Pyrometallurgical Recovery Of Metals From Electronic Waste Environmental Sciences Essay

Published: 2021-07-01 07:38:21
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Category: Metal, Chemistry, Water, Manufacturing, Recycling, Electronic Waste

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Veldbuizen and Sipple ( 1994 ) acknowledged that stuffs come ining into the reactor are immersed in a liquefied metal bath where the temperature is around 1250 grades, which is churned by a mixture of supercharged air. The burning of plastics and other inflammable components in the eating procedure cut down the cost of energy. In the reactor, all drosss including Fe, Zn and lead are converted into oxides and so converted into scorias to silica by the agitated oxidization zone. These scorias are cooled and milled to acquire more and more metals before the disposal ( Cui & A ; Zhang, 2008 ) .
The diagrammatic word picture of the works and the recycling procedure of E-waste are given below. These two diagrams will explicate how cast-off waste of Personal computers and laptops are recycled and disposed off. The Cu matte incorporating cherished metals is removed and transferred to the convertors. After the patterned advance in the convertors, liquid blister Cu is refined in anode furnaces and dramatis personae into anodes with about absolute pureness of 99.10 per centum. The residuary 0.9 per centum holds the valuable metals such as gold, Ag, Pt and Pd. There are besides some other recoverable stuffs like Ni, Se, Te etc. Afterwards, electro-refining of the anodes recovers these marketable metals ( Cui & A ; Zhang, 2008 ) .
Fig-9 shows that E-waste can be fed into the procedure in different stairss depending upon their purenesss. High Cu incorporating bit is fed into change overing procedure straight but low class E-waste is fed into Kaldo Furnace. The needful O is supplied by the O spear for the intent of burning along with oil O burner. The off-gases require an extra burning air of about 1200 grades after burning. Thermal energy is recovered by a steam web through criterion gas handling system.

Figure: - 8 Pyrometallurgical Recover Process at Recycling Plant
( Beginning: Cui & A ; Zhang, 2008 )
Figure: - 9 Recovery of Cherished Materials
( Beginning: Cui & A ; bent, 2008 )
The installing of off-gas emanation control system in an IsaSmelt Furnace ( a new method of E-waste recycling and metal recovery ) is an illustration for retrieving thermic energy by a steam web through criterion gas handling system. Here the hygienic gases and procedure gases are cooled to retrieve the energy and are cleaned utilizing techniques like bag house filters, electro filters etc.
2.12.3 Recovery of Cherished Metallic elements Using IsaSmelt Furnace:
The smelting ( the procedure of runing to retrieve metal from its ore ) procedure in the recycling of E-waste is done in IsaSmelt Furnace ( Cui & A ; Zhang, 2008 ) . Like Pyrometallurgical Process one of the most of import advantages of utilizing this method is that the demand for energy beginning and cut downing agent for the smelting procedure will be quarterly substituted by the combustion of the organic substances like plastics that are present in the E-waste ( Hageluken, 2007 ) . The smelting procedure offprints cherished metals in Cu bullion from other metals that are present in a lead scoria, which is further treated in a BMO. The cured Cu bullion is used in the following procedure of valuable metals recovery through copper-leaching ( a method used for the recovery of Cu from its ore ) and electro-winning ( method of taking drosss from the metals ) procedures.
There are three nucleus processing stairss in the BMO:
The Lead Blast Furnace: to diminish the oxidized lead scoria from the IsaSmelt together with high lead incorporating 3rd party natural stuffs.
The Lead Refinery: the assorted lead bullion, roll uping most of the non-precious metals is farther treated here and the procedure is called Harris procedure.
Particular Metallic elements Plant: pure metals are recovered in this works.
( Cui & A ; Zhang, 2008 )
The image of the emanation control system is as under and could be adapted by the recycling centres to cut down the degree of emanation. Hageluken ( 2007 ) , in his study accepted that the emanations from the works are much below the bounds set by the European bureaus and authorities.
Figure: - 10 IsaSmelt Furnace Fitted With Emission Control System
( Beginning: Cui & A ; Zhang, 2008 )
Apart from recycling methods like Pyrometallurgical Process and method utilizing IsaSmelt Furnace, bio-metallurgical procedure is another method of retrieving cherished metals from E-waste. Due to moo cost and high specificity for the mark elements, bio-metallurgical processing is attractive and soon limited to merely rich states ( Cui & A ; Zhang, 2008 ) . Brand et Al, ( 2001 ) displayed how Fungi ( Aspergillus Niger, Penicillium Simplicissmum ) and Thiobacillus bacteriums can enable metal filtrating from electronic bit. To retrieve gold, Cu etc from E-waste, Creamer et Al ( 2006 ) engaged Desulfovibrio Desulfuricans.
