Which one is the correct antonym of ''Impound''?

Impound (Verb)
Meaning: Lock up (someone)
Bengali meaning: আইন বা ক্ষমতাবলে দখল করা; আটক/ক্রোক করা।
Example Sentence: Almost forgotten were the poor unfortunates impounded in the prison.
Synonym: Lock-up, Incarcerate, Imprison.
Antonym: emancipate, enfranchise, manumit, unbind, uncage, unchain, unfetter
discharge, free, liberate, release.

Source: Oxford Dictionary, Merriam - Webster Dictionary & Bangla Academy Dictionary.