CaptivePortal and allowed domains

[ccorsani]

Dear all, I have successfully installed pfsense + captiveportal connected to my freeradius server.

I work in a pubblic library, so my guests on pubblic wifi network can surf internet with our autentication
db. They can surf  with daily traffic limitation based on my db.

But I have a problem: my guests must access to our network - and this is easy because I have a fixed
ip class - and some othe "pubblic" network like, for example .edu .gov.it .sbn.it

Is there a way to manage this situation?

Sorry for my english.
Regards.