Thermal and chemical modifications of diatomite from Peru and its application in the adsorption of cadmium

A physicochemical characterization was performed on a pennate-type diatomite of lacustrine origin from the southern region of Peru. Diatomite treatments were conducted with the goal of applying this material in adsorption of cadmium, various physical and chemical modifications were carried out, including thermal treatment and modifications with hydrochloric acid, sulfuric acid, and sodium hydroxide. A composite with cellulose and sulfuric acid was also prepared, and finally, a chelating agent EDTA (Ethylenediaminetetraacetic acid) was added. The thermal modifications showed weakly bound hydroxyl groups on the surface, originating from adsorbed water, as well as strongly bound hydroxyl groups from silanol group, as observed in FTIR (Fourier Transform Infrared Spectroscopy) studies. Higher adsorption capacity of cadmium values were obtained in samples modified with 0.5 M NaOH post thermal modification at 700 °C. SEM analysis showed a uniform distribution of cadmium on the diatomite surface. However, modifications with cellulose and sulfuric acid, as well as EDTA, did not significantly increase cadmium adsorption.