All perfect praise be to Allaah, the Lord of the worlds. I testify that there is none worthy of worship except Allaah and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.
We do not know of any texts indicating that reciting the Surahs you mentioned is a reason for wiping out sins. The utmost we found concerning this issue is a statement from Al-Ghazali in Al-Ihya’ that reads:
"So when one ends his Friday prayer, he should recite Surah Al-Faatihah seven times before uttering any speech and then do the same with Al-Ikhlas and Al-Mu‘awwithatan. Some of the righteous predecessors were reported to have said that whoever does this will be granted protection in the interval between that Friday up until the following one, and that such an action will shield him from Satan."
There is no room for Ijtihaad (independent reasoning) in such issues. Rather, it cannot be proven, except by an authentic text from the Quran or Sunnah, and we have not found any. The fundamental principle in acts of worship is to avoid them if they are not bound by Sharee'ah texts, so that Allaah Almighty is not worshipped, except through what He legislated. Moreover, the Messenger of Allaah, sallallaahu ‘alayhi wa sallam, said: "Whoever introduces into our matter (i.e. Islam) something that does not originally belong to it, will have it rejected." [Al-Bukhari, Muslim and others]
Allaah Knows best.