Separation Performance of Lithium and Calcium from Synthetic Geothermal Brine Using Electric Field-assisted Membrane

Abstract

Green low-carbon technology development has spurred an increased demand for lithium. Brine, including geothermal brine, is the world's largest source of lithium. However, the low lithium content and the presence of other ions pose challenges in concentrating lithium. An electric field-assisted membrane is a separation approach combining nanofiltration membranes with an electric field as an additional driving force, effectively separating lithium from magnesium and strontium. This study was conducted to separate lithium and calcium from synthetic geothermal brine using an electric field-assisted membrane. The separation process is conducted for lithium (50 ppm) and calcium (300, 800, and 2,000 ppm) with variations in electrical voltage (0V, 2V, and 3V). The decrease in lithium rejection reaches up to 50% at an electrical voltage of 2V. Conversely, the increase in electrical voltage does not significantly impact calcium rejection (calcium rejection remains at 89% with an electrical voltage of 3V) and the permeate flux for lithium and calcium. The increasing calcium concentration affects permeate flux significantly but does not notably affect calcium rejection, with the rejection remaining above 85%. The findings suggest the feasibility of concentrating lithium through electric field application without compromising calcium rejection within a single salt solution system.