RECOVERY OF LITHIUM IN HYDRAULIC FRACTURING FLOWBACK AND PRODUCED WATER USING A MAGNESIUM-LITHIUM MANGANESE OXIDE COMPOSITE

Flowback and produced water (FPW), a waste byproduct that is discharged from hydraulic fracturing operations of oil and gas wells, is a potential lithium resource. Seip et al. (2021) successfully demonstrated that spinel lithium manganese oxide (LMO) sorbents can effectively extract lithium (Li) from FPW, and lithium uptake reached 18 mg g^-1. However, there was a considerable amount of manganese (Mn) loss (~ 9.1%) during acid desorption, resulting in sorbent structural distortion, also known as Jahn-Teller distortion. Extant research shows that doping the Mn-spinel with cations can reduce the structural Mn distortion in battery electrode applications. In our research, the Mn-spinel is doped with different concentrations of magnesium (Mg). Magnesium, a common element in FPW and one that is environmentally benign, makes it a promising and inexpensive dopant. Our preliminary results using synthetic brines show that doping LMO with Mg can effectively reduce sorbent Mn loss by more than half by reinforcing its structure. Analyses such as X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray absorption spectroscopy (XAS), are further used to constrain the structure of doped spinel sorbents, which provides an in-depth understanding of how Mg is coordinated in the manganese lithium spinel and the mechanisms by which Mg inhibits Mn loss. Our results provide an evaluation of the performance of Mg-doped sorbents in Li recovery from FPW, and provide the data needed to conduct further Mg and cation doping experiments to optimize the sorbent for specific brine chemistries.

References

Seip, A., Safari, A., Pickup, D. M., Chadwick, A. V., Ramos, S., Velasco, C. A., Cerrato, J. M., & Alessi, D. S. (2021). Lithium recovery from hydraulic fracturing flowback and produced water using a selective ion exchange sorbent. Chemical Engineering Journal, 426(2), Article 130713. https://doi.org/10.1016/j.cej.2021.130713