Síntese de geopolímeros a partir de cinzas pesadas e metacaulim para avaliação das propriedades de solidificação/imobilização de resíduos tóxicos

Tese (doutorado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Engenharia Química, Florianópolis, 2016.A utilização de resíduos industriais para produção de novos materiais favorece a retirada do passivo industrial do meio ambiente e minimiza a extração de matéria-prima da natureza. A solidificação/imobilização (S/I) de resíduos de metais pesados em matrizes geopoliméricas obtidas a partir de subprodutos industriais ambientalmente sustentável. Os geopolímeros são materiais desenvolvidos a partir de aluminossilicatos, residuais ou naturais de diversas fontes, ativados alcalinamente para formação de polímeros inorgânicos. Neste estudo, geopolímeros foram sintetizados a partir de cinzas pesadas e metacaulim (CP/M), nas proporções de 2:1 em massa, com o objetivo de se testar as propriedades de S/I de metais na matriz. São poucas as pesquisas utilizando cinzas pesadas em matrizes geopoliméricas. No entanto, as cinzas pesadas estão disponíveis em grandes proporções devido a queima do carvão mineral para geração de, aproximadamente, 41% da energia global. Para avaliação do ativador alcalino foram utilizadas as bases hidróxido de sódio (NaOH) e hidróxido de potássio (KOH) nas concentrações de 8 e 12 M, em composição com silicato de sódio (Na2SiO3) nas razões de 1:2 em volume. Para os testes de S/I de metais pesados foram utilizados 1, 10, 15 e 30 ml de uma solução residual provinda da decapagem de placas de circuito impresso contendo vários metais, entre eles Pb, Cr, Cu, Fe, Sn, As e Ni em diferentes proporções. Visando avaliar a eficiência da S/I, foram realizados ensaios para obtenção de extrato lixiviado e solubilizado. As análises da CP/M, dos geopolímeros sem a adição de metais pesados (GSMP) e dos geopolímeros com a adição de metais pesados (GCMP) foram realizadas através das seguintes técnicas: fluorescência de raios X (FRX), difração de raios X (DRX), espectrometria de massa por plasma acoplado indutivamente (ICP-MS), microscopia eletrônica de varredura (MEV), espectroscopia de energia dispersiva (EDS), espectroscopia no infravermelho por transformada de Fourier (FTIR) e ensaios de resistência à compressão. As amostras de geopolímeros apresentaram alto grau de S/I dos metais testados, sendo que, em algumas amostras, os resultados chegaram próximos a 100%. Os melhores resultados testados que atenderam as especificações das Normas Brasileiras para lixívia e solubilidade de resíduos tóxicos foram as amostras sintetizadas com 8 M de KOH e com 10 ml da solução contendo metais pesados (RCMP).Abstract: The use of industrial residue in the production of new materials promotes the removal of the industrial waste from the environment and minimizes the extraction of raw materials. The solidification/immobilization (S/I) of heavy metal residue in geopolymer matrices obtained from industrial sub-products is environmentally sustainable. The geopolymers are part of a new material technology that can be developed from aluminosilicates, waste or natural coming from different sources, alkali-activated for the formation of inorganic polymers. However, the understanding of the phases of gel formation in different materials is primordial. In this study, geopolymers where synthesized from heavy ash and metakaolin (BA/M), in the proportion of 2:1 of mass, aiming the test of the solidification/immobilization properties of heavy metals in the matrix. The number of researches that use heavy ash in polymeric matrices is very low. However, the heavy ashes are available in huge proportions, due to the burning of mineral coal for the production of roughly 41% of the global energy. For evaluation of the alkali activator, the sodium hydroxide (NaOH) and potassium hydroxide (KOH) bases were used in the concentrations of 8 and 12 M in the composition of sodium silicate (Na2SiO3) in 1:2 volume ratios. For the testing of S/I of metals were used 1, 10, 15 and 30 ml of residual solution coming from the pickling of printed circuit boards containing several metals including Pb, Cr, Cu, Fe, Sn, As and Ni in different proportions. To evaluate the efficiency of the S/I, tests were performed to obtain leached and solubilized extract. Analyses BA/M, of geopolymers without the addition of heavy metals (GWHM) and geopolymers containing heavy metals (GCHM) was carried out through X-Ray Fluorescence (XRF), X-Ray Diffraction (XRD); Inductively Coupled Plasma Mass Spectrometry (ICP-MS); Scanning Electron Microscope (SEM) and Energy-Dispersive X-ray Spectroscopy (EDS); Spectroscopy in Fourier Transform Infrared (FTIR), and compressive strength tests. All geopolymer samples showed a high degree of S/I of the tested metals; in some samples, the results reached nearly 100%. The best results tested according to specifications of the Brasilian Standards for bleach and solubility of toxic waste were synthesized samples with 8 M KOH and 10 ml of solution containing heavy metals (HMW)

