JP2014529681A - Recovery of lead and indium from glass, mainly electronic waste materials - Google Patents

Abstract

Lead and / or indium can be recovered from a cullet containing indium and / or lead, such as a cullet from a CRT or flat panel display. A chloride salt melt containing AlCl3 is used to dissolve the cullet. The melt can be electrolyzed and lead and / or indium and other metals can be selectively electrodeposited from the salt melt. These two steps can be combined in a continuous process. The salt in the salt melt is not consumed and can be recycled (except for the flux resulting from alumina and chlorine gas formation). Salt melting by evaporating lead chloride and / or indium and other metals by vaporizing and condensing the respective chlorides or by leaching the salt phase in water and extracting the metals as hydroxides by wet refining It can also be recovered from things.

Description

  The present invention relates to a method for recovering lead and / or indium from glass containing PbO and / or indium oxide, mainly from electronic waste material.

Background Art Lead is used in radiation shielding glass to absorb gamma rays, X-rays, etc., for example, cathode ray tubes used in computer screens and television sets that are considered to reduce the viewer's exposure to soft X-rays. Used in CRT and the like.

  Modern CRTs have an essentially lead-free glass front panel, followed by a lead glass funnel and a highly leaded glass neck at the far end. Such CRTs exhibit environmental destruction if discarded inappropriately. In October 2001, the US Environmental Protection Agency established a rule that CRT must be brought into a special recycling facility. In November 2002, EPA began to impose a fine on companies that disposed of CRT by landfill or incineration. Regulators monitor the disposal of CRTs and other computer equipment locally and throughout the country. In Europe, the disposal of CRT televisions and monitors is covered by the WEEE Directive 2002/96 / EC.

  CRT monitors constitute about 6% of electronic waste in Europe, and about 450,000 tons of CRT monitors are disposed of every year in Europe. Because no effective recycling system is available, 70% of all CRT monitors are dumped in landfills or exported abroad. As pointed out, CRT screens are becoming a major problem, especially in countries that manufacture these monitors, such as Japan, the United States, and Taiwan. Many countries treat CRT waste by sending it to developing countries in exchange for money to avoid regulatory procedures. However, this is a temporary solution and new techniques are being developed to find more effective ways to extract lead and other harmful components that should be separated from the glass. The remaining 70% of CRT monitors contain 33300 tons of lead oxide. When calculated as pure lead, approximately 31,000 tons of lead is dumped into landfills every year in Europe.

  A major concern for CRT screen dumping is the leaching of lead from the glass. Leached lead is dangerous for both humans and the environment. CRT screen dumping occurs mainly in developing countries. This is a big problem for homeless people, both adults and children, because living in and around abandoned dumped items is very common. These people are therefore very exposed to lead leached from the screen by rainwater. Therefore, many people who live around abandoned dumped objects are poisoned by lead through routine exposure. The most common route for exposed people to become lead poisoning is that they are drinking high amounts of water. Lead can also spread on land via air, by mining, and by direct discharge to water and land. It takes a very long time for lead to form a harmless compound in nature. The big problem is when lead spreads to farms and arable land. When this happens, people are exposed to lead poisoning because they eat fruits and vegetables grown in these lands. Both adults and children, when they eat meat from animals grazed on land that has been exposed to lead, from industrial wastes discharged into the sea and lakes, from derelict dumps and landfills They can also be affected when they eat fish affected by lead from leachate or effluent from sewage. No safe threshold has been found for lead exposure-that is, no amount of lead is known that is too small to cause harm to the body.

  Research on chopping CRT glass into cullet (small glass pieces) and reusing them for CRT has been done by the Home Appliances Association. Among these studies, a system has been developed in which a cathode ray tube is taken out from a television body and the cathode ray tube is shredded into a glass cullet (see, for example, “Electrotechnology”, January 1997).

  A method for recovering glass as cullet is disclosed, for example, in JP-A-61-50688. Further, there is known a method of chopping a cathode ray tube glass into a cullet (small glass piece) and reusing them for the cathode ray tube (for example, JP-A-9-193762). A method of dividing a cathode ray tube into a face plate and a funnel corresponding to the material and chopping them into a cullet is disclosed in, for example, Japanese Patent Application Laid-Open No. 05-185064. Further, JP-A-7-037509 discloses a method in which a cathode ray tube is divided into a face plate and a funnel, a fluorescent material and a black mask are peeled off from the face plate, and the face plate is recycled.

