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The objective of this study is to develop a low-cost biosorbent using residual seeds of the Citrullus lanatus fruit for the removal of cationic dyes. Physicochemical parameters such as pH, adsorbent mass, contact time, and temperature were evaluated for their effects on dye removal. The biosorbent is composed of lignin and cellulose, exhibiting a highly heterogeneous surface with randomly distributed cavities and bulges. The adsorption of both dyes was most effective at natural pH with a dosage of 0.8 g L−1. Equilibrium was reached within 120 min, regardless of concentration, indicating rapid kinetics. The Elovich model and pseudo-second-order kinetics were observed for crystal violet and basic fuchsin dye, respectively. The Langmuir model fitted well with the equilibrium data of both dyes. However, the increased temperature had a negative impact on dye adsorption. The biosorbent also demonstrated satisfactory performance (R = 43%) against a synthetic mixture of dyes and inorganic salts, with a small mass transfer zone. The adsorption capacities for crystal violet and basic fuchsin dye were 48.13 mg g−1 and 44.26 mg g−1, respectively. Thermodynamic studies confirmed an exothermic nature of adsorption. Overall, this low-cost biosorbent showed potential for the removal of dyes from aqueous solutions. In this work, a novel biosorbent was developed using residual Citrullus lanatus fruit seeds that can efficiently remove cationic dyes from aqueous solutions. The biosorbent’s composition includes lignin and cellulose, and its surface structure is highly heterogeneous, consisting of randomly distributed cavities and bulges. The biosorbent demonstrated a rapid and efficient adsorption capacity for both crystal violet and basic fuchsin, regardless of dye concentration. Moreover, the biosorbent was successfully employed in the treatment of a synthetic mixture containing several dyes and inorganic salts. Finally, the application of the biosorbent in continuous adsorption showed a low zone of mass transfer and high breakthrough time, indicating it to be an excellent material for fixed-bed operation. Overall, this study provides a low-cost and efficient alternative for the removal of dyes from aqueous solutions, with promising practical applications. Citrullus lanatus seed powder was produced and characterized. Crystal Violet (CV) and Basic Fuchsin (BF) contaminants were successfully removed by the powder. Low mass-transfer zone length and good adsorption capacities were obtained in a continuous system. A good performance was observed against a synthetic mixture.

RESUMO Neste trabalho, compósito Fe2O3/grafite foi preparado e usado como um catalisador em reação foto-Fenton para a descoloração de solução aquosa contendo o corante amaranto sob irradiação de luz visível. Amostras com diferentes teores de Fe2O3 suportados sobre grafite foram preparadas e caracterizadas por difração de raios-X (DRX), adsorção-dessorção de N2 e microscopia eletrônica de varredura (MEV). O aumento do teor de ferro nos compósitos resultou em uma superior área de superfície específica. Através da metodologia de superfície de respostas gerada a partir do Delineamento Composto Central Rotacional (DCCR), verificou-se uma eficiência máxima de descoloração da solução de corante de 93% nas condições experimentais ótimas de reação foto-Fenton (pH = 2,5, quantidade de catalisador = 0,35 g L-1 e razão molar H2O2/Ʃ elementos mineralizáveis: 4,7). Portanto, o compósito Fe2O3/grafite pode ser utilizado como um potencial catalisador foto-Fenton para a degradação do corante amaranto em efluentes líquidos. ABSTRACT In this work, Fe2O3/graphite composite was prepared and used as a catalyst in photo-Fenton reaction for the decolorization of amaranth dye from aqueous solution under visible light irradiation. Samples with different Fe2O3 contents supported on graphite were prepared and characterized by X-ray diffraction (XRD), N2 adsorption-desorption and scanning electron microscopy (SEM). The increase of the iron content in the composites resulted in a superior specific surface area. The response surface methodology generated from the Rotational Central Composite Design (RCCD) showed a maximum efficiency in the decolorization of the dye solution of 93% under the optimal experimental conditions of photo-Fenton reaction (pH = 2.5, amount of catalyst = 0.35 g L-1 and molar ratio H2O2/Ʃ mineralizable compounds: 4.7). Therefore, the Fe2O3/graphite composite can be used as a potential photo-Fenton catalyst for the degradation of amaranth dye from liquid effluents.