環境資源報告成果查詢系統

水環境介質中奈米微粒轉換及宿命研究

中文摘要   環境奈米科技之研究與應用正在蓬勃發展,然而奈米材料進入環境介質後,可能之性質變化、流布與宿命,甚至對於生態、環境與人體健康之可能影響,已逐漸引起國內外各界之關注。尤其於水體環境中,因各項水質化學因子之影響,人造奈米懸浮液體材料奈米微粒於水體環境中物化性質之轉變與其可能之流布與宿命仍待持續之研究與評估。目前人造奈米懸浮性材料顆粒之量測技術尚無一統一之標準方法,尤其在水介質中奈米懸浮性材料型態、粒徑與物化性質會因水質化學特性而有所轉變,所以建構一測量水介質中奈米懸浮性顆粒之檢測技術,並研討水質化學對於奈米懸浮性顆粒之粒徑與物化性質變化,將有助於分析奈米懸浮性材料之環境宿命,並可藉由此研究方法的建置探討人造懸浮性奈米顆粒之生態風險。   本研究的主要目的在於藉由之前所建立水介質中分析商用奈米粉體與自製之懸浮良好奈米顆粒之量測技術,在本年度將新開發結合多層次奈米微粒篩分裝置,建立實際環境水體中奈米懸浮液體奈米微粒之分析技術,並與國際上分析水介質中人造懸浮性奈米材料之慣用技術相比較。由於水體環境中水質參數將影響人造懸浮性奈米顆粒在其中之粒徑大小與物化性質變化,因此本研究將進行探討水介質中商用懸浮性奈米材料物化特性及粒徑分佈隨這些水質因子之轉變,以明確了解水質化學對於商用懸浮性奈米顆粒在水體之宿命,並可藉由此研究方法的建置探討奈米微粒之生態風險。   本研究選定的奈米微粒為商用氧化鋅(ZnO)與二氧化鈦(TiO2)奈米懸浮液體材料,奈米氧化鋅為一種重要的半導體材料,在感測器、太陽能電池、光電設備等方面有廣泛的應用,也是本計劃指定之奈米材料;奈米二氧化鈦是一廣泛使用的光觸媒材料,已有多種商品化之產品。並有許多文獻研究指出此兩奈米材料之毒性,更值得我們關心其宿命。延續所建立之動態光散射技術(Dynamic light scattering),進行水介質中奈米懸浮液體材料奈米微粒量測之實驗方法,結合一奈米微粒篩分裝置,新開發實際環境水體介質中奈米懸浮液體奈米微粒之分析方法,建立分析環境水溶液介質中奈米微粒之最佳分析條件與分析方法。針對商用ZnO與TiO2奈米懸浮液體材料,在不同的水質參數包括奈米微粒濃度、溶液溫度、酸鹼度、鹽類與其濃度、腐植物質與其濃度下,探討水介質中商用懸浮性奈米材料物化特性及粒徑分佈隨這些水質因子之轉變。   於實際環境水體中,設計良好界定的封閉系統中進行實驗,探討實際環境水體中水質參數影響商用奈米懸浮液體材料中奈米微粒之變化,藉由水質化學與表面化學等中膠體化學的基本理論,討論實際環境水體中商用奈米懸浮液體材料奈米微粒的轉變與穩定性。藉由水質化學與表面化學中DLVO理論或修正DLVO理論,計算驗證水質參數對懸浮奈米溶液奈米顆粒之模式,討論水體環境中奈米粒子的轉變、穩定性,並由腐植物質與奈米微粒之實驗,以及環境水樣之結果,探討環境系統中是否存在奈米自組裝現象。完成水體環境中奈米微粒之檢驗方法建立與探討水質參數對於奈米微粒在水介質中的轉換及宿命研究。   建立在水介質中商用人造懸浮性奈米材料顆粒之量測技術與研討在水介質中奈米材料顆粒之轉變,相當符合目前國際上環境奈米科技之重點研究方向,預計所研究之結果將具有下列創新與環境意涵:(1)研發分析水體環境中商用人造懸浮性奈米顆粒之檢測技術、(2)標準化檢測分析條件,以利分析結果可統一比較、(3)具有不同水質情境下,水體環境中商用人造懸浮性奈米顆粒之轉變特性、(4)了解環境介質與人造懸浮性奈米材料之作用關係、以及(5)建立商用人造懸浮性奈米材料在水體環境之預估模式。
中文關鍵字 奈米懸浮液,聚集,酸鹼值,陽離子,陰離子

基本資訊

專案計畫編號 EPA-99-U1U1-02-102 經費年度 099 計畫經費 1820 千元
專案開始日期 2010/04/15 專案結束日期 2010/12/31 專案主持人 施養信
主辦單位 永續發展室 承辦人 蘇鈺珊 執行單位 國立台灣大學

