Oleaginous plant seeds and seed by-products for water treatment

Julien Boucher
EPFL, 2006
Thèse EPFL

Résumé

The treatment of water is needed for the supply of adequate quantity and quality of drinking water, as well as before the discharge of wastewater to the environment. Treatment technologies are often costly, involve chemicals that may have detrimental effects to health and the environment, or may not be available locally. Consequently, there is a need to find sustainable alternative technologies, adapted for small-scale water treatment units and for developing countries. Oleaginous plant seeds represent a renewable resource available world-wide, basically grown for oil-production, but which has been identified for potential applications in water treatment, such as in the extraction of flocculating proteins (moringa seeds) or for metal biosorption. This thesis consists of a systematic study to investigate the various possible applications of oleaginous seeds and seed by-products for water treatment, with rapeseed (Brassica napus) used as model species. Three main by-products of oilseeds were studied: (i) oil-bodies (OB), the organelles of oil storage in plant seeds, which consist of oil core microcapsules (≈ 1 μm diameter) surrounded by a lipoproteinaceous membrane, (ii) press-cake (PC), the solid residue resulting after seed pressing for oil extraction, composed of fibres, proteins, membrane lipids and residual oil, and (iii) seed husks. OB were shown to have flocculation activity for clay suspensions, comparable to that of the moringa proteinaceous extract1. The flocculation activity of these natural microspheres results from the presence of specific proteins (oleosins) at the surface. Ionic bridging, between oleosins and groups at the surface of clays, is postulated to be the mechanism involved in the flocculation activity. Thus oil-bodies appear as possible candidates for the flocculation of silica or clay laden water (Chapters 1 and 2). Furthermore it was demonstrated that OB and PC constitute novel types of biosorbents for hydrophobic organic pollutants (HOP) based on a liquid-liquid extraction mechanism. Atrazine, which was employed as a model compound for HOP, was shown to partition from an aqueous phase to the oil reservoir of the OB, respectively to the residual oil trapped in the PC matrix. This sorption mechanism (absorption) is in contrast to that for other biosorbents which is generally based on adsorption, and makes PC and OB particularly suited for the treatment of highly laden effluents and hydrophobic compounds (Chapters 3 and 5). Both in the case of OB and PC, the degradation of the sorbed compounds is foreseen by burning of the sorbent material. However, the feasibility of using oil core microcapsules saturated with a HOP for performing two-phase biodegradation was also demonstrated (Chapter 4). The capsules were suspended in a HOP degrading bacterial culture, where the HOP diffused into the aqueous phase and was degraded by the bacteria, leading to further release of the compound into the aqueous phase according to equilibrium partitioning. Thus the concentration in the aqueous phase remains low (below toxicity), but the global concentration in the system, including organic phase, is high, hence greatly reducing the aqueous volume to be biologically treated. Besides the possibility of using PC as biosorbent in a batch system, the feasibility of running sorption experiments in a semi-continuous way was discussed using columns packed with PC (Chapters 6 and 7). Finally the sorption of metal ions on PC was investigated, using copper as a model metal species. The husks of the seeds present as residues in the PC show very interesting sorption properties with complex adsorption mechanisms involving chemisorption and ion exchange (Chapter 7). The results of this thesis demonstrate that oleaginous seed materials exhibit versatile properties for developing novel and sustainable water treatment technologies. ------------------------------ 1Doerries, C (2005). Coagulants of Moringa oleifera Lam. Seeds Purification and Characterisation. Thèse N°3251. LGCB. Faculté des Sciences de Base. Lausanne, EPFL.

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Julien Boucher
EPFL, 2006
Thèse EPFL

Résumé

Official source

https://infoscience.epfl.ch/record/85800?ln=fr

À propos de ce résultat

Concepts associés (17)

Concepts associés

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Publications associées (11)

