioxide.
  • the room temperature according to the present invention is a temperature in the range of l5-25°C, and particularly in the range of 21- 23°C.
  • the solubilized granulate is rinsed with water to wash out from its surface the remainders of the oxide phase.
  • the solubilized granulate is subjected to assessment of its chemical composition.
  • tin dioxide obtained in step e) is purified by washing the suspension of tin dioxide at the room or elevated temper ature with the 5-15%, preferably 10% aqueous acetic acid solution for no longer than one hour, followed by the determination of a contamination level of tin oxide (IV) with lead compounds, and in the case of the impurity level higher than 2% by weight, the suspension of tin dioxide is washed again.
  • washing the suspension of tin oxide with the acetic acid solution is conducted at the temperature not exceeding 85°C, prefera bly at the temperature in the range of l8-25°C, most preferably at the temperature about 20°C.
  • the solid oxide fraction is calcined additionally at the temperature of 500-800°C in the presence of carbon such as the wood charcoal.
  • the purified tin dioxide obtained in step f) is smelted to give metallic tin.
  • the smelting of tin oxide is conducted in the molten sodium carbonate at the temperature 1050-1 l50°C in the presence of carbon.
  • the mol ten sodium carbonate is used in at least onefold weight excess of the smelted tin dioxide, at the ratio to the smelted tin dioxide from 1 : 1,9 to 1 :2,1.
  • carbon is the wood charcoal.
  • the solu- tions remaining after conducting the steps of the selective tin acquisition and purification of the tin-compound containing oxide fraction e) are subjected to the selective precipitation by the precipitating agent to precipitate the lead ions present in the solutions.
  • the lead ions are precipitated as lead carbonate by adding calcium bi- carbonate prepared by means of saturating the suspension of calcium carbonate with car bon dioxide prepared during the thermal reduction of tin (IV) oxide to metallic tin.
  • the copper (II) cation-containing aqueous solution forming after the precipitation of the lead salt is recycled as the nitric (V) acid diluent used in step e) as the washing bath for the selective solubilization of tin from a tin-containing material, comprising the regenerat ed washing bath supplied, if necessary, with concentrated nitric acid in an amount suffi cient to obtain the desired concentration of the nitric acid in the range of from 1 to 5% by volume.
  • the regenerated washing bath contains an agent enhancing the oxidising efficiency of the bath in the form of the copper cations.
  • Another object of the present invention is a method for the purification of tin dioxide contaminated with lead oxides, wherein tin dioxide contaminated with lead oxides is smelted in the molten sodium carbonate at the temperature of 1050-1 l50°C in the pres ence of carbon to give metallic tin.
  • the molten sodium carbonate is used in at least single weight excess of the smelted tin dioxide, at the ratio to the smelted tin dioxide from 1 : 1,9 to 1 :2,1.
  • carbon is the wood charcoal.
  • the object of the present invention is also use of the diluted nitric (V) acid o of the concentration not exceeding 5% by volume, preferably of the concentration of 1-5% by volume, most preferably of the concentration of 2% by volume as the washing bath for the selective washing out tin from a tin-containing material.
  • the tin-containing ma- terial is an electronic scrap, and especially preferably elements of the electronic scrap such as printed-circuit boards.
  • Yet another object of the present invention is use od the molten sodium car bonate as a fluxing agent comprising the environment for conducting the thermal reduction of tin dioxide to metallic tin.
  • the thermal reduction is conducted at the tempera- ture of 1050-1 l50°C.
  • the amount of the fluxing agent for smelted tin oxide is from 1 : 1,9 to 1 :2,1.
  • the present invention provides also a reactor (1) for selective washing of the oxide suspension in the process of the selective separation of tin from a tin-containing ma- terial in the granulate form, preferably the electronic scrap, comprising a reaction vessel (2) including:
  • reaction chamber (4) for conducting washing out metallic tin from the granulate of the electrochemical scrap by means of the bath and
  • baffle (6) for holding the granulate of the electrochemical scrap during washing by means of the bath, comprising openings (7) to ensure the frre flow of the bath and the oxide suspension from the granulate of the electrochemical scrap to the reaction chamber below (4) the baffle (6), which baffle (6) is adapted for removing from the reactor (1) the granulate of the electrochemical scrap after washing metallic tin.
  • the baffle (6) comprises a moving screen, more preferably the baffle (6) is located in a basket for the granulate of the electrochemical scrap.
