The objective of this research was to evaluate the treatment efficiency of a trichloroethylene(TCE)-contaminated aqueous solution and soil by combined technologies of the emulsified nanoscale zero-valent iron slurry (ENZVIS) and electrokinetic remediation process. Nanoiron was synthesized using the chemical reduction method by industrial grade chemicals. The synthesized nanoparticles contained elemental iron and iron oxide as determined by X-ray diffractmetry(XRD). Micrographs of FE-SEM have shown that a majority of nanoiron were in the size range of 30~50 nm. The stability study of food-grade soybean oil emulsion was conducted using six non-ionic surfactants and soybean oil. The results have shown that the emulsion prepared by mixed surfactants (Span 80 and Tween 40) and soybean oil yielded a better emulsion stability. Based on the above finding, the nanoiron slurry, soybean oil and aforementioned, mixed surfactants were used to prepare ENZVIS. Degradation of TCE by ENZVIS under various operating parameters was carried out in batch experiments. The experimental results have indicated that emulsified nanoiron outperformed nanoiron in TCE dechlorination rate. ENZVIS (0.75 g-Fe0/L) degradated TCE (initial conc.= 10 mg/L) down to 45 %. An increase of the oil dosage could improve the stability of the emulsion, but yielding a negative influence on degradation of TCE. Experimental results also showed that ENZVIS could remove TCE up to 94 % when pH=6. It was also formed that a higher TCE initial concentration would result in a higher TCE removal efficiency. In addition, using ENZVIS to degraded TCE-contaminated artificial groundwater has indicated that nitrate and carbonate of groundwater will suppress nanoiron reaction with TCE. Especially, a high concentration of carbonate in the reaction system might form a passive film or precipitates on nanoiron surface. This study further evaluated the treatment efficiency of combining ENZVIS and electrokinetic technology in treating a TCE-contaminated soil. Experimental conditions were given as follows:(1) initial TCE concentration in the range of 98~118 mg/kg; (2) an electric potential gradient of 1 V/cm; (3) a daily addition of 20 mL ENZVIS; and (4) a reaction time of 10 days. Experimental results have shown that an addition of ENZVIS to the anode reservoir of strongly acidic and oxidative environment would cause nanoiron to corrode rapidly and decrease TCE removal efficiency. On the other hand, an addition of ENZVIS to the cathode reservoir would enhance the degradation of TCE therein. In summary, an addition of ENZVIS to the cathod reservoir would yield the best TCE removal efficiency.

In this research, nanoscale zero-valent iron (NZVI) was synthesized using the chemical reduction method. Experimental results have revealed that nanoiron synthesized by the reagent-grade chemicals had a size range of 50-80 nm, as determined by FE SEM. BET specific surface area of thus synthesized nanoparticles was 66.34 m2/g. NZVI prepared by the industrial-grade chemicals had a broader particle size distribution (30-80 nm) and its BET specific surface area was 61.50 m2/g. Results of XRD showed that both types of NZVI were composed of iron with a poor crystallinity. Additional test results further showed that both types of NZVI had similar characteristics. NZVI prepared by the chemical reduction method tends to aggregate resulting in a significant loss in reactivity. To overcome this disadvantage, four water-soluble dispersants were used in different stages of the NZVI preparation process. Of these, Dispersant A (an anionic surfactant) has shown its superior stabilizing capability to others. An addition of 0.5 vol % Dispersant A during the nanoiron preparation process would result in a good stability of NZVI slurry (NZVIS). Degradation of trichloroethylene (TCE) by NZVIS under different atmospheres was carried out in batch experiments. Experimental results have shown that the TCE dechlorination rate increased markedly when the reaction proceeded under hydrogen gas atmosphere as compared with that of air. Methane was the primary end product with a trace amount of ethane and ethylene when the reaction was conducted under the atmosphere of H2. It was suggested that an addition of H2 to the reaction system could promote the hydrogenolysis reaction for better degradation. On the other hand, ethane was the main product when the reaction system consisted of nanoscale palladized iron and H2 atmosphere. It demonstrated that Pd-catalyzed TCE dechlorination has resulted in a direct conversion of TCE to ethane in the study. The greatest dechlorination rate was obtained when 2 g/L nanoscale palladized iron and 50 mL H2 was employed in the reaction system. Under the circumstances, the TCE (10 mg/L) removal efficiency was up to 99 % in 3 minutes. Experimental results have demonstrated that the reaction system with both nanoscale palladized iron and H2 atmosphere would promote TCE degradation rate. The culture of microorganism in soil showed minor changes to microbial community structures between the pre- and post-injection conditions. The number of microorganism colony was found to be increased after adding 1 mL NZVIS to 1 g soil. Experimental results revealed that NZVIS would not cause the inhibition or reduction of microorganism activity. Surface modification of NZVI slurry by Dispersant A could enhance its transport in saturated porous media. Sticking coefficients were determined to be 0.56 and 0.11, respectively, for bare and Dispersant A-modified NZVIS transporting in quartz sand columns. The sticking coefficient for modified NZVIS transport in soil (loamy sand) column was determined to be 0.0061. Apparently, NZVIS modified by Dispersant A would enhance the transport of NZVI in saturated porous media. The results of combining electrokinetic technology and NZVIS injection tests in horizontal soil column illustrated that the sticking coefficient was 0.00034 and the total content of iron reduced 10 wt. %. Experimental results revealed that the transport distance of NZVIS in saturated horizontal soil column would be greatly increased under electronkinetic conditions.