  To recycle CRT glass, the glass must be separated into panel glass and lead-containing funnel glass. The reason is that when a predetermined amount or more of lead is mixed into the panel glass, a browning phenomenon occurs, and the lead-containing glass cannot be reused as a raw material for the panel glass. For this reason, the cathode ray tube is separated into a panel and a funnel. For this purpose, a method for deciding a position for cutting a cathode ray tube (Japanese Patent Laid-Open No. 9-115449) or a method for melting a frit glass for joining a panel and a funnel to separate the panel and the funnel (Japanese Patent Laid-Open No. 7-1990). No. 45198) has been proposed.

  WO 2009/139715 A1 discloses a method for chlorinating ores, slag, mill scale, scrap, dust and other resources containing recoverable metals from groups 4-6, 8-12 and 14 of the periodic table ing. It is well known that valuable metals can be recovered by chlorination from many sources such as scrap, ore, and sea nodules. The formed metal chloride can then be separated and extracted by fractional distillation and condensation, salt electrolysis, or by a wet refining process. However, in order to obtain much higher reaction rates and valuable metal yields than are possible when ferric chloride and / or cupric chloride are used as chlorine donors, Aluminum chloride is used.

Furthermore, US4853094 discloses a method for producing a metal Me (eg Sn) or an alloy containing a metal Me from a metal halide MeX _n (eg SnCl ₄ ) by electrolysis in the cell, the cell comprising an anode, A liquid electrolyte comprising a liquid metal cathode containing one or more metals M (eg liquid Zn) and a salt melt of one or more alkali metals or alkaline earth metal halides (eg LiCl / KCl mixtures). This method is selected from metal halide MeX _n (where Me is a periodic table 2b, 3b (including lanthanide and actinide systems), 7b and 8 groups, and Cr, Cu, Au, Ga, Sn, Pb and Bi). And X represents halogen, and n represents the valence of the metal Me) into the liquid metal cathode, and the separation of the Me or Me-containing alloy from the metal cathode material.

  Journal of Hazardous Materials 161 (1109-1113) Issus 2/3 2009 proposed a method of recovering lead by the pyrovacuum method. However, to the best of our knowledge, no commercially accepted method has been proposed to solve the problem of rendering glass from scrapped CRT funnels harmless by lead recovery.

  Another metal oxide that it is desirable to recover from glass is indium. Indium tin oxide (ITO) is one of the most widely used transparent conductive oxides, for example flat panel displays such as LCD, LED, OLED, PDP, antistatic coating, light emitting diodes and various supplies Used in the source. Indium may also be present as indium doped zinc oxide. Indium is expensive and its supply is low. Therefore, there is a need to recycle indium from glass existing in electronic waste materials with good profitability.

DESCRIPTION OF THE INVENTION The main object of the present invention is to recover metal oxides, especially lead or indium, from glass containing PbO and / or indium oxide, mainly from electronic waste materials.

This object is achieved according to the invention, the method comprising the following steps:
a) crushing the glass to produce a cullet;
b) by weight of the mixture,
A chloride salt composition consisting of at least two metal chlorides selected from the group consisting of 60 to 95 alkali metal chlorides and alkaline earth metal chlorides;
- 5 to 30 AlCl _3, and - optionally of 0, halide, additional chloride, to form a mixture of sulfides and / or oxides,
c) heating the mixture to form a salt melt;
d) dissolving cullet in the salt melt;
e) recovering at least one of lead and indium from the salt melt.

  This makes it possible to recover valuable metals from the glass and to essentially render the residue after this process harmless. For lead, lead extraction rates of over 95% can be achieved, thereby essentially detoxifying the residue after this process.

Preferably the amount of AlCl ₃ is in the range of 5-20% by weight of the mixture, more preferably 7-15% by weight and most preferably 8-13% by weight.

Preferably, the recovery of at least one of lead and indium from the melt includes the following steps:
-Electrolyzing the melt; and
-Selective electrodeposition of at least one of lead and indium.

  By selective electrodeposition, most of the oxides present in the glass can be recovered.

  During cullet dissolution, the temperature of the salt melt should preferably not exceed 1000 ° C., more preferably this temperature should not exceed 900 ° C., suitable during cullet dissolution and melt electrolysis. The temperature is at least approximately 500 ° C. The upper limit is set by the fact that at higher temperatures some chloride begins to evaporate from the melt. The lower limit is determined by the liquidus temperature of the salt bath. The operating temperature is preferably at least 100 ° C. higher than the liquidus temperature of the salt bath.

  Graphite rods are preferably used for anodes and cathodes during electrolysis due to their inertness and low cost. When collecting lead, it is preferred that a permeable cathode diaphragm is provided around the cathode to collect liquid lead. This is mainly to avoid contamination of the residue, which is almost pure silica, by liquid lead.

