Biological remediation of Cr(VI) contaminated soil and groundwater is an emerging field. In this study, the in situ bioremediation technology for treating Cr(VI) contaminated groundwater aquifers was evaluated using a laboratory microcosm system. The study was conducted using columns with five equally spaced intermediate sampling ports along the length to facilitate finite difference modelling of the Cr(VI) concentration profile within the column. Cr(VI) concentration was continuously measured in the influent, in five equally spaced intermediate ports within the column and in the effluent port. The change or the shift in microbial community within the inoculated column was also monitored due to exposure to toxic conditions after seven weeks of operation using the 16S rRNA genotype fingerprinting method. The effect of introducing a natural carbon source (sawdust) in inoculated columns in comparison with the performance of sterile controls under various loading conditions was also evaluated. Near complete Cr(VI) removal was achieved in an inoculated carbon source reactor, whereas only 69.5% of Cr(VI) removal was achieved in an inoculated column without an added carbon source after 4 days of operation at 20 mg/L. In a sterile control reactor less than 2% of Cr(VI) was removed after 4 days of operation at 20 mg/L. Experimental cores demonstrated a successful Cr(VI) reduction process in the simulated microbial barrier system that was evaluated internally. The model that simulates Cr(VI) removal and transport in the subsoil environment was developed. The Cr(VI) mass balance model across the reactor that accounts for the flow characteristics and biological removal mechanism successfully captured the trends of Cr(VI) response profiles under quasi-steady state conditions for different loading conditions. This study demonstrate the potential of applying effective Cr(VI) reducers in the reactive barrier systems to contain or attenuate the spread of Cr(VI) contaminant in groundwater aquifer systems. The finite difference model developed in this study to evaluate the behaviour of Cr(VI) in the reactor could contribute towards improved designs of future in situ bioremediation systems that can be implemented for remediation of Cr(VI) on site. / Dissertation (MSc)--University of Pretoria, 2011. / Chemical Engineering / unrestricted

M. Tech (Department of Chemistry, Faculty of Applied and Computer Sciences) Vaal University of Technology. / Agricultural waste such as Macadamia nutshells are currently receiving more attention for removal of hexavalent chromium (Cr(VI)). However, they have low adsorption capabilities when used in their raw form. In this study, the efficiency of using Macadamia nutshell powder modified with different concentrations of hydrogen peroxide, grafted with 1,5’-diphenylcarbizide (DPC) for the removal of hexavalent chromium from aqueous solution was explored. The effects of various parameters controlling adsorption of Cr(VI) onto Macadamia adsorbents such as initial concentration, contact time, adsorbent concentration and pH were investigated. The optimal operating parameters for Macadamia nutshells treated with hydrogen peroxide (MHP) adsorbents were determined to be 75 mg/L, 3 h, 0.1 g and pH 1. The optimal operating parameters for Macadamia nutshells treated with hydrogen peroxide and grafted with 1,5’-diphenylcarbizide (MHPD) were determined to be 150 mg/L, 1 h, 0.1 g and pH 3. Fourier transform infrared (FTIR) spectroscopy of the adsorbents revealed that treated MHP showed amino groups attached to the adsorbents. Thermogravimetric analysis (TGA) revealed that the grafted material lowered the thermal stability from 180◦C to 300◦C due to volatile nature of DPC. The surface of the MHPD materials was rough due to grafting. The results showed that the 1,5’-diphenylcarbazide treatment improved the removal efficiency of Cr(VI).

This study was designed to accomplish two primary objectives: (1) to compare two test methods commonly used to evaluate toxicity of inhaled air pollutants, and (2) to observe the response as measured by each of the methods, of pulmonary alveolar macrophages exposed to 2μg hexavalent chromium. The firs t method evaluated featured use of intratracheal injections to simulate live inhalation exposures, and the second required exposure of macrophages cultured on petri plates. Pulmonary alveolar macrophages harvested from Long Evans rats were used. The two cell function parameters measured in the evaluations were chemiluminescence and oxygen consumption (which was determined for cells at rest and during phagocytosis). These two tests have been shown to be sensitive indicators of macrophage damage. Results of CL output and oxygen consumption revealed the two methods were significantly different. Evaluation of macrophages from live animals treated with CrO3 or CaCrO4showed no differences between their respective untreated controls as determined by measurement of their chemiluminescence production or of oxygen consumption rates. Alveolar macrophages that were cultured in media during treatment with the same two forms of hexavalent chromium showed statistically significant differences from untreated controls. These comparisons indicate that choices of investigative toxicological models influence interpretation of data recorded.

