Help : White wine tastes like soap

Not too much you can do, I'm afraid. From what you write, I suspect that the sodium bicarbonate has left sodium carbonate behind, which is washing soda, i.e. soap, and that's what you're tasting now in your wine.

You might try adding some sort of acid (wine acid blend would seem the weapon of choice here) to neutralize the sodcarb remnants, but you would have to do that judiciously and not go overboard with it. That said, you will always be left with sodium, no matter what you do. Too much sodium does not improve any beverage.

If you are able to take a pH reading, you might try to acidify the wine (blending the acid in well) until you're just below 7 and then give it time for the reaction to complete.

My own approach would be to run it through a still and make some sort of brandy out of it. :-)

Possibly, but you need patience it seems/ It is probably because of the baking soda that your wine tastes like this. You can't remove the molecules that are responsible for this anymore from your wine.

However, I read that this is readily used, but you need a month or two for the results of this addition to drop out from the wine.

I have made wine already three times from my own homegrown grapes, and I have actually never adjusted my pH, not even measured it. What I do after fermentation is to rack it off the lees into a jar (without much headspace), then let it rest in a cool place for six to seven months (other people wait a year, maybe for red wine). The acid responsible for the acidity of the wine (tannins, cream of tartar) will drop out. This works for me, I have tasty wine.