Fiber-reinforced concrete (FRC) is nowadays extensively used in civil engineering throughout the world due to the composites of FRC can improve the toughness, flexural strength, tensile strength, and impact strength as well as the failure mode of the concrete. It is an easy crazed material compared to others materials in civil engineering. Concrete, like glass, is brittle, and hence has a low tensile strength and shear capacity. At present, there are different materials that have been employed to reinforce concrete. In our experiment, nanostructures iron oxide was prepared by electrodepostion in an electrolyte containing 0.2 mol/L sodium acetate (CH3COONa), 0.01 mol/L sodium sulfate (Na2SO4) and 0.01 mol/L ammonium ferrous sulfate (NH4)2Fe(SO4)2.6H2O under magnetic stirring. The resulted showed that pristine Fe2O3 particles, Fe2O3 nanorods and nanosheets were synthesized under current intensity of 1, 3, 5 mA, respectively. And the pull-out tests were performed by Autograph AGS-X Series. It is discovering that the load force potential of nanostructure fibers is almost 2 times as strong as the control sample.

Various concentrations of ferrous and ferric iron solutions were held at room temperature for 60 min before they were assayed for ferrous iron, which may be unstable due to oxidation. The ferrous and ferric solutions (in pH 2 HCl) were maintained as such for 60 min without the use of chelators. There was no significant oxidation of ferrous iron. Also, four different levels of each ferrous and ferric iron were injected into proximal duodenal loops of rat intestine and uptake was determined at four different time intervals. Two iron-replete rats were assigned to each of the treatments. The in situ experiments showed that iron was taken up rapidly from pH 2.0 solutions of ferrous and ferric iron. Maximum amount of iron was taken up in the first 10 min. Uptake of ferrous iron was significantly greater (p < 0.05) than uptake of ferric iron, and there were significant differences in total uptake among the four iron levels used. Uptake, absorption, and adsorption kinetics of both ferrous and ferric iron were determined in situ for both iron-replete and iron-deficient rats. Deficiency caused greater uptake and absorption, confirming a biological adaptation of these processes. Both uptake and absorption were greater for ferrous than for ferric iron and were possibly taken up by different pathways or by a ferrous-ferric pathway with preference for ferrous. Uptake and absorption kinetics were biphasic for both ferrous and ferric iron. The first phase demonstrated saturation kinetics and was followed by a nonsaturable phase at higher concentrations of luminal iron. Iron deficiency altered the uptake and absorption kinetics of ferrous and ferric iron, but not always in a similar manner, suggesting that ferrous and ferric iron were each taken up by a separate pathway. Indications were that enhanced absorption during deficiency was largely due to adaptation of ferric uptake. Iron adsorption was directly proportional to luminal iron concentration, but it was greater for ferric than for ferrous, possibly due to charge interactions. Iron deficiency caused increased adsorption of both ferrous and ferric iron, supporting the notion that adsorption acts to maintain iron in a form available for uptake.

Studies of seafloor hydrothermal activity and its associated geochemical and mineralogical effects have primarily focused on deep sea systems. These processes are not limited to deep sea locations. Numerous shallow hydrothermal systems have been identified along the submerged flanks of volcanic islands such as Vulcano Island, Italy and Ambitle Island, Papua New Guinea. This study investigates the Champagne Hot Springs shallow marine hydrothermal system, located along the submerged flank of the Plat Pays volcanic system on the southwest section of the island of Dominica, Lesser Antilles. The main objective is determine the source of the hydrothermal fluids and gases and their related effect on sediment and precipitate chemistry. A detailed map of the vent field will also be generated to accurately present vent locations and distribution. Geochemical and mineralogical analyses of vent waters, pore waters, gases, sediments and precipitates were determined by High Pressure Liquid Chromatography (HPLC), Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES), Neutron Activation Analysis (NAA), Scanning Electron Microscopy (SEM), Electron Dispersive X-Ray Analysis (EDX), Powder X-Ray Diffraction (XRD), Gas Chromatography and Mass Spectrometry. These analyses have revealed the following: (1) The vent waters and pore waters are mixtures of seawater and meteoric derived hydrothermal fluids in varying proportions. The relative input of each component is both temperature and flow rate dependent. (2) The simultaneous increase in pH and Eh caused by mixing between Fe2+ rich vent fluids and seawater forms precipitates and sediment coatings of hydrous ferric oxides. The elevated concentrations of As and Sb in the precipitates and sediments relative to average Caribbean seafloor sediments is a function of adsorption to the surface of the hydrous ferric oxide, (3) Pore waters in the immediate vicinity of sediment covered vents carry Fe2+ rich fluid to the sediment/seawater interface, where rapid oxidation of soluble Fe2+ to insoluble Fe3+ leads to precipitation of hydrous ferric oxide coatings on sediment grains and subsequent formation of hydrothermally altered sand patches, (4) The gas samples are typical arc-type gases and have both meteoric and magmatic signatures.

