Perspectivas de aplicações tecnológicas de lodo gerado no processo de tratamento de água dos rios Negro e Solimões

Este trabalho teve como objetivo caracterizar um subproduto do processo de tratamento de água, visandoinseri-lo na cadeia produtiva da construção civil. Tal subproduto foi gerado em uma estação de tratamento deágua (ETA), que realiza a captação de água bruta do Rio Negro e, eventualmente, do Rio Solimões. Paraadequar a água desses mananciais aos padrões de potabilidade brasileiros, executa-se na ETA uma série deprocessos físico-químicos, os quais acarretam a geração do resíduo designado lodo de ETA. Visandoidentificar possíveis aplicações tecnológicas para o referido resíduo, fez-se uma pesquisa bibliográficapertinente. Desse modo, constatou-se que esse tipo de subproduto necessita de beneficiamento prévio àutilização. Sendo assim, para tornar o lodo de ETA estudado uma matéria-prima apropriada, submeteu-se omesmo a procedimentos de secagem, moagem e calcinação. Antes e após tais procedimentos, suascaracterísticas foram determinadas por meio de Fluorescência de Raios X (FRX), Difração de Raios X(DRX), Termogravimetria (TG), dentre outras técnicas. Os resultados das caracterizações evidenciaram quemais de 80% da composição do lodo de ETA calcinado corresponde a óxidos de silício e alumínio. Acreditaseque, após o beneficiamento, o lodo tornou-se uma matéria-prima econômica e ambientalmente sustentável,podendo ser utilizado como substituto parcial de argilas, na produção de materiais cerâmicos; substitutoparcial de cimento Portland, em pastas, argamassas e concretos; aditivo mineral ou pozolana artificial;precursor ou agregado geopolimérico.Palavras-chave: lodo de ETA, resíduo, construção civil, Rio Negro, Rio Solimões

Synthesis of water treatment sludge ash-based geopolymers in an Amazonian context

Water treatment plants (WTP) in the City of Manaus, Brazil, generate tons of sludge daily, which are then disposed of in landfills and main watercourses, particularly two important Amazonian Rivers: the blackwater Negro River and the pale sandy-colored water Solimoes River. Because WTP-based sludges are rich in silicon and aluminum, they have been employed in the synthesis of geopolymers - alkaline activated inorganic polymers consisting of silicate and aluminosilicate chains. This paper reports the results of a geopolymeric synthesis process in which calcined sludge was explored as a source of silica and alumina. In this research, a laboratory testing program was developed to characterize the waste material generated from a water treatment plant in Manaus, whose intake water is influenced by the above referred rivers. Sample preparation involved kiln drying at 110 degrees C for 8 h, grinding in ball mill for 2 h, and calcination at 750 degrees C for 6 h. The calcined sludge was used as precursor, and potassium hydroxide added as activating alkali. Two geopolymers, one from each sludge source, were prepared following identical procedures. The chemical, compositional, morphological, thermal and mechanical properties of the fresh and hardened geopolymers were characterized. The geopolymers reached uniaxial compressive strengths of over 50 MPa at 28 days. Calcination conveyed more refined properties to the sludge-based geopolymers, akin to metakaolin-based geopolymers. The results presented herein support the technical feasibility of geopolymer synthesis in the lab scale

Biotechnological Applications of Nanoencapsulated Essential Oils: A Review

Essential oils (EOs) are complex mixtures of volatile and semi-volatile organic compounds that originate from different plant tissues, including flowers, buds, leaves and bark. According to their chemical composition, EOs have a characteristic aroma and present a wide spectrum of applications, namely in the food, agricultural, environmental, cosmetic and pharmaceutical sectors. These applications are mainly due to their biological properties. However, EOs are unstable and easily degradable if not protected from external factors such as oxidation, heat and light. Therefore, there is growing interest in the encapsulation of EOs, since polymeric nanocarriers serve as a barrier between the oil and the environment. In this context, nanoencapsulation seems to be an interesting approach as it not only prevents the exposure and degradation of EOs and their bioactive constituents by creating a physical barrier, but it also facilitates their controlled release, thus resulting in greater bioavailability and efficiency. In this review, we focused on selecting recent articles whose objective concerned the nanoencapsulation of essential oils from different plant species and highlighted their chemical constituents and their potential biotechnological applications. We also present the fundamentals of the most commonly used encapsulation methods, and the biopolymer carriers that are suitable for encapsulating EOs

Pineapple (Ananás comosus) leaves ash as a solid base catalyst for biodiesel synthesis

Homogeneous catalysts used for biodiesel synthesis have several limitations, including non-recoverability/reusability, saponification, emulsification, equipment corrosion, and environmental pollution. To overcome these limitations, we synthesized a novel catalyst via calcination of pineapple leaves waste. This catalyst was characterized by X-ray powder diffraction, X-ray fluorescence, Fourier transform infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy, and soluble alkalinity measurements. The catalyst\u27s activity with regards to soybean oil transesterification was analyzed, and multiple process parameters (temperature, catalyst amount, reaction time, and methanol:oil molar ratio) were examined. A high catalytic activity, probably related to the 85 wt% content of alkali/alkali metals (K, Ca and Mg), was observed after a 30 min reaction time, 60 °C, 4 wt% of catalyst, oil to methanol molar ratio of 1:40, reaching an oil to biodiesel conversion above 98%. We conclude that the novel catalyst presented here is efficient, cost-effective, and sustainable, while simultaneously abundant waste is reduced. © 2020 Elsevier Lt