The objective of this research was to evaluate the treatment efficiency of a nitrate-contaminated soil by combined technologies of the injection of palladized nanoiron slurry and electrokinetic remediation process. First, nanoiron was prepared by two synthesis processes based on the same chemical reduction principle yielding products of NZVI-A and NZVI-B, respectively. Then they were characterized by various methods. Micrographs of scanning electron microscopy have shown that a majority of these nanoparticles were in the range of 50-80 nm and 30-40 nm, respectively. Results of nitrogen gas adsorption-desorption show that NZVI-A and NZVI-B are mesorporous (ca. 30-40 Å) with BET surface areas of 128 m2/g and 77 m2/g, respectively. Results of X-ray diffractometry have shown that both types of nanoiron were poor in crystallinity. Results of zeta-potential measurements indicated that NZVI-A and NZVI-B had the same isoelectric point at pH 6.0. Although NZVI-A and NZVI-B were found to be superparamagnetic, their magnetization values were low. Poly acrylic acid (PAA), an anionic dispersant, was employed for stabilizing various types of nanoiron. Then Palladium¡]ca. 1 wt% of iron¡^ was selected as catalysis to form palladized nanoiron¡]Pd/Fe¡^. Results have demonstrated that an addition of 1 vol. % of PAA during the nanoiron preparation process would result in a good stabilization of nanoiron and nanoscale Pd/Fe slurry. Batch tests were carried out to investigate the effects of pH variation on degradation of nitrate aqueous solutions. Experimental results have indicated that palladized nanoiron outperformed nanoiron in treatment of nitrate in this study. Apparently, an employment of catalyst would enhance the treatment efficiency. Further, an exponential increase of the reaction rate was found for the systems at low pH. The final stage of this study was to evaluate the treatment efficiency of combined technologies of the injection of palladized nanoiron¡]Pd/Fe¡^ slurry and electrokinetic remediation process in treating a nitrate-contaminated soil. Test conditions used were given as follows: (1) slurry injection to four different positions in the soil matrix; (2) electric potential gradient: 1 V/cm; (3) daily addition of 20 mL of palladized nanoiron (4 g/L) slurry to the injection position; and (4) reaction time: 6 days. Test results have shown that addition of palladized nanoiron slurry to the anode reservoir yielded the lowest residual nitrate concentration in soil. Namely, about 99.5% removal of nitrate from soil. On the other hand, the acidic condition of soil matrix around the anode reservoir would enhance the degradation of nitrate therein. Based on the above findings, the treatment method employed in this work was proven to be a novel and efficient one in treating nitrate contaminated soil.