Campylobacter jejuni is the leading bacterial cause of human gastroenteritis in the United States. Increasing resistance of Campylobacter to clinical antibiotics raises an urgent need for novel strategies to prevent and control infections in humans and animal reservoirs, which necessitates a better understanding of Campylobacter pathogenesis. We hypothesize that multidrug efflux pump CmeABC and ferric enterobactin (FeEnt) iron acquisition systems, which play a critical role in Campylobacter pathogenesis, are novel targets for developing effective measures against Campylobacter. To test this, the molecular, antigenic, functional, and protective characteristics of two outer membrane proteins, CmeC (an essential component of CmeABC drug efflux pump) and CfrA (a FeEnt receptor), were examined. Both CmeC and CfrA are highly conserved and widely produced in C. jejuni strains. Anti-CmeC and Anti-CfrA antibodies inhibited the function of CmeABC efflux pump and CfrA, resulting enhanced susceptibility to bile salts and reduced utilization of FeEnt of C. jejuni, respectively. Immunoblotting analysis also indicated that CfrA is expressed and immunogenic in vivo. Amino acid substitution mutagenesis demonstrated that a highly conserved basic amino acid R327 in CfrA plays a critical role in FeEnt acquisition. The purified recombinant CmeC and a Salmonella live vaccine expressing the protective epitope of CfrA were evaluated as subunit vaccines against Campylobacter infection in the chicken model. CmeC vaccination elicited immune response but failed to reduce C. jejuni colonization in the intestine. However, Salmonella-vectored vaccine conferred significant protection against C. jejuni challenge. To further elucidate the role of iron acquisition in the pathogenesis of Campylobacter, whole genome sequence of a unique C. jejuni strain was determined using a 454 GS FLX sequencer with Titanium series reagents. Comparative genomics analysis led to the identification of a novel Campylobacter Enterobactin Esterase (Cee) that is essential in the CfrB-dependent FeEnt utilization pathway. Extensive genetic manipulation revealed molecular pathways and mechanistic features of the two orchestrated FeEnt acquisition systems in Campylobacter. This project provides critical information about the feasibility of targeting CmeC and CfrA for immune protection against Campylobacter colonization in the intestine, and increases our understanding of the critical role of FeEnt acquisition in the pathophysiology of Campylobacter.

