Dissertations / Theses on the topic 'Soil remediation – Oxidation'

Thesis (M.S. in environmental engineering)--Washington State University, December 2008.
Title from PDF title page (viewed on Apr. 17, 2009). "Department of Civil and Environmental Engineering." Includes bibliographical references (p. 15-18).

Thesis (Ph. D.)--Washington State University, August 2009.
Title from PDF title page (viewed on Sept. 9, 2009). "Department of Civil and Environmental Engineering." Includes bibliographical references.

Sous la direction du professeur Mehmet Oturan et du professeur Hui Zhang, j’ai fini toutes les parties des thèses. Un article a été publié dans SCI et les autres parties sont prêtes à se soumettre à la revue. Maintenant, je modifie les papiers et les thèses. Les difficultés sont la détection des contaminants parce qu’il a besoin de la machine de fluorescence et de la méthode d’extraction complexe
Soil contaminated by petroleum-hydrocarbons is a serious environmental problem since it is toxic to agriculture and human. And the polycyclic aromatic hydrocarbons (PAHs) in petroleum-hydrocarbons possess carcinogenicity, teratogenicity, mutagenicity, low volatility and poor solubility properties. Moreover, PAHs are persistent in soil and difficult to be degraded. Hence, effective methods are essential to remedy soil contaminated by petroleum-hydrocarbons and particularly the PAHs. Among various remediation methods, soil washing (SW) combined with surfactant is a promising techniques since it is an economical and effective approach. This technology promotes the transformation of contaminants from soil to aqueous solution, which is especially applied for heavily contaminated soil. However, a soil washing solution highly loaded with surfactant and contaminants is produced. Therefore, effective treatment of soil washing solution is a challenge for promoting the application of surfactants and the remediation of contaminated soil. The combination of soil washing process and electrochemical advanced oxidation processes (EAOPs) constitutes an effective technique for the treatment of soil washing solution. In this paper, Tween 80 was applied as surfactant during soil washing process. The lipophilic part of Tween 80 tends to contaminants or soil particles and the hydrophilic part has tendency to the aqueous phase. Thus, Tween 80 promotes the transformation of hydrophobic organic contaminants from soil to aqueous phase. Then the soil washing solution highly loaded with contaminants and surfactant was treated by EAOPs, processes based on the generation of strong oxidant species such as hydroxyl radicals (•OH), sulfate radicals (SO4•−) and active chlorine (•Cl), are one of the most efficient methods for degrading refractory organic pollutants in soil washing solution. The effect of EAOPs including electro-oxidation (EO), electro-Fenton (EF), sulfate radical-based advanced oxidation processes (AOPs) was investigated in the degradation of petroleum-hydrocarbons. Besides, a potential advanced oxidation process including the presence of chlorine s was applied for treating soil washing solution which contains polycyclic aromatic hydrocarbons (PAHs) and Tween 80

Pyrite (FeS2) is commonly present in complex sulphide ores in significant amounts. After the enrichment of such ores by flotation, pyrite is either produced as a separate concentrate and sold to acid manufactures or removed and disposed off as tailing. Due to lack of demand from manufacturers, most of pyrites is usually disposed off as tailing. Therefore, pyrite is usually a waste from complex sulphide ores. Yet, it may be a remediation additive for calcareous soils and calcareous- alkali soils deficient in Fe and other micronutrients such as Cu, Zn and Mn. Waste pyrite may be also an alternative amendment to gypsum because of the production of sulphuric acid which is effectively used in the reclamation of calcareous alkali soils. The effectiveness of adding waste pyrite and sulphuric acid produced from waste pyrite to calcareous-alkali soil (Saraykö
y-Ankara) and calcareous soil (Gaziantep) was studied under laboratory conditions. Pure gypsum was also used as an amendment for the comparison of the effectiveness of waste pyrite in the reclamation of alkali soils. Gypsum, powder waste pyrite and sulphuric acid were applied to the soil with reference to the gypsum requirement (GR) of the soils. Greenhouse pot tests were carried out with wheat as test plant to determine the effect of waste pyrite treatment on the plant yield (wheat) and on the amount of micronutrient (Fe, Cu, Zn, Mn) essential for plant growth. Hazard potential of pyritic tailings in terms of heavy metal contamination was also taken into account. The results showed that the soil pH and exchangeable sodium percentage (ESP), indicators of alkalization, decreased upon pyrite addition to calcareous- alkali soils of Saraykö
y-Ankara. It was also found that pyritic tailings were effective in the increasing level of essential micronutrients (Fe, Cu, Zn and Mn) for plant growth in both soils. This was ascertained by the dry matter yield of the plants in the green house pot tests. Heavy metal toxicity caused by pyrite which is a rightful concern remained well below the legal limits in the soils. Thus, it was concluded that the application of pyritic tailings promoted rapid amelioration of calcareous-alkali soil (Saraykö
y-Ankara) and calcareous soil (Gaziantep) with no deleterious heavy metal contamination.

