Actuellement, 80 à 85% des cuirs sont tannés au chrome. Ce procédé permet d'obtenir d'excellentes propriétés physico-mécaniques dans des conditions économiques optimales. Les sels de chrome sous forme trivalente utilisés lors de la fabrication du cuir ne sont pas nocifs; cependant sous certaines conditions et associés à d'autres substances, le chrome trivalent peut se transformer en chrome hexavalent, très allergisant et pouvant s'avérer dangereux pour la santé du consommateur. Depuis le 1er mai 2015, la présence de chrome hexavalent dans le cuir est soumise à la législation européenne; la teneur en chrome hexavalent ne doit pas excéder plus de 3 mg/kg de poids sec total du cuir (REACh ANNEXE 17, §47). A ce jour, de nombreux travaux de recherche ont été réalisés et des premières hypothèses ont été avancées pour expliquer la formation du chrome hexavalent dans le cuir. L'objectif de ce projet de recherche a été de rationaliser et d'approfondir ces différentes études pour essayer de mieux appréhender cette problématique. Ce projet de thèse a permis d'améliorer la spécificité et la fiabilité la méthode d'analyse pour la détermination de la teneur en chrome hexavalent en introduisant la chromatographie ionique. Ensuite, l'influence de la composition du cuir (matière grasse, indice d'iode, pH, chrome total et chrome extractible) sur la formation de chrome hexavalent dans le cuir a été étudiée afin d'expliquer l'origine et d'éventuels mécanismes d'oxydation du chrome trivalent (en chrome hexavalent). Enfin, cette étude s'est intéressée aux facteurs environnementaux (température, humidité relative, lumière et durée d'exposition), aux conditions de fabrication du cuir ou encore au cycle de vie du cuir (transport, transformation en produit fini, utilisation par le consommateur) afin de déterminer l'impact de ces paramètres sur la formation du chrome hexavalent. A l'issue de ce travail, une méthode de vieillissement "artificiel" représentative de l'évolution réelle d'un cuir a été proposée, et ce quelles que soient les caractéristiques et la nature du cuir / Currently, 80 to 85% of leather is tanned with chrome. This process allows to obtain excellent physico-mechanical properties with optimum economic conditions. The chromium salts in trivalent form used in the manufacturing of leather are not harmful; however under some conditions and associated with other substances, trivalent chromium can be transformed into hexavalent chromium, highly allergenic and potentially harmful to the health of the consumer. Since 1st May 2015, the presence of hexavalent chromium in leather is subject to European legislation; the hexavalent chromium content must not exceed 3 mg/kg of the total dry weight of leather (REACh ANNEX 17, § 47). To date, a great amount of research has been done and initial hypothesis have been able to explain the formation of hexavalent chromium in leather. The objective of this research project was to rationalize and to deal with these various studies in order to understand this problem in more detail. In this thesis project, the introduction of ion chromatography has improved the specificity and reliability of the analysis method for the determination of hexavalent chromium. Secondly, the influence of leather composition (fat liquor, iodine value, pH, total chromium and extractible chromium) on the formation of hexavalent chromium in leather was studied. The objective was to explain the potential oxidation mechanisms of trivalent chromium (in hexavalent chromium). The third part of this study deals with environmental factors (temperature, relative humidity, light and duration of exposure), leather manufacturing conditions or the life cycle of leather (transport, transformation into finished product, consumer use). The aim was to determine the impact of these parameters on the formation of hexavalent chromium. To conclude, an "artificial" ageing method representing the natural evolution of leather, and which corresponds to the characteristics and the nature of the leather, has been proposed

In 2003, the European Community Obligation (directive 2003/5C/EC) regulates a maximal value of soluble hexavalent chromium to 0.0002 % (per weight of dry cement). This limitation leads to modifications of the regular Portland cement by using of suitable reduction agents. Therefore, the possibilities of chromium reduction become a very actual topic. The primary goal of this work is a basic research of the ferrous sulphate influence on hexavalent chromium reduction and also its influence on Portland clinker hydration process. The reduction ability was determined by UV/VIS method. The mechanism and ferrous sulphate influence on Portland clinker hydration process was observed by isothermal calorimetry and mechanical strength tests. XRD method, SEM-EDS analysis and Raman microscopy were used for identification of formed hydration products. Study of hydration mechanism occurring in this system was focused on the divergence observations from the regular Portland cement hydration. Pore solution analysis provided significant information about chromium behavior during the hydration process (substitution and releasing). Chromium incorporation into structure of hydration products during the reduction process was also studied in the pure tricalciumaluminate system with targeted Cr6+ content. This work suggests the possible substitution of the trivalent and hexavalent chromium into structure of monosulphate (AFm) phase.

