22 nd I nternational Symposium on Plasma Chemistry July 5-10, 2015; Antwerp, Belgium P-III-6-57 1 Plasma surface modification of hydrophilic polyethersulfone membranes for air gap membrane distillation (AGMD) S. Pedram 1,2 , F. Arefi-Khonsari 1 , H.R. Mortaheb 2 , H. Fakhouri 1 , S. Mehvari 2 and J. Pulpytel 1 1 Université Pierre et Marie Curie, Laboratoire Interfaces et Systèmes Electrochimiques, Paris, France 2 Chemistry and Chemical Engineering Research Centre of Iran, Tehran, Iran Abstract: Present research work is devoted to develop hydrophobic polyethersulfone (PES) membranes for wastewater treatment. Ultrathin polymer films were prepared in two ways: plasma enhanced chemical vapor deposition with propane as a precursor and physical vapor deposition with PTFE target. By combining the enhanced polymer hydrophobicity and high porosity, static contact angles up to 124 were obtained. The plasma modified membranes were examined for benzene removal using an air gap contact membrane distillation process. Keywords: hydrophobic membrane, air gap membrane distillation, low pressure plasma enhance chemical vapour depositions, sputtering, PES 1. Introduction Serious threatens by the presence of chemical compounds released by industries in environment, makes it inevitable to use efficient treatment methods for controlling emissions by these polluting resources. Among the environmental pollutants, volatile organic compounds (VOCs) are especially important because of their destructive effects and their extensive presence in refinery wastewaters as well as petrochemical industries, but also rubber, plastics, paper, leather and textiles [1]. Membrane Distillation (MD) is a recent thermally- driven separation process technology in water purification processes, in which vapour molecules pass through a porous hydrophobic membrane. The process driving force is the difference between partial pressures at both sides of the membrane. Separation of volatile pollutants by this method is based on their evaporation and transfer through the hydrophobic porous membrane [2-4]. The main requirements for the MD process are that the membrane must not be wetted and only vapour and non- condensable gases would pass through its pores. Then, a hydrophobic microporous membrane meets these requirements [5]. Polyethersulfune (PES) is a non- crystalline polymer which is suitable for membrane preparation in terms of cost and processability. However, the main disadvantage of the polymer for this particular application is its relative hydrophilicity. Therefore, some corrective surface treatments are needed to make these membranes applicable in membrane distillation process. Plasma surface modification has shown advantages in changing the surface wettability of the materials in the nanometer scale, without affecting the bulk properties, and has been widely used in membrane surface modification [6]. Surface modification by plasma polymerization for the formation of a hydrophobic layer on a hydrophilic base membrane was conducted accordingly. The aim of this work is to investigate the performance of treated membranes by physical vapour deposition (sputtering) as well as plasma assisted chemical vapour deposition in MD system. In this regards, attempts were made to deposit fluoropolymer films in an RF magnetron system, using Ar, as the sputtering gas on a PTFE target. In parallel, propane plasma has been used by low pressure plasma to improve the membrane hydrophobicity. 2. Experimental procedure PES membranes were prepared by phase inversion technique (100 μm thick) according to reference 7 and in were used as substrates. The membranes were placed on central substrate holder. The chamber was evacuated to 0.4 mbar. The substrates were etched in a first step in air which was introduced in the chamber with a radio frequency 13.56 MHz (RF) glow discharge for 2 minutes. Then propane was injected by using a LF (40 KHz) power supply generator. Pressure was set in the range of 0.7-1.5 mbar by changing the propane gas flow rate in range of 9-20 sccm at a constant power of 3.6 W. In the PVD process, fluorocarbon coatings were deposited by rf magnetron sputtering at 13.56 MHz with Teflon target fixed on a cooled magnetron cathode, fixed at a distance of 120 mm from the substrate. The sputtering chamber was evacuated to a background pressure of 10 -5 mtorr before admitting the argon gas. The Teflon films were also deposited also on silicon wafers for analytical purposes. The AGMD experiments were carried out using the experimental set-up presented schematically in Fig. 1. The feed solution was supplied from the feed tank to the feed chamber of the membrane module and the retentate was turned back to the feed tank by a circulation pump. A cooling liquid (water) was recycled from the cooling tank to the cooling chamber of the membrane module.