水溶性無機微粒的一個自動監測技術

Abstract

本研究結合平板式濕式固氣分離器(Parallel Plate Wet Denuder, PPWD)、濕式靜電集塵器(Wet Electrostatic Precipitator, WEP)技術及離子層析儀(Ion Chromatogrphy, IC)組成一套即時監測大氣環境中水溶性無機酸鹼氣體-微粒採樣分析系統(PPWD-WEP)，以改善傳統手動採樣器採樣時間過長、耗費人力及在運送與分析過程中易發生人為污染等缺點，並提升採樣分析的方便性及準確性。 本研究利用多孔玻璃板及一個銅片分別作為PPWD-WEP之吸收表面及收集電極，收集板表面經噴砂處理後塗敷TiO2奈米微粒以提高表面親水性，水溶性氣膠藉著由上而下流動的均勻水膜收集，並以IC進行吸收液的樣本濃度分析。本研究利用氣體產生器產生NH3及HF氣體作為測試氣體，再利用未施加高電壓的PPWD-WEP及吸收瓶同時進行採集監測，實驗結果發現，兩種採樣器所監測到的氣體濃度相對誤差在4.4 %以內。 本研究亦利用恆定輸出霧化器(TSI, Model 3076)產生多徑的NaCl及(NH4)2SO4微粒，再利用施加高電壓之PPWD-WEP及濾紙匣同時進行採樣實驗。微粒進入PPWD-WEP後藉由電場作用而往兩側極板移動，再以由上而下流動的吸收液收集；濾紙採集到之微粒則以超純水萃取，再將溶液樣本打入IC進行分析，進而獲得微粒中離子濃度。實驗結果顯示，當鈉離子及氯離子產生的濃度範圍分別為0.93~36.46μg/m3與0.83~48.8 μg/m3時，PPWD-WEP與濾紙採樣器所採集之可溶性離子濃度誤差在 10.7 %內。當硫酸根與銨根的濃度範圍為1.25~16.2 μg/m3及0.55~6.58 μg/m3時，PPWD-WEP與濾紙採樣器所採集之可溶性離子濃度誤差介於± 5~20 %間。此實驗結果顯示PPWD-WEP系統可有效監測NaCl及(NH4)2SO4微粒。

In this study a real-time monitoring system, PPWD-WEP, which consists of parallel plate wet denuder (PPWD), wet electrostatic precipitator (WEP) and ion chromatography (IC) for soluble inorganic acid/basic air and particles sampling, was developed. The present system can solve the problems in traditional sampler such as time consuming and artificial generated during samples transportation and analysis. It is expected that the convenience and accuracy of air sampling and analysis can be enhanced by the present system. In the PPWD-WEP, porous glass plate and copper plate which are coated with TiO2 nanoparticles to enhance the hydrophilicity are used as the acting surfaces and the collection electrode, respectively. The soluble inorganic acid/basic air and particles are collected by a uniform water film flowing downward along the active and collection electrodes surface. Ion chromatography is used to analyze liquid samples. NH3 and HF gases generated by a gas generator were used as the test gas and sampled by PPWD-WEP system without applying to high voltage and impinger at the same time. The gas concentrations sampled by PPWD-WEP system agree well with those sampled by impinge with deviation lower than 4.4%. The PPWD-WEP system applied to high voltage and filter sampler were further used to sampled NaCl and (NH4)2SO4 particles simultaneously, which were produced by atomizer (TSI, Model 3076) in this study. In the PPWD-WEP system, particles migrated to the collection electrodes because of the electrostatic force and then collected by scrubbing liquid. Particles collected by filters were extracted by used deionized water. Ion Chromatograph was used to analyze the samples and determined the ion concentration in the particles. The results show that when the sodium ion and chloride concentrations were 0.93-36.46μg/m3 and 0.83-48.8 μg/m3, respectively, the concentrations measured by the present system agree well with those sampled by filter samplers with deviation lower than □10.7 %. When sulfate and ammonium concentrations were 1.25-16.2 μg/m3 and 0.55-6.58 μg/m3, respectively, the concentrations sampled by the present system are in good agreement with those sampled by filter samplers with a deviation lower than □5~20%. This result suggested that the present PPWD-WEP system can be used to monitor inorganic acid /basic gases and NaCl and (NH4)2SO4 particles accurately.