Thesis (Ph. D.)--Ohio State University, 2002.
Title from first page of PDF file. Document formatted into pages; contains xv, 179 p.; also contains graphics (some col.). Includes abstract and vita. Advisor: Franklin W. Schwartz, Dept. of Geosciences. Includes bibliographical references (p. 172-179).

Le thème principal de cette recherche est la remédiation des sols contaminés par des hydrocarbures en utilisant des traitements d'oxydation chimique à pH neutre. Les minéraux à base de fer sont susceptibles de catalyser cette réaction d'oxydation. L'étude concerne donc dans un premier temps la synthèse des minéraux réactifs contenant des espèces FeII et FeIII (la magnétite et la rouille verte) et, dans un second temps, leur utilisation pour catalyser l'oxydation chimique. Les procédés d'oxydation testés incluent l'oxydation de type « Fenton-like (FL) » et de type persulfate activé (AP). La formation de la magnétite et de la rouille verte a été étudiée par des transformations abiotiques de différents oxydes ferriques (ferrihydrite, goethite, hématite et lépidocrocite) mis en présence de cations FeII. La magnétite a été utilisée pour catalyser les oxydations (FL et AP) dans la dégradation des hydrocarbures aliphatiques et aromatiques polycycliques (HAP) à pH neutre. Une dégradation importante des hydrocarbures aliphatiques a été obtenue par ces deux oxydants, aussi bien pour des pétroles dégradés naturellement que pour un pétrole brut. L'oxydation catalysée par la magnétite a également été efficace pour la remédiation de deux sols contaminés par HAP provenant d'anciens sites de cokerie. Aucun sous-produit n'a été observé dans nos expériences d'oxydation. En revanche, une très faible dégradation des hydrocarbures a été observée lorsque les espèces FeII solubles ont été utilisées comme catalyseur. Des expériences d'oxydation ont également été réalisées en colonne. Ces études d'oxydation ont révélé l'importance du type de catalyseur utilisé pour l'oxydation, la disponibilité des HAP dans les sols et l'effet de la matrice du sol. Les résultats suggèrent que la magnétite peut être utilisée comme source de fer pour activer les deux oxydations par Fenton-like et persulfate à pH neutre. Ce travail a de fortes implications sur la remédiation par oxydation chimique in situ des sols pollués par des hydrocarbures
The main theme of this research is the use of reactive iron minerals in the remediation of hydrocarbon contaminated soils via chemical oxidation treatments at circumneutral pH. The contribution of this thesis is two-fold including the abiotic synthesis of mixed FeII-FeIII oxides considered as reactive iron minerals (magnetite and green rust) and their use to catalyze chemical oxidation. Oxidation methods tested in this study include Fenton-like (FL) and activated persulfate oxidation (AP). The formation of magnetite and green rust was studied by abiotic FeII-induced transformations of various ferric oxides like ferrihydrite, goethite, hematite and lepidocrocite. Then, the ability of magnetite was tested to catalyze chemical oxidation (FL and AP) for the degradation of aliphatic and polycyclic aromatic hydrocarbons (PAHs) at circumneutral pH. Significant degradation of oil hydrocarbons occurring in weathered as well as in crude oil was obtained by both oxidants. Magnetite catalyzed oxidation was also effective for remediation of two PAHs contaminated soils from ancient coking plant sites. No by-products were observed in all batch slurry oxidation systems. Very low hydrocarbon degradation was observed when soluble FeII was used as catalyst under the same experimental conditions. Magnetite also exhibited high reactivity to catalyze chemical oxidation in column experiments under flow through conditions. Oxidation studies revealed the importance of catalyst type for oxidation, PAHs availability in soils and the soil matrix effect. Results of this study suggest that magnetite can be used as iron source to activate both Fenton-like and persulfate oxidation at circumneutral pH. This study has important implications in the remediation of hydrocarbon polluted soils through in-situ chemical oxidation

Bibliography: leaves 166-180. Determines the effect of chromium on the soil microbial community and its activity, the biotic-abiotic mechanisms involved in chromium oxidation, and phytostabilization of chromium using plants and organic amendment in tannery-waste contaminated soil.

