Carbon nanotube-based membranes: Fabrication and application to desalination
Journal of Industrial and Engineering Chemistry 18 (2012) 1551?1559
Chang Hoon Ahna, Youngbin Baekb, Changha Leec, Sang Ouk Kimd, Suhan Kime, Sangho Leef, Seung-Hyun Kimg, Sang Seek Baeh, Jaebeom Parkh, Jeyong Yoonb*
a) Water and Environment Team, Civil Engineering Center, Samsung C&T Corporation, Seoul 137-956, Republic of Korea
b) World Class University (WCU) Program of Chemical Convergence for Energy & Environment (C2E2), School of Chemical and Biological Engineering, College of Engineering, Institute of Chemical Process, Seoul National University (SNU), Seoul 151-742, Republic of Korea
c) School of Urban and Environmental Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan 698-805, Republic of Korea
d) Department of Materials Science and Engineering, KAIST, Daejeon 305-701, Republic of Korea
e) Department of Civil Engineering, Pukyung National University, Busan 609-735, Republic of Korea
f) School of Civil and Environmental Engineering, Kookmin University, Seoul 136-702, Republic of Korea
g) Department of Civil Engineering, Kyungnam University, Changwon 631-701, Republic of Korea
h) Department of Water Supply Technology, Korea Water Resources Corporation (K-water), Daejeon 306-711, Republic of Korea
This review paper compared different methods of fabricating vertically aligned (VA) and mixed composite and carbon nanotube (CNT) membranes in line with water treatment.
The paper presented a brief background of nanofluidics, which governs transport phenomena in CNTs. It also compared the advantages and disadvantages of the two types of CNT membranes. VA-CNTs have high water flux but are difficult to manufacture. On the other hand, the authors recommend the prioritization of mixed-CNTs in research and development because they are simpler to fabricate even though the water flux is not as fast as in VA-CNTs (but still faster than existing membranes).
Despite the advantages obtainable from CNT membranes, the authors also presented different challenges in using them for actual water treatment. A lot of these challenges come from the manufacture of the CNT membranes which involve various hurdles in every stage of its fabrication: from controlling the diameter, to growing of CNTs, to opening the ends, to selection of filler materials, and until functionalization of CNT ends.
The paper also mentioned the major factors to be considered in assessing the desalination potential of CNT membranes. In conjunction with this, it also projected the performance of CNT membranes based on current studies, and specifically expected that desalination using CNT membranes would lower energy consumption because of nanofluidics.
Finally, the paper proposed a prototype for assembling CNT membranes into modules which can be used for actual desalination. The authors mentioned that the module configuration may not differ much from the conventional polymeric RO membranes. They also proposed how a practical and effective configuration could be selected for a desalination process using CNT membranes.
Contribution and application:
From this review paper, it can be deduced that fabricating CNT membranes to be used in desalination of seawater is difficult. A lot of factors should be considered in order to achieve excellent desalination performance: CNT diameter, CNT alignment and assembly, uniformity of nanotubes, vertical growing of CNTs (for tortuosity control), and more. It can be seen that aside from MD simulations, actual experiments and fabrication of CNTs are also important in order to assess the true feasibility of CNT membranes for desalination.
By: Hannah Ebro