Fig. 7 plots the kinetics of Sr2+ uptake by BT1 after three runs of
adsorption and desorption experiments using a second order
rate model; the adsorption is from the depletion of initial Sr2+ in
solution ([Sr2+]i = 9.56 ppm) using 5 g BT1 at pH 11, and the
desorption is based on Sr2+ load of previous run on BT1 releasing
into solution at pH 3.