Made available in DSpace on 2014-12-17T15:01:24Z (GMT). No. of bitstreams: 1 CelynaKOS_DISSERT.pdf: 1291622 bytes, checksum: 6aba20d221ab35537c160d478e6ac5f7 (MD5) Previous issue date: 2010-12-16
Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior
The soil contamination with petroleum is one of the major concern of industries operating in the field and also of environmental agencies. The petroleum consists mainly of alkanes and aromatic hydrocarbons. The most common examples of hydrocarbons polyaromatic are: naphthalene, anthracene, phenanthrene, benzopyrene and their various isomers. These substances cause adverse effects on human and the environment. Thus, the main objective of this work is to study the advanced oxidation process using the oxidant potassium permanganate (KMnO4) for remediation of soils contaminated with two polyaromatic hydrocarbons (PAHs): anthracene and phenanthrene. This study was conducted at bench scale, where the first stage was at batch experiment, using the variables: the time and oxidant dosage in the soil. The second stage was the remediation conducted in continous by a fix column, to this stage, the only variable was remediation time. The concentration of oxidant in this stage was based on the best result obtained in the tests at batch, 2,464 mg / L. The results of degradation these contaminants were satisfactory, at the following dosages and time: (a) 5g of oxidant per kg soil for 48 hours, it was obtained residual contaminants 28 mg phenanthrene and 1.25 mg anthracene per kg of soil and (b) for 7g of oxidant per kg soil in 48 hours remaining 24 mg phenanthrene and anthracene 0.77 mg per kg soil, and therefore below the intervention limit residential and industrial proposed by the State Company of Environmental Sao Paulo (CETESB)
A contamina??o de solo com petr?leo ? uma das grandes preocupa??es das ind?strias que atuam no ramo e tamb?m dos ?rg?os ambientais. O petr?leo ? constitu?do basicamente por hidrocarbonetos alcanos e arom?ticos. Os exemplos mais comuns dos hidrocarbonetos poliarom?ticos s?o: naftaleno, antraceno, fenantreno, benzopireno e seus v?rios is?meros. Estas subst?ncias apresentam efeitos nocivos ao ser humano e ao meio ambiente. Logo, este trabalho tem como principal objetivo, estudar o processo de oxida??o avan?ada, utilizando o oxidante permanganato de pot?ssio (KMnO4), na remedia??o de solos contaminados com dois hidrocarbonetos poliarom?ticos (HPAs): antraceno e fenantreno. Este estudo foi realizado em escala de bancada, sendo a primeira etapa realizada experimentos em batelada, utilizando as vari?veis: tempo de remedia??o e dosagem do oxidante. Na segunda etapa, a remedia??o foi realizada em regime cont?nuo utilizando coluna de leito fixo, para esta etapa a ?nica vari?vel foi tempo de remedia??o. A concentra??o do oxidante nesta etapa, foi baseada no melhor resultado obtido nos ensaios em batelada, 2464 mg/L. Os resultados da degrada??o destes contaminantes foram satisfat?rios, nas seguintes dosagens de oxidante e tempo de remedia??o: (a) 5g de oxidante por kg de solo em 48 horas, foram obtidos contaminantes residuais de 28 mg de fenantreno e 1,25 mg de antraceno por kg de solo e (b) para 7g de oxidante por kg de solo em 48 horas restaram 24 mg de fenantreno e 0,77 mg de antraceno por kg de solo, ficando abaixo dos valores de interven??o residencial e industrial propostos pela Companhia Ambiental do Estado de S?o Paulo (CETESB)

Soil that is heavily contaminated with polycyclic aromatic hydrocarbons (PAHs) is often found at the sites of former gasworks and wood-impregnation plants. Since PAHs are toxic these sites represent a hazard to human health and the environment, and therefore they need to be treated, preferably by a method that destroys the contaminants, and thus eliminates the problem permanently. However, during biological and chemical degradation of PAHs other toxic compounds may be formed. If these transformation products are sufficiently persistent they could potentially accumulate during remedial processes. In the work underlying this thesis the degradation and transformation of PAHs were studied in three remedial processes: viz. a pilot-scale bioslurry reactor, microcosms with wood-rotting fungi and lab-scale treatments with Fenton's reagent. A group of transformation products referred to as oxygenated-PAHs (oxy-PAHs) was found to be particularly important, as these compounds are toxic and were shown to be relatively persistent in the environment. The oxy- PAHs were, for instance, found at significant concentrations in the gasworks soil used in most of the studies. This soil was highly weathered and had therefore been depleted of the more readily degradable compounds. In addition, experiments in which earthworms were exposed to the gasworks soil showed that the oxy-PAHs were more easily taken up in living organisms than PAHs. To facilitate the studies, new extraction and fractionation methods were developed. For instance, pressurized liquid extraction (PLE) was investigated for its reliability and efficiency to extract PAHs and oxy-PAHs from soil. Furthermore, a selective PLE-method was developed that can simultaneously extract and separate the PAHs and oxy-PAHs into two different fractions. This was accomplished by adding a chromatographic material (silica or Florisil) to the extraction cell. Under certain conditions all three remedial processes resulted in increasing amounts of oxy- PAHs in the soil. For example, 1-acenaphthenone and 4-oxapyrene-5-one accumulated in the bioslurry reactor. Similarly, in the soil inoculated with a white-rot fungus 9-fluorenone, benzo[a]anthracene-7,12-dione, 4-hydroxy-9-fluorenone and 4-oxapyrene-5-one accumulated. Finally, in an ethanol-Fenton treatment the concentration of some PAH-quinones increased in the soil. The results show that it might be necessary to monitor oxy-PAHs as well as PAHs during the remediation of PAH-contaminated sites. Otherwise, the soil may be considered detoxified too early in the process. In the long term it would be desirable to include analyses with sufficient marker compounds to follow the possible production and elimination of the oxy-PAHs. However, until such compounds can be identified it is suggested that contaminated soil should be screened for oxy-PAHs in general. The selective PLE-method presented in this thesis could be a useful tool for this.