The main objective of this study was to evaluate the feasibility of using nanoscale zero-valent iron (nZVI) as the source of hydrogen to enhance in situ anaerobic biodegradation of trichloroethylene (TCE). In the first part of this study, microcosms were constructed to evaluate the effects of different controlling factors [e.g., different redox conditions (aerobic and anaerobic conditions), different microorganisms (in situ microorganisms, activated sludge, and anaerobic sludge), and different sources of substrates and electron donors (phenol, cane molasses, hydrogen, and nZVI)] on TCE biodegradation. In the second part of this study, batch experiments were conducted to evaluate the feasibility of hydrogen production by nZVI and bimetallic particles. Results from the microcosm study indicate that in-situ microorganisms were capable of degrading TCE under aerobic and anaerobic conditions. Results also show that TCE removal was more effective by activated sludge and anaerobic sludge. Aerobic biodegradation of TCE was enhanced by the addition of phenol and cane molasses. Under anaerobic conditions, TCE removal could be improved when cane molasses and hydrogen were supplied. In addition, anaerobic TCE degradation was more effective with the presence of hydrogen. Results of microcosms conducted with the addition of nZVI reveal that TCE was degraded completely in both live and autoclaved microcosms. This indicates that chemical reductive dechlorination seemed to dominate the removal of TCE in microcosms. Therefore, further studies with higher TCE concentrations or lower nZVI doses need to be conducted to determine the effects of the produced hydrogen on TCE biodegradation. Results from the hydrogen production experiments indicate that efficiency of hydrogen production by nZVI ranged from 30% to 76%. Higher dose of nZVI addition resulted in higher amount of hydrogen production. The total amounts of hydrogen production were correlated with the doses of nZVI. In addition, rates and efficiency of hydrogen production by bimetallic particles were better than those of nZVI. Results of the batch experiments reveal that nZVI and bimetallic particles had good efficiency on hydrogen production. This indicates that nZVI and bimetallic particles have high potential to be used as hydrogen producers. In this study, a simple system consisted of only water and nZVI or bimetallic particles was applied to produce hydrogen. Although TCE in microcosms with nZVI addition was totally consumed by nZVI, results of microcosms with hydrogen addition demonstrated that hydrogen was able to improve the efficiency of anaerobic TCE biodegradation. Thus, it may be feasible to use nZVI as the source of hydrogen to enhance in situ anaerobic biodegradation of TCE. The advantages of using nZVI as the source of hydrogen include: (1) rapid removal of significant contaminant concentrations in the early stage of nZVI injection; (2) creation of a more reducing environment; (3) safer than liquid hydrogen, which is stored in steel containers; and (4) direct hydrogen supply without transfer of biological mechanisms compared to commercial hydrogen release compounds and other organic substrates. Results of this study suggest that biological reductive dechlorination of TCE can be enhanced if proper doses of nZVI are supplied in situ. Knowledge and comprehension obtained in this study will be helpful in designing an enhanced in situ anaerobic bioremediation system for a TCE-contaminated site.

This thesis deals with optimization and application of assays for determination of ecotoxicity of nanomaterials based on nanoscale zero-valent iron (nZVI), which are used in remedial technologies. After in situ application of nZVI, a significant decrease in toxicity of polluted environment was detected; however, a potential negative effect of nanoparticles has not been sufficiently investigated yet. Standard used tests were found to be incompatible with nZVI for toxicity determination. Specific characteristics of nZVI, such as high reactivity and sorption, complicate determining the toxicity by routinely used ecotoxicity tests. Concentration ranging from 0,1 to 10 g/l that are used in practise for decontamination were tested. These concentrations resulted in formation of turbidity, which prevented the use of standard tests. In this work, a new method has been optimized for in vitro toxicity testing of nZVI and derived nanomaterials using bacteria. The principle of this assay is determination of oxidative stress (OS). The disbalance between formation and degradation of reactive oxygen species (i.e. OS) leads to irreversible changes in biomolecules of organisms and formation of undesirable products. A toxic and mutagenic product - malondialdehyde (MDA) is formed during lipid peroxidation and it is a...

