Browsing by Author "Musariri, Bruce"

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    Development of an environmentally friendly lithium-ion battery recycling process
    (Stellenbosch : Stellenbosch University, 2019-04) Musariri, Bruce; Akdogan, G.; Dorfling, C.; Bradshaw, S. M.; Stellenbosch University. Faculty of Engineering. Dept. of Process Engineering.
    ENGLISH ABSTRACT: The main aim of this work was to evaluate the technical feasibility of using organic acids as lixiviants for Co, Li and Ni recovery from lithium-ion batteries (LIBs) and to recover the metals from the resulting pregnant leach solution (PLS). Batch leaching tests to investigate the effects of H2O2 addition, temperature and acid concentration on metal dissolution were performed in a glass jacketed reactor with 300 ml working volume, using citric acid and DL-malic acid as lixiviants. Initial tests to investigate the effects of H2O2 addition indicated that it speeds up the leaching kinetics, hence it was included in successive leaching tests. Leaching tests were performed to investigate the effect of temperature and acid concentration on metal dissolution. Temperature levels of 30℃, 60℃ and 95℃ were used and acid concentration levels of 1 M, 1.25M and 1.5 M were used, with the H2O2 concentration and pulp density being kept constant at 2 % v/v and 20g/L, respectively. Results revealed that the performances of both acids were almost similar with over 95% metal dissolution within 30 minutes, using 1.5M citric acid and 1M DL-malic acid in the presence of 2% v/v H2O2 at 95℃ and 20g/L pulp density. After considering the cost of each acid, citric acid was selected as the more suitable lixiviant and was used in successive tests. Batch solvent extraction tests were performed, with the aim of separating Mn and Al from Co, Li and Ni in the PLS, using D2EHPA as extractant in kerosene diluent. The following variables at the given levels were investigated: D2EHPA concentration (10% v/v and 20% v/v), pH (2.5, 3.0 and 3.5) and organic/aqueous phase ratio (O/A) (1, 2, 3, 4, and 5). The best separation results were obtained using 10% v/v D2EHPA at pH 2.5 and organic phase/aqueous phase O/A ratio 5, where 94% Mn was extracted within 15 minutes, with 47% Al, 7% Co, 9% Li and 3% Ni co-extraction, in one stage. The McCabe-Thiele method was employed under the optimum conditions and it predicted that over 99% Mn can be extracted in two stages. This was verified experimentally and 99% Mn and 89% Al were extracted in two stages, with 13% Co, 17% Li and 6% Ni co-extraction. Metal precipitation tests were carried out at 50℃, 60℃, 70℃ and 80℃ using NaH2PO4 as precipitating agent. The results revealed that the solubility of Li3PO4 decreases with temperature increase, while the solubilities of Co3(PO4)2, Mn3(PO4)2 and Ni3(PO4)2 were not affected, in the investigated temperature range. Five scenarios for the recovery of metals from solution were considered and the proposed separation order in each scenario was experimentally investigated. For each scenario a flowsheet was constructed and mass balances were performed. Comparisons were made based on the mass balances, and the flowsheet in scenario four was selected as the most efficient one. It involves Mn and Al extraction from PLS using D2EHPA, followed by phosphate precipitation at 50℃ (targeting Co and Ni) and subsequent phosphate precipitation at 80℃ (targeting Li). This yields three products: a 93% pure Mn product, a Co-Ni product with 42 wt. % Co and 57 wt. % Ni and a Li product with 89 wt. % Li.