Efficient lithium extraction from oilfield produced water using a 3D-printed microfluidic device

The increasing global demand for lithium, driven by the rapid expansion of electric vehicles and renewable energy storage technologies, necessitates the development of sustainable and efficient extraction methods beyond conventional mining and brine evaporation. Produced water (PW), a high-salinity byproduct of oil and gas operations, has emerged as a promising yet underutilized secondary source of lithium. In this study, we present a novel microfluidic extraction platform based on a 3D-printed Y-shaped slug flow reactor for selective lithium recovery from synthetic and real PW samples. The device was fabricated using stereolithography (SLA) 3D printing and polydimethylsiloxane (PDMS) casting, enabling precise control over channel geometry and fluid behavior. Bis(2,4,4-trimethylpentyl) phosphinic acid dissolved in decane with 2% hexanol was employed as the organic extractant phase. Optimization studies revealed that lithium extraction efficiency peaked at pH 6.0, with a maximum recovery of 89% from synthetic solutions. The platform also demonstrated effective performance across varying lithium concentrations, with measurable recovery observed even at 20 mg/L. When applied to real PW samples containing 136 mg/L lithium and high concentrations of competing ions, the system achieved 36% recovery, which increased to 75.7% following selective removal of divalent cations. The microfluidic system outperformed traditional methods in terms of selectivity, reagent economy, and operational speed, while offering a scalable and environmentally friendly alternative for lithium recovery. This work establishes a foundation for the integration of microfluidic extraction with pre-treatment strategies, highlighting its potential for deployment in critical mineral recovery from industrial waste streams.