利用奈米碳管吸附水中壬基苯酚之研究

Abstract

本研究主要針對有內分泌干擾物質特性(EDCs)的壬基苯酚(4-nonylphenol)為研究對象。壬基苯酚(4-n-nonylphenol)其來源最主要為界面活性劑、乳化劑及一般塑膠生產製造過程的添加劑等，且因其在環境中溶解度低且不易生物分解，具環境荷爾蒙的特性、持久性以致於對環境和水中生物造成危害。目前台灣傳統之污水處理設備並無法有效去除水中之壬基苯酚(4-nonylphenol)，因此本研究利用四種不同型態之吸附劑，包括粉末狀活性碳、單壁奈米碳管、多碳奈米碳管、束狀奈米碳管吸附水中壬基苯酚(nonylphenol)探討其吸附效率。 利用四種不同比表面積、孔徑吸附劑針對水中壬基苯酚(4-nonylphenol)進行吸附實驗，吸附劑之吸附量除了跟吸附質之基本特性有關係外，吸附劑本身表比面積及孔徑大小也會影響吸附劑之吸附量。若吸附劑擁有較小的孔徑時當吸附質經由質傳效應進入孔徑後較不容易在恆溫振盪的過程中被沖洗出來。在動力吸附實驗結果顯示，四種吸附劑達最高飽和吸附率為70~80%，以四種吸附劑模擬擬一階及擬二階動力吸附模式時發現，四種吸附劑皆符合擬二階動力動力吸附模式，且四種吸附劑其R2值皆大於0.95。將四種吸附劑之等溫吸附實驗結果模擬Langmuir等溫吸附模式、Freundlich 等溫吸附模式及BET等溫吸附模式結果發現四種吸附劑皆較符合Freundlich isotherm，多壁奈米碳管碳較其他三者吸附劑在濃度較高的平衡狀態下比在濃度低的環境時有較高的吸附量，而活性碳粉末和多壁奈米碳管在低濃度的平衡狀況下比其他二者吸附劑有較高吸附量。

The study focused on the adsorption mechanism of 4-nonylphenol in water with carbon nanotubes. The primary sources of nonylphenol are surfactant, emulsifying agent, and additive of plastic product, etc. Nonylophenol which belongs to endocrine disrupting compounds (EDCs) has many characteristics such as low solubility, persistent and difficulty to be decomposed by biodegradation. Therefore, it might cause the toxicity in ecosystems and aquatic organisms. 4-Nonylphenol could not be removed completely via traditional wastewater treatment processes, but it could be discharged directly into aquatic environments. In this study, the adsorption efficiency for nonylphenol from water samples was estimated by four adsorbents, including powder activated carbon (PAC), single-wall carbon nanotubs (SWCNT), mult-wall carbon nanotubs (MWCNT), and bundle carbon nanotubs (BCNT). The effect of the parameters, such as specific surface area and pore size of adsorbent as well as properties of adsorbate on adsorption capacity were studied. 4-nonylphenol which was adsorbed in smaller porous adsorbate was hard to be washed out during constant-temperature vibrating process. In kinetic adsorption experiments, the highest saturated adsorption rate of the four adsorbents is 70~80 %. The adsorptions behavior of 4-nonylphenol onto PAC, SWCNT, MWCNT and BCNT coincided with the pseudo second-order model (R2= 0.95). In this study the Langmuir, Freundlich and BET isotherms were simulated. The adsorption isotherms of 4-nonylphenol of the selected adsorbates fitted the Freundlich isotherm fairly well. From Freundlich isotherm model, MWCNT had the highest adsorption capacity among the selected adsorbates in the higher equilibrium concentration. In constant PAC and MWCNT had higher adsorption capacity in the lower equilibrium concentration.