Evaluation of the Properties of Diatomaceous Earth in Relation to Their Performance in the Removal of Heavy Metals from Contaminated Effluents

This research analyzes the behavior of different diatomite from Peru, and their potential use for the removal of heavy metals from contaminated effluents. Seven different diatomites were characterized by X-ray diffraction, X-ray fluorescence, scanning electron microscopy, specific surface area, and cation exchange capacity. The absolute removal and the removal efficiency of Cu, Pb, and Zn were assessed by stirring the diatomite in solutions of known concentration of the contaminant, and then analyzing the solutions by atomic absorption spectroscopy (AA). The results were finally correlated with microstructural, chemical, and physicochemical characteristics of the diatomites. It was found that Peruvian diatomites have potential use for decontamination of heavy metals from contaminated effluents even with their low SiO₂ content. Affinity for the studied metals was as follows: Zn > Pb > Cu, with removal percentages as higher than 98% for Zn. No one-to-one relationships were found between the removal efficiency of the studied metals with properties of diatomites. Different parameters must be taken into account at the same time to understand the efficiency of metal removal in polluted waters. In this case, the specific surface area and minor oxides have the greatest effect on the removal efficiency of all metals.