Abd Jalil Siti Nurehan, Wang David K, Yacou Christelle, Motuzas Julius, Smart Simon, Diniz da Costa João C
The University of Queensland, FIM²Lab-Functional Interfacial Materials and Membranes Laboratory, School of Chemical Engineering, Brisbane 4072, Australia.
Faculty of Chemical Engineering, Universiti Teknologi MARA (UiTM), Shah Alam 40450, Malaysia.
Materials (Basel). 2016 Nov 18;9(11):938. doi: 10.3390/ma9110938.
This work investigates the structural formation and analyses of titania membranes (TM) prepared using different vacuum exposure times for molecular weight (MW) cut-off performance and oil/water separation. Titania membranes were synthesized via a sol-gel method and coated on macroporous alumina tubes followed by exposure to a vacuum between 30 and 1200 s and then calcined at 400 °C. X-ray diffraction and nitrogen adsorption analyses showed that the crystallite size and particle size of titania increased as a function of vacuum time. All the TM membranes were mesoporous with an average pore diameter of ~3.6 nm with an anatase crystal morphology. Water, glucose, sucrose, and polyvinylpyrrolidone with 40 and 360 kDa (PVP-40 kDa and PVP-360 kDa) were used as feed solutions for MW cut-off and hexadecane solution for oil filtration investigation. The TM membranes were not able to separate glucose and sucrose, thus indicating the membrane pore sizes are larger than the kinetic diameter of sucrose of 0.9 nm, irrespective of vacuum exposure time. They also showed only moderate rejection (20%) of the smaller PVP-40 kDa, however, all the membranes were able to obtain an excellent rejection of near 100% for the larger PVP-360 kDa molecule. Furthermore, the TM membranes were tested for the separation of oil emulsions with a high concentration of oil (3000 ppm), reaching high oil rejections of more than 90% of oil. In general, the water fluxes increased with the vacuum exposure time indicating a pore structural tailoring effect. It is therefore proposed that a mechanism of pore size tailoring was formed by an interconnected network of Ti-O-Ti nanoparticles with inter-particle voids, which increased as TiO₂ nanoparticle size increased as a function of vacuum exposure time, and thus reduced the water transport resistance through the TM membranes.
本研究考察了使用不同真空暴露时间制备的二氧化钛膜（TM）的结构形成及其截留分子量性能和油水分离性能分析。通过溶胶 - 凝胶法合成二氧化钛膜，并将其涂覆在大孔氧化铝管上，随后在30至1200秒的真空条件下处理，然后在400℃下煅烧。X射线衍射和氮吸附分析表明，二氧化钛的微晶尺寸和颗粒尺寸随真空时间增加而增大。所有的TM膜均为介孔结构，平均孔径约为3.6nm，具有锐钛矿晶体形态。使用水、葡萄糖、蔗糖以及分子量为40和360 kDa的聚乙烯吡咯烷酮（PVP - 40 kDa和PVP - 360 kDa）作为截留分子量的进料溶液，使用十六烷溶液进行油过滤研究。TM膜无法分离葡萄糖和蔗糖，这表明无论真空暴露时间如何，膜孔径均大于蔗糖的动力学直径0.9nm。它们对较小的PVP - 40 kDa也仅表现出中等截留率（20%），然而，所有膜对较大的PVP - 360 kDa分子均能实现近100%的优异截留率。此外，对TM膜进行了高浓度油（3000 ppm）油乳液分离测试，油截留率高达90%以上。一般来说，水通量随真空暴露时间增加，表明存在孔径剪裁效应。因此，提出了一种孔径剪裁机制，该机制由具有颗粒间空隙的Ti - O - Ti纳米颗粒相互连接网络形成，随着TiO₂纳米颗粒尺寸随真空暴露时间增加而增大，颗粒间空隙也增大，并因此降低了水通过TM膜的传输阻力。
