Bitmiş Li-iyon ikincil pillerinden lityum ve kobalt geri kazanımı

In recent years, consumer demand for smaller and more powerful electronic devices has led to a large increase in the usage of batteries worldwide. Advances in sophisticated electronic items such as laptop computers and mobile phones require these batteries to be more sustainable, smaller and lightweight. The gravimetric energy density is 110-160 and 30-50 Wh/kg for lithium ion and lead acid batteries respectively. Owing to its merit, such as a high energy density, a high working voltage, a long cyclic life and negligible memory loss effects, the lithium ion batteries are state of the art and also remain the battery system with the highest potential for future development. With increasing use of such batteries in the developed countries for transportable applications, and large untapped markets in the developing countries, the need for lithium ion batteries will increase by orders of magnitude. This has led to growing concerns worldwide about the disposal of batteries and the potentially harmful impact they may have on the environment. However, spent batteries also represent a concentrated source of high value metal. Therefore, it is important that a system for recycling and regenerating waste lithium ion batteries is developed. Owing to the explosive nature of metallic lithium, spent lithium primary batteries cannot be disposed safely unless metallic lithium is properly removed from them. In contrast, lithium ion secondary batteries use a lithium conducting cathode made from a non-explosive 'mixed oxide', allowing a wider selection of recycling techniques. These mixed oxides often contain valuable cobalt, which has a high economic value for recycling owing to the fact that natural sources for cobalt are limited, and its uses are diverse and steadily increasing. The objective of the present work is to outline the dissolution characteristics of the cathodic active materials from spent lithium ion secondary batteries in sulfuric acid media, and to recover cobalt and lithium separately as their sulfates by sulfate precipitation method using ethanol. Despite long leaching time and high leaching temperature, it was observed that cobalt, which is present in the LiCoO2 compound, dissolved into concentric sulfuric acid media with poor dissolution efficiency. The reason for this is that the oxidation level of the cobalt in the LiCoO2 compound is +3, so it should be reduced to +2. Hydrogen peroxide, known as both good oxidizer and reducer, is an ideal option for this reduction. Using 5% H2O2, at 80oC, at 300 rpm, the LiCoO2 compound was found to dissolve into 4M H2SO4 in an hour with 100% dissolution efficiency. Cobalt was recovered in two steps. During the first step, 92% of the cobalt is recovered as CoSO4 by the use of ethanol at a volume ratio of 3:1. Ethanol removes water ligands from the Co2+ cation, and caused the precipitation of cobalt as cobalt sulfate monohydrate. In the second step, the remaining cobalt was precipitated as cobalt hydroxide (Co(OH)2) by increasing the pH value up to 10 with the addition of lithium hydroxide (LiOH). Lithium, which remained in the solution, was then recovered as lithium sulfate (Li2SO4) with up to 98% recovery efficiency by the addition of ethanol at a 3:1 volume ratio. It was shown that metals could be precipitated separately by this technique depending on their concentrations present in the solution. Using this selective precipitating characteristic of ethanol, it was managed to precipitate the cobalt with high efficiency without promoting the precipitation of the lithium. The advantage of this technique over more classical techniques for salt crystallization is that no temperature shift is needed, and the product will be intrinsically low in water, unlike the more classical separation by crystallization, which requires heat (or at least temperature control) and tends to yield a metal sulfate with a high amount of crystalline water. The leach acids may be reused in feedback loops. Also, it is possible to recover ethanol by distillation. By doing so, the recovered ethanol could be reused for precipitating sulfates from sulfuric acid solutions. The proposed process can be used to treat spent Li-ion secondary batteries, and to recover valuable cobalt and lithium without posing environmental problem.  