A silverwood tree will start cleaning up a taint biome, and Etherial Blooms will halt the spread of taint up to 8 blocks around them. As for taint/flux produced from infusion crafting that is in a liquid form, I know of no ways to clean that up, doesn't seem to go away over time either.
A silverwood tree with a pure node will turn the biome into a magical forest 4-5 blocks around it, you're right about Etheral Blooms.
Taint/Flux generated from Infusion Crafting and Cauldrons can be removed by simply placing a block on it.
Taint caused by infusion/cauldrons seems to just eat any block you try to place on it, or at the very least keep you from placing it. the only way I have been able to eliminate it is by pouring lava over it, but that leads to another host of issues in itself.