Adsorption rate versus agitation speed and initial metal ions concentration: To determine
the effect of agitation speed on the rate of metal ion adsorption, three agitation speeds (100, 200 and 270 RPM), at 20°C with 1 g of Bentonite clay having a particle diameter of 0.25 mm was placed in 50 mL of metal ions (chromium or lead ions) solution with an initial concentration of 200 ppm.
In these experimental runs, the initial concentration of chromium and lead ions was kept constant before adding the Bentonite clay in the metal (chromium or lead) solution in the bottles. After starting the experiment, samples of metal (chromium or lead ions) solutions were collected at various time intervals during 3 h period, filtrated and the concentration was determined by atomic absorption spectroscopy. The data was plotted as the concentration versus the time as shown in Fig. 2 and 3.
The experiments were also carried at different initial concentrations of lead ion (154, 216,
307 ppm) to determine the effect of varying initial concentrations on adsorption rate at 20°C.