比較積垢與未積垢薄膜對於藥物及個人保健用品之去除率及通量之影響

Abstract

近年來，薄膜處理技術被廣泛運用在淨水場以去除特定汙染物，如溶解性固體、天然有機物、無機離子及毒性物質。本研究主要以三種PPCP及兩種奈米薄膜作為對象研究奈米薄膜去除PPCP之現象，並藉此找出PPCP及薄膜特性對於效率及去除機制之影響，利用Hermia模式來判斷積垢機制。本研究使用之薄膜機組為平板掃流式，並在不同操作條件下(pH、壓力、掃流速度及積垢物質)觀察薄膜通量衰減情形和出水品質。利用HPLC及TOC分析出流水濃度，並使用SEM及AFM分析薄膜表面。最後使用反應曲面法(responds surface method)根據實驗結果求出本實驗之最佳操作條件。 三種PPCP之去除率和薄膜之MWCO有正相關，NF270之去除率階高於NTR7450，顯示size exclusion在三種PPCP之去除階存在。在高pH值時sulfamethoxazole及triclosan之帶電性由中性便為負電性，因而electrostatic exclusion存在，使得sulfmethoxazole及triclosan之去除率提升。 根據Hermia模式預測，標準阻塞機制對於兩種模之通量衰減無法解釋，積垢物質並未進入到薄膜孔洞內而被吸附於孔內膜壁上，機構形成可能同時存在樹種機制，包括，完全阻塞、中間阻塞及濾餅生成機制。 結果顯示NF270及 NTR7450兩種積垢薄膜會提高acetaminophen之去除率，對於sulfamethoxazole則會使去除率下降，triclosan在NTR7450積垢後去除率會較未積垢之薄膜下降而在NF270積垢與未積垢並無明顯變化。對於acetaminophen之主要去除機制為size exclusion，sulfamethoxazole為size exclusion及electrostatic exclusion而triclosan則包含了三種去除機制。 積垢會改變薄膜表面特性，造成積垢後之薄膜去除效率與未積垢薄膜有所差別(可能上升或下降)。由於實驗中之三種藥物之物化特性不同其去除機制也有所不同，因而造成三種藥物在積垢和未積垢薄膜中去除率變化的差異性。 利用實驗結果及反應曲面應用程式推算結果顯示，在本奈米薄膜處理程序其最佳操作條件為操作壓力在100psi，掃流速度在0.32m/s及進流pH在10時。在此操作條件下，其預估之通量減為5.6%，PPCP之去除效率約為98.5%。

Membrane or pressure-driven processes are used to remove contaminants such as dissolved solids, nature organic matter, inorganic ions, and some other hazardous compounds from water. This research investigated the effects of solute and membrane characteristics on the rejection and flux decline at various pH levels, transmembrane pressure, cross-flow velocity, and at foulant. Filtration was conducted with a cross-flow module using membrane (NF270 and NTR7450) in plate form. The concentration of effluent and membrane properties were determined using instruments such as HPLC, TOC, SEM, and AFM. The optimal operation conditions of NF filtration processes were determined using the response surface method (RSM). There are positive correlations between rejection of target compounds and the MWCO of membrane. The rejection by NF270 was always higher than that by NTR7450 which indicated that size exclusion could be the removal mechanism of the three target compounds. At high pH, both sulfamethoxazole and triclosan are negatively charged, which implies that electrostatic exclusion could be the removal mechanism. Standard blocking was not the main fouling mechanism for both membranes, which indicated that the molecular size of foulant in the feed solution might be larger than that of the membrane pore. Membrane fouling could be brought by the a combination of several fouling mechanisms, i.e, complete blocking, intermediate blocking, and gel layer formation. In the presence of humic acid and calcium ions, the rejection of acetaminophen by both NF270 and NTR7450 membranes was increased whereas opposite results were observed for sulfamethoxazole. The rejection of ticlosan decreased with operation time prior to 6 hrs which could be attributed to adsorption. The fouling layer may modify the surface properties of membrane which leads to different degrees of performance. The difference in the rejection of the three target compounds brought by distinct removal mechanisms can be attributed to their respective physic-chemical properties. The optimum operating condition determined by the RSM was found to be at TMP of 100 psi, cross-flow velocity of 0.32 m/s, and pH 10.0. Under the best operating condition the performance was: 98.5% of rejection and 5.6% of flux decline.