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Chargement

Heterogeneous kinetics of some atmospherically relevant reactions

A low pressure reactor (Knudsen cell) coupled to molecular beam modulated mass spectrometry was used to study the heterogeneous kinetics of the following three systems: (1) NO2 on amorphous carbon, (2) H2O vapor on ice and (3) gaseous HCl on ice. The first system was investigated at ambient temperature while the two last ones were investigated at temperatures typical of the stratosphere, that is roughly between 160 and 220K. The solid phase samples correspond to model surfaces whose physicochemical properties come very close to the ones of atmospheric particulates. Firstly, we studied the interaction of gaseous NO2 with three different commercial samples of amorphous carbon having widely differing physicochemical properties. Using in situ laser-induced fluorescence, the only major product was unambiguously determined to be NO with the oxidation product of carbon apparently remaining on the surface. Probing the gas phase with mass spectrometry (MS), both pulsed valve dosing and steady state experiments were performed and revealed a complex reaction mechanism for both the uptake as well as product formation. The initial uptake coefficient γo for NO2 was (6.4±2.0)·10-2 and proved to be identical within experimental uncertainty for all three types of amorphous carbon. The initial NO2 uptake rate was independent of the mass of the carbon sample and scaled with its external geometrical surface. Applying a simple chemical kinetic model to both pulsed dosing and steady state experiments resulted in an effective surface for uptake on amorphous carbon ranging between a factor of 2.8 to 8.4 larger than the geometrical surface area, but inversely proportional to the measured BET surface area of the three types of amorphous carbon. This means that the amorphous carbon with the highest BET surface (FW2) had the lowest external surface for NO2 adsorption. The chemical kinetic model included competing processes between Langmuir-type adsorption and inhibition controlling the adsorption kinetics of NO2 and revealed that the NO generation rate differed greatly between the three carbon samples examined. All samples showed saturation effects of differing degree that were partially reversible through prolonged pumping at 10-4 Torr and/or heating. Virgin amorphous carbon samples did not take up H2O vapor at 20 mTorr, and no HONO and/or HNO3 was detected in simultaneous NO2/H2O exposure experiments. CO and CO2 were detected when a sample previously exposed to NO2 was heated by an incandescent lamp. Moreover, upon heating such a sample, a MS signal m/e 62 originating from NO3 and/or N2O5 was detected. In addition to the experiments conducted on the three commercial carbon samples, we carried out uptake experiments of NO2 on acetylene soot. Originating from the flame of an acetylene burner, this soot was freshly deposited on glass dishes before each experiment. The initial uptake coefficient γo for NO2 was measured to be (3.0±1.1)·10-2 is smaller by a factor of two compared to γo observed in the uptake on commercial samples whose mass was a factor of 10 higher. In addition to NO, a net formation of HONO (m/e 47) was observed. This HONO formation is strongly dependent on the instantaneous water desorption from the sample as well as on the NO2 partial pressure in the reactor. On the other hand, it is not enhanced by an external water flow which did not show any interaction with the carbon sample. Upon heating the sample using an incandescent lamp, significant amounts of water desorbed, suggesting that the water vapor had condensed into the micropores of the soot during combustion. No quantitative results are presented yet. However, as no correlation between HONO formation and NO partial pressure has been observed so far, we suggest a reaction mechanism that only involves NO2 and H2O but no NO: 2 NO2 (g) + H2O HONO + HNO3 In a second study, the kinetics of condensation and evaporation of water on ice was determined in the temperature range of 170 to 220K. The rate of evaporation Fev corresponds to the evaporation of 70±10 monolayers of H2O per second at 200K. The condensation rate constant kc has a negative activation energy of -3.l±1.5kcal/mol which is significantly larger than the one recently measured by Haynes et al. We report the first real time kinetic measurements of water condensation on ice at stratospherically relevant temperatures. At temperatures above 160K, pulsed dosing experiments show a dose dependence of the condensation rate coefficient. For example, the condensation rate coefficient increases by a factor of five with a 1000 fold increase of the H2O dose from 1·1015 to 1·1018 molecules per pulse at 180K. This pressure dependence of the condensation rate constant may be explained by an autocatalytic mechanism involving the competition of two condensation channels. These two channels feed two different surface species, one of which leads to autocatalytic condensation. This mechanism gives insight into the manner in which a gas phase molecule is stepwise incorporated into tetrahedrally coordinated bulk ice. In a third and ongoing study, the uptake kinetics of HCl on ice has been investigated by pulsed valve experiments in the temperature range of 180 to 210K and are discussed as a function of the state of the surface. In fact, some of the pulsed valve experiments present a relaxation to a steady state level. It is shown that this level originates from the evaporation of a liquid solution corresponding to a temperature specific HCl concentration. The threshold of the injected dose leading to this solution layer is estimated to be 8·1014 molecules. This threshold corresponding to a fraction of a monolayer may be explained by the formation of small domains along grain boundaries or other lattice imperfections. Within detection limit, no difference in keff has been observed for pulses on the solution or on a previously exposed sample without formation of the solution. In the case of pulses forming a solution layer, a fraction of 20±20% of the injected molecules remains permanently adsorbed on the surface. In the temperature range from 210 to 180K, the pulsed valve experiments yield values of keff roughly between 5 and 25s-1 and an activation energy of -1.6±0.7kcal/mol which are consistent with the values observed by Flueckiger in steady state experiments using the 15mm escape aperture (kuni varying from 12 to 23s-1 and an activation energy of -1.9±0.25 kcal/mol).

