Improved desalination by zinc oxide nanorod induced electric field enhancement in capacitive deionization of brackish water Karthik Laxman a,b , Myo Tay Zar Myint a , Rashid Khan c , Tasneem Pervez c , Joydeep Dutta a, ⁎ a Chair in Nanotechnology, Water Research Center, Sultan Qaboos University, PO Box 33, Al-Khoudh, Muscat, 123, Oman b Department of Electrical and Computer Engineering, College of Engineering, Sultan Qaboos University, Al-Khoudh, Muscat, 123, Oman c Department of Mechanical and Industrial Engineering, College of Engineering, Sultan Qaboos University, Al-Khoudh, Muscat, 123, Oman HIGHLIGHTS • Theoretical study of increase in capaci- tance with metal oxide (ZnO) semicon- ductor • Facile growth of ZnO nanorods arrays on CDI electrodes as proof of principle • Demonstration of the enhancement in ACC capacitance • Marked reduction in power consump- tion and improvement in charge effi- ciency • 30% higher specific salt adsorption ca- pacity (mg/g) was achieved. GRAPHICAL ABSTRACT abstract article info Article history: Received 1 October 2014 Received in revised form 1 December 2014 Accepted 18 December 2014 Available online xxxx Keywords: Electric field Capacitive deionization Zinc oxide Activated carbon cloth Finite element analysis Ion adsorption in capacitive deionization is a function of the electric field strength present at the electrode sur- face. We show enhancement in the electric field strength by coating activated carbon cloth (ACC) electrodes with zinc oxide (ZnO) nanorods, where the effective field was shown to vary with respect to the length, diameter and proximity of the coated ZnO nanorods. Deionization of a 17 mM NaCl solution in a single pass experiment using the composite electrodes showed a desalination efficiency of 35%, a 40% improvement as compared to plain ACC electrodes. The composite electrodes also desalinated at a charge efficiency of 78% with a salt uptake of 7.7 mg/g of the electrode. An enhancement in the ion adsorption rate led to a 30% reduction in the energy con- sumption per mole of salt removed for the desalination process. A theoretical model showing further enhance- ment in the desalination efficiency by reducing the diameter of the rods is also discussed. © 2014 Elsevier B.V. All rights reserved. 1. Introduction In recent years, extensive extraction of groundwater has led to seawa- ter intrusion especially in the arid areas, making the fast depleting fresh- water sources brackish and unsuitable for consumption. The use of traditional desalting methods like reverse osmosis (RO) or multi stage Desalination 359 (2015) 64–70 ⁎ Corresponding author. E-mail addresses: dutta@squ.edu.om, nanosqu@gmail.com (J. Dutta). http://dx.doi.org/10.1016/j.desal.2014.12.029 0011-9164/© 2014 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Desalination journal homepage: www.elsevier.com/locate/desal