  Noble gas and liquid detectors rely on high chemical purity for successful
operation. While gaseous purification has emerged as a reliable method of
producing high-purity noble fluids, the requirement for large mass flows drives
the development of liquid-phase purification. We constructed a medium-scale
liquid argon (LAr) purification system based on a copper catalyst and 4 A
molecular sieve capable of purifying 1 t of commercial LAr 5.0 to a long
effective triplet lifetime of $\tau_3 \sim 1.3 \mu$s. We further demonstrate
that a quenched effective triplet lifetime of $\tau_3 \sim 1 \mu$s, due to
contamination by air, can be recovered in loop-mode purification to $\tau_3
\sim 1.3 \mu$s after > 20 volume exchanges.