No description available.

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No. of bitstreams: 2 Dissertação - Glalber Luiz da Rocha Ferreira - 2016.pdf: 1694646 bytes, checksum: 0edfdeae06383f7209358539abe161f7 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2016-08-29 / Fundação de Amparo à Pesquisa do Estado de Goiás - FAPEG / The existing techniques for removing heavy metals are expensive and are often not effective. Thus the application arises from biosorbents, an emerging technology that needs to be studied and explored, in order to promote better environmental and human life quality. The study craved verify removal capacity in synthetic aqueous solutions of ions Cr (VI) at concentrations of 10, 25, 50, 75, 100, 125 and 150 mg/L by biosorption by use of active and inactive fungal biomass Pleurotus ostreatus. In the use of the active biosorbent, kinetic studies revealed that in 336 hours was achieved 100% of its saturation capacity at concentrations of 10 and 25 mg/L of Cr (VI), achieving total removal of Cr (VI) in the order of 250 times over the recommended limit for industrial effluents in CONAMA Resolution nº 430/2011, and 360 hours biomass reached its maximum capacity of saturation, reaching values of 98,18% and 96,84%, in concentrations of 50 and 75 mg/L of Cr (VI), respectively. Observing the concentrations of 100% removal was confirmed by analysis of the total EAA chromium values of 141,66 mg/g and 133,55 mg/g biomass respectively. The analysis revealed the micrographs by SEM and TEM we observed at the cellular composition of biomass the presence of bacterial cells associated with the fungus, which on analysis was not possible to know where the metal was in adsorbed, it is better to point out that it was possible to detect content chromium from the cellular structure of the biomass. In the use of the idle biosorbent, kinetic studies showed that 6, 10 and 12 minutes it was reaching 100% of its saturation capacity at concentrations of 10, 25 and 50 mg/L of Cr (VI), respectively, achieving total removal Cr (VI) in the order of 500 times over the recommended limit for industrial effluents in CONAMA Resolution No. 430/2011, and in 22 minutes biomass reached its maximum capacity of saturation, reaching values of 73,21% and 55,13% at concentrations of 75 and 100 mg/L of Cr (VI), respectively. The Langmuir model was the one that best fit the experimental data biosorbent P. ostreatus, when evaluating the separation factor (RL), responding to values between zero and 1. Now, considering the values of the coefficient of determination (R2), the Freundlich model fit better due to present higher values in relation to the Langmuir model. / As técnicas existentes de remoção de metais pesados são caras e muitas vezes não são eficientes. Dessa forma surge a aplicação de biossorventes, uma tecnologia emergente que precisa ser estudada e explorada, com o objetivo de promover melhor qualidade ambiental e da vida humana. O estudo almejou verificar a capacidade de remoção em soluções aquosas sintéticas de íons Cr(VI) nas concentrações de 10, 25, 50, 75, 100, 125 e 150 mg/L, através da biossorção pela utilização da biomassa fúngica ativa e inativa de Pleurotus ostreatus. Na utilização do biossorvente ativo, os estudos cinéticos revelaram que em 336 horas foi alcançado 100% de sua capacidade de saturação nas concentrações de 10 e 25 mg/L de Cr(VI), alcançando uma remoção total de Cr(VI) na ordem de 250 vezes em relação ao limite preconizado para efluentes industriais na Resolução do CONAMA nº 430/2011, e em 360 horas a biomassa atingiu sua capacidade máxima de saturação, atingindo valores de 98,18% e 96,84%, nas concentrações de 50 e 75 mg/L de Cr(VI), respectivamente. Observando as concentrações de 100% de remoção, foi confirmando através da análise de EAA valores de crômio total de 141,66 mg/g e 133,55 mg/g de biomassa, respectivamente. Na análise revelada pelas microfotografias por MEV e MET foi possível verificar junto a composição celular da biomassa a presença de células bacterianas associadas ao fungo, que em análise não foi possível saber onde o metal se encontrava adsorvido, mais vale salientar que foi possível detectar conteúdo de crômio junto a estrutura celular da biomassa. Na utilização do biossorvente inativo, os estudos cinéticos revelaram que em 6, 10 e 12 minutos foi alcançando 100% de sua capacidade de saturação nas concentrações de 10, 25 e 50 mg/L de Cr(VI), respectivamente, alcançando uma remoção total de Cr(VI) na ordem de 500 vezes em relação ao limite preconizado para efluentes industriais na Resolução do CONAMA nº 430/2011, e em 22 minutos a biomassa atingiu sua capacidade máxima de saturação, atingindo valores de 73,21% e 55,13%, nas concentrações de 75 e 100 mg/L de Cr(VI), respectivamente. O modelo de Langmuir foi o que se melhor ajustou aos dados experimentais do biossorvente P. ostreatus, quando avaliando o fator de separação (RL), respondendo a valores entre zero e 1. Agora, considerando os valores do coeficiente de determinação (R2), o modelo de Freundlich se ajustou melhor, devido apresentar valores maiores em relação ao modelo de Langmuir.