Orientador: Wilson de Figueiredo Jardim
Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Química
Made available in DSpace on 2018-08-21T12:42:03Z (GMT). No. of bitstreams: 1 Marques_EmanuelJoseNascimento_M.pdf: 2293976 bytes, checksum: 7be303ab6d3a366873fc9c1c636abfbf (MD5) Previous issue date: 2012
Resumo: Neste trabalho foi avaliado um processo de lavagem de solo utilizando solução oxidante, visando a remediação de áreas contaminadas com hidrocarbonetos provenientes combustíveis. O processo foi denominado de lavagem oxidativa e consistiu na mistura de H2O2 com um catalisador de Fenton modificado, chamado Fentox®. A lavagem oxidativa foi aplicada em solo contaminado artificialmente com óleo diesel em laboratório, a fim de avaliar as mudanças ocorridas no perfil de distribuição dos hidrocarbonetos remanescentes no solo tratado e verificar as condições experimentais que resultassem em máxima remoção destes contaminantes. Foi possível obter remoção de 90% para alcanos totais, 69% para hidrocarbonetos policíclicos aromáticos (HPA) totais, e 86% para hidrocarbonetos totais de petróleo (HTP). O aumento na proporção entre fase líquida e fase sólida resultou em maior eficiência na remoção dos contaminantes. A lavagem do solo utilizando o agente tensoativo dodecil benzeno sulfonato de sódio (DBSS) foi outro aspecto investigado em laboratório. Verificou-se que em solo com baixa concentração inicial de HPA o uso do tensoativo não favoreceu a solubilização dos contaminantes. Além disso, a adição de tensoativo durante a lavagem oxidativa do solo não contribuiu para melhorar o desempenho do processo de remediação. O processo de lavagem oxidativa juntamente com solução de tensoativo foi aplicado em solo contaminado com óleos combustíveis em uma área localizada na cidade de São Paulo, a fim de remover os hidrocarbonetos presentes no local. Foi obtida redução de aproximadamente 87% do parâmetro HPA total, sendo que a extensão da remoção individual dos HPA apresentou variações, principalmente em função da hidrofobicidade característica de cada composto. A lavagem oxidativa mostrou-se uma alternativa viável sob o ponto de vista técnico, considerando que os resultados obtidos em campo foram comparáveis àqueles obtidos em laboratório
Abstract: In this work a soil washing process using oxidizing solution was evaluated, aiming the remediation of contaminated areas with hydrocarbons derived from fuels. The selected process was called oxidative soil washing and consists in the use of H2O2 with a modified Fenton¿s catalyst, called Fentox®. The oxidative washing was applied first in a laboratory diesel oil contaminated soil in order to evaluate changes in the distribution profile of hydrocarbons remaining in the treated soil and to set the experimental conditions that resulted in maximum removal of these contaminants. It was possible to obtain removals of 90% for total alkanes, 69% for polycyclic aromatic hydrocarbons (PAH), and 86% for total petroleum hydrocarbons (TPH). The increase in the liquid-solid ratio resulted in increase of the contaminant removal. The oxidative soil washing using the surfactant sodium dodecyl benzene sulphonate (SDBS) was another aspect investigated in the laboratory. It was found that in soil having low initial PAH concentration, the use of surfactant did not increase the contaminants solubilization. Furthermore, the surfactant addition during the soil oxidative washing did not improve the performance of the remediation process. The oxidative soil washing in the presence of the surfactant solution was applied in a fuel contaminated soil to remove hydrocarbons. Results indicated removal around 87 % for total PAH, with different rates according to the hydrophobicity of each compound. Oxidative soil washing proved to be a feasible alternative under the technical point of view, considering that results obtained on site were comparable to the ones obtained under laboratory conditions
Mestrado
Quimica Analitica
Mestre em Química

