An Adsorption Experiment Utilizing Bentonite, a Green and Inexpensive Clay

Although there have been numerous published experiments dealing with adsorption from solutions, those involving the adsorption of metal ions are not numerous. Clays are widely used as adsorbents, and bentonite is a widely available and inexpensive clay. In this report, several aspects of the adsorption of Cu2+ by bentonite are described. Only simple equipment and procedures are involved making such studies accessible to students in lower level laboratory courses. The effects of amount of clay, temperature, and time are described. The results show that adsorption is an endothermic process and that for a given amount of clay the adsorption process follows a rate law that is first-order in Cu2+ concentration. Several extensions of the work are suggested in order to make the adsorption of Cu2+ or other metal ions by bentonite suitable for study by more advanced students.