This research was aimed to investigate the enhancement of electrokinetic (EK) remediation arsenate-contaminated soil by permeable reaction barrier (PRB). All experiments, which experimental parameters included the position, materials, and quantity of PRB, processing fluid types, potential gradients, and treatment time, were conducted in two types of EK systems. One was Pyrex glass cylindrical cells with dimension of 4.2 cm (£r) ¡Ñ 12 cm (L) and the other was a small pilot-scale modulus with dimension of 36cm (L) ¡Ñ18cm (W) ¡Ñ18cm cm (H). The PRBs were composed of four kinds of reaction materials, which included commercial zero valent iron (Fe(0)C), manufactured zero valent iron (Fe(0)M), commercial hydrous ferric oxide (FeOOHC), and manufactured hydrous ferric oxide (FeOOHM), mixed with ottawa sand in a ratio of 1:2,respectively, and installed in the anode, middle, and cathode side of the EK systems. For 5-day EK cylindrical cell tests, the results showed that the PRB installation would result in a lower electroosmosis permeability (Ke) and a higher removal efficiency of arsenate. The arsenate removal efficiency of EK system with PRB was in the range of 43.89-70.25%, which was 1.5~2.6 times greater than that without PRB, and the value of Ke was in the range of 4.30-12.61¡Ñ10-6 cm2/V-s. The soil pH after EK/PRB treatment was much closer to natural and more arsenate was collected in the anode reservoir. Moreover, the remediation performance of FeOOHC as PRB materials was much better than other materials. For EK pilot-scale modulus tests, it was shown that the removal efficiency of arsenate was effectively enhanced as improved experimental parameters and, however, led to increase the treatment cost. In EK modulus without PRB, the removal efficiency of arsenate, elctroosmosis permeability, and energy consumption were 27.76%, 3.30-5.39¡Ñ10-6 cm2/V-s, and 1724.81 kWh/m3, respectively. Furthermore, the treatment cost was NT 9583/m3. As increasing treatment time, graphite electrode, potential gradient, and quantity of PRB materials, the removal efficiency of arsenate increased to as high as 45.11-71.22% and the treatment cost also increased up to NT 24,800-57,730/m3. As investigated the binding form of arsenate with soil after EK/PRB treatment, it was found that the arsenate ¡Vsoil binding forms of Fe-Mn oxide bound, organically bound, and residual in the soil section behind the PRB were much easier transformed to the forms of exchangeable and carbonate bound. The transformation rate reached as high as 72.5% and it increased with treatment time. However, the Fe-Mn oxide bound was still the main binding form, 61.6-81.6%, in the soil section prior to the PRB. The removal mechanism of arsenate contaminated soil remediation was dominated by electromigration, electrolysis, and electroosmosis in EK system without PRB. And, in EK/PRB system, the removal of arsenate from soil was mainly resulted from adsorption rather than redox reaction by PRB. To sum up, the PRB can effectively enhance the electrokinetic remediation of arsenate contaminated soil by choosing the right PRB materials and operation parameters.

Lowering the Maximum Contaminant Level (MCL) for arsenic in drinking water in the U.S., has caused a significant increase in the volume of Arsenic Bearing Solid Residuals (ABSRs) generated by drinking water utilities. Most of the affected utilities are smaller water treatment facilities, especially in the arid Southwest, and are expected to use adsorption onto solid sorbents for arsenic removal. Because of their high adsorption capacity and low cost, iron sorbents are used treatment technology and, when the sorbent's capacity is spent, these ABSRs are disposed in municipal solid waste (MSW) landfills and as a consequence arsenic is likely being released into leachate. However, a mature landfill is a biotic, reducing environment, which causes arsenic reduction and mobilization from the ABSRs. It is well documented that iron and sulfur redox cycles largely control arsenic cycling and, because iron and sulfur are ubiquitous in MSW, it is suspected that they play key roles in arsenic disposition in the landfill microcosm. The purpose of this study is to investigate the degree to which sulfate can prevent arsenic from leaching into landfill through biomineralization and to study ABSRs biogeochemical weathering effect on arsenic sequestration. The primary routes of iron and sulfate reduction in landfills are microbially mediated and biomineralization is a common by-product. In this case, biomineralization is the transformation of ferric (hydr) oxides into ferrous iron phase and sulfate into sulfide minerals such as: siderite (FeCO₃), vivianite (Fe₃(PO₄)₂), iron sulfide (FeS), goethite (α-FeOOH), and realgar (AsS). In this work, long-term microbial reduction and biomineralization of iron, sulfur, and arsenic species are evaluated as processes that both cause arsenic release from landfilled ABSRs and may possibly provide a means to re-sequester As in a recalcitrant solid state. The work uses long-term, continuous flow-through laboratory-scale columns in which controlled conditions similar to those found in a mature landfill prevail. In these simulated landfill column experiments, formation of biominerals, same as those that would naturally occur in typical non-hazardous MSW landfills, will be investigated. The feed contains lactate as the carbon source and primary electron donor, and ferric iron, arsenate, and a range of sulfate concentrations as primary electron acceptors. Our results suggest that biomineralization changes the stability of arsenic through a number of different processes including (i) release of arsenic through reductive dissolution of iron-based ABSRs; and (ii) readsorption/incorporation of released arsenic to secondary biominerals. The influence of biominerals, which have less surface area and adsorption capacity than original AFH, on the retention of arsenic is also investigated in this study. Our results show that the concentration of sulfate fed to the system affects the biomineral formation, and that the relative amounts and sequence of precipitation of biominerals affect the free arsenic concentration that can seemingly be engineered by the concentration of sulfate fed to the system. Comparison between the columns with different sulfate concentrations indicate that inflow sulfate concentration higher than 2.08 mM decreases As mobilization to <50%.

