Thin-film composite crosslinked polythiosemicarbazide membranes for organic solvent nanofiltration (OSN) Jamaliah Aburabie, Pradeep Neelakanda, Madhavan Karunakaran, Klaus-Viktor Peinemann ⇑ Advanced Membranes and Porous Materials Center, King Abdullah University of Science and Technology, Thuwal 23955-6900, Saudi Arabia article info Article history: Received 23 June 2014 Received in revised form 13 September 2014 Accepted 15 September 2014 Available online 22 September 2014 Keywords: Organic solvent nanofiltration Polythiosemicarbazide Diaminopiperazine Trimesoyl chloride Interfacial polymerization Thin-film composite membranes abstract In this work we report a new class of solvent stable thin-film composite (TFC) membrane fabricated on crosslinked polythiosemicarbazide (PTSC) as substrate that exhibits superior stability compared with other solvent stable polymeric membranes reported up to now. Integrally skinned asymmetric PTSC membranes were prepared by the phase inversion process and crosslinked with an aromatic bifunctional crosslinker to improve the solvent stability. TFC membranes were obtained via interfacial polymerization using trimesoyl chloride (TMC) and diaminopiperazine (DAP) monomers. The membranes were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and contact angle measurement. The membranes exhibited high fluxes toward solvents like tetrahydrofuran (THF), dimethylformamide (DMF) and dimethylsulfoxide (DMSO) ranging around 20 L/m 2 h at 5 bar with a molecular weight cut off (MWCO) of around 1000 g/mol. The PTSC-based thin-film composite membranes are very stable toward polar aprotic solvents and they have potential applications in the petrochemical and pharmaceutical industry. Ó 2014 Elsevier B.V. All rights reserved. 1. Introduction Various techniques like distillation, adsorption, and chromatog- raphy are widely being used for the separation of solutes from organic solvents. These processes often have high energy and operation costs [1]. An alternate approach of using polymeric membranes for such separation processes can in many cases reduce these costs effectively [2–5]. Organic solvent nanofiltration (OSN) is an emerging membrane- based separation process which separates mixtures on a molecular level [5] very efficiently compared with other traditional industrial processes. OSN is a pressure driven separation process without phase transfer and uses membranes with pore size diameters between 0.2 and 0.5 nm that are capable of separating solutes with molecular weights (MWCOs) of 200–1000 g/mol [6,7] in organic solvents. One of the mostly studied polymers for OSN is polyimide (PI). Crosslinked PI membranes are chemically stable toward organic solvents [8–13] and are used for separations widely. Research is heading toward finding new polymeric membranes that are stable in a wide range of organic solvents and which can compete with existing membranes in terms of fluxes and rejec- tions. One attractive polymer is polythiosemicarbazide (PTSC, Fig. 1), which was first introduced in 1962 for its ability to form stable chelates with wide range of metals [14,15]. PTSC was only recently used as membrane material for the first time [16]. But in this work the PTSC was not crosslinked and the gold loaded membrane was used as a catalytically active membrane in water. PTSC dissolves very well in dimethylsulfoxide (DMSO) and par- tially in other polar aprotic solvents. In this work, a dope solution from DMSO was used to cast membranes. Crosslinking is a well known method that promotes resistance to chemical dissolution [17] and reduces the mobility of the poly- mer chains, which leads to higher selectivity and stability while maintaining permeability. Crosslinking with an aromatic bifunc- tional crosslinker is proved to enhance the stability of polymers toward organic solvents [1]. In this work a, a-dibromo-p-xylene (DBX) was used as a crosslinking agent. Preparation of thin-film composite (TFC) membranes via inter- facial polymerization (IP) is a promising method and new approach to manufacture membranes for nanofiltration in organic solvents. From literature studies, it is believed that TFC – OSN membranes have the potential to achieve higher fluxes compared with inte- grally skinned asymmetric OSN membranes, without compromis- ing high rejection [12]. http://dx.doi.org/10.1016/j.reactfunctpolym.2014.09.011 1381-5148/Ó 2014 Elsevier B.V. All rights reserved. ⇑ Corresponding author. Tel.: +966 128082769. E-mail address: klausviktor.peinemann@kaust.edu.sa (K.-V. Peinemann). Reactive & Functional Polymers 86 (2015) 225–232 Contents lists available at ScienceDirect Reactive & Functional Polymers journal homepage: www.elsevier.com/locate/react