Cellulose Fiber Crystallizer for Continuous Evaporative Lithium Enrichment from Low-Quality Brines

Lithium is a critical mineral with a rapidly expanding global market. Nontraditional sources such as oilfield brines have emerged as promising yet underutilized sources of lithium. However, existing extraction techniques, including evaporation ponds and direct lithium extraction methods, face substantial limitations when applied to these dilute resources, including prolonged processing times, high energy and freshwater requirements, and low selectivity between lithium and competing monovalent ions, making lithium recovery from low-concentration brines inefficient and economically unattractive. In this study, we present a continuous and passive lithium extraction approach utilizing a fiber crystallizer driven by a capillary siphon process. With a simplified monovalent Marcellus-type brine, the system achieved 596-fold lithium enrichment and a maximum Li⁺/Na⁺ separation factor of 11,182 through staged fractional crystallization. For a more complex brine containing high Ca²⁺ and Mg²⁺, lithium was enriched approximately 17-fold, from approximately 95 mg L^-1 to 1.641 g L^-1, with approximately 87% lithium recovery and a Li⁺/Na⁺ separation factor of approximately 182. These results demonstrate the strong potential of fiber crystallization for lithium extraction from complex oilfield brines, with pretreatment offering further opportunities to improve performance.