Energy efficiency of permeate gap and novel conductive gap membrane distillation

This work presents numerical modeling results and flux experiments for a novel membrane distillation configuration called conductive gap membrane distillation (CGMD), as well as permeate gap membrane distillation (PGMD). CGMD has a conductive spacer in the gap between the membrane and condensing surface rather than more commonly used insulating materials. Flux measurements with two experimental systems are used to validate the numerical models for PGMD and CGMD. PGMD has 20% higher GOR (energy efficiency) than an air gap membrane distillation (AGMD) system of the same size, whereas CGMD can have two times higher GOR than even PGMD. Increasing gap effective thermal conductivity in CGMD has negligible benefits beyond View the MathML source under the conditions of this study. The direction of pure water flow in the gap has a significant influence on overall system energy efficiency, especially in the case of CGMD. Using a countercurrent configuration for the pure water flow in the gap relative to the cold stream leads to 40% higher GOR than flow cocurrent with the cold water stream.MIT & Masdar Institute Cooperative Program (Reference no. 02/MI/MI/CP/11/07633/ GEN/G/00

Improving Liquid Entry Pressure of Polyvinylidene Fluoride (PVDF) Membranes by Exploiting the Role of Fabrication Parameters in Vapor-Induced Phase Separation VIPS and Non-Solvent-Induced Phase Separation (NIPS) Processes

Polyvinylidene fluoride (PVDF) is a popular polymer material for making membranes for several applications, including membrane distillation (MD), via the phase inversion process. Non-solvent-induced phase separation (NIPS) and vapor-induced phase separation (VIPS) are applied to achieve a porous PVDF membrane with low mass-transfer resistance and high contact angle (hydrophobicity). In this work, firstly, the impacts of several preparation parameters on membrane properties using VIPS and NIPS were studied. Then, the performance of the selected membrane was assessed in a lab-scale direct-contact MD (DCMD) unit. The parametric study shows that decreasing PVDF concentration while increasing both relative humidity (RH) and exposure time increased the contact angle and bubble-point pore size (BP). Those trends were investigated further by varying the casting thickness. At higher casting thicknesses and longer exposure time (up to 7.5 min), contact angle (CA) increased but BP significantly decreased. The latter showed a dominant trend leading to liquid entry pressure (LEP) increase with thickness

Improving Liquid Entry Pressure of Polyvinylidene Fluoride (PVDF) Membranes by Exploiting the Role of Fabrication Parameters in Vapor-Induced Phase Separation VIPS and Non-Solvent-Induced Phase Separation (NIPS) Processes

Polyvinylidene fluoride (PVDF) is a popular polymer material for making membranes for several applications, including membrane distillation (MD), via the phase inversion process. Non-solvent-induced phase separation (NIPS) and vapor-induced phase separation (VIPS) are applied to achieve a porous PVDF membrane with low mass-transfer resistance and high contact angle (hydrophobicity). In this work, firstly, the impacts of several preparation parameters on membrane properties using VIPS and NIPS were studied. Then, the performance of the selected membrane was assessed in a lab-scale direct-contact MD (DCMD) unit. The parametric study shows that decreasing PVDF concentration while increasing both relative humidity (RH) and exposure time increased the contact angle and bubble-point pore size (BP). Those trends were investigated further by varying the casting thickness. At higher casting thicknesses and longer exposure time (up to 7.5 min), contact angle (CA) increased but BP significantly decreased. The latter showed a dominant trend leading to liquid entry pressure (LEP) increase with thickness

Sustainable biomimetic solar distillation with edge crystallization for passive salt collection and zero brine discharge

Abstract The urgency of addressing water scarcity and exponential population rise has necessitated the use of sustainable desalination for clean water production, while conventional thermal desalination processes consume fossil fuel with brine rejection. As a promising solution to sustainable solar thermal distillation, we report a scalable mangrove-mimicked device for direct solar vapor generation and passive salt collection without brine discharge. Capillarity-driven salty water supply and continuous vapor generation are ensured by anti-corrosion porous wicking stem and multi-layer leaves, which are made of low-cost superhydrophilic nanostructured titanium meshes. Precipitated salt at the leaf edge forms porous patch during daytime evaporation and get peeled by gravity during night when saline water rewets the leaves, and these salt patches can enhance vaporization by 1.6 times as indicated by our findings. The proposed solar vapor generator achieves a stable photothermal efficiency around 94% under one sun when treating synthetic seawater with a salinity of 3.5 wt.%. Under outdoor conditions, it can produce 2.2 L m−2 of freshwater per day from real seawater, which is sufficient for individual drinking needs. This kind of biomimetic solar distillation devices have demonstrated great capability in clean water production and passive salt collection to tackle global water and environmental challenges

