Contents lists available at ScienceDirect Journal of Water Process Engineering journal homepage: www.elsevier.com/locate/jwpe Bio-inspired, fouling resistant, tannic acid functionalized halloysite nanotube reinforced polysulfone loose nanofiltration hollow fiber membranes for efficient dye and salt separation G.P. Syed Ibrahim a,c , Arun M. Isloor a,c, ⁎ , A. Moslehyani b,c , A.F. Ismail b,c a Membrane Technology Laboratory, Department of Chemistry, National Institute of Technology Karnataka, Surathkal, Mangalore 575 025, India b Department of Chemical and Biological Engineering, University of Ottawa,161 Louis Pasteur St., Ottawa, ON K1N 6N5, Canada c Advanced Membrane Technology Research Center (AMTEC), Universiti Teknologi Malaysia, 81310 Skudai, Johor Bahru, Malaysia ARTICLE INFO Keywords: Loose nanofiltration Salt Dye Halloysite nanotube Tannic acid Hollow fiber membrane ABSTRACT Superficial functionalization of the hollow fiber membrane with progressive nanomaterials exhibits increased hydrophilicity, outstanding selectivity, and permeability. In the present study, a simple and novel loose nano- filtration (NF) membranes were prepared by the addition of tannic acid functionalized halloysite nanotubes (THNTs) in polysulfone (PSf) membrane matrix via phase inversion method. The successful modification of halloysite (HNTs) was confirmed by FT-IR, zeta potential measurement, TGA, TEM and EDX analysis. The membrane permeation studies were carried out with a sequence of salts (NaCl and Na 2 SO 4 ) and dyes (reactive black 5 and reactive orange 16). The resulted membranes exhibited increased hydrophilicity, porosity, water uptake, antifouling performance, along with higher dye rejection (> 99% for reactive black 5 and > 90% of reactive orange 16) and low salt rejection (2.5% of NaCl and 7.5% of Na 2 SO 4 ) properties. The nanocomposite membrane also exhibited the highest pure water flux of 92 L/m 2 h compared to the pristine membrane of 18 L/ m 2 h made it a worthy candidate for the wastewater purification. 1. Introduction The increased concentration of pollutants is inflowing water pro- visions through anthropogenic sources, affecting in the insufficient entry to clean water for the rising worldwide inhabitants [1]. The wastewater from the industries such as a dye, paper, paint, and tan- neries are needed to treat appropriately before discarding or recycling. The direct discharge of organic dyes into water stream lead to severe environmental imbalance, as most of them are non-biodegradable, toxic and consume dissolved oxygen [2–4]. More complex structure, high molecular weight and synthetic origin of reactive dyes make them more stable, particularly even just 1.0 mg/L concentration in drinking water possibly will impart color [5,6]. In dye industry, water is employed primarily as steam for heat treatment of the bath and then for trans- ferring dyes to the fibers. The dyeing of about 1 kg of cotton needs around 152 L of water, ∼0.8 kg of NaCl and somewhere around 60 g of dyestuff [7]. Therefore, reclamation of dye from wastewater has ex- cessive importance. Furthermore, inorganic salts such as NaCl (∼6 wt %) and Na 2 SO 4 (∼5.7 wt%) were incorporated to improve dye pickup ability of the cotton and during synthesis of dye, quite large amount of low molecular weight intermediates are produced [8]. The occurrence of inorganic salts not only restraining the biodegradation of dyes but complicates the treatment processes as well [9,10]. In the thought of sustainability, the recovery of dyes and salts from the wastewater needs a new technique which is cost effective, less time consuming and en- vironmental friendly. Conventional methods, such as electrochemical [11,12], oxidation [13], coagulation by polymeric aluminum species [14] are having the similar disadvantages that, the resources are not recycled adequately [15]. The employment of loose nanofiltration (NF) membrane has been recognized as the complementary nominee for the wastewater man- agement as it has advantages like low cost, low operating pressure, environmentally friendly, less energy consumption, high dye rejection and high salt permeability [16–18]. Even though NF has the capacity to reject more than 99% of dyes, it has a high rejection of inorganic salts (> 30% NaCl), membrane fouling, concentration polarization and molecular weight cut-off (MWCO) of 100–1000 Da signifying the near pore size of 1 nm. Unavoidably, NF requires a high frequency of che- mical cleaning, which would affect the lifespan of membranes. The above shortcomings make the NF as the insignificant candidate for the separation of dye/salt mixture [19–22]. Therefore, it is of prime im- portance to study the loose NF membranes. Lin et al. reported the http://dx.doi.org/10.1016/j.jwpe.2017.09.015 Received 6 July 2017; Received in revised form 18 September 2017; Accepted 20 September 2017 ⁎ Corresponding author at: Membrane Technology Laboratory, Department of Chemistry, National Institute of Technology Karnataka, Surathkal, Mangalore 575 025, India. E-mail address: isloor@yahoo.com (A.M. Isloor). Journal of Water Process Engineering 20 (2017) 138–148 2214-7144/ © 2017 Elsevier Ltd. All rights reserved. MARK