2.13 Batteries: Recycling & A ; Material Recovery:
Batteries are one of the terminal merchandises of E-waste recycling because it remains integral during the E-waste recycling procedure ( SWEEEP, 2010 ) . Land make fulling or Incineration of these batteries can do terrible wellness and environmental jeopardies ; when the shell of these land filled battery corrodes it can ensue in air, dirt and H2O pollution because it contains toxic substances like lead, quicksilver, Cd ( human carcinogen: substance that causes malignant neoplastic disease ) etc ( Frick & A ; Knudsen, 2002 ) . Similarly incineration of batteries will ensue in air pollution and other wellness jeopardies.
On the other manus proper intervention and recycling of these batteries will be good both for the environment and for the economic system because it contains valuable stuffs like steel, Ag, nickel, Zn, manganese, gypsum etc which can be recovered and the harmful substances like lead, Cd, quicksilver can be safely separated and can be reused as secondary natural stuff ( G & A ; P, 2010 ) .
UK generates 20,000 to 30,000 metric tons of waste batteries every twelvemonth and out of it less than 1,000 metric tons are recycled ( Resource Management & A ; Recovery, 2003 ) . Harmonizing to waste battery ordinances in Europe ( European Batteries Directive, 2006/ 66/EC ) , UK is needed to recycle 10 % of portable batteries in 2010, but in UK, merely 3 % of portable batteries are presently being recycled.
2.13.1 Methods of Battery Recycling:
Harmonizing to Espinosa, Bernardes & A ; Tenorio ( 2004 ) , it is imperative to cognize the composing of batteries in order to advance its recycling because the chemical composings of different batteries are different, so same methods can non be used for recycling different batteries. But unluckily there is no relationship between the size or form of batteries and their composing. There are chiefly three methods for the recycling of batteries:
Separation of constituents through unity operations of excavation intervention
Out of these three methods the most normally used method by all the recycling companies in UK and Europe are Pyrometallurgy and / or Robust Pyroprocess ( another method ) severally because of their simpleness and high efficiency / capacity ( even though the energy demands for these procedures are high ) ( Jan Tytgat, 2010 ) . The Pyrometallurgy and Robust Pyroprocess methods of recycling will be discussed in item in chapter four.
2.13.1 Hydrometallurgy Method of Battery Recycling:
In the past two decennaries, the most active research country on recovery of metals from battery is retrieving cherished metals by Hydrometallurgical procedure ( Horn & A ; Holt, 1990 ) . In this method the unsorted batteries are fed straight to the furnace. Inside the furnace the organic constituents will acquire decomposed to organize bluess ( Sequeira, 1994 ) . For illustration quicksilver compound will acquire decomposed to organize quicksilver vapor. These bluess are so passed through a capacitor to retrieve quicksilver and other condensable liquids.
The condensate will acquire fractionated by the centrifugation procedure into quicksilver, waste H2O etc. The waste H2O will so passed through an aluminum cementor to retrieve the residuary quicksilver in the signifier of an aluminium-mercury metal. The staying waste from the cementor is send to an evaporator to bring forth some steam or H2O and a salt mixture ( disposable ) in order to forestall the inordinate salt construct up in the procedure. The residuary gases and other organic bluess are oxidized in an afterburner and expelled to the ambiance in the signifier of H2O vapor and C dioxide after a careful intervention to take the staying sum of quicksilver since this quicksilver may incorporate hints of risky substance like Cd ( Sequeira, 1994 ) .
The staying solids from the furnace are shredded and leached ( acid or acerb leaches ) before the magnetic separation of Fe and Ni from other non magnetic solids. The leaching solutions which contain oxides of C, Zn, manganese etc are so subjected to separation and purification processs such as precipitation of drosss, solvent extraction, ion-exchange etc. Consequently, the solutions are treated by electro refinement procedure for metal recovery ( Sequeira, 1994 ) . It is estimated that for retrieving a metric ton of Cu this procedure requires around 3,400KWh of energy ( Liew, 2008 ) .
Precipitation of drosss is nil but the drosss present in the solution will go a precipitate ( solid ) during the chemical reaction, which can be removed subsequently by filtrating. Thus the staying liquid ( supernate ) above the solid containing cherished metals can be separated and cherished metals can be recovered by electro refinement. Electro refinement is a method of sublimating metal by electrolysis. Here the impure metal and cathode will be immersed in a solution ( electrolyte ) incorporating cations and electric current will be passed between the impure metal and cathode. As a consequence of it the pure metal will acquire deposited on the cathode and can be separated.