  Preferably, the cathode diaphragm is made of alumina and has a plurality of pores so that the solid residue cannot pass but the liquid molten salt electrolyte can permeate through the pores.

  Preferably, a voltage of 2-3V, more preferably 2.3-2.7V is used to extract lead by electrolysis, which has been found to be advantageous in preliminary tests. This is consistent with the cyclic voltammetry study using a graphite rod.

  Suitably, the melt is electrolyzed for a period of about 2-8 hours, preferably about 3-6 hours.

  Preferably, the weight ratio of flux to cullet is about 0.25 to 1.5, more preferably about 0.3 to 1.0. For lead-containing cullet, it is most preferably 0.35 to 0.45. The increase in flux content and flux / cullet ratio does not appear to contribute to the lead oxide extraction rate because the low flux content and flux / cullet already exhibit very high extraction rates.

  Preferably, the temperature is maintained for a period of approximately 4-8 hours during the dissolution process. The cullet will then be softened and valuable lead and / or indium will be extracted into the salt melt.

  It can be condensed to evaporate the metal chloride from the melt and later recover the condensed chloride metal. The metal chloride from the melt can also be recovered by leaching into water and extracted by wet refining to recover the metal as a hydroxide.

  After recovery of lead and / or indium and possibly other metals present in the cullet, the chloride salt of the melt can be recycled.

After recovery of lead and indium, and possibly other metals from the glass, a processing residue consisting essentially of Al ₂ O ₃ and SiO ₂ remains, which is used for landfills, building structures, It is also useful as a raw material for the refractory industry.

  Lead-containing glass is mainly derived from the funnel-like portion and / or neck portion of the cathode ray tube of a computer screen or television set.

Alternatively, at least one of lead and indium can be recovered by a method using a liquid aluminum anode. In this method, AlCl ₃ is generated by in situ formation during electrolysis. This method includes the following steps:
a) pulverizing glass to produce cullet;
b) preparing a crucible containing a chloride salt melt, an anode and at least one cathode connected to the salt melt, a heating means for heating the salt melt, and an aluminum melt present at the bottom of the crucible. Where the aluminum melt forms the anode or part of the anode;
c) supplying an initiating chlorine donor to the salt melt to initiate the reaction in the salt melt, wherein the starting chloride donor is electrolyzed in aluminum chloride and / or in step g. At least one metal chloride capable of forming aluminum chloride;
d) maintaining the temperature of the salt melt and the temperature of the aluminum melt at a temperature at which both are in the liquid phase;
e) introducing the cullet into the liquid salt melt;
f) reacting aluminum chloride as a chlorine donor with cullet to form at least one of lead chloride and indium chloride dissolved in the salt melt g) electrolyzing the salt melt and lead and indium at the cathode Selectively depositing at least one of the following, optionally using a cathode bag, and in situ forming aluminum chloride on the contact surface of the aluminum and salt melts;
h) A step of recovering at least one of lead and indium from the salt melt.

FIG. 3 shows an embodiment of the method according to the invention.

[Caret]
The cullet is prepared by grinding a glass containing PbO and / or indium oxide. The glass containing PbO is mainly derived from the funnel-like part and / or neck part of the cathode ray tube of a computer screen or a television set. Glass containing indium oxide is mainly derived from flat panel displays coated with indium tin oxide. Preferably, the PbO-containing glass and the indium oxide-containing glass are separated such that the cullet contains lead or indium. However, indium and lead can be recovered from the mixed cullet by selective electrodeposition.

[Salt composition]
Preferably, the salt composition, NaCl, KCl, consisting of at least two salts selected from the group of LiCl and CaCl _2, preferably NaCl, KCl, at least three salt selected from the group of LiCl and CaCl ₂ Become. Preferably, the composition is chosen such that the salt composition has a liquidus temperature of less than 700 ° C, preferably less than 600 ° C, more preferably less than 500 ° C. For a given combination of salts, the composition is preferably chosen to be within 10% by weight, more preferably within 5% by weight, most preferably within 1% by weight from the lowest eutectic point of the salt combination. . However, other contents can be used as long as the liquidus temperature of the combination of salts is at least 50 ° C. below the operating temperature during electrolysis, preferably 100 ° C. below the operating temperature.

  In a preferred embodiment, the salt composition is essentially 3 to 20 NaCl, 30 to 70 KCl, 20 to 60 LiCl, preferably 5 to 15 NaCl, 40 to 60 percent by weight of the salt composition. KCl, 30-50 LiCl, more preferably 7-12 NaCl, 45-55 KCl, 35-45 LiCl. Such a salt composition can provide low liquidus temperature (eutectic temperature of about 350 ° C.) and good conductivity at a relatively low cost.

