CNTs/TiO2 複合奈米材料去除水中磺胺甲基噁唑可行性之研究

磺胺甲基噁唑普遍出現在自然水體中，甚至在國內污水廠之放流水中也被偵測過，如此一來環境中的微生物容易因抗生素之存在而產生抗體基因(ARGs)，進而突變為新異種病毒，若無適合的抗生素抑制，實在威脅人類的生命。奈米碳管與二氧化鈦，為環境奈米技術中廣泛用於處理水中有機物之奈米材料。本研究利用未改質及硝酸氧化法處理之奈米碳管，吸附水中磺胺甲基噁唑(sulfamethoxazole，C10H11N3O3S)。發現奈米碳管經氧化過後可增加純度，減少不定形碳，增加不同的官能基，進而幫助奈米碳管對有機物之吸附與鍵結。硝酸氧化法可大量產生羧酸基，實驗結果顯示兩種碳管對磺胺甲基噁唑之吸附效果，硝酸處理的優於未改質之奈米碳管。利用不同克數奈米碳管找出最適吸附克數為0.01g/100ml。經動力吸附實驗發現，本實驗之奈米碳管吸附磺胺甲基噁唑約需4小時方可達吸附平衡。隨著吸附溶液之pH值降低，奈米碳管對磺胺甲基噁唑之吸附量有增加之趨勢，不同離子強度對於吸附量呈現負面影響，水中陰離子越多會與磺胺甲基噁唑競爭碳管的吸附位址而造成吸附量減少的情形。利用兩種不同波長的紫外光(254nm、365nm)降解磺胺甲基噁唑，加入本研究所製備的奈米複合材料(CNTs/TiO2)進行實驗，但經實驗結果發現此複合材料對磺胺甲基噁唑雖有降解效果，但在波長為254nm的情況下，複合比例為10:1(TiO2/CNTs)的催化速率k=0.2987min-1小於比例為1:0(僅添加TiO2者)之k=0.4588 min-1；而波長為365nm時降解情形也同於前述，初估此複合材料非針對去除此污染物之最佳材料。因此本研究改良上述方法進行兩階段式的實驗，先加入一定比例的奈米碳管對磺胺甲基噁唑達吸附平衡，再加入二氧化鈦進行光降解，於波長254nm下添加比例為10:1(TiO2:CNTs)能達到最快的催化速率(k = 0.4672 min-1)；而在波長365nm下催化速率也大幅提升。DOC去除率方面在光催化3小時後由58.8%提升到64.3%，並無明顯提高磺胺甲基噁唑的礦化率，對照文獻結果發現光降解期間SMT會生成其他結構較複雜且分子量較大的中間產物，而造成礦化程度無法提升。實驗也發現曝入適當的空氣會提升降解sulfamethoxazol的效率。過去研究認為，奈米碳管複合於二氧化鈦上有助其光降解率，但實驗結果顯示，複合的比例對降解效率影響甚大，和文獻相比較後，如何使奈米碳管與二氧化鈦保持一定比例及良好接觸性為關鍵重點。

關鍵字

磺胺甲基噁唑；奈米碳管；二氧化鈦；複合材料；吸附；光催化作用

並列摘要

The sulfamethoxazole appears generally in the natural water body, even in the domestic sewage factory puts in the running water also to detect, then in the environment microorganism easily produces antibiotic resistance genes(ARGs) existence of because of the antibiotic, then sudden change for new heterogeneous virus, if not suitable antibiotic to suppress, threatens humanity's life really. The multi-walled carbon nanotubes (MWCNTs) and the titanium dioxide(TiO2), widely use in for an environment nanotechnology in processing in the water the organic matter nanomaterials. This research use raw(RAW MWCNTs) and modified by nitric acid(H-MWCNTs) to absorb sulfamethoxazole(C10H11N3O3S) in water. The experimental results indicated that H-MWCNTs might increase the purity , the structure and nature of the surface were greatly improved after purification which made CNTs become more functional groups and adsorption sites to adsorption the organic matter from water. Use nitric acid treatment MWCNTs may produce the carboxylic acid base massively, the experimental result indicated that two kind of MWCNTs to adsorption sulfamethoxazol ,the modified MWCNTs superior than the raw MWCNTs .Used different adsorption volume, the optimal grams is 0.01g/100ml. The equilibrium adsorption experiments show that the adsorption sulfamethoxazole approximately needs 4 hours to reach the adsorption equilibrium. Reduces pH of value along with the adsorption solution, the adsorptive capacity of MWCNTs to increases；the different ionic strength causing the negative influence with the adsorptive capacity, in the water the anion too more which with the sulfamethoxazole competition MWCNTs adsorption sites ,so the adsorptive capacity reduces. Using two different UV wavelength (254nm, 365nm) to degrade the sulfamethoxazole, add the CNTs/TiO2 composites to carry on the experiment, although the experimental result indicated that composites not suitable to degeneration sulfamethoxazol, when the wavelength was 254nm, the composites proportion is 10:1(TiO2/CNTs) that reaction rate constant is kmin-1=0.2987 smaller than proportion is 1: 0 (TiO2 only) kmin-1=0.4588; and when the wavelength is 365nm the degeneration situation also like the former, primary estimates this composites to removes sulfamethoxazole by no means best material. Therefore this research improves the above method carries on two-stages experiments, add the certain proportion MWCNTs adsorption sulfamethoxazol to reach the adsorption equilibrium, then add the TiO2 to carry on the light to degrade, under the wavelength 254nm proportion is 10:1(TiO2:CNTs) can achieve the fastest reaction rate constant (kmin-1 = 0.4672); under wavelength 365nm also has the promotion. The DOC degeneration rate aspect photochemical catalysis three hours later from 58.8% promotes to 64.3%, but sulfamethoxazol mineralization not obviously. The comparison literature result discovered that light degeneration period sulfamethoxazol will produce other intermediary product to be complex and the molecular weight is big, so limit the mineralization rate. The experimental results also found that the degeneration efficiency was increased by purging air appropriately. In the past studied consider that a MWCNTs bonded on the TiO2 is positive influence for degeneration rate, but the experimental result showed that the composites proportion to influence degeneration efficiency, compared after the studied, how to maintain good contacting for suitable proportion MWCNTs and TiO2 to is important.