Microbial Fuel Cells (MFCs) can be conveniently used for wastewater treatment and bioelectricity production. Their efficiency is strongly influenced by the physico-chemical properties of the ion-conducting membrane. In this work we prepare Nafion (TM)-based composite membranes by using mesoscale SBA-15 silica, and organic-inorganic fillers obtained by functionalizing SBA-15 with SO3H groups. The proposed membranes are tested as alternative separators in MFCs for applications in wastewater treatment and their performances compared to those of standard Naflon (TM) 117. Prolonged (3 months) MFC operation shows that the composite membrane with 5 wt% of SBA-15 functionalized with 10 mol% of SO3H gives maximum power density of 380 mW m(-3), namely three times better than that of Naflon (TM) after 90 days of operation. The same membrane offers a very effective COD removal after 14 days (more than 95%), an impressive coulombic efficiency of 34%, and very high resistance to biofouling. We conclude that the use of silica-based SO3H functionalized fillers is a powerful strategy to improve the performances of Nafion (TM) membranes in MFCs. (C) 2016 Elsevier B.V. All rights reserved.