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES Industrial activities are the main causal agents in the contamination of waste water by dyes, due to the large amount of organic pollutants released in the effluents. In this scenario, adsorption has been pointed out as a promising technique in dye removal. Associating this process with the use of low cost adsorbents, such as waste from agroindustries and other alternative materials, we have an inexpensive, efficient and easily executed technique. In this sense, the peels of Pecan nut (Carya illinoensis), Chestnut (Parakeet) (Bertholletia excelsa) and Avocado (Persea americana) generate a high amount of residues when used in the manufacture of various products. Thus, this work had as objective, to develop adsorbent materials from residues of vegetal origin for the removal of industrial dyes. Pecan, Parana nut and Abacate hulls were used as biosorbents for the removal of methylene blue, crystal violet and reactive red (RR141) dyes as a model contaminant system. Both materials were characterized by the DRX, MEV and FT-IR techniques, after which pH, adsorbent mass, kinetic, equilibrium, thermodynamic studies were carried out and the adsorption capacity of the material was tested by simulation of a textile effluent. The adsorbent formed from Nóz pecã bark obtained better adsorption capacity at pH 2, from 45 mg g-1 for crystal violet and 8.5 mg g-1 for methylene blue. The pseudo-first order model was adequate to represent the kinetic data, and the equilibrium was best represented by the Sips model. Actual effluent tests revealed a 65% removal percentage of the dyes. For the nut shell the best adsorption capacity for both dyes was better in acid pH, the pseudo-first order model represented satisfactorily the kinetic curves, whereas Freundlich's model represented the best equilibrium curves. Maximum biosorption capacities were 83.6 and 83.8 mg g-1 for Violta crystal and Methylene blue, respectively. In the simulation of the textile effluent the nut shell removed 90% of the color. Finally, the bark of the avocado treated with H2SO4 and HNO3, obtained better adsorption capacities at pH 6.5, where more than 90% of Red procion was removed from the solution. The general order model was the one that best represented the adsorption kinetics, since the Sips model was adequate to represent the isotherm data, with the maximum adsorption capacities of 167.0 and 212.6 mg g-1 for the material treated with H2SO4 and HNO3, respectively. The adsorption processes were thermodynamically spontaneous, favorable and exothermic. In the simulation of the textile effluent the removal was 82 and 75%, for the adsorvent treated with H2SO4 and HNO3, respectively. It is concluded that these materials possess a great potential in the removal of dyes. As atividades industriais são as principais agentes causadoras na contaminação de águas residuais por corantes, devido à grande quantidade de poluentes orgânicos liberados nos efluentes. Neste cenário, a adsorção tem sido apontada como uma técnica promissora na remoção de corantes. Associando este processo ao uso de adsorventes de baixo custo, como os resíduos das agroindústrias e outros materiais alternativos, tem-se uma técnica barata, eficiente e de fácil execução. Neste sentido, as cascas de Noz Pecã (Carya illinoensis), Castanha do Pará (Bertholletia excelsa) e Abacate (Persea americana) geram uma elevada quantidade de resíduos, quando empregadas na fabricação de diversos produtos. Assim, este trabalho teve como objetivo, desenvolver materiais adsorventes a partir de resíduos de origem vegetal para a remoção de corantes industriais. Foram utilizadas as cascas de Noz Pecã, Castanha do Pará e Abacate como biossorventes, visando à remoção dos corantes Azul de metileno, Violeta cristal e Vermelho reativo (RR141) como sistema modelo de contaminante. Ambos os matérias foram caracterizados pelas técnicas de DRX, MEV e FT-IR, após isso foram realizados testes de pH, massa do adsorvente, estudos cinéticos, de equilíbrio, termodinâmicos e testada a capacidade de adsorção do material mediante a simulação de um efluente têxtil. O adsorvente formado a partir da casca de Nóz pecã obteve melhores capacidades de adsorção em pH 2, sendo de 45 mg g-1 para o violeta cristal e 8,5 mg g-1 para o azul de metileno. O