  • the reactor for the selective collection of the oxide suspension according to the invention is connected to a centrifuge to facilitate quantitative separation of the oxide suspension.
  • the baffle (6) is located in the reaction vessel (2) in parallel to the base (3).
  • the base (3) has a circular shape, and side walls (4) form one cylinder-shaped side wall.
  • Fig. 1 shows a scheme of the reactor for the selective washing out tin
  • Fig. 2 shows a diagram of the processing of the electronic scrap granulate, wherein the final products of the method were marked grey;
  • FIG. 3 shows photographs of the granulate (Fig. 3a) and e-scrap elements (Fig. 3b) respec- tively, before the treatment for the solubilization and selective acquisition of metallic tin and photographs of the granulate (Fig. 3c) of e-scrap elements (Fig. 3d) respectively after the treatment with the solubilization and selective acquisition of metallic tin.
  • the present invention provides a method for the recovery of metallic tin from the electronic scrap, in particular the electronic scrap elements such as printed-circuit boards or metal elements, the method comprising the following steps:
  • the chemically heterogenous mass of the waste materials should be sub- jected to properly configured pretreatment.
  • the pretreatment comprises several basic oper- ations: preselection and classification of the scrap;
  • magnetic separation by means of one or a assembly of permanent magnets of suita- bly selected characteristics of the magnetic field and the size of the slit between a magnetic separator and a belt, for separating the ferromagnetic grains from the granulate;
  • electrodynamic separation by means of a separator employing the magnetoelectric induction, to enable separation of non-ferromagnetic metals, which basically corresponds the separation of fragments of pure aluminium and copper from the fraction containing a mixture of the remaining metallic components, including tin alloys as films deposited on copper or plastic (laminate) supports; and
  • an organic solvent such as common alcohols, in particular denatured alcohol or other inorganic solvents suitable for removing fats, such as the solutions of bases, particularly aqueous NaOH and KOH solutions or mix tures thereof for removing varnish films present on the electronic scrap elements.
  • the end product in this step is the electronic scrap granulate of the grain size not exceeding 3 mm and a definite (repeatable) chemical composition confirmed by means of independent chemical analyses.
  • the granulate is deemed to be ready for the further pro- cessing steps, if the chemical composition of the inorganic (metallic) part does not indicate the presence of ferromagnetic metals and aluminium, and the major metallic components are: Cu, Sn, Pb and to the smaller extent Bi and Ag.
  • the second step of the method for the selective recovery of tin comprises prep- aration of the chemical bath capable for the selective solubilization of metallic tin often comprising galvanically applied external layer of metal or solder elements on the electronic boards.
  • the components of the chemical bath used known here also as the washing bath, are characterized by their oxidative activity. Their selection is made with respect to the differences in reactivity between tin and other metals present in the processed material.
  • the obvious advantage of such a bath is providing the selective method for the acquisition of tin which does not demand running specific, laborious operations of separating tin from the remaining metals (mainly Cu, Pb, Ag et al.).
  • the suggested agent providing selective solubilization of films made of tin-lead solder with leaving out in a significant extent the copper support is diluted nitric (V) acid of the concentration in the range of 1 - 5% by weight, and particularly of the concentration of 2%. Under the action of diluted nitric (V) acid tin and lead contained in the granulate and, to a very small extent, copper, undergo oxidation.
  • V nitric
  • Raising the temperature of the solubilization step favours conversion of lead (V) nitrate to the oxide, and subsequently to lead dioxide.
  • Nitric (II) oxide which evolves in small amounts is absorbed in water scrubbers, recycled and used for the secondary gen eration of nitric acid.
  • Use of more concentrated nitric (V) acid, with concentrations greater than 5% by volume, or excessive raise of the washing step temperature to above 85°C can lead to intensification of decomposition of lead (V) nitrate to their undesirable, water- insoluble oxide forms.
  • the major product of the above-indicated reaction will be tin (IV) oxide, Sn0 2 , in a fine-grained form, contaminated to a small extent with lead and copper com pounds.
  • the separated metal-electronic elements are additionally rinsed with water to wash out from their surfaces the remainders of the oxide phase.
  • the reaction system comprises three phases: two solid phases, i.e. the elec tronic scrap granulate depleted in tin (enriched in copper) and the oxide fraction, and the liquid phase - the solution.
