Method of concentrating lithium-containing solutions and recovering lithium therefrom

A system for concentration and recovery of lithium containing solutions, the system comprising:

• a feed of brine solution including lithium sulfate and one or more aqueous solutions of sodium sulfate, potassium sulfate, calcium sulfate, and sodium chloride, the feed brine solution having a total salt content in the range of 20 to 31.5 wt. %, and the feed brine solution having a content of lithium sulfate in a range of 1 to 2 wt. %;
• an initial separation stage including a pre-treatment membrane to which the brine solution is introduced via an input that receives the feed of brine solution at a pressure that is less than the osmotic pressure of the feed brine solution, an initial permeate outlet on the opposite side of the pre-treatment membrane relative to the feed, and an initial retentate outlet on the same side of the pre-treatment membrane as the feed, wherein an initial permeate that passes through the pre-treatment membrane exits the initial separation stage through the initial permeate outlet, and an initial retentate that does not pass through the pre-treatment membrane exits the initial separation stage through the initial retentate outlet, and the initial retentate includes lithium sulfate and a precipitate of at least one of the salts other than lithium sulfate;
• a final separation stage including a nanofiltration membrane to which the initial permeate is introduced via an input that receives the initial permeate from the initial separation stage at a pressure that is less than the osmotic pressure of the initial permeate, a final permeate outlet on the opposite side of the nanofiltration membrane relative to the input of initial permeate, and a final retentate outlet on the same side of the membrane as the input of initial permeate, wherein a final permeate that passes through the nanofiltration membrane exits the final separation stage through the final permeate outlet, and a final retentate that does not pass through the nanofiltration membrane exits the final separation stage through the final retentate outlet, and the final retentate includes lithium sulfate and a precipitate of at least one of the salts other than lithium sulfate;
• and
• a filtration stage connected to the initial retentate outlet and the final retentate outlet, the filtration stage including a filter that removes the precipitated salts from the initial retentate and the final retentate to obtain a product solution having a higher concentration of dissolved lithium sulfate than the feed brine solution, the product solution being obtained solely from the retentates of the initial and final separation stages, and the product solution having a content of lithium sulfate in a range of 8 to 10 wt. %.