D. Tech (Department of Chemistry, Faculty of Applied and Computer Sciences) Vaal University of Technology. / Trivalent arsenic (As(III)) and hexavalent chromium (Cr(VI)) toxicity have necessitated a great deal of research into the remediation of contaminated water. The techniques applied including oxidation, coagulation-flocculation and ion exchange have suffered drawbacks due to the high cost of materials and equipment, complex operations and secondary pollution among others. Adsorption, however, remains a cost-effective solution in the remediation of contaminated water. The use of biosorbent materials further lowers the cost of the adsorption process and improves its eco-friendliness. These biomaterials, however, suffer some drawbacks as poor porosity, low adsorption capacities and mechanical strength thus require modifications to improve their applicability as biosorbents. In this work pine cone powder, a waste from pine trees, was used as a biosorbent for the removal of As(III) and Cr(VI) from water. The powder was pre-treated with Fenton’s reagent to oxidize some of the functional groups and provide more binding sites. Iron oxide magnetic nanoparticles (magnetite) were incorporated into the pine cone matrix to form a magnetic composite with higher heavy metal affinity. The magnetite nanoparticles were also doped with manganese to improve their redox capacities and aid in the oxidation of the toxic As(III) to the less toxic As(V) and allow for improved binding. The adsorbents used in the study were therefore named as Fenton’s treated pine cone powder (FTP), pine cone -magnetite composite (FTP-MNP), magnetite nanoparticles (MNP), manganese doped magnetite nanoparticles (Mn MNP) and manganese doped pine cone-magnetite composite (Mn FTP-MNP). The prepared materials were fully characterized, and the adsorption process was optimized for both As(III) and Cr(VI) removal from aqueous solution. After modification the surface area of the particles increased in the order Mn MNP>MNP>Mn FTP-MNP>FTP-MNP>FTP. Surface and Xray analysis confirmed the formation of magnetite by the presence of both ferric and ferrous ion states on the surface and characteristic diffraction peaks for magnetite. The adsorption data was fitted into isotherm and kinetic models and the nature of adsorption was determined from the thermodynamic and kinetic parameters. Equilibrium studies indicated that the adsorption followed Langmuir isotherm for all adsorbents and was thus monolayer in nature, further analysis indicated that chemisorption was the predominant type of adsorption with ion exchange being the predominant mechanism of adsorption. Spent adsorbents were tested for reusability and displayed excellent adsorption capacities when used for up to three times. Adsorption mechanism was evaluated using characterization techniques and the ion-exchange mechanism inferred from thermodynamic data was confirmed spectroscopically with redox reactions aiding in the removal of the pollutants from water. The introduction of competing anions in solution, lowered the adsorption efficiency of both arsenic and chromium on the adsorbent indicating that there was competition for adsorption sites.

Research efforts in aquatic toxicology have historically centered on the chemical analyses and toxic effects of waters to aquatic organisms. More recently, sediment-source toxicity has been explored, with efforts concentrated on establishing sensitive and accurate methodologies. This study focused on the toxicity of trivalent chromium, hexavalent chromium, and fluoranthene to Pimephales promelas, Ictalurus punctatus, and Lepomis macrochirus. Test fish were exposed to both water-borne and sediment-source toxicants for 96 hours (h) and 30 days (d). A 96-h and 30-d LC50 (mg/L Cr, ug/L Fluoranthene) was determined for each fish species exposed to aqueous toxicants. In addition, 96-h and 30-d LC50s were determined for each fish species from sediment chromium concentrations (mg/kg) and sediment fluoranthene concentrations (ug/kg). Although lethality endpoints were used throughout this research, acute effects other than mortality were determined for Lepomis macrochirus exposed to hexavalent chromium. Lethal toxicity values (96-h and 30-d LC50 and their 95% confidence limits) for trivalent chromium could not be determined since trivalent chromium concentations above 6.0 mg/L could not be obtained at water pHs compatible with these fish species. Trivalent chromium addition to test waters at pHs compatible with fish survival resulted in a chromium precipitate that was not lethal to test fish. In contrast, fathead minnows, channel catfish, and bluegill sunfish exposed to hexavalent chromium in water and sediments experienced mortality. Fathead minnows exposed to fluoranthene in water for 96h demonstrated a maximum mortality of 69%, while 100% mortality was achieved with channel catfish in similar tests. Sediment tests with fluoranthene resulted in 100% mortality with both fathead minnows and channel catfish.

