Upcycling spent graphite in LIBs into battery-grade graphene: Managing the produced waste and environmental impacts analysis.

This study focuses on connecting graphite demand to battery materials demand, providing a solution to the identified shortage of battery materials and promoting sustainable development. This research used modified Hummer's method to synthesize graphene from the recycled graphite and compared it with graphene synthesized from purified recycled graphite. The purification of recycled graphite was implemented by acid curing-leaching and calcination. The analysis showed that the reduction reaction effectively removed oxygen-containing functional groups from the graphene, resulting in enhanced quality of the produced graphene. Hummer's waste acid was used as a leaching reagent for different LIBs' cathode types in waste management. The waste acid was found to be a strong reagent for transition metals leaching and obtained almost full recoveries of Li, Co, Mn, and Ni from spent LIB cathodes. The synthesized graphene exhibited higher specific surface areas and conductivity values compared to battery-grade graphite. The electrochemical performance of the graphene sheets in lithium half-cells was evaluated, and it was found that the graphene synthesized from recycled graphite enabled increased lithium insertion at active sites, suggesting its potential for enhanced lithium retention. Furthermore, a life cycle assessment study was conducted to evaluate the environmental impacts of the recycling and synthesis processes. This study demonstrates the potential of recycling graphite from spent battery anodes to produce high-quality graphene with improved electrochemical properties.

Removal of polyvinylidene fluoride binder and other organics for enhancing the leaching efficiency of lithium and cobalt from black mass.

The agglomeration and encapsulation of recoverable materials of interest (e.g. metals and graphite) as a result of the presence of polyvinylidene fluoride (PVDF) in spent lithium-ion batteries (LIBs) with mixed chemistries (black mass) lower the extraction efficiency of metals. In this study, organic solvents and alkaline solutions were used as non-toxic reagents to investigate the removal of a PVDF binder from a black mass. The results demonstrated that 33.1%, 31.4%, and 31.4% of the PVDF were removed using dimethylformamide (DMF), dimethylacetamide (DMAc), and dimethyl sulfoxide (DMSO) at 150, 160, and 180 °C, respectively. Under these conditions, the peel-off efficiencies for DMF, DMAc, and DMSO were 92.9%, 85.3%, and approximately 92.9%, respectively. Using tetrabutylammonium bromide (TBAB) as a catalyst and 5 M sodium hydroxide (NaOH) at room temperature (RT- 21 °C-23 °C), 50.3% of PVDF and other organic compounds were eliminated. The removal efficiency was enhanced to approximately 60.5% when the temperature was raised to 80 °C using NaOH. Using 5 M potassium hydroxide at RT in a TBAB-containing solution, ca. 32.8% removal efficiency was obtained; raising the temperature to 80 °C further enhanced the removal efficiency to almost 52.7%. The peel-off efficiency was 100% for both alkaline solutions. Lithium extraction increased from 47.2% to 78.7% following treatment with DMSO and to 90.1% following treatment with NaOH via leaching black mass (2 M sulfuric acid, solid-to-liquid ratio (S/L): 100 g L-1 at 50 °C, for 1 h without a reducing agent) before and after removal of the PVDF binder. Cobalt's recovery went from 28.5% to 61.3% with DMSO treatment to 74.4% with NaOH treatment.

Potential and current practices of recycling waste printed circuit boards: A review of the recent progress in pyrometallurgy.

Over the last few decades, a substantial amount of e-waste including waste printed circuit boards (WPCBs) has been produced and is accumulating worldwide. More recently, the rate of production has increased significantly, and this trend has raised some serious concerns regarding the need to develop viable recycling methods. The presence of other materials in the WPCBs, such as ceramics and polymers, and the multi-metal nature of WPCBs all contribute to the increased complexity of any recycling process. Among the viable techniques, pyrometallurgy, with the inherent ability to process the waste independent of its composition, is a promising candidate for both rapid and large-scale treatment. In the present study, firstly, the principles of the pyrometallurgical methods for WPCB recycling are discussed. Secondly, the different unit operations of thermochemical pretreatment including incineration, pyrolysis, and molten salt processing are reviewed. Thirdly, the smelting processes for the recovery of metals from WPCBs, as well as the issues surrounding slag formation and subsequent treatment are explained. Fourthly, alternative methods for the recovery of polymers and ceramics, in addition to metal recycling, are elucidated. Fifthly, emission control techniques and the potential for energy recovery are evaluated.

