Etilendiamin tetraasetik asit kullanılarak atık lityum iyon pillerden metallerin geri kazanımı
Recovery of metals from waste lithium-ion batteries using ethylene diamine tetraacetic acid
- Tez No: 997505
- Danışmanlar: PROF. DR. İSMAİL AYHAN ŞENGİL
- Tez Türü: Doktora
- Konular: Çevre Mühendisliği, Environmental Engineering
- Anahtar Kelimeler: Belirtilmemiş.
- Yıl: 2026
- Dil: Türkçe
- Üniversite: Sakarya Üniversitesi
- Enstitü: Fen Bilimleri Enstitüsü
- Ana Bilim Dalı: Çevre Mühendisliği Ana Bilim Dalı
- Bilim Dalı: Belirtilmemiş.
- Sayfa Sayısı: Belirtilmemiş.
Özet
Bu tez çalışmasında, kullanım ömrünü tamamlamış lityum-iyon pillerden (LIP) lityum (Li), kobalt (Co) ve nikelin (Ni) geri kazanımında daha düşük kimyasal tüketimi gerektiren, maliyet açısından daha avantajlı ve çevre dostu hidrometalurjik liç yöntemlerinin geliştirilmesi amaçlanmıştır. Çalışmada liç maddesi olarak etilendiamin teteraasetik asit (EDTANa₂), sitrik asit (SA), asetik asit (AA) ile bunların ikili karışımları değerlendirilmiştir. EDTANa₂ ve EDTANa₂+SA sistemlerinin kullanıldığı deneylerde, 180 dakika reaksiyon süresi, 100 °C sıcaklık, 20 g/L katı–sıvı oranı ve %1 H₂O₂ (w/w) koşullarında Li ve Co çözünme verimlerinin %99'un üzerine çıktığı belirlenmiştir. Aynı deneysel koşullarda tek başına CA kullanıldığında Co için %93, Li için %96 geri kazanım sağlanmıştır. Tüm liç ajanlarında Ni çözünürlüğünün yaklaşık %90 civarında gerçekleştiği gözlenmiştir. EDTANa₂+AA karışımı ile yürütülen çalışmalarda ise, optimum koşullar altında (180 dakika, 100 °C, 20 g/L, %10 H₂O₂) Li ve Co geri kazanım oranları %99'un üzerinde ölçülmüştür. Liç prosesine ilişkin kinetik analizler, reaksiyon hızının kimyasal reaksiyon kontrollü olmadığını, süreçte belirleyici adımın gözenekli (pöröz) tabaka içi difüzyon olduğunu göstermiştir. Bu bulgu, aktif malzeme yapısının çözünme davranışı üzerinde önemli bir sınırlayıcı etkiye sahip olduğunu, metal iyonlarının difüzyonuna bağlı olarak liç hızının belirlendiğini ortaya koymaktadır. Lİ ve Co geri kazanımı için en düşük maliyetli liç ajanı EDTANa₂+SA ve Ni geri kazanımı için EDTANa₂+AA karışımıdır. Bu karışımlar ile literatürdeki diğer organik asit liç ajanlarına göre %85-95 daha düşük bir maliyetle ve %65-85 daha az madde kullanımı ile geri kazanım yapılabilmektedir. Elde edilen tüm sonuçlar, EDTANa₂ ve karışımlarının hem yüksek geri kazanım verimi hem de düşük maliyet avantajı ile kullanım ömrünü tamamlamış LIP'lerin sürdürülebilir geri dönüşümünde etkin ve uygulanabilir, çevre dostu liç reaktifleri olduğunu ortaya koymaktadır. Elde edilen tüm sonuçlar, EDTANa2+CA karışımının, daha az madde, daha düşük maliyet ve yüksek verimlilik gerektiren bir prosesle, kullanılmış LİP'lerin geri dönüşümünde çevre dostu bir sızıntı suyu olarak kullanılabileceğini göstermektedir. Bu bağlamda, geliştirilen liç sistemlerinin endüstriyel ölçekte uygulanabilirliği, prosesin ölçek büyütme potansiyeli ve çevresel etkileri açısından önemli avantajlar sunduğu değerlendirilmektedir. Özellikle düşük kimyasal tüketimi ve yüksek metal geri kazanım oranları, bu yöntemin hem ekonomik hem de çevresel sürdürülebilirlik hedefleriyle uyumlu olduğunu ortaya koymaktadır. Ayrıca, EDTANa₂ temelli liç sistemlerinin seçici çözündürme kapasitesi, sonraki saflaştırma ve metal geri kazanım adımlarının daha verimli yürütülmesine olanak sağlayarak proses bütününde enerji ve maliyet tasarrufu sağlamaktadır. Bu yönüyle çalışma, atık lityum-iyon pillerin geri dönüşümüne yönelik çevre dostu hidrometalurjik yaklaşımlara bilimsel ve uygulamaya dönük önemli katkılar sunmaktadır.
