Brine purification process

A method comprising:

• providing an inlet brine to a vessel including a resin bed having a mixture of at least two cationic exchange resins comprising a first cationic exchange resin comprising an aminophosphonic acid functional group and a second cationic exchange resin comprising an iminodiacetic acid functional group, wherein the inlet brine has a pH of from 2 to 6, a linear liquid velocity from 10 through 100 m/hr, a temperature of from 10 to 90° C., and does not contain a chelating or complexing agent;
• and
• contacting the inlet brine with the mixture of resins to produce a treated brine which contains less aluminum and nickel cations than the inlet brine, wherein prior to contacting the inlet brine with the mixture of the at least two cationic exchange resins the inlet brine has a concentration of from about 300 ppb to about 5 ppm aluminum and from about 3 ppb to about 100 ppb nickel, and wherein the concentration of aluminum and nickel is reduced in the treated brine to less than about 50 ppb aluminum and to less than about 1 ppb nickel after contact with the mixture of the at least two cationic exchange resins.