Les travaux présentés dans ce manuscrit sont consacrés à l’étude et à l’élaboration de résines de collage bio-sourcées pour remplacer les résines Urée-Formol (UF) d’origine pétrochimique, sources de formaldéhyde, utilisées actuellement dans l’industrie panneautière. Les résines étudiées dans le cadre de cette thèse sont formulées à partir de ressources locales (dextrines issues d’amidon de maïs et tanins d’écorces de pin maritime) et doivent respecter certaines contraintes industrielles. Pour répondre à ces contraintes, les travaux de recherche présentés dans ce mémoire vont de la compréhension structurale des mélanges des produits de base jusqu’à la fabrication de panneaux à l’échelle du laboratoire, en passant par la formulation et la réticulation des différentes résines thermodurcissables. Ces travaux montrent qu’il est nécessaire de travailler en milieu alcalin pour solubiliser les tanins. Dans cette situation, les mélanges tanins/dextrines donnent des suspensions colloïdales. Les fractions massiques en tanins et en dextrines permettant d’obtenir des paramètres respectant le cahier des charges varient de 0 à 40%. La réticulation de ces mélanges par l’épichlorhydrine a permis l’obtention de colles thermodurcissables insolubles dans l’eau ayant une bonne stabilité dimensionnelle à sec, mais un pouvoir gonflant plus ou moins important selon la formulation. Les propriétés adhésives, mécaniques et thermiques de ces matériaux ont été caractérisées et ont permis de sélectionner des formulations de colles ayant les meilleures performances thermomécaniques. Enfin, tout en respectant un protocole industriel, des composites ont été fabriqués à partir de ces colles et des particules de bois. Il a été montré que les panneaux de particules obtenus ont des performances mécaniques équivalentes à ceux fabriqués avec des colles UF. / This work aims to substitute resins based on formaldehyde as UF by “green” thermosetting adhesives based on natural and renewable local products, in the wood composite industry. The resins studied in this thesis are made from local resources (dextrins from corn starch and tannins from maritime pine barks) and must respect certain industrial requirements. To meet these industrial constraints, the research work of this manuscript deals with studies ranging from the structural understanding of basic product mixtures, up to the characterization of the properties of panels manufactured in the lab, including the formulation and reticulation of resins. These studies show that it is necessary to work in an alkaline medium to solubilize the tannins. In this situation, the tannins / dextrin mixtures give colloidal suspensions. The mass fractions in tannins and dextrins allowing to obtain parameters respecting the specifications vary from 0 to 40%. The epichlorohydrin has been used as hardener to cross-link these resins. Thermosetting materials with good dimensional stability have been obtained. However the resin swelling depends on the composition of the formulation. Adhesive, mechanical and thermal properties of these materials were characterized. Thus, adhesive formulations with the best thermomechanical performances have been selected. Finally, composites have been made from these adhesives and wood particles, respecting an industrial procedure. It has been shown that these panels and those obtained with UF adhesives have equivalent mechanical performances.

D. Tech. (Department of Chemistry, Faculty of Applied and Computer Sciences), Vaal University of Technology / In the present era of water resources scarcity, efficient treatment of wastewater is a major prerequisite especially for growing economy. Numerous approaches have been studied for the development of cheaper and more effective adsorbents for removal of both organic and inorganic pollutants from wastewater. The present study seeks to harness the potential of biosorption and nanotechnology by producing more efficient, selective, mechanically stable and effective adsorbents for removal of organic and inorganic pollutants. The biosorbent-magnetic nanomaterial was synthesized by coating magnetite nanoparticles with sodium hydroxide treated pine cone by co-precipitation method. Magnetite coated pine bio-composite was then modified by cross-linking with hexamethylene diisocyanate and epichlorohydrin to the molecular recognition compound “cyclodextrin”. These novel biosorbent-magnetic nanoparticle materials were explored in overcoming the drawbacks of the biosorbent alone and selectively remove inorganic and organic pollutants from complex matrices. The synthesized materials were characterized by several analytical techniques including, Fourier Transformed Infrared Spectroscopy (FTIR), Thermogravimetric analysis (TGA), X-Ray Diffraction (XRD), Scanning Electron Microscopy-Energy Dispersive X-Ray (SEM–EDX), Transmission Electron Microscopy (TEM), Brunauer, Emmett and Teller Isotherm (BET) surface area analysis, X-ray Photoelectron Spectroscopy (XPS), Vibrating Sample Magnetometer (VSM) and pH at point of zero charge (pHpzc). Sodium hydroxide treated pine cone and magnetite coated pine cone were applied for both chromium(VI) and arsenic(III) adsorption while the magnetite coated pine cone, magnetite coated pine cone crosslinked to cyclodextrin using both epichlorohydrin and hexamethylene