Process monitoring of cobalt carbonate precipitation by reactions between cobalt sulfate and sodium carbonate solutions to control product morphology and purity

Jianxin Zhang, Rajaboopathi Mani, Marjatta Louhi-Kultanen*

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

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Abstract

Recovering critical elements from EV batteries is challenging as the separation is a complex process which involves different processing parameters. Cobalt (Co) is one of the metals which ensures the life of EV batteries and here we have successfully precipitated cobalt carbonate (CoCO3) by semi-batch precipitation using cobalt sulfate and sodium carbonate as reactant solutions. The precipitation of cobalt carbonate was investigated by offline Raman spectroscopy, Powder X-ray diffraction analysis, inline Focused Beam Reflectance Measurement (FBRM), and pH measurements. In addition, the effects of various factors including pH, aging time, reactant addition time, mixing speed, and temperature on cobalt carbonate precipitation and the properties of the precipitated solids were investigated. In the process of precipitation, the carbonate ions in the initial electrolyte solution were converted to bicarbonate ions during the addition of acidic cobalt sulfate solution, which consequently decreased the pH in the suspension. When the pH was lower than 8, the carbon mainly existed as bicarbonate and the cobalt carbonate started to precipitate at a high efficiency. Cobalt initially precipitated as cobalt carbonate hydroxide (Co2CO3(OH)2) at a higher pH (9–11) and converted to cobalt carbonate at a lower pH (6.5–8). The crystallite size of cobalt carbonate calculated for the different reaction conditions shows that the growth response is high at longer reactant addition time and high temperature. The morphology of the final cobalt carbonate precipitate was small single spherical crystals and their aggregates. The purity of precipitates could be increased by reducing the aggregation tendency during the precipitation.

Original languageEnglish
Article number106232
Number of pages11
JournalHydrometallurgy
Volume224
Early online date17 Nov 2023
DOIs
Publication statusPublished - Feb 2024
MoE publication typeA1 Journal article-refereed

Keywords

  • Cobalt carbonate precipitation
  • Process monitoring
  • Purification
  • Raman spectroscopy

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