Hydrometallurgical recovery of nickel from oxidized ores

A significant portion of the world’s reserves of Ni-containing raw materials (40–66 %) is concentrated in oxidized nickel ores. One of the alternatives to the high-cost pyrometallurgical and ammonia-carbonate methods for processing such ores could be the chlorammonium recovery of nickel from relatively low-grade ores. The halide-ammonia decomposition and recovery technology of nickel from oxidized nickel ores, supplemented by a sorption process, is less stage-intensive and simpler in practical implementation. Nickel adsorption recovery is feasible using carbon sorbents that exhibit high chemical stability, withstand high-temperature exposure, and strong acidic treatment. Sorbents were obtained through steam-gas activation of extracted carbonizates from fossil coals. The sorption capacity for Ni(II) ions was studied, and the patterns and characteristic parameters of the process on carbon sorbents were identified using adsorption isotherms while varying experimental conditions. The experimental results were processed using the Freundlich and Langmuir equations. The sorbents have several distinctive features determined by their predominant microporous structure and multifunctional surface with active complex-forming atomic groups, characteristic of ampholytes with cation- and anion-exchange properties. The adsorption process is described by a pseudo-first-order equation with rate constants ranging from 0.204 to 0.287 s^–1. For the adsorption recovery of Ni(II), a scheme with two adsorbers and a pseudo-fluidized sorbent bed is proposed. Nickel desorption and sorbent regeneration were carried out with a 2.3 % sulfuric acid solution, desorbing 95 to 98 % of nickel. Standard chemical machinery and equipment are recommended for these processes.