I've got a couple sources that can probably explain it better than I can, but here's the gist:
- Walk through each file you want to read
- Walk through each line you want to read
- Replace emojis using RegEx
The tricky part seems to be defining the range of characters you want to replace. Most emoji are in a particular block of unicode, but there could be a few outliers particularly if you want to remove kaomoji.
Here's a Stack Overflow link where there's some discussion on what that range will be.
Here's a Python script that shows how you might do it for one file.
Good luck!