强化针铁矿法除铁的研究现状和进展

Research progress of enhanced iron removal by the goethite process

  • 摘要: 湿法炼锌浸出液中铁的去除是一道重要的工序,这是因为电积时铁离子会在电极上发生氧化还原,造成阴极锌的反溶、阳极腐蚀、降低电流效率和增加能耗,严重影响电积工艺. 针铁矿法除铁具有渣量少、易过滤、稀贵金属损失低等优点,沉淀生成的针铁矿渣(α-FeOOH)不含S元素,从源头减少杂质元素,使铁水预处理工艺降低处理难度,只需提高渣中铁含量就可作为炼铁原料,因此是目前主流的除铁方法. 但针铁矿法除铁存在反应时间长、晶型混杂不稳定以及渣中铁含量低等难题,导致实际工业应用效果不佳. 针对上述问题,本文以氧化、水解和中和三个针铁矿法除铁过程的形成环节为结构框架,综述了强化改善针铁矿法除铁效率的方法,如氧压水热法、常规氧化法、剪切强化法、晶种诱导法、反应器控制和中和剂优化法等,系统分析了各种方法的原理、现状、优缺点. 氧压水热法依据亨利定律提高氧分压促进气体分子的溶解,该法可显著提高反应速率和渣中铁品位,但对设备要求高;常规氧化法通常在低温常压环境中进行,主要通过加入各种添加剂,使除铁过程发挥高效率、高效果,因此该法操作简便,但高度依赖氧化剂性能;剪切强化法以施加剪切力来改变溶液体系环境,使离子流动状态改变,增加各反应物接触几率,从而改善传质,提升效率,但对环境适应性差;晶种诱导法是应用最广泛和成熟的方法,通过提供生长模板和降低成核能垒,在不满足过饱和的条件下,可定向调控晶体结构,提高铁去除率,但晶种循环回收技术及其稳定性受到制约;反应器智能控制技术有望实现工艺参数的精准调控,将其作为辅助条件有利于高效生产、解放人力、提高经济效益,但目前对实际溶液理论机理的研究仍然模糊,对建立除铁的完整理论体系仍待研究;中和剂优化法可以减少资源浪费、降低成本、减少后续处理难度,但对操作条件极为严格,关键的难点是对pH的动态变化调节. 最后,本文提出强化针铁矿法研究思路和想法,并展望了强化针铁矿法除铁新方向.

     

    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.

     

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