A Fundamental Economic Assessment of Recovering Rare Earth Elements and Critical Minerals from Acid Mine Drainage Using a Network Sourcing Strategy

Abstract

In recent years, acid mine drainage (AMD) has emerged as a promising unconventional source of rare earth elements (REEs) and other critical minerals (CMs) such as cobalt and manganese. In this regard, AMD provides a natural heap leaching effect that extracts and concentrates REE/CM from the host strata creating a partially enriched feedstock suitable for downstream extraction, separation, and recovery. While several prior studies have described processes and approaches for the valorization of AMD, very few have described the supply chain and infrastructure requirements as well as the associated economic assessment. To that end, this paper provides a fundamental economic assessment of REE/CM recovery from AMD using a network sourcing strategy in addition to a robust, flexible feedstock separations and refining facility. The methodology of this paper follows that of a typical techno-economic analysis with capital and operating costs estimated using AACE Class IV (FEL-2) guidelines. To demonstrate the range of possible outcomes, four pricing scenarios were modeled including contemporary prices (September, 2021) as well as the minimum and maximum prices over the last decade. In addition, five production scenarios were considered reflecting variations in the product suite, ranging from full elemental separation to magnet REE and CM production only (i.e., Pr, Nd, Tb, Dy, Y, Sc, Co, and Mn). The results of this analysis show that, with the exception of the minimum price scenario, all operational configurations have positive economic indicators with rates of return varying from 25% to 32% for the contemporary price scenario. The optimal configuration was determined to be production of Co, Mn, and all REEs except for mischmetal, which is not recovered. Sensitivity analysis and Monte Carlo simulation show that capital cost and HCl consumption are the two major factors influencing rate of return, thus indicating opportunities for future technology development and cost optimization. Implications of the study and a cooperative profit-sharing model for sourcing are also described.

Effect of Fractionation Columns on the Elution of Rare Earth Elements Recovered from Acid Mine Drainage

“…According to the experimental conditions, the linear velocity of the eluate in the saturated column is 0.37 cm min −1 , meaning that the eluate will take 44.3 min to pass through each fractionation column. In order to illustrate the effect of the interaction between the fractionation column and the REE present in the percolated solution, the amount of REE retained during passage through the fractionation column is given by Equation (10).…”

“…The large volumes of waste generated, and the high cost associated with treatment turns AMD into one of the greatest mining sustainability challenges. Developing research initiatives to identify the potential benefit of considering AMD as a potential secondary source should be encouraged by new regulatory initiatives on sustainable development as well as the circular economy [9][10][11].…”

Sustainable Production of Rare Earth Elements from Mine Waste and Geoethics

“…Secondary sources of REEs include their recovery from waste, including electronic or electrical waste, mine tailings, contaminated residuals from mine drainage treatment, red mud, and phosphogypsum [10,[18][19][20][21][22][23]. Phosphogypsum (PG), originating from the digestion of phosphate rocks, contains up to 0.40% REEs.…”

Recent Progress on Acid Mine Drainage Technological Trends in South Africa: Prevention, Treatment, and Resource Recovery

“…AMD presents a challenge for operational and deserted mines, in shafts below ground, open holes, waste rock mounds, and powder tailings [1][2][3][4]. AMD is more serious in deserted and inactive mines, where there is no pumping occurring and the water table recoils, in contrast to active mines where the water table levels are kept to a minimum through the use of pumps [5][6][7]. Besides the environmental impacts, AMD also impacts sustainability, which includes environmental, community, and financial concerns.…”