下水污泥中4-壬酚之SFE萃取程序建立與Fenton處理程序可行性評估

Abstract

本研究主要目的為建立超臨界流萃取（supercritical fluid extraction, SFE）技術，目標物為污泥中4-nonlyphenol （4-NP），同時探討利用Fenton處理程序去除污泥中4-NP之可行性，4-NP為非離子界面活性劑王基苯酚聚乙氧基醇類（nonylphenol polyethoxylates, NPnEO）於厭氧生物處理時主要代謝產物，其具有類似雌性生物中雌性激素（estrogen）之結構，進入雄性生物體後會導致雄性生物具有雌性生物之特微。 SFE主要利用二氧化碳為流體，而戊烷（pentane）為收集溶劑，萃取步驟建立主要由三個步驟組成，第一步驟的針對無基質影響之石英砂萃取進行4-NP標準品添加，探討之萃取參數分別為萃取壓力、萃取溫度、萃取流速、靜態萃取時間與動態萃取時間，目的是在瞭解4-NP於二氧化碳流體之溶解度；第二步驟是利用無4-NP之污泥進行4-NP標準品添加，主要探討於基質干擾下所需進行之參數變化，分別為污泥量、4-NP含量、污泥含水率、修正劑添加種類與所需動態萃取時間；第三步驟主要進行實際含在4-NP之厭氧污泥萃取，探討參數為污泥含水率、修正劑添加影響與所需動態萃取時間，同時利用索氏萃取法（Soxhlet exraction method）進行比較。最佳萃取參數如下：污泥量0.2 g、萃取壓力97 bar、萃取溫度40°C、流體流速3.0 mL/min、靜態萃取時間2 min、動態萃取時間30 min、修正劑種類methanol（0.5 mL）。利用SFE與索氏萃取法萃取迪化污水處理廠厭氧污泥時，污泥中4-NP含量分別為243.89與266.98 mg/kg，相對標準偏差分別為0.86與2.62%。 Fenton處理程序處理迪化厭氧污泥（TS 1.7%），所探討之參數為初始氧化劑（H2O2）添加量、催化劑（Fe2+）添加量、污泥pH值、溶氧與反應時間影響。最佳參數設定值如下：初始H2O2添加量5,000 mg/L、初始Fe2+添加量500 mg/L、污泥初始pH值3、反應過程持續曝氧（500 mL/min）、反應時間4小時。經Fenton氧化程序後，污泥細胞未被破壞，污泥中4-NP去除率為83.68%，上層液可作為好氧生物之碳源，H2O2消耗量為185.5 mole/mole 4-NP，處理成本為$190/ton-sludge（dry weight）。

The main objective of this study is to develop the supercritical fluid extraction method. The target is the 4-nonylphenol (4-NP) in sludge. In the same time, we also discuss the feasibility of the Fenton method to treat the 4-NP in sludge. Nonylphenol polyethoxylates (NPnEO) are a major class nonionic surfactant in the world. Under anaerobic condition, NPnEO ultimately biodegrade into 4-NP, which has been shown to be a strongly estrogenic compound. In this study, the CO2 was used as extraction fluid and the pentane as collection solvent. Developments of SFE method contain three procedures. First, we approach to the extractability of standard 4-NP spiking in quartz, which is without matrix effect. The purpose of study was to examm e the solubility of 4-NP in supercritical fluid. The parameters discussed in this procedure are extraction pressure, temperature, flow rate, static extraction time and dynamic extraction. Second, we research on the matrix effect with spiking standard 4-NP in non-4-NP sludge. The parameters discussed in this procedure are sludge weight, concentration of 4-NP, water contain of sludge, modifier type and dynamic extraction time. Third, the real anaerobic sludge from De-Haw sludge treatment plant was extracted by SFE. In this procedure, we examine the water contain and modifier effect in real sludge with SFE. At the end, we compared the extraction efficiency between SFE and Soxhlet extraction method. The optimal extraction conditions are: sludge weight 0.2 g, extraction pressure 97 bar, temperature 40°C, flow rate 3.0 mL/min, static extraction time 2 min, dynamic extraction time 30 min, and methanol (0.5 mL) as modifier. Under these conditions, the concentration of 4-NP in De-Hew STP were 243.89 and 266.98 by SFE and Soxhlet extraction method, respectively and the relative standard deviation were 0.86 and 2.62%. The Fenton oxidation of 4-NP was investigated in sludge of De-Haw STP using a number of process conditions including initial concentrations of H2O2, initial concentrations of Fe2+, initial pH value, concentration of dissolved oxygen, and reaction time. The total solid of sludge was 1.7%. The result suggest that hydroxyl radical may cross the liquid-solid interface under aggressive reaction conditions. The optimal conditions are inital H2O2 concentration of 5,000 mg/L, initial Fe2+concentration of 500 mg/L, initial pH value of 3, dissolved oxygen kept at 35 mg/L with pure oxygen under 500 mL/min, and the reaction time of 4 hours. Under these conditions, the Fenton process did not destroy the bacteris structure. The removal ratio of 4-NP in sludge was 83.68% and the supernatant of sludge was biodegradable. The consumption of H2O2 was 185.5 mole per kg of sludge. Based on these optimization results, the estimated chemical cost for the removal of 243.89 mg/kg 4-NP in sludge was $190/ton (dry weight).