Recovery of heavy metals from waste printed circuit boards: statistical optimization of leaching and residue characterization.

Despite attempts to enhance the recycling of waste printed circuit boards (WPCBs), the simultaneous recovery of major metals of WPCBs using an efficient approach is still a great challenge. This study mainly concerned with applying an effective statistical tool to optimize the recovery of metal content (i.e., Cu, Fe, Zn, Pb, Ni, Sn, and Al) embedded in WPCBs using a leaching agent without any additive or oxidative agent. Another target was to optimize a multi-response recovery process by minimizing time, energy, and acid consumption during the leaching. Effective parameters and their levels, including leaching time (20-60 min), temperature (25-45 °C), solid to liquid (S/L) ratio (1/8-1/20 g/ml), and acid molarity (1-2.7 M), were optimized. A well-established statistical approach (i.e., response surface methodology (RSM)) was applied to precisely quantify and interpret the effects. General optimum conditions for nine responses were introduced with the desirability of ≈ 85%. Finally, the solid residue of leaching was characterized and results showed the morphology, structure, and composition of the residue content (i.e., polymers and ceramics) remained the same after the leaching, indicating the neutral behavior of the leaching process on these two materials. Also, thermal behavior and phase analysis of the original WPCBs and leaching residue were compared and analyzed. Graphical abstract.

Fungal bioleaching of WPCBs using Aspergillus niger: Observation, optimization and kinetics.

In this study, Aspergillus niger (A. niger) as an environmentally friendly agent for fungal bioleaching of waste printed circuit boards (WPCBs) was employed. D-optimal response surface methodology (RSM) was utilized for optimization of the bioleaching parameters including bioleaching method (one step, two step and spent medium) and pulp densities (0.5 g L-1 to 20 g L-1) to maximize the recovery of Zn, Ni and Cu from WPCBs. According to the high performance liquid chromatography analysis, citric, oxalic, malic and gluconic acids were the most abundant organic acids produced by A.niger in 21 days experiments. Maximum recoveries of 98.57% of Zn, 43.95% of Ni and 64.03% of Cu were achieved based on acidolysis and complexolysis dissolution mechanisms of organic acids. Based on the kinetic studies, the rate controlling mechanism for Zn dissolution at one step approach was found to be diffusion through liquid film, while it was found to be mixed control for both two step and spent medium. Furthermore, rate of Cu dissolution which is controlled by diffusion in one step and two step approaches, detected to be controlled by chemical reaction at spent medium. It was shown that for Ni, the rate is controlled by chemical reaction for all the methods studied. Eventually, it was understood that A. niger is capable of leaching 100% of Zn, 80.39% of Ni and 85.88% of Cu in 30 days.

Recovery of lithium and cobalt from spent lithium-ion batteries using organic acids: Process optimization and kinetic aspects.

An environmentally-friendly route based on hydrometallurgy was investigated for the recovery of cobalt and lithium from spent lithium ion batteries (LIBs) using different organic acids (citric acid, Dl-malic acid, oxalic acid and acetic acid). In this investigation, response surface methodology (RSM) was utilized to optimize leaching parameters including solid to liquid ratio (S/L), temperature, acid concentration, type of organic acid and hydrogen peroxide concentration. Based on the results obtained from optimizing procedure, temperature was recognized as the most influential parameter. In addition, while 81% of cobalt was recovered, the maximum lithium recovery of 92% was achieved at the optimum leaching condition of 60°C, S/L: 30gL-1, citric acid concentration: 2M, hydrogen peroxide concentration: 1.25Vol.% and leaching time: 2h. Furthermore, results displayed that ultrasonic agitation will enhance the recovery of lithium and cobalt. It was found that the kinetics of cobalt leaching is controlled by surface chemical reaction at temperatures lower than 45°C. However, diffusion through the product layer at temperatures higher than 45°C controls the rate of cobalt leaching. Rate of lithium reaction is controlled by diffusion through the product layer at all the temperatures studied.