成果下載

類型 檔名 檔案大小 說明
期末報告 期末報告定稿.pdf 6MB

nanoparticle suspension, aggregation, pH, cations, anions

英文摘要 After the studies about aggregation of commercial nanopowders in 2008 and self-synthsized suspension nanoparticles in 2009, two commercial nanoparticle suspensions were chosen in this year (2010). The two commercial metal oxide nanoparticle suspensions, TiO2 and ZnO, in a variety of aqueous conditions were investigated. These two commercial suspensions, TiO2 and ZnO, were identified as nanoscale particles by a transmission electron microscopy (TEM) and dynamic light scattering (DLS). At 25℃, the particle concentration of nanoparticles between 20 mg/L and 30 g/L did not significantly affect the particle size of these commercial nanoscale TiO2 (pH 3~4) and ZnO (pH 8~9) suspensions. The temperature in the range of 15~35℃ also did not significantly affect the stability of 1000 ppm TiO2 (pH 3~4) and ZnO (pH 8~9). When the pH value closes to pHpzc of TiO2 nanoparticles (pH 6.5) at 25℃, the obvious sedimentation behaviors were found for 1000 ppm TiO2 nanoparticle suspension. Far from the pHpzc of TiO2 nanoparticles, the TiO2 nanoparticles keep stable in nanoscale. ZnO nanoparticles (1000 ppm) keep stable in the nanoscale under alkaline condition (pH 8~12) at 25℃. Under neutral and acid conditions, the ZnO nanoparticles aggregated quickly, which could result from its dissolved zinc species. The ionic composition and strength can strongly affect the aggregation of nanoscale materials in the aquatic environment. For the 1000 ppm commercial TiO2 suspensions (pH 3~4) at 25℃, the particle size increased more quickly in a higher concentration of salts. The critical coagulation concentration (CCC) values for nanoscale TiO2 particles with positive surface were estimated as 290 meq/L and 2.3 meq/L for Cl- and SO42-, respectively. The increase in ionic strength resulted in compression of the electrical double layer (EDL), and therefore a decrease in the EDL repulsive energy such that the flocculation can be predicted. Multivalent ions could form bridges with nanoscale particles or neutralize their surface charges to induce a quick aggregation. Furthermore, these CCC values are higher than those of TiO2 nanoparticle powders in previous study (2008), indicating the strong stability of the commercial TiO2 nanoparticles. Besides, these CCC values are similar to those of manufacturing TiO¬2 suspensions in previous study (2009), indicating the similar behavior of two kinds of modified-TiO2 nanoparticles. The CCC value for 1000 ppm commercial ZnO suspension particles with negative surface (pH 8~9) was estimated as 40 meq/L for Ca2+, which is much higher than ZnO nanoparticle powder and commercial TiO2 suspensions. In addition, the ZnO nanoparticles were not aggregated obviously in the presence of NaCl. The results indicated that the divalent cation than monovalent is more easily to neutralize the surface charge of particles and increase aggregation in the same ion strength. This phenomenon is consistent with Schulze-Hardy rule. The interaction energies of nanoparticles in the presence of electrolytes were also evaluated by using DLVO (Derjaguin-Landau-Verwey-Overbeek) theory. Besides, compared with manufacturing ZnO suspensions, the CCC values of commercial ZnO suspensions are obviously higher. We need to pay attention on these highly stable commercial nanoparticle suspensions. In the presence of a low humic acid (HA) concentration, the 1000 ppm commercial TiO2 suspension particles can keep stable several days at pH 3~4 and 25℃. When Suwannee river humic acid (SRHA) concentration was higher than 30 mg/L, TiO2 nanoparticles aggregated. Humic acid could enhance the aggregation process possibly through the cross-linking of nanoparticles with SRHA in aqueous solution. For the co-effect of ions and HA, the CCC values decreased to 100 meq/L and 1.8 meq/L for Cl- and SO42-, respectively, as compared to those values in the absence of humic acid. Because unchanged surface potentials were observed under these CCC values, ions seem to enhance the aggregation effect in the presence of SRHA molecules. 1000 ppm ZnO suspension particles still maintained stable as HA concentration in the range of 0~50 mg/L at pH 8~9 and 25℃. The commercial ZnO suspension particles did not affect by NaCl in the presence of humic acid. In the presence of HA, the CCC value of ZnO nanoparticles slightly reduced to 30 meq/L for Ca2+, which is very high as compared to nanoparticle powders. Consequently, these commercial suspension nanoparticles could have hazardous potential in aquatic environment due to their high stability. In this study, the DLS technology is also cooperated with sample pretreatment process including filtration and centrifugation to develop a process for the analysis of nanoparticles in the aquatic environment. The centrifugation process was efficient to removal the interference effect of large particles on DLS analysis. In the artifical environmental waters, centrifugation is also more suitable than filtration to be used as a pretreatment process of DLS measurement for nanoparticles. The combination of centrifugation process into the DLS analysis and confirmation by SEM or TEM is suggested to detect nanoparticles in the environment. The cooperation of other instruments is recommended for the precise analysis of nanomaterials in the environment in near future.
英文關鍵字 nanoparticle suspension, aggregation, pH, cations, anions