Lijo Francis

Fabrication of electrospun nanofibrous membranes for membrane distillation application

Abstract Nanofibrous membranes of Matrimid have been successfully fabricated using an electrospinning technique under optimized conditions. Nanofibrous membranes are found to be highly hydrophobic with a high water contact angle of 130°. Field emission scanning electron microscopy and pore size distribution analysis revealed the big pore size structure of electrospun membranes to be greater than 2 μm and the pore size distribution is found to be narrow. Flat sheet Matrimid membranes were fabricated via casting followed by phase inversion. The morphology, pore size distribution, and water contact angle were measured and compared with the electrospun membranes. Both membranes fabricated by electrospinning and phase inversion techniques were tested in a direct contact membrane distillation process. Electrospun membranes showed high water vapor flux of 56 kg/m2-h, which is very high compared to the casted membrane as well as most of the fabricated and commercially available highly hydrophobic membranes.

Engineering Hydrophobic Organosilica Nanoparticle-Doped Nanofibers for Enhanced and Fouling Resistant Membrane Distillation

Engineering and scaling-up new materials for better water desalination are imperative to find alternative fresh water sources to meet future demands. Herein, the fabrication of hydrophobic poly(ether imide) composite nanofiber membranes doped with novel ethylene-pentafluorophenylene-based periodic mesoporous organosilica nanoparticles is reported for enhanced and fouling resistant membrane distillation. Novel organosilica nanoparticles were homogeneously incorporated into electrospun nanofiber membranes depicting a proportional increase of hydrophobicity to the particle contents. Direct contact membrane distillation experiments on the organosilica-doped membrane with only 5% doping showed an increase of flux of 140% compared to commercial membranes. The high porosity of organosilica nanoparticles was further utilized to load the eugenol antimicrobial agent which produced a dramatic enhancement of the antibiofouling properties of the membrane of 70% after 24 h.

Submerged membrane distillation for seawater desalination

AbstractA submerged membrane distillation (SMD) process for fresh water production from Red Sea water using commercially available hollow fiber membranes has been successfully employed and compared with the conventional direct contact membrane distillation (DCMD) process. The hollow fiber membranes have been characterized for its morphology using field effect scanning electron microscope. In SMD process, a bunch of hollow fiber membranes are glued together at both ends to get a simplified open membrane module assembly submerged into the coolant tank equipped with a mechanical stirrer. Hot feed stream is allowed to pass through the lumen side of the membrane using a feed pump. Continuous stirring at the coolant side will reduce the temperature and concentration polarization. During the conventional DCMD process, using feed-coolant streams with co-current and counter-current flows has been tested and the results are compared in this study. In SMD process, a water vapor flux of 10.2 kg m−2 h−1 is achieved wh...

Performance of different hollow fiber membranes for seawater desalination using membrane distillation

AbstractMembrane distillation requires a highly porous hydrophobic membrane with low surface energy. In this paper, we compare the direct contact membrane distillation (DCMD) performances of four different types of in-house fabricated hollow fiber membranes and two different commercially available hollow fiber membranes. Hollow fiber membranes are fabricated using wet-jet phase inversion technique and the polymeric matrices used for the fabrication are polyvinylidine fluoride (PVDF) and polyvinyl chloride (PVC). Commercial hollow fiber membrane materials are made of polytetrafluoroethylene (PTFE) and polypropylene (PP). PVDF hollow fibers showed a superior performance among all the hollow fibers tested in the DCMD process and gave a water vapor flux of 31 kg m−2h−1 at a feed and coolant inlet temperatures of 80 and 20°C, respectively. Under the same conditions, the water vapor flux observed for PP, PTFE, and PVC hollow fiber membranes are 13, 11, and 6 kg m−2h−1, respectively, with 99.99% salt rejection o...

Case Study: Oasys Water—Forward Osmosis

Abstract Oasys Water developed the first membrane brine concentrator (MBC) employing ammonia and carbon dioxide-based draw solution to treat high salinity brine streams and wastewater, using a forward osmosis (FO) process, producing a high quality permeate water that can be reused in any industrial process. According to Oasys Water, they are the only FO provider that develops all three key components of its systems: optimized and patented FO membranes, powerful draw solution chemistries, and highly efficient draw solution recovery systems. In the last few years, Oasys Water has been testing pilot units in three different facilities, with promising results in the treatment of industrial wastewater, which validate the viability of the product: i) Pennsylvania based Marcellus Shale plant, used to treat highly variable water, product of large volumes of frac flowback and water with high concentrations of total dissolved solids (TDS) from natural gas extraction, ii) the testing facility in Permian Basin at Midland, Texas, testing high TDS water from oil and gas operations, and iii) Changxing Power Plant pilot unit, the world’s first commercial application of FO-based zero liquid discharge (ZLD). Several advantages of the use of Oasys Water FO technology have been demonstrated, such as the ability to concentrate brines up to a high TDS concentration for further processing in a crystallizer, lower capital costs compared to evaporative ZLD technologies, reduced energy requirements and the elimination of thermal scaling concerns.