The study of the adsorption kinetics of these metallic ions shows that the particle size
has a significant influence on the metal uptake rate for copper; but that it has only a
slight influence on the adsorption rate of zinc and mercury in the range studied. Arsenic
adsorption exhibited an interesting behaviour which depends strongly on the pH of the
solution; the uptake increased at short adsorption times and then decreased at long
times. The analysis of kinetic models showed that the pseudo-second-order adsorption
mechanism is predominant, and the overall rate of the metallic ion adsorption process is
therefore controlled by adsorption reactions and not by mass transfer for the range of
particle sizes examined in this study.