关键词: 剪切强化, 针铁矿, 晶体生长, 均相成核, 异相成核

Abstract: Removing iron from the solution is an indispensable procedure to ensure the quality of zinc products in zinc hydrometallurgy. Regarding the requirements of economic cost and environmental protection, the goethite method has a significant advantage in iron removal. However, due to the existing regulation technology of iron removal by the goethite process, the crystal shape of goethite residue is difficult to be controlled stably, which leads to the problems of poor filtration performance. At the same time, the iron grade is low and the zinc content is high in the produced goethite residue. The mechanism of crystal structure, microscopic morphology and element occurrence in the homogeneous and heterogeneous nucleation crystal growth process was investigated by X-ray diffraction spectroscopy, scanning electron microscope, and inductively coupled plasma emission spectroscopy in the ZnSO4-FeSO4 system. Moreover, the regularity of iron removal by shear-enhanced goethite was verified in a real solution. The results showed that there were no obvious goethite crystal characteristics at the initial stage of iron settling slag in the process of homogeneous nucleation, and the amorphous nuclei were spherical. The iron grade and zinc contented fluctuate greatly, increased from 43.13wt% and 4.57wt% in the early stage to 57.76wt% and 6.12wt%, respectively. In the early stage of heterogeneous nucleation, the secondary growth of the seed was the main method, which effectively avoided the generation of a large number of amorphous iron residues. Compared with homogeneous nucleation, the size of the crystal was larger and the crystallinity was higher, and the zinc was finally controlled at 5.60wt%. Compared with the simulated solution, the growth and development of goethite crystal in the real solution with complex properties were more difficult to control, but it can ensure the goethite crystal precipitation, and the content of iron and zinc in the iron-settling slag was controlled at 57.63wt% and 5.90wt%, respectively. The industrial zinc oxide fume was used as a neutralizing agent to obtain the final goethite residue containing 52.59wt% iron and 6.93wt% zinc. This study provided a theoretical basis for the application of shear strengthening technology and the selection of nucleation mode in the hydrometallurgical zinc-goethite process.

Key words: shear strengthening, goethite, crystal growth, homogeneous nucleation, heterogeneous nucleation