Solvent Extraction is the procedure of dividing liquid mixtures by doing usage of solubility differences of the different constituents ( Cox & A ; Rydberg, 2004 ) . Ion-Exchange is an electrochemical procedure in which an unwanted chemical constituent is removed from solution by replacing it with a more attractive one ( Friedrich, 1995 ) .
The chief terminal merchandises of this procedure are C and black lead which can be removed subsequently by filtration. Compared to Pyrometallurgical procedure Hydrometallurgy is more exact and predictable but its operating cost is high and it is more complicated ( Sequeira, 1994 ) . This method is chiefly used for the recycling of lithium-ion, nickel Cd, Zn oxide and quicksilver oxide batteries.
Figure: -11 Hydrometallurgy Method of Battery Recycling
( Beginning: Sequeira, 1994 )
2.13.2 Separation of Components through Unity Operations of Mining Treatment:
Separation of constituents through unity operations of excavation intervention method is besides used for battery recycling ( e.g. nickel Cd batteries ) . Using this method more than 2kg of Ni home bases present in a nickel Cd battery can be recovered. A compound with a high sum of Cd can besides be obtained and can be farther treated ( cadmium distillment ) to retrieve the stuff. This method is non used often because of its high operating cost and complexness ( Espinosa, Bernardes & A ; Tenorio, 2004 ) .
2.13.3 Recycling Procedures under Pyrometallurgy & A ; Hydrometallurgy:
There are several battery recycling procedures that works by the Pyrometallurgy and Hydrometallurgy rules. Sometimes these procedures are designed for specific sort of battery, but there are some in which batteries can be recycled together with other types of stuffs. The procedures are as follows:
Sumitomo: It is a Nipponese procedure which is wholly based on calcinations ( method of change overing metals to its oxide at high temperature ) at about 1000 grade centigrade in a furnace ( Tedjar et al, 2010 ) . Its cost is really high and it is used to recycle all types of portable batteries e.g. lithium-ion battery. The residues formed as a consequence of calcinations is crushed and screened. The residuary pulverization will incorporate oxides of different metals. It is non suited for recycling nickel Cd batteries.
Figure: -12 Sumitomo Method of Battery Recycling
( Beginning: Sequeira, 1994 )
Recytec: It is the Swiss procedure that combines pyrolysis ( thermic intervention ) , gas intervention, tear uping, rinsing, electrolysis ( for non-ferrous substances ) followed by magnetic separation and other physical interventions ( Sequeira, 1994 ) . It is used for recycling all types of portable batteries and besides fluorescent lamps and quicksilver incorporating tubings.
Initially pyrolysis is done at 550 grade centigrade in a reduction atmosphere and the waste gases produced during this procedure are passed through a capacitor for purification. The solids that left after the pyrolysis are shredded and washed with H2O to call up different salts and oxides. The oxides of manganese and zinc get dissolved in an acidic leaching process and these are at the same time separated by an electrodeposition procedure. Ferro-magnetic stuffs are separated by magnetic separation procedure from other non magnetic substances like black lead. The stuffs separated by the magnetic separation procedure so enter into an electrochemical system and from here the stuffs are separated by anodal disintegration method. The method of anodal disintegration offers 99 % pureness of the metals recovered.
Figure: -13 Recytec Method of Battery Recycling
( Beginning: Sequeira, 1994 )
This procedure does non recycle nickel Cd batteries. The initial investing for this procedure is smaller than that for the Sumitomo procedure, but its operating cost is high ( Espinosa, Bernardes & A ; Tenorio, 2004 ) . Another advantage of this procedure compared to Sumitomo is its first-class recycling efficiency of 95 % i.e. merely 5 % of secondary waste.
TNO: It is a Hydrometallurgical Dutch procedure for the recycling of bit batteries. This procedure developed two recycling options one for alkaline family batteries and the other for nickel Cd batteries. The option for family batteries was non commercially implemented ( Espinosa, Bernardes & A ; Tenorio, 2004 ) .
In this procedure the waste batteries are foremost shredded into little ( all right ) fractions. Many metal and plastic parts can be retained from these all right fractions. These all right fractions are so subdivided into two fractions: magnetic and nonmagnetic. Then both these fractions will be leached with hydrochloric acid to fade out the Cd content in it. The magnetic atoms like Fe and Ni will be separated by magnetic separation procedure after the leaching procedure.
