Capacitive deionization of seawater effected by nano Ag and Ag@C on graphene P.-F. Cai a , C.-J. Su b , W.-T. Chang a , F.-C. Chang c , C.-Y. Peng a , I-W. Sun b , Y.-L. Wei d , C.-J. Jou e , H.Paul Wang a,⇑ a Department of Environmental Engineering, National Cheng Kung University, Tainan 70101, Taiwan b Department of Chemistry, National Cheng-Kung University, Tainan 70101, Taiwan c The Experimental Forest, National Taiwan University, Chu-Shan 55750 Nan-Tou Hsien, Taiwan d Department of Environmental Science and Engineering, Tunghai University, Taichung 407, Taiwan e Department of Safety, Health and Environmental Engineering, National Kaohsiung First University of Science and Technology, Kaohsiung 811, Taiwan article info Article history: Available online xxxx Keywords: Capacitive deionization Graphene Ag@C Seawater Saline water abstract Drinking water shortage has become worse in recent decades. A new capacitive deionization (CDI) method for increasing water supplies through the effective desalination of seawater has been developed. Silver as nano Ag and Ag@C which was prepared by carbonization of the Ag + -b-cyclodextrin complex at 573 K for 30 min can add the antimicrobial function into the CDI process. The Ag@C and Ag nanoparticles dispersed on reduced graphene oxide (Ag@C/rGO and nano Ag/rGO) were used as the CDI electrodes. The nano Ag/rGO and Ag@C/rGO electrodes can reduce the charging resistant, and enhance the electrosorp- tion capability. Better CDI efficiencies with the nano Ag/rGO and Ag@C/rGO electrodes can therefore be obtained. When reversed the voltage, the electrodes can be recovered up to 90% within 5 min. This work presents the feasibility for the nano Ag and Ag@C on rGO electrodes applied in CDI process to produce drinking water from seawater or saline water. Ó 2014 Elsevier Ltd. All rights reserved. 1. Introduction Drinking water shortage has become worse in recent decades. At least 97% of water can be obtained from ocean. Therefore, the seawater desalination methods such as thermal, reverse osmosis, electrodialysis, and capacitive deionization (CDI) have been devel- oped rapidly. Compared with other desalination methods, CDI pos- sesses energy and high efficiency separation without secondary environmental pollution problems (Anderson et al., 2010; Porada et al., 2013). However, in the CDI processes, the electrodes could be fouled by organics in seawater. The CDI commercial processes are better used in low-salinity water, ground water and wastewa- ter (Gabelich et al., 2010; Gray et al., 2011). The CDI electrochemical reaction and its deionization mecha- nism on carbon electrodes by simulation were reported in 1960s (Evans and Hamilton, 1966; Murphy and Caudle, 1967). Opera- tions of the CDI are based on the electrical double layers on the electrode surfaces, and the ions can be captured by the counter electrodes in the electrolyte solution. CDI electrodes pos- sessing a high electrical conductivity, specific surface area and wetting ability could have a better capacity for capturing ions in seawater (Johnson and Newman, 1971; Song et al., 2013). The CDI electrode materials such as carbon aerogel, mesoporous carbons, activated carbons, carbon nanotubes, and graphene (rGO) have been widely studied (Farmer, 1995; Farmer et al., 1995; Choi, 2010; Li et al., 2010a, 2009; Mishra and Ramaprabhu, 2011; Wang et al., 2011). Graphene is a new mate- rial constructed with 2D nanostructured carbon that has single layers of sp 2 carbon hybridization. Graphene generally has a high electrical/thermal conductivity, good mechanical strength, and high specific surface area (Das et al., 2011; Li et al., 2013a). Jia and coworkers modified the graphene electrode surfaces by sulfonation to increase the hydrophobic, wetting ability, and specific area (Jia and Zou, 2012a, b). To increase the ability, graphene can be modified with porous carbon materials such as mesoporous carbons (Zhang et al., 2012), carbon black (Yan et al., 2010), and CNTs (Li et al., 2013b; Wimalasiri and Zou, 2013). Ag has a good thermal and electrical conductivity (Pasricha et al., 2009) and antibacterial ability (Das et al., 2011; Zheng et al., 2012). In the present work, to integrate the antimicrobial function in the CDI processes, Ag nanoparticles (i.e., nano Ag and Ag@C) were dispersed on graphene (rGO) as the electrodes. In addition to the CDI feasibility study with the new nano Ag/rGO and Ag@C/rGO electrodes, their chemical and physical properties http://dx.doi.org/10.1016/j.marpolbul.2014.05.020 0025-326X/Ó 2014 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. Tel.: +886 6 2763608; fax: +886 6 2752790. E-mail address: wanghp@mail.ncku.edu.tw (H.P. Wang). Marine Pollution Bulletin xxx (2014) xxx–xxx Contents lists available at ScienceDirect Marine Pollution Bulletin journal homepage: www.elsevier.com/locate/marpolbul Please cite this article in press as: Cai, P.-F., et al. Capacitive deionization of seawater effected by nano Ag and Ag@C on graphene. Mar. Pollut. Bull. (2014), http://dx.doi.org/10.1016/j.marpolbul.2014.05.020