  • the method according to the invention should be conducted in a special reactor dedicated for conducting phase separation which allows to selectively collect the oxide suspension separated from electronic parts even in the course of washing out tin.
  • a reactor dedicated to the separation of the forming phases is shown sche matically in Fig. 1.
  • the reactor (1) which allows to selective- ly collect the oxide suspension has a shape of a reaction vessel (2) open at one side, com prising a base (3) and side walls (4), which in the case of the base (3’) having a circular shape, form one cylinder-shaped side wall (4’), and which reaction vessel (2) comprises a reaction chamber (5) for introducing a chemical bath capable for the selective solubiliza tion of metallic tin for conducting washing out metallic tin from the electronic scrap granu- late by means of the bath, divided by a baffle (6) located within the reaction vessel (2) for holding the electronic scrap granulate during washing out metallic tin by means of the bath, preferably a movable one, moving along the side walls (4) of the reaction vessel (2), in the direction essentially perpendicular to the base (3), which baffle (6) is provided with openings (7) of a diameter smaller than the size of the granulate located in the moving bas- ket (6) and subjected to washing, which provide free flow of the solution
  • the baffle (6) is adapted for removing from the reactor (1) the electronic scrap granulate after washing out metallic tin.
  • the moving basket (6) due to movable arrangement of the moving basket (6) simple separation of the washed granulate from the oxide precipitate and isolation of the granulate located in the moving basket (6) performing the function of a screen is possible.
  • the moving basket (6) is located in the reaction vessel (2) in parallel to the base
  • the reactor according to the invention is connected to a centri fuge to facilitate quantitative separation of the oxide suspension.
  • Average contents of metals in the obtained oxide fraction are respectively: Sn 68 - 70%, Pb 12 - 16%, Cu 0,5 - 1,0%, Ag 0,3 - 0,6%, Bi ⁇ 0,2%.
  • the suggested approach allows to obtain minimum 60% efficiency of solubiliz ing tin and tin alloy layers to the fine-grained fraction form enriched in tin (IV) oxide.
  • the washing efficiency is determined on the basis of a specification of results of chemical analyses concerning the averaged contents of metallic tin present before the washing in the granulate and the averaged contents of metallic tin present after the washing in the fine- grained amorphous oxide fraction.
  • the third step of the method according to the invention embraces the entirety of operations resolving itself into the purification of the fine-grained oxide fraction separated from the aqueous suspension.
  • the co-precipitated and occluded small amounts of compounds of other metals, mainly lead present as the nitrate (V) and oxide and copper present as the nitrate (V) are passed into the solution and the tin (IV) oxide form as pure as possible is obtained.
  • the purification process comprises rinsing at the temperature not higher than 85°C the suspension of tin oxide with 10% acetic acid (CH 3 COOH) solution for a specified period, not longer than for one hour (1 h). After that period, the level of tin (IV) oxide im purities in the isolated oxide fraction is determined. In the case of unsatifactory results, if the impurity level is determined as higher than above 2% by weight, the above-indicated purification operation of the tin oxide suspension should be repeated.
  • Lead (V) nitrate formed in step 2 that is the step of solubilizing the tin-lead films, is water soluble at the significant level, which enables its separation from the solid oxide fraction.
  • the purification process of the oxide tin fraction can be deemed completed, when contents of lead and copper does not exceed respectively 2% and 0,5% by weight. The remaining impurities in the silver oxide and bismuth forms do not exceed levels for silver and bismuth 0,8% and 0,2% by weight, respectively.
  • the soluble copper and lead compounds and, though to positively lower degree, the silver compounds are concentrated.
  • the essential element of the purification process which positively lowers environmental nuisance of the proposed solution providing the method for the selective recovery of tin, is separation of these metals and regeneration of water employed in this process.
  • the obtained purified tin (IV) oxide will be subsequently subjected to reduction resulting in smelting of metallic tin.
  • step 3 The main purpose of step 3 is providing tin oxide (IV) of a high level of purity (at least 95%), which is a valuable commercial product and which could be commercially utilized without any need for further treatment.
  • tin dioxide obtained in step 3 of the method of the present invention is subjected to further treatment - a reduction process - which leads to obtaining the desired product in the form of metallic tin.
  • purity of tin oxide (IV) determines purity of metallic tin obtained in the subse- quent step. It should be noted that the presence of lead in the oxide form of tin at a level higher than 2% by weight does not put any obstacle in conduction the process of thermal reduction of tin oxide.
