L'objectif de la présente thèse a été d'étudier les possibilités de valorisation des déchets de biomasse (Penicillium oxalicum var. Armeniaca, Tolypocladium sp.) issus de procédés de fermentation en tant que biosorbants du plomb, du cadmium, du mercure et du chrome hexavalent. Alors que la biomasse de Tolypocladium (biomasse T) a été utilisée en l'état, la biomasse de Penicillium a dû subir un traitement alcalin (biomasse P3). Dans un premier temps, la biosorption a été étudiée à partir de solutions synthétiques monométalliques. Le pH initial optimal pour les espèces cationiques est proche du pH neutre, alors que celui de l'espèce anionique est inférieur à 3 (milieu acide). Le biosorbant P3 a montré des capacités de fixation plus importantes pour tous les métaux étudiés par rapport au biosorbant T. Les capacités maximales de fixation peuvent atteindre, dans des conditions opératoires optimales, 270 mg Hg g-1 biomasse P3 (à pH 5), 160 mg Hg g-1 biomasse T (à pH 7), 70 mg Cr(VI) g-1 biomasse P3 (à pH 3) et 55 mg Cr(VI) g-1 biomasse T (à pH 2). Ces valeurs figurent parmi les valeurs les plus élevées citées dans la littérature. Au contraire pour le plomb et le cadmium les performances sont décevantes. La cinétique de biosorption du mercure et du chrome est du second ordre. L'influence des phénomènes de diffusion sur la vitesse globale du procédé a été largement discutée. Pour les espèces cationiques, le mécanisme de chélation des métaux sur les groupes aminés a été proposé pour la biomasse P3, alors que l'échange d'ions sur les groupes carboxyliques s'est révélé plus probable pour la biomasse T. Pour ce qui concerne les espèces anioniques (ions chromates) la fixation procède par attraction electrostatique sur les groupes aminés protonés. Concernant la biomasse T, le mécanisme combiné d'adsorption/réduction observé pendant les expérimentations en régime statique n'a pas été clarifié. La biosorption à partir de solutions mixtes a été également étudiée. La sélectivité de la biomasse P3 pour le mercure a été confirmée. Aucun mécanisme de compétition n'a été identifié. Le travail expérimental s'est conclu par des expérimentations en régime dynamique (colonne à lit fixé) en utilisant la biomasse de Tolypocladium, immobilisée sur une terre des diatomées. Le procédé est contrôlé par diffusion intraparticulaire. Les courbes de percée dépendent de plusieurs paramètres tels que la concentration initiale et le diamètre des particules.

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

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.

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.