雙重功能層柱改質黏土之製備與其吸持特性之研究;Preparation and sorption properties of dual functions modified clay

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Title:	雙重功能層柱改質黏土之製備與其吸持特性之研究;Preparation and sorption properties of dual functions modified clay
Authors:	陳誼庭;Chen,Yi-Ting
Contributors:	環境工程研究所
Keywords:	改質黏土;BTEX;層間距;分佈係數;modified clay;BTEX;basal spacing;partition coefficient
Date:	2015-07-08
Issue Date:	2015-09-23 15:17:37 (UTC+8)
Publisher:	國立中央大學
Abstract:	自然環境下，污染物通常為無機及有機物同時存在。一般土壤攜帶負電且對金屬離子具有高親和力，對於有機污染物則礙於有機質含量及土壤水分含量導致吸持性不顯著。傳統土壤改質劑雖可增加土壤有機質含量且提高對有機污染物之吸持能力，但是，對金屬離子並不具親和力。本研究選用五種分別含有不同官能基與不同碳鏈之改質劑，利用陽離子交換法進行人造黏土改質，藉由改質劑的特殊構造及官能基，使得改質土壤可同時吸附/吸持無機與有機污染物。由實驗結果可以發現，改質後的土壤藉由特性分析以了解改質前後之差異，X 光繞射儀的分析可以得知層間距離從15 Å增加至18～53Å，觀察出層間距離的增加與改質劑之碳鏈長度長短及添加量有極大的相關性。利用傅立葉紅外線光譜儀得知，經改質後的黏土表面較未改質者增加烷基碳鏈、羧機等官能基之特徵波峰，且利用重鉻酸鉀迴流法檢測其有機碳含量，證明已成功將黏土改質成功。土壤以有機相分佈之方式吸持BTEX，而改質後黏土提供良好的分佈介質，由吸持結果可觀察出改質劑的結構與疏水性分佈環境會影響BTEX的吸持，且分佈常數（Kd）與有機碳含量有明顯的相關性存在。由於改質黏土經由離子交換法鍵結於土壤表面，使得部分吸附位置被占據且改質劑提供的官能基量不多，造成吸附量較未改質時低，但仍達成本研究之目的，製備出得以同時吸附重金屬及有機污染物（BTEX）的改質黏土。 ;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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