Optimizing the selective precipitation of iron to produce yellow pigment from acid mine drainage

Acid mine drainage (AMD) in the coal mining industry is recognized as one of the major sources of environmental damage. The active treatment of AMD involves adding alkaline reagents to wastewater so as to raise pH and to precipitate dissolved metals in the form of oxides/hydroxides. Studies have shown that yellow pigment (goethite) can be produced from the iron present in AMD. However, the presence of other metals can prevent the formation of pigment. Therefore, this paper seeks to evaluate several processes for purifying iron sludge so as to obtain raw material that can be recovered from AMD and thereby obtain a good quality of yellow pigment. The experiments were carried out by causing precipitation with strong and weak bases and removing other metals from the sludge by washing and filtering the sludge or by centrifugation. The results show that the color, type and morphology of the compounds changed, depending on the number of contaminants, and that these factors are strongly dependent on the type of reagent and less dependent on the separation process and the repetition of washes.Peer ReviewedPostprint (author's final draft

Obtenção de bloco de concreto celular como tema gerador para ensino médio

O Bloco de Concreto Celular (BCC) vem sendo muito utilizado na construção civil como bloco de vedação por apresentar ótimo isolamento termoacústico, além de serem considerados ambientalmente menos impactantes.  Esse tipo de concreto leve pode ser obtido pela formação das bolhas dentro de sua pasta, esta formação se dá por uma reação química ou por adição de espuma através de um agente espumígeno. Este trabalho teve por objetivo avaliar os Blocos de Concreto Celulares Espumígenos (BCCE) obtidos pela introdução de bolhas de ar em sua massa devido a um agente espumante. O principal objetivo da pesquisa realizada é aprimorar os conhecimentos adquiridos pelos alunos do Ensino Médio, integrantes do projeto, através do estudo do BCCE produzido em uma empresa local visando, além da obtenção de blocos mais resistentes, o desenvolvimento do espírito científico nos alunos.  A pesquisa foi constituída de análises de resultados experimentais obtidos em laboratório, bem como de ensaios industriais.  Os mesmos demonstraram que a relação de água/cimento com valor de 0,8 mostrou-se mais adequada atingindo resistências a compressão na ordem de 2,14 MPa. Para além do observado experimentalmente ressalta-se que o escopo do projeto baseava-se na atividade de pesquisa aplicada no Ensino Médio com objetivo de fomentar a pesquisa no Ensino Médio Politécnico

Características bromatológicas e digestibilidade in vitro de quatro variedades de cana-de-açúcar submetidas ou não à aplicação de cal virgem

The experiment was conducted to evaluate the bromatological characteristics and the in vitro digestibility of four sugarcane varieties, subjected or not to hydrolysis, with quicklime. A completely randomized design was employed with three replications arranged in a 4 × 2 factorial scheme, with four sugarcane varieties (SP 52454, RB 867515, RB 855536 and IAC 862480), hydrolyzed or not. There was significant effect on brix (p < 0.05) and industrial fiber (p < 0.05), and IAC 862480 variety had the lowest levels of industrial fiber. There were no significant difference (p &gt; 0.05) in neutral detergent fiber, acid detergent fiber and lignin levels among the sugarcane varieties under analysis and for the sugarcanes, hydrolyzed or not. The use of sugarcane hydrolysis with 1% quicklime improves the in vitro digestibility of NDF and ADF, regardless of the variety studied. Hydrolysis with 1% quicklime did not alter the sugarcane chemical composition

Geomechanical Behaviour of Recycled Construction and Demolition Waste Submitted to Accelerated Wear

