A combined temperature-programmed reaction spectroscopy and Fourier-transform infrared spectroscopy study of CO2/H2 and CO/CO2/H2 interactions with model ZnO/SiO2, Cu/SiO2 and Cu/ZnO/SiO2 methanol-synthesis catalysts

The reaction of CO2 and H2 with ZnO/SiO2 catalyst at 295 K gave predominantly hydrogencarbonate on zinc oxide and a small quantity of formate was evolved after heating at 393 K. Elevation of the reaction temperature to 503 K enhanced the rate of formation of zinc formate species. Significantly these formate species decomposed at 573 K almost entirely to CO2 and H2. Even after exposure of CO2-H2 or CO-CO2-H2 mixtures to highly defected ZnO/SiO2 catalyst, the formate species produced still decomposed to give CO2 and H2. It was concluded that carboxylate species which were formed at oxygen anion vacancies on polar Zn planes were not significantly hydrogenated to formate. Consequently it was proposed that the non-polar planes on zinc oxide contained sites which were specific for the synthesis of methanol. The interaction of CO2 and H2 with reduced Cu/ZnO/SiO2 catalyst at 393 K gave copper formate species in addition to substantial quantities of formate created at interfacial sites between copper and zinc oxide. It was deduced that interfacial formate species were produced from the hydrogenation of interfacial bidentate carbonate structures. The relevance of interfacial formate species in the methanol synthesis reaction is discussed. Experiments concerning the reaction of CO2-H2 with physical mixtures of Cu/SiO2 and ZnO/SiO2 gave results which were simply characteristic of the individual components. By careful consideration of previous data a detailed proposal regarding the role of spillover hydrogen is outlined. Admission of CO to a gaseous CO2-H2 feedstock resulted in a considerably diminished amount of formate species on copper. This was ascribed to a combination of over-reduction of the surface and site-blockage.

A fourier-transform infrared study of CO2 and CO2/H2 interactions with caesium-doped copper catalysts

FTIR spectra are reported of CO2 and COi/Hi on a silica-supported caesium-doped copper catalyst. Adsorption of COj on a "caesium"/silica surface resulted in the formation of COj and complexed CO species. Exposure of CO2 to' a caesium-doped reduced copper catalyst produced not only these species but also two forms of adsorbed carboxylate giving bands at 1550, 1510, 1365 and 1345 cm"1. Reaction of carboxylate species with hydrogen at 388 K gave formate species on copper and caesium oxide in addition to methoxy groups associated with caesium oxide. Methoxy species were not detected on undoped copper catalyst suggesting that caesium may be a promoter for the methanol synthesis reaction. Methanol decomposition on a caesium-doped copper catalyst produced a small number of formate species on copper and caesium oxide. Methoxy groups on caesium oxide decomposed to CO and U.2, and subsequent reaction between CO and adsorbed oxygen resulted in carboxylate formation. Methoxy species located at interfacial sites appeared to exhibit unusual adsorption properties.

Effectiveness of cysteine proteases on protein/pigment film removal

Objective: Theaflavin (TF) from the black tea can react to human salivary proline-rich proteins (PRPs) to form stains on exposed dental surfaces. Here, we employed a model of protein/pigment film using TF and dephosphorylated bovine b-casein (Db-CN), which has an extended conformation, similar to that of salivary PRPs, on a sensor surface to assess the efficacy of cysteine proteases (CPs) including papain, stem bromelain, and ficin, on removing TF bound to Db-CN and the control TF readsorption on the residual substrate surfaces was also measured. Methods: The protein/pigment complex film was built by using a quartz crystal microbalance with dissipation (QCM-D). The efficacies of CPs were assessed by Boltzman equation model. The surface details were detected by grazing angle infrared spectroscopy spectra, atomic force microscopy images, and contact angles. Results: The efficacy order of CPs on hydrolyzing protein/pigment complex film is ficin > papain > bromelain. The results from grazing angle infrared spectroscopy spectra, atomic force microscopy images, and contact angles demonstrated that TF bound on the Db- CN was effectively removed by the CPs, and the amount of TF readsorption on both the residual film of the Db-CN/TF and the Db-CN was markedly decreased after hydrolysis. Conclusion: This study indicates the potential application of the CPs for tooth stain removal and suggests that these enzymes are worthy of further investigation for use in oral healthcare.

