Niobium and tantalum recovery from the primary source and from tin slag, an industrial challenge: A review

Niobium (Nb) and Tantalum (Ta) are used to increase materials' mechanical resistance and produce lighter alloys. Worldwide Nb production reached 78 000 t in 2020. The reduced ore offer justifies the recycling of these metals from tin slag, contributing to the circular economy. Nb2O5 and Ta2O5 extraction either from the primary source or the tin slag is an industrial challenge. Nb and Ta dissolution processes already implemented are fluoride leaching, sulphuric leaching, alkaline leaching, and alkaline roasting. The fluoride process raises environmental concerns about waste control. The sulphuric method can be managed to have higher Nb and Ta extraction in a less aggressive process, if some changes are implemented, such as increasing the number of extraction steps, decreasing the pulp density, or increasing the temperature; however, the efficiency of this methodology must be tested for tin slag. The alkaline method seems to be more selective to Nb and Ta by reactants and temperature control. Despite those well-established Nb and Ta treatments, they must be adapted to recover Nb and Ta from slag. The slag has low Nb and Ta content, while high Si and Ca concentrations exist in the matrix. This paper brings the main methods used to extract the Nb and Ta from the primary resources and an overview of Nb and Ta recovery from the slag. This investigation comes as a tool to guide the development of new methods to recover Nb and Ta from low-grade sources such as tin slag.

Automated summary

Niobium (Nb) and Tantalum (Ta) are used to enhance mechanical resistance and produce lighter alloys. Nb production reached 78,000 tons globally in 2020. Recycling of these metals from tin slag contributes to the circular economy. Industrial challenges exist in extracting Nb2O5 and Ta2O5 from primary sources or tin slag, but various dissolution processes have been implemented.