Fabrication and characterization of nano-engineered membranes for oil-water separation

Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2013.Cataloged from PDF version of thesis.Includes bibliographical references (pages 55-58).The focus of this thesis is the design and testing of membranes for separation of water-in- oil (w/o) emulsions. A polycarbonate membrane treated with octadecyltrichlorosilane (OTS) is used to filter a 3 wt% w/o emulsion. The permeate is characterized to have no measurable water content by microscopy, dynamic light scattering (DLS) and differential scanning calorimetry (DSC). To extend this work, a method for fabricating an asymmetric polysulfone membranes is presented. The polysulfone membrane has the feature of allowing much higher flow rates for a given applied pressure. The research is largely motivated by a need for low cost methods for separating o/w and w/o emulsions. The largest source of wastewater is generated by the petroleum industry as o/w emulsions. Currently, industry has a number of methods for cleaning produced water. The inherent problem is that the smaller dispersed droplets are the more expensive they are to separate. In addition, the fundamental equations and models that govern interfacial phenomena and hydrophobic/oleophilic membranes are developed. In all, this work present a method for successfully separating oil droplets smaller than a micron from water by a novel methodology.by Brian R. Solomon.S.M

Separating Oil-Water Nanoemulsions using Flux-Enhanced Hierarchical Membranes

Membranes that separate oil-water mixtures based on contrasting wetting properties have recently received significant attention. Separation of nanoemulsions, i.e. oil-water mixtures containing sub-micron droplets, still remains a key challenge. Tradeoffs between geometric constraints, high breakthrough pressure for selectivity, high flux, and mechanical durability make it challenging to design effective membranes. In this paper, we fabricate a hierarchical membrane by the phase inversion process that consists of a nanoporous separation skin layer supported by an integrated microporous layer. We demonstrate the separation of water-in-oil emulsions well below 1 μm in size. In addition, we tune the parameters of the hierarchical membrane fabrication to control the skin layer thickness and increase the total flux by a factor of four. These simple yet robust hierarchical membranes with engineered wetting characteristics show promise for large-scale, efficient separation systems.MIT Energy InitiativeShell Oil CompanyMIT Energy Initiative (Fellowship

Steady‐state field‐aligned currents at Mercury

Magnetic field observations acquired in orbit about Mercury by the MESSENGER spacecraft demonstrate the presence in the planet's northern hemisphere of Birkeland currents that flow to low altitudes. Currents of density 10–30 nA/m2 flow downward at dawn and upward at dusk. Total currents are typically 20–40 kA and exceed 200 kA during disturbed conditions. The current density and total current are two orders of magnitude lower than at Earth. An electric potential of ~30 kV from dayside magnetopause magnetic reconnection implies a net electrical conductance of ~1 S. A spherical‐shell conductance model indicates closure of current radially through the low‐conductivity layers near the surface and by lateral flow from dawn to dusk through more conductive material at depth

The evolving SARS-CoV-2 epidemic in Africa: Insights from rapidly expanding genomic surveillance

INTRODUCTION Investment in Africa over the past year with regard to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) sequencing has led to a massive increase in the number of sequences, which, to date, exceeds 100,000 sequences generated to track the pandemic on the continent. These sequences have profoundly affected how public health officials in Africa have navigated the COVID-19 pandemic. RATIONALE We demonstrate how the first 100,000 SARS-CoV-2 sequences from Africa have helped monitor the epidemic on the continent, how genomic surveillance expanded over the course of the pandemic, and how we adapted our sequencing methods to deal with an evolving virus. Finally, we also examine how viral lineages have spread across the continent in a phylogeographic framework to gain insights into the underlying temporal and spatial transmission dynamics for several variants of concern (VOCs). RESULTS Our results indicate that the number of countries in Africa that can sequence the virus within their own borders is growing and that this is coupled with a shorter turnaround time from the time of sampling to sequence submission. Ongoing evolution necessitated the continual updating of primer sets, and, as a result, eight primer sets were designed in tandem with viral evolution and used to ensure effective sequencing of the virus. The pandemic unfolded through multiple waves of infection that were each driven by distinct genetic lineages, with B.1-like ancestral strains associated with the first pandemic wave of infections in 2020. Successive waves on the continent were fueled by different VOCs, with Alpha and Beta cocirculating in distinct spatial patterns during the second wave and Delta and Omicron affecting the whole continent during the third and fourth waves, respectively. Phylogeographic reconstruction points toward distinct differences in viral importation and exportation patterns associated with the Alpha, Beta, Delta, and Omicron variants and subvariants, when considering both Africa versus the rest of the world and viral dissemination within the continent. Our epidemiological and phylogenetic inferences therefore underscore the heterogeneous nature of the pandemic on the continent and highlight key insights and challenges, for instance, recognizing the limitations of low testing proportions. We also highlight the early warning capacity that genomic surveillance in Africa has had for the rest of the world with the detection of new lineages and variants, the most recent being the characterization of various Omicron subvariants. CONCLUSION Sustained investment for diagnostics and genomic surveillance in Africa is needed as the virus continues to evolve. This is important not only to help combat SARS-CoV-2 on the continent but also because it can be used as a platform to help address the many emerging and reemerging infectious disease threats in Africa. In particular, capacity building for local sequencing within countries or within the continent should be prioritized because this is generally associated with shorter turnaround times, providing the most benefit to local public health authorities tasked with pandemic response and mitigation and allowing for the fastest reaction to localized outbreaks. These investments are crucial for pandemic preparedness and response and will serve the health of the continent well into the 21st century

