This thesis focuses on the development of two new applications using ion concentration polarization (ICP): an out-of-plane microfluidic approach for water desalination and a method for concentration and transportation of charged analytes in paper-based biomedical diagnostic device. In the first work, we present an out-of-plane desalination approach using ICP. A depletion boundary separates salt ions and purified water into distinct vertically stacked layers. The out-of-plane design enables multiplexing in three dimensions, providing the functional density required for practical applications. The second work demonstrates an active control mechanism of target analytes in paper using ICP. Both external devices (with all functional units on one side of paper) and integrated paper microfluidic devices (by embedding all functional units in paper) were developed to concentrate and transport charged analyte molecules in the paper. We also demonstrate a new fabrication method of nanofluidic and hydrophobic barriers (nanoporous membrane patterning) in paper microfluidic device.

Carbon has been used electrochemically in various forms for water treatment and the carbon aerogel is one of them. Carbon Aerogels (CA) are used as electrodes due to their high surface capacity and high electrical conductivity. They are also known as Carbon Nanofoams (CNF). CA electrodes attract oppositely charged ions that are nearby. This concept is known as Capacitive De-Ionization (CDI). The use of CA in CDI for water purification is well documented, but not much work has been done on regeneration of CA electrodes. Once saturated, these electrodes lose their ability to adsorb additional ions and it must be restored by regeneration. If they cannot be regenerated, they would need to be replaced, which would greatly increase the cost of the treatment they are expensive. The goal of this study is to obtain data to define optimal regeneration conditions and to develop predictive capability by examining desorption behavior of adsorbed ions on CA electrodes. This study focuses on desorption of adsorbed ions and regeneration of CA. Various experiments were conducted to explore the effects on regeneration of CA of shorting of electrodes, change of polarity of electrodes, flow speed of water over CA electrodes, and temperature of regeneration water. The optimal combination of experimental variables was identified and was used for remaining experiments that tested the effect of size, charge and mass of adsorbed ions on regeneration of CA. Also, the effect of thickness of CA and its pore size on regeneration of CA was studied. Results indicated that application of reverse potential for the first few minutes of the total regeneration time provided the greatest regeneration. Longer application of reverse potential did not result in higher regeneration. The regeneration behavior when no potential applied with and without shorting was as expected. Application of reverse potential with variable temperature or variable flow speed of water over CA surfaces provided results that were different from the ones that were obtained with no potential being applied with or without shorting of electrodes.

0.7nm single wall carbon nanotubes have been synthesized within VPI-5 zeolite channels with sucrose as carbon precursor. VPI-5 molecular sieves are synthesized hydrothermally under conventional heating. X-ray powder diffraction, micro raman, scanning electron microscope (SEM), transmission electron microscope (TEM), Thermogravimetric analysis have been used to investigate the structure of zeolite and thermal decoposition process of carbon precursors. 0.4nm single wall carbon nanotubes have also been fabricated within AlPO4-5 nanopores. A key challenge is to produce high yield single wall carbon nanotubes with uniform diameter. In order to improve the carbon nanotube yield, different organic precursors are employed. Although the problem is still the repetition and low yield of CNTs, it is still an improvement for 0.7nm SWNTs synthesis with the new template prolysis method. The novel multilayer conductor/insulator/conductor structures have been fabricated. This structure might find potential application in DNA sequential reactions because each layer might be individually addressed with voltage. When bias is applied to the conductive layer, it can be chemically functionalized, which leads to membrane pore with multiple reaction sequences when the molecule traverses the membrane reactor. In this thesis, Carbon/polymer/carbon system and copper/polymer system will be introduced. O2 RIE was used to expose the edge of carbon/polymer/carbon structure. However, the conductivity of carbon layer is not high enough for electroplating. Copper pores etched by FeCl3 solution shows good conductivity, and can be electroplated with metal nanoparticles.