Hexavalent chromium, Cr(VI), is an established human carcinogen that is a worldwide environmental health concern. It is well understood that reactive oxygen species, genomic instability, and DNA damage repair deficiency are important contributors to Cr(VI)-induced carcinogenesis. After decades of research some cancer hallmarks remain understudied for the mechanism of Cr(VI) carcinogenesis. Dysregulated cellular energetics have been established as a hallmark of cancer. Energy pathways that become dysregulated in cancer include mitochondrial respiration, lipogenesis, pentose phosphate pathway, one carbon metabolism, and increased anaerobic glycolysis in the presence of oxygen or ‘Warburg effect’. To investigate metabolism changes in Cr(VI) carcinogenesis, we exposed human lung epithelial cells (BEAS-2B cells) to Cr(VI) for six months and isolated a colony from soft agar. To confirm the results in the BEAS-2B cells, we used two other sets of Cr(VI)-transformed cells, human lung epithelial cells (BEP2D cells) and human lung fibroblasts (WTHBF-6 cells). We found increased lipogenesis related protein expressions including: ATP citrate lyase (ACLY), acetyl-CoA carboxylase 1 (ACC1), and fatty acid synthase (FASN) in Cr(VI)-transformed cells as compared to passage-matched control cells. We also observed increased palmitic acid levels, confirming that Cr(VI)-transformed cells were making more lipids. Cr(VI)-transformed BEAS-2B cells had decreased colony formation in soft agar and decreased cell growth when treated with a FASN inhibitor (C75). ACLY, ACC1, and FASN protein expressions were also increased in chromate-induced lung tumors in human tissue samples. We also observed that Cr(VI)-transformed human lung cells (BEAS-2B, BEP2D, and WTHBF-6 cells) had no major changes in their mitochondrial respiration as measured by the Seahorse Analyzer when compared to their passage-matched control cells. Conversely, xenograft tumor-derived cells had mitochondrial respiratory dysfunction. Interestingly, we also found that Cr(VI)-transformed human lung cells (BEAS-2B, BEP2D, and WTHBF-6 cells) had no major changes in their glycolytic function as measured by the Seahorse Analyzer when compared to their passage-matched control cells. Similarly, these cells did not have changes in glycolytic enzymes or extracellular L-lactate levels. Moreover, xenograft tumor-derived cells showed no changes in glycolytic endpoints or L-lactate levels. This indicates these cells did not undergo the ‘Warburg effect’. These data demonstrate that increased lipogenesis is important to Cr(VI)-induced lung carcinogenesis and are consistent with the cancer literature which reports that increased lipogenesis proteins occur during carcinogenesis. Additionally, our results indicate mitochondrial respiratory dysfunction is likely a result of the tumor microenvironment and a later step during Cr(VI) carcinogenesis. Lastly, we observed the ‘Warburg effect’ is not required for Cr(VI)-induced carcinogenesis in vitro. However, it remains to be shown if the ‘Warburg effect’ is still a consequence or contributing factor for tumorigenesis. Future studies are needed to investigate other metabolic pathways in Cr(VI)-induced carcinogenesis. In conclusion, some metabolism pathways are important to Cr(VI)-induced carcinogenesis, while others appear not to be.

