Thesis. 1978. Ph.D. cn--Massachusetts Institute of Technology. Dept. of Chemistry. / Includes bibliographical references. / Ph.D.cn

No description available.

Chloride diffusivity in high performance concrete is influenced by the exposure environment, aside from the concrete mixture properties like, water to cementitious ratio (w/cm) and presence of add-on pozzolans. In this study, a set of concrete specimens (eleven-different concrete mixtures) were cast and exposed to three different environmental conditions (Tidal, Splash and Barge) in which the solution was seawater or brackish water. These exposures simulated environmental field conditions. After the specimens had been wet cured for 32 days (on average), the specimens were exposed to three different field simulation conditions for up to 54 months. The specimens under the field simulated conditions were cored at 6, 10, 18, 30 and 54 months at four elevations and then the chloride profiles were obtained from the cores. The apparent diffusivity values for each profile were calculated based on Fick’s 2nd law. Then, the aging factor “m” was calculated by regression analysis of the diffusivity values vs. time (days) plotted in the log10-log10 scale. This was done for samples exposed to the three different exposure conditions and then the results were compared side-by-side. First, the “m” values were calculated using the exposure duration. Then, to study the effect of including the curing time on “m” value, the curing time was added to the exposure time and a new calculation and “m” value was obtained and compared with the previous results. Moreover, upon inspecting the chloride diffusivity values vs. time plots, it was observed that in some cases, a number of data points showed significantly higher or lower values in comparison with the rest of the data points. It was decided to recalculate the “m” values for these cases, and to only use selected data points instead of all data points (i.e., remove outlier data points). In terms of chloride diffusivity value, it was found that in most cases the specimens with higher water to cementitious (w/cm) ratio showed higher diffusivity, as expected. Further, the presence of pozzolans had a noticeable impact on the chloride diffusivity by decreasing the diffusion rate due to microstructure changes that occurred with time. In terms of “m” values, the result for the field simulated conditions showed a range of “m” values dependent on the specimen’s mixture composition and the elevation at which the specimens were cored. It was observed that the chloride diffusivity declined with time and after a certain amount of time (in this research, almost after 30 months) the diffusivity reduction became small and a transition in the slope of the diffusivity trend appeared in a number of cases. After the transition, the diffusivity trend reached either a plateau zone or continued with a significantly lower slope, depending on the time, composition and exposure. It was found that the specimens under tidal and splash field simulation conditions that had only fly ash in their mixtures showed higher “m” values when compared with samples that contained fly ash and silica fume or fifty percent slag. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2019. / FAU Electronic Theses and Dissertations Collection

Development of a rapid method for the detection of fecal enterococci and pathogenic microorganisms in beach water was attempted utilizing an evanescent wave fiber optic biosensor. Various assay formats including a sandwich immunoassay were tested in the development of a rapid assay. Fluorophore labeled antibodies were used for specific detection of bacteria captured or adsorbed directly to the surface of a polystyrene fiber optic waveguide. Binding of the fluorescent labeled antibody to its specific target or binding of a fluorescent labeled anti-IgG within 100-1000 nm of the waveguide surface caused excitation of the fluorescent conjugate resulting in a quantifiable signal. Enterococcus faecalis, Staphylococcus aureus, Escherichia coli O157:H7, and Vibrio cholerae were used as model organisms for biosensor detection in phosphate buffered saline and seawater. Seawater samples were selectively enriched for the presence of these model organisms, which were later detected on the biosensor. The sensitivity and specificity of the biosensor was examined by testing various assay formats, sample preparations, and molecules for capture and detection. Finally, an enrichment protocol combined with filter concentration was utilized to enhance detection of low levels of enterococci. The fiber optic biosensor has the potential to be a sensitive and specific system for the detection of fecal enterococci. The lower limit of detection in seawater and phosphate buffered saline was 2.8 x 106 CFU/ml. As few as 6 CFU/100ml (0.06CFU/ml) could be detected in seawater following a 14-24 hour enrichment and concentration step. Vibrio alginolyticus was found to grow under the same enrichment conditions as the enterococci. V. alginolyticus crossreacted with the polyclonal anti-Strep group D antibody used in the immunoassay at high cell concentrations. Staphylococcus aureus was the only other organism which showed significant cross-reactivity with this antibody. The biosensor was also able to detect other bacterial pathogens in PBS and seawater. The lower limit for detection of E. coli O157:H7 was 3.6 x 105 CFU/ml. The lower limit for detection of Vibrio cholerae O1 was 1.3 x 108 CFU/ml. The antibodies used in these assays were found to crossreact with other gram negative microorganisms. The biosensor was not able to detect Staphylococcus aureus.