Dans cette thèse, nous avons déterminé les mécanismes qui régissent l'efficacité des particules de fer zérovalent (ZVI) dans la dépollution des sols et des eaux souterraines. Dans les milieux contaminés par des polluants accepteurs d'électrons, le ZVI est injecté in situ sous forme de suspensions de particules micro et/ou nanométriques. La première étude a porté sur la caractérisation de poudres industrielles et de particules synthétisées au laboratoire à partir de thé vert. Afin de comparer la réactivité de l'ensemble des particules, un test en milieu fermé a été mis en oeuvre avec une solution de nitrate. Ce test a permis de différencier les particules en mettant en évidence des mécanismes réactionnels et des cinétiques de réduction qui dépendent du type de poudre utilisé. La seconde étude a porté sur la dégradation du chrome hexavalent (dans une matrice sol et eau) en combinant le ZVI à du thiosulfate de sodium. Les résultats ont été probants et ont mené au dimensionnement d'un pilote sur un site de Soléo Services. Enfin, deux cas de remédiation de sites pollués aux solvants chlorés ont été étudiés. Des expériences de laboratoire ont été menées pour expliquer l'impact des conditions opératoires sur l'efficacité du traitement / This thesis aims at a better understanding of mechanisms governing the efficiency of zerovalent iron (ZVI) particles in soil and groundwater remediation. In these processes ZVI is injected in situ as micro and/or nanoparticles slurry in areas contaminated by electron acceptor pollutants. At first, we characterized industrial powders and particles synthetized with green tea in the laboratory. In order to compare the reactivity of all the particles, a batch test has been carried out with nitrate solution. Differences in pathways and kinetic reduction have been exhibited. Secondly, we combined ZVI with sodium thiosulfate to investigate hexavalent chromium degradation (soil and water matrices). The results are conclusive and were used to design a pilot on a Soléo Services site.Finally, remediation cases of sites contaminated by chlorinated solvents have been investigated. Lab experiments have been run to explain the influence of operating conditions on the treatment efficacy

Au cours des dernières décennies, un contexte alarmant de déclin des paramètres du sperme etd’accroissement constant des pathologies génitales masculines a été décrit dans de nombreuxpays industrialisés.Notre travail évalue dans un premier temps l’évolution des paramètres spermatiques chez11 330 hommes ayant consulté pour infertilité conjugale au Centre de ProcréationMédicalement Assistée du CHU de Marseille entre 1988 et 2007. Les données ont étérecueillies de manière rétrospective et analysées par régression linéaire multi-variée afin detenir compte de l’effet lié à l’âge. Nous montrons une diminution significative des principauxparamètres du sperme: concentration en spermatozoïdes (-1.4% par an), numération totale enspermatozoïdes (-1.5% par an), mobilité progressive rapide (-5.6% par an) et morphologienormale (-1.9% par an). Les possibles biais de selection ont été discutés. L’effet del’environnement sur notre fonction de reproduction est l’une des hypothèses principalesévoquées pour expliquer ce phénomène.Nous montrons ensuite comment un modèle de culture de tubes séminifères de rat en chambrebicamérale, couplé à des techniques d’étude de la méiose en immunocytochimie peut êtreutilisé comme nouvel outil de reprotoxicologie. Nous décrivons tout d’abord avec l’anticorpsanti-SCP3 la prophase de première division méiotique chez le rat in-vivo et nous validons lemodèle de culture par comparaison entre les résultats des cellules obtenues in vivo et ceux descellules obtenues ex-vivo. Nous montrons ensuite grâce à ce système l’impact du ChromeHexavalent et du Cadmium sur la méiose du rat. Ces 2 métaux lourds, largement présent dansnotre environnement, peuvent être responsables d’atteintes importantes des cellulesméiotiques, y compris à de faibles doses pouvant correspondre à celles retrouvées chez desindividus exposés dans leur vie quotidienne et/ou professionnelle. / In recent decades, an alarming decline of sperm parameters and a constant increase in malegenital diseases has been described in many industrialized countries.In a first time, our study evaluates the evolution of sperm parameters in 11 330 menconsulting for infertility of their couple in the Reproduction Biology Laboratory of anUniversity Hospital in Marseilles between 1988 and 2007. Data were collected retrospectivelyand analyzed by multivariate linear regression to take into account the effect related to age.We show a significant decrease of the main sperm parameters: sperm concentration (-1.4%per year), total sperm count (-1.5% per year), rapid progressive motility (-5.6% per year) andnormal morphology (-1.9 % per year). Possible selection bias were discussed. The effect ofenvironment on our reproductive function is one of the main hypothesis to explain thisphenomenon.Secondly, we show how a rat seminiferous tubule culture in a bicameral chamber system,coupled with study of meiosis by immunocytochemistry can be used as a new tool ofreprotoxicology. We first describe with an anti-SCP3 antibody the first prophase of ratmeiosis and we validate the model of culture by comparing the results obtained on cellsobtained after in vivo spermatogenesis and those of cells obtained ex-vivo. Then, we showusing this system, the impact of hexavalent chromium and cadmium on rat meiosis. These twoheavy metals, widely present in our environment, may cause substantial impairment ofmeiotic cells, including low doses which can fit with those found in individuals exposed intheir personnal life and / or occupational training.

