The Role of Silver Nanoparticles on Mixed Matrix Ag/Cellulose Acetate Asymmetric Membranes Shirish H. Sonawane, 1 Antonine Terrien, 2 Ana Sofia Figueiredo, 3,4 M. Clara Gonc¸alves, 5,6 Maria Norberta De Pinho 3,5 1 Department of Chemical Engineering, National Institute of Technology, Warangal 546004, India 2 ETU, University of Nantes, Nantes, France 3 CEFEMA, Instituto Superior T  ecnico, Universidade de Lisboa, Lisbon, Portugal 4 Departmental Area of Chemical Engineering, Instituto Superior de Engenharia de Lisboa, Lisbon, Portugal 5 Departamento de Engenharia Qu  ımica, Instituto Superior T  ecnico, Universidade de Lisboa, Lisbon, Portugal 6 Centro de Qu  ımica Estrutural, Instituto Superior T  ecnico, Universidade de Lisboa, Lisbon, Portugal Mixed matrix asymmetric membranes were prepared by the addition of silver nanoparticles to cellulose ace- tate/acetone/formamide casting solutions with ratios acetone/formamide varying from 1.44 to 2.77 to pre- pare ultrafiltration/nanofiltration membranes covering a wide range of hydraulic permeabilities. Binding of the silver nanoparticles to the polymer matrix is revealed through comparison of the FTIR spectra of the cellulose acetate and the Ag/cellulose acetate membranes. In the later, there is a decrease of the ratio between the bands intensities at 2,000– 2,500 cm 21 . Membrane surface charge of the mixed matrix membranes varies with the pore size and pH, and when compared with cellulose acetate membranes there is a decrease of the negative surface charge densities. The silver nanoparticles in all mixed matrix membranes results in an enhancement of the hydraulic permeabilities, ranging from 10.8 kg m 22 h 21 bar 21 to 67.1 kg m 22 h 21 bar 21 . POLYM. COMPOS., 00:000–000, 2015. V C 2015 Society of Plastics Engineers INTRODUCTION Polymeric membranes have a variety of applications in chemical processing industries, waste water treatment, wine making industries, food, and pharmaceutical indus- tries [1]. Nanoparticles are being used in the preparation of asymmetric mixed matrix membranes, because of its ability to have different charges on “its” surface. These nanoparticles can be responsible to generate different pos- itive or negative charges and may be useful for enhance- ment of selective separation and as anti fouling agents especially in the case of protein separation [2, 3]. Cellu- lose acetate asymmetric membranes prepared by the phase inversion technique are reported to be a common kind of membranes that are easy to prepare a wide range of structures due to the versatility of formulating the cast- ing solutions and the casting conditions. In fact, the varia- tion of the solvent system and in particular the ratio of acetone/formamide makes them to classify into ultrafiltra- tion, nanofiltration and reverse osmosis membranes based on their surface pore size distribution [4]. Membrane sep- aration efficiency depends on a several physical proper- ties of the membrane, such as hydraulic permeability and thickness, and on operation variables as a transmembrane pressure, filtration time and feed concentration. A variety of nanoparticles are reported in literature to be used in mixed matrix membranes such as silver nanoparticles, gold colloids, alumina and other metals and metal oxides. Lee et al. [5] reported the preparation of polyamide mixed matrix TiO 2 nanocomposites using an interfacial polymerization process. They reported the added of TiO 2 nanoparticles during the polymerization. They observed that the nanoparticles remain on the surface of the mem- brane and that the rejection to MgSO 4 is around 95% and the permeation rate is as high as 9.1 L/m 2 h (at 0.6 MPa). Hu et al. [6] prepared a nanocomposite matrix of Correspondence to: S. H. Sonawane; e-mail: shirishsonawane09@gmail. com DOI 10.1002/pc.23557 Published online in Wiley Online Library (wileyonlinelibrary.com). V C 2015 Society of Plastics Engineers POLYMER COMPOSITES—2015