In an alternative embodiment, the salt composition is essentially 10 to 50 NaCl, 2 to 20 KCl, 50 to 80 CaCl ₂ , preferably 25 to 35 NaCl, by weight percent of the salt composition. 3-10 of KCl, consisting of CaCl ₂ of 60 to 75.

In another alternative embodiment, the salt composition consists essentially, in weight percent of the salt composition, 5 to 20 NaCl, 20 to 40 of LiCl, CaCl ₂ 40 to 70, preferably NaCl of 7-15, 25 to 35 of LiCl, consisting of CaCl ₂ of 50 to 60.

In another alternative embodiment, the salt composition consists essentially of 35-65 KCl, 20-50 LiCl, 5-20 CaCl ₂ , preferably 45-55 KCl, by weight percent of the salt composition. 30 to 40 of LiCl, consisting of CaCl ₂ of 10 to 15.

[Dissolution]
In order to dissolve the cullet, preferably a mixture is provided, which mixture consists of: A) a chloride salt composition comprising at least two metal chlorides selected from the group consisting of alkali metal chlorides and alkaline earth metal chlorides, 60-95% by weight of the mixture, B) AlCl ₃ 5-30 wt%, C) optionally, halides, additional chlorides, sulfides and / or oxides (as non-limiting examples, CaO, Li ₂ O, NaO, MgCl ₂ , BaCl ₂ ) 0-10% by weight of the mixture. In the most preferred embodiment, the salt composition consists of NaCl, KCl, and LiCl, and has the lowest eutectic point composition of the NaCl-KCl-LiCl system. The mixture is heated to form a salt melt. The cullet can be added before heating the mixture or after the salt melt is formed. This mixture is heated in a refractory container under a protective atmosphere, preferably under argon, to form a melt. The atmosphere may be nitrogen. Further, chlorine gas may be mixed in a nitrogen or argon atmosphere. In order to dissolve the cullet, the melt is typically kept at an elevated temperature for a time between about 4 and about 8 hours. Generally, the amount of cullet is preferably such that the flux / cullet weight ratio is between about 0.25 and about 1.5, more preferably 0.30 to 1.0, and most preferably 0.35 to 0.45. Be made to be. The temperature should be below 1000 ° C, more preferably below 900 ° C. Otherwise, lead chloride may evaporate from the melt. For optimal economics, the temperature is preferably in the range of 550-700 ° C, more preferably 580-650 ° C, during cullet dissolution and melt electrolysis.

For PbO, the dissolution reaction is as follows:
3PbO + 2AlCl ₃ → 3PbCl ₂ + Al ₂ O ₃ (1a).

  A flux / cullet ratio of 0.37 appears to be sufficient to dissolve lead oxide in the salt melt.

For indium, the dissolution reaction is as follows:
In ₂ O ₃ + 2AlCl ₃ → 2InCl ₃ + Al ₂ O ₃ (1b).

  Since aluminum chloride is difficult to recover after extraction, it is desirable not to add excess aluminum chloride.

Various processes that are well known per se can be used to recover at least one of lead and indium from the melt. Interestingly, the salt melt used for extraction can be recycled. Lead and / or indium and other metals can be selectively electrodeposited from the salt melt. However, it is also possible to use metal chloride vaporization and its condensation, or to leach out a salt phase in water and extract the metal as a hydroxide by wet refining. The process can be designed to be continuous by combining the two steps. The anode off-gas from the subsequent electrolysis, Cl ₂ may be reused to enhance the dissolution of the slag / ore. The residue after glass treatment consists essentially of Al ₂ O ₃ and SiO ₂ and can be used for landfills, building structures, or as a raw material for the refractory industry.

[Electrolysis using conventional anode (s) and cathode (s)]
The electrolysis is preferably performed in a refractory vessel that holds the salt melt with dissolved cullet, and lead and / or indium and possibly other metals are recovered as cathode deposits.

In one embodiment, lead is recovered from the PbO-containing glass. Two electrodes made of graphite are immersed in a salt melt containing dissolved cullet and can be connected to a DC power source. The DC power supply can supply a DC current with a voltage of 2 to 3V, preferably 2.3 to 2.7V, so that the reaction shown below for lead occurs.
2Cl ⁻ → Cl ₂ (g) + 2e ⁻ (2),
Pb ²⁺ + 2e ⁻ → Pb (l) (3),
2Al ³⁺ + 3O ^2- → Al ₂ O ₃ (s) (4).

