以酵素清洗超濾薄膜過濾腐植酸之不可逆積垢與分析

Abstract

本研究目的利用生物性的清洗試劑，藉以降低清洗積垢後所產生的廢液問題、減少對薄膜的傷害，透過不同透膜壓差(100和135 kPa)和過濾時間(24和12 hr)，薄膜過濾腐植酸溶液後，利用酵素探討對薄膜上產生的不可逆積垢去除效率，並以阻力串聯模式分析阻力與去除效率之相關性。 從α- amylase和lipase的去除效率僅侷限於1~10%，主要因為薄膜積垢後，在薄膜表面上形成一致密的膠體層，導致孔隙率降低，使酵素易截留於此膠體層表面，因而去除效率不佳。相較於傳統的NaOH和citric acid有37%~63%和6 %~19 %的去除率，雖然酵素無較佳去除率，但NaOH和citric acid第一階段清洗完後，後續再以酵素清洗，均可提升去除效率，尤其是NaOH+α- amylase可至91%，意味著α- amylase和lipase可去除NaOH和citric acid無法去除的不可逆積垢；另一方面，FEG-SEM和AFM可觀察出NaOH和citric acid清洗後可使積垢表面膠體層孔隙率和粗糙度變大，增加α- amylase和lipase水解面積並提升其去除效率。 利用FTIR分析清洗前後，積垢物官能基的改變，反應出不可逆積垢與多醣類物質有直接相關性，經α- amylase清洗後，此多醣類物質的IR吸收強度明顯降低，推測不可逆積垢中有類似澱粉類物質(starch-like)潛在性。

The utilization of enzymatic detergents for membrane fouling control presents several advantages such as minimum membrane damage, easier neutralization of cleaning effluents and their biodegradability was evaluated using different enzyme. The removal of irreversible fouling, due to ultrafiltration of humic acid. T he fouled membrane surfaces appears smoother than corresponding clean membrane sufaces. NaOH and citric acid were much more efficient than enzyme solution. The combination of alkaline, acid and enzyme however, was more effective than NaOH and citric acid alone. This implies that enzyme can remove the component that cannot be removed or degraded by NaOH or citric acid. The highest cleaning efficiency was observed with the combination of NaOH and α-amylase. FEG-SEM and AFM analyses elucidate that the lower roughness of fouled membrane than clean membrane, which implied increasing cleaning efficiency of α-amylase and lipase. FTIR spectra analysis were applied to see difference between the original membrane and the fouling membrane.When irreversible fouling resistance achieve one critical value, α- amylase was more cleaning efficiency than NaOH. The removal organic matter of irreversible fouling were difference with NaOH and α- amylase.