Carbohydrate Polymers 175 (2017) 149–157 Contents lists available at ScienceDirect Carbohydrate Polymers journal homepage: www.elsevier.com/locate/carbpol Porous composite membranes based on cellulose acetate and cellulose nanocrystals via electrospinning and electrospraying Santhosh S. Nair ∗ , Aji P. Mathew ∗ Division of Materials and Environmental Chemistry, Stockholm University, 10691 Stockholm, Sweden a r t i c l e i n f o Article history: Received 11 May 2017 Received in revised form 26 June 2017 Accepted 16 July 2017 Available online 20 July 2017 Keywords: Porous cellulose fibers Cellulose nanocrystals Adsorption Surface zeta potential Mechanical properties a b s t r a c t Porous and non-porous cellulose acetate (CA) – cellulose nanocrystal (CNC) electrospun nanocomposite fibers and electrosprayed-electrospun composite membranes were fabricated using two different binary solvent systems. To evaluate the expression of CNC as the active entity in the membrane, dye adsorption studies were carried out using Victoria Blue. To overcome the low surface area of thick porous fibers, a porous electrosprayed-electrospun composite has developed which exhibited 98% dye removal compared to non-porous counterparts (67.9%). The porous membrane with CNC showed an increase of 38 mV in surface zeta potential compared to 9 mV increases in the case of the nonporous membrane and after the dye adsorption, it maintained the negative charge, indicating that further adsorption is feasible. Moreover, the mechanical properties of porous fibers were found to be ten-fold better than that of nonporous fibers. Creating porous CA-CNC composites is demonstrated as a tool for ensuring better exposure of active materials during the adsorption reaction. © 2017 Elsevier Ltd. All rights reserved. 1. Introduction Cellulose is one of the most abundant organic polymers having attractive features such as biodegradability, chemical resistance, and thermal stability along with highly reactive surface functional groups (Matsuyama, Ohga, Maki, Tearamoto, & Nakatsuka, 2003; Qiu & Hu, 2013). Its ester form (Cellulose acetate CA) was widely studied for the applications such as reverse osmosis, ultrafiltra- tion, microfiltration (Matsuyama et al., 2003). The major attraction was the hydrophilicity of the CA membranes which avoids pore blocking and solute adsorption compared to its high flux hydropho- bic counterparts such as polyethersulfones, polyethylene, and polypropylene (Zydney & Zeman, 1996). Hence CA membranes were found application in commercial reverse osmosis and water filter application (Zydney & Zeman, 1996). The attempts to improve the commercial membranes are focused majorly in two directions either by increasing the functional moieties available for adsorption or by increasing the surface area (He et al., 2014; Herrera, Mathew, Wang, & Oksman, 2011; Vallejos, Peresin, & Rojas, 2012). CA membranes are prepared by numerous methods such as immersion precipitation method, thermally induced phase separa- ∗ Corresponding authors. E-mail addresses: santhosh.nair@mmk.su.se (S. S. Nair), aji.mathew@mmk.su.se (A.P. Mathew). tion, phase inversion, and electrospinning (Matsuyama et al., 2003; Qiu & Hu, 2013). Electrospinning has achieved considerable interest due to inherent properties of electrospun ultrafine fibers such as the large surface area to volume ratio, flexibility in surface character- istics and most importantly for its potential for commercial scale up (Chronakis, 2005). However, electrospinning most commonly produces smooth fibers which limit the application of these fibers in most of the affinity or adsorption membranes (Chronakis, 2005). For example, porous surface features are ideal not only for deposit- ing nanoparticles but also can act as anchoring points for grafting other reactive/functional moieties in the post-functionalization process (Senthamizhan, Celebioglu, Balusamy, & Uyar, 2015; Wang et al., 2016). In electrospinning, highly porous structures can be obtained either by engineering the solution properties or the pro- cess itself. To obtain porous structures, the electrospinning solution can be designed in such a way that either it contains a binary solvent system with high boiling point/low boiling point or by a solvent/non-solvent system (Luo, Nangrejo, & Edirisinghe, 2010). In either case, the fast evaporation of the one of the solvent gives rise to local phase separation and the solvent rich regions transformed into pores during electrospinning (Celebioglu & Uyar, 2011). The process modification involves spinning in the high humid environ- ments or into a liquid nitrogen baths, the idea here is to suppress the evaporation of the volatile solvent and create the solvent rich regimes in the electrospun fibers (Park & Lee, 2010). http://dx.doi.org/10.1016/j.carbpol.2017.07.048 0144-8617/© 2017 Elsevier Ltd. All rights reserved.