Pore-scale physics of ice melting within unconsolidated porous media revealed by non-destructive magnetic resonance characterization

Abstract Melting of ice in porous media widely exists in energy and environment applications as well as extraterrestrial water resource utilization. In order to characterize the ice-water phase transition within complicated opaque porous media, we employ the nuclear magnetic resonance (NMR) and imaging (MRI) approaches. Transient distributions of transverse relaxation time T 2 from NMR enable us to reveal the substantial role of inherent throat and pore confinements in ice melting among porous media. More importantly, the increase in minimum T 2 provides new findings on how the confinement between ice crystal and particle surface evolves inside the pore. For porous media with negligible gravity effect, both the changes in NMR-determined melting rate and our theoretical analysis of melting front confirm that conduction is the dominant heat transfer mode. The evolution of mushy melting front and 3D spatial distribution of water content are directly visualized by a stack of temporal cross-section images from MRI, in consistency with the corresponding NMR results. For heterogeneous porous media like lunar regolith simulant, the T 2 distribution shows two distinct pore size distributions with different pore-scale melting dynamics, and its maximum T 2 keeps increasing till the end of melting process instead of reaching steady in homogeneous porous media

Civic Engagement for Non-Profit Organizations

Civic Engagement is defined as an active involvement of individuals and business organizations in changing and improving communities (Lawrence and Weber, 2014). Why should individuals and organizations have to be involved in global citizenship? What is the purpose for the existence of non-government organizations? This project explores how non-profit organizations in Volusia County enhance the local population by contributing to the overall welfare of the affected people, the community, and the surrounding environment. The project was assigned in BA325 Social Responsibility and Ethics in Management class for Spring 2015. The three non-profit organizations selected are: Junior Achievement of Central Florida, the Salvation Army, and the Marine Science Center. Junior Achievement empowers young people to own their economic success and leads the youth to a bright future. The Salvation Army is an international movement to help all humanity needs without discrimination. The Marine Science Center of Ponce Inlet is set in place to conserve the natural wildlife local to the area and educate citizens on the importance of preservation. We are working in three groups of two students each. Upon conducting research and volunteering 10 hours each, we will provide analyses to include why these service-learning projects are important in business education, the training of future business leaders, and the impact on lives of society’s citizens. The project results will be communicated to the instructor Dr. Tamilla Curtis in an oral presentation at the end of the Spring semester

Synthesis of polydopamine coated tungsten oxide@ poly(vinylidene fluoride-co-hexafluoropropylene) electrospun nanofibers as multifunctional membranes for water applications

In this work, electrospun poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) nanofiber membranes were loaded with tungsten oxide (WO3) nanoparticles, surface coated with polydopamine (PDA) hierarchical structures, and tested in oil/water separation, photothermal water evaporation, and degradation of ampicillin. The electrospun nanofiber membranes (ENMs) consisted of three layers and the WO3 nanoparticles were incorporated into the top layer to increase their surface exposure. These layers were then heat-pressed for dimensional stability and surface coated with PDA hierarchical structures. Characterization was conducted using microscopic, goniometric, gravimetric, and spectroscopic methods. All ENMs displayed randomly oriented, smooth microporous structure and EDS mapping revealed a uniform distribution of WO3 nanoparticles on the nanofiber matrix. WO3-blended ENMs showed improved mechanical strength, higher UV/Vis absorption, and similar thickness as pristine ENM. PDA deposition has reduced the water contact angle of pristine PVDF-HFP membrane from 130.3 to 0 degrees, whereas, the underwater oil contact angle has increased from 55.8 to 159.7 degrees. The PDA-coated ENMs exhibited enhanced oil/water separation with 384.3 L m 2h- 1 (LMH) of flux and 97.6% oil rejection when filtered under gravity. Photothermal interfacial evaporation and ampicillin degradation tests also demonstrated the multifunctionality and exciting features of the fabricated membranes for a wide range of applications