A intensificação da degradação ambiental impulsionada pelas atividades antrópicas tem comprometido a qualidade da água. A presença de metais potencialmente tóxicos no ambiente provoca diversos impactos na fauna e flora, como, por exemplo, o processo de magnificação trófica. Assim, é fundamental que estudos de adsorção desses contaminantes sejam realizados, a fim de buscar novos métodos que permitam a remoção dos mesmos no meio aquático. O metal crômio está nos efluentes de diversos processos industriais, como curtumes, refino de petróleo, galvanoplastia, soldagem e cromagem. Esse metal na forma hexavalente possuí efeito tóxico a biota e riscos à saúde humana, indicando a necessidade da realização de estudos para sua remoção de efluentes industriais e corpos d\'água. O biopolímero quitosana tem sido reportado em diversos estudos como bioadsorvente de alto potencial de retenção de metais, por conta da presença de amino-grupos em sua estrutura. Além disso, a quitosana possui propriedades singulares e é obtida da quitina, um dos biopolímeros mais abundantes na natureza. Com a finalidade de avaliar a capacidade de adsorção de Cr (VI) pelo biopolímero quitosana em forma de pérolas (P-QTS), realizou-se ensaios de adsorção em processo contínuo com diferentes concentrações do metal cromo em coluna de leito fixo, preenchida pelo material adsorvente (P-QTS). Além disso, realizou-se testes de toxicidade com os organismos Daphnia magna, Allonais inaequalis e Chironomus xanthus no afluente e efluente da coluna de adsorção, buscando avaliar a toxicidade dessas amostras para os organismos e a consequente eficácia do tratamento da solução de dicromato de potássio na coluna de leito fixo com as P-QTS. As curvas de ruptura indicaram que para as maiores concentrações de K2Cr2O7 houve intensificação da saturação da CALF (coluna de adsorção de leito fixo), e, consequentemente, a zona de transferência de massa (ZTM) se deslocou no sentido descendente do leito fixo da coluna de adsorção. A razão C/Co (concentração efluente/concentração afluente) aumentou de maneira significativa no decorrer do ensaio para as maiores concentrações afluentes (25 e 28,5 mg L-1) de K2Cr2O7 alcançando valores de até 0,4, e, isso demonstra a saturação de parte das P-QTS na coluna de leito fixo. De maneira geral, a remoção de Cr VI foi alta (superior a 50% e atingindo a máxima de 98%) para os tempos estudados na presente pesquisa, sendo maior nos menores tempos (60 e 120 min) do ensaio, estado em que os sítios ativos para adsorção das P-QTS provavelmente estavam livres. Da extração do cromo das P-QTS obteve-se valor máximo de 8,18 mg g-1 e mínimo de 0,42 mg g-1 de massa adsorvida por massa de adsorvente, o que indica variação de acordo com a concentração da solução de K2Cr2O7 afluente a CALF, ou seja, para as maiores concentrações, maior a quantidade adsorvida de Cr VI por massa de adsorvente (P-QTS). Alguns pesquisadores obtiveram relação de 2,6 mg de crômio (III) /g de quitosana indicando que as P-QTS na coluna de leito fixo possuem boa capacidade de adsorção. Os testes de toxicidade mostraram diferentes sensibilidades dos organismos-teste às soluções de dicromato de potássio, sendo na ordem decrescente: Chironomus xanthus < Allonais inaequalis < Daphnia magna. A coluna de adsorção de leito fixo diminuiu, de modo geral, a mortalidade dos organismos-teste comparando o afluente e efluente, principalmente das amostras efluentes de menor tempo (60 e 120 min) de ensaio de adsorção. A média de comprimento das larvas de C. xanthus reduziu (10,07 mm > 8,34 mm > 4,59 mm), de modo geral, a medida que o tempo de ensaio (60, 120 e 180 min) aumentou, indicando aumento da concentração de Cr VI nos efluentes. / The intensification of environmental degradation driven by anthropic activities has led to a decrease in water quality. The presence of potentially toxic metals in the environment causes several impacts on fauna and flora, such as the trophic magnification process. Thus, it is fundamental that adsorption studies of these contaminants are carried out in order to search for new methods that allow their removal in the aquatic environment. Chromium metal is in the effluents of various industrial processes, such as tanning, petroleum refining, electroplating, welding and chrome plating. The chromium in the hexavalent form has a toxic effect on biota and risks to human health, indicating the need to carry out studies to your removal of industrial effluents and water bodies. The biopolymer chitosan has been reported in several studies as bioadsorbent with high potential for metal retention, due to the presence of amino groups in its structure. In addition, chitosan has unique properties and is obtained from chitin, one of the most abundant biopolymers in nature. In order to evaluate the Cr (VI) adsorption capacity of the chitosan biopolymer in the form of beads (P-QTS), adsorption tests