Your choice (aqueous phase) is

• 4-Methoxybenzoic acid* reacted with sodium bicarbonate to form the salt*, sodium 4-methoxybenzoate*.

• Keep the aqueous solution (the top layer) containing the sodium 4-methoxybenzoate.
  Save it to recover (isolate) the 4-methoxybenzoic acid.

Continue to separate the mixture.