Les récents progrès en matière de nanotechnologies ont permis d'élaborer de nouveaux matériaux aux propriétés physico-chimiques uniques tels que les nanoparticules de fer zéro valent (NPFe0). Ces nanoparticules ont prouvé leur efficacité pour dégrader les composés organiques chlorés comme le trichloroéthylène (TCE), cependant leur transport dans les milieux poreux est souvent limité. Une solution pour pallier à ce problème est de modifier leur surface par adsorption de molécules organiques. Toutefois, cet enrobage modifie la réactivité des NPFe0 vis-à-vis du TCE, ce qui peut potentiellement affecter l'efficacité du traitement. Ainsi, le premier volet de cette thèse concerne l'étude de la réactivité de NPFe0 brutes ou modifiées par des polyélectrolytes anioniques vis-à-vis du TCE. Cette réactivité a été évaluée au travers des cinétiques de dégradation du TCE et de ses produits de transformation.D'autre part, les eaux souterraines contiennent souvent des espèces dissoutes réductibles pouvant réagir avec Fe0. Ces dernières peuvent affecter la réactivité des NPFe0 vis-à-vis du polluant ciblé et donc l'efficacité du traitement de dépollution. Le deuxième volet de cette thèse porte sur l'effet de deux accepteurs d'électrons (CrVI et NO3-) sur la réactivité des NPFe0 brutes et modifiées. Enfin, le troisième volet de cette thèse concerne l'évaluation de la réactivité des NPFe0 vis-à-vis du TCE dans un cas « réel », afin de valider la technique de dépollution. Une étude pilote et une application in situ ont ainsi été menées sur un site industriel dont l'eau souterraine est contaminée par le TCE (polluant ciblé) avec de fortes teneurs en CrVI et NO3-. / Recent advances in nanotechnology have led to the development of new materials with unique physicochemical properties such as nanoscale zero valent iron particles (nZVI). These nanoparticles proved their efficiency to degrade chlorinated organic compounds such as trichlorethylene (TCE), but their migration in porous media is often limited. To overcome this problem, a solution is to modify their surface by adsorption of organic molecules. However, this coating modifies the reactivity towards TCE, which can potentially affect the treatment efficiency.Thus, the first part of this PhD focuses on the reactivity of nZVI (bare or modified by anionic polyelectrolytes) towards TCE. This reactivity was evaluated through the TCE degradation kinetics rates and its transformation products.In addition, groundwaters often contain reducible species that can react with dissolved Fe0. These last species may affect the reactivity of nZVI towards the target pollutant and therefore the remediation efficiency. The second part of this PhD focuses on the effect of two electron acceptors (CrVI and NO3-) on the reactivity of bare and modified nZVI.Finally, the third part of this PhD presents the assessment of the reactivity of nZVI towards TCE in a "real" case, in order to validate the remediation process. A pilot study and in situ application have been carried out on an industrial site which groundwater is contaminated with TCE (targeted pollutant) with high levels of CrVI and NO3-.

Orientador: Jonas Contiero / Resumo: A contaminação ambiental causada por compostos orgânicos é um importante problema que afeta solos e água superficiais. Para reduzir ou remover esses poluentes, os locais contaminados são geralmente tratados com métodos físicos e químicos. No entanto, a maioria dessas técnicas de remediação é custosa e geralmente leva à remoção incompleta e à produção de resíduos secundários. A nanotecnologia consiste na produção e aplicação de estruturas extremamente pequenas, cujas dimensões estão na faixa de 1 a 100 nm, neste cenário a nanopartícula de ferro zero valente representa uma nova geração de tecnologias de remediação ambiental. É não tóxica, abundante, barata, fácil de produzir, e seu processo de produção é simples. No entanto, a fim de diminuir a tendência de agregação, a nanopartícula de ferro zero é frequentemente revestida com surfactantes. A maioria dos surfactantes é quimicamente sintetizado a partir de fontes petroquímicas, eles são persistentes ou parcialmente biodegradáveis, enquanto oferecem baixos riscos à saúde humana, esses compostos podem prejudicar plantas e animais. Para diminuir o uso de métodos químicos, a síntese e estabilização verde de nanomateriais metálicos apresentam-se como uma opção menos perigosa ao meio ambiente. Os biossurfactantes podem potencialmente substituir qualquer surfactante sintético, eles são compostos extracelulares produzidos por microrganismos, como bactérias, e cultivados em diferentes fontes de carbono, podendo ser substratoshidrofílico... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Environmental contamination caused by organic compounds is the most important challenge that affects a huge number of soils and water surfaces. To reduce or remove these pollutants, contaminated sites are usually treated using physical and chemical methods. However, most of these remediation techniques are expensive and commonly lead to incomplete removal and to the production of secondary wastes. Nanotechnology is the production and application of extremely small structures, whose dimensions are in the range of 1 to 100 nm and Nanoscale zero-valent iron represents a new generation of environmental remediation technologies, is non-toxic, abundant, cheap, easy to produce, and its reduction process requires little maintenance. Nonetheless, in order to diminish the tendency of aggregation, nanoscale zero-valent iron is often coated with surfactants. Most surfactants are chemically synthesized from petrochemical sources, they are slowly or partially biodegradable, while offer low harm to humans, such compounds can influence plants and animals. To decrease the use of chemical methods green synthesis and stabilization of metallic nanomaterials viable option. Biosurfactants can potentially replace virtually any synthetic they are extracellular compounds produced by microbes such as by bacteria and grown on different carbon sources containing hydrophobic/hydrophilic substrates. The biosurfactants have a wide variety of chemical structures and surface properties and among them is the ... (Complete abstract click electronic access below) / Doutor