Development of Small-scale Two-stage Photovoltaic-photothermal Humidification-dehumidification Desalination System

Air bubble has been proved that it can increase evaporation area and coefficient of mass transfer and heat transfer. Two-stage evaporation system can indirectly increase the contact area of water and vapor, reduce the volume of single evaporation system, and can also combine the multiple systems flexibly. So a new type of small scale two-stage photovoltaic-photothermal humidification-dehumidification (HDH) desalination system is designed, and the relationship between solar radiation and temperature is measured, and the water production capability of the system is investigated. The effect of water temperature, ambient temperature, air flow rate and air temperature on desalination performance is also investigated. The results showed that the rate of water production is positively correlated with sea water temperature, ambient temperature, gas flow rate and air temperature. And the gas temperature is positively correlated with the solar radiation intensity. When the ambient temperature is higher than 25 ℃, the cumulative amount of irradiation is 22.3 MJ/m2, the cumulative water production is 19.2 L/d, and 6.4 L/( m2∙d), the thermal efficiency is 0.66. The cost of water produced through the designed HDH system is 0.08 $/L

Fouling mitigation strategies for different foulants in membrane distillation

Providing clean water to a rapidly growing population is an issue that is currently getting lots of attention to offer a sustainable solution for water scarcity. Membrane distillation (MD) is one of the latest technologies that provides great potential in water treatment. Even though there is a tremendous amount of research done during the past two decades on membrane distillation, the long-term use of this process is still restricted by membrane fouling. Membrane Fouling can be defined as the accumulation of various materials in the pores or surface of the membrane that affect permeate's quantity and quality. This review highlights the recent observations on various foulants in MD process. Moreover, different fouling mechanisms of inorganic fouling, organic fouling, biological fouling, and colloidal fouling were investigated for better understanding and prevention of membrane fouling. In order to achieve a sustainable MD process, various techniques to mitigate fouling were discussed comprehensively including pre-treatment processes and cleaning methods. The benefits and disadvantages of these approaches have been investigated and reviewed in order to provide an overall understanding of fouling minimization in membrane distillation process. Fouling mitigation strategies have been suggested for different foulants in membrane distillation

Models and Analysis of Vocal Emissions for Biomedical Applications

The Models and Analysis of Vocal Emissions with Biomedical Applications (MAVEBA) workshop came into being in 1999 from the particularly felt need of sharing know-how, objectives and results between areas that until then seemed quite distinct such as bioengineering, medicine and singing. MAVEBA deals with all aspects concerning the study of the human voice with applications ranging from the neonate to the adult and elderly. Over the years the initial issues have grown and spread also in other aspects of research such as occupational voice disorders, neurology, rehabilitation, image and video analysis. MAVEBA takes place every two years always in Firenze, Italy

Real time measurement of oxygen by integrating a clark sensor with low cost printed circuit board technology and solid electrolyte membrane

A prototype of a miniaturized Clark type electrochemical oxygen sensor integrated with a 3D printed in vitro cell culturing platform is designed and developed for the purpose of monitoring the cellular oxygen consumption by the solution flowing through the cultured cells on the platform. Oxygen respiration indicates a cell's metabolic activity, so by measuring a chemical's oxygen content as it passes through a cell chamber, we can measure that chemical's potential effectiveness. This miniature micro sensor is designed and fabricated on a printed circuit board for the first time and integrated with a solid electrolyte membrane and 3D printed cell culturing platform to ensure robustness, low manufacturing cost and good electrical conductivity for sensing. Hence the sensor is aimed at enabling the pharmaceutical industry to rapidly test chemical products on animal and cancer cells; and has been designed to be low cost and suitable for mass production. The presented oxygen sensor configuration consists of two identical series of working, reference and counter microelectrodes. The solid polymer electrolyte membrane, Nafion (perfluorosulfunic acid membrane, DuPont Company) removed requirement for extra humidification and increased the shelf life of the sensor. The sensitivity of the oxygen sensor was tested in different oxygen concentration in gas and liquid states and was calibrated with measurements from a Portable Multi-Gas analyzer and a dissolved oxygen analyzer. The prototype can detect the small changes in oxygen concentration in the range of 0 to 5 μA current and has a response time of less than 5 seconds

Reduction in salt deposition on carbon nano-tube immobilized membrane during desalination via membrane distillation