modelo de pseudo-primeira ordem foi o adequado para representar os dados cinéticos, já o equilíbrio foi melhor representado pelo modelo Sips. Os testes em efluente real revelaram um percentual de remoção de 65% dos corantes. Para a casca da castanha a melhor capacidade de adsorção para ambos os corantes foi melhor em pH ácido, o modelo pseudo-primeira ordem representou satisfatoriamente as curvas cinéticas, já o modelo de Freundlich foi o que melhor representou as curvas de equilíbrio. As capacidades máximas de biosorção foram 83,6 e 83,8 mg g-1 para Violta cristal e Azul de metileno, respectivamente. Na simulação do efluetne textil a casca da castanha removeu 90 % da cor. Por fim a casca do abacate tratada com H2SO4 e HNO3, obteve melhores capacidades de adsorção no pH 6,5, onde mais de 90 % do Vermelho procion foi removido da solução. O modelo de ordem geral foi o que melhor representou a cinética de adsorção, já o modelo de Sips foi adequado para representar os dados de isoterma, sendo as capacidades máximas de adsorção de 167,0 e 212,6 mg g-1 para o material tratado com H2SO4 e HNO3, respectivamente. Os processos de adsorção foram termodinamicamente espontâneos, favoráveis e exotérmicos. Na simulação do efluente textil a remoção foi de 82 e 75%, para o adsorventente tratado com H2SO4 e HNO3, respectivamente. Conclui-se que estes materiais possuim um grande potencial na remoção de corantes.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior The contamination of water bodies by dye containing effluents is harmful for the environment and human health. In this way, several techniques have been used to remove dyes from colored effluents. Adsorption stands out, due its low-cost, low energy requirements, use of low-cost adsorbents, ease of implementation and operation and high efficiency. In this work, peanut shells were used as adsorbents and as precursors to obtain activated carbon. These materials were characterized and used to remove DB38 (Direct Black 38) and RR141 (Reactive Red 141) dyes from aqueous media. It was found that the best adsorbents to remove both dyes were in the following order: microwave/pyrolyzed activated carbon from peanut shells>pyrolyzed activated carbon from peanut shells>peanut shells. This result demonstrated that the microwave irradiation followed by pyrolysis is an alternative way to produce a material with good adsorbent characteristics. The adsorption was favored at pH of 2.5. For both dyes, the kinetic was successfully represented by the pseudo second order model and the equilibrium, represented by the Langmuir model. Desorption and reuse was possible maintaining the same adsorption capacity. In brief, these results revealed that peanut shells are a good precursor to obtain a suitable adsorbent material able to remove dyes from aqueous media. A atividade industrial tem contribuído muito para um aumento significativo nas concentrações de corantes em águas, representando uma importante fonte de contaminação dos corpos aquáticos, principalmente quando consideramos que tais íons podem ser disseminados via cadeia alimentar. Devido a estas implicações ambientais, novos processos de remoção e/ou degradação destes compostos em efluentes têxteis têm sido testados, dentre eles a adsorção. O processo de adsorção é uma alternativa potencialmente versátil, acessível e econômica para o tratamento de diversos tipos de efluentes, inclusive os das indústrias têxteis. Objetivou-se neste trabalho desenvolver materiais adsorventes a partir de resíduos agroindustriais para a remoção de poluentes em meio aquoso. Neste estudo foram utilizadas cascas de amendoim como adsorvente e como precursor para a obtenção de carvões, para remoção de poluentes hídricos utilizando soluções de corantes DB38 (Direct Black 38) e RR141(Reactive Red 141) como sistema modelo de contaminante. A partir do estudo adsortivo, verificou-se que o material submetido à irradiação de microondas seguido de pirólise (MW-P), obteve maior capacidade de adsorção de ambos os corantes, principalmente a um pH ácido de 2,5, do que o submetido à pirólise convencional (P). A adsorção dos corantes DB38 e RR141 pela amostra MW-P pode ser representado pelo modelo cinético de pseudo-segunda ordem e o modelo de isoterma de Sips. O adsorvente é possível ser reutilizado mantendo a mesma capacidade de adsorção. Com isso, pode-se concluir que a casa de amendoim pode originar um bom material adsortivo na remoção de corantes a partir de soluções aquosas.