Organic solvent purification method and purification system

A purification method for separating and purifying an organic solvent from a liquid mixture of the organic solvent and water, the organic solvent having a boiling point of more than 100° C. at 1 atm, the purification method comprising:

• a first ion exchange step of passing the liquid mixture into a first ion exchange resin;
• a dehydration step of selectively separating water component from the liquid mixture by supplying the liquid mixture discharged from the first ion exchange step to a pervaporation device having a pervaporation membrane;
• an evaporation step of supplying the organic solvent recovered from a concentration side of the pervaporation membrane to an evaporator to vaporize, and obtaining the organic solvent which has been purified;
• and
• a second ion exchange step of treating a portion of liquid which contains the organic solvent that flows into a branch point at a first position, and
• wherein liquid discharged from the second ion exchange step is returned to a second position,
• wherein the first position is:
• located between the concentration side of the pervaporation membrane and an inlet of the evaporator,
• located between an outlet of the first ion exchange step and an inlet of the pervaporation device, and prior to the second position, and/or
• at a position at which the organic solvent discharged from the evaporation step flows, and
• wherein the second position is located between the outlet of the first ion exchange step and an inlet of the dehydration step.