The Chizkuni to Bereishis 3:1 says that the serpent ate from the eitz hadaas, this would explain why he have gained "cunning" and also the ability to talk by ingesting some of that tree.
On regard the taking away the serpent power of speech, the Torah DOES suggests this by saying:
“...and dust shalt thou eat all the days of thy life.” (3:14)
The Oznaim LaTorah, says that "dust consumption" is sign of silence. The use of expression "all the days of thy life" would impact more this silence, i.e, the complete absence of speech. A paralellism in Eicha 3:28-29 alludes to this idea:
Let him sit alone and keep silence / because He hath laid it upon
Let him put his mouth in the dust / if so be there may be hope.