The pollution of South Africa’s water resources puts a strain on an already stressed natural resource. One of the main pollution sources is industrial effluents such as acid mine drainage (AMD) and other mining effluents. These effluents usually contain high levels of acidity, heavy metals and sulphate. A popular method to treat these effluents before they are released into the environment is lime neutralisation. Although this method is very effective to raise the pH of the effluent as well as to precipitate the heavy metals, it can only partially remove the sulphate. Further treatment is required to reduce the sulphate level further to render the water suitable for discharge into the environment. A number of sulphate removal methods are available and used in industry. These methods can be divided into physical (membrane filtration, adsorption/ion exchange), chemical (chemical precipitation) and biological sulphate reduction processes. A literature study was conducted in order to compare these different methods. The ABC (Alkali – Barium – Calcium) Desalination process uses barium carbonate to lower the final sulphate concentration to an acceptable level. Not only can the sulphate removal be controlled due to the low solubility of barium sulphate, but it can also produce potable water and allows valuable by–products such as sulphur to be recovered from the sludge. The toxic barium is recycled within the process and should therefore not cause additional problems. In this study the sulphate removal process, using barium carbonate as reactant, was investigated. Several parameters have been investigated and studied by other authors. These parameters include different barium salts, different barium carbonate types, reaction kinetics, co–precipitation of calcium carbonate, barium–to–sulphate molar ratios, the effect of temperature and pH. The sulphate removal process was tested and verified on three different industrial effluents. The results and conclusions from these publications were used to guide the experimental work. A number of parameters were examined under laboratory conditions in order to find the optimum conditions for the precipitation reaction to take place. This included mixing rotational speed, barium–to–sulphate molar ratio, initial sulphate concentration, the effect of temperature and the influence of different barium carbonate particle structures. It was found that the reaction temperature and the particle structure of barium carbonate influenced the process significantly. The mixing rotational speed, barium–to–sulphate dosing ratios and the initial sulphate concentration influenced the removal process, but not to such a great extent as the two previously mentioned parameters. The results of these experiments were then tested and verified on AMD from a coal mine. The results from the literature analysis were compared to the experiments conducted in the laboratory. It was found that the results reported in the literature and the laboratory results correlated well with each other. Though, in order to optimise this sulphate removal process, one has to understand the sulphate precipitation reaction. Therefore it is recommended that a detailed reaction kinetic study should be conducted to establish the driving force of the kinetics of the precipitation reactions. In order to upgrade this process to pilot–scale and then to a full–scale plant, continuous reactor configurations should also be investigated. The sulphate removal stage in the ABC Desalination Process is the final treatment step. The effluent was measured against the SANS Class II potable water standard and was found that the final water met all the criteria and could be safely discharged into the environment. / Thesis (M.Ing. (Chemical Engineering))--North-West University, Potchefstroom Campus, 2012.

The pollution of South Africa’s water resources puts a strain on an already stressed natural resource. One of the main pollution sources is industrial effluents such as acid mine drainage (AMD) and other mining effluents. These effluents usually contain high levels of acidity, heavy metals and sulphate. A popular method to treat these effluents before they are released into the environment is lime neutralisation. Although this method is very effective to raise the pH of the effluent as well as to precipitate the heavy metals, it can only partially remove the sulphate. Further treatment is required to reduce the sulphate level further to render the water suitable for discharge into the environment. A number of sulphate removal methods are available and used in industry. These methods can be divided into physical (membrane filtration, adsorption/ion exchange), chemical (chemical precipitation) and biological sulphate reduction processes. A literature study was conducted in order to compare these different methods. The ABC (Alkali – Barium – Calcium) Desalination process uses barium carbonate to lower the final sulphate concentration to an acceptable level. Not only can the sulphate removal be controlled due to the low solubility of barium sulphate, but it can also produce potable water and allows valuable by–products such as sulphur to be recovered from the sludge. The toxic barium is recycled within the process and should therefore not cause additional problems. In this study the sulphate removal process, using barium carbonate as reactant, was investigated. Several parameters have been investigated and studied by other authors. These parameters include different barium salts, different barium carbonate types, reaction kinetics, co–precipitation of calcium carbonate, barium–to–sulphate molar ratios, the effect of temperature and pH. The sulphate removal process was tested and verified on three different industrial effluents. The results and conclusions from these publications were used to guide the experimental work. A number of parameters were examined under laboratory conditions in order to find the optimum conditions for the precipitation reaction to take place. This included mixing rotational speed, barium–to–sulphate molar ratio, initial sulphate concentration, the effect of temperature and the influence of different barium carbonate particle