dc.description.abstract | In general, soil posseses negatively charged and having a high affinity for metal ions only. Soil has no capacity of partitioning for nonionic organic pollutants because the nonionic organic pollutants are carried out with partitioning by soil organic matter. If the soil does not contain a high content of organic matters, the partition capacity of soil would be low. However, the inorganic and organic pollutants usually coexist presenting time in the environment. In general, the traditional methods of modification of soils usually improve the content of soil organic matter but often loss the capacity of adsorption for ionic pollutants.
In this study, we have synthesized modified-montmorillonites using Na-montmorillonites and surfactants with different alkyl chain number, chain length and functional groups. Such modification, makes Na-montmorillonites possible for simultaneous adsorption / sorption of inorganic and organic pollutants. The most widely used technique for studying intercalated materials in the silicate galleries is X-ray diffraction (XRD), which provides information on the layered structure and the basal spacing. The results showed that for the modified clay the basal spacing increased from 15 to ~ 18-53Å, and the interlamellar space is defendent on the carbon chains of the modifiers and also its dosage. Nitrogen adsorption-desorption device can confirm the amount of modifier resulted in an average pore size than the unmodified sample. Fourier infrared spectroscopy also informed that the modified clay surface contains the specific functional groups (e.g. alkyl and Carboxyl functional) and modification relatively changed upon increasing the alkyl carbon chain of modifiers. Detected organic carbon content by dichromate reflux method have proven the successful modification. Sorption of BTEX by modified soil indiacated that distribution of BTEX and water solubility of organic adsorbate is disproportional to its partition coefficient. Also, the distribution and behavior of BTEX by hydrophobic modification of soil is affected by the environment conditions and structure. The organic modifiers improved the distribution of nonionic organic compounds better is shown in this study. Since, the modified clay is bonded on surface of soil by ion exchange, parts of adsorption sites are occupied and the modified agent can not provide a lot of functional groups and then cause for less adsorption capacity than pristine clay. But, the purpose to prepare the modified clay that can absorb both heavy metal and BTEX at the same time has been obtained in this study.
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