This is about 1 volt higher than the theoretical decomposition voltage for PbCl ₂ to compensate for polarization and other effects. The selected voltage is low enough to avoid decomposition of AlCl ₃ . The decomposition of AlCl _{3 in} the electrolytic process also requires an overvoltage with respect to the theoretical decomposition voltage of AlCl ₃ . In this case, 2.4 + 1 = 3.4V. Thus, at a voltage lower than 3V, electrolysis of AlCl ₃ is avoided.

  When the indium oxide is indium tin oxide, the indium can be co-deposited with Sn, or they may be selectively electrodeposited.

  Preferably, the batch of melt is electrolyzed for 2-8 hours. During electrolysis, the temperature is preferably maintained above 500 ° C, more preferably about 600 ° C.

  A permeable cathode bag may be provided around the cathode to collect liquid lead. The cathode bag is preferably made of alumina and has a plurality of holes through which ions can pass. The holes may be cuts extending in the circumferential direction.

After recovery of lead and / or indium, and possibly other metals, the molten chloride salt can be recycled. At that time, a processing residue consisting essentially of Al ₂ O ₃ and SiO ₂ remains, which is useful for landfills, building structures and as a raw material for the refractory industry. The lead-containing glass processed in accordance with the present invention is primarily derived from the funnel-like and / or neck portion of the cathode ray tube of a computer screen or television set.

[Dissolution and electrolysis using aluminum anode]
In an alternative embodiment, the aluminum melt forms an anode or part of an anode, for example by dipping an electrode (eg a graphite electrode) in the aluminum melt and connecting it positively during electrolysis. Alternatively, the crucible is at least partially made of a conductive material that contacts the aluminum melt, and the crucible is connected positively during electrolysis. Thereby, a crucible and molten aluminum operate | move as an anode. Of course, at least one cathode is also required during electrolysis, for example one or more graphite electrodes are submerged in the salt melt. Voltage.

  When using an aluminum melt at the bottom of the crucible as the anode or part of the anode, the salt melt and aluminum are heated to a temperature at which both are in the liquid phase. In order to improve the viscosity of the salt melt, the temperature of the salt melt is preferably at least 50 ° C. higher than the liquidus temperature of the salt melt, more preferably higher than the liquidus temperature of the salt melt. At least 100 ° C higher. The temperature should be at least 660 ° C. and below 1000 ° C., preferably the temperature is in the range of 700-900 ° C.

During electrolysis, metal (s) from metal chloride (s) are deposited on the cathode. At the contact surface between the salt melt and the aluminum melt, chloride ions react with the aluminum, thereby forming AlCl ₃ . This means that during steady state the salt melt can be fully or partially self-supporting with respect to AlCl ₃ and the chlorine gas emissions are reduced. Even when an aluminum melt is used as the anode or part of the anode, a smaller amount of chlorine gas can be produced. This gas can be recovered.

  At the cathode, the metal (s) are deposited in the liquid or solid state for the metal (s) having a melting point below the temperature of the salt melt. A permeable cathode bag may be provided around the cathode to collect liquid metal, such as lead. The cathode bag is preferably made of alumina and has a plurality of holes through which ions can pass. The hole may be a cut extending in the circumferential direction.

  The composition of the salt melt is preferably the same as when a conventional graphite anode (s) is used.

An initiating chloride donor is provided to initiate the reaction in the salt melt. Initiating chlorides donors may be aluminum chloride and / or electrolyte, i.e. such as chloride ions to form the AlCl ₃ in the contact surface between the salt melt and the aluminum melt, comprising at least one metal chloride Good.

  In one embodiment, the starting chloride donor is the same type of metal chloride provided in the chloride salt composition, such as Li, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr. , At least one metal chloride selected from the group consisting of chlorides of Ba and Ra.

  In a preferred embodiment, the starting chloride donor comprises aluminum chloride added to the mixture before its heating or added to the salt melt, the aluminum chloride being up to 20% by weight of the salt mixture, preferably 1 to 15% by weight, more preferably 5 to 10% by weight is added.

  When using an aluminum melt as an anode or part of an anode, the dissolution step and the recovery step by electrolysis are preferably accelerated for at least 2 hours at the same time.

  As indium and / or lead is deposited, additional cullet can be added to the salt melt stepwise or continuously. The electrolysis and dissolution operation can be performed, for example, for 2 to 8 hours; after (where after), the metal deposited on the cathode (s) is collected and electrolysis can be resumed. To avoid interruption of electrolysis, another “clean” electrode can be submerged. Alternatively, the salt melt may have multiple electrodes (actually activated as a cathode and the previous electrode deactivated). Thereby, metal can be selectively deposited on the individual electrodes.

The treated residue includes Al ₂ O ₃ and other stable oxides such as SiO ₂ .

