Accurate Lithium Quantification in Hypersaline Brines Using a Polybutadiene Maleic Acid Based Ion Exchange Column

Abstract Accurately measuring lithium content in hypersaline brines with total dissolved solids (TDS) exceeding 150,000 ppm is challenging due to matrix interferences and dilute lithium concentrations. The objective of this work is to demonstrate a reliable method based on polybutadiene maleic acid (PBMA) resin for precise lithium quantification, even at low concentrations and in highly complex brine matrices, reducing the uncertainty in prospecting for lithium brine resources. An ion chromatography system with a degasser, suppressor, ion exchange columns, and conductivity detectors was used. Samples were diluted to keep TDS below 500 ppm to protect the ion exchange columns. Suspended solids were removed using 0.45-micron syringe filters. The cation-exchange column was based on a PBMA resin. The method's accuracy was evaluated using seven synthetic brines containing lithium, sodium, potassium, magnesium, calcium, strontium, barium, chloride, bromide, and iodide. Lithium concentrations were calculated from conductivity-based chromatograms through numerical integration, and density measurements were used for mg/L to ppm conversions. Lithium calibration using standard solutions yielded a linear regression coefficient of 0.99998 with a relative standard deviation of 0.583%. The lithium peak was numerically integrated from chromatograms based on conductivity measurements (μS/cm vs. time in minutes). Among the detected cations, lithium exhibited the shortest retention time (6-6.5 minutes), potentially reducing matrix effects and minimizing peak overlap. This behavior is attributed to the ion exchange resin's selectivity and lithium's distinct physicochemical properties. Test brines with TDS exceeding 220,000 ppm were analyzed, containing lithium concentrations between 10 and 200 ppm. The correlation coefficient obtained from the measured brine samples was 0.9983, suggesting that the method effectively quantified lithium with limited matrix interference. Compared to conventional spectroscopic methods, this approach demonstrated promising performance under extreme salinity conditions. This can enable the accurate prospecting of brine resources for lithium. This study introduces a robust method for lithium quantification in brines with significant matrix interferences. While typical analytical methods for diluting lithium solutions using spectroscopic or spectrometric techniques, this work demonstrates the reliability of PBMA resins in ion chromatography, enabling precise lithium measurements with simple conductivity detection. This approach can support lithium exploration and prospecting efforts by offering a reliable analytical method for complex brine systems.