Recentemente, o uso de persulfato em processo de oxidação química in situ em áreas contaminadas por compostos orgânicos ganhou notoriedade. Contudo, a matriz sólida do solo pode interagir com o persulfato, favorecendo a formação de radicais livres, evitando o acesso do oxidante até o contaminante devido a oxidação de compostos reduzidos presentes no solo ou ainda pela alteração das propriedades hidráulicas do solo. Essa pesquisa teve como objetivos avaliar se as interações entre a solução de persulfato com três solos brasileiros poderiam eventualmente interferir sua capacidade de oxidação bem como se a interação entre eles poderia alterar as propriedades hidráulicas do solo. Para isso, foram realizados ensaios de oxidação do Latossolo Vermelho (LV), Latossolo Vermelho Amarelo (LVA) e Neossolo Quartzarênico (NQ) com solução de persulfato (1g/L e 14g/L) por meio de ensaios de batelada, bem como a oxidação do LV por solução de persulfato (9g/L e 14g/L) em colunas indeformadas. Os resultados mostraram que o decaimento do persulfato seguiu modelo de primeira ordem e o consumo do oxidante não foi finito. A maior constante da taxa de reação (kobs) foi observada para o reator com LV. Essa maior interação foi decorrente da diferença na composição mineralógica e área específica. A caulinita, a gibbsita e os óxidos de ferro apresentaram maior interação com o persulfato. A redução do pH da solução dos reatores causou a lixiviação do alumínio e do ferro devido a dissolução dos minerais. O ferro mobilizado pode ter participado como catalisador da reação, favorecendo a formação de radicais livres, mas foi o principal responsável pelo consumo do oxidante. Parte do ferro oxidado pode ter sido precipitado como óxido cristalino favorecendo a obstrução dos poros. Devido à maior relação entre massa de persulfato e massa de solo, a constante kobs obtida no ensaio com coluna foi 23 vezes maior do que a obtida no ensaio de batelada, mesmo utilizando concentração 1,5 vezes menor no ensaio com coluna. Houve redução na condutividade hidráulica do solo e o fluxo da água mostrou-se heterogêneo após a oxidação devido a mudanças na estrutura dos minerais. Para a remediação de áreas com predomínio de solos tropicais, especialmente do LV, pode ocorrer a formação de radicais livres, mas pode haver um consumo acentuado e não finito do oxidante. Verifica-se que o pH da solução não deve ser inferior a 5 afim de evitar a mobilização de metais para a água subterrânea e eventual obstrução dos poros por meio da desagregação dos grãos de argila.
Recently the persulfate application for in situ chemical oxidation at areas contaminated by organic compounds gained notoriety. However, the persulfate can interact with the solid matrix of the soil favoring the formation of free radicals, avoiding the oxidant access to the contaminant due to the oxidation of reduced compounds present in the soil or by changing the hydraulic properties of the soil. This research aimed to evaluate if the interactions between the persulfate solutions and three Brazilian tropical soils could eventually interfere on the persulfate oxidation capacity and if the interaction between them could modify the hydraulic properties of the soil. For such, oxidation tests were performed with soils: Latossolo Vermelho (LV), Latossolo Vermelho Amarelo (LVA) and Neossolo Quartzarênico (NQ) with persulfate solution (1 and 14 g/L) through batch tests and LV oxidation by persulfate solution (9 and 14 g/L) on undisturbed columns. The results showed that persulfate decay followed a first order model and oxidant consumption was not finite. The higher reaction rate coefficient (kobs) was observed in the reactor with LV. This higher interaction was due to the difference in the mineralogical composition and surface area. Kaolinite, gibbisita and iron oxides showed greater interaction with persulfate. The pH reduction on the reactor solution caused the aluminum and iron leaching due to dissolution of minerals. The mobilized iron may have participated as a reaction catalyst favoring the formation of free radicals although it was the major responsible for the oxidant consumption. Part of oxidized iron may have been precipitated as crystalline oxide favoring the clogged pores. As a consequence of the higher mass proportion between persulfate and soil, the kobs constant obtained in the column test was 23 times higher than the one observed on the batch test, even utilizing a concentration 1.5 times lower than bath test. There was a reduction in the soil hydraulic conductivity and the water flow proved to be heterogeneous after oxidation due to changes in minerals structure. For remediation purposes in areas with predominance of tropical soils, especially LV, the formation of free radicals may occur but an accented and not finite oxidant consumption may happen. It is verified that the pH solution should not be inferior than 5 to prevent the mobilization of metals to the groundwater and a possible pores clogging by the breakdown of the clay grains.

