I know it is a 2 hour train ride. Would this be ok for a day trip, or does Antwerp need more time, maybe overnight? The rest of my trip, so far, will be in France.
Depends what your interests are. Personally, I did not care for Antwerp, but a few museums have opened since I was there a few years ago - now I might want to see them if I were in town again. Otherwise, I didn't really enjoy the town.
If there are for example museums in Antwerp you want to see that would take priority over everything else you would want to see in France or Belgium, and you could see them in one long day (pick a day when those museums are all open!), then sure, you could do a long day trip.
Well, you better book nonrefundable far in advance. For tomorrow, a return ticket is 277 EUR. Even if you had Eurail Global Pass, it is 20 EUR for seat reservations each way.
Cheaper routes require a change in Brussels, but the local train is quite frequent. Have you seen everything in Paris? I love Antwerp but some would wait for the KMSKA art museum to finish a long closure for renovations. You can see a lot in a day (not Monday) but not everything. Antwerp has more to see than Bruges or Gent.
Is there a particular reason you picked Antwerp? I enjoyed a 1/2 day there when I was in Brussels so I think it's certainly worth a day trip if there is something of interest to you there. However, if you're just picking a city in Belgium to see, I would prefer Ghent to Antwerp. And it's just a few minutes more to Bruges which I would also pick over Antwerp for a day trip.
Since it only takes 2 hours to get there, why not you know better than us what you want to see there.
That ride with one change in trains Paris to Antwerp will take at least #hrs 40 mins.
You take the early TGV from Gare du Nord to Arras, ca 40 mins, then change to Antwerp. That 40 mins ride is a bit pricey.
On the TER train Paris Nord to Arras takes 2hrs or so.