SYSTEMS AND METHODS OF HIGH-PRESSURE NANOFILTRATION TO REDUCE MAGNESIUM CONCENTRATION WHILE INCREASING LITHIUM CONCENTRATION IN HIGHLY SALINE BRINES BEFORE DIRECT LITHIUM EXTRACTION

1 . A method for processing a highly saline brine input containing monovalent and multivalent ions, the method comprising:

feeding the highly saline brine input into a first pass of a nanofiltration membrane at a high pressure effective to produce a permeate having (1) a concentration of multivalent cations that is lower than the highly saline brine input and (2) a concentration of monovalent cations that is higher than the highly saline brine input, the nanofiltration membrane having a permeate brine stream and a retentate brine stream,

wherein feeding the highly saline brine input into the first pass of the nanofiltration membrane includes:

passing monovalent anions in the highly saline input brine stream through the nanofiltration membrane into the permeate;

pulling monovalent cations in the highly saline input brine stream through the nanofiltration membrane in response to monovalent anions passing through the nanofiltration membrane to maintain electrical neutrality, thereby concentrating monovalent cations in the permeate; and

concentrating multivalent cations in the retentate brine stream.

2 . The method of claim 1 , where one of the ions concentrated in the permeate is lithium.

3 . The method of claim 2 , where the lithium containing permeate is introduced to a direct lithium extraction process.

4 . The method of claim 1 , where ruthenium or cesium is concentrated in the permeate stream.

5 . The method of claim 1 , further comprising feeding the permeate to a second pass of high-pressure nanofiltration to further reduce the concentration of multivalent cations in the permeate.

6 . A membrane system for softening brines while concentrating monovalent cations, the system comprising:

a) a high-pressure nanofiltration device that operates at pressures above nominal 40 bar standard nanofiltration pressure;

b) a high salinity input brine stream containing monovalent cations, high levels of multivalent cations, and high levels of monovalent anions, where a total osmotic pressure of the high salinity input brine stream is above about 100 bar, an osmotic pressure of magnesium chloride and calcium chloride together is above about 60 bar, and monovalent anions account for about 90% or more of the total anions;

c) a high-pressure source above about 50 bar applied to the input brine; and

d) a permeate brine stream;

wherein:

monovalent anions in the pressurized input brine stream pass through the nanofiltration membrane,

monovalent anions passing through the filter pull monovalent cations through the nanofiltration membrane to maintain electrical neutrality,

monovalent cations concentrate in the permeate brine stream to a higher level than the monovalent cation concentration in the input brine stream, and

multivalent cations are substantially blocked from entering the permeate.

7 . The membrane system of claim 6 , wherein one of the monovalent cations concentrated in the permeate is lithium.

8 . The membrane system of claim 6 , wherein one of the monovalent cations is ruthenium or cesium.

9 . The membrane system of claim 6 , wherein the monovalent anions are primarily chloride ions.

10 . The membrane system of claim 6 , wherein the multivalent cations includes magnesium and/or calcium.

11 . A high-pressure nanofiltration device configured to receive an input of a brine solution under an applied pressure of above about 50 bar and that produces a higher concentration of monovalent cations on a permeate side of the nanofiltration device compared to the brine solution on a feed side of the nanofiltration device when the input of the brine solution includes a high salinity brine having a high level of divalent cations including at least one of magnesium chloride and/or calcium chloride, and a high level of monovalent anions where a total osmotic pressure of the high salinity brine is above about 100 bar, an osmotic pressure of magnesium chloride and calcium chloride together is above about 60 bar, and monovalent anions account for about 90% or more of the total anions of the high salinity brine, wherein, when the high salinity brine is passed through the nanofiltration device, monovalent anions in the high salinity brine pass through the nanofiltration device and pull monovalent cations through the nanofiltration device to the permeate side of the nanofiltration device to maintain electrical neutrality, thereby concentrating monovalent cations on the permeate side of the nanofiltration device, and wherein divalent cations in the high salinity brine are inhibited from passing through the nanofiltration device, leading to lower concentrations of divalent cations in the permeate.

12 . The high-pressure nanofiltration device of claim 11 , wherein one of the monovalent cations concentrated in the permeate is lithium.

13 . The high-pressure nanofiltration device of claim 11 , wherein the monovalent anions are primarily chloride ions.

14 . The high-pressure nanofiltration device of claim 11 , wherein the multivalent cations includes magnesium and/or calcium.

15 . A lithium concentration system, comprising:

a high-pressure nanofiltration system having at least one nanofiltration membrane at a pressure of at least about 50 bar;

a high salinity brine feed stream containing lithium and high concentrations of multivalent cations, such as calcium and/or magnesium ions, where a total osmotic pressure of the high salinity brine feed stream is above about 100 bar, an osmotic pressure of magnesium chloride and calcium chloride together is above about 60 bar, and monovalent anions account for about 90% or more of the total anions in the high salinity brine feed stream; and

a permeate brine stream,

wherein the lithium concentration system simultaneously or nearly simultaneously increases lithium concentration and reduces magnesium and/or calcium concentration of the permeate compared to that of the high salinity brine feed stream, wherein monovalent anions in the high salinity brine stream pass through the at least one nanofiltration membrane and pull lithium cations through the at least one nanofiltration membrane and into the permeate brine stream to maintain electrical neutrality, thereby concentrating lithium cations in the permeate brine stream while the magnesium and/or calcium ion do not readily pass through the nanofiltration membrane into the permeate brine stream.

16 . The system of claim 15 , wherein the permeate containing lithium is passed through a direct lithium extractor to sequester the lithium from the permeate stream.

17 - 27 . (canceled)