A process for extracting lithium ions from geothermal water within a binary geothermal power plant, comprising the steps A) Pumping geothermal water with a temperature of 120 °C - 180 °C from a geothermal reservoir via a production well into a heat exchanger under a pressure of 15 - 35 bar; B) Passing the geothermal water from step A) through the heat exchanger; C) Feeding 100% of the geothermal water from step B) into at least one nanofiltration module; D) Nanofiltration of the geothermal water supplied to the at least one nanofiltration module in step C) for the separation of alkali metal ions and other monovalent ions from multivalent ions under a pressure of 15 - 35 bar and a temperature of 50 °C - 80 °C and direct reinjection of the residual solution enriched in multivalent ions into the geothermal reservoir via at least one reinjection well; E) Transferring the permeate of the nanofiltration from step D) to a precipitation unit (5a or 5b) for the precipitation of the remaining divalent alkaline earth ions; F) Precipitation of the remaining divalent alkaline earth ions in the precipitation unit (5a or 5b) from the permeate of the nanofiltration of step D); G) Transporting the permeate depleted of divalent ions from step F) by a circulation pump (6a or 6b) to a second heat exchanger (7a or 7b); H) Heating the permeate from step G) in the second heat exchanger (7a or 7b) to 65 - 85 °C; I) Membrane distillation of the permeate heated in step H) under normal pressure and a temperature of 65 °C - 85 °C; J) Separation of lithium ions concentrated in step I) in a separation unit by precipitation, ion exchange, absorption processes, liquid-liquid extraction or electrodialysis. A) Pumping geothermal water with a temperature of 120 °C - 180 °C from a geothermal reservoir via a production well into a heat exchanger under a pressure of 15 - 35 bar; B) Passing the geothermal water from step A) through the heat exchanger; C) Feeding 100% of the geothermal water from step B) into at least one nanofiltration module; D) Nanofiltration of the geothermal water supplied to the at least one nanofiltration module in step C) for the separation of alkali metal ions and other monovalent ions from multivalent ions under a pressure of 15 - 35 bar and a temperature of 50 °C - 80 °C and direct reinjection of the residual solution enriched in multivalent ions into the geothermal reservoir via at least one reinjection well; E) Transferring the permeate of the nanofiltration from step D) to a precipitation unit (5a or 5b) for the precipitation of the remaining divalent alkaline earth ions; F) Precipitation of the remaining divalent alkaline earth ions in the precipitation unit (5a or 5b) from the permeate of the nanofiltration of step D); G) Transporting the permeate depleted of divalent ions from step F) by a circulation pump (6a or 6b) to a second heat exchanger (7a or 7b); H) Heating the permeate from step G) in the second heat exchanger (7a or 7b) to 65 - 85 °C; I) Membrane distillation of the permeate heated in step H) under normal pressure and a temperature of 65 °C - 85 °C; J) Separation of lithium ions concentrated in step I) in a separation unit by precipitation, ion exchange, absorption processes, liquid-liquid extraction or electrodialysis.