Concentrating brine for lithium recovery using GO composite pervaporation membranes

The extraction process of highly demanded lithium from brine normally starts with a solar evaporation pond to increase the lithium concentration, which takes more than a year and is weather-dependent. This work evaluated the enrichment of lithium from salt lake brine using graphene oxide (GO) composite pervaporation membrane with the crystallizer unit. The deposition of stacked GO layer on the commercially available hydrophobic membranes can tackle the membrane wetting and salt crystallization issues. The initial water flux was 11 L/m2 h at 70 °C, which was 20 times higher than that of solar evaporation pond (~0.5 L/m2 h) and 10 times lower footprint. With high initial feed concentration (>200 g/L of salt) the GO composite pervaporation membrane increased lithium concentration from 0.3 to 1.27 g/L (73% feed volume reduction). Assuming 10 m3/day capacity of the proposed solar pervaporation system, an economic analysis showed that the technique is not economically sustainable when solely aiming at the lithium extraction, while it becomes competitive with the traditional method when aiming at simultaneously producing deionized water and lithium. A payback time of 3.6–27 years is achievable with the sale price of water and LiOH at US$ 0.3–1 per 20 L and US$ 20 per kg, respectively. A continuous process is also possible with backup gas heater and waste heat.