Enhanced extraction of nickel from limonitic laterite via improved nitric acid pressure leaching process

At a time when the world is practicing energy conservation and emission reduction in order to achieve carbon neutrality, it is particularly important to enhance the extraction of valuable metals from low-grade resources. In the current process of extracting valuable metals from limonitic laterite, the characteristic that the laterite is a highly porous mineral is often overlooked. Inspired by our previous studies on the porous kinetics of limonitic laterite during nitric acid pressure leaching, this paper investigated the enhanced recovery of nickel from limonitic laterite. Response surface methodology was first used to optimize the nitric acid pressure leaching limonitic laterite process parameters to obtain the optimum conditions (Temperature: 194 °C, Time: 75 min, Liquid/Solid: 3.4 mL/g, and the initial nitric acid concentration: 178 g/L). Based on this process condition, two enhancement options were performed, namely bleed air treatment and adding surfactant. The results showed that both bleed air treatment and the addition of surfactant promoted the leaching of limonitic laterite. The best enhancement was achieved by DTAB (dodecyl trimethyl ammonium bromide), with a 5.22% increase in nickel extraction under optimal process conditions (from 90.63% to 95.85%). Furthermore, the analysis of the reinforcement mechanism shows that the bleed air treatment mainly removes the obstruction of the leaching reaction by the air in the pore, thus accelerating the reaction. The reinforcing effect of surfactants is mainly based on improved diffusion efficiency and increased permeability.