Keywords: Li-ion batteries, recycling, precipitation method with ethanol, Li and Co recovery. Bu çalışmada, lityum iyon ikincil pillerinde katodik aktif malzeme görevi gören lityum kobalt oksit (LiCoO2) bileşiğinin sülfürik asit ile liç davranışları optimize edilerek, çözeltiye geçen lityum ve kobaltın etanol sülfat çöktürme tekniği ile sülfatları şeklinde çöktürülme şartları incelenmiştir. Yeniden kullanılabilir malzemeleri maksimum seviyede geri kazanmak ve böylece bitmiş pillerin çevreye yapacağı kirliliği minimuma indirmek amaçlanmıştır. 80oC sıcaklıkta 1 saat boyunca çözümlendirme işlemi için kullanılan %5 hidrojen peroksit içeren 4M sülfürik asit çözeltisi ile lityum ve kobaltın tamamı çözeltiye geçmiştir. Çözeltiye geçen kobalt iki aşamada geri kazanılmıştır. Birinci adımda, çözeltideki kobalt iyonları, 3:1 etanol/çözelti hacimsel oranında etanol ilavesiyle CoSO4 şeklinde %92 verim ile çöktürülmüştür. Etanol, çözeltideki sülfat ligant bağlarının kırılmasını sağlayarak kobaltın, kobalt sülfat tuzu (CoSO4) şeklinde çökmesini sağlamıştır. İkinci adımda, etanol ile çökmeyen kobalt iyonları, lityum hidroksit ile pH 10’a getirilerek kobalt hidroksit (Co(OH)2) şeklinde çöktürülmüştür. Çözeltideki lityum iyonları da sülfürik asit ile asitlendirildikten sonra 3:1 etanol/çözelti hacimsel oranında etanol ilavesiyle %98 verim ile lityum sülfat (Li2SO4) şeklinde çöktürülmüştür. Etanol sülfat çöktürme tekniği ile metallerin başlangıç konsantrasyonlarına bağlı olarak selektif olarak çöktürüldükleri gösterilmiştir. Ayrıca diğer metotların aksine etanol sülfat çöktürme metodu ile yapılan çöktürme işleminde sıcaklık değişimine ihtiyaç yoktur ve elde edilen ürün düşük miktarda kristal su içermektedir. Anahtar Kelimeler: Li-iyon pilleri, geri dönüşüm, etanol sülfat çöktürme, Li ve Co kazanımı.&nbsp

Leaching of scrap lead acid battery paste by NaOH

Zehirli malzeme olarak sınıflandırılan kurşunu içeren birçok ürün, son yıllarda, kullanım alanını kaybetmektedir. Kurşunun en yaygın kullanım alanını kurşun asit akümülatörleri oluşturmaktadır. Kurşun asit akümülatörlerinin kullanım ve tüketim miktarları, çevreye karşı etkileriyle birlikte göz önüne alındığında, geri kazanımının gerekliliğini ve önemini yansıtmaktadır. Nitekim son yıllarda, Avrupa’da, %95’in üzerinde hurda kurşun asit akümülatörü geri kazanılmaktadır. Geri kazanımda temel aşamalar, sırasıyla; akümülatör asidinin boşaltılması, plastik kısımların ayrılması, metalik kısımların değerlendirilmesi ve akümülatör pastasının geri kazanılması süreçleridir. Hurda kurşun asit akümülatörlerinin geri kazanımında hidrometalurjik ve pirometalurjik yöntemler uygulanmaktadır. Bu yöntemler içerisinde, doğrudan ergitmeye dayanan yöntemlerin, gerek düşük metal kazanma verimi gerekse çevre açısından olumsuz etkileri nedeniyle yeni yöntemlerin geliştirilmesi gerekmektedir. Geri kazanım sürecinde, karmaşık kimyasal yapılı atık akümülatör pastasında bulunan, özellikle, zor çözünen PbO2 ve kükürt içerikli PbSO4 büyük sorun yaratmaktadır. Bu çalışmada, atık kurşun asit akümülatörlerinde bulunan akümülatör pastasının kimyasal ve fiziksel karakterizasyonu yapılmakta, ardından NaOH çözeltileriyle çözümlendirilmesi şartları incelenmektedir. NaOH ile çözümlendirmede en uygun işlem şartları; 400 dev.dak–1 karıştırma hızında, 1/10 katı/sıvı oranı için 0.7 M NaOH başlangıç çözeltisiyle, 15 dakikalık çözümlendirme süresinde ve ortam sıcaklığında sağlanmaktadır. X-ışını difraksiyonu analizi sonuçlarına göre, işlem sonrasında akümülatör pastasındaki PbSO4, kurşun oksi-hidroksit (Pb3O2(OH)2) bileşiğine dönüşmektedir. İşlem sonrasında atık pastada %68.8 oranında bulunan PbSO4, çözümlendirme sonrasında  %0.5 oranında analiz edilmektedir. Anahtar Kelimeler: Geri kazanım, akümülatör pastası, kurşun akümülatörler, NaOH çözümlendirmesi.Many lead based products that are classified as toxic material have disappeared from use in recent years. Lead acid batteries constitute the most widespread usage area of lead. Lead is particularly suitable for batteries, because of its characteristics (conductivity, resistance to corrosion and the special reversible reaction between lead oxide and sulphuric acid). The majority of lead / acid batteries are used as SLI batteries (starting, lightning and ignition) for