These separated Fe and nickel atoms will incorporate Cd and this Cd can be removed by extraction procedure with the aid of TBP. The Cd salt from the infusion will be farther removed by acerb extraction. The sourness of the so formed Cd chloride is so adjusted to precipitate residuary Fe as ferrous hydrated oxide and it is separated by the filtration procedure. By utilizing the electrolysis procedure metallic Cd will be recovered and the staying solution is discarded ( Sequeira, 1994 ) .
Accurec: It is a German Pyrometallurgical procedure to recycle batteries chiefly used for nickel Cd batteries. This procedure has got several advantages like: it is merely a one measure procedure compared to other procedures, the emanation of green house gases to the ambiance is less ( & gt ; 0.01g/h ) , it is energy efficient and a extremely secured procedure ( Accurec, 2010 ) .
Figure: -14 Accurec Method of Battery Recycling
( Beginning: Accurec, 2010 )
Snam-Savam: Gallic procedure for Ni Cd battery recycling, wholly based on Pyrometallurgy method ( Espinosa, Bernardes & A ; Tenorio, 2004 ) . This is a closed furnace battery recycling technique in which Cd is distilled at 850-900 grade centigrade. This method offers 99.9 % pureness of the cured stuffs ( Sequeira & A ; Moffat, 1997 ) .
Sab Nife: Swedish procedure for Ni Cd batteries. This method is besides based on Pyrometallurgy. In this method the Cd is distilled at high temperature ( 850-900 grade centigrade ) in a reduction atmosphere. Then the Cd is chemically leached with the aid of sulfuric acid and eventually Cd is recovered from the leachate by electrolysis ( Sequeira & A ; Moffat, 1997 ) .
Atech: This procedure is based on the physical intervention of cast-off batteries ; it is holding relatively lower cost than the other types of recycling procedures but the pureness of the cured stuffs will non be high. It is used for recycling all types of portable batteries.
Recycling Companies does non trust on any individual method or procedure but it uses the combinations of many methods and procedures for the recycling of assorted types of batteries, as it is apparent that there are many types of batteries holding different forms, size and chemical composing. So, the company uses the method and procedure which are suited for the peculiar set of batteries.
Table aa‚¬ '' 11: Valuable Materials that can be recovered by Battery Recycling:
Name of the Battery
Materials that can be Recovered
Lead Acid
Lead, Polypropylene, Gypsum
Zincs Based
Steel, Zinc, Manganese
Nickel Cadmium
Nickel, Steel, Cadmium
Cobalt, Steel
Silver Oxide
Silver, Steel
Mercuric Oxide
Mercury, Steel
( Beginning: G & A ; P, 2010 )
These recovered metals and stuffs has got many applications like: lead and Cd can be used for doing batteries once more, steel and Ni can be used in the steel industry, polypropene can be used for doing battery instances, gypsum can be used for agricultural intents, Co and Ag can be used in electronic and photographic industries etc.
Overall E-waste is really insecure for the environment and for the human wellness. On the other manus if proper recycling Centres are established, the economic system as a whole would be benefited and there would be fewer loads on natural resources like gold, Cu, aluminum, Ag and other cherished metals and stuffs. In this manner the reuse rate would be increased and less emanation of green house gases would happen. It would be good for the environment, human wellness and national economic system of the UK to set up proper and dedicated recycling Centres to better the status. UK particularly needs it, as it has the highest figure of computing machine users. As per estimated information there are at present 360 million computing machine users in UK ( Internet World Statistics, 2009 ) . One can easy do appraisal of the volume of E-waste, maintaining in head the maximal life of computing machines and replacing in UK.
2.14 Decision:
From the reappraisal of the available literature, it can be argued that E-waste is earnestly really unsafe for the environment and for the human wellness every bit good. The whole universe needs to take proper enterprise for managing E-waste and there should be dedicated recycling Centre for it. Although, there are enterprises that have been taken but those are non plenty as the measure of E-waste is turning twenty-four hours by twenty-four hours. The authoritiess across Europe and the authorities of UK have enacted Torahs and directives for extenuating the ill-impact of E-waste. After the earth acme in 1992, two ordinances have been enforced to extenuate the ill-effect of E-waste i.e. the Swiss ORDE ordinance and EU WEEE ordinance. Under both the ordinances, the list of electronic points is by and big same and contains about the same list.
