Emma Anna Carolina Emanuelsson

Heterogeneous Lollipop-like V2O5/ZnO Array: A Promising Composite Nanostructure for Visible Light Photocatalysis

ZnO/V(2)O(5) core-shell nanostructures have been prepared by a two-step synthesis route through combined hydrothermal growth and magnetron sputtering. After annealing under oxygen ambience, a ZnO/V(2)O(5) heterogeneous lollipop-like nanoarray formed. The microstructure and crystal orientation of those nanolollipops were investigated by scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM), which show single crystal structure. The optical properties were characterized by UV-vis spectroscopy and showed quite different absorption curves for the as-deposited and annealed samples. The ZnO/V(2)O(5) nanolollipops demonstrated excellent photocatalytic activity in terms of decomposing 2,6-dichlorophenol (2,6-DCP) under visible light, indicating their promising potential as catalysts for industrial wastewater and soil pollution treatments.

Enabling the utilization of wool as an enzyme support: Enhancing the activity and stability of lipase immobilized onto woolen cloth

An improved, simple, effective and superior protocol has been developed to immobilize amano lipase from Pseudomonas fluorescens on woolen cloth using polyethyleneimine (PEI) with glutaraldehyde (GA) cross-linking. The success of immobilization was confirmed by FTIR and confocal laser scanning microscope (CLSM), the latter proving that enzyme is well distributed across the wool fiber surfaces throughout the cloth. Woolen cloth therefore provides a large outer and inner fiber surface area for immobilization with minimal mass transfer resistances during immobilization. The optimal protocol (GA at 0.5% and pH 6, lipase solution pH 6) gave an enzyme load of 46.6 mg g(-1)dry cloth with expressed activity of 178.3 U, 46.8% immobilization yield and 30.2% retained activity. Zeta potential measurements showed that PEI significantly enhanced the positive charge on woolen cloth and shifted the isoelectric point to approximately 7. Therefore at a lipase solution pH of around 6, the wool-PEI and lipase are oppositely charged, leading to a maximal adsorption of lipase to the wool surface. The immobilized lipase also had a good stability and 81% of its original activity was maintained after 10 runs in tributyrin emulsion hydrolysis. This protocol provides a significant improvement in terms of retained activity and lipase stability compared to previous immobilizations on wool and opens up the possibility of using wool as a cheap and effective lipase support material for continuous lipase reactions/reactors and possibly enzyme enhanced woolen fabrics.

Temperature sensitive crystallization of V2O5: from amorphous film to β-V2O5nanorods

Amorphous V2O5 films dramatically transform to standing β-phase V2O5nanorods and flat lying nanoslices after annealing in O2 ambience within a narrow temperature range, showing a remarkable temperature-sensitive crystallization process.

The anoxic extractive membrane bioreactor.

The extractive membrane bioreactor (EMB) employs a dense silicone rubber membrane to selectively extract hydrophobic organic compounds from industrial wastewaters into a bioreactor in order to biodegrade them. The major drawback of the EMB is excess biofilm growth on the membrane, which limits mass transfer and creates oxygen limitations. In this work, nitrate has been used as an electron acceptor instead of oxygen. Due to the high solubility of nitrate in water, it is hypothesised that nitrate penetrates the whole biofilm, preventing the formation of inactive zones of bacteria. Four experiments have been performed with toluene as a model substrate under anoxic conditions. The effect of nitrate concentrations on the biofilm and on the toluene flux have been investigated. In addition, the production of soluble microbial products (SMPs), and bacterial hydrophobicity were studied. Under high nitrate concentrations, the performance of the anoxic EMB was stable and no biofilm was formed. The bacteria metabolised toluene, and the toluene flux remained approximately constant. Conversely, at low nitrate concentration, a decrease in pollutant flux concomitant with biofilm growth was observed. The production of SMPs increased under limiting nitrate concentrations, but the hydrophobicity of the suspended bacteria remained constant. However, the bacterial hydrophobicity of the attached cells was significantly greater than that of the suspended cells.

Study of membrane attached biofilm performance with nitrate as electron acceptor

This paper presents a study that aims to overcome oxygen limitations in membrane-attached biofilms in the Extractive Membrane Bioreactor (EMB), by using nitrate instead of oxygen as an electron acceptor. In the EMB target organic compounds are extracted through a dense membrane into a bioreactor, where they are biodegraded. However, due to bacterial attachment, a membrane-attached biofilm forms on the biomedium side of the membrane. This is problematic as an inverse relationship between the organic flux and biofilm growth is commonly observed. In the aerobic EMB, this is thought to be a consequence of the low solubility of oxygen in water - oxygen can therefore only penetrate thin biofilms. Thus this problem might be overcome by using nitrate, which is very soluble in water. It is hypothesized in this anoxic EMB that nitrate can fully penetrate the biofilm and therefore overcome the inactive zones of bacteria. To test this hypothesis, four experiments have been performed in an EMB with toluene as a model pollutant. The effect of excess and low nitrate concentrations on biofilm formation and toluene flux has been investigated. At low nitrate concentrations, a decrease in pollutant flux concomitant with biofilm growth was observed. Conversely, no biofilm was formed and the flux remained high using excess nitrate. Therefore, to investigate the effect of excess nitrate with biofilm formation, a ferric nitrate flocculent was used to force the formation of a biofilm. However, when the biofilm was formed, the toluene flux across the membrane decreased, similar to the experiment with low nitrate concentrations. This indicates that the solubility of the electron acceptor is not the sole factor controlling the decrease in organic flux with biofilm growth, as previously thought in the aerobic EMB.

CHAPTER 11:Process Intensification of Immobilized Enzyme Reactors

The advantages of enzyme catalysis are high specificity and (enantio)selectivity, resulting in reactions with little or no by-products. The applications of enzymes in aqueous medium are well established and have been extended to organic synthesis more recently. The two limiting factors for large scale application of enzymes are continuous processing and process scale-up. Process intensification has the potential to overcome these challenges posed by conventional processing methods by incorporating a novel reactor design or by using alternate processing methods. Process intensified reactors like membrane reactors, microreactors, monolithic reactors and rotating disc reactors for enzyme catalyzed reactions will be discussed in this chapter. These reactors have shown an improved performance compared to the enzymatic reactors currently in use, and future opportunities include application for enzymatic catalysis on an industrial scale and advances in reactor design and process control.