Özet (Çeviri)
In this thesis, the development of environmentally benign, chemically efficient, and industrially applicable hydrometallurgical processes for the recovery of lithium (Li), cobalt (Co), and nickel (Ni) from spent lithium-ion batteries (LIBs) was investigated. To achieve this objective, ethylenediaminetetraacetic acid disodium salt (EDTANa₂), citric acid (CA), acetic acid (AA), and their binary mixtures were systematically evaluated as leaching agents. The primary aim was to enhance selective metal dissolution while minimizing total chemical consumption, thereby establishing a sustainable and economically viable recycling strategy. Leaching experiments conducted using EDTANa₂ and EDTANa₂+CA systems under optimized conditions—180 minutes of reaction time, a temperature of 100 °C, a solid-to-liquid ratio of 20 g/L, and 1% (w/w) H₂O₂—resulted in lithium and cobalt dissolution efficiencies exceeding 99%. Under identical experimental conditions, the use of CA alone yielded comparatively lower recoveries, with 93% for Co and 96% for Li. Nickel recovery was observed to remain around 90% for all investigated leaching agents. In experiments employing the EDTANa₂+AA mixture, Li and Co recoveries above 99% were achieved under optimized conditions involving a higher oxidant concentration of 10% H₂O₂ (w/w). These results clearly demonstrate the synergistic effect between EDTANa₂ and organic acids in enhancing metal extraction efficiency. Thermogravimetric analysis (TGA) and chemical characterization of the spent LIB powder revealed that the sample consisted of 4.48% moisture, 31.04% organic matter, and 64.48% metal oxides. To remove organic components, the waste LIB powder was subjected to calcination at 700 °C prior to leaching. The calcined powder contained 17.75% Co, 2.38% Ni, and 3.95% Li, and a particle size of 0.053 mm was used in all leaching experiments to ensure consistent mass transfer conditions. The EDTANa₂+CA and EDTANa₂+AA systems represent innovative leaching approaches that combine the acidic dissolution capability of organic acids with the strong chelating power of EDTANa₂. In these systems, CA and AA provide an acidic environment that facilitates the dissolution of metal oxides, while EDTANa₂ forms highly stable complexes with the liberated metal ions, thereby enhancing solubility and preventing re-precipitation. This synergistic mechanism enables high extraction efficiencies at lower reagent dosages and under relatively mild operating conditions, contributing significantly to process sustainability and cost-effectiveness. Experimental findings confirmed that EDTANa₂, both alone and in combination with CA or AA, exhibited superior leaching performance for Li and Co compared to single-acid systems. At 100 °C, 180 minutes, and a solid-to-liquid ratio of 20 g/L, the EDTANa₂, EDTANa₂+CA, and EDTANa₂+AA systems consistently achieved Li and Co recoveries above 99%. In contrast, the use of CA or AA alone resulted in noticeably lower extraction efficiencies, underscoring the critical role of EDTANa₂'s strong complexation ability in controlling leaching performance. Furthermore, the substantial reduction in reagent consumption observed in EDTANa₂-based systems led to a significant decrease in chemical costs, highlighting the economic advantage of the proposed approach. In studies involving acetic acid, the EDTANa₂+AA mixture yielded particularly notable results under high H₂O₂ concentrations. Achieving Li and Co recoveries of approximately 99% using a low-cost and widely available organic acid such as AA demonstrates that this combination constitutes a highly efficient and economically attractive leaching system. Nevertheless, when comparing all leaching agents, nickel consistently exhibited lower dissolution efficiency than Li and Co, remaining at approximately 90%. This behavior is attributed to the structural characteristics of Ni within the cathode matrix and its stronger bonding within layered oxide structures, which impose greater resistance to dissolution. Scanning electron microscopy (SEM) analyses revealed pronounced morphological changes following leaching. The post-leaching residues exhibited looser, more porous, and fragmented structures, indicating effective metal dissolution. Across all leaching agents, surface morphology became smoother after leaching, with minimal changes in primary particle size, although localized agglomeration was observed in some regions. Energy-dispersive X-ray spectroscopy (EDX) analyses confirmed a substantial increase in carbon content and a near-complete depletion of metallic elements in the leached residues. These findings demonstrate that the