were carried out in continuous process with different concentrations of the chromium metal in a fixed bed column, filled by adsorbent material (P-QTS). Besides that, toxicity tests were carried out with the organisms Daphnia magna, Allonais inaequalis and Chironomus xanthus on the affluent and effluent of the adsorption column, seeking to evaluate the toxicity of these samples to the organisms and the consequent effectiveness of the treatment of potassium dichromate solution in the fixed bed column with the P-QTS. The breakthrough curves indicated that for the higher concentrations of K2Cr2O7 there was an increase in the saturation of the CALF (fixed bed adsorption column), and consequently the mass transfer zone (ZTM) moved downwards from the fixed bed of the column of adsorption. The C/Co (affluent concentration/effluent concentration) ratio increased significantly during the test for the highest affluent concentrations, reaching values of up to 0.4 for the affluent concentrations of 25 and 28.5 mg L-1 of K2Cr2O7, and this demonstrates the saturation of part of the P-QTS in the fixed bed column. The removal of Cr VI was high (higher than 50% and reaching a maximum of 98%) for the times studied in the present study, but it was higher in the lower times (60 and 120 min) of the test, in which the active sites for adsorption of P-QTS probably were free. From the extraction of chromium from P-QTS, a maximum value of 8.18 mg g-1 and a minimum of 0.42 mg g-1 was obtained, which indicates variation according to the concentration of the K2Cr2O7 solution affluent to CALF, i.e the adsorbed amount of Cr VI per adsorbent mass (P-QTS) is higher at higher concentrations. Some authors have obtained a ratio of 2.6 mg of chromium (III) / g of chitosan indicating that the P-QTS in the fixed bed column have good adsorption capacity. The toxicity tests showed different sensitivities of the test organisms to the solutions of potassium dichromate, being in descending order: Chironomus xanthus < Allonais inaequalis < Daphnia magna. The fixed-bed adsorption column decreased the mortality of the test organisms by comparing the affluent and the effluent, mainly from the effluent samples with the shortest adsorption test time (60 and 120 min). The mean length of the C. xanthus larvae decreased (10.07 mm> 8.34 mm> 4.59 mm), generally as the test time (60, 120 and 180 min) increased, indicating rise in Cr VI concentration in the effluents.

A intensificação da degradação ambiental impulsionada pelas atividades antrópicas tem comprometido a qualidade da água. A presença de metais potencialmente tóxicos no ambiente provoca diversos impactos na fauna e flora, como, por exemplo, o processo de magnificação trófica. Assim, é fundamental que estudos de adsorção desses contaminantes sejam realizados, a fim de buscar novos métodos que permitam a remoção dos mesmos no meio aquático. O metal crômio está nos efluentes de diversos processos industriais, como curtumes, refino de petróleo, galvanoplastia, soldagem e cromagem. Esse metal na forma hexavalente possuí efeito tóxico a biota e riscos à saúde humana, indicando a necessidade da realização de estudos para sua remoção de efluentes industriais e corpos d\'água. O biopolímero quitosana tem sido reportado em diversos estudos como bioadsorvente de alto potencial de retenção de metais, por conta da presença de amino-grupos em sua estrutura. Além disso, a quitosana possui propriedades singulares e é obtida da quitina, um dos biopolímeros mais abundantes na natureza. Com a finalidade de avaliar a capacidade de adsorção de Cr (VI) pelo biopolímero quitosana em forma de pérolas (P-QTS), realizou-se ensaios de adsorção em processo contínuo com diferentes concentrações do metal cromo em coluna de leito fixo, preenchida pelo material adsorvente (P-QTS). Além disso, realizou-se testes de toxicidade com os organismos Daphnia magna, Allonais inaequalis e Chironomus xanthus no afluente e efluente da coluna de adsorção, buscando avaliar a toxicidade dessas amostras para os organismos e a consequente eficácia do tratamento da solução de dicromato de potássio na coluna de leito fixo com as P-QTS. As curvas de ruptura indicaram que para as maiores concentrações de K2Cr2O7 houve intensificação da saturação da CALF (coluna de adsorção de leito fixo), e, consequentemente, a zona de transferência de massa (ZTM) se deslocou no sentido descendente do leito fixo da coluna de adsorção. A razão C/Co (concentração efluente/concentração afluente) aumentou de maneira significativa no decorrer do ensaio para as maiores concentrações afluentes (25 e 28,5 mg L-1) de K2Cr2O7 alcançando valores de até 0,4, e, isso demonstra a saturação de parte das P-QTS na coluna de leito fixo. De maneira geral, a remoção de Cr VI foi alta (superior a 50% e atingindo a máxima de 98%) para os tempos estudados na presente pesquisa, sendo maior nos menores tempos (60 e 120 min) do ensaio, estado em que os sítios ativos para adsorção das P-QTS provavelmente estavam livres. Da extração do cromo das P-QTS obteve-se valor máximo de 8,18 mg g-1 e mínimo de 0,42 mg g-1 de massa adsorvida por massa de adsorvente, o que indica variação de acordo com a concentração da solução de K2Cr2O7 afluente a CALF, ou seja, para as maiores concentrações, maior a quantidade adsorvida de Cr VI por massa de adsorvente (P-QTS). Alguns pesquisadores obtiveram relação de 2,6 mg de crômio (III) /g de quitosana indicando que as P-QTS na coluna de leito fixo possuem boa capacidade de adsorção. Os testes de toxicidade mostraram diferentes sensibilidades dos organismos-teste às soluções de dicromato de potássio, sendo na ordem decrescente: Chironomus xanthus < Allonais inaequalis < Daphnia magna. A coluna de adsorção de leito fixo diminuiu, de modo geral, a mortalidade dos organismos-teste comparando o afluente e efluente, principalmente das amostras efluentes de menor tempo (60 e 120 min) de ensaio de adsorção. A média de comprimento das larvas de C. xanthus reduziu (10,07 mm > 8,34 mm > 4,59 mm), de modo geral, a medida que o tempo de ensaio (60, 120 e 180 min) aumentou, indicando aumento da concentração de Cr VI nos efluentes. / The intensification of environmental degradation driven by anthropic activities has led to a decrease in water quality. The presence of potentially toxic metals in the environment causes several impacts on fauna and flora, such as the trophic magnification process. Thus, it is fundamental that adsorption studies of these contaminants are carried out in order to search for new methods that allow their removal in the aquatic environment. Chromium metal is in the effluents of various industrial processes, such as tanning, petroleum refining, electroplating, welding and chrome plating. The chromium in the hexavalent form has a toxic effect on biota and risks to human health, indicating the need to carry out studies to your removal of industrial effluents and water bodies. The biopolymer chitosan has been reported in several studies as bioadsorbent with high potential for metal retention, due to the presence of amino groups in its structure. In addition, chitosan has unique properties and is obtained from chitin, one of the most abundant biopolymers in nature. In order to evaluate the Cr (VI) adsorption capacity of the chitosan biopolymer in the form of beads (P-QTS), adsorption tests were carried out in continuous process with different concentrations of the chromium metal in a fixed bed column, filled by adsorbent material (P-QTS). Besides that, toxicity tests were carried out with the organisms Daphnia magna, Allonais inaequalis and Chironomus xanthus on the affluent and effluent of the adsorption column, seeking to evaluate the toxicity of these samples to the organisms and the consequent effectiveness of the treatment of potassium dichromate solution in the fixed bed column with the P-QTS. The breakthrough curves indicated that for the higher concentrations of K2Cr2O7 there was an increase in the saturation of the CALF (fixed bed adsorption column), and consequently the mass transfer zone (ZTM) moved downwards from the fixed bed of the column of adsorption. The C/Co (affluent concentration/effluent concentration) ratio increased significantly during the test for the highest affluent concentrations, reaching values of up to 0.4 for the affluent concentrations of 25 and 28.5 mg L-1 of K2Cr2O7, and this demonstrates the saturation of part of the P-QTS in the fixed bed column. The removal of Cr VI was high (higher than 50% and reaching a maximum of 98%) for the times studied in the present study, but it was higher in the lower times (60 and 120 min) of the test, in which the active sites for adsorption of P-QTS probably were free. From the extraction of chromium from P-QTS, a maximum value of 8.18 mg g-1 and a minimum of 0.42 mg g-1 was obtained, which indicates variation according to the concentration of the K2Cr2O7 solution affluent to CALF, i.e the adsorbed amount of Cr VI per adsorbent mass (P-QTS) is higher at higher concentrations. Some authors have obtained a ratio of 2.6 mg of chromium (III) / g of chitosan indicating that the P-QTS in the fixed bed column have good adsorption capacity. The toxicity tests showed different sensitivities of the test organisms to the solutions of potassium dichromate, being in descending order: Chironomus xanthus < Allonais inaequalis < Daphnia magna. The fixed-bed adsorption column decreased the mortality of the test organisms by comparing the affluent and the effluent, mainly from the effluent samples with the shortest adsorption test time (60 and 120 min). The mean length of the C. xanthus larvae decreased (10.07 mm> 8.34 mm> 4.59 mm), generally as the test time (60, 120 and 180 min) increased, indicating rise in Cr VI concentration in the effluents.

