PRE-TREATMENT METHODS FOR FLOWBACK AND PRODUCED WATER BRINES PRIOR TO DIRECT LITHIUM EXTRACTION

Ion-exchange technologies are being employed to extract lithium from brines. This study investigates the manganese oxide, Li_1.6Mn_1.6O₄, as an ion-exchange material to extract lithium from flowback and produced water (FPW) from hydraulically fractured wells. The main problem is the reductive dissolution of the sorbent by dissolved organics and loss of manganese to solution. Dissolved organics could reduce cyclability of the sorbent and pre-treatment of FPW brines before ion-exchange for lithium extraction is a promising technique to improve efficiency and performance. We tested if a combined approach of aeration and filtration could effectively remove organics, prevent Mn-loss of the sorbent and improve the extraction performance. In Alberta, Canada, there are significant lithium-bearing brines (>75 ppm) in the Fox Creek region. Brine from the Duvernay Fm. have TDS values >170,000 ppm and significant Fe (II), silica, barium, sulfate, and strontium concentrations. For the aeration process, 800 ml of brine was aerated at 0.3 L/min using compressed air for 24 h. Aliquots were taken for ferrozine iron assay, TOC analysis, and pH. Results were compared for the raw brine, aerated brine at pH 3.78, and aerated brine at pH 6.0. After aeration, the brine was filtered with a 0.03 μm filter. Lithium extraction was conducted on the three treated brines using a Li_1.6Mn_1.6O₄ sorbent. Samples were taken after lithium loading, and after final lithium desorption into acid. Performance was determined using an ICP-MS to measure lithium recovery and Mn-loss. The iron assay displays the oxidation of Fe(II) to Fe(III) as the brine is aerated. During aeration, oxidation of Fe(II) is minimal in the raw brine, given the low initial pH of 3.78. In the pH-adjusted brine, a steady decline in Fe²⁺ concentrations is observed, as well as approximately 20% decrease in the TOC concentration. The change in TOC and Fe²⁺ after aeration could be due to organics adsorbing to ferric oxyhydroxide precipitates produced through the oxidation of Fe(II), or through volatilization, which are removed during filtration. The results of this study are valuable in understanding the effect of decreasing total organics on manganese loss, and in assessing low-cost and easy to implement pre-treatment methods for hydrocarbon brines prior to lithium ion-exchange processes.