Adsorption and ion exchange of toxic metals by Brazilian clays: clay selection and studies of equilibrium, thermodynamics, and binary ion exchange modeling.

In this study, four Brazilian clays (Bofe, Verde-lodo, commercial Fluidgel, and expanded commercial vermiculite) were evaluated for their adsorptive capacity and removal percentage in relation to different toxic metals (Ni, Cd, Zn, and Cu). The best results were obtained by expanded vermiculite, with cadmium removal reaching values of 95%. The most promising clay was modified by the sodification process, and the metal cadmium was used to evaluate the ion exchange process.

Ion exchange and adsorption of cadmium from aqueous media in sodium-modified expanded vermiculite.

The use of mineral clays as alternative adsorbent has received attention due to their physicochemical characteristics, superficial negative charge, abundance of vermiculite (especially in Brazil), low cost, and chemical composition, which allows the material modification to increase the adsorptive capacity. This manuscript evaluated the use of expanded vermiculite (EV) and sodium-modified vermiculite (VNa) in the adsorption and ion exchange of Cd ions. The sodification was successfully carried out making the ion exchange capacity greater in the modified clay, confirmed by EDX, cation exchange capacity (CEC), DRX, and FTIR analysis.