Quantum chemical calculation assisted efficient lithium extraction from unconventional oil and gas field brine by β-diketone synergic system

Abstract

The lithium extraction from emerging unconventional oil and gas (UOG) field brine by β-diketone synergic system was established and systematically studied for the first time. A synergistic system consisting of dibenzoylmethane (DBM) and trioctylphosphine oxide (TOPO) was screened for lithium extraction through high-precise DFT calculation, and the synergistic effects were revealed by FT-IR analysis. A state-of-the-art Li+-Mg2+-Ca2+ co-extraction and Li+ selective stripping (CESS) process was proposed to achieve high lithium recovery efficiency. The effects of saponification, phase ratio, extractant composition and stripping acidity on extraction efficiency were systemically studied using real UOG field brine. After three-stage countercurrent extraction, the lithium extraction efficiency reached 98.1 % with the DBM concentration of 0.25 mol/L, TOPO concentration of 0.25 mol/L, and saponification of 70 %. After selective stripping and scrubbing with gradient HCl concentrations, Li+ was further separated from Na+, Mg2+ and Ca2+. The mass ratio of Mg2+/Li+ was reduced by 49.7 times, Na+/Li+ was reduced by 102.4 times. This work bridged the gap in the solvent extraction of lithium resources from UOG field brines and provided ideas for UOG field resource exploit and comprehensive utilization.