diisocyanate were applied for 4-nitrophenol removal from aqueous solution. Batch adsorption studies were performed to optimize operating parameters such as solution pH, adsorbent dose, contact time, temperature and initial concentration. Pseudo first, pseudo second, intraparticle diffusion, pore and film diffusion kinetic models were determined to investigate the mechanism of adsorption process. Coefficient of correlation, r2, and variable error, methods were also applied in the determination of the best fit of the kinetic method. Structural characterization of magnetite coated pine cone and the magnetite coated pine crosslinked to cyclodextrin using 1,6-hexamethylene diisocyanate and epichlorohydrin were confirmed by characterization techniques applied. The adsorption of Cr(VI), As(III) and 4-nitrophenol was found to be dependent on the solution pH, adsorbent dose, initial concentration, temperature and ionic strength. Kinetic modelling revealed that the adsorption of Cr(VI), As(III) and 4-nitrophenol is controlled by pseudo second order kinetic model suggesting surface adsorption and intraparticle diffusion model. Intraparticle, pore and film diffusion models gave further insight into the controlling diffusion mechanism involved in the adsorption process for all pollutants investigated. Equilibrium studies indicated that the adsorption of all pollutants followed Langmuir isotherm indicating that adsorption sites are homogeneous in nature. The obtained thermodynamic parameters demonstrated that the adsorption of Cr(VI), As(III) and 4-nitrophenol were spontaneous, favourable and endothermic in nature. Anionic effect positively affected Cr(VI) and As(III) removal but had a negative effect on the 4-nitrophenol adsorption. Adsorption of 4-nitrophenol onto the nanocomposite adsorbents was attributed to multiple adsorbent-adsorbate interactions such as hydrogen bonding, hydrophobic attraction and guest host interaction. Magnetite coated pine better removed Cr(VI) and As(III) from aqueous solution than NaOH treated pine cone biomaterial while the magnetite coated pine crosslinked to cyclodextrin using 1,6-hexamethylene diisocyanate exhibited better adsorption performance for 4-nitrophenol removal than the nanocomposite crosslinked using epichlorohydrin and the magnetite coated pine cone.

Polyamideamine epichlorohydrin (PAE) resin is a water soluble additive and the most used permanent wet strength additive in alkaline conditions for preparing wet strengthened papers. In this thesis, we studied some properties of PAE resins and wet strengthened papers prepared from them. In order to elucidate PAE structure, liquid state, 1H and 13C NMR was performed and permitted signals assignment of PAE structure. PAE films were prepared to study cross-linking reactions and then thermal and ageing treatments were performed. According to our results, the main PAE cross-linking reaction occurs by a nucleophilic attack of N atoms in the PAE and/or polyamideamine structures forming 2-propanol bridges between PAE macromolecules. A secondary contribution of ester linkages to the PAE cross-linking was also observed. However, this reaction, which is thermally induced, only occurs under anhydrous conditions. The mechanism related to wet strength development of PAE-based papers was studied by using CMC as a model compound for cellulosic fibres and PAE-CMC interactions as a model for PAE-fibres interactions. Based on results from NMR and FTIR, we clearly showed that PAE react with CMC that is when carboxylic groups are present in great amounts. Consequently, as the number of carboxylic groups present in lignocellulosic fibres is considerably less important and the resulting formed ester bonds are hydrolysable, we postulate that ester bond formation has a negligible impact on the wet strength of PAE-based papers. In the second part of this work, a 100% Eucalyptus pulp suspension was used to prepare PAE-based papers. PAE was added at different dosages (0.4, 0.6 and 1%) into the pulp suspension and its adsorption was indirectly followed by measuring the zeta potential. Results indicate that the adsorption, reconformation and/or penetration phenomena reach an apparent equilibrium between 10 and 30 min. Moreover, we showed that the paper dry strength was not significantly affected by the conductivity level (from 100 to 3000 µS/cm) of the pulp suspension. However, the conductivity has an impact on the wet strength and this effect seems to be enhanced for the highest PAE dosage (1%). We also demonstrated that storing the treated paper under controlled conditions or boosting the PAE cross-linking with a thermal post-treatment does not necessarily lead to the same wet strength. Degrading studies of cross-linked PAE films showed that PAE degradation in a persulfate solution at alkaline medium was more effective. A preliminary study of industrial PAE-based papers (coated and uncoated papers) was also performed. For uncoated paper, persulfate treatment was the most efficient. For coated papers, all treatments were inefficient in the used conditions, although a decrease of the wet tensile force of degraded samples was observed. The main responsible of the decrease of persulfate efficiency for coated papers was probably related to side reactions of free radicals with the coating constituents.