employed leaching agents effectively complexed and removed metallic species, leaving behind carbon-rich residues primarily originating from graphite anodes or conductive carbon additives. X-ray diffraction (XRD) analyses further supported these observations. Prior to leaching, the spent LIB powder exhibited characteristic peaks corresponding to graphite (C), LiCoO₂, LiNiₓCoᵧMn_zO₂, and minor amounts of Co₃O₄. After leaching, a marked reduction in the intensity of LiCoO₂ and LiNiₓCoᵧMn_zO₂ peaks was observed for all leaching agents, confirming the effective dissolution of metal-containing phases while graphite remained largely unaffected. This selectivity highlights the suitability of EDTANa₂-based systems for targeted metal recovery without excessive degradation of carbonaceous materials. Kinetic analyses indicated that the leaching process was not governed by surface chemical reaction control. Instead, diffusion through the porous product layer was identified as the dominant rate-controlling mechanism. This finding suggests that the internal structure of the cathode material imposes significant diffusional resistance during leaching, emphasizing the importance of particle size and surface area in determining leaching efficiency. The use of EDTANa₂ and its combinations with CA and AA resulted in lower apparent activation energies, further confirming that ion transport rather than chemical reaction kinetics limits the overall process. By facilitating ion mobility through complex formation, EDTANa₂-based systems effectively enhance leaching rates. Metal recovery from the leach solutions was achieved through selective precipitation. Co²⁺ and Ni²⁺ ions were precipitated as CoS(s) and NiS(s) using Na₂S. At pH 3, the Co²⁺ concentration decreased from 17.76% to 0.22%, while at pH 5, the Ni²⁺ concentration was reduced from 2.12% to 0.005%. Lithium was subsequently recovered as Li₂CO₃ by adding Na₂CO₃ at pH 12. These results demonstrate the compatibility of EDTANa₂-based leachates with downstream metal separation and purification processes. Compared with leaching agents reported in the literature, the EDTANa₂+CA and EDTANa₂+AA mixtures used in this study represent the lowest-cost options for recovering Li, Co, and Ni from spent LIBs. These systems not only minimize leaching reagent costs but also significantly reduce acid and reducing agent consumption. Economic evaluations indicated that EDTANa₂+CA is the most cost-effective leaching agent for Li and Co recovery, while EDTANa₂+AA is optimal for Ni recovery. The cost of recovering 100 g of metal was calculated as USD 12.76 for Li, USD 1.65 for Co, and USD 2.50 for Ni. When all experimental results are collectively assessed, it is evident that EDTANa₂—particularly in combination with CA and AA—offers exceptional metal dissolution efficiency, reduced chemical consumption, significant cost advantages, and strong environmental sustainability. These findings demonstrate that chelating organic reagents can provide safer, more selective, and more economical alternatives to conventional mineral acid-based leaching processes. Furthermore, the reduced environmental impact, lower reagent consumption, and high recovery efficiencies indicate that the proposed approach can make substantial contributions to sustainable material management. The results support critical metal supply security and align with circular economy principles by enabling effective reutilization of spent LIBs. In this respect, the study provides valuable contributions to both academic research and industrial practice. Overall, the high leaching recovery percentages, combined with reduced chemical usage, clearly demonstrate the superior process efficiency of the developed hydrometallurgical system. Li and Co recoveries exceeding 99% indicate near-complete transfer of these metals from the cathode material to the solution phase, minimizing metal losses and ensuring efficient mass balance. Although Ni exhibited comparatively lower recoveries, values of approximately 90% are considered highly satisfactory for hydrometallurgical processes involving complex cathode compositions. Time-dependent leaching behavior revealed rapid metal dissolution during the initial stages, followed by diffusion-controlled kinetics at higher recovery levels. EDTANa₂-containing systems achieved high recoveries within shorter reaction times, confirming that stable complex formation enhances leaching kinetics by maintaining dissolved metal ions in solution. These consistent and reproducible results strongly support the industrial applicability of the proposed leaching strategy.
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