It's not able to create more than one wiki per team project at present.
There has been a related user voice, you could vote up and monitor the progress:
Allow creation of multiple Wikis per Team Project
https://developercommunity.visualstudio.com/idea/379600/allow-creation-of-multiple-wikis-per-team-project.html
Alternatively, if I can restrict access to some of the pages in the wiki, that is fine too.
Unfortunately, we do not have independent permission setting based on page level. We could only mange whole wiki permission from Manage Wiki permissions.
You could give a try with Adithya Ramasubramanian [MSFT]'s suggestion in above user voice:
We have the ability to publish code as wiki where a repository can be published into a Wiki. All the markdown files in that repo goes as a Wiki. With this, you can also manage permissions for the Repo which will be inherited into the Wiki.
Try to use branch security to separate different users or groups.