Distillation is a technique that can be used to physically separate most homogeneous mixtures based on the difference in the boiling points of the substances involved.
A good example; A flask hold liquids A, B, and C in a homogeneous mixture. The boiling points of A, B, and C are 130 C, 65 C, and 71 C, respectively. The flask is heated to 65C until all of liquid B is filtered out. The remaining mixture is heated to 71C until all of liquid C is filtered out, and only liquid A is left in the flask.
Answer: We do not know. We have not been given the solubility of oxygen in water at a given temperature nor have we been given the Henry's laws constant. We also do not know whether you mean 1 atmosphere of air, or 1 atmosphere of oxygen.