博士
國立臺灣大學
環境工程學研究所
100
The purposes of this study are to explore the applicability and relevance to implement persulfate oxidation as a remedial means for soil and groundwater contaminated by petroleum hydrocarbons in Penghu area. This study consisted of three main work tasks including two laboratory and one pilot-scale demonstrations. Prior to oxidation testings, priority heavy metals content of the testing soils collected from the project area was evaluated through bench-scale chemical oxidation experiments. As in the tests for the the study site, a gasoline service station, it was observed that at pH of groundwater less than 4.0, heavy metal as nickel was detected at a concentration of 1.19 mg/L in groundwater, exceeding the regulatory standard of 1.0 mg/L. When pH elevated to a level above 6.0, nickel concentration was declined to a concentration of 0.719 mg/L. It appeared that decrease in nickel concentration was attributed to the pH increases in groundwater; therefore, it appeared that decrease in pH in groundwater during oxidation treatment process was the main cause to trigger the increase of nickel concentration. As in the field pilot tests for power plant remediation, Results obtained from the bench- and pilot-scale tests reveal that persulfate is a more persistent oxidant than hydrogen peroxide and sulfate radical (SO4-‧) has longer reaction time than hydroxyl radical (OH-‧). Furthermore, it was observed that persulfate was subject to less impact by radical scavengers as CO32-, HCO3-, and Cl- than was hydrogen peroxide, and it thereby, had less soil oxidant demand in the aqueous system onsite. Data obtained from bench-scale experiments showed that persulfate oxidation provided better removal efficiency for petroleum hydrocarbons than Fenton-like reaction. Results of bench experiments revealed that nearly 90% of total petroleum hydrocarbons (TPHd) in the soil matrix was reduced through persulfate oxidation, as opposed to 41% through Fenton-like reaction. The subsequent pilot-scale testing showed that persulfate activated by either ferrous ion or hydrogen peroxide could effectively reduce TPHd concentration to below the regulatory standard within two weeks of testing period. In the course chemical oxidation, heat, low pH, and gas generated during oxidation process would not only enhance desorption of the contaminants but also elevate the solubility of the chemicals of concern. Persulfate oxidation in the pilot test was observed to elevate the solubility of TPHd by two orders of magnitude, from 1.34 mg/L in groundwater to 289 mg/L in leachate collected from the soil treatment cells. Statistical analysis of the pilot testing performed at a power-plant indicated that 71.7% of diesel fuel was reduced through persulfate oxidation, 23.5% of diesel fuel was recovered from leachate as free product, and less than 5% of diesel fuel remained in the soil. Nickel has poor sorption selectivity to soil as compared to other divalent metals and has strong tendency to dissolve in groundwater as pH declines, causing secondary site contamination, particularly in the area where the aquifer consists of nickel-rich soil. Therefore, treatability of chemical oxidation for groundwater remediation should be carefully evaluated and planned prior to implementation to prevent from adverse site impact.

The ever-increasing detection of harmful organic and inorganic compounds in habitable areas throughout the world has led to mounting research into applications and techniques for the treatment of contaminated soils, surface and groundwaters, and chemical and industrial wastewaters. Chemical oxidation technologies, in particular Fenton-based remediation systems, have exhibited considerable potential for the effective treatment and remediation of such contaminated waters and soils. The use of Fenton-based oxidation systems for the treatment of contaminated waters and wastewaters warrants the development of kinetic models capable of accurately simulating system behaviour. In this thesis, the kinetics of Fenton-mediated oxidation systems and kinetic models based on its governing reaction mechanism are investigated in order to highlight those parameters and conditions that effect Fenton chemistry and oxidation performance, and to demonstrate the application of such kinetic models to design and improve treatment systems. Experimental and simulated data describing the oxidation of formic acid by Fenton's reagent at low pH (3 to 4) and under a variety of initial conditions, operating regimes, and solution environments supports a proposed reaction mechanism that nominates the hydroxyl radical (OH) as the active oxidizing intermediate in Fenton-based oxidation systems. Laboratory experiments demonstrate that formic acid oxidation is inhibited in the presence of oxygen, and model simulations of these systems reveals that such behaviour is due to the effect organic radical intermediates and/or by-products have in assisting or hindering the redox cycling of the catalytic iron species. The critical role that iron redox cycling plays in affecting oxidation performance is further highlighted by experimental and simulated studies at alternate pHs and using different target organics, including those that react directly with iron in a redox capacity. Experiments at pH 4 reveal an increase in the redox cycling of iron and improved oxidation performance compared to pH 3 as the higher pH favours the superoxide radical, a stronger reductant than the hydroperoxyl radical that predominates at pH 3. Other laboratory and modelling studies on the Fenton-mediated oxidation of certain aromatic compounds highlight the manner in which quinone and quinone-like compounds, being added directly or generated as oxidation by-products, can improve oxidation performance via redox reactions with iron. Further simulations reveal the type of practical design and operating information kinetic models can provide for treatment processes, though it is noted an appropriate understanding of the oxidation mechanism of the target species is necessary for the accurate application of the model.