structures. It was found that the reaction temperature and the particle structure of barium carbonate influenced the process significantly. The mixing rotational speed, barium–to–sulphate dosing ratios and the initial sulphate concentration influenced the removal process, but not to such a great extent as the two previously mentioned parameters. The results of these experiments were then tested and verified on AMD from a coal mine. The results from the literature analysis were compared to the experiments conducted in the laboratory. It was found that the results reported in the literature and the laboratory results correlated well with each other. Though, in order to optimise this sulphate removal process, one has to understand the sulphate precipitation reaction. Therefore it is recommended that a detailed reaction kinetic study should be conducted to establish the driving force of the kinetics of the precipitation reactions. In order to upgrade this process to pilot–scale and then to a full–scale plant, continuous reactor configurations should also be investigated. The sulphate removal stage in the ABC Desalination Process is the final treatment step. The effluent was measured against the SANS Class II potable water standard and was found that the final water met all the criteria and could be safely discharged into the environment. / Thesis (M.Ing. (Chemical Engineering))--North-West University, Potchefstroom Campus, 2012.

South Africa is on a path of dramatically increasing its energy supplying capabilties. Eskom (the main utility supplying electricity to the national grid) recently announced that future power station technologies will focus on renewable energy and nuclear power. This is done in an effort to reduce South Africa’s dependance on burning fossil-fuels and thereby decreasing CO2 emissions and other harmful gases. This, together with the fact that there are a lot of fresh water scarce areas especially along the Eastern Cape coast of South Africa, is what inspired this study. This study investigates the use of a 200 MWth High Temperature Reactor (HTR) for cogeneration purposes. Heat from the reactor is utilised for electricity generation (Rankine cycle) and process heat (desalination). Two desalination concepts were evaluated thermodynamically and economically, namely Multi-Effect Distillation (MED) and Reverse Osmosis (RO). Computer software, Engineering Equation Solver (EES), was used to simulate different cycle configurations, where the heat available in the condenser was increased successively. The coupling of the two desalination technologies with a HTR was compared and it was found that a RO plant produces nearly twice as much water while sending the same amount of electricity to the grid (compared to coupling with MED). Coupling options were investigated and each simulation model was optimised to deliver maximum output (power and water). The best configuration was found to be the coupling of a HTR with a RO plant producing 86.56 MW generator power. This is equal to 2077 MWh/day. Using 332 MWh/day for desalination through RO, delivers 73 833 m3/day fresh water and results in 1745 MWh/day sent to the grid. This scenario is the best option from a thermodynamic and economic point of view. From an investment point of view, it will produce an Internal Rate of Return (IRR) of 10.9 percent and the Net Present Value (NPV) is calculated to be R 2,486,958,689. The results and analysis for the different cycle configurations are presented in such a way that an easy comparison can be made. / Thesis (M.Ing. (Nuclear Engineering))--North-West University, Potchefstroom Campus, 2011

Most common inorganic foulants in RO processes operating on brackish water are calcium carbonate, calcium sulphate and silica. However, silica fouling is the recovery limiting factor in RO system. Silica chemistry is complex and its degree of fouling strongly depends on the silica solubility and its polymerization under different operating conditions of RO process. In several studies carried out in batch and dynamic tests, the presence of polyvalent cations and supersaturation of silica in solutions were found to be the important factors (apart from pH and temperature) that affected the rate of silica polymerization and its induction period. Agitation did increased silica solubility; however, its effect was negligible in presence of polyvalent cations. Alkalization of water solution by coagulants particularly sodium hydroxide was found suitable for silica removal during pretreatment. The presence of magnesium in solution played a key role in silica removal mostly by the mechanism of adsorption to the metal hydroxide. The options of inline mixing (high agitation) for 5 to 10 minutes and microfiltration before RO were found suitable for silica pretreatment. During dynamic tests, the most dominant mechanism for salt deposition (mostly CaSO4) was particulate type in high concentration water solution; while crystallization fouling was the prevailing mechanism of deposition (mostly CaCO3 and silica) in low concentration solution. Silica showed significant effect on size and shape of inorganic salt crystals during coprecipitation. Moreover, the presence of common antiscalants promoted silica fouling. This important finding recommends an extra caution while using antiscalants in case feed water contains silica to a level that can attain saturation near membrane during RO process. A model was developed to predict the silica fouling index (SFI) based on the experimental data for induction period of silica polymerization. The model takes into account the effect of polyvalent cations and concentration polarization near membrane during RO process. It provides a conservative basis for predicting the maximum silica deposition in RO process at the normal operating conditions. A generalised correlation, which was developed for determination of the mass transfer coefficient in RO process, incorporated the effect of temperature change that is usually not considered in previous correlations. A correlation for reduction of silica content in feed water, down to a safe limit of 15 ppm for RO process, was also formulated and validated by the experimental results.

