Gutterres Mariliz

Universidade Federal do Rio Grande do Sul | UFRGS

4.1 Objetivo Geral O presente projeto tem com objetivo o desenvolvimento de um novo material adsorvente para o tratamento de efluentes líquidos contendo corante e/ou metais, sendo este obtido a partir do encapsulamento de queratina hidrolisada, biomassa residual do processo de fermentação da cerveja e quitosana via processos Sol-Gel ou recobrimento de carvão ativado. 4.2 Objetivos específicos Os objetivos específicos do presente trabalho são: a) Obter um novo adsorvente a partir da técnica Sol-Gel e recobrimento de carvão ativado com os biossorventes; b) Comparar os biossorventes produzidos frente a adsorção de Cromo (IV), corante alimentício amarelo tartrazina e o corante têxtil azul de metileno, em diferentes condições de pH c) Construir as curvas de equilíbrio do(s) biossorventes(s) selecionado(s) na etapa anterior, em diferentes condições experimentais, para os poluentes selecionados; d) Correlacionar as curvas de equilíbrio com modelos de isotermas previstos na literatura; e) Obter parâmetros cinéticos do processo de adsorção; f) Obter as curvas de rupturas dos poluentes acima citados, e correlacionar com modelos previstos na literatura; g) Realizar ensaios cíclicos de adsorção e regeneração do(s) biossorventes(s) desenvolvido(s); h) Inserir alunos de graduação na pesquisa científica; i) Gerar ao menos dois artigos científicos para revistas reconhecidas na área de ciência para difusão do conhecimento.

Dyes, phenols, amines and other organic compounds are largely employed in the industry such as textiles, paper, polymers, pesticides, pharmaceuticals, explosives, oil additives, rubber, steel, etc and then these compounds are released in high amounts in the aqueous effluents. These effluents contaminated with these organic compounds require special treatment, because the presence of these chemicals in water reduce the light penetration, impairing the photosynthesis of aqueous flora; also the presence of these compounds in water cause an improper visual and organoleptic impact for its use; also these chemicals increase the chemical oxygen demand of the aquatic environment, decreasing remarkably the life of aquatic beings. Besides that, the organic chemicals such as dyes, phenols, amines can cause allergy, gastrointestinal disorders, difficulty for walking, cardiovascular diseases, skin irritation, human cancer, besides of these chemicals being mutagenic. In this way, effluents containing organic chemicals, when they are not conveniently treated they are capable of endangering the aquatic system. For this reason, the treatment of industrial effluents containing organic compounds is a major concern from a toxicological and environmental point of view. With the growing Brazilian agricultural production generates a large number of agricultural residues, which in most cases are simply discarded in groundwater environments (rivers, lakes, streams, etc.) as well as in soils. The decomposition of these organic residues leads to the generation of various chemical compounds and microorganisms that may contaminate the environment in an uncontrolled manner. Thus, it is necessary to find a use for these agricultural wastes to generate new wealth to the country and avoid environmental order problems. Combining the need to find a use for agro-industrial residues and also to treat wastewater containing organic compounds, in this project, it is proposed to use agro-industrial residues in pristine and chemically modified form (carbonization, activated carbon production, producing composites with polysiloxanes or clays). Also, synthetic adsorbents (carbon nanotubes, graphene, functionalized organo-silicates and silicas) for the removal of organic compounds from aqueous effluents will be employed. The dead biomass when used as adsorbent is named biosorbent, since it is of natural origin differing from those of synthetic origin. The plant biomass has a chemical composition composed of lignin-cellulose, with the following functional groups: alcohols, ethers, phenols, aromatic rings, carboxylic groups, esters when suspended in solutions with a suitable pH, may adsorb the organic compounds by electrostatic interaction, hydrophobic interaction such as van der Waals forces, hydrogen bonds, - interactions. The main advantages of biosorbents in relation to the synthetic adsorbents: they are naturally occurring adsorbents which are plentiful and also they are agricultural residues or waste of organic material in a state of decay, showing no commercial value. However, these biosorbents have low surface area, low pore volume, low adsorption capacity for many pollutants and low mechanical resistance to high pressures, fact that precludes its use in the form of columns due to its low mechanical strength. Therefore, it is necessary to do some chemical modification in the biomass to increase its adsorption capacity and also its mechanical strength. In this project, it will be made studies for optimization of the best adsorption batch conditions. It will be studied, adsorbent dose; adsorbent particle size; acidity of the adsorbate solution; contact time between the adsorbent and adsorbate; temperature of adsorption (298-323K), employing dyes, phenols and amines as adsorbates and using different adsorbents. Using the best adsorption conditions, kinetics studies will be conducted. The adsorption kinetics curves will be adjusted employing nonlinear adsorption kinetics models (pseudo-first order, pseudo-second order, general-order, fractional-order, and intra-particle diffusion) in order to study the mechanism adsorption. And further, the adsorption isotherms will be obtained to evaluate the adsorbents with a greater capacity for adsorption of adsorbates of interest. The equilibrium data of adsorption will be fitted to Langmuir, Freundlich, Liu, Sips, Redlich-Peterson adsorption equilibrium models. The adsorption equilibrium isotherms will be obtained at different temperatures to obtain the parameters G (changes in the Gibb's adsorption free energy from 298 to 323K), H° (changes in the standard enthalpy of adsorption at 298K), and S° (changes in standard adsorption entropy at 298K). In order to measure the amounts of adsorbates (organic compounds) remaining in solution after the adsorption procedure, the following analytical techniques will be used: UV-VIS (molecular absorption spectrophotometry in the ultraviolet-visible region), HPLC (high performance liquid chromatography), and MF (molecular fluorescence). After evaluating the performance of adsorbent, these materials will be employed for removing organic compounds from wastewater of textile industries, food, paper, petrochemical, pharmaceutical, polymers, etc.