Is it obligatory to take back a young wife or a post-menopausal wife during a period of purity in which her husband had intercourse with her?

The Shaykh : A third man came to us asking, saying that he has a young wife or a wife who does not menstruate; a young wife who does not menstruate, or an older wife who does not menstruate for one reason or another. He had intercourse with her and then divorced her before performing the ritual bath for major ritual impurity. He divorced her before performing the ritual bath for major ritual impurity. What do we tell him? Is the divorce valid or not?
The divorce is valid, because she falls under one of the three categories mentioned previously.