> what actually happens if you mix sulfuric acid with lye
This reaction produces sodium sulfate (a salt) plus water and heat [1]. No idea if this is practical, though. Maybe it’s difficult to source sufficient quantities of some base to neutralize the acid.
There are alkaline wastes. Steelwork slag, power plant fly ash, residues from concrete production, and, the big one, what's left of bauxite after making aluminum. It's probably possible to build a plant to combine them and get some neutral-pH solid out. Still have a heavy metal problem, though.
Florida does not have steel production because it is distant from both coal and iron ore. Same for Aluminum.
It does have portland cement production due to the abundance of limestone near the surface. However, portland cement production is more or less local globally...or it's usually made relatively close to where used. Conversely Florida's phosphate industry is a major source globally. The scales are incomensurate.