The construction industry is one of the most important sectors for economic and social development. However, it is responsible for more than 50% of the depletion of natural resources, for 40% of the energy consumption and construction and demolition waste (CDW) accounting for 30&ndash;60% of the total municipal solid waste generated worldwide. In this sense, the recycling of CDW is considered a safe alternative to the current trend, which can produce environmental and economic benefits, namely the reduction of the depletion of natural resources and the volume of waste sent to landfills. Some studies have shown promising results in the use of recycled CDW as geotechnical materials. However, the degradation performance induced by the construction procedures and weather conditions on the geotechnical behaviour of recycled CDW is still a research gap, creating an obstacle for its regular use in general engineering practice. This work evaluated the mechanical performance of recycled CDW over time when subjected to wetting&ndash;drying degradation cycles under different temperature and pH conditions. The effects of such degradation were then evaluated qualitatively (changes in particle size distribution and Proctor parameters) and quantitatively (stress&ndash;strain response and permeability). The results showed that 10 wetting&ndash;drying cycles and different compaction energies have no change in the particle size distribution of CDW compared to the original CDW. The shear strength parameters were very similar for the different degradation conditions except when different pH values were used, which may have weakened the grains and decrease the friction angle of the material. Regarding the permeability, all tested samples were classified in the same hydraulic conductivity range (very low) without significant changes induced by the degradation mechanisms

Study of the use of an Alkaline Hybrid Cement to improve the base of shallow foundations

