A method for purifying a crude hydrogen feed stream utilizes an adsorbent having a N2/Ar selectivity ranging from 2 to 4 at 30 C. and a Henry's law coefficient for argon ranging from 0.15 to 1.0 mmole/g/atma at 30 C. The composition of crude hydrogen streams from processes in which carbon dioxide is captured necessitates new criteria for adsorbent selection to improve recovery.