Emission of metals under colloidal phase in wastes leachates : ICP-AES and SEM-EDX analysis
Résumé
European Union is aiming to promote sustainable long-term progressive reduction of contaminant discharges to the environment. Potentially toxic elements and hydrophobic organic contaminants inputs and transfer of metals and organic contaminants to the environment occur from various sources: domestic, industrial and urban runoff. Different types of waste are extensively produced all over the word by industrial and domestic activities, but after disposal, their fate in the environment is poorly known, especially when pollutant release occurs under colloidal form. So, a general recommendation to protect the water and soil environment is that a biodegradability and fate assessment should be required for these various wastes, in order to determine subsequent implications for the environment. The complexity and variability in the composition of these wastes involve to study a large panel of them, since speciation of pollutants considerably depends on chemical composition, pH, Eh, ionic strength. Speciation, mobility and toxicity of these pollutants could be quite predictable in the aqueous or particulate phases, whereas their fate is unsure when they exist under colloidal form. Thus, it is of great interest to evaluate the composition of metals under colloidal form present in waste leachates in order to study the phase they are bound to, and finally predict their behavior and fate. In this context, 5 different wastes were studied: Bauxite residue, coastal marine sediments, sludge of wastewater treatment plant, crushed wastes and ashes from household incineration. After leaching, filtrations and measurement of element concentrations in the microfiltrate and ultrafiltrate fractions by Inductive Coupled Plasma Atomic Emission Spectroscopy (ICP-AES), we used Scanning Electron Microscopy- Energy Dispersive X-ray spectroscopy (SEM-EDX) to specifically detect the phases bound to metals of colloidal size. Some answers dealing with emission of pollutants from wastes were given.