Water is a vital element of agriculture. Almost 75% of the world's water resources are used for farm irrigation. Using greenhouses in agriculture provides a good environment for plant growth and reduces water consumption. Desalination to obtain freshwater from seawater or brackish water has been used in the arid costal regions and areas that have encountered water shortages. Solar desalination systems integrated into greenhouses have been considered for fresh water production to satisfy their water demand. Two main types of greenhouse integrated desalination systems are used, namely, solar stills and greenhouse-integrated humidification-dehumidification type solar systems. The main objective of this project is to carry out a thermodynamic analysis and a comparison of solar stills and humidification-dehumidification type desalination units. The basic principles, components, types, advantages and disadvantages of solar stills and humidification-dehumidification type greenhouse integrated desalination systems were investigated in detail. A conventional single basin type solar still that includes a basin and a symmetrical tilted condensing cover (greenhouse roof), and a humidification- dehumidification desalination unit that consists of two evaporators and one condenser were selected for detailed analysis. In order to carry out the thermal analysis, some important data such as plant transpiration and evaporation, solar radiation and indoor conditions of the greenhouse were determined. The thermal analysis was based on tomato production. Typical year ambient air temperature, relative humidity, and wind velocity values were taken from TRNSYS 16 for Adelaide conditions. In order to provide a good environment for the tomato crops, the internal conditions of the greenhouse were selected in the range 15-29oC temperature and 60-80% relative humidity. Detailed mathematical thermal models of both conventional solar stills and the new humidification-dehumidification type systems were simulated and the fresh water production of both systems was evaluated by means of MATLAB 7.8. The results were compared with previous experimental results. The results demonstrated that even if the whole roof area is used, the required fresh water supply cannot be produced in the months of May, June and July by the simple solar still system, whereas adequate amounts of fresh water can be produced throughout the year by means of humidification-dehumidification type system. On the other hand, the annual water production of the simple solar still system and humidification-dehumidification type system were determined as 308.5 and 260 m3/year respectively. The thesis also considers the option of water storage for providing water requirement of the greenhouse plants. The parameters that affect the fresh water requirement of the both systems were also considered and their impact evaluated. The effects of the desalination system on the internal environment of the greenhouse were also considered. It was revealed from the results that the use of the solar still system during the period from April to October causes unsuitable greenhouse conditions for the greenhouse crops whilst appropriate conditions for the greenhouse crops were achieved throughout the year in the case of the humidification-dehumidification type system. On these and other grounds, the humidification-dehumidification type system was found more suitable for the given greenhouse and climatic conditions. / Thesis (MEng(MechanicalEngineering)--University of South Australia, 2010