Petroleum hydrocarbons (PHCs) such as gasoline are ubiquitous organic compounds present at contaminated sites throughout the world. Accidental spills and leakage from underground storage tanks results in the formation of PHC source zones that release hundreds of organic compounds, including the high impact, acutely toxic and highly persistent aromatics (e.g., benzene, toluene, ethylbenzene, xylenes, trimethylbenzenes and naphthalene) into groundwater. Contamination by these compounds continues to persist until the PHC source zone is treated in place or removed. In situ chemical oxidation (ISCO) employing persulfate was identified as a potentially viable technology for the treatment of PHC source zones. The effectiveness and efficiency and, therefore, the overall economic feasibility of a persulfate-based ISCO treatment system depend upon the reactivity of the target organic compounds and the interaction of persulfate with aquifer media. The objective of this research was to investigate the persistence of unactivated and activated persulfate in the presence of aquifer materials, and to examine persulfate oxidation of PHC compounds at both the bench- and pilot-scales. A series of bench-scale studies were performed to estimate persulfate degradation kinetic parameters in the presence of seven well-characterized, uncontaminated aquifer materials and to quantify the changes in specific properties of these materials. Batch experiments were conducted in an experimental system containing 100 g of solids and 100 mL of persulfate solution at 1 or 20 g/L. Column experiments were designed to mimic in situ conditions with respect to oxidant to solids mass ratio and were performed in a stop-flow mode using a 1 g/L persulfate solution. The degradation of persulfate followed a first-order rate law for all aquifer materials investigated. An order of magnitude decrease in reaction rate coefficients was observed for systems that used a persulfate concentration of 20 g/L as compared to those that used 1 g/L due to ionic strength effects. As expected, the column experiments yielded higher reaction rate coefficients than batch experiments for the same persulfate concentration due to the lower oxidant to solids mass ratio. Bench-scale data was used to develop a kinetic model to estimate the kinetic response of persulfate degradation during these tests. The push-pull tests involved the injection of persulfate (1 or 20 g/L) and a conservative tracer into a hydraulically isolated portion of the sandy aquifer at CFB Borden, Canada. The kinetic model developed from the bench-scale data was able to reproduce the observed persulfate temporal profiles from these push-pull tests. This implies that persulfate degradation kinetics is scalable from bench-scale to in situ scale, and bench tests can be employed to anticipate in situ degradation. The estimated reaction rate coefficients indicate that persulfate is a persistent oxidant for the range of aquifer materials explored with half lives ranging from 2 to 600 days, and therefore in situ longevity of persulfate will permit advective and diffusive transport in the subsurface. This is critical for successful delivery of oxidant to dispersed residuals in the subsurface. Activation of persulfate is generally recommended to enhance its oxidation potential and reactivity towards organic compounds. This approach may influence the stability of persulfate-activator system in the presence of aquifer materials. A series of batch tests were performed to investigate persistence of persulfate at two concentrations (1 or 20 g/L) using three contemporary activation strategies (citric acid chelated-ferrous, peroxide and high pH ) in the presence of 4 well-characterized, uncontaminated aquifer materials. Chelation by citric acid was ineffective in controlling the interaction between persulfate and Fe(II) and a rapid loss in persulfate concentration was observed. Higher Fe(II) concentration (600 mg/L) led to greater destabilization of persulfate than lower Fe(II) concentration (150 mg/L) and the persulfate loss was stoichiometrically equivalent to the Fe(II) concentration employed. Subsequent to this rapid loss of persulfate, first-order degradation rate coefficients (kobs) were estimated which were up to 4 times higher than the unactivated case due to the interaction with Fe(III) and CA. Total oxidation strength (TOS) was measured for peroxide activation experiments and was observed to decrease rapidly at early time due peroxide degradation. This was followed by slow degradation kinetics similar to that of unactivated persulfate implying that the initial TOS degradation was peroxide dominated and the long-term kinetics were dominated by persulfate degradation. The kobs used to capture TOS degradation for later time were shown to depend upon unactivated persulfate and peroxide degradation rate coefficients, and peroxide concentration. Either a slow peroxide degradation rate and/or higher peroxide concentration allow a longer time for peroxide and persulfate to interact which led to kobs ~1 to 100 times higher than kobs for unactivated persulfate. For alkaline activation, kobs were only 1 to 4 times higher than unactivated persulfate and therefore alkaline conditions demonstrated the least impact on persulfate degradation among the various activation strategies used. For all activation trials, lower stability of persulfate was observed at 1 g/L as compared to 20 g/L due to insufficient persulfate and/or ionic strength effects. A series of