Half-life equation for 2nd order kinetics
Roughly speaking, half-life is not a thing at all for the second order (or any order other than first, for that matter).

What would they do after finding the number of half-lives? Raise 2 to that power? Too bad, because that only works for the exponential decay, which is the solution of the first-order kinetics and no other order. Really, what if the number of half-lives equals 2? After spending the first half-life, we now have a different half-life ahead of us, because it is concentration dependent, and the concentration has changed.

Following your link, we see the same statement, except they don't put enough emphasis on it, as to my taste:


  For this reason, the concept of half-life for a second-order reaction is far less useful.