Battery Scrap and Biochar Utilization for Improved Metal Recoveries in Nickel Slag Cleaning Conditions

Abstract

Cobalt is a critical, high-value metal used extensively in batteries and other sustainable technologies. To secure its supply in future, it is utmost important to recover cobalt efficiently from industrial wastes and recycled End-of-Life batteries. This study aims at finding ways to improve the reduction of cobalt as well as valuable metals nickel and copper in nickel slag cleaning furnace conditions by using both traditional fossil-based coke and a more sustainable option, low-CO2 footprint biochar, as reductants. A cobalt-rich fraction of battery scrap (25.5 wt% Co) was also used as a secondary feed. The experimental technique consisted of reduction experiments with different times at 1400 °C under inert atmosphere, quick quenching and Electron Probe X-ray Microanalysis. The use of biochar resulted in faster reaction kinetics in the reduction process, compared to coke. Moreover, the presence of battery scrap had a clear impact on the behavior and reduction kinetics of the elements and/or enhanced settling and separation of matte and slag. The addition of scrap increased notably the distribution coefficients of the valuable metals but consequently also the iron concentration in matte which is the thermodynamic constraint of the slag cleaning process.

Worth from Waste: Utilizing a Graphite-Rich Fraction from Spent Lithium-Ion Batteries as Alternative Reductant in Nickel Slag Cleaning

“…In the industrial nickel-slag cleaning process, the Fe/SiO 2 ratio varies between 0.9 and 1.1 [37,38]. In the investigated system, the ratio decreased over time as the Fe concentration in slag decreased, which is fully in line with the previous findings [23,24]. The Fe/SiO 2 ratio in the system with 10 wt.% of SBs was slightly lower than in the system with 5 wt.% of SBs and the lowest in the system with 20 wt.% of SBs in the starting mixture.…”

“…Similarly to previous kinetic studies [8,24,31,32], the drop-quench method and an LTF 16/450 single-phase vertical tube furnace (Lenton, Parsons Lane, Hope, UK) were used in the experiments. The furnace parameters are summarized in Table 1, and a detailed schematic of the furnace was presented earlier in the study of Ruismäki et al [8].…”

“…They also studied the effect of adding battery scrap, which contained ~33 wt.% carbon, to the mixture. It was concluded that biochar enhanced reaction kinetics compared to coke [24]. The presence of battery scrap notably increased the distribution coefficients of valuable metals and iron in matte [24].…”

“…It was concluded that biochar enhanced reaction kinetics compared to coke [24]. The presence of battery scrap notably increased the distribution coefficients of valuable metals and iron in matte [24].…”

“…Pyrometallurgical processes usually consume reductants obtained from fossil fuels, and the estimated global consumption of metallurgical coal rose by 3.8% in 2019 [22]. To further reduce the environmental impact, options for replacing the conventional reductants are being widely researched in both ferrous and nonferrous metal production [23][24][25][26][27]. Al and carbon present in LIBs can act as reductants with Al slagged as Al 2 O 3 and carbon transformed into carbon monoxide [9] or carbon dioxide.…”