<p>The RoHS Directive was introduced in order to restrict hazardous substances in Electrical and Electronic Equipment, EEE. It currently restricts the use of six hazardous substances/compounds; cadmium, lead, mercury, hexavalent chromium, PBB, and PBDE. The RoHS Directive currently includes category 1-7 and 10 in the categories of EEE listed in Annex 1A to the WEEE-Directive (Waste of EEE). The aim with the report is to investigate and elucidate prospects and obstacles to increase the scope of RoHS. This report mainly considers the inclusion of product categories 8 (Medical Devices) and 9 (Monitoring and Control Instruments). </p><p>In order to fulfil the aim eight questions were formulated, that shall be answered in the report. In order to find the knowledge of and attitude towards RoHS of manufacturers, retailers, and importers of products falling under category 8 and 9, a questionnaire was sent to 80 companies, of which 25 answered. The answers showed that many of the companies did not know of RoHS before the questionnaire was sent out. The majority did not consider that their product category needed a longer time period to find alternatives for the applications where any of the in RoHS restricted substances were used, compared with the other categories in annex 1A to WEEE. Of the companies that answered on the questionnaire the majority had less than 50 employees. The companies in the study had limited knowledge of the contents of their products, they bought the function rather than the contents. </p><p>One important conclusion in this report is that only a few of the companies in category 8 and 9 are likely to keep using non compliant components for a long time if they use standard electronic equipment irrespective if they intend to readjust their production according to the RoHS Directive or not. The reason is that most subcontractors will be forced by the customers, mainly the larger ones, to readjust their production. They certainly will not keep two production lines. A paradox problem that can arise for small and medium sized companies, the majority of those answering the questionnaire were, is to get access to compliant components before the RoHS Directive is put into force. These companies order such small batches that it is unrealistic to order them from the original manufacturer, who usually is located in Asia. The small and medium sized companies usually buy their components from middlemen/grossists in Europe and Sweden. These grossist in many cases have large stocks with non-compliant components that they want to sell out before RoHS Directive is put into force from the 1st July 2006. </p><p>The RoHS Directive has been critized for restricting lead, but different studies show that the alternatives to e.g. Lead gives only slightly worse results, which by way of introduction can be expected from a new technology compared with an old, more investigated. The work with the report has also revealed a lack in communication and cooperation not only between the different stakeholders in electronic industry: retailers, importers, manufacturers and subcontractors, but also between industry, customers and authorities. The RoHS Directive may improve the communication and cooperation between these different actors.</p>

The RoHS Directive was introduced in order to restrict hazardous substances in Electrical and Electronic Equipment, EEE. It currently restricts the use of six hazardous substances/compounds; cadmium, lead, mercury, hexavalent chromium, PBB, and PBDE. The RoHS Directive currently includes category 1-7 and 10 in the categories of EEE listed in Annex 1A to the WEEE-Directive (Waste of EEE). The aim with the report is to investigate and elucidate prospects and obstacles to increase the scope of RoHS. This report mainly considers the inclusion of product categories 8 (Medical Devices) and 9 (Monitoring and Control Instruments). In order to fulfil the aim eight questions were formulated, that shall be answered in the report. In order to find the knowledge of and attitude towards RoHS of manufacturers, retailers, and importers of products falling under category 8 and 9, a questionnaire was sent to 80 companies, of which 25 answered. The answers showed that many of the companies did not know of RoHS before the questionnaire was sent out. The majority did not consider that their product category needed a longer time period to find alternatives for the applications where any of the in RoHS restricted substances were used, compared with the other categories in annex 1A to WEEE. Of the companies that answered on the questionnaire the majority had less than 50 employees. The companies in the study had limited knowledge of the contents of their products, they bought the function rather than the contents. One important conclusion in this report is that only a few of the companies in category 8 and 9 are likely to keep using non compliant components for a long time if they use standard electronic equipment irrespective if they intend to readjust their production according to the RoHS Directive or not. The reason is that most subcontractors will be forced by the customers, mainly the larger ones, to readjust their production. They certainly will not keep two production lines. A paradox problem that can arise for small and medium sized companies, the majority of those answering the questionnaire were, is to get access to compliant components before the RoHS Directive is put into force. These companies order such small batches that it is unrealistic to order them from the original manufacturer, who usually is located in Asia. The small and medium sized companies usually buy their components from middlemen/grossists in Europe and Sweden. These grossist in many cases have large stocks with non-compliant components that they want to sell out before RoHS Directive is put into force from the 1st July 2006. The RoHS Directive has been critized for restricting lead, but different studies show that the alternatives to e.g. Lead gives only slightly worse results, which by way of introduction can be expected from a new technology compared with an old, more investigated. The work with the report has also revealed a lack in communication and cooperation not only between the different stakeholders in electronic industry: retailers, importers, manufacturers and subcontractors, but also between industry, customers and authorities. The RoHS Directive may improve the communication and cooperation between these different actors.

