Journal of Basic and Applied Engineering Research p-ISSN: 2350-0077; e-ISSN: 2350-0255; Volume 4, Issue 3; April-June, 2017, pp. 229-233 © Krishi Sanskriti Publications http://www.krishisanskriti.org/Publication.html Study on Membrane Fouling in Vacuum Membrane Distillation for Desalination Jitendra Kumar Singh 1 , Sushant Upadhyaya 2 , S.P. Chaurasia 3* and Rakesh Baghel 4 1 Department of Chemical Engineering, IET, JK Lakshmipat University Jaipur (India) 2,3,4 Department of Chemical Engineering, MNIT Jaipur (India) E-mail: 1 jitendrasingh.chmnit@gmail.com Abstract—In this work, membrane fouling was studied in vacuum membrane distillation for different pore sizes and membrane materials. Hydrophobic membrane of PTFE and PVDF was taken of two different pore diameter viz0.22 and 0.45 micron in a membrane module. The experiments were carried out using aqueous feed solution of NaCl at different feed concentrations over a period of 200hrs and 340hrs for different membranes. The decline in permeate flux was observed as 1.7% & 4.0 % for 0.22 μm PTFE membrane and 4.0 % & 9.0 % for 0.22 μm PVDF membrane in 200 hrs and 340 hrs continuous run respectively. Similarly the decline in permeate flux was observed for 0.45 μm PTFE & PVDF membranes, 2.6 % & 7.2% and 6.3% & 12.5% respectively in 200hrs and 340 hrs continuous run. SEM analysis was also carried out new brand and used membranes after 200hrs and 340hrs run time which confirmed the deposition of feed solute on membrane surface. This minor scale deposition is also evident from pore size distribution (PSD) which indicated that average pore size in PSD curve shifted from 0.22 μm to 0.18 μm and this little problem was very easily overcome by water washing. Keywords: Vacuum membrane distillation, Specific energy, PTFE, Ion meter, NaCl, Reverse Osmosis. 1. INTRODUCTION Membrane distillation (MD) is known to be one of the growing non-isothermal membrane separation processes [1]. MD is a technique which leads toan almost complete water recovery. MD is defined as thermally driven transport process of vapor through hydrophobic membranes, the basic driving force in MD is the vapor pressure difference through membrane thickness. However, in other membrane separation processes, the basic driving force is the chemical potential difference through the membrane thickness [2–4]. Different MD configurations such as direct contact MD, sweeping gas MD, air gapMD, and vacuum membrane distillation (VMD) are used rapidly for various applications (desalination, water- reuse, food, medical, etc.). The resulting driving force of vapor pressure difference produces a flux of water vapor through the membrane, and thus, aqueous brine solutions can be concentrated and crystallized. This process can work on high solute concentration at feed side, at low concentration gradients, moderate temperature, and atmospheric pressure [5]. The advantages of VMD compared to other more popular separation processes are theoretically 100% rejection of ions, colloids, macro molecules, and other non-volatiles, lower operating pressure than conventional pressure-driven membrane separation processes, lower operating temperature than conventional distillation, and reduced vapor pressure compared to conventional distillation processes. VMD differs from the other membrane technologies in that the basic driving force for desalination is the difference in vapor pressure of water across the membrane, rather than total pressure. In VMD configuration, the vapor permeated does not condense in cooling chamber, but is drawn out by vacuum and condenses externally in a condenser. The pressure difference between the two sides of the membrane creates a convective mass flow along the pores that contribute to the total mass transfer for VMD. In this paper, membrane fouling was extensively studied on membrane surfaces of different pore sizes and membrane materials. The deposition of salts was determined using the scanning electron microscopy (SEM) and the reduction of pore size was confirmed using pore size distribution analysis. 2. MATERIAL AND METHODS The experimental VMD permeate flux (N, kg/m 2 h) is calculated by equation (1): Where V is volume of permeate water (l); ρ is density of permeate water (kg/l); A is effective membrane area (m2) and t is the running time of VMD. The concentration of ionic species in the feed water (C1, mg/l) and in permeate water (C2, mg/l) were calculated by the conductivity meter [1,8]. The percentage removal (% R) of the species was calculated from equation (2): 1 2 1 100 C C R C   