Integrated adsorption–membrane process for lithium recovery from shale gas flowback fluid

Shale gas fracturing flowback fluid represents a promising unconventional lithium resource with concentrations reaching industrial grades, while simultaneously presenting significant wastewater treatment challenges. This study systematically investigates the complete research chain from flowback fluid characteristic analysis through extraction technology optimization to engineering feasibility validation, with particular emphasis on environmental sustainability and circular economy principles. Water quality analysis of Yang 101 well block in Sichuan Basin revealed lithium concentrations ranging from 26.01 to 53.89 mg/L, with high total dissolved solids (14,000–33,000 mg/L) and complex organic-inorganic composition. A pretreatment-lithium enrichment-deep purification technical framework was constructed and optimized, incorporating adsorption-membrane coupling process. The aluminum-based adsorbent demonstrated superior performance with adsorption capacity of 3.0 mg g −1 (3,000 mg kg −1 ), lithium recovery rate of 87%, and eluate lithium concentration exceeding 500 mg/L. Comprehensive mechanistic studies using XRD, XPS, and FTIR characterization revealed the selective Li+ adsorption mechanism involving layer-intercalation and electrostatic interactions. Life cycle assessment (LCA) analysis demonstrated that the proposed process achieves 42% lower carbon footprint (2.8 kg CO2-eq/kg Li2CO3) compared to conventional spodumene mining, with > 90% COD removal and 80% water recovery enabling circular water reuse. Long-term stability evaluation over 30 adsorption-desorption cycles demonstrated promising pilot-scale performance with potential for industrial deployment, achieving < 5% capacity decay. Economic analysis indicated that the integrated process could achieve daily production of 30.1 kg battery-grade lithium carbonate at an estimated production cost competitive with conventional sources, with NPV of 3.86 million CNY at 8% discount rate, IRR of 7.95%, and payback period of 12.19 years over a 20-year project lifetime. This research provides both theoretical foundation and practical pathway for sustainable industrial development of unconventional lithium resources from oilfield wastewater, contributing to diversified lithium supply and waste valorization objectives.