the purpose of starting the engines of cars and lorries. Another sort of lead acid battery is the traction battery, used to power electric vehicles such as milk floats, forklift trucks and airport support vehicles. This type of battery provides the best service for "stop and start" conditions. A last sort of lead acid battery concerns stationary battery, which provides uninterrupted electrical power (e.g. in hospitals, telephone exchanges, companies etc.) The active mass, cathode, anode, connecting bridges, electrolyte, and casing are the main components of lead acid battery. The cathode (positive pole) consists of metallic lead, whereas anode (negative pole) consists of lead oxides. Connecting bridges are made of suitable lead-antimony, lead-calcium (tin, aluminium) alloys with additives in negligible quantities, such as copper, arsenic, tin and selenium. Sulphuric acid solution is used as an electrolyte in which lead-antimony plates are immersed. Casing is usually made of polypropylene, and, less frequently, of hard rubber, ebonite, bakelite etc. Other components of lead acid batteries are paper, rubber, fibre-glass and wood. When a battery discharges, as it operates the starting motor of a car, the concentration of sulphuric acid decreases from the electrolyte and the lead from the electrodes is transformed into lead sulphate. As the concentration of the acid decreases, the density of the electrolyte also decreases, thus making it possible to know the level of charge of a battery by measuring the density of its solution. For each electron generated in an oxidation reaction occurring at the negative electrode, there is an electron consumed in the reaction of the reduction of the positive electrode. As the process continues, the active materials (the lead oxides paste and the porous lead) are depleted and the speed of the reaction decreases until the battery is no longer able to supply electrons. Most of the lead oxides paste and the porous lead are converted into lead sulphate. When a battery is recharged, these reactions are inverted and the lead sulphate changes back into lead and lead oxide. In time, the lead oxide plates become contaminated by lead sulphate form sludge layer (55-60% PbSO4; 20-25% PbO; 1-5% PbO2; 1-5% metallic Pb). This mixture accumulates at the bottom of the battery. It is no longer possible for battery to recharge due to the high level of contamination. From this moment the battery becomes what is known to be a spent battery. The usage amount and the consumption of lead acid batteries, considering the environmentally non-friendly effects, reflect the necessity and the importance of recycling. Likewise, in recent years more than 95% of scrap lead acid batteries have been recycled in Europe. Basic stages in lead acid battery recycling processes are removal of the battery acid, separation of the plastic parts, processing of metallic parts, recycling of battery paste, respectively. Hydrometallurgical and pyrometallurgical methods are used in scrap lead acid battery recycling. During recycling process, particularly, because of non-soluble PbO2 and sulphur containing PbSO4, significant problems occur. The presence of lead sulphate complicates the environmentally acceptable treatment of the battery paste. The high temperatures required to decompose the sulphate generate lead fumes in addition to dilute SO2 gas streams. PbO2 can only be dissolved by using additional chemicals in hidro-electrometallurgical recycling processes. In this study, lead acid batteries were defined, and some existing pyrometallurgical and hydro-electrometallurgical scrap lead acid battery treatment processes were comparatively investigated. The purpose of this study is to investigate the possibility for desulphurization of the paste with sodium hydroxide to verify the possibility for removal of sulphur ions in the form of sodium sulphate. Optimum process conditions for NaOH leaching of battery paste are achieved as follows; 400 rpm of stirring rate, 1/10 of solid/liquid ratio for 0.7 M NaOH starting solution, 15 minutes of leaching duration at room temperature. X-ray diffraction analysis show the transformation of PbSO4 in the battery paste into lead oxi-hydroxide (Pb3O2(OH)2) compound.Keywords: Recycling, battery paste, lead batteries, NaOH leaching