I can only speak for Ahkanazi Jewish tradition, not for Sephardic, but according to the “official” rules the issue with biscuits is not the baking soda, it is the flour. Flour is considered to have leavened if it spends more than a cumulative 18 minutes wet from the time of harvest until it is baked.
That said, many Jewish people would probably balk at the idea of eating biscuits on passover unless they are made with matzah meal instead of flour, even if they follow the 18 minutes rule. For me it would feel like violating the spirit of the holiday even if it does not violate the law explicitly.
I can only speak for Ahkanazi Jewish tradition, not for Sephardic, but according to the “official” rules the issue with biscuits is not the baking soda, it is the flour. Flour is considered to have leavened if it spends more than a cumulative 18 minutes wet from the time of harvest until it is baked. That said, many Jewish people would probably balk at the idea of eating biscuits on passover unless they are made with matzah meal instead of flour, even if they follow the 18 minutes rule. For me it would feel like violating the spirit of the holiday even if it does not violate the law explicitly.