>Magister Scientiae - MSc / Glucose oxidase (GOx) and horseradish peroxidase (HRP) are important enzymes for the development of amperometric enzyme linked immunosensors. The selectivity of each enzyme towards its analyte deepens its importance in determining the sensitivity of the resultant immunosensor. In designing immunosensors that have customized transducer surfaces, the incorporation with FAD and iron based enzymes ensures that electron kinetics remains optimal for electrochemical measurement. Various different immobilization strategies are used to produce response signals directly proportional to the concentration of analyte with minimal interferences. The combination of self-assembled monolayers and supramolecular chemistry affords stability and simplicity in immunosensor design. In this work, two electrochemical strategies for the detection of human chorionic gonadotropin(hCG) is presented. This involves the modification of a gold surface with a thiolated β-cyclodextrin epichlorohydrin polymer (βCDPSH) to form a supramolecular inclusion complex with ferrocene (Fc)-functionalised carboxymethyl cellulose polymer (CMC). Cyclic voltammetry indicated that ferrocene is in close proximity to the electrode surface due to the supramolecular complex formed with βCDPSH. Furthermore, strategy (a) for the detection of hCG used α-antihCG labelled (HRP) as reporter conjugate. Strategy (b) maintained the CMC bifunctionalised with Fc and recognition antibody for hCG hormone. However, the system was functionalised with a HRP enzyme and detection is done by using GOx reporter conjugates for in situ production of hydrogen peroxide. The reduction of H2O2 was used for the amperometric detection of hCG by applying a potential of 200 mV. The sensitivity and limit of detection of both strategies were calculated from calibration plots. For strategy (a) the LOD was found to be 3.7283 ng/mL corresponding to 33.56 mIU/mL and a sensitivity of 0.0914 nA ng-1 mL-1. The corresponding values for strategy (b) are 700 pg/mL (6.3 mIU/mL) and 0.94 nA ng-1 mL-1.

>Magister Scientiae - MSc / Glucose oxidase (GOx) and horseradish peroxidase (HRP) are important enzymes for the development of amperometric enzyme linked immunosensors. The selectivity of each enzyme towards its analyte deepens its importance in determining the sensitivity of the resultant immunosensor. In designing immunosensors that have customized transducer surfaces, the incorporation with FAD and iron based enzymes ensures that electron kinetics remains optimal for electrochemical measurement. Various different immobilization strategies are used to produce response signals directly proportional to the concentration of analyte with minimal interferences. The combination of self-assembled monolayers and supramolecular chemistry affords stability and simplicity in immunosensor design. In this work, two electrochemical strategies for the detection of human chorionic gonadotropin(hCG) is presented. This involves the modification of a gold surface with a thiolated β-cyclodextrin epichlorohydrin polymer (βCDPSH) to form a supramolecular inclusion complex with ferrocene (Fc)-functionalised carboxymethyl cellulose polymer (CMC). Cyclic voltammetry indicated that ferrocene is in close proximity to the electrode surface due to the supramolecular complex formed with βCDPSH. Furthermore, strategy (a) for the detection of hCG used α-antihCG labelled (HRP) as reporter conjugate. Strategy (b) maintained the CMC bifunctionalised with Fc and recognition antibody for hCG hormone. However, the system was functionalised with a HRP enzyme and detection is done by using GOx reporter conjugates for in situ production of hydrogen peroxide. The reduction of H2O2 was used for the amperometric detection of hCG by applying a potential of 200 mV. The sensitivity and limit of detection of both strategies were calculated from calibration plots. For strategy (a) the LOD was found to be 3.7283 ng/mL corresponding to 33.56 mIU/mL and a sensitivity of 0.0914 nA ng-1 mL-1. The corresponding values for strategy (b) are 700 pg/mL (6.3 mIU/mL) and 0.94 nA ng-1 mL-1.