A técnica de estabilização de solos com uso de cimento Portland é bastante difundida para resolver problemas de solos com baixa capacidade de suporte. No entanto, a nível mundial, 7% das emissões de CO2, principal gás contribuinte para ao aquecimento global, são devidas ao setor cimenteiro. Então, na busca por materiais alternativos ao cimento Portland, estão os cimentos alcalinos, que podem utilizar como matéria-prima subprodutos e/ou resíduos, contribuindo ainda para a redução de resíduos dispostos no meio ambiente. Apesar de ser uma técnica muito recente, alguns trabalhos sobre álcali-ativação com resíduos contendo sílica e cálcio, como precursores para estabilização química de solos, têm demonstrado ótimos desempenhos em termos de resistência e durabilidade. Porém, a maioria desses estudos estão relacionados a caracterização laboratorial desta técnica, contudo, a viabilidade e o impacto do processo de construção associado a essas soluções alternativas, bem como o efeito das condições de cura in situ nas propriedades mecânicas do solo estabilizado não podem ser avaliados adequadamente em laboratório. Neste sentido, o presente estudou a utilização de um cimento alcalino a base dos resíduos, cal de carbureto e pó de vidro moído, com (CA) e sem (SA) a introdução de um ativador alcalino de hidróxido de sódio na mistura. Propondo uma alternativa ao uso do cimento Portland, para a estabilização de uma areia fina para base de fundações superficiais, executadas sobre um solo residual de baixa capacidade de suporte. Assim, foram executados ensaios com placa de 30 cm em camadas confeccionadas com diferentes diâmetros (Dr 45 e 90 cm) e igual espessuras (Hr 30 cm) com um período de 14 e 120 dias de cura, além disso, ensaios com condições controladas de laboratório foram executados para comparação com os ensaios realizados em campo e, ainda, corpos-de-prova retirados das camadas curadas em campo foram submetidos a ensaios triaxiais. Os resultados demostraram que, ensaios em condições controladas de laboratório apresentam resistência à compressão simples maior para as misturas com o ativador de NaOH, principalmente a menores tempos de cura, porém para o maior tempo analisado, a tendência é de que as resistências se equiparem com as da mistura sem o ativador. Quando comparados com os ensaios de campo, estes apresentaram maior resistência, sugerindo assim que resultados em campo mostram grande influência das condições de cura, compactação, entre outros. Os diferentes diâmetros analisados demostraram dois mecanismos de ruptura, um de puncionamento, para as camadas de diâmetros de 45 cm e a ruptura das camadas de 90 cm. Os ensaios triaxiais para as diferentes misturas apresentaram pico pronunciado com posterior queda de resistência com comportamento inicialmente compressivo, seguida de uma posterior expansão. Amostras com a mistura com o ativador alcalino de NaOH apresentaram maior tensão desvio, maior ângulo de atrito e maior coesão. Além disso, apresentaram queda de ruptura acentuada e maior rigidez do material quando comparadas com a mistura sem o ativador. Das soluções analíticas testadas para determinar a capacidade de carga, o método de Hansen (1961) foi o que se mostrou adequado para estimativa das camadas de Dr 45 cm para ambas as misturas e o método de Meyerhof e Hanna (1978), apresentou uma estimativa de capacidade de carga próxima à obtida da camada tratada de Dr 90cm confeccionada com a mistura SA. Porém, quando aplicados para as misturas CA de mesmo diâmetro, o método superestimou a carga de ruptura, entretanto foi o qual apresentou resultados mais próximos dos obtidos para a mesma.Soil improvement through the use of Portland cement is a widespread solution for the low bearing capacity of soils. However, the cement sector is responsible for 7% of CO2 emissions, the main gas contributing to global warming. In the search for alternative materials to Portland cement, there are alkaline types of cement, which can use by-products and/or residues as raw materials, contributing to the reduction of waste disposed of in the environment. Despite being a very recent technique, some studies on alkali-activation with residues containing silica and calcium, as precursors for chemical stabilization of soils, have shown excellent performances in terms of strength and durability. Most of these studies are related to laboratory characterization of this technique, however, the feasibility and impact of the construction process associated with these alternative solutions, as well as the effect of in situ curing conditions on the improved mechanical properties of the soil cannot be properly evaluated in the laboratory. In this sense, the present study evaluated the use of alkaline cement-based residues, carbide lime, and ground glass powder, with (CA) and without (SA) the introduction of an alkaline sodium hydroxide activator in the mixture. Proposing an alternative to the use of Portland cement, for the improvement of fine sand for the base of shallow foundations, executed on a residual soil of low bearing capacity. Tests were performed with a 30 cm plate in layers of different diameters (Dr 45 and 90 cm) and equal thicknesses (Hr 30 cm) with a curing period of 14 and 120 days, also, tests with controlled laboratory conditions were performed for comparison with the field tests and, further, specimens removed from the layers cured in the field were subjected to triaxial tests. The results showed that tests under controlled laboratory conditions present higher uniaxial compression strength for mixtures with the NaOH activator, mainly to shorter curing times, but for the longest time analyzed, the tendency is for the strength to be equal with those of the mixture without the activator. When compared to the field tests, they showed greater strength, suggesting that field values are greatly influenced by curing and compaction conditions. The different diameters showed two distinctive rupture mechanisms, one for punching, for the 45 cm diameter layers, and the 90 cm layer rupture. The triaxial tests for the different mixtures showed a pronounced peak with a subsequent drop in strength with initially compressive behavior, followed by a subsequent expansion. Samples with the mixture with the alkaline NaOH activator showed higher stress deviation, greater friction angle, and greater cohesion. Besides, they showed a marked drop in rupture and greater material stiffness when compared to the mixture without the activator. Of the analytical solutions tested to determine the bearing capacity, the Hansen method (1961) was the one that proved adequate for estimating the Dr 45 cm layers for both mixtures, and the method of Meyerhof and Hanna (1978), presented an estimate of load capacity close to that obtained from the treated layer of Dr 90cm made with the SA mixture. However, when applied to CA mixtures of the same diameter, the method overestimated the rupture load, however, it was the one that showed results closer to those obtained for the same combination

Live-scale testing of granular materials stabilized with alkali-activated waste glass and carbide lime

