We use web authentication/captive portal for our Employee and Guest WLANs.
How long does an unauthorized device stay connected to the AP if it hasn't successfully authenticated via web?
Is there a setting to automatically disconnect a device if it hasn't authenticated after, say five minutes?
"Inactivity Timeout" , the last option under Advanced-options for WLAN should help to disconnect the idle device after certain minutes . You can select the number in minutes. ( 1 - 500 ) . Hope this helps.