Is this item able to remove airborne? To be more specific, during Yasuo's ult, can this item or Mercurial Scimitar dismiss the effect of Yasuo's ult?
From the wiki-
The active does not cancel or remove Airborne directly, but allows wielders to use mobility spells and Flash to overrule the effect.
So, used in conjunction with Flash, or a similar spell, you can remove the effects of airborne. This works not only with yasuo's knock up, but also with malphite and others who also have knock up abilities.
From what I understand about how knock ups work (from listening to casters of professional games) there are two parts to a knock up; the initial knock up which works similar to a knock back, and a secondary stun that immediately follows and lasts until the animation of your character falling to the ground completes. The qss will remove this secondary stun allowing you to issue movement commands again, but only movement spells like dashes or blinks break the falling animation and allow you to move again.