Lithium extraction from oil and gas produced water: resource characteristics, technological challenges and future...

Driven by the global transition to low-carbon energy and the rapid development of the electric vehicle industry, the finite supply of lithium (Li) resources coupled with growing demand will exacerbate the imbalance between supply and demand. Current Li supply primarily relies on traditional resources such as salt lake brines and hard-rock ores. However, these resources exhibit concentrated geographic distribution and incur high environmental costs, posing severe constraints on sustainable resource utilization and supply chain security. Oil and gas produced water (OGPW), a persistent byproduct of hydrocarbon extraction, is regarded as a highly promising unconventional Li resource due to its widespread distribution and Li content far exceeding industrial-grade standards. Compared to traditional salt lake brines, OGPW exhibits characteristics such as low Li concentrations, high salinity, complex ionic compositions, abundant organic contaminants, and harsh field conditions, which substantially increase the technical difficulty of Li extraction. This review systematically summarizes recent advances in Li extraction technologies, covering evaporation-precipitation, solvent extraction, adsorption, membrane separation, and electrochemical technologies, while critically evaluating their applicability to OGPW under complex compositions and field conditions. The study emphasizes that efficient Li recovery from OGPW cannot rely on a single extraction technology. Instead, customized integrated process designs are required, combining complementary separation mechanisms to address the complex composition and field conditions of OGPW. Future research should focus on developing integrated process systems that synergistically achieve Li extraction and water treatment, thereby fulfilling dual objectives of resource recovery and environmental management.