While trying to do some calculations to answer this quesion, I got stuck missing a crucial piece of data: I have no clue how much mass the volcanoes of Io manage to throw out of the gravity well of the Jupiter moon.
It is clear that most of the erupted material falls back to the surface, and the various velocity estimates I have found are quite a bit lower than the escape velocity (~2.56 km/s). For instance "up to 1 km/s".
One number that is possible to find is how much mass the magnetosphere of Jupiter strips of Io. Most are listing that as 1000kg/s (example). That is about as much as the wheat production of Canada.
Are the volcanoes directly throwing away a lot more than that? A lot less? Not at all?