[Example of lead recovery from a CRT monitor]
CRT glass samples were supplied by East Japan Recycle Systems Co., Ltd. (EJRS). The CRT monitor was dismantled and some parts were recycled. The CRT monitor processing by EJRS will be described below.

  The monitor was dismantled by hand and the cathode ray tube was separated. The printed circuit board, deflection yoke, wiring and speakers were also taken and recycled. The separated CRT was polished by a brush cleaning device to remove protrusions on the surface of the CRT. The panel and funnel were then separated by a P / F divider. Since the glass compositions of the panels and funnels are different, they must be recycled separately. The funnel glass was washed and dry scrubbed to remove the carbon and iron oxide paint on the glass surface, and then funnel cullet was made. This cullet is a raw material for CRT glass.

  As mentioned above, the glass used in CRTs is of a different type for CRT panels, funnels and necks. The panel contains barium-strontium glass and its weight is about two thirds of the total weight of the CRT monitor. The funnel is made of lead glass. Its weight is about one third of the total weight of the CRT monitor. The neck is made of high lead content glass and surrounds the electron gun.

  Two different analyzes were performed on the supplied funnel cullet. The results of the analysis are shown in Table 1, and two different analyzes are named CRT1 and CRT2.

  The metal chloride was supplied by Sigma-Aldrich, USA, and the refractory container was an alumina crucible with a lid (99.5%, outer diameter 40 mm, inner diameter 36 mm, height 60 mm, manufactured by KERANOVA AB, Sweden). Chloride salts (8 wt% NaCL, 53 wt% KCL and 39 wt% LiCl) and cullet were placed in a uniformly mixed crucible and held in the oven for a predetermined time. Argon gas (ICP 5.0, AGA gas AB, Sweden) was introduced from the bottom of the furnace as a protective gas. A graphite rod (diameter 6 mm, Lorraine, Paris) was used as an electrode, and an iron rod (diameter 6 mm) was used as a lead wire.

  During the dissolution process, the electrode was held 2-4 cm above the salt melt. After the salt mixture was melted and held for dissolution for a period of time, the electrode was immersed in the salt melt, electrolysis was started, and DC power (HP Hewlett 6632A) was supplied. After electrolysis, the electrode was removed from the salt melt, held above the salt melt, and cooled under the protection of argon gas. The sample in the crucible was completely dissolved in distilled water and filtered. The residue was prepared for chemical analysis. ICP-AES analysis was applied to the elements Al, Fe, Sr, Zr, Sb, Ba, Zn, Pb, Li and Ti. Atomic absorption analysis was applied to the elements Na, Mg, Ca and K. Deposited products on the cathode were analyzed with a scanning electron microscope (SEM) (JSM-840, JEOL) equipped with energy dispersive X-ray spectroscopy (EDS link, Oxford).

  Four factors were examined: retention temperature, retention time, flux content (molar ratio to NaCl-KCl-LiCl mixture), and flux / cullet (weight ratio). The parameters changed during the test were temperature (600, 800, and 1000 ° C.), retention time (4 and 8 hours), flux content (11, 15, 19 and 29 wt%), and flux / cullet ( 0.37, 0.5, 0.7, 0.9 and 1.5) were employed. Table 2 shows the extraction rates of various metal oxides in the CRT glass in the salt melt. In this table, the extraction rate is defined as the ratio of oxide left in the residue to the amount of corresponding oxide in the initial CRT glass.

  Two methods were used to estimate the amount of extracted oxide. First, the dissolved residue was filtered and then subjected to two chemical analyses, ICP-AES and atomic absorption analysis. It should be noted that this extraction rate is not always equal to the solubility in the salt melt. Some of the oxide can evaporate as chloride. The extraction rates of aluminum and lithium oxides show negative values, which means that the amount of oxide increased. Almost all oxides show very high extraction rates except for iron and antimony oxides. However, iron and antimony oxides show an extraction rate of about 70%. For lead oxide, this ratio is about 50-60% at 800 ° C. and 91% at 1000 ° C. These values are lower than those obtained at 600 ° C. Also, the increase in flux content and flux / cullet ratio does not seem to contribute to the increase in lead oxide extraction rate, which is already very high extraction when flux content and flux / cullet are at low ratio This is because the rate is shown. In this experimental test, a flux / cullet ratio of 0.37 appears to be sufficient to dissolve lead oxide in the salt melt. This value is a theoretical amount for completing the reaction (1).

