鈣離子對UF薄膜有機積垢之影響

Abstract

薄膜處理程序無法廣泛應用之限制乃因薄膜積垢問題，積垢產生使得薄膜通量衰減導致於清洗次數增多而減少薄膜使用壽命，有機物為薄膜處理程序中主要積垢物質，而水體中有機物與鈣離子對於薄膜積垢之共同效應為本研究之重點。 本研究使用人工配置腐植酸水樣進行薄膜過濾實驗，並配置鈣離子水樣，在不同鈣離子存在條件中觀察薄膜積垢的現象，於研究結果發現，腐植酸與鈣離子對於30 kDa之UF薄膜而言，薄膜積垢之機制以分子大小減少至10~50 kDa進而直接阻塞薄膜孔洞為主，而對於不同的薄膜而言，鈣離子、腐植酸與薄膜之間的關係，因薄膜官能基與表面物理特性而有所不同，對於表面容易吸附鈣離子的PSF薄膜而言，鈣離子先行累積於薄膜表面會造成後續有機物在薄膜上的累積，但短時程過濾不影響其通量衰減情形；若以PVDF薄膜而言，先行過濾含鈣離子水樣卻有助於其排除腐植酸之能力，此乃鈣離子累積孔洞內而導致其疏水性減弱所致。

Organic matters are major foulants during ultrafiltration and limit the development of membrane. The influence of humic acid on the organic fouling of ultrafiltration was studied as a function of calcium ions. Molecular weight and microscopy were used to study the characterization of membrane and organic foulants. Flux decline of filtration in the presence calcium ions was very severe. The saturated bond was decreased by calcium ions bridging with humic acids, decreasing the contact angle. Thus, the membrane, after filtration with humic acid and calcium ions, was hydrophilic. UF membrane flux declines seriously with the absence of calcium ions in a humic acid solution, attributing to membrane pore blocking. Humic acid and calcium ions, due to complex formation, reduce molecular weight distribution. Molecular weight determines a membranes pore size. The molecular weight of complex is similar to membrane pore size. The molecular weight of humic acid is smaller than 50kDa and causes serious membrane fouling for a UF membrane (30kDa). In the results of SEM, the pore sizes were smaller after filtration. There were significant amounts of foulants on the membrane surface in the presence of calcium ions. This research focuses on the humic acid curled by calcium ions that lead to immediate flux decline soon.