Le travail décrit dans cette thèse couvre une étude fondamentale sur des canaux artificiels d'eau et sur des matériaux membranaires incorporant ces canaux. Structuré en quatre chapitres, la thèse commence par une présentation de l'état de l’art sur les systèmes biomimétiques de transport d'eau et des membranes biomimétiques. Au centre de tous ces travaux de recherche sont les protéines biologiques hautement efficaces et sélectives, les Aquaporines. Le deuxième chapitre présente les canaux artificiels d'eau à base d'imidazole-quartet. Les similitudes structurelles et fonctionnelles avec les Aquaporines sont discutées et caractérisées par plusieurs méthodes expérimentales. Les structures à l'état solide obtenues à partir de monocristaux présentent une organisation très similaire des I-quartets avec leurs homologues biologiques. Le biomimétisme fonctionnel du transport de l'eau a été démontré par des expériences cinétiques de transport à travers des systèmes vésiculaires. Le mécanisme de translocation de l'eau et l'organisation confinée dans des environnements lipidiques a été confirmé par des simulations dynamiques moléculaires, tandis que la preuve physique de l'eau orientée dipolaire dans les canaux intégrés aux lipides a été fournie par des expériences de spectroscopie IR polarisée. Le troisième chapitre présente de nouveaux canaux d'eau artificiels en utilisant une stratégie d'auto-assemblage. De nouveaux composés à base de diol, de tétrazacrown et de tryarilamine capables de transporter l'eau sont décrits. Le dernier chapitre décrits le passage du niveau moléculaire aux matériaux membranaires macroscopiques incorporant des canaux d'eau artificiels. Deux configuration membranaires différentes ont été décrites: des membranes en couche mince par l'incorporation de nanoparticules à base d'imidazole dans des polymères de polyamide et des membranes de la cellulose régénérée chimiquement greffée par des monomères de canaux d'eau artificiels. Les membranes ont été caractérisées par diverses méthodes d'imagerie et d'analyse et leurs performances ont été testées dans des expériences d'osmose inverse et de filtration d'osmose directe. La thèse est conclue avec une partie de conclusion générale, comprenant des perspectives pour les développements futurs. / The work described in this thesis covers an in depth fundamental study of artificial water channels and of membrane materials incorporating these channels. Structured in four chapters, the thesis begins with a presentation of the state of the art in the field of biomimetic systems and membranes for water transport. The center of the described research work is the family of highly efficient and selective biological water transporter proteins, the Aquaporins. The second chapter presents the description of imidazole-quartet supramolecular artificial water channels. Structural and functional similarities with Aquaporins are discussed and based on several experimental methods. Single-solid state structures present very similar organization of confined water wires as found in their biological counterparts. Functional mimicry of water transport has been proved through stopped flow experiments in vesicular systems. Further characterization concerning water translocation mechanism and confined organization in lipid environments have been obtained through molecular dynamic simulations, while physical evidence of dipolar oriented water in lipid embedded channels has been provided by sum frequency generation experiments. The third chapter presents novel artificial water channels. New diol, tetrazacrown and tryarilamine based compounds have been described, with a main focus on design, synthesis, self-assembly and water transport properties. The last chapter makes the transition from the molecular systems to macroscopic membrane materials incorporating artificial water channels. Two different approaches have been described: thin film nanocomposite membranes based on the incorporation of imidazole-quartet nanoparticles in polyamide polymers and chemically grafted regenerated cellulose membrane through the use of custom monomers for the obtaining of artificial water channels. The membranes have been characterized through various imaging and analytical methods and their performances have been tested in reverse and forward osmosis experiments. The thesis is concluded with a general conclusion part, including perspectives for future developments.