The change of lead oxide extraction rate with different process parameters was investigated. The extraction rate of lead oxide at 600 ° C. was about 96% and did not depend on the holding time. For temperature variations, the extraction rates were about 95, 60 and 91% at 600, 800 and 1000 ° C., respectively. The ratio seems to be random. However, it can be said that the high temperature did not contribute to the increase of the extraction rate. Also, high flux content did not significantly change the extraction rate. Similarly, changes in the flux / cullet ratio did not result in significant changes in lead oxide extraction rate (which was about 95%). Thus, higher temperatures, flux content and flux / CRT ratio, longer retention times are not required. As described above, an increase in parameter value does not result in an increase in extraction rate because a low value of the parameter already gives a high extraction rate. Based on this result, the optimized process parameters were a temperature of 600 ° C., a flux / cullet of 0.37, a holding time of 4 hours, and a flux content of 11% by weight. In the test at 1000 ° C., there was much evaporation of AlCl ₃ . Therefore, it is preferable to maintain a temperature lower than 1000 ° C, preferably lower than 900 ° C.

  The dissolution test demonstrates that valuable metals in CRT glass can be extracted into the salt phase. Different metals or alloys can be deposited on the cathode surface under different cell potentials. All metal chlorides in the melt have a theoretical decomposition voltage. The decomposition voltages of silicon chloride and lead chloride are close to each other, which means that it is expected that it will be difficult to describe these two separated from each other. However, silicon tetrachloride is not actually present in the melt because it is very difficult to dissolve silicon oxide in the salt melt. Therefore, it is possible to deposit lead selectively. It should be noted that even in pure molten salt systems, metal electrodeposition affects many factors such as overvoltage, current density, current efficiency, electrolytic cell conductivity, cathode material properties and surface, distance between electrodes, etc. It can be done.

  For the experimental electrolytic treatment, a temperature of 600 ° C., flux / cullet of 0.9, retention time of 4 hours, and flux content of 19% by weight were selected because of the small size of the crucible. At that time, the amount of CRT glass was 9.3 g, which contained about 1.8 grams of lead oxide. If 100% of the lead oxide is dissolved in the salt melt and all of the lead is deposited, about 1.7 g of lead is recovered. This amount of lead is the maximum value obtained for a small crucible.

  As indicated above, a salt extraction process has been developed to recover lead and other metals from CRT glass. According to analysis of CRT glass, the glass contained about 19% lead oxide and about 96% of the lead oxide was extracted by dissolution in the salt melting process. The optimized process parameters in the dissolution process were (a) temperature 600 ° C., (b) holding time 4 hours, (c) flux / cullet ratio 0.37, and (d) flux content 11% by weight. . Several electrolysis tests were performed using molten salt and CRT glass. A voltage of 2.3 V was used for lead electrodeposition. A liquid phase of lead was deposited and dropped from the cathode into the cathode bag where it was collected.

[Industrial applicability]
A major concern for cathode ray tube (CRT) screen dumping is the leaching of lead from the glass. Lead is used in radiation shielding glass to absorb gamma rays, X-rays, etc., for example, used in CRTs used in computer screens and television sets that are considered to reduce the viewer's exposure to soft X-rays. The Leached lead is dangerous for both humans and the environment. The present invention solves the problem of detoxifying glass from scrapped CRT funnels by recovering lead from the glass. Lead and other metals are present as oxides in the glass and are dissolved in the chloride salt melt and recovered therefrom, for example, by electrolysis. The treated residue consists essentially of Al ₂ O ₃ and SiO ₂ and can be used for landfills, building structures or as a raw material for the refractory industry.

  Similarly, indium can be recovered from glass coated with indium tin oxide.

Claims (23)

