This picture says "all natural", it doesn't say aluminum free. The bag from Bob's Red Mill I have in my fridge says aluminum free. Search amazon for aluminum free, there are aluminum free brands. Maybe Bob's Red Mill has stopped selling aluminum free, I bought mine a few years ago.
As far as I know baking soda is baking soda. It never contains aluminum. Baking powder contains aluminum. Therein lies the confusion. If you need baking soda, buy whichever is there and/or most inexpensive.