This thesis reports a research of the corrosion mechanism and corrosion rate of steel reinforcement in concrete. Experimental results are presented to compare the corrosion behaviours of steel reinforcement in two blended-cement concretes in seawater. The experimental program included a study of the influence of crack width on macrocell corrosion, an investigation of the procedure for the determination of polarisation curves of steel in concrete and, an evaluation of the corrosion rate of steel in concrete and the influence of crack width as determined by a new polarisation curve analysis. A mechanism is proposed to interpret the different influences, in both the short and long term, of concrete crack width on the macrocell corrosion rate. This mechanism is based on the finding that the corrosion-spread phenomenon is caused by polarisation effects. An oxygen-depletion mechanism is also proposed to explain the much lower macrocell corrosion rate in the slag cement concrete than that in the flyash cement concrete. The procedure for polarisation testing of steel in concrete is found to be critical to obtaining correct polarisation curves. A twotest procedure is verified to be an appropriate procedure and used in this investigation. Experimental polarisation curves of steel in concrete are found to be very different to those expressed by the kinetic Butler-Volmer equation and, this is considered to be a result of the influence of the passive film on the steel surface in concrete. An empirical polarisation formula is developed and its interpretation is based on the postulation of two parallel kinetic processes occurring at the steel/passive-film/concrete interface; one is the active corrosion process and the other is the film growth/dissolution process. The formula is used to model experimental polarisation curves of steel in concrete through curvefitting analyses. Good curve-fitting results are obtained between the polarisation test curves and model curves. The results are used for evaluation of the corrosion rate and Tafel behaviours of steel in the two concretes and for assessment of the influence of crack width on the corrosion rate within the crack zone.

Graduation date: 1963

Electrodialysis (ED) experiments were conducted on reverse osmosis (RO)-concentrated solutions of NOM from six rivers. The ED processes successfully recovered 88 11% of TOC, and removed 83% 19% of SO42- and 67% 18% of H4SiO4. More importantly, the molar ratios of SO42- /TOC and H4SiO4 /TOC were reduced to a mean value of 0.0046 and 0.032, respectively, surpassing the goal for removal of SO42- (0.008) and almost achieving the goal for removal of H4SiO4 (0.021). The ED process can lower the SO42- /TOC ratio in samples whose initial SO42- /TOC ratios are already far below the limit of 0.008 used in this study. The coupled RO/ED process that has been described here offers a fast, simple, chemically mild (relative to other methods), and reproducible method of isolation of large quantities of relatively unfractionated, low-ash NOM from freshwaters. RO/ED was also successfully used for isolating and concentrating marine dissolved organic matter (DOM). The effort successfully recovered a median of 72% of the TOC from 200 L samples within six to nine hours of processing through a combination of ED and RO, greatly exceeding the current norm of 30%. The relatively high recovery of DOM implies that classes of DOM previously missing are included in these samples and should yield new insight into the chemistry of marine DOM. Freshwater samples processed by electrodialysis were analyzed for elemental composition and by capillary zone electrophoresis (CZE), 1H and 13C nuclear magnetic resonance spectroscopy (NMR), and electro-spray ionization mass spectrometry (ESI-MS). Bulk elemental composition, 1H- and 13C-NMR, and ESI-MS data provide evidence linking bioavailabilty to the bulk chemistry of NOM: the H/C and N/C molar ratios are positively and strongly correlated with bioavailability, as hypothesized. Using an independent dataset (STORET) of water quality parameters, calculated BOD/TOC ratios were found to be moderately correlated with measured bioavailabilities and can be used as a surrogate for bioavailability of geochemically diverse riverine DOM.