EPFL1996

Chargement

Single-molecule-level characterization of supramolecular systems at surfaces

Dietmar Payer

This thesis deals with the self-organization of individual building blocks, specifically organic molecules and metal atoms, into supramolecular structures on metal surfaces under ultra high vacuum conditions (UHV). Self-organization of supramolecular systems is a promising candidate for a bottom-up approach in the fabrication of complex structures with specific properties. This process is steered by interactions between functional groups of the individual building blocks and is of apparent interest to gain a detailed understanding of the influence and the behavior of these functional groups enabling intermolecular binding. In the first part of the thesis, we investigate hydrogen bonded structures on metal surfaces. Of especial interest is the possibility of the formation of ionic hydrogen bonds, a special class of hydrogen bond which connects a charged donor (acceptor) and a neutral acceptor (donor) and is important in biological systems. By combined Scanning Tunneling Microscopy (STM), X-ray Photoelectron Spectroscopy (XPS) and Near Edge X-ray Absorption Fine Structure (NEXAFS) measurement we show the deprotonation of carboxylic functions in the molecules, forming carboxylate groups involved in intermolecular binding. With our complementary experimental and theoretical examinations we clearly show that the carboxylate groups are indeed still charged although adsorbed onto a conducting metal surface and that the observed structures can be computationally reproduced by using these charges in classical molecular dynamic calculations. Our investigations clearly reveal that all requirements for the formation of ionic hydrogen bonds in these samples at metal surfaces under solvent free conditions are fulfilled. In the second part, the confinement of surface state electrons in self-assembled hydrogen-bonded structures is investigated. The examined structure contains two-dimensional cavities, with different inner diameters in the periodic arrangement and in domain boundaries. Inside the cavities we detect a spatially localized modification in the local density of states (LDOS) of the Ag(111) surface state electrons. The energy of the peak correlates with the cavity area as predicted by a simple "particle in a box" model. This clearly shows that the surface state electrons form a confined state inside the cavities. Furthermore we examine self-assembled periodic structures as templates for binding single macrocyclic molecules. The macrocyclic molecules can be deposited by sublimation, as STM-topographs with submolecular resolution reflect the shape of the intact molecules and reveal a coverage dependent aggregation behavior. We show that it is possible to fabricate a structure in which at most one macrocyclic molecule per pore can be found in a defined binding position. In the last part of the thesis we investigate the influence of individual metal atoms on the chemical activity and the self-assembly process of molecules on metal surfaces. First, we demonstrate the high chemical reactivity of these metal atoms. In our experiments we address the chemical reactivity of static active sites, like kinks and step edges, and of dynamic active sites, like the metal atoms, separately. Doing this we show that a non-negligible amount of the chemical reactivity of a metal surface is due to this dynamic adatom gas. Furthermore the influence of metal atoms on the structure formation of organic molecules is investigated. We show that two-dimensional structures based on a complex formation between metal centers and ligands can be formed and that the coordination number is independent of the substrate symmetry. Furthermore, we show the possibility that on metal surfaces one can prepare three-fold coordinated Fe-centers, a coordination number which is rarely seen in three dimensional chemistry. In the last part we study catenanes, which consist of two interlocked macrocyclic molecules. Main interest is on the confirmation of a structural change of the catenanes adsorbed on a metal substrate. For our experiments we use the fact that the catenanes are designed to "trap" a Cu-atom by complex formation. As this reaction is associated with a structural change and a change in intermolecular interaction, we can verify a reaction of catenanes adsorbed onto a surface with Cu adatoms and therefore a structural alteration by simply imaging the formed structures. Our measurements show the possibility of depositing large molecules like catenanes by sublimation and of their potential for use as molecular machines adsorbed onto metal surfaces.

