奈米零價金屬因具有反應迅速以及還原能力強的特性，能有效地去除水中污染物，已被廣泛應用在水污染之整治上。惟金屬在奈米尺寸下，容易造成團聚效應，降低奈米金屬在水中的去除效果。
在本研究中，以聚偏二氟乙烯(PVDF)微濾膜做為奈米零價金屬之載體，藉由聚丙烯酸溶液以交聯方式製備奈米零價金屬之複合膜。所製備兩種奈米零價金屬複合膜分別包含奈米零價鐵之金屬複合膜及奈米零價鐵鎳之雙金屬複合膜，分別在控制不同pH值及不同孔徑之金屬複合膜的條件下，探討其對水中Cr(Ⅵ)之去除效果；並以最佳孔徑之奈米零價金屬複合膜，針對不同方式處理水中Cr(Ⅵ)，觀察其效果差異。同時，探討不同製備方式對水中Cr(Ⅵ)去除效果及pH值變化之影響。
研究結果發現，以含奈米零價鐵鎳之孔徑為0.45μm之雙金屬複合膜(雙金屬含量4.14mg)處理Cr(Ⅵ)(起始濃度為20mg/L)效果最顯著，幾乎可以達到99.7%(90分鐘)，其中鐵鎳雙金屬比例為1：3。
此外，以不同方式處理水中Cr(Ⅵ)可以發現，奈米零價鐵鎳之雙金屬複合膜遠比奈米金屬及PVDF微濾膜效果來的好。在探討不同方式製備奈米零價鐵鎳之雙金屬複合膜時，以延長加熱時間、降低鎳之比例以及減少鎳浸漬時間時，均可增加對水中Cr(Ⅵ)之去除效果。 Zero-valent metal nanoparticles, possessing characterization of fast reaction rate and strong reduction ability have been found to be effective in degrading organic and inorganic aqueous contaminants. However, the aggregation of zero-valent metal nanoparticles can reduce the effective application for in situ decontamination in soil and groundwater.
Zero-valent iron nanoparticle composite PVDF microfiltration membranes (ZVI/PVDF) and bimetallic FeNi alloy nanoparticle composite PVDF microfiltration membranes (Fe0Ni0/PVDF) were synthesized with cross linkage of Polyacrylic Acid (PAA) into hydrophobic polyvinylidene fluoride (PVDF) microfiltration membrane which was used as the supported membrane. Supported membrane pore sizes such as 0.1, 0.22, 0.45, and 0.65μm, aqueous pH values, mass loading of zero-valent nanometals and bimetallic mass ratio were evaluated to realize the influences on the reductive removal of chromium(VI) ion from contaminated aqueous solution. Significant reduction efficiency of chromium(VI) ion reached at almost 99.7% when it was contacted with 0.45μm membrane supported of Fe0Ni0/PVDF (Fe:Ni=1:3) in 90 minutes.
Fe0Ni0/PVDF composite membrane had higher Cr(Ⅵ) removal efficiency than ZVI/PVDF composite membrane did. Different synthesized methods were used to prepare the Fe0/Ni0/PVDF composite membrane. The extension heating time of PAA solution, the reduction of Fe/Ni bimetallic ratio, and the reduction impregnate time of PVDF into Ni solution could enhance the reductive removal of Cr(Ⅵ).
