studied the retention of Cr(III)
by bentonite at pH 3 with an initial concentration of
5 · 103 mol L1. They found that the equilibrium is also
reached after 30 min.
We can deduce from these experiments that the equilibrium
times of adsorption are achieved faster for chromium. The
equilibrium adsorption of cadmium is slower to reach but
did not exceed 210 min in all the analyzed cases. Thus, given
these results and for convenience reasons, the contact times
were set at night (960 min) for the adsorption experiments
on the effects of pH and initial concentrations of Cr III solutions
and Cd II