Implementation and removal of an affirmative-action quota : the impact on task assignment and workers’ skill acquisition

Both the United States and Canada have federal legislation that attempts to address employment inequities across specific target groups. The US has a long tradition of affirmative action, dating back to President Kennedy’s 1961 Executive Order; Canada enacted its Employment Equity Act in 1986. Employment Equity/Affirmative Action policy has attracted significant controversy, with high profile court cases and the repeal of state/provincial legislation. Coate and Loury (1993) examine the theoretical impact of introducing affirmative action. Unfortunately the theoretical impact of affirmative action is ambiguous. The current paper employs a laboratory experiment to shed empirical light on this theoretical ambiguity.

Pyrolysing poultry litter reduces N2O and CO2 fluxes

Application of poultry litter (PL) to soil can lead to substantial nitrous oxide (N2O) emissions due to the co-application of labile carbon (C) and nitrogen (N). Slow pyrolysis of PL to produce biochar may mitigate N2O emissions from this source, whilst still providing agronomic benefits. In a corn crop on ferrosol with similarly matched available N inputs of ca. 116 kg N/ha, PL-biochar plus urea emitted significantly less N2O (1.5 kg N2O-N/ha) compared to raw PL at 4.9 kg N2O-N/ha. Urea amendment without the PL-biochar emitted 1.2 kg N2O-N/ha, and the PL-biochar alone emitted only 0.35 kg N2O-N/ha. Both PL and PL-biochar resulted in similar corn yields and total N uptake which was significantly greater than for urea alone. Using stable isotope methodology, the majority (~ 80%) of N2O emissions were shown to be from non-urea sources. Amendment with raw PL significantly increased C mineralisation and the quantity of permanganate oxidisable organic C. The low molar H/C (0.49) and O/C (0.16) ratios of the PL-biochar suggest its higher stability in soil than raw PL. The PL-biochar also had higher P and K fertiliser value than raw PL. This study suggests that PL-biochar is a valuable soil amendment with the potential to significantly reduce emissions of soil greenhouse gases compared to the raw product. Contrary to other studies, PL-biochar incorporated to 100 mm did not reduce N2O emissions from surface applied urea, which suggests that further field evaluation of biochar impacts, and methods of application of both biochar and fertiliser, are needed.

Removal of phosphorus using NZVI derived from reducing natural goethite

Nano zero valent iron (NZVI) prepared by reducing natural goethite in hydrogen at 550 °C was used to remove phosphate. The effect of particle size, reaction time, NZVI dose, pH, initial phosphorus concentration, and oxygen amount in reaction system on phosphorus removal was investigated. The characterization of X-ray fluorescence (XRF), X-ray diffraction (XRD), N2 adsorption and desorption (BET analysis), transmission electron microscope (TEM), field emission scanning electron microscope with a energy dispersive X-ray detector (FESEM/EDS) and X-ray photoelectron spectroscopy (XPS) indicated that nanoscale of iron (around 80–150 nm length and 5–30 nm width) was prepared successfully with high dispersion and relative large surface area around 22 m2/g. The results of batch experiments and XPS analysis suggested that this kind of NZVI had a good performance on removal of phosphate (over 99%) despite in slightly acidic media as the initial concentration of P was 5 mg/L. The reason was ascribed to the effective corrosion of this NZVI under the function of proton and dissolved oxygen in spite of the existence of thin passive films.

Development of modified inorganic adsorbents for radioactive iodine removal and biomolecule adsorption

Development and application of inorganic adsorbent materials have been continuously investigated due to their variability and versatility. This Master thesis has expanded the knowledge in the field of adsorption targeting radioactive iodine waste and proteins using modified inorganic materials. Industrial treatment of radioactive waste and safety disposal of nuclear waste is a constant concern around the world with the development of radioactive materials applications. To address the current problems, laminar titanate with large surface area (143 m2 g−1) was synthesized from inorganic titanium compounds by hydrothermal reactions at 433 K. Ag2O nanocrystals of particle size ranging from 5–30 nm were anchored on the titanate lamina surface which has crystallographic similarity to that of Ag2O nanocrystals. Therefore, the deposited Ag2O nanocrystals and titanate substrate could join together at these surfaces between which there forms a coherent interface. Such coherence between the two phases reduces the overall energy by minimizing surface energy and maintains the Ag2O nanocrystals firmly on the outer surface of the titanate structure. The combined adsorbent was then applied as efficient adsorbent to remove radioactive iodine from water (one gram adsorbent can capture up to 3.4 mmol of I- anions) and the composite adsorbent can be recovered easily for safe disposal. The structure changes of the titanate lamina and the composite adsorbent were characterized via various techniques. The isotherm and kinetics of iodine adsorption, competitive adsorption and column adsorption using the adsorbent were studied to determine the iodine removal abilities of the adsorbent. It is shown that the adsorbent exhibited excellent trapping ability towards iodine in the fix-bed column despite the presence of competitive ions. Hence, Ag2O deposited titanate lamina could serve as an effective adsorbent for removing iodine from radioactive waste. Surface hydroxyl group of the inorganic materials is widely applied for modification purposes and modification of inorganic materials for biomolecule adsorption can also be achieved. Specifically, γ-Al2O3 nanofibre material is converted via calcinations from boehmite precursor which is synthesised by hydrothermal chemical reactions under directing of surfactant. These γ-Al2O3 nanofibres possess large surface area (243 m2 g-1), good stability under extreme chemical conditions, good mechanical strength and rich surface hydroxyl groups making it an ideal candidate in industrialized separation column. The fibrous morphology of the adsorbent also guarantees facile recovery from aqueous solution under both centrifuge and sedimentation approaches. By chemically bonding the dyes molecules, the charge property of γ-Al2O3 is changed in the aim of selectively capturing of lysozyme from chicken egg white solution. The highest Lysozyme adsorption amount was obtained at around 600 mg/g and its proportion is elevated from around 5% to 69% in chicken egg white solution. It was found from the adsorption test under different solution pH that electrostatic force played the key role in the good selectivity and high adsorption rate of surface modified γ-Al2O3 nanofibre adsorbents. Overall, surface modified fibrous γ-Al2O3 could be applied potentially as an efficient adsorbent for capturing of various biomolecules.

