I can see some real technical difficulties with this if I understand this correctly, or not.
If regaining argon purity is your problem I would think that you need a unit that reduces gaseous temperature to a point that individual gases and gaseous impurities, can be seperated through the liquid state. This is how the gases are 'manufactured' in the first place. My thought would be this would be prohibitively expensive since the energy required to do this, and the cost of the equipment, would be in excess of the savings gained.
If the gas is assumed to remain as pure coming out as going in the all you need do is recirculate and maybe attach an analyzer to verify its purity to an acceptable level. If your process is clean and controlled perhaps you could achieve several uses of the same gas which would require minimal investment.