  • Step 4 The subsequent step of the discussed method for the selective recovery of tin from the electronic waste is conducting thermal reduction of tin (IV) oxide to metallic tin in the case of a sufficiently purified fraction of tin dioxide or to the tin and lead alloy in the case of a more contaminated fraction of tin dioxide.
  • tin (IV) oxide to metallic tin in the case of a sufficiently purified fraction of tin dioxide or to the tin and lead alloy in the case of a more contaminated fraction of tin dioxide.
  • Preparation of the feed for suitably designed furnace consists in selection of: a) suitable fluxing agents and reducing agents;
  • the step of thermal reduction of the purified tin (IV) oxide is conducted in the presence of an excess (at least a onefold ex- cess by weight) of the molten sodium carbonate in the presence of carbon (for example, carbon in the form of the wood charcoal).
  • carbon for example, carbon in the form of the wood charcoal.
  • Sodium carbonate employed in this step pro- vides alkaline environment of the reaction, in which a more easily reducible form of tin oxide is formed.
  • the melting point of sodium carbonate is 85l°C. Above this temperature, decomposition of sodium carbonate to sodium oxide increases. For that reason it is indis- pensable to use a significant excess of this reagent in relation to the amount resulting from stoichiometry of the reaction.
  • the important element of the technology under development jest selective sepa- ration of lead from the solution obtained after purification of tin oxide fraction.
  • a suggest- ed selective agent for precipitation of lead ions from the solution containing also copper cations is calcium bicarbonate prepared by saturating the suspension of calcium carbonate with carbon dioxide obtained in high amounts in the method of the invention in step 4 - during the thermal reduction of tin (IV) oxide. Solubility of lead carbonate is about one order of magnitude lower as compare to the solubility of copper carbonate. Lead carbonate obtained can be an additional commercial product of the processing line.
  • the copper (II) cation-containing aqueous solution obtained after the separation of a lead salt is recycled as a dilution medium for nitric (V) acid used in step 2 as the washing bath for the solubiliza tion of tin solders.
  • An additional factor which enhances effectiveness of oxidative activity of such a regenerated bath is the presence of copper cations in the recycled solution.
  • the suggested technology of processing the electronic scrap to acquire tin is characterized by relative simplicity of proceeding, is environmentally friendly (closed re- cycle of the reagents) and leads to obtaining metallic tin of the high purity and other com spillal products.
  • the suggested technology employs reagents which are non-toxic, inexpensive and widely used in numerous industrial processes. Any of the steps of the suggested technology of obtaining metallic tin generates additional by-products which could be toxic materials.
  • the experimental studied conducted to the present day demonstrated that the technology allows to recycle Sn/Pb with the high yield reaching 85-90%.
  • Example 1 selective recovery of tin from e-scrap
  • Tests of the developed method was conducted with 10 kg of the granulate from the class C printed-circuit boards free from ferromagnetic elements, as shown in Fig. 3a.
  • the process of comminuting the board to form the granulate was conducted with initial use of the hammer mill to remove ceramic parts of the boards, and then the knife mill with suitably selected set of screens with mesh diameter of from 8 to 3 mm to provide the gran ulate with its largest dimension not exceeding 3 mm, and removing additionally varnish films having been applied onto connections and tracks covered by the tin solder.
  • the washed granulate was cleaned in a denatured alcohol to provide the purified granulate with exposed metallic elements and solders.
  • the operation of diluted nitric (V) acid does not provide the expected effect of the selective solubilization of tin present in the granulated material.
  • the provided granulate was introduced into 10 litres of 2% nitric (V) acid.
  • the contents of the reactor was vigorously stirred all the time until voluminous white pre- cipitate of the oxide tin fraction was formed.
  • the aqueous suspen sion of tin (IV) oxide was separated from the metallic residue enriched with copper, and depleted in tin and lead.
  • the weight of the residue containing copper in the first place was 8,5 kg.
  • Tin oxide contaminated with insoluble lead compounds (mainly in the oxide form) was separated by decanting from the aqueous solution comprising lead as soluble nitrate (V). The separated oxide tin fraction contaminated with compounds of lead was added to
  • the crucible contents was transferred to a metallic form to obtain 0,64 kg of the Sn/Pb alloy containing 73% of tin, 23% of lead, 2% of copper, 0.8% of silver.
