| 摘要: | 大部分土壤表面帶負電荷對於金屬陽離子具高親和力，但因為有機質含量偏低導致對環境中占有機污染物絕大部分的非離子有機污染物不具吸持特性。傳統利用大型有機陽離子（HDTMA）改質土壤可增加土壤有機質含量並增加其對有機污染物之吸持能力，但所增加之土壤有機質無法同時顯現出對重金屬的親和力。藉此本研究積極研發可同時吸持有機與無機污染物之多重功能吸附劑，以蒙特石為改質基材探討具不同特殊官能基(包括-SH、-S、-NH2、-COOH)之有機改質劑以陽離子交換法及接枝法植入蒙特石層隙，使其同時對有機污染物與無機污染物兼具吸持特性，其中亦選擇胺類改質劑經由質子化的方式降低長烷基鏈的疏水性。分析結果證實改質蒙特石之表面存在胺基、硫醚或硫醇基等官能基，且陽離子改質法比接枝法更能將改質劑插入於蒙特石層隙中亦對重金屬離子有較大親和力。
改質劑的碳鏈長度與非離子有機污染物的親和力有很大的相關性，但前述研究缺點為當蒙特石引入官能基時會增加蒙特石之極性，導致削弱其對非離子有機污染物的親和力，且對無機污染物之吸附僅止於一般常見之重金屬。因此，本研究另以不同碳鏈長度以及具苯環結構之有機改質劑完成層柱狀土壤表面修飾，以利於後續大型團聯共聚物的植入。結果顯示碳鏈長度高達C38之改質劑已成功植入蒙特石中且擴大其層隙間距達50Å以上。層柱狀土壤除擴大土壤層隙外，具較長直碳鏈結構之層柱亦可提供良好的疏水分佈環境。
層柱狀改質蒙特石之主要目的為利於大型團聯共聚物的植入，其中參與聚合的團聯單聚物於特殊條件下其表面官能基可分別呈現正或負電特性而對陰或陽離子產生極高的親和力，最終形成可同時對非離子(BTEX)、陰離子(Cr2O72-)及陽離子重金屬(Cu2+、Zn2+)污染物兼具高吸持(附)特性的蒙特石複合材料。由NMR鑑定確定RAFT聚合法可以成功合成三團聯共聚物，三團聯共聚物改質之蒙特石透過調整反應條件來進行有機與無機污染物吸附，其中甲基丙烯酸二甲胺乙酯(D)單聚物在酸性溶液中可吸附Cr2O72-，研究成果證明在低pH值(pH=3)有最佳的吸附效果且飽和吸附量可達107066 mg/kg，當pH值愈高吸附能力則降低。另外甲基丙烯酸(A) 單聚物亦被證實可於水溶液(pH=6)中吸附Cu2+及Zn2+，其中吸附Cu2+之飽和吸附量達9969 mg/kg，團聯共聚物的甲基丙烯酸甲酯(M) 單聚物則提供BTEX良好的分佈介質，結果顯示改質蒙特石的log Kom明顯大於天然土壤，代表其對有機污染物能提供更有效的分佈介質。本研究成果完成同時對非離子、陰離子及陽離子污染物兼具高吸持特性的蒙特石複合材料已顛覆一般對傳統吸附劑的認知。
;The current remediation technologies are not effective for the simultaneous removal of both organic and inorganic contaminants from the contaminated sites due to their different characteristics. In two decades ago, we had used a high molecular organic compound (HDTMA) to modify soil to enhance the SOM content, which increases the ability of organic compounds partitioning to the soil.
One of the studies highlighted the preparation of adsorbents for both organic and inorganic pollutants by modifying sodium montmorillonite using different functionalized modifiers. The effects of different functional groups, including –SH，–S，–NH2，–COOH, of the modifier on the sorption are discussed. Since the long hydrocarbon chains, the water solubility of modifiers is restricted, the materials are prepared by cation exchanging with alkylammonium ions, and protonated of amine group in alkyl polyamine halide to increases water solubility. In addition, we were exploring the influence of different processing methods, via cation exchange and grafting, on the structure, physical and chemical characteristics and adsorption ability of modified montmorillonites. The adsorption behavior of the modified montmorillonites for both inorganic and organic pollutants was also discussed based on the structural and surface properties. The successful grafting of modifiers onto the interlayer was confirmed by spectral analysis. However, adsorption was mainly controlled not only by surface area but also by the nature and surface charge of the modifiers. Based on the experimental results, the soil modifier significant improved the sorption characteristics and, among two metal ions, Cu2+ showed enhanced adsorption. The uptake phenomenon was influenced by various combined factors such as the nature, surface charge and surface area of the modified soils.
Due to small interlamellar spacing of the hydrophilic layered silicate surface of montmorillonite, the intercalated species are capable of increasing the interlayer spacing as pillars. According to the above principle, we present another method to modify soil using the specific modifier. The modified pillared soil could adsorb both the organic contaminants and the heavy metals simultaneously. The effect of different modifiers with different chain lengths on the d-spacing of montmorillonite was studied and discussed in detail. XRD experiments were carried out and it was found that the modifier with a longer carbon chain comparatively enhanced the interlamellar spacing than that of other modifiers. The influence of HCl, the amount of modifiers and temperature on the interlayer structure was also discussed. In addition, the alkyl chain on the soil surface can be regarded as a partition medium.
Although, quaternary ammonium salt can effectively improve the organic matter content of the soil and recent researches on amine modified soil showed that under certain conditions, they can be used as dual adsorbents for the removal of both organic and inorganic pollutants, but the removal of nonionic organic compounds (NOCs) is not effective. Thus the final study was to propose a new concept to use clay composite materials in which polymers are intercalated into interlayer of clay. Such clay composite can possess positive and negative charges and thus can act as versatile adsorbents for both organic and inorganic pollutants (cation and anion).
Finally, this study chooses a methyl methacylate (M), methacrylic acid (A) and dimethylaminoethyl methacrylate (D) to synthesize triblock polymers. The triblock copolymers successfully synthesized by RAFT polymerization method were confirmed by nuclear magnetic resonance (NMR) spectral analysis. In acidic conditions, the dimethylaminoethyl methacrylate is protonated (positively charged) which can be used for anionic pollutants, and in alkaline solution, methacrylic acid can possess negative charge which can adsorb inorganic heavy metal pollutants. Furthermore, methyl methacylate is considered to greatly enhance the distribution of NOCs in the hydrophobic environment. Not only sorption of different pollutants was carried out using these clay synthesized composite materials, but also the effect of pH and other parameters were studied. A systematic study was carried out in depth in order to understand the mechanism and various factors that can affect the adsorption phenomenon. Uptake of both organic (benzene; toluene; ethylbenzene; and xylene; in brief BTEX) and inorganic (Cu2+, Zn2+ and Cr2O7 2-) pollutants were explored and highlighted in the final study. The observed log Koc values for the distribution of organic pollutants onto clay are significantly high in this study. In all cases the adsorption of Cu2+ was comparatively larger than that of Zn2+. The affinity of modified clay for Cr2O72- is increased owing to the occurrence of pH value decreased. The obtained log Koc and log Kom values of BTEX in this study for modified montmorillonite are comparatively larger than those of unmodified montmorillonite or natural soil. The self-synthesized triblock copolymers were embedded in the pillared layered clays, that displayed enhanced adsorption of both organic and inorganic pollutants and hence it was concluded as a great potential candidate. |