As water scarcity increases globally under the stresses of increasing demand, aquifer depletion, and climate change, the market for efficient desalination technologies has grown rapidly to fill the void. One such developing technology, membrane distillation (MD), has found much interest in the scientific community. MD has also been powered by solar energy and waste heat resources because it can be operated at relatively low temperatures. Recent studies indicate that MD could potentially achieve the efficiencies of state-of-the-art mature thermal desalination technologies, although additional engineering and scientific challenges must first be overcome. MD can be used to treat high salinity water where the salt concentration is high. The aim of this research is to better understand and provide solutions for one of the major challenges being faced by high concertation applications of MD, more specifically membrane fouling. Through experiments, this thesis compares different heating systems in MD, namely conventional and microwave heating, and their effect on fouling. It also looks at carbon nanotube immobilized membrane, and studies the effect of carbon nanotubes on fouling. In this research MD is carried out using highly concentrated aqueous calcium carbonate, calcium sulfate and barium sulfate solutions, and it is observed that the decline in flux over time is significantly less in microwave induced membrane distillation (MIMD). As compared to conventional heating, the salt deposition on the membrane is 50-79 % less during microwave heating. The second and third part of this research shows the effects of adding different antiscalant materials to the feed side of the experiment to investigate the fouling behavior under fixed operating parameters such as feed concentration, temperature, and feed flowrate. The results show a strong influence of using antiscalant materials on the highly concentrated salt solutions and on produced water from hydraulic fracturing as well. It is observed that using carbon nanotube based membranes and antiscalants, the fouling behavior could be reduced and water vapor flux in MD can be enhanced. Results also show that the presence of CNTs facilitates the removal of deposited salts by washing and the CNIM regains 97% of its initial water flux, whereas the unmodified polypropylene only regains 85% of the original value

Assessment of the impact of atmospheric pollutants on bacteria viability by an atmospheric simulation chamber

The aim of the PhD project was to make possible systematic studies of the bio-aerosols behavior in different atmospheric conditions, with the final goal to assess the link between pollution levels and bio-aerosol dispersion and impact. The research has been carried out at ChAMBRe (Chamber for Aerosol Modelling and Bio-aerosol Research), a 2.3 m3 stainless steel atmospheric simulation chamber. Experiments conducted inside confined artificial environments, such as the Atmospheric Simulations Chambers (ASCs), where atmospheric conditions and composition are controlled, can provide valuable information on bio-aerosols viability and their interaction with other atmospheric constituents. The first phase of the PhD project was dedicated to the characterization of the chamber, the related instrumentation and the design and development of the experimental set-up. An experimental protocol for chamber studies on bio-aerosols was developed and thoroughly tested with two bacteria model strains (B. subtilis and E. coli). An intense effort has been dedicated to fully characterize the performance of three different nebulization systems specifically designed for bioaerosol applications to assess their application in experiments at ASCs. A WIBS-NEO provides the size-segregated, real-time monitoring of the total bio-aerosol concentration inside the chamber. With a clean atmosphere maintained inside ChAMBRe, the ratio between injected and extracted viable bacteria turned out to be reproducible at 11\u2009% and 13% level with E. coli and B. subtilis respectively. After assessing this way the reproducibility and sensitivity of the whole experimental procedure, the first tests to explore the possible correlation between bacteria viability and air quality were carried out. The two bacteria models, B. subtilis and E. coli, were subjected to high concentrations of nitrogen oxides and soot particles, two of the most common pollutants emitted by anthropogenic sources

Cesium dihydrogen phosphate as electrolyte for intermediate temperature proton exchange membrane water electrolysis (IT-PEMWE)