Desenvolvimento de geopolímeros a partir de cinzas pesadas oriundas da queima do carvão mineral e metacaulim sintetizado a partir de resíduo da indústria de papel

Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Engenharia QuímicaA presente pesquisa concentrou-se no estudo e desenvolvimento de um material com propriedades cimentícias. Trata-se de um polímero inorgânico, formado pela ativação de aluminossilicatos (Al2O3.SiO2) amorfos, que reagem em um meio fortemente alcalino, chamado geopolímero. Como matéria-prima foram utilizadas cinzas pesadas, resíduo da queima de carvão mineral (Termoelétrica do Sul do Brasil), como fonte de aluminossilicatos; e o meio alcalino foi hidróxido de sódio (NaOH) e silicato de sódio (Na2SiO3), utilizados como ativadores. As cinzas pesadas cristalizam-se parcialmente durante a queima e perdem parte de seu estado amorfo, devido a isso suas propriedades reativas para combinar quimicamente durante a polimerização são reduzidas. Para aumentar as propriedades reativas da cinza pesada foi adicionado metacaulim, processado a partir de resíduos da indústria de papel. Os resíduos sólidos e as amostras geopoliméricas passaram por caracterização e, as principais análises envolvidas no processo, foram: fluorescência de raios X (FRX), difração de raios X (DRX), microscopia eletrônica de varredura (MEV), espectrometria no infravermelho com transformada de Fourier (FTIR), análise termogravimétrica (TGA) e a análise térmica diferencial (DTA). Também foram realizados ensaios de resistência à compressão nas amostras geopoliméricas para avaliar o grau de polimerização, uma vez que, quanto mais polimerizada estiver a estrutura, maior será a resistência. Com 24 horas de cura as pastas geopoliméricas atingiram resistências à compressão de até 10 megapascais (MPa) e, com 90 dias de cura, aproximadamente, 25 MPa. Os melhores resultados foram obtidos com amostras ativadas com 15 mols/l de NaOH na mistura com silicato de sódio e nas proporções de 2:1 entre a cinza pesada e o metacaulim. Os resultados obtidos através das análises de caracterização das amostras foram satisfatórios e demonstraram que os resíduos de cinza pesada e metacaulim, quando ativados com hidróxido de sódio e silicato de sódio, são uma alternativa viável para a produção de materiais geopoliméricos.This research concentrated on the study and development a material with cementitious properties. It is an inorganic polymer formed by the activation of aluminosilicates (Al2O3.SiO2) amorphous, which reacts in a strongly alkaline medium, called geopolymer. As raw material were used bottom ash residue from burning mineral coal (Thermoelectric South of Brazil) the alkaline medium were sodium hydroxide (NaOH) and sodium silicate (Na2SiO3), used as activators. Because the bottom ash partially crystallizes during burning and loses its amorphous state, its reactive properties to combine chemically during polymerization are reduced. For o increase the bottom ash reactive properties, metakaolin synthesized from paper industry waste was added. The solid waste and the geopolymeric samples passed for characterization and main analysis involved in the process, were: X-ray fluorescence (XRF), X-ray Diffraction (XRD), scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), differential thermal analysis (DTA). Were also conducted of compressive strength tests geopolymer sample, to measure the degree of polymerization, since the more polymerized structure, the more will resistance. With 24 hours of curing folders geopoliméricas reached compressive strengths of up to 10 megapascals (MPa) and with 90 days of curing approximately, 25 MPa. The best results were obtained in samples activated with 15 mol / l NaOH in a mixture with sodium silicate and the proportion of 2:1 between the ash and metakaolin. The results obtained of analysis characterization were satisfactory, demonstrating that waste bottom ash and metakaolin activated with sodium hydroxide and sodium silicate are viable alternative to production of geopolymer materials

Effect of synthesis parameters on the performance of alkali-activated non-conformant EN 450 pulverised fuel ash

The fly ash reported in this paper is coarser than conventional pulverised fuel ash (PFA), with loss on ignition (LOI) exceeding 10.8%. Consequently, it is precluded from being used as a supplementary cementitious material (SCM) according to EN 450 and disposed in landfills. Alkali-activation of such PFAs is considered here. Three concentrations of sodium hydroxide (NaOH) were separately blended with water glass at different ratios to modify the silica modulus. Heat of reaction, setting time, compressive strength and drying shrinkage were investigated as a function of activator composition. Specimens were either cured at room temperature or hydro-thermally treated at 75 °C for five hours. The results show that by optimizing the activator composition, a binder with a 28 day compressive strength of 25 MPa can be synthesised from such PFAs even at room temperature. Among the activator parameters, the alkali content was observed to be most influential

Management and valorisation of wastes through use in producing alkali-activated cement materials