  • the residue weighing 0,31 kg as a slag comprised a mixture of sodium oxide/sodium carbonate, compounds of tin and a negligible level of lead (below 1%).
  • Average efficiency of the tin recovery obtained in the present method was 60%.
  • Example 2 thermal reduction of pure tin (IV) oxide in the molten sodium carbonate with addition of carbon
  • the sample of tin (IV) oxide of the purity of 98% and the weight of 50 g was mixed with 150 g of sodium carbonate and 25 g of the wood charcoal.
  • the mixture was homogenised and added to a graphite crucible, which was then inserted into a resistance furnace at the temperature of l050°C. After the contents of the crucible was melted, the whole was held at the indicated temperature for about 40 minutes. After this period the contents of the crucible was transferred to a steel mould, the smelted metal was weighed and reduction yield determined. Average yield determined for 4 analogous tests was 80 - 95%. For each consecutive test the yield decreased slightly for about 5%. Due to corrosion cause by the action of emerging gases which penetrated easily the porous structure of the crucible material, the graphite crucible used was being consumed.

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Abstract

La présente invention concerne un procédé de récupération sélective de l'étain à partir d'un matériau contenant de l'étain, de préférence les déchets électroniques, et en particulier les cartes de circuit imprimé, le procédé comprenant un prétraitement du matériau contenant de l'étain, une solubilisation sélective du matériau prétraité pour précipiter de façon sélective des composés d'étain, comprenant l'exposition du matériau prétraité contenant de l'étain à l'opération d'un bain de lavage contenant de l'acide nitrique (V) et l'isolement de l'étain du bain de lavage en tant qu'oxyde d'étain (IV). La présente invention porte également sur un réacteur utile pour la solubilisation sélective du matériau contenant de l'étain. L'invention se rapporte également à un procédé de purification du dioxyde d'étain contaminé par des oxydes de plomb pour donner de l'étain métallique au moyen d'un traitement thermique réalisé en présence d'un nouvel agent fluxant et de l'utilisation d'un nouvel agent fluxant comme environnement pour effectuer une réduction thermique du dioxyde d'étain en étain métallique.
PCT/IB2019/052273 2018-03-20 2019-03-20 Procédé de récupération sélective de l'étain et réacteur destiné à être utilisé dans ledit procédé WO2019180642A1 (fr)

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CN112517616A (zh) * 2020-12-11 2021-03-19 惠州市宁泰林环境科技有限公司 一种废弃电路板中金属的回收方法
CN114196835A (zh) * 2021-12-17 2022-03-18 郑州大学 一种从含锡冶金渣中选择性浸出锡的方法
RU2790720C1 (ru) * 2021-12-27 2023-02-28 Аркадий Нахимович Фейгельман Способ получения катодной меди из вторичного сырья
IT202200008912A1 (it) * 2022-05-03 2023-11-03 Pietro Bozzi Processo di estrazione sequenziale e recupero di metalli da dispositivi elettrici o elettronici di scarto
WO2023237859A1 (fr) 2022-06-07 2023-12-14 Kaseum Holdings Limited Appareil et procédé de coupe d'un élément tubulaire dans un puits de pétrole ou de gaz
WO2024084208A1 (fr) 2022-10-21 2024-04-25 Kaseum Holdings Limited Appareil et procédé

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Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN112517616A (zh) * 2020-12-11 2021-03-19 惠州市宁泰林环境科技有限公司 一种废弃电路板中金属的回收方法
CN114196835A (zh) * 2021-12-17 2022-03-18 郑州大学 一种从含锡冶金渣中选择性浸出锡的方法
CN114196835B (zh) * 2021-12-17 2023-10-03 郑州大学 一种从含锡冶金渣中选择性浸出锡的方法
RU2790720C1 (ru) * 2021-12-27 2023-02-28 Аркадий Нахимович Фейгельман Способ получения катодной меди из вторичного сырья
IT202200008912A1 (it) * 2022-05-03 2023-11-03 Pietro Bozzi Processo di estrazione sequenziale e recupero di metalli da dispositivi elettrici o elettronici di scarto
WO2023237859A1 (fr) 2022-06-07 2023-12-14 Kaseum Holdings Limited Appareil et procédé de coupe d'un élément tubulaire dans un puits de pétrole ou de gaz
WO2024084208A1 (fr) 2022-10-21 2024-04-25 Kaseum Holdings Limited Appareil et procédé

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