[pt] No presente trabalho, foram abordadas duas formas alternativas de materiais para a redução do cromo hexavalente. Para um dos materiais foram sintetizadas nanopartículas de ferro metálico, níquel metálico e sílica como suporte, e o outro material visando menor custo e maior acessibilidade foi uma lã de aço comercial. Ambos têm como objetivo a diminuição ou remediação de cromo hexavalente através de soluções de dicromato de potássio em concentrações que visam simular contaminações geradas por diversas operações industriais. A função destes materiais é de atuar como um forte agente redutor, doando elétrons para reduzir o cromo hexavalente em cromo trivalente. As nanopartículas de ferro zero valente, níquel zero valente suportadas em sílica foram sintetizadas empregando sulfatos em uma técnica de redução com borohidreto de potássio em solução aquosa. As nanopartículas foram caracterizadas com o auxílio da técnica de difração de raio-X para determinar as fases presentes, e de microscopia eletrônica de varredura com espectroscopia por dispersão de energia, definindo a composição química elementar e a morfologia das superfícies, e ICP para quantificar a composição dos elementos ferro e níquel. Finalmente, foram realizados os testes de redução do cromo hexavalente em cromo trivalente através do Espectrofotômetro UV-VIS, sendo quantificada a concentração de cromo hexavalente presente na solução através da técnica colorimétrica com o reagente altamente seletivo, o 1,5-difenilcarbazida (DFC). As nanopartículas e a lã de aço demonstraram eficiência na redução do cromo hexavalente em concentrações de 8,32 ppm (K2Cr2O7 80 Mmol/L), 6,241 (K2Cr2O7 60 Mmol/L) e 4,161 ppm (K2Cr2O7 40 Mmol/L) com tempos inferiores a 5 minutos. Contudo, as nanopartículas de Fe0-Ni0 suportadas em SiO2 reduziram o cromo hexavalente com uma quantidade em massa de Fe0 aproximadamente 110 vezes menor em relação a lã de aço, considerando que este é constituído unicamente por ferro metálico. Credita-se esta efetividade à maior área superficial por unidade de massa das partículas nanoestruturadas. / [en] In the present work, two alternative forms were approached using different materials. For one of the materials, nanoparticles of metallic iron, metallic nickel and silica as support were synthesized, and the other material aiming at lower cost and greater accessibility will be steel wool. Both have the objective of reducing or remediation of hexavalent chromium through solutions of potassium dichromate in concentrations that aim to simulate contaminations generated by various industrial operations. The function of these materials is to act as a strong reducing agent by donating electrons to reduce the hexavalent chromium to trivalent chromium. The nanoparticles of zero-valent Iron, zero-valent nickel supported on silica was synthesized using sulfates in a reduction technique with potassium borohydride in aqueous solution. The nanoparticles were characterized with the help of the XRD technique, from the diffraction pattern generated and quantifying the present phases, and SEM / EDS, defining elemental chemical composition and surface morphology and ICP to quantify the elemental composition. Finally, the tests of reduction of the hexavalent chromium in trivalent chromium through the UV-VIS spectrophotometer were carried out, and the concentration of hexavalent Chromium present in the solution was quantified through the Colorimetric technique with the highly selective reagent, 1,5-diphenylcarbazide (DFC). Nanoparticles and steel wool showed efficiency in the reduction of hexavalent chromium at concentrations of 8,32 ppm (K2Cr2O7 80 Mmol/L), 6,241 (K2Cr2O7 60 Mmol/L) e 4,161 ppm (K2Cr2O7 40 Mmol/L) with times less than 5 minutes. However, as Fe0-Ni0 nanoparticles supported in SiO2, they reduced the hexavalent content of a quantity of steel mass in relation to steel wool, considering that it consists only of metallic iron. The effectiveness in the most superficial part by the mass unit of the nanostructured particles is credited.

