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.

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, fibreglass 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 nonfriendly 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 hidroelectrometallurgical recycling processes. In this study, lead acid batteries were defined, and some existing pyrometallurgical and hydroelectrometallurgical 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.