EPFL2007

Chargement

The development of innovative bioanalytical technologies that enable the discovery of new therapeutics or the creation of systems for rapid, accurate and parallel analyses has gained an extraordinary interest in the biomedical sector in the last 10-15 years. Since proteins are the key-targets for such essential discoveries and developments, a particular emphasis has been placed on proteomics (study of proteins), including the investigation of protein structures, changes of protein expression upon treatment of cellular systems, the role of post-translational protein modifications on cell signaling events and the validation of selected proteins as disease-specific markers or pharmaceutical targets. These studies usually aim at using crude biological samples as the starting materials, which typically contain a large variety of proteins at concentrations covering a wide dynamic range and where the low abundant proteins are often the biologically most relevant. Therefore, the challenge is to create analytical tools which are able to cope with this large protein concentration range and which provide sufficiently high sensitivity to measure low abundant analytes in the presence of a high abundant protein matrix. The information that is expected from such technologies may soon exert a drastic change on the pace of medical research and considerably impact on the care of patients. As protein microarrays offer a powerful tool for the rapid, parallel analysis of complex samples and only require a minimal amount of reagents, they are currently one of the hot topics of life sciences, which strive to provide such analytical solutions. One of the current limiting factors in the field of protein microarrays for achieving the required analytical sensitivity is the amount of proteins that can be immobilized on the proteomic chip surface. Polymer brushes, which consist of an arrangement of polymer chains that are attached by one end to a substrate in a stretched, well-defined chain conformation, can increase the surface area available for protein binding, and thus act as a new category of 3D protein microarray substrates. With the advent of surface-initiated controlled polymerization techniques, extremely precise control over the thickness, composition, architecture and grafting density can be achieved, which allow to finely tune the properties of the polymer brush. In addition, these polymer chains may contain, natively or after specific post-polymerization reaction of their side chains, a high density of functional groups that can react with proteins. The different approaches available for the preparation of such surface-tethered polymer chains, the strategies allowing control over their architecture and properties as well as examples of applications related to protein binding are presented in Chapter 1. This Thesis describes the use of polymer brushes to create a new type of 3D proteomic chips, with the ultimate goal to improve the protein binding capacity compared to existing chip surface, without altering the accessibility of the detection reagents or increasing the intrinsic fluorescence of the background. The objective of this research work is to prepare polymer brush-based substrates that can outperform the sensitivity (i.e. increase the signal-to-noise ratio) that is obtained with a commercial microarray system, which is used as a benchmark in this Thesis. In this regard, functional polymer brushes containing epoxide groups that can react with the nucleophilic moieties of proteins have been chosen as promising candidates. In a preliminary set of experiments, the potential of glycidyl methacrylate-containing brushes to bind (bio)molecules via a post-polymerization modification reaction under mild conditions, i.e. at room temperature in aqueous medium, has been studied (Chapter 2). To this end, poly(glycidyl methacrylate) brushes, as well as several poly(glycidyl methacrylate)-co-poly(2-(diethylamino)ethyl methacrylate) copolymer brushes of different composition have been prepared by surface-initiated atom transfer radical (co)polymerization. The kinetics of the post-polymerization modification reaction of these (co)polymer brushes were followed using various model primary amines, as well as proteins. The introduction of tertiary amine groups, incorporated in the polymer brushes such as 2-(diethylamino)ethyl methacrylate units, was demonstrated not only to enhance the rate of the epoxide ring-opening reaction but also to induce higher protein binding capacities as compared to poly(glycidyl methacrylate) homopolymer brushes. The improved loading capacities of the (co)polymer brushes were evaluated in Chapter 3 under conditions that more closely resemble real microarray applications, such as the use of automated nanospotters to deposit proteins and fluorescence readers to detect protein immobilization. In this regard, commercially-available proteomic chips were coated with the epoxide-containing (co)polymer brushes and the spotting conditions as well as the proteins were varied. These studies revealed that the loading capacity depends on the pH and on the investigated protein, but also that the (co)polymer brush-coated substrates show far higher loading capacities than the standard, unmodified proteomic chips. This investigation also ascertained the supremacy of brushes containing 2-(diethylamino)ethyl methacrylate units compared to homopolymer brushes, as well as the superiority of thick (co)polymer brushes in comparison to their thinner equivalents. These (co)polymer brushes were subsequently used as platforms for real, although simplified, protein assays. The modified proteomic chips were spotted with unlabeled proteins that were further recognized with detection antibodies via either a one-step or a two-step approach. The clear benefits observed for copolymer brushes as compared to the existing technology under these realistic assay conditions nicely support the fact that the interior volume of the brush remains accessible for the detection reagents. In conclusion, the combination of the high loading capacity and the remaining accessibility for the detection partners make these (co)polymer brushes, and particularly the poly(glycidyl methacrylate)-co-poly(2-(diethylamino)ethyl methacrylate) brushes, excellent candidates for the improvement of the sensitivity in protein microarray applications.

EPFL2010

Chargement

EPFL2010

Single-molecule-level characterization of supramolecular systems at surfaces

Dietmar Payer

EPFL2007

Heterogeneous kinetics of some atmospherically relevant reactions

EPFL1996