By plotting ln Ce versus 1/T (figure not shown) for different
amounts of TCP, DHx values were measured from the slope and
intercept. From Fig. 7, it was found that the heat of adsorption was
negative (DHx = 56.23 kJ/mol), indicating the exothermic nature
of adsorption. The adsorption enthalpies are found to decrease
with increasing TCP loading on the adsorbent, as a result of the
surface heterogeneity of the adsorbent [43