Abstract:
The removal of iron from zinc hydrometallurgical leaching solutions is a critical process. This is because iron ions are oxidized and reduced on the electrode during electrowinning, resulting in the reverse dissolution of cathode zinc, anode corrosion, reduction in current efficiency, and an increase in energy consumption, which severely affects the electrowinning process. Iron removal using the goethite method has the advantages of less slag, easy filtration, and low loss of rare and precious metals. The goethite slag (α-FeOOH) formed by precipitation does not contain the sulfur element, which can reduce impurity elements from the source and decrease the difficulty of pretreatment of molten iron in steelmaking. It can be used as an ironmaking raw material only by increasing the iron content of slag. Therefore, it is currently the mainstream iron removal method. However, iron removal by the goethite method has the problems of long processing time, mixed crystal instability, and low iron content in slag, resulting in poor practical industrial application. Given these problems, this study considers the three goethite iron removal formation processes of oxidation, hydrolysis, and neutralization as the structural framework and summarizes the methods to strengthen and improve the iron removal efficiency of the goethite method, such as the oxygen pressure hydrothermal, conventional oxidation, shear strengthening, seed induction, reactor control, and neutralizer optimization methods. The principles, current state, advantages, and disadvantages of various methods are systematically analyzed. The oxygen pressure hydrothermal method is based on Henry’s law to increase the oxygen partial pressure to promote the dissolution of gas molecules. This method can significantly increase the reaction rate and the iron content of slag but requires substantial equipment. The conventional oxidation method is usually conducted in an environment of low temperature and normal pressure, primarily through a combination of various additives to make the iron removal process highly efficient and effective. Therefore, this method is simple to operate but is highly dependent on the performance of the oxidant. The shear strengthening method changes the solution system environment by applying shear force, changes the ion flow state, increases the contact probability, and improves mass transfer efficiency; however, it has poor environmental adaptability. Seed induction is the most widely used and mature method. By providing growth templates and reducing the nucleation energy barrier, the method enables the crystal structure to be directionally regulated, and the iron removal rate can be improved when supersaturation is not satisfied. However, the seed recycling technology and stability are restricted. The intelligent control technology of the reactor is expected to realize precise control of the process parameters. As an auxiliary condition, it is conducive to efficient production, liberating manpower and improving economic benefits. However, research on the theoretical mechanism of the actual solution remains uncertain, and the establishment of a complete theoretical system for iron removal must be studied. The neutralization agent optimization method can reduce the waste of resources, cost, and the difficulty of subsequent treatments. However, the operating conditions are very strict, and the most critical difficulty is adjusting the dynamic change in pH. Therefore, the purpose of this study is to overcome these limitations, provide ideas for subsequent research on strengthening the goethite method, and suggest a new direction for iron removal by strengthening the goethite method.