Submitted by Maria Medeiros (maria.dilva1@ufcg.edu.br) on 2018-09-14T11:45:03Z No. of bitstreams: 1 ARLEIDE RICARTE DE OLIVEIRA - TESE (PPGEP) 2007.pdf: 4819651 bytes, checksum: 1cc38913961211c387807eb81998c764 (MD5) / Made available in DSpace on 2018-09-14T11:45:03Z (GMT). No. of bitstreams: 1 ARLEIDE RICARTE DE OLIVEIRA - TESE (PPGEP) 2007.pdf: 4819651 bytes, checksum: 1cc38913961211c387807eb81998c764 (MD5) Previous issue date: 2007-08-31 / Capes / A falta de água potável em algumas localidades do mundo, mais precisamente no semi-árido, é um problema de caráter secular, agravado pela poluição, distribuição irregular e existência de águas subterrâneas de utilização bastante limitada por causa dos altos índices de salinidade. Por outro lado, essas regiões possuem um grande potencial de irradiação solar que favorece a utilização de painéis fotovoltaicos, principalmente em locais distante da rede elétrica. Visando melhorar a qualidade de vida e minimizar o problema da falta de água potável nessas regiões, esse trabalho tem como objetivo estudar o desempenho de um protótipo de equipamento para fins de dessalinizar águas salobras via osmose inversa, fazendo uso de um gerador fotovoltaico com a utilização de um circuito eletrônico, no qual substitui acumuladores de carga (baterias). Com o uso do circuito eletrônico foi possível produzir água potável sem a necessidade da utilização de acumuladores de carga (baterias) e sem danificar o motor-bomba. A ausência do banco de baterias proporciona uma redução dos custos e da necessidade de manutenção; mas o sistema torna-se subordinado às condições instantâneas da radiação solar e da temperatura ambiente. Esse sistema foi instalado no Laboratório de Referência em Dessalinização (LABDES), na Universidade Federal de Campina Grande. O desempenho do sistema foi avaliado com soluções de cloreto de sódio com concentração de 1.000 mg/L e 2.500 mg/L e água de poço com concentração de 3.800 mg/L. As variáveis de medidas, como: tensão, corrente, vazão e pressão foram obtidas em tempo real no Software Data Aquisition, através de sensores elétricos. A partir desses dados foram avaliados os seguintes parâmetros: potência elétrica, vazão do permeado e do concentrado, recuperação e consumo de energia por m3 de água produzida. As condições meteorológicas e as concentrações da água de alimentação influenciam diretamente na pressão, e consequentemente na produção de água. Mesmo com a grande variação de tensão em função da irradiação solar, o sistema mostrou condições técnicas de produzir 0,25 m3/h de água dessalinizada. A pressão máxima obtida foi de 8,2 kgf/cm2. O balanço econômico, que representa o custo-benefício de implantação, operacional e manutenção para atender comunidades isoladas, mostrou que o menor custo de água dessalinizada é obtido quando o sistema de dessalinização é instalado em localidade na qual já possui o poço tubular e um local para servir de abrigo para o sistema de dessalinização. Para essas localidades é viável o uso de painéis fotovoltaicos. / The lack of drinking water in some places of the world, more precisely in the semi-arid region of Brazil, is an old problem, worsened by the pollution, irregular distribution and high salinity of underground waters. On the other hand, those areas possess a great solar irradiation rate that favors the use of photovoltaic panels, mainly where the electric net is not available. Seeking to improve the life quality and to minimize the problem of the lack of drinking water in those areas, the objective of this work is to study and evaluate an osmosis reverse desalination system, using photovoltaic solar energy coupled to an electronic circuit. This electronic circuit replaces the use of batteries without damaging the motor-bomb. The absence of batteries provides a reduction of the cost and maintenance need; but the system is subordinated to the instantaneous conditions of the solar radiation. This system was installed at the Reference Laboratory of Desalination (LABDES) in the Federal University of Campina Grande. The system was evaluated with sodium chloride solutions of 1,000 and 2,500 mg/L NaCl concentrations, and a well water of 3,800 mg/L TDS concentration. The meteorological conditions and the concentrations of the feeding water influence directly the applied pressure and consequently the permeate production. Even with the intermittent energy delivered by the solar photovoltaic panels, the desalination system showed good technical conditions to produce 0.25 m3/h of potable water. The economical statements , that the implantation cost-benefit represents, operational and maintenance to take care of isolated communities, showed that the lesser desalinizaded water cost is gotten when the desalination system is installed in locality in which already possesss the well and a place to serve of shelter for the desalination system. For these localities the use of photovoltaics panels is viable.