Clay minerals used in sanitary landfills for the retention of organic and inorganic pollutants

Samples from a waste operating facility in western Greece were collected in order to determine the composition of the clay minerals present and assess their efficacy in organic and inorganic pollutants retention. For this purpose a number of analytical techniques were employed. 1H NMR revealed that some of the organic components which are present in the samples are aliphatics, polysaccharides, alcohols, esters, Cl-halogens, sulphides, amines, peptide/protein groups, amide and aromatics which are produced in the landfill as a result of several complex phenomena involving solubilization, hydrolyzation and anaerobic biological processes. SEM-EDS analyses showed the presence of chlorine and sulphur in apatite crystals, and of chlorine, sulphur and phosphorus in clay minerals suggesting the interaction of these minerals with leachate. Physicochemical characterization of the leachate produced in the landfill indicates a transition of the landfill from acidogenic to methanogenic phase with a subsequent decrease of the Chemical Oxygen Demand (COD). Furthermore, the increase in the ammonium-nitrogen and the phosphorus content suggest that any leachate leakage poses a serious threat for the environment. NMR analyses showed that a number of aliphatic fractions are preferentially adsorbed on chlorite than on montmorillonite, while those aliphatic moieties that are water soluble are preferentially adsorbed on montmorillonite. The different clay mineralogy of the material used in the landfill, smectite (montmorillonite) rich and chlorite/vermiculite rich material, facilitated the adsorption of different organic compounds, which is significant for the retention of pollutants. Aromatics are not accessible to rainwater and therefore hardly migrate. The aliphatic chains that are water accessible can be released to the environment through natural leaching by rainwater and therefore supervision of the landfill is considered essential.