New catalysts for organic synthesis driven by light and efficient sorbents for removal of radioactive ions from water

The body of the thesis contained two separate elements which made an original contribution to fundamental understanding in the areas of photocatalysis, chemical synthesis and water treatment. Research on chemical reactions catalyzed by noble metal nanoparticles (such as gold) or surface complex grafted metal oxides which can be driven by sunlight at ambient temperature and the second element on radioactive cesium (137Cs+) cations and iodine (125I-) anions recovery by the unique structural features of titanate nanostructures for firmly capture and safe storage; the works has been all published in journals that are rated at the top of their respective fields.

Removal of bisphenol A from wastewater by Ca-montmorillonite modified with selected surfactants

Organo Arizona SAz-2 Ca-montmorillonite was prepared with different surfactant (DDTMA and HDTMA) loadings through direct ion exchange. The structural properties of the prepared organoclays were characterized by XRD and BET instruments. Batch experiments were carried out on the adsorption of bisphenol A (BPA) under different experimental conditions of pH and temperature to determine the optimum adsorption conditions. The hydrophobic phase and positively charged surface created by the loaded surfactant molecules are responsible for the adsorption of BPA. The adsorption of BPA onto organoclays is well described by pseudo-second order kinetic model and the Langmuir isotherm. The maximum adsorption capacity of the organoclays for BPA obtained from a Langmuir isotherm was 151.52 mg/g at 297 K. This value is among the highest values for BPA adsorption compared with other adsorbents. In addition, the adsorption process was spontaneous and exothermic based on the adsorption thermodynamics study. The organoclays intercalated with longer chain surfactant molecules possessed a greater adsorption capacity for BPA even under alkaline conditions. This process provides a pathway for the removal of BPA from contaminated waters.

A review of the removal of anions and oxyanions of the halogen elements from aqueous solution by layered double hydroxides

The application of layered double hydroxides (LDHs) and thermally activated LDHs for the removal of various fluorine (F-, BF-4), chlorine (Cl-,ClO-4), bromine (Br-, BrO-3) and iodine (I-, IO-3) species from aqueous solutions has been reviewed in this article. LDHs and thermally activated LDHs were able to significantly reduce the concentration of selected anions in laboratory scale experiments. The M2+:M3+ cation ratio of the LDH adsorbent was an important factor which influenced anion uptake. Though LDHs were able to remove some target anion species through anion exchange and surface adsorption thermal activation and reformation generally produced better results. The presence of competing anions including carbonate, phosphate and sulphate had a significant impact on uptake of the target anion as LDHs typically exhibit lower affinity towards monovalent anions compared to anions with multiple charges. The removal of fluoride and perchlorate from aqueous solution by a continuous flow system utilising fixed bed columns packed with LDH adsorbents has also been investigated. The adsorption capacity of the columns at breakpoint was heavily dependent on the flow rate and lower than result reported for the corresponding batch methods. There is still considerable scope for future research on numerous topics summarised in this article.