The increasingly strong search for alternative materials to Portland cement has resulted in the development of alkali-activated cements (AAC) that are very effective at using industrial by-products as raw materials, which also contributes to the volume reduction in landfilled waste. Several studies targeting the development of AAC—based on wastes containing silicon and calcium—for chemical stabilization of soils have demonstrated their excellent performance in terms of durability and mechanical performance. However, most of these studies are confined to a laboratory characterization, ignoring the influence and viability of the in situ construction process and, also important, of the in situ curing conditions. The present work investigated the field application of an AAC based on carbide lime and glass wastes to stabilize fine sand acting as a superficial foundation. The assessment was supported on the unconfined compressive strength (UCS) and initial shear modulus (G0) of the developed material, and the field results were compared with those prepared in the laboratory, up to 120 days curing. In situ tests were also developed on the field layers (with diameters of 450 and 900 mm and thickness of 300 mm) after different curing times. To establish a reference, the mentioned precursors were either activated with a sodium hydroxide solution or hydrated with water (given the reactivity of the lime). The results showed that the AAC-based mixtures developed greater strength and stiffness at a faster rate than the water-based mixtures. Specimens cured under controlled laboratory conditions showed better results than the samples collected in the field. The inclusion of the stabilized layers clearly increased the load-bearing capacity of the natural soil, while the different diameters produced different failure mechanisms, similar to those found in Portland cement stabilization.The authors wish to explicit their appreciation to FAPERGS/CNPq 12/2014-PRONEX (Project #16/2551-0000469-2), MCT-CNPq (Editais INCT-REAGEO, Universal and Produtividade em Pesquisa) and MEC-CAPES (PROEX) for the support to the research group

Optimizing the selective precipitation of iron to produce yellow pigment from acid mine drainage

Acid mine drainage (AMD) in the coal mining industry is recognized as one of the major sources of environmental damage. The active treatment of AMD involves adding alkaline reagents to wastewater so as to raise pH and to precipitate dissolved metals in the form of oxides/hydroxides. Studies have shown that yellow pigment (goethite) can be produced from the iron present in AMD. However, the presence of other metals can prevent the formation of pigment. Therefore, this paper seeks to evaluate several processes for purifying iron sludge so as to obtain raw material that can be recovered from AMD and thereby obtain a good quality of yellow pigment. The experiments were carried out by causing precipitation with strong and weak bases and removing other metals from the sludge by washing and filtering the sludge or by centrifugation. The results show that the color, type and morphology of the compounds changed, depending on the number of contaminants, and that these factors are strongly dependent on the type of reagent and less dependent on the separation process and the repetition of washes.Peer Reviewe

DIVERGENT ROLE OF HEME OXYGENASE INHIBITION IN THE PATHOGENESIS OF SEPSIS

The reduction of neutrophil migration to an infectious focus is associated with a high mortality in severe sepsis. Previously, we showed that heme oxygenase (HO) products downregulate neutrophil recruitment in a noninfectious inflammatory model. The present study was designed to determine the role of HO in sepsis induced by cecal ligation and puncture (CLP) model. We demonstrated that pretreatment, but not the combination of pretreatment plus posttreatment with zinc protoporphyrin IX (ZnPP IX), an HO inhibitor, prevented the reduction of CXCR2 on circulating neutrophils and the failure of intraperitoneal neutrophil migration to the site of infection. Consequently, bacterial dissemination, systemic inflammatory response, and organ injury were prevented. In addition, pretreatment with the HO inhibitor avoided hypotension and consequently increased survival. Moreover, in mice subjected to severe CLP, the pretreatment, but not the combination of pretreatment plus posttreatment with ZnPP IX, prevented the increase of plasmatic free heme observed in nontreated severe CLP. The administration of exogenous hemin to mice subjected to moderate sepsis consistently increased the mortality rate. Furthermore, hemin resulted in a reduction of neutrophil migration both in vivo and in vitro. Altogether, our results demonstrated that pretreatment with the HO inhibitor prevents the pathological findings in severe CLP. However, the combination of pretreatment plus posttreatment with ZnPP IX enhances sepsis severity because of an increase in circulating levels of heme, which is deleterious to the host tissues and also inhibits neutrophil migration.FAPESP Fundacao de Amparo a Pesquisa do Estado de Sao PauloCAPES Coordenação de Aperfeiçoamento de Pessoal de Nível SuperiorCNPq Conselho Nacional de Pesquisa e Desenvolvimento Tecnologic