Exploration of fertilizer industry wastes as potential source of critical raw materials

This paper explores the possibility of using wastes (i.e. solid phosphogypsum (PG), process waters and edge outflows) generated by a fertilizer plant in SW Spain as a source of elements of economic interest, estimating the available metal reserves and discussing the technological and economic pros and cons of this potential source of raw materials. In general, elements of economic interest are found in these wastes below of the grades commonly reported in conventional deposits. However, the huge tonnage of wastes stockpiled constitutes a significant secondary source of elements. Around 30,400 t of B, 28,000 t of rare earth elements (REE), 1800 t of U, 1400 t of Cr, 1300 t of V and lesser amounts of other elements of economic interest (e.g. Cu, Ni, Sc and Ga) are enclosed in the solid PG while lower amounts are found in process waters (e.g. 1360 t of Zn, 760 t of V, 630 t of U and Cr, 225 t of Cu, 160 t of Ni, 190 t of REE). Considering the market metal prices, the reserves contained in the Huelva PG stack have a potential value of around 8937 million USD, which mainly correspond to PG (97% of total value). The recovery of these elements is technically feasible, although intense research in refining processes is needed in order to increase the purity of the final product. The results of this study could be of interest in other PG stacks worldwide to provide more sustainable and cost-effective management of these wastes.