Abstract
This research project focuses on investigating ion flotation as an alternative and environmentally friendly method for selectively recovering base metals, such as cobalt, copper, iron, and nickel, from hydrometallurgical pregnant solutions. Hydrometallurgy, encompassing leaching, purification, and metal recovery, is a widely applied technique for extracting valuable metals using aqueous solutions. While conventional purification methods, such as solvent extraction, ion exchange, and carbon adsorption, are commonly used in industry, they present limitations including high costs, environmental concerns, and selectivity challenges.
Ion flotation offers several advantages: low energy consumption, ease of operation, minimal sludge production, and suitability for treating dilute solutions. It uses surfactants that selectively complex with target metal ions, enabling their removal via flotation foams. Despite its promise, the technique has not been widely commercialized in hydrometallurgy, partly due to issues in surfactant selectivity, kinetics, and environmental compatibility.
The study systematically optimized ion flotation for the selective recovery of Cu, Ni, Co, and Fe using HDTAC, HDTAC-Glycolic acid, and HDTAC-Betaine surfactant systems by varying pH, temperature, surfactant concentration, and initial metal concentration. Optimal selective recovery generally occurred within a pH range of 5 to 7, where metal speciation favored the formation of flotation-amenable ionic complexes, allowing for the efficient separation of target metals from iron precipitates.
Temperature optimization revealed an ideal operational window near 35°C, balancing enhanced kinetic energy with the stability of surfactant-metal complexes while minimizing hydrolysis and precipitation losses. Surfactant concentration effects varied by metal species; notably, nickel recovery peaked at moderate surfactant levels (10 drops, 95 ppm HDTAC), beyond which excess surfactant reduced recovery for some metals due to micelle aggregation or competitive adsorption.
Increasing the initial metal concentration generally enhanced recovery, particularly for cobalt and copper, by increasing the possibility of complex formation and adsorption onto bubbles. Iron showed limited recovery due to hydrolysis and precipitation, except at very high concentrations, where ionic strength altered speciation in favor of the ionic form.
Kinetic analyses demonstrated that ion flotation rates followed zero-order kinetics under many conditions, indicating surface saturation-controlled recovery dynamics. Semi-empirical kinetic...