The growth of anthropogenic actions, especially industrial development and urbanization, has increased the release of heavy metals in the environment, including hexavalent chromium, Cr (VI), requiring, as a matter of urgency, new processes for pollutants removal, among which are the adsorption processes, which are the focus of this work. Biosorption is an efficient, economical, high selectivity and low energy consumption technique. The main objective of this work was the production of a biosorbent from the crop residues of Cocos nucifera, enhancing it with superparamagnetic properties, as a viable technical and economical alternative, able to adsorb hexavalent chromium ions, Cr (VI), applicable to the treatment of industrial wastewater, expanding pollution control strategies and minimizing environmental impacts. Thus, low concentration coprecipitation routes for the synthesis of nanoparticle (NPs) were proposed, conveying magnetic property to the Cocos nucifera biomass. During the biosorption of hexavalent chromium ions, Cr (VI), the saturation conditions (equilibrium) and the kinetic parameters were evaluated to determine the maximum removal capacity and equilibrium time for the biosorption, besides the optimum conditions for pH, initial concentration, biosorbent content, particle size (grain size), stirring velocity and temperature, providing the fitting of equilibrium models and kinetic constants determination. The biosorbents were characterized by scanning electron microscopy techniques with dispersive energy spectroscopy (SEM/EDS), Fourier transform infrared spectrometry (FT-IR), X-ray diffraction (EDX), X-ray fluorescence with dispersive energy (FR-X/WD), thermogravimetric analysis (TGA), magnetization measurements, zero load point analysis (pCZ), and specific surface analysis through the Brunauer, Emmet and Teller (BET) method. The leachate effluent obtained in the production of the magnetized fibers was characterized through the parameters biochemical oxygen demand (BOD), chemical oxygen demand (COD), total organic carbon (TOC) and pH. The characterization of biosorbents and the determination of kinetic and equilibrium parameters provided the main mechanisms of the biosorption process, giving arise to a possible application on an industrial scale, helping to solve serious environmental problems. / O crescimento das atividades antrópicas, sobretudo o desenvolvimento industrial e o crescimento das cidades têm como consequência o aumento do descarte de metais pesados no ambiente com destaque para o cromo hexavalente, Cr(VI), demandando, urgentemente, novos processos para remoção destes poluentes, dentre os quais os processos adsortivos, que são o foco do presente trabalho. A biossorção tem se destacado como uma técnica eficaz, econômica, de alta seletividade e baixo consumo energético. O objetivo principal desse trabalho é a produção de um biossorvente a partir de rejeitos agrícolas de fibra de Cocos nucifera com propriedades superparamagnética, capaz de adsorver íons de cromo hexavalente, Cr(VI), facilmente aplicável as indústrias, como uma alternativa técnica e econômica viável, ampliando as estratégias de controle de poluentes e minimizando os impactos ambientais. Com essa finalidade foram propostas rotas de síntese de coprecipitação de nanoparticulas (NPs) de magnetita, em baixas concentrações, promovendo propriedade magnética à biomassa das fibras do Cocos nucifera. No processo de biossorção dos íons cromo hexavalente, Cr(VI), foram avaliadas as condições de saturação (equilíbrio) e os parâmetros cinéticos para determinar a capacidade máxima de remoção e o tempo de equilíbrio da biossorção, além das condições ótimas de pH, concentração inicial e carga dos biossorventes, tamanho das partículas (granulometria), velocidade de agitação e temperatura, definindo os modelos de equilíbrio e as constantes cinéticas. Os biossorventes foram caracterizados pelas técnicas de microscopia eletrônica de varredura com espectroscopia de energia dispersiva (MEV/EDS), espectrometria de infravermelho por transformada de Fourier (FT-IR), difratometria de raios-X (EDX), fluorescência de raios-X por energia dispersiva (FR-X/WD), análise termogravimétrica (TGA), medidas de magnetização, análise do ponto de carga zero (pCZ) e análise superficial especifica pelo método de Brunauer, Emmet e Teller (B.E.T). O lixiviado, efluente obtido na produção das fibras magnetizadas, foi caracterizado pelas determinações da demanda bioquímica de oxigênio (DBO), demanda química de oxigênio (DQO), carbono orgânico total (COT) e pH. Como resultado da caracterização dos biossorventes e dos cálculos dos parâmetros cinéticos e de equilíbrio, foi possível sugerir os principais mecanismos do processo de biossorção, facilitando uma possível aplicação em escala industrial, remediando sérios problemas ambientais.