Titanium and Tantalum are quite nonreactive, so using 'safe' acids, such as diluted acetic acid won't make any difference. That's why using strong acids such as (sometimes has to be hot ) sulfuric acid will do it. If you are looking for not having to work with sulfuric acid, you could always use hydrogen iodide: that is even stronger than sulfuric acid...
It's documented here that:
Tantalum appear not to be attacked by many acids at room temperature
but does dissolve in hydrofluoric acid, $\ce{HF}$, or oleum (a solution of
sulfur trioxide, $\ce{SO3}$, in sulfuric acid, $\ce{H2SO4}$, also known as
fuming sulfuric acid).
Reaction of tantalum with water
Tantalum does not react with water under normal conditions. The
surface of tantalum metal is protected by a thin oxide layer.
Then I read for titanium (Source):
Reaction of titanium with water
Titanium metal is coated with an oxide layer that usually renders it
inactive. However, titanium will react with steam form the
dioxide, titanium(IV) oxide, $\ce{TiO2}$, and hydrogen, $\ce{H2}$.
$\ce{Ti(s) + 2H2O(g) → TiO2(s) + 2H2(g)}$
So Tantalum doesn't react with steam so you might be able to use steam for that separation as seen as $\ce{TiO2}$ is white and tantalum not.
Source : http://caldersgr9science.wikispaces.com/73+Tantalum