A method of recovering lead and / or indium from glass containing PbO and / or indium oxide, mainly from electronic waste materials,
f) crushing the glass to produce cullet;
g) by weight of the mixture,
A chloride salt composition consisting of at least two metal chlorides selected from the group consisting of 60 to 95 alkali metal chlorides and alkaline earth metal chlorides;
- 5 to 30 AlCl _3, and - optionally of 0, halide, additional chloride, to form a mixture of sulfides and / or oxides,
h) heating the mixture to form a salt melt;
i) dissolving the cullet in the salt melt;
j) A method comprising recovering at least one of lead and indium from the salt melt. Said salt composition, NaCl, KCl, at least two salts selected from the group of LiCl and CaCl _2, preferably at least three salt selected NaCl, KCl, from the group of LiCl and CaCl _2, The method of claim 1.   The salt composition is 3 to 20 Na, 30 to 70 KCl, 20 to 60 LiCl, preferably 5 to 15 Na, 40 to 60 KCl, 30 to 50% by weight of the salt composition. The process of claim 1 consisting essentially of LiCl, more preferably 7-12 NaCl, 45-55 KCl, 35-45 LiCl. The salt composition is 10 to 50 NaCl, 2 to 20 KCl, 50 to 80 CaCl ₂ , preferably 25 to 35 NaCl, 3 to 10 KCl, 60 to 75 by weight% of the salt composition. consisting essentially of CaCl _2, the method of claim 1, wherein. The salt composition is 5-20 NaCl, 20-40 LiCl, 40-70 CaCl ₂ , preferably 7-15 NaCl, 25-35 LiCl, 50-60 by weight percent of the salt composition. consisting essentially of CaCl _2, the method of claim 1, wherein. The salt composition is 35 to 65 KCl, 20 to 50 LiCl, 5 to 20 CaCl ₂ , preferably 45 to 55 KCl, 30 to 40 LiCl, 10 to 15% by weight of the salt composition. consisting essentially of CaCl _2, the method of claim 1, wherein. The amount of AlCl ₃ is 5 to 20 wt% of the mixture, preferably in the range of 7 to 15 wt% A method according to any one of claims 1 to 6.   8. A method according to any one of the preceding claims, wherein the salt composition is selected to have a liquidus temperature of less than 700C, preferably less than 600C, more preferably less than 500C.   9. A method according to any one of the preceding claims, wherein the weight ratio of flux to cullet is approximately 0.25 to 1.5, more preferably 0.30 to 1.0.   10. A method according to any one of the preceding claims, further comprising the step of maintaining the temperature for approximately 4-8 hours during the dissolving step. Recovery of at least one of lead and indium from the melt,
The method according to any one of claims 1 to 10, comprising the step of electrolyzing the melt, and the step of selectively electrodepositing at least one of lead and indium.   Maintaining the melt at a temperature of at least 500 ° C. and at most 900 ° C. during cullet melting and melt electrolysis, preferably between 550 and 700 ° C. during cullet melting and melt electrolysis 12. The method of claim 11, further comprising maintaining the melt at a temperature preferably in the range of 580-650 <0> C.   13. A method according to claim 11 or 12, further comprising the step of electrolyzing the melt for approximately 2-8 hours, preferably 3-6 hours.   The method according to claim 11, further comprising collecting chlorine gas generated during electrolysis.   15. The method of any one of claims 1 to 14, further comprising condensing the metal chloride from the melt and condensing the vaporized chloride to later recover the condensed chloride metal. Method.   The method according to any one of claims 1 to 15, further comprising the step of leaching the metal chloride from the melt in water and extracting the metal as a hydroxide by wet refining.   The method according to any one of claims 1 to 16, further comprising the step of recycling the chloride salt of the melt. Al ₂ O ₃ and recovering the treated residues consisting essentially of SiO _2, for landfill or building structure, or further comprising the step of using as a raw material for refractory industry, any one of claims 1 to 17 The method described in 1.   The method according to any one of the preceding claims, wherein the glass comprises PbO and is derived from a funnel and / or neck portion of a computer screen or television set cathode ray tube. A method for recovering lead and / or indium from glass containing PbO and / or indium oxide, mainly from electronic waste materials,
i) crushing the glass to produce cullet;
j) providing a crucible containing a chloride salt melt, at least one cathode and an anode connected to said salt melt, a heating means for heating the salt melt, and an aluminum melt present at the bottom of the crucible. A process wherein the aluminum melt forms an anode or part of an anode;
k) supplying an initiating chlorine donor to the salt melt to initiate the reaction in the salt melt, wherein the initiating chloride donor is electrolyzed in aluminum chloride and / or step g) to produce aluminum chloride. At least one metal chloride that can be formed,
l) maintaining the temperature of the salt melt and the temperature of the aluminum melt at a temperature at which both the salt melt and the aluminum melt are in a liquid phase;
m) introducing the cullet into the liquid salt melt;
n) reacting aluminum chloride as a chlorine donor with cullet to form at least one of lead chloride and indium chloride dissolved in the salt melt;
o) Electrolyzing the salt melt, selectively depositing at least one of lead and indium at the cathode, optionally using a cathode bag, and aluminum chloride on the contact surface of the aluminum melt and the salt melt Forming in situ,
p) A method comprising recovering at least one of lead and indium from the salt melt.   The starting chloride donor comprises aluminum chloride added to the mixture before heating it or added to the salt melt, said aluminum chloride being up to 20% by weight of the chloride salt mixture, preferably 1 to 21. The method of claim 20, wherein 15% by weight, more preferably 5-10% by weight is added.   The method according to claim 20 or 21, wherein the salt melt and the aluminum melt are kept at a temperature above 660 ° C, preferably between 700 ° C and 1000 ° C, more preferably below 900 ° C.   23. A method according to any one of claims 20 to 22, wherein the method is partially or completely self-supporting during steady state by aluminum chloride formed during electrolysis.

Images