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / In Brazil, the SMP buffer has been used since the 60's as the main method to estimate the potential acidity and/or the soil lime requirement. However, SMP contains pnitrophenol and potassium chromate, substances with high potential for environmental contamination and able to promote the development of methemoglobin and carcinomas in lab handlers as a result of continued exposure. This work aimed to develop a buffer solution free of hazardous substances which can mimic the acid-base characteristics of the SMP buffer, with the composition used in the states of RS and SC (SMP-RS/SC), in response to the acidity of Brazilian soils. To develop the new buffer, imidazole and 2-(Nmorpholino) ethanessulfonic acid monohydrate (MES) were used as substitutes for pnitrophenol and potassium chromate, respectively. The titration of the buffer SMP-RS/SC with HCl was carried out and these data were used as the starting point for the new buffer reproduce the potentiometric behavior of SMP-RS/SC buffer. To achieve this, multiparametric regression analysis was used, taking as adjustable parameters the pKa values and the concentrations of the components of the new buffer. The final composition for the new buffer, called Santa Maria buffer (TSM) was obtained with: 37.5 mM of triethanolamine; 17.3 mM of imidazole; 30.7 mM of MES; 20.7 mM of calcium acetate and 721 mM of calcium chloride; with initial pH adjusted to 7.5. For comparison between TSM and SMP-RS/SC, we utilized 42 soil samples collected in different physiographic regions of Brazil. Linear regression was performed with pH-SMP and pHTSM values, and also, between the lime requirement by SMP and TSM, reaching determination coefficient (R2) greater than 0.99 in both cases. The TSM had equivalent sensitivity to the SMP-RS/SC in differentiating the acidity degree of soils, and can be used replacing this, without the need for change in routine laboratory and interpretations already developed to estimate the potential acidity or need limestone of soil. At temperature from 22 to 27 °C, the TSM has a long shelf life and can be stored in plasticpolypropylene or glass containers protected from light, for a period of 120 to 150 days. The replacement of SMP-RS/SC buffer by TSM is a viable alternative for soil testing laboratories to avoid the generation of hazardous wastes and to reducing the health risks for the lab handlers. / No Brasil, o tampão SMP vem sendo utilizado desde a década de 60 como o principal método para a estimativa da acidez potencial e/ou da necessidade de calcário do solo. No entanto, em sua composição, a solução SMP apresenta p-nitrofenol e cromato de potássio, substâncias essas com elevado potencial de contaminação ambiental e capazes de promover o desenvolvimento de metahemoglobina e carcinomas aos seus manipuladores, como conseqüência da exposição continuada. Este trabalho teve como objetivo principal desenvolver uma solução tampão livre de substâncias tóxicas, capaz de mimetizar as características ácido-base do tampão SMP, na composição utilizada nos estados do RS e SC (SMP-RS/SC), em resposta à acidez de solos brasileiros. Para o desenvolvimento do novo tampão, utilizaram-se como substitutos ao p-nitrofenol e ao cromato de potássio, o imidazol e o ácido 2-(N-morfolino) etanossulfônico monohidratado (MES), respectivamente. Realizou-se a titulação do tampão SMP-RS/SC com HCl e esses dados de titulação foram utilizados como ponto de partida para que o novo tampão reproduzisse o comportamento potenciométrico do tampão SMP-RS/SC. Para tanto, empregou-se análise de regressão multiparamétrica, considerando como variáveis os valores de pKa e as concentrações dos componentes do novo tampão. A composição final para o novo tampão, denominado Tampão Santa Maria (TSM), foi obtida com: 37,5 mM de trietanolamina; 17,3 mM de imidazol; 30,7 mM de MES; 20,7 mM de acetato de cálcio e 721 mM de cloreto de cálcio; com pH inicial ajustado a 7,5. Para comparação entre o TSM e o SMP-RS/SC, utilizaram-se 42 amostras de solo oriundas de diferentes regiões fisiográficas do Brasil. Ajustou-se regressão linear entre os valores de pH-TSM e pH-SMP, e também, entre a recomendação de calcário por TSM e por SMP, alcançando-se coeficiente de determinação (R2) superior a 0,99 em ambos os casos. O TSM apresentou sensibilidade equivalente ao SMP-RS/SC na diferenciação do grau de acidez dos solos estudados, podendo ser utilizado em substituição a esse, sem a necessidade de alteração da rotina e das interpretações laboratoriais já desenvolvidas para a estimativa da acidez potencial ou necessidade de calcário do solo. À temperatura de 22 a 27 ºC, o TSM apresenta uma longa vida útil, podendo ser armazenado em recipiente de plástico-polipropileno ou vidro protegido da luz, por um período de 120 a 150 dias. A substituição do tampão SMP-RS/SC pelo TSM é uma alternativa viável para os laboratórios de análise de solo evitarem a geração de resíduos perigosos e reduzirem os riscos à saúde dos técnicos manipuladores.