Technologies for processing iron-containing secondary resources from nickel production

Abstract

The goal is to systematize and analyze existing technological approaches to the processing of iron hydrate cake and wastewater neutralization cake generated during hydrometallurgical production of nickel, with an assessment of their advantages, disadvantages and prospects for implementation. As part of the review study, an analysis of patent and scientific and technical literature on methods of handling these types of waste was carried out. The physical and chemical characteristics of raw materials were considered, and the key problems associated with their storage and processing were identified. The article discusses in detail the main directions of disposal. Traditional storage after dewatering is a temporary solution leading to irretrievable loss of metals and the need for future expensive reclamation. Hydrometallurgical methods are aimed at selective extraction of non-ferrous metals (sulfuric acid leaching, including autoclave leaching with precipitation of iron in the form of jarosite). Despite the technical feasibility, their widespread use is constrained by economic inexpediency due to low concentrations of target components and high capital intensity. Pyrometallurgical methods involve adding cakes to the mixture for agglomeration or firing together with nickel concentrate. The main obstacles are the need for preliminary drying and grinding, deterioration of technological indicators of autogenous processes, and increased energy consumption. Their use in construction materials (as a filler for concrete, a component of cement compositions or binders) allows solving the problem of volume utilization, but does not provide for the extraction of valuable metals, and also requires careful control over the environmental safety of the final prod-uct. The analysis showed that there is currently no universal and cost-effective solution for the integrated processing of iron hydrate cake and neutralization cake from nickel production. The most common practice of dehydration and storage does not meet the long-term goals of resource conservation and environmental safety. Specialized hydro- and pyrometallurgical technologies, while technically feasible, require significant investment and are often unprofitable with the current composition of waste. In this regard, it is proposed to involve these secondary resources in the ferrous metallurgy industry, where they can be used as sources of alloying elements. Iron hydrate cake is also a source of iron, and neutralization cake contains fluxing compounds. The most realistic at the present stage seems to be an integrated approach that combines pre-enrichment to increase the concentration of metals with subsequent hydrometallurgical processing or the creation of safe building materials with guaranteed immobilization of toxic elements. To choose the best path, further research is needed to reduce the cost of processes and develop complex technological schemes