Removal of Cr(VI) and Cd(II) from aqueous solutions using natural sorbents: volcanic tuff and walnut shells

"Some natural adsorbents were evaluated for the advanced removal of pollutants from aqueous systems. The sorption capacity of walnut shells and volcanic zeolite tuff (from Mirsid-Cluj Romania) to remove the chrome and cadmium at different experimental conditions was studied. The concentration of metal ions in aqueous
systems was evaluated with an inductively coupled plasma mass spectrometer (ICPMS) and an atomic absorption spectrometer. The effect of time, initial concentration of the metals and solution pH on the adsorption at room temperature was studied. pH of the solutions was found to influence the adsorption. Higher Cr(VI) adsorption was observed at lower pH and at low concentration of metal ions. The maximum efficiency
of volcanic tuff in acidic media was 97.12% for chrome and 57.04% for cadmium, respectively, for 0.1 mg/L initial concentration. Moreover, in the same experimental conditions, the maximum efficiency of walnut shells was 61.24% and 44.51% for chrome and cadmium. The two low-cost natural sorbents were efficient for the remove of pollutants from aqueous systems."