PhD ThesisIn this work the potential application of CsH2PO4 as intermediate temperature electrolyte for Proton Exchange Membrane Water Electrolysis (PEMWE) was studied. This material, from the phosphate-based solid acid family, was previously reported as a promising electrolyte for intermediate temperature PEM fuel cells although no study as electrolyte in a PEMWE system had been carried out before. The physico-chemical properties of phosphate-based solid acids in terms of structure and morphology were investigated and their thermal stability evaluated. Proton conductivity at the intermediate temperature range (150 – 300 °C) was measured and the influence of humidity on the stability of CsH2PO4 in terms of dehydration and water solubility determined. Different approaches for the fabrication of CsH2PO4-based membranes are proposed in order to improve the mechanical properties and reduce the thickness and ohmic resistance of the electrolyte. Membrane fabrication techniques including casting of polymer/CsH2PO4 composites, glass-fibre reinforcement, polymer doping or electrospinning were developed and the resulting membranes characterised in terms of structure, proton conductivity and mechanical stability. The compatibility of CsH2PO4 with IrO2 was evaluated and compared to standard acid electrolyte solutions in a three-electrode half-cell in the low temperature range (40 – 80 °C). The performance of IrO2 towards oxygen evolution reaction (OER) in a CsH2PO4 concentrated solution exhibited poor activity, which was attributed to a high kinetic activation caused by the high pH and high phosphate concentration in solution. Finally the performance of CsH2PO4 as solid-state electrolyte in the electrolysis cell was evaluated at intermediate temperatures (235 – 265 °C). Electrodes were optimised in terms of catalyst and ionomer loading for an intimate catalyst/electrolyte contact and characterised by cyclic voltammetry. The electrolysis system was characterised by quasi-steady polarisation curves and electrochemical impedance spectroscopy. The maximum performance obtained by a Pt/CsH2PO4/IrO2 MEA system at 265 °C was 20 mA cm-2 at 1.90 V. This low activity, in good agreement with the results obtained in the half-cell, was mainly attributed to kinetic losses generated in the CsH2PO4/IrO2 interface. The low acidity of the electrolyte is considered to affect the active oxidation state of iridium, Abstract ii creating a non-hydrated oxide layer, which influenced negatively to the performance of the electrolyser. It is therefore concluded that despite the promising results reported for CsH2PO4 as electrolyte in intermediate temperature fuel cells, this material, and presumably the rest phosphate-based solid acids, are not to be considered as potential electrolytes for PEM water electrolysers.European Commission for their financial support through SUSHGEN (Sustainable Hydrogen Generation) project under the 7th framework Marie Curie ITN progra

Studies on Poly(N,N-dimethylaminoethyl methacrylate) Composite Membranes for Gas Separation and Pervaporation

Membrane-based acid gas (e.g., CO2) separation, gas dehydration and humidification, as well as solvent dehydration are important to the energy and process industries. Fixed carrier facilitated transport membranes can enhance the permeation without compromising the selectivity. The development of suitable fixed carrier membranes for CO2 and water permeation, and understanding of the transport mechanism were the main objectives of this thesis. Poly(N,N-dimethylaminoethyl methacrylate) (PDMAEMA) composite membranes were developed using microporous polysulfone (PSF) or polyacrylonitrile (PAN) substrates. The PDMAEMA layer was crosslinked with p-xylylene dichloride via quaternization reaction. Fourier transform infrared, scanning electron microscopy, adsorption tests, and contact angle measurements were conducted to analyze the chemical and morphological structure of the membrane. It was shown that the polymer could be formed into thin dense layer on the substrates, while the quaternary and tertiary amino groups in the side chains of PDMAEMA offered a high polarity and hydrophilicity. The solid-liquid interfacial crosslinking of PDMAEMA led to an asymmetric crosslinked network structure, which helped minimize the resistance of the membrane to the mass transport. The interfacially formed membranes were applied to CO2/N2 separation, dehydration of CH4, gas humidification and ethylene glycol dehydration. The membranes showed good permselectivity to CO2 and water. For example, a CO2 permeance of 85 GPU and a CO2/N2 ideal separation factor of 50 were obtained with a PDMAEMA/PSF membrane at 23oC and 0.41 MPa of CO2 feed pressure. At 25oC, the permeance of water vapor through a PDMAEMA/PAN membrane was 5350 GPU and the water vapor/methane selectivity was 4735 when methane was completely saturated with water vapor. On the other hand, the relative humidity of outlet gas was up to 100 % when the membrane was used as a hydrator at 45oC and at a carrier gas flow rate of 1000 sccm. For used for dehydration of ethylene glycol at 30oC, the PDMAEMA/PSF membrane showed a permeation flux of ~1 mol/(m2.h) and a permeate concentration of 99.7 mol% water at 1 mol% water in feed. This work shows that the quaternary and tertiary amino groups can be used as carriers for CO2 transport through the membrane based on the weak acid-base interaction. In the presence of water, water molecules in the membrane tend to form a water "path" or water "bridge" which also help contribute to the mass transport though the membrane. In addition, CO2 molecules can be hydrated to HCO3-, which reaction can be catalyzed by the amino groups, the hydrated CO2 molecules can transport through the water path as well as the amino groups in the membrane. On the other hand, for processes involving water (either vapor or liquid) permeation, the amino groups in the membrane are also helpful because of the hydrogen bonding effects