This work addresses the synthesis of carbon nanomaterials (CNMs) by up-cycling common solid wastes. These feedstocks could supersede the use of costly and often toxic or highly flammable chemicals, such as hydrocarbon gases, carbon monoxide, and hydrogen, which are commonly used as feedstocks in current nanomanufacturing processes for CNMs. Agricultural sugar cane bagasse and corn residues, scrap tire chips, and postconsumer polyethylene (PE) and polyethylene terephthalate (PET) bottle shreddings were either thermally treated by sole pyrolysis or by sequential pyrolysis and partial oxidation. The resulting gaseous carbon-bearing effluents were then channeled into a heated reactor. CNMs, including carbon nanotubes, were catalytically synthesized therein on stainless steel meshes. This work revealed that the structure of the resulting CNMs is determined by the feedstock type, through the disparate mixtures of carbon-bearing gases generated when different feedstocks are pyrolyzed. CNM characterization was conducted by scanning and transmission electron microscopy as well as by Raman spectroscopy and by thermogravimetric analysis. Gas chromatography was used to characterize the gases in the synthesis chamber. This work demonstrated an alternative method for efficient manufacturing of CNMs using both biodegradable and nonbiodegradable agricultural and municipal carbonaceous wastes.

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Acidic mine drainage (AMD) is regarded as a pollutant and considered as potential source of valuable metals. With diminishing metal resources and ever-increasing demand on industry, recovering AMD metals is a sustainable initiative, despite facing major challenges. AMD refers to effluents draining from abandoned mines and mine wastes usually highly acidic that contain a variety of dissolved metals (Fe, Mn, Cu, Ni, and Zn) in much greater concentration than what is found in natural water bodies. There are numerous remediation treatments including chemical (lime treatment) or biological methods (aerobic wetlands and compost bioreactors) used for metal precipitation and removal from AMD. However, controlled biomineralization and selective recovering of metals using sulfidogenic bacteria are advantageous, reducing costs and environmental risks of sludge disposal. The increased understanding of the microbiology of acid-tolerant sulfidogenic bacteria will lead to the development of novel approaches to AMD treatment. We present and discuss several important recent approaches using low sulfidogenic bioreactors to both remediate and selectively recover metal sulfides from AMD. This work also highlights the efficiency and drawbacks of these types of treatments for metal recovery and points to future research for enhancing the use of novel acidophilic and acid-tolerant sulfidogenic microorganisms in AMD treatment.

ResumoO presente trabalho tem como objetivo a caracterização dos resíduos provenientes do beneficiamento de mármore e granito, visando o seu reaproveitamento como matérias primas parciais na produção de materiais vítreos. Amostras recolhidas na forma de lama foram secas e, posteriormente, caracterizadas por meio de técnicas microestruturais e de análise química por fluorescência de raios X. Dos resultados obtidos é realizada uma comparação entre os resíduos, com a finalidade de avaliar a melhor composição para a obtenção de materiais vítreos. Os resultados indicam que os resíduos do corte de mármore e de granito podem vir a ser empregados na produção da lã mineral, um material vítreo com grande mercado consumidor. Palavras-chave: Resíduos; Granitos; Mármores; Vidros. STUDY OF WASTES FROM ORNAMENTAL ROCKS FOR PRODUCTION OF VITREOUS MATERIALS AbstractThis study aims to characterize the wastes from processing of marble and granite, aiming its reuse as partial raw-materials in the production of vitreous materials. Samples collected in the mud appearance were dried and characterized using microstructural techniques and chemical analysis by X-ray fluorescence. Through the results it is elaborated a comparison among the wastes and tried to evaluate the best composition to obtain vitreous materials. The results indicate that the wastes from processing of marble and granite can be used in the production of mineral wool, a vitreo material with large consumer market. Key words: Wastes; Granites; Marbles; Glass. INTRODUÇÃOA introdução de resíduos no ciclo produtivo para a produção de um novo produto apresenta-se como uma maneira de diminuir o impacto causado pelos resíduos, quando jogados no ambiente e, também, prolongar o uso das reservas de matérias primas naturais. Ao longo de sua existência, o homem sempre utilizou os recursos naturais do planeta e, ao transformar matérias primas de modo a torná-las úteis para a sociedade, produz quantidades apreciáveis de resíduos que acabam por comprometer o meio ambiente.(1) Neste contexto, este trabalho visa obter bases sobre o conhecimento para reutilização de dois rejeitos industriais como matérias primas para serem reintroduzidas no meio produtivo, de forma a diminuir o impacto causado quando estes resíduos são lançados no meio ambiente, e também diminuindo a extração de matéria prima natural. O aproveitamento de rejeitos, total ou parcial, constitui uma vantagem que coloca o fabricante em uma posição fortemente competitiva no mercado, devido não apenas à questão econômica, como também à oportunidade de veiculação deste princípio como marketing ecológico.