Cavitation-enabled selective goethite crystallization for efficient iron removal and suppressed Cu/Zn loss in...

In hydrometallurgical zinc production, efficient iron removal and retention of valuable metals like copper and zinc with minimal loss are essential for achieving environmentally friendly, energy-efficient, and high-value-added purification operations. Traditional goethite methods exhibit slow iron precipitation kinetics, disordered aggregate formation, and poor suppression of mechanical entrainment and non-selective coprecipitation of copper and zinc during iron removal. To address the aforementioned bottlenecks, this paper innovatively proposes a new method for the synergistic separation of iron, copper, and zinc from zinc sulfate solutions using an ultrasonic-enhanced goethite process, and systematically investigates the effects of process parameters on iron precipitation behavior and the loss patterns of copper and zinc. The results showed that ultrasonic intensification increased the iron precipitation rate by 4.67%, while reducing the loss rates of copper and zinc by 6.62% and 8.13%, respectively. Further analysis using multi-scale characterization techniques, including XRD, XPS, particle size distribution, EPR, SEM-EDS, TEM, EXAFS, and EPMA, revealed that the coupling of ultrasonic cavitation and oxidation processes enhances the oxidation, hydrolysis, and hydroxyl cross-linking reactions of Fe. Meanwhile, this optimized the particle size distribution, surface active sites, and local coordination environment of the precipitated particles. Consequently, it reduced the mechanical entrapment of copper and zinc in the precipitate, as well as their non-selective surface adsorption and co-precipitation. This study overcomes the limitations of traditional goethite-based processes, which focus solely on iron removal, and provides a new theoretical basis and process approach for the efficient co-separation of iron and valuable metals in complex zinc sulfate systems, as well as for the green intensification of the purification process in hydrometallurgical zinc production.