CHEMICAL ENGINEERING TRANSACTIONS VOL. 60, 2017 A publication of The Italian Association of Chemical Engineering Online at www.aidic.it/cet Guest Editors: Luca Di Palma, Elisabetta Petrucci, Marco Stoller Copyright © 2017, AIDIC Servizi S.r.l. I SBN 978-88-95608- 50-1; I SSN 2283-9216 Thermoplasmonic Membrane Distillation Antonio Politano a,b , Gianluca Di Profio c , Vanna Sanna d , Efrem Curcio e* a Department of Physics, University of Calabria - Via P. Bucci Cubo 31/C, 87036 Rende (CS) Italy b Italian Institute of Technology, Graphene Labs, Via Morego 10, 16163 Genova, Italy c Institute on Membrane Technology, National Research Council of Italy ITM-CNR, Italy - Via P. Bucci Cubo 17C, 87036 Rende (CS) Italy d Nanomater S.r.l., Porto Conte Ricerche, Loc. Tramariglio, 07041 Alghero (SS). e Department of Environmental and Chemical Engineering DIATIC, University of Calabria - Via P. Bucci Cubo 45A, 87036 Rende (CS) Italy e.curcio@unical.it Membrane Distillation (MD) is a hybrid thermal/membrane technology emerging either as a promising alternative or as a complement to Reverse Osmosis, having the potential to concentrate saline solutions even up to supersaturation. Presently, performance of conventional MD systems is drastically affected by temperature polarization, a phenomenon intrinsically connected to the removal of latent heat due to evaporation, which causes the decrease of feed temperature at the membrane surface with respect to the bulk. As a consequence, the net driving force to mass transfer falls down along with the thermal efficiency of the process. Due to these adverse effects, technological applications of MD are still elusive. In this work, we prove that thermoplasmonic effect induced by photothermal excitations of silver nanoparticles (Ag NPs), incorporated into polyvinylidene (PVDF) membranes, remarkably increase the feed temperature at the membrane surface exposed to light radiation, thus achieving unmatched performance in a vacuum MD unit. 1. Introduction With a global capacity currently around 100 million m 3 /day, the desalination market (expected to jump to $ 50 billion by 2020) is largely dominated by membrane technology; large Seawater Reverse Osmosis (SWRO) installations exhibit an energy consumption of 3-4 kWh per m 3 drinking water and a unit water cost approaching 0.5 $/m 3 . However, SWRO technology still faces crucial technological challenges, mostly related to a relatively low overall recovery factor, about 30-50%, limited by concentration polarization phenomena. As a consequence, half cubic meter of brine at molar concentration of about 1 M in NaCl is produced per cubic meter of feed seawater and released in the environment. Literature studies demonstrate adverse ecological and toxicological impacts of hypersaline brines on echinoids and ascidians, sediment infauna, seagrass and epifauna, planktons, fishes and clams (Lattemann and Höpner, 2008). MD is a hybrid thermal/membrane technology, not limited by concentration polarization, having the potential to produce desalted water at recovery factors greater than 85%. In MD, a microporous hydrophobic membrane is in contact with a heated feed solution: the hydrophobic character of the membrane prevents the permeation of molecules in liquid phase (no filtration), while sustaining a vapour-liquid interface at the pores mouth. Here, water evaporates (whereas non-volatile solutes are retained), diffuses across the membrane, and condenses on the opposite side (“distillate”). Theoretically, MD guarantees a complete rejection of non-volatile solutes such as macromolecules, colloidal species, ions etc. Relatively low temperature gradients are generally sufficient to establish a satisfactory transmembrane flux (1-10 l/m 2 h); typical feed temperatures vary in the range of 50-80°C, allowing the efficient recycle of low-grade or waste heat streams, as well as the use of alternative energy sources such as solar, wind or geothermal (Al-Obaidani et al., 2008; Curcio et al., 2005; Majidi Salehi et al., 2016). The ability of MD to concentrate an aqueous solution up to supersaturation has been also exploited for the crystallization of biomolecules and active pharmaceutical ingredients (Curcio et al., 2016, Di Profio et al., 2007, Di Profio et al., 2010). Tufa et al. (2015) proposed a hybrid MD/ Reverse Electrodialysis system for DOI: 10.3303/CET1760051 Please cite this article as: Politano A., Di Profio G., Sanna V., Curcio E., 2017, Thermoplasmonic membrane distillation, Chemical Engineering Transactions, 60, 301-306 DOI: 10.3303/CET1760051 301