Extraction of Nickel Cobalt and Manganese from Spent NMC Cathodes by Malonic Acid Leaching

Abstract

This study investigates the feasibility of using malonic acid as a standalone leaching agent for the extraction of nickel, cobalt, and manganese from NMC-type cathode mass without the addition of external reducing agents. A systematic optimization of the leaching process parameters, including acid concentration, temperature, solid-to-liquid ratio, and contact time, was performed. It was established that the optimal process conditions are a malonic acid concentration of 2 M, a solid-to-liquid ratio of 20 g/L, a temperature of 60 °C, and a contact time of 80-90 min. Under these parameters, extraction rates of 98% for nickel, 97% for manganese, and 93% for cobalt are achieved. Increasing the temperature above 60 °C leads to efficiency decrease due to thermal decarboxylation of malonic acid. The addition of hydrogen peroxide under optimal conditions does not improve but rather decreases extraction efficiency. The high efficiency is attributed to the dual function of malonic acid, acting simultaneously as an agent for acidic breakdown of the oxide lattice and as a chelating ligand stabilizing metal ions in solution.