利用顯色型中孔洞材料進行氨氣吸附及探測之研究

Abstract

氨氣具有惡臭性、刺激性及腐蝕性，主要氨氣排放源包含農業活動與工業製程，此外，台灣高科技產業爲達產品生產的超高空氣品質要求，無塵室作業環境中之氨氣(NH3)問題也備受重視，因此如能有效吸附NH3氣體，並在吸附飽和時顯色，應可有廣泛之工業應用領域。本研究之目的是結合變色染劑及中孔洞分子篩MCM-41進行氨氣吸附，研究中所選擇之變色染劑溴甲酚綠(bromocresol green)是一種偏酸性之大分子有機染劑，其變色範圍在pH 3.8 (橘黃色)到pH 5.4 (藍綠色)；而MCM-41由於其孔洞大小分布範圍狹窄、孔洞體積大、高比表面積、具有良好的吸附容積、表面反應性強及易於改質等優點，故期望利用此複合材料，經氣體吸附達到氨的移除並同時在吸附飽和前能產生顯色效果。研究結果顯示，在複合材料填充量為0.3g且NH3初始濃度1-5 ppm下進行吸附，約20-30秒後材料表面即開始變色。因此藉由顏色改變與NH3濃度之關係，期望未來能開發簡易之氨氣感知器，以進行現場即時偵測，此外，其還可應用在化學濾材去除氨氣上，藉由濾材是否變色，即可了解濾材已達飽和與否，可確實掌握其更換時間。

Ammonia is an odorous gas which commonly exists in the atmosphere due to human, agricultural and industrial activities. And typical online ammonia sensing instruments provide high resolution data but the instrument cost is usually expensive. On the other hand, the low cost ammonia measurement devices such as ammonia sensing probes are limited by their low accuracy of measurement. In this study, we developed the ammonia sensing material by using MCM-41 impregnated with bromocresol green. MCM-41 is one kind of mesoporous molecular sieves. It can be applied to many fields due to well-defined pore shapes, narrow distribution of pore sizes, large pore volumes, high surface area, excellent thermal, hydrothermal, chemical and mechanical stability. And the bromocresol green dye (BG) is commonly used as a pH indicator with colorimetric from pH 3.8 (yellow) to pH 5.4 (blue). The results showed that visible color change was observed within 30 sec of ammonia detection from 1~5ppm NH3 concentration level. Besides, the adsorption of ammonia gas was preceded with adsorption efficiency of over 95%. Thus the adsorbents can provide further application potential as a color indicator for an ammonia adsorber upon saturation.