There is a growing global interest in maximising the re-use and recycling of waste, to minimise the environmental impacts associated with waste treatment and disposal. Use of high-volume wastes in the production of blended or novel cements (including alkali-activated cements) is well known as a key pathway by which these wastes can be re-used. This paper presents a critical overview of the urban, agricultural, mining and industrial wastes that have been identified as potential precursors for the production of alkali-activated cement materials, or that can be effectively stabilised/solidified via alkali activation, to assure their safe disposal. The central aim of this review is to elucidate the potential advantages and pitfalls associated with the application of alkali-activation technology to a wide variety of wastes that have been claimed to be suitable for the production of construction materials. A brief overview of the generation and characteristics of each waste is reported, accompanied by identification of opportunities for the use of alkali-activation technology for their valorisation and/or management

Novel porous geopolymeric formulation as green material applied to the recovery of contaminated effluent aiming environmental protection

\u3cp\u3eGeopolymeric materials have been widely applied in a wide variety of industrial processes due to their structural versatility, which depends primarily on the raw material, its composition and the techniques used in the synthesis. This work focused on the synthesis of highly porous geopolymers (PGPs) to be applied as adsorbents in the treatment of effluents. Different compositions, which involved the addition of rice husk silica, were tested to optimize the porosity of the materials synthesized. In the synthesis of PGPs, the best mass proportions of raw materials and reagents were 5.0:0.4:0.6:1.9:0.55:3.3 for K/MK/RHS/KOH/Na\u3csub\u3e2\u3c/sub\u3eSiO\u3csub\u3e3\u3c/sub\u3e/H\u3csub\u3e2\u3c/sub\u3eO, respectively, and the molar ratio for SiO\u3csub\u3e2\u3c/sub\u3e/Na\u3csub\u3e2\u3c/sub\u3eO was 3.3. The formation of geopolymer nanoparticles was favored by the mixture of different materials in predefined proportions, and in the presence of activated amorphous silica microparticles. The BET (Brunauer-Emmett-Teller) surface area of the porous geopolymers was 76.93 m\u3csup\u3e2\u3c/sup\u3e/g and the BJH (Barrett-Joyner-Halenda) value was in the range of 69.84 m\u3csup\u3e2\u3c/sup\u3e/g. Methylene blue was used as a model compound for the evaluation of the performance of the material when applied to adsorptive processes, both experimentally and theoretically. Batch experiments were conducted to determine the kinetics of MB adsorption in the prepared PGP. The material demonstrated excellent characteristics for the application in the removal of contaminants from effluents by adsorption.\u3c/p\u3

Production of vitreous materials from mineral coal bottom ash to minimize the pollution resulting from the waste generated by the thermoelectrical industry

Mineral coal bottom ash exerts a great impact on the environment due to the presence of heavy metals in its composition and the lack of an adequate area for disposal. Vitreous materials were synthesized from bottom ash to be employed as a by-product. The bottom ash was subjected to an X-ray fluorescence (XRF) analysis to evaluate the oxide composition present in the material. To study the effect of bottom ash in the attainment of glass, a simplex lattice design for experiments with blends was employed. The elements considered in the design were: bottom ash; sodium carbonate (Na2CO3) and calcium oxide (CaO), both used as melting agents; magnesium oxide (MgO), which was used as a stabilizer for the vitreous network. For the characterization of the glasses, X-ray diffraction (XRD), differential scanning calorimetry (DSC) and Fourier transform infrared spectrometry (FTIR) were carried out. Ten different formulations were tested. The results indicated that two out of the ten formulations formed a crystalline phase, which is undesirable for a vitreous material. In the statistical analyses, the Pareto Diagram and the response surface showed that the glass transition and softening temperatures were strongly influenced by the level of calcium oxide and magnesium oxide, as well as that of bottom ash, resulting in an increase in the softening and glass transition temperatures. Resumen: La escoria de carbón mineral afecta profundamente al medio ambiente por la existencia de metales pesados en su composición y la falta de un área adecuada para su eliminación. Los materiales vítreos se sintetizaron a partir de escoria para ser empleados como subproducto. La escoria se sometió a un análisis de fluorescencia de rayos X (XRF) para evaluar la composición de óxido presente en el material. Para estudiar el efecto de la escoria en la obtención de vidrio, se empleó un diseño de malla simple para experimentos con mezclas. Los elementos que se valoraron en el diseño fueron: escoria; carbonato de sodio (Na2CO3) y óxido de calcio (CaO), ambos utilizados como agentes de fusión; óxido de magnesio (MgO), que se utilizó como estabilizador de la red vítrea. Para la caracterización de los vidrios se llevaron a cabo difracción de rayos X (XRD), calorimetría de barrido diferencial (DSC) y espectrometría de infrarrojos por transformada de Fourier (FTIR). Se probaