Palladium-Zeolite nanofiber as an effective recyclable catalyst membrane for water treatment Jungsu Choi a , Sophia Chan a , Garriott Yip a , Hyunjong Joo b , Heejae Yang a, * , Frank K. Ko a, ** a Department of Materials Engineering, University of British Columbia, Vancouver, V6T1Z4, Canada b Department of Environmental Energy Engineering, Kyonggi University, 94 San, Iui-dong, Youngtong-ku, Suwon-si, Gyeonggi-do, 442-760, South Korea article info Article history: Received 20 February 2016 Received in revised form 4 May 2016 Accepted 16 May 2016 Available online 18 May 2016 Keywords: Zeolite Palladium Nanofiber membrane Ammonia adsorption Oxidation Sustainable abstract Zeolite is an exciting natural material due to its unique capability of ammonium nitrogen (NH 3 eN) adsorption in water. In this study, multifunctional hybrid composites of zeolite/palladium (Ze/Pd) on polymer nanofiber membranes were fabricated and explored for sustainable contaminant removal. SEM and XRD demonstrated that zeolite and palladium nanoparticles were uniformly distributed and deposited on the nanofibers. NH 3 eN recovery rate was increased from 23 to 92% when palladium coated zeolite was embedded on the nanofiber. Multifunctional nanofibers of Ze/Pd membranes were able to adsorb NH 3 eN on the zeolites placed on the surface of fibers and palladium catalysts were capable of selective oxidation of NH 3 eN to N 2 gas. The cycling of NH 3 eN adsorption-oxidation, high flux, hydro- philicity, and flexibility of the membrane makes it a strong candidate for water treatment. © 2016 Elsevier Ltd. All rights reserved. 1. Introduction Nitrogen is an essential nutrient element for living organisms. However, discharge of nitrogen containing wastewater into the environment without removal of the contaminants can be harmful to ecosystems (Li et al., 2011). Excessive nitrogen (Especially ammonia nitrogen, NH 3 eN) can be toxic to human and aquatic life. Also, excessive nitrogen can cause eutrophication in rivers and marine waters. In wastewater treatment plants (WWTPs), NH 3 eN is traditionally removed by nitrification-denitrification by activated sludge (AS) with biological nitrogen removal (BNR) (Kurama et al., 2010; Kurniawan et al., 2006). In AS with BNR systems, anoxic (or anaerobic) and aerobic reactors are utilized to remove NH 3 eN mainly due to lower cost and fewer byproducts formed compared to other chemical approaches. For example, chloramines are formed during chlorination to remove NH 3 eN in water treatment plants (WTPs) as shown in Equation (1). NH 3 þHOCl/NCl 3 þH 2 O (1) However, efficiency of AS systems using either aerobic or anaerobic bacteria is sensitive to various environmental changes, especially during cold weather (Morgan-Sagastume and Allen, 2003). In addition, chlorine supplied for removal of NH 3 eN reacts with humic or fulvic acids, which produces trihalomethane (THM), a well-known carcinogen (Liang and Singer, 2003). Recently ad- sorbents such as activated carbon or zeolite have attracted great interest due to its simplicity of operation, less byproducts, and robustness to operation environment. Particularly zeolite, had been actively explored in WTPs and WWTPs due to high adsorbance capacity for ammonia in aqueous environments (Hedstr€ om and Amofah, 2008; Weatherley and Miladinovic, 2004; Xie et al., 2014; Yan et al., 2013). NH 3 eN attached to zeolite can be chemi- cally or biologically recycled by NaCl, NaOH, and microorganisms. However, wide use of zeolite is hindered by high processing cost, complicated recycle processes, and the disposal challenges of chemicals or microorganisms used to recycle zeolite (Doula, 2009; Faghihian and Kabiri-Tadi, 2010; Kumar et al., 2006). Also, pulver- ized zeolite particles used during the water treatment process are difficult to harvest from water, which limits the minimum size of zeolite and reduces the surface area for NH 3 eN adsorption. * Corresponding author. ** Corresponding author. E-mail addresses: jungsu@mail.ubc.ca (J. Choi), s.chan@alumni.ubc.ca (S. Chan), garriott.yip@alumni.ubc.ca (G. Yip), hjjoo@kgu.ac.kr (H. Joo), heejae.yang@ubc.ca (H. Yang), frank.ko@ubc.ca (F.K. Ko). Contents lists available at ScienceDirect Water Research journal homepage: www.elsevier.com/locate/watres http://dx.doi.org/10.1016/j.watres.2016.05.051 0043-1354/© 2016 Elsevier Ltd. All rights reserved. Water Research 101 (2016) 46e54