batch reactor trials were designed to observe the behavior of the nine high impact gasoline compounds and the bulk PHC fraction measures subjected to various persulfate activation strategies over a 28-day period. This bench-scale treatability used unactivated persulfate (1 or 20 g/L) and activated persulfate (20 g/L). Activation employed chelated-Fe(II), peroxide, high pH or two aquifer materials as activators. No significant oxidation of the monitored compounds was observed for unactivated persulfate at 1 g/L, but 20 g/L persulfate concentration resulted in their near-complete oxidation. Oxidation rates were enhanced by 2 to 18 times by activation with peroxide or chelated-Fe(II). For alkaline activation, pH 11 trials demonstrated ~2 times higher oxidation rates than the unactivated results. For pH 13 activation the oxidation rates of benzene, toluene and ethylbenzene were reduced by 50% while for the remaining monitored compounds they were enhanced by 5 to 100%. Natural activation by both aquifer materials produced oxidation rates similar to the unactivated results, implying that either activation by minerals associated with aquifer material was not significant or that any potential activation was offset by radical scavenging from aquifer material constituents. Acid-catalyzation at pH <3 may enhance oxidation rates in weakly buffered systems. Oxidation of the monitored compounds followed first-order reaction kinetics and rate coefficients were estimated for all the trials. Overall, activated and unactivated persulfate appear to be suitable for in situ treatment of gasoline. Persulfate under unactivated or naturally activated conditions demonstrated significant destruction of gasoline compounds and showed higher persulfate persistence when in contact with aquifer solids as compared to chelated-Fe(II) or peroxide-activated persulfate systems. This observation was used as the basis for selecting unactivated sodium persulfate for a pilot-scale treatment of gasoline-contaminated source zone at CFB Borden, Canada where a ~2000 L solution of persulfate (20 g/L) was injected into a PHC source zone. Concentration of organics and inorganics were frequently monitored over a 4 month period across a 90 point monitoring fence line installed down-gradient. Treatment performance was measured by estimating organic and inorganic mass loading across the monitoring fence. Increased mass loading for sodium was observed over time as the treatment volume moved across the fence-line indicating transport of the inorganic slug created upon oxidant injection. The mass loading also increased for sulfate which is a by-product generated either due to persulfate degradation during oxidation of organic compounds or during its interaction with aquifer materials. Oxidation of organic compounds was evident from the enhanced mass loading of dissolved carbon dioxide. More importantly, a significant (45 to 86%) decrease in mass loading of monitored compounds was observed due to oxidation by injected persulfate. The cumulative mass crossing the monitoring fence-line was 20 to 50% lower than that expected without persulfate treatment. As the inorganic slug was flushed through the source zone and beyond the monitoring fence, the mass loading rate of sodium, sulfate and carbon dioxide decreased and approached background condition. Mass loading of the monitored compounds increased to within 40 to 80% of the pre-treatment conditions, suggesting partial rebound. These investigations assessed the impact of activation on persulfate persistence and treatability of gasoline and served to establish guidelines for anticipating field-scale persulfate behavior under similar conditions. In summary, unactivated persulfate is a stable oxidant in the presence of aquifer materials and its persistence depends upon TOC and Fe(Am) content of the materials, ionic strength, and aquifer to solids mass ratio. Persulfate exhibits significant destruction of gasoline compounds and can be employed for the remediation of gasoline-contaminated sites. Peroxide and chelated-Fe(II) enhance oxidation rates of these compounds, but reduce stability of the persulfate-activator system. Persulfate activation using high pH conditions does not significantly impact persulfate persistence but reduces the overall destruction of gasoline compounds. Therefore, activation imposes a trade-off between enhanced oxidation rates and reduced persulfate persistence. Kinetic model is representative of persulfate degradation at bench- and pilot-scales and can be used for estimation of in situ degradation. The quantification of oxidation rates for gasoline compounds under activated and unactivated persulfate conditions will assist decision-making for identification of appropriate remediation options when targeting contamination by gasoline or by specific high impact gasoline compounds. While persulfate oxidation resulted in partial treatment of a small gasoline source zone, aggressive persulfate load will be required during injection for a complete clean-up. Overall, persulfate-based in situ chemical oxidation was demonstrated to be an effective and a viable technology for the remediation of contaminated soil and groundwater.

Corrigenda inside front cover.
Includes bibliographical references (leaves 205-232)
xii, 232, [27] leaves : ill., plates ; 30 cm.
Title page, contents and abstract only. The complete thesis in print form is available from the University Library.
Thesis (Ph.D.)--University of Adelaide, Dept. of Soil and Water, 2002