Orientador: Wilson de Figueiredo Jardim / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Quimica / Made available in DSpace on 2018-08-13T18:50:44Z (GMT). No. of bitstreams: 1 Franco_DeboraVilela_D.pdf: 6112505 bytes, checksum: 9ffd8531fa2a0322c7b7d08e90de70fa (MD5) Previous issue date: 2008 / Resumo: A redução química do cromo hexavalente, Cr(VI), presente em solo e água subterrânea contaminados, foi investigada empregando-se diferentes agentes redutores (batelada e semi-batelada) para avaliar a extensão da redução do Cr(VI) e da imobilização (precipitação) do cromo trivalente, Cr(III). O estudo comparativo envolvendo o uso de diferentes agentes redutores evidenciou que as espécies Fe(II) e FZVcol (nanopartículas estabilizadas com carboximetilcelulose) apresentaram os resultados mais promissores para a remoção do Cr(VI), visto que houve uma redução quantitativa desta espécie com sua concomitante imobilização. A aplicação do Fe(II) e FZVcol nas razões molares 1[Cr(VI)]:20[Fe(II)] e 1[Cr(VI)]:4[FZVcol] resultou na conversão redox superior a 98% e na imobilização das frações de Cr(VI) lábil e trocável. Foi verificado para o Fe(II), que o aumento da velocidade do fluxo volumétrico (G) resulta na diminuição do número de volume de poro para o tratamento do solo e da quantidade de Cr(VI) residual. O estudo hidrodinâmico teórico da coluna recheada com solo (meio poroso) permitiu mensurar o grau de dispersão do redutor na coluna frente ao modelo pistonado de escoamento em função de G mediante o cálculo do coeficiente de dispersão mássica volumétrico (kDV), o qual foi calculado a partir da modelagem da curva de saturação experimental. Foi verificado em todos os casos que a cinética do processo redox Cr(VI)/Cr(III) segue uma lei empírica de velocidade de pseudo-primeira ordem. A complexidade cinética do processo redox foi evidenciada pela dependência da constante de velocidade global de pseudo-primeira ordem (k*) com o tempo de reação, G e a concentração inicial do redutor. Um modelo cinético fenomenológico foi proposto para se obter uma expressão representativa de k* nas diferentes situações experimentais investigadas, bem como nos casos limites previstos. Um esquema reacional global foi proposto para representar os diferentes processos elementares envolvendo as espécies Cr(VI) e Cr(III) na matriz porosa (solo/água subterrânea). Um ensaio de tratamento em escala piloto foi realizado in situ tendo-se como balizadora as condições experimentais mais promissoras obtidas nos estudos realizados em escala laboratorial / Abstract: Chemical reduction of the hexavalent chromium, Cr(VI), present in contaminated soil and groundwater was investigated using several different reductants (batch and semi-batch) in order to evaluate the extension of Cr(VI) reduction and the immobilization (precipitation) of trivalent chromium, Cr(III). A comparative study concerning the use of different reductants revealed that Fe(II) and ZVIcol (nanoparticles stabilized with carboximethylcellulose) present the most promising findings for the Cr(VI) removal, since it was found that a quantitative reduction of this specie is accompanied by its immobilization. Application of Fe(II) and ZVIcol using the 1[Cr(VI)]:20[Fe(II)] and 1[Cr(VI)]:4[ZVIcol] molar ratios resulted in a redox conversion degree higher than 98% and in the immobilization of the labile and the exchangeable Cr(VI) fractions. It was verified for Fe(II) that increasing the volumetric flow rate (G) both the pore volume necessary for the redox treatment and the residual Cr(VI) decrease. The theoretical hydrodynamic study concerning the packed column reactor containing soil (porous medium) permitted to evaluate the reductant dispersion degree inside the column in relation to the plug-flow model as functions of G by measuring the volumetric mass dispersion coefficient (kVD), which was calculated from simulation of the experimental saturation curve. In all cases, it was found the kinetics of the Cr(VI)/Cr(III) redox process follows a pseudo-first order rate law. The complexicity concerning the kinetic process was evidenced by the dependence of the overall pseudo-first order kinetic rate constant (k*) on reaction time, G and the initial concentration of the reductant. A phenomenological kinetic model was proposed in order to obtain a relation capable to represent k* for the different experimental conditions investigated, as well for the possible limit cases. An overall reaction scheme was proposed in order to describe the different elementary processes concerning the Cr(VI) and Cr(III) species, which take place inside the porous soil matrix (soil/groundwater). A pilot scale test was carried out in situ taking into account the best experimental scenario obtained in laboratory. / Doutorado / Quimica Analitica / Doutor em Ciencias Quimicas