Drinking water contaminated with arsenic is a worldwide problem, especially in developing nations. The research presented in this dissertation describes two major goals: development of hybrid homopolymer polyacrylonitrile (PAN)-based sorbents for arsenate removal from drinking water and understanding regeneration of arsenate from ferric hydroxide-based adsorbents. The homopolymer PAN fiber was chemically modified to introduce functional groups using NaOH and hydrazine hydrate (HH) separately, or in combination of both. The modified fibers were characterized using Fourier transform infrared spectroscopy (FTIR) and ion exchange measurements. The ferric hydroxides were impregnated onto functionalized fibers using two iron loading procedures. The best arsenate removal performance was obtained using the simplest pretreatment procedure of soaking in 10% NaOH at 95 °C for ninety min, followed by precipitation coating of ferric hydroxide. This suggests that adsorbents based on a low-cost PAN fabric may be produced in developing areas of the world where commercial products may not be available. A density functional theory (DFT) molecular modeling was used to compare free energies of reactions and activation barriers in the formation of arsenate-ferric hydroxide complexes. Slow kinetics associated with arsenate adsorption and desorption attributed to the high activation barriers in forming and breaking bonds with the ferric hydroxides. Another aspect of regeneration study focused on the effects of underlying properties of the ferric hydroxides-loaded adsorbents on arsenate recovery. The arsenate loaded ferric hydroxide adsorbent containing no or weak base functionalities can be regenerated using NaOH, while addition of NaCl to NaOH solution is required for same recovery of arsenate from the adsorbents containing strong base anion exchange functionalities. Moreover, the irreversible fraction of arsenate on the adsorbent can be reduced by increasing the concentration of NaOH. Thus, understanding arsenate desorption kinetics and effects of support properties of ferric hydroxide-based adsorbents are important for environmental fate of arsenate and in designing adsorption systems for removing arsenate from potable water.

No description available.

Thesis (Ph. D.)--University of Washington, 2005. / Vita. Includes bibliographical references (leaves 205-218).

A mineração de carvão gera milhões de toneladas de rejeitos, contendo pirita (FeS2). A oxidação da pirita, na presença de ar e água, dá origem a um importante problema ambiental comum em regiões de mineração de carvão, a geração de drenagem ácida de mina (DAM). A oxidação da pirita em presença de água promove a formação de H2SO4 (ácido sulfúrico) o que promove a liberação de ferro nas formas de Fe+2 e Fe+3 , sulfatos e uma série de outros metais como Al, Mn e Zn. Esse problema ocorre de forma bastante intensa na região carbonífera do sul do Brasil em especial nos Estados de Santa Catarina e Paraná. A DAM produzida pelos rejeitos da mineração de carvão necessita passar por um processo de tratamento visando diminuir a acidez e a carga de metais despejada no meio, de forma a atender as exigências ambientais. Assim, o objetivo do presente trabalho foi estudar a produção de um coagulante, o sulfato férrico, a partir dos seguintes materiais: (a) lodo férrico obtido por precipitação seletiva da DAM; (b) rejeito obtido pela jigagem do carvão da Camada Barro Branco, Santa Catarina; e (c) concentrado de pirita obtido pelo rebeneficiamento do rejeito de carvão da Mina do Cambuí, Paraná. A metodologia para a produção do coagulante a partir do lodo consistiu na inicialmente na precipitação seletiva do ferro em pH 3,8, lavagem do precipitado, adição de ácido sulfúrico e evaporação para obtenção de uma solução com concentração de Fe3+ de até aproximadamente 12%. A metodologia para a obtenção do coagulante a partir da pirita presente no rejeito de carvão ou no concentrado de pirita consistiu na percolação de água sob condições oxidantes para a produção de uma lixívia rica em sulfato férrico. A lixívia também foi evaporada para obtenção de uma solução de sulfato férrico com concentrações de Fe3+ de até aproximadamente 12%. A qualidade do coagulante produzido foi avaliada em termos da concentração de Fe, Al, Ca, Mn, Zn, Cu e sulfatos. Os resultados demonstram que todos os materiais estudados apresentaram potencial de produção do coagulante. Entre os contaminantes encontrados, destacam-se os elementos alumínio, cálcio, manganês e zinco. Entretanto, quanto maior o teor de enxofre da amostra, maior o rendimento e maior pureza do produto. Concluiu-se que o beneficiamento do rejeito de carvão para a concentração da pirita permite a obtenção de sulfato férrico de melhor qualidade. Os coagulantes produzidos foram utilizados no tratamento do esgoto do Campus do Vale da UFRGS e de água de abastecimento da região de Porto Alegre. As idéias de valorização dos rejeitos da mineração de carvão estão em sintonia com os princípios da atualidade no que diz respeito ao desenvolvimento sustentável e aos programas de valoração de resíduos e produção mais limpa. / The coal mining generates millions of tonnes of tailings containing pyrite (FeS2). The oxidation of pyrite in the presence of air and water, gives rise to an important environmental problem common in areas of coal mining, the generation of acid mine drainage (AMD). The oxidation of pyrite in the presence of water promotes the formation of H2SO4 (sulfuric acid) which promotes the release of iron in the form of Fe +2 and Fe +3, sulphates and a host of other metals such as Al, Mn and Zn. This problem occurs quite intense in the coal in southern Brazil in particular in the states of Santa Catarina and Parana. The DAM produced by coal waste mining need to go through a treatment process in order to decrease the acidity and metal load discharged into the environment, in order to meet environmental requirements. The objective of this work was to study the production of a coagulant, ferric sulfate, with the following materials: (a) ferric sludge obtained by selective precipitation of DAM (b) obtained by reject coal concentration of the Layer Barro Branco, Santa Catarina, and (c) pyrite concentrate obtained by concentration of the tailings coal mine of Cambuí, Paraná. The methodology for the production of coagulant from sludge was the first in the selective precipitation of iron in pH 3.8, washing the precipitate with sulfuric acid and evaporation to obtain a solution with Fe 3 + concentration of approximately 12% with Fe2O3. The methodology for obtaining the coagulant from the pyrite present in coal or reject the pyrite concentrate was the percolation of water under oxidizing conditions to produce a liquor rich in ferric sulphate. Leach was also evaporated to obtain a solution of ferric sulphate with concentrations of Fe3 + up to approximately 12%. The quality of the coagulant was evaluated in terms of concentration of Fe, Al, Ca, Mn, Zn, Cu and sulfates. The results show that all the materials studied showed potential for production of the coagulant. Among the contaminants found, highlight the elements aluminum, calcium, manganese and zinc. However, the higher the sulfur content of the sample, the higher the yield and higher purity of the product. It was concluded that the processing of the waste coal to the concentration of pyrite to obtain ferric sulphate better. Coagulants produced were used in the treatment of sewage Campus do Vale UFRGS and water supply in the region of Porto Alegre. Ideas for use of tailings from coal mining are in line with the principles of the present time regarding the development and evaluation programs for waste and cleaner production.