Electrocatalytically switchable CO2 capture : first principle computational exploration of carbon nanotubes with pyridinic nitrogen

Carbon nanotubes with specific nitrogen doping are proposed for controllable, highly selective, and reversible CO2 capture. Using density functional theory incorporating long-range dispersion corrections, we investigated the adsorption behavior of CO2 on (7,7) single-walled carbon nanotubes (CNTs) with several nitrogen doping configurations and varying charge states. Pyridinic-nitrogen incorporation in CNTs is found to induce an increasing CO2 adsorption strength with electron injecting, leading to a highly selective CO2 adsorption in comparison with N2. This functionality could induce intrinsically reversible CO2 adsorption as capture/release can be controlled by switching the charge carrying state of the system on/off. This phenomenon is verified for a number of different models and theoretical methods, with clear ramifications for the possibility of implementation with a broader class of graphene-based materials. A scheme for the implementation of this remarkable reversible electrocatalytic CO2-capture phenomenon is considered.

Nurse-led chest drain removal in a cardiac high dependency unit

Within the cardiac high dependency unit it is currently a member of the surgical team who makes the decision for a patient's chest drain to be removed after cardiac surgery. This has often resulted in delays in discharging one patient and therefore in admitting the next. A pilot study was carried out using a working standard that had been developed, incorporating an algorithmic model. The results have enabled nursing staff in a cardiac high dependency unit to undertake this responsibility independently.

A new approach to prepare ZVI and its application in removal of Cr(VI) from aqueous solution

Zero valent iron (ZVI) was prepared by reducing natural goethite (NG-ZVI) and synthetic goethite (SG-ZVI) in hydrogen at 550 °C. XRD, TEM, FESEM/EDS and specific surface area (SSA) and pore analyser were used to characterize goethites and reduced goethites. Both NG-ZVI and SG-ZVI with a size of nanoscale to several hundreds of nanometers were obtained by reducing goethites at 550 °C. The reductive capacity of the ZVIs was assessed by removal of Cr(VI) at ambient temperature in comparison with that of commercial iron powder (CIP). The effect of contact time, initial concentration and reaction temperature on Cr(VI) removal was investigated. Furthermore, the uptake mechanism was discussed according to isotherms, thermodynamic analysis and the results of XPS. The results showed that SG-ZVI had the best reductive capacity to Cr(VI) and reduced Cr(VI) to Cr(III). The results suggest that hydrogen reduction is a good approach to prepare ZVI and this type of ZVI is potentially useful in remediating heavy metals as a material of permeable reaction barrier.

Monitoring phase behavior of sub- and supercritical CO2 confined in porous fractal silica with 85% porosity

Phase behavior of CO2 confined in porous fractal silica with volume fraction of SiO2 φs = 0.15 was investigated using small-angle neutron scattering (SANS) and ultrasmall-angle neutron scattering (USANS) techniques. The range of fluid densities (0<(FCO2)bulk<0.977 g/cm3) and temperatures (T=22 °C, 35 and 60 °C) corresponded to gaseous, liquid, near critical and supercritical conditions of the bulk fluid. The results revealed formation of a dense adsorbed phase in small pores with sizes D<40 A° at all temperatures. At low pressure (P <55 bar, (FCO2)bulk <0.2 g/cm3) the average fluid density in pores may exceed the density of bulk fluid by a factor up to 6.5 at T=22 °C. This “enrichment factor” gradually decreases with temperature, however significant fluid densification in small pores still exists at temperature T=60°C, i.e., far above the liquid-gas critical temperature of bulk CO2 (TC=31.1 °C). Larger pores are only partially filled with liquid-like adsorbed layer which coexists with unadsorbed fluid in the pore core. With increasing pressure, all pores become uniformly filled with the fluid, showing no measurable enrichment or depletion of the porous matrix with CO2.

Dynamic Micromapping of CO2 Sorption in Coal

We have applied X-ray and neutron small-angle scattering techniques (SAXS, SANS, and USANS) to study the interaction between fluids and porous media in the particular case of subcritical CO2 sorption in coal. These techniques are demonstrated to give unique, pore-size-specific insights into the kinetics of CO2 sorption in a wide range of coal pores (nano to meso) and to provide data that may be used to determine the density of the sorbed CO2. We observed densification of the adsorbed CO2 by a factor up to five compared to the free fluid at the same (p, T) conditions. Our results indicate that details of CO2 sorption into coal pores differ greatly between different coals and depend on the amount of mineral matter dispersed in the coal matrix: a purely organic matrix absorbs more CO2 per unit volume than one containing mineral matter, but mineral matter markedly accelerates the sorption kinetics. Small pores are filled preferentially by the invading CO2 fluid and the apparent diffusion coefficients have been estimated to vary in the range from 5 × 10-7 cm2/min to more than 10-4 cm2/min, depending on the CO2 pressure and location on the sample.