Optimisation of nickel extraction from spent cathodes of NiMH batteries by hydrometallurgical process through experimental design

Abstract

This paper presents the development of a novel process for the extraction of Ni contained in spent cathodes of NiMH batteries, by using an organic leaching agent, acetic acid (CH3COOH), in the presence of hydrogen peroxide (H2O2) as a facilitator of cathodic dissolution. The operating parameters studied were temperature, time, and concentration of CH3COOH and H2O2, applying experimental design with subsequent optimisation using the response surface methodology (RSM). The maximum empirical extraction of Ni, of 99.9%, was achieved under the following conditions: temperature, 75°C; CH3COOH and H2O2 concentrations, 6% (v/v) and 1.5% (v/v), respectively; reaction time, 30 min; stirring speed, 330 rpm and solid–liquid ratio, 25 g/L. To minimise the values of parameters such as the temperature and concentration of leaching agent and H2O2, a numerical optimisation was carried out, leading to an optimal extraction value of 95.6%.