The turning market for Personal computers and its incursion and replacing markets in developed states like UK and high obsolescence rate have made WEEE as one of the fastest turning waste watercourses. Puckett & A ; Smith ( 2002 ) approximately estimate the chemical and non-chemical substance nowadays in E-waste and it is truly really flooring as the measure projected could be highly harmful for the environment and human wellness. Precisely, it could be wellness jeopardy as the chemicals present in E-waste are lead, Cd, quicksilver, plastics etc ( Culver, 2005 ) . If these chemical substances and metals are burned, it will hold terrible impact on the environment and on the human wellness.
Widmer et Al, ( 2005 ) say that these E-waste contains extremely toxic chemicals and the paradox is that the UK and EU is bound to dispose E-waste within their ain geographical country as they are obliged to follow the directives because the directives of the Basel Norms prohibits them to merchandise with Non-OECD states.
The UK authorities is really serious for the environmental protection and it explores what actions might be taken and poses inquiries, on which remarks and suggestions are invited from a scope of participants including the general populace. Phillips et Al ( 1998 ) argues that there is an pressing demand for the effectual protection of the environment and prudent usage of natural resources, so that the sustainable development programme could non be hampered. The direction of E-waste is acknowledged as indispensable to the sustainable development in UK.
Earlier, the E-waste has used to be disposed through land fill and incineration. Landfill is / was non an effectual manner to dispose E-waste as it is non bio-degradable and used to harm the birthrate of the land. Incineration is besides really unsafe as it can breathe a batch of harmful gases and substances. Spalvins et Al ( 2008 ) and Dagan et Al ( 2007 ) argued against the disposal of E-waste along with MSW as the toxic features could non be mitigated through landfill and could dispute regulative conformity.
To get the better of this serious menace authorities has introduced the construct of EPR both lawfully and operationally. It involves dealing cost, aggregation cost, recycling cost and other types of costs. The makers besides have to negociate with recycling Centres and to place the aggregation centres so that E-waste could be collected expeditiously and economically. The makers are now bound to do such electronic merchandises so that at least 70 % to 80 % ( by weight ) of the stuffs could be collected from recycling and the reuse rate of stuffs must non less than 50 % by weight so that natural resources could be protected.
There are presently assorted theoretical accounts have been adopted for the direction of E-waste. Among that the four stage theoretical account is really effectual. Another extension of the EPR is the ARF. It is collected at the clip of purchase of electrical equipments and besides from the terminal users, so that the recycling procedure could be financed once the merchandise is discarded by the terminal users.
The cast-off E-waste particularly the personal computing machines bits are valuable in the sense that it carries metals about 70 % of the weight of computing machines and are reclaimable. This is the major drive force behind the recycling of E-waste as every company want to understate the input cost and maximize the profitableness. Earlier Pyrometallurgy is used for the recovery of valuables metals from the bit E-waste. However there are some failings in this method. It was non really friendly for the environment as there is more emanation of green house gases. Cui & A ; Zhang ( 2008 ) argue that the retrieval of energy from E-waste pave the manner for utilizing plastics in E-waste. Now it has been apparent that thermic processing of E-waste delivers an attack for recovery of energy from E-waste if a broad runing emanation control system is installed.
The batteries that are the terminal merchandises of E-waste recycling can be farther recycled to retrieve and divide cherished stuffs like steel, Ag, nickel etc and toxic substances like lead, Cd etc severally. The recovery and separation of these metals and stuffs will farther lend to the economic system of the state and sustainability of the environment. There are several methods and procedures for battery recycling and no same method or procedures can be used for different batteries since they differ in their chemical composing. The procedure of Pyrometallurgy and Robust Pyroprocess are sooner used by the recycling companies in Europe.
From the available literature it can be argued that most of the above mentioned recycling procedure / methods offer about 90 % to 95 % pureness of the cured metals and stuffs which is an advantage. On the other manus these methods have got many disadvantages. Most of these procedures / methods that works under the rule of Hydrometallurgy are complicated as it needs to undergo many other sub-processes in between ( except few procedures like Accurec ) , e.g. it needs to undergo tear uping procedure before the existent recycling. Hydrometallurgy procedures are most of the clip dedicated to merely a peculiar type of battery chemical science / little scope of different chemical sciences ( Jan Tytgat, 2010 ) .
Higher energy demand is another disadvantage of these methods ( chiefly for procedures that works under Pyrometallurgy rule ) . For illustration most the methods required energy of about 1000 degree centigrade or more. As consequence of it the operating cost is high. Discarding the terminal merchandise which contains valuable metals ( which can still be recovered ) is another disadvantage. Discarding of the staying solution after the electrolysis of Cd in the TNO procedure is an illustration for this. As mentioned above the loss of staying 5 % to 10 % pureness of cured stuffs is besides an of import affair that needs to be considered

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