Quantifying the degree of selectivity in a Flocculation-Flotation process of LiCoO2 and graphite using scanning electron microscopy and image processing analysis

Tommi Rinne, Mohazzam Saeed, Rodrigo Serna-Guerrero*

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

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Abstract

This research article studies selective flocculation as a means for improving flotation of lithium-ion battery active materials using mixtures of pure LiCoO2 (LCO) and graphite. Scanning electron microscopy (SEM) combined with image analysis via density-based spatial clustering of applications with noise (DBSCAN) is presented as a novel method to quantitatively determine the degree of selectivity in a process that applies selective flocculation as a conditioning stage for froth flotation. SEM was shown to provide visual proof of flocculated particles, even in dried froth samples. Under optimal flocculant concentration of 10 g/t only a few flocs were detected in the froth concentrate, suggesting that heteroflocculation of LCO and graphite was minimized under said conditions. Using a flocculant concentration in excess (50 g/t) resulted in multiple flocculated LCO particles within the froth, indicating loss of flocculation selectivity. These results were corroborated by batch flotation experiments, which showed that treating the pulp with 10 g/t flocculant concentration yielded a graphite froth product at a grade of 98.2 %, compared to 98.1 % recovered from a non-flocculated pulp. An excess flocculant concentration led to a drastic reduction in graphite grade. Similar graphite recoveries were observed in all flotation experiments, indicating that the reduced graphite grade with excess flocculant was a result of hydrophobic heteroflocs carrying entrapped LCO to the froth. Proper pH control throughout the experiment prevented a negative influence of flocculation on the kinetics of graphite recovery, which had been reported in earlier research. The results suggest that selective flocculation is a potential method for improving the separation efficiency of graphite from Li-ion battery waste, and that SEM/DBSCAN can be applied for characterization of selectivity in combined flocculation-flotation processes.

Original languageEnglish
Article number108644
Number of pages12
JournalMinerals Engineering
Volume209
Early online date2 Mar 2024
DOIs
Publication statusPublished - Apr 2024
MoE publication typeA1 Journal article-refereed

Keywords

  • DBSCAN
  • Direct recycling
  • Froth flotation
  • Lithium-ion batteries
  • Scanning electron microscopy
  • Selective flocculation

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