Advances in liquid repellent surfaces by anisotropic wetting and lubricant impregnation

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2016.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from student-submitted PDF version of thesis.Includes bibliographical references (pages 119-130).Recent advances in creating liquid-repellent surfaces have focused on decreasing the interaction between a liquid and a solid surface by modifying the surface's chemistry and cleverly designing its geometry on nano- and millimetric length scales. This thesis explores two advances to control a liquid's interaction with a surface: 1) deflectable structures that influence anisotropic wetting properties and 2) lubricant impregnated surfaces comprised of a porous surface and liquid lubricant. Through experimental characterization the mechanism by which deflectable scales on a butterfly wing cause anisotropic drop repellency is investigated. The design of lubricant impregnated surfaces is reviewed and expanded by demonstrating their potential for drag reduction and incorporation into electrochemical systems. The first part of this thesis characterizes how the unique structure of a butterfly's wings contributes to its anisotropic wetting properties. In particular, a water drop placed on the surface of a butterfly's wing will easily roll away from the butterfly's body, but will roll off at much higher angles toward the body. This phenomenon is observed and quantified using environmental electron microscopy and confocal microscopy. A theory that takes into account the deflection of the butterfly's scales explains the observed anisotropy and correlates with the observed roll-off on a wide range of butterfly species. Such deflectable surface structures offer a new way to tune the wetting properties of a surface. The second part of this thesis reviews and expands on lubricant impregnated surfaces. It explains how to achieve a stable lubricant impregnated surface and discusses its basic features including the wetting ridge and lubricant cloak. Motivated by the slippery nature of these surfaces, the potential of lubricant impregnated surfaces to reduce drag is detailed. A scaling model that incorporates the viscosity of the lubricant and elucidates the dependence of drag reduction on the ratio of the viscosity of the working fluid to that of the lubricant is presented. The model is validated by experiments conducted in a cone and plate rheometer where a drag reduction of 16% is measured. Finally, lubricant impregnated surfaces are applied to electrochemical systems. Measurements quantify how lubricant impregnated surfaces improve the flowability of a non- Newtonian lithium polysulfide flow electrode in which electronic conductivity is imparted by carbon particles. A framework for the design of such surfaces for a wide range of flow electrode solvents is used to incorporate lubricant impregnated surfaces into a Gravity Induced Flow Cell (GIFCell) prototype to enable the flow of highly conductive suspension.by Brian R. Solomon.Ph. D

Enhancing the Performance of Viscous Electrode-Based Flow Batteries Using Lubricant-Impregnated Surfaces

Redox flow batteries are a promising technology that can potentially meet the large-scale grid storage needs of renewable power sources. Today, most redox flow batteries are based on aqueous solutions with low cell voltages and low energy densities that lead to significant costs from hardware and balance-of-plant. Nonaqueous electrochemical couples offer higher cell voltages and higher energy densities and can reduce system-level costs but tend toward higher viscosities and can exhibit non-Newtonian rheology that increases the power required to drive flow. This work uses lubricant-impregnated surfaces (LIS) to promote flow in electrochemical systems and outlines their design based on interfacial thermodynamics and electrochemical stability. We demonstrate up to 86% mechanical power savings at low flow rates for LIS compared to conventional surfaces for a lithium polysulfide flow electrode in a half-cell flow battery configuration. The measured specific charge capacity of ∼800 mAh/(g·S) is a 4-fold increase over previous work

Enhancing the Performance of Viscous Electrode-Based Flow Batteries Using Lubricant-Impregnated Surfaces

Redox flow batteries are a promising technology that can potentially meet the large-scale grid storage needs of renewable power sources. Today, most redox flow batteries are based on aqueous solutions with low cell voltages and low energy densities that lead to significant costs from hardware and balance-of-plant. Nonaqueous electrochemical couples offer higher cell voltages and higher energy densities and can reduce system-level costs but tend toward higher viscosities and can exhibit non-Newtonian rheology that increases the power required to drive flow. This work uses lubricant-impregnated surfaces (LIS) to promote flow in electrochemical systems and outlines their design based on interfacial thermodynamics and electrochemical stability. We demonstrate up to 86% mechanical power savings at low flow rates for LIS compared to conventional surfaces for a lithium polysulfide flow electrode in a half-cell flow battery configuration. The measured specific charge capacity of ∼800 mAh/(g·S) is a 4-fold increase over previous work