奈米矽片銀改質濾材控制室內生物氣膠之研究

Abstract

生物氣膠為室內空氣品質控制所關注的項目之一，於室內HVAC系統結合過濾裝置之方式目前普遍的生物氣膠控制技術。本研究嘗試利用奈米矽片銀高抗菌性且低生物毒性之特性，將其批覆於濾材上形成一抗菌濾材，藉此使生物氣膠能迅速失活。四種濾材(未改質、銀濃度12.6 ppm、31.5 ppm與63 ppm之奈米矽片銀改質濾材)連續過濾測試結果，經改質後濾材因孔隙率下降，提高E.coli氣膠被攔截下來的機率，過濾效率在RH=30%條件提升13.7∼19.7%，在RH=70%條件則提升14∼19.9%，yeast則濾材改質前後過濾效率並無明顯差別。不同奈米矽片銀改質濃度濾材(銀濃度12.6 ppm、31.5 ppm與63 ppm)過濾效率統計分析結果並無顯著差異。過濾後濾材上微生物存活情形，結果顯示濾材經奈米矽片銀改質濃度越高，針對生物氣膠的抗菌表現也就越佳。 HVAC模擬系統過濾測試，在RH=30%環境條件下，E.coli與yeast於HVAC模擬系統裝設濾材後，艙室中存活氣膠量無明顯降低跡象，可能為裝設濾材後產生過濾壓差，使HVAC系統回流率不佳，導致生物氣膠難以經由HVAC過濾裝置所去除。在RH=70%條件下，裝設濾材後艙室內E.coli衰減率增加1%∼10.8%，yeast衰減率提升17.7%∼31%，未改質濾材與奈米矽片銀改質濾材結果差異不大。經HVAC系統過濾後，E.coli於濾材上的存活數量十分稀少，yeast於未改質濾材存活數量遠高於奈米矽片銀改質濾材，表示改質濾材具有抗菌效能。 最後針對四處公共場所(教室、圖書館、餐飲區、醫院候診區)進行實地測試，奈米矽片銀改質濾材細菌和真菌過濾效率分別為98.9%與98.7%以上。同時針對教室環境過濾後微生物存活測試，未改質濾材放置12小時後，真、細菌存活率分別為290%與76.5%，而改質濾材在12小時放置後真、細菌存活率則分別僅有50%與25%，顯示實場應用下奈米矽片銀改質濾材具有良好過濾和抗菌效能。

Bioaerosols is one of the concerning topics associated with indoor air quality control. The combination of indoor HVAC system with filtration device is the most common bioaerosol control technology. In order to inactivate bioaerosols, clay-supported silver nanohybrids (AgNP/Clay) could be immobilized on the filter to form an antimicrobial filter by utilizing its characteristics of high antimicrobial activity and low cytotoxicity. According to the results of continuous flow filtration test for four types of filers(un-modified filter, AgNP/Clay modified filter with 12.6ppm, 31.5ppm, and 63ppm Ag), the filter efficiency for E.coli was increased 13.7~19.9% and 14.0~19.9% due to the decreased in porosity at RH=30% and RH=70%, respectively. However, there was no significant difference between un-modified and modified filter for yeast could be observed. According to the results of statistical analysis of modified filters with different AgNP/Clay concentrations, the P-value was greater than 0.05, which indicated that there was no significant difference between filtration efficiency. By observing the survival of microorganism on filter, the results showed that modified filter with higher concentration of AgNP/Clay had better antimicrobial performance. In HVAC filter testing simulation system, both the survival number of E.coli and yeast had no significant decrease after the installation of filter under environmental condition of RH=30%. Bioaerosols had difficulty to remove from HVAC system due to the differential pressure produced from the installation of filter, which result in deficiency of recirculation rate of HVAC system. Under environmental condition of RH=70%, the reduction rate of E.coli and yeast increased 1.0~10.8% and 17.7~31.0%, respectively. However, there were no remarkable difference between un-modified and AgNP/Clay modified filter. It could be observed that E.coli were rare to survived on filter after the filtration of HVAC system while survival rate of yeast on un-modified filter was much higher than AgNP/Clay modified filter. It indicates that filter modified with AgNP/Clay has antimicrobial effect. Based on the test of on-site bioaersols at four public locations (classroom, library, dining hall, and out-patient hall), the Ag/NP/Clay modified filter had filtration efficiencies of 98.9% and 98.7% for bacteria and fungi, respectively. Furthermore, according to the results of survival examination of microorganism on filter in classroom with the duration of 12 hours, the survival rates for bacteria and fungi were 290% and 76.5% for un-modified filter while 50% and 25% for AgNP/Clay modified filter, respectively. It could be summarized that AgNP/Clay modified filter has a positive filtration and antimicrobial performance with on-site application.