Waste oil emulsions are generated in several manufacturing processes. Such emulsions not only affect the efficacy of wastewater treatment but also influence the water quality of the effluent. Therefore, these waste oil emulsions that have to be treated before being released into the environment. Many processes have been developed for demulsifying such materials and microwave irradiation has been shown to be most effective in this respect. It does not require the addition of chemicals and the oil recovered from the emulsion can be reused. With microwave irradiation, there are two main mechanisms occurring simultaneously. One is the rapid increase of temperature which reduces the viscosity of the emulsion. The other is molecular rotation, which neutralizes the Zeta potential because of the rearrangement of electrical charges surrounding the water droplets. Hence, water droplets coalesce and result in the separation of the emulsion. Addition of inorganic salts has also been shown to improve the efficiency of microwave irradiation in demulsification owing to an increase in solvent conductivity, which accelerates the heating rate. This process is termed salt-assisted microwave irradiation. In the present study, we propose that NaCl and artificial seawater can be an economical source of cations required in salt-assisted microwave demulsification. Our experiments included batch tests of emulsion characteristics and the effects of microwave operating conditions on demulsification rate and separation efficiency of three oil-in-water (O/W) emulsions (mineral oil, vegetable oil, and mineral-oil/vegetable-oil mix). First study was aimed to examine the demulsification of an O/W cutting oil emulsion with the addition of NaCl under microwave irradiation. This work investigates the effect of a set of operating variables, including irradiation time, irradiation power, dosage of NaCl, settling time, pH and the initial oil concentration, on the separation efficiency in the treatment of an oil in water (O/W) type cutting oil emulsion by microwave assisted demulsification. As a result of a series of batch demulsification tests a set of optimum operating conditions was found, consisting of 2 min of microwave irradiation at 280 W, the addition of 14 g/L of NaCl, 60 min settling time, and at a pH of 9.5. A separation efficiency of 93.8% was obtained with these conditions for 50 mL of cutting oil emulsion with an initial oil content of 10 g/L. The objective of the second study was to examine the demulsification of an O/W cutting oil emulsion, an olive oil emulsion, and a 1:1 cutting-oil/olive-oil emulsion mix, using a proposed process termed as seawater-assisted microwave irradiation demulsification. We conducted batch demulsification tests on 50-mL aliquots with an initial oil content of 10 g/L, and found that the separation efficiencies of a cutting oil emulsion, an olive oil emulsion, and a cutting-oil/olive-oil mix reached 93.1%, 92.6%, and 93.2%, respectively, using our optimum operating conditions, which were 40 sec of microwave irradiation at 700 W, a 60 min settling time, and addition of 12%, 32%, and 20% (all v/v) of artificial seawater, respectively. Using this set of operating conditions, a decrease in solution pH was found to significantly increase the demulsification efficiency after addition of inorganic acid, whereas an increase in the concentration of surfactant, sodium dodecyl sulfate (SDS), resulted in a decrease in efficiency. In addition, our test data were explored using a stepwise regression method, yielding a multi-variable equation. This empirical equation was able to describe separation efficiency rather well, after exclusion of tests showing separation efficiency below 40% and temperature higher than the boiling point. This study could provide essential information related to O/W emulsions using salt-assisted microwave demulsification.

Abstract ¡@¡@The present study was undertaken to understand the accumulation of PCBs in the marine environment of Taiwan. Samples including oyster drills, oysters, sediments and seawater were collected from the West coast of Taiwan and analyzed by GC/ECD and GC/MS. ¡@¡@The concentration of PCBs in sediments was 31.05¡ã406.38 pg/g dry wt with the highest one at Tong-Kung. The PCBs in cultural oysters from Tong-Kung was 3.80 pg/g wet wt. Concentrations of PCBs in wild oysters from Tai-Si, Chi-Ku, and Pu-Dai were 123.57 pg/g wet wt, 2.93 pg/g wet wt, and 2.08 pg/g wet wt, respectively. The concentrations of PCBs in snails were in the range of 78.24 to 796.96 pg/g wet wt with the highest one from Tong-Kung. A positive correlations between the concentrations of PCBs in seawater and sediment (r=0.78; p<0.01) and in oysters and snails were also observed(r=0.79; p<0.01). The bioaccumulation of PCBs from seawater to oysters was about 72 times, and the biomagnification of PCBs from oysters to snails was 10 times.

This work addresses the problem of using seawater for cooling and the associated environmental problems caused by the usage and discharge of biocides. The discharged biocide and its byproducts are toxic to aquatic lives and must be decreased below certain discharge limits on load prior to discharge. The conventional approach has been to add biocide removal units as an end-of-pipe treatment. This work introduces an integrated approach to reducing biocide discharge throughout a set of coordinated strategies for inplant modifications and biocide removal. In particular, process integration tools are used to reduce heating and cooling requirements through the synthesis of a heat-exchange network. Heat integration among process of hot and cold streams is pursued to an economic extent by reconciling cost reduction in utilities versus any additional capital investment of the heat exchangers. Other strategies include maximization of the temperature range for seawater through the process and optimization of biocide dosage. This new approach has the advantage of providing cost savings while reducing the usage and discharge of biocides. A case study is used to illustrate the usefulness of this new approach and the accompanying design techniques.