利用SDS與rhamnolipid修飾之層狀雙氫氧化物(LDH)移除水中多環芳香烴化合物(PAHs)

Abstract

多環芳香烴碳氫化合物(PAHs)具疏水性，屬於致癌物質，大量工業廢水排放導致水中PAHs濃度上升，造成環境嚴重衝擊。因此如何將PAHs從水中移除已成非常重要的課題。 本研究利用共沉澱方法合成Mg2Al-(NO3-) LDH (2:1LDH)，再以離子交換方式將化學界面活性sodium dodecyl sulfate (SDS) 及生物界面活性劑 rhamnolipid (RL)修飾2:1LDH合成SDS-LDH及RL-LDH作為移除水中Naphthalene (NaP)、Acenaphthylene (AcPy)以及Acenaphthene (AcP)等三種PAHs之吸附劑。等溫吸附實驗結果顯示，相同重量的RL-LDH對於NaP的吸附能力較SDS-LDH高，主要是因為RL-LDH 層間間距較大，有機碳含量高，因此對於NaP有較多的分配位置，故對於水中NaP的移除效率較大。動力吸附實驗結果顯示，SDS-LDH以及RL-LDH移除水中NaP經反應15分鐘後即可達到平衡，並較適合以Elovich方程式來描述。溫度效應結果顯示，SDS-LDH以及RL-LDH對於NaP的移除量會隨著溫度增加而降低。當改變初始pH以及離子強度對於SDS-LDH以及RL-LDH對於NaP的移除量影響是較小的。PAHs間物種的影響結果顯示，RL-LDH對於疏水性較高的AcPy有較大的吸持含量，其次為AcP，最低者為NaP。回收再利用試驗結果得知，RL-LDH重複利用數可達五次以上，且仍有75 %的移除效率 。經由生物界面活性劑(RL)與化學界面活性劑(SDS)修飾後之LDH皆能對水中PAHs有良好的移除效果，並且以RL-LDH對於PAHs具有更大的移除效果。RL 相較於 SDS 毒性低，同時RL-LDH並具有可重複利用性，因此對水中PAHs的移除，RL-LDH是一種具有潛力及對環境友善的吸附劑。

Sorption is a common treatment for removing pollutants from natural environments. The sorption of polycyclic aromatic hydrocarbons (PAHs) by layered double hydroxide (LDHs) and surfactant modified LDHs had been investigated. Mg2-Al (NO3) LDH has been synthesized by co-precipitation method with interlayer nitrate and the Mg/Al molar ratio was 2. Chemical synthesis surfactant sodium dodecyl sulfate (SDS) and biosurfactant rhamnolipid (RL) modified LDHs, SDS-LDH and RL-LDH, were synthesized by ion exchange method. The experimental results indicated that more organic carbon content and larger interlayer spacing lead RL-LDH sorb more naphthalene (NaP) than SDS-LDH. The fitted sorption data revealed that the Elovich model could be best described the sorption kinetics, respectively. The temperature has significantly influenced sorption of NaP on SDS-LDH and RL-LDH : lower temperature leads to more sorption capacity. The sorption process was almost unaffected by NaP initial pH and ionic strength. Additionally, acenaphthene (AcP) and acenaphthylene (AcPy) could be sorbed more than NaP by RL-LDH cause of the higher octanol-water partition coefficient.The desorption and reuse experiments revealed that RL-LDH could be used more than 5 times and the removal efficiency is higher than 75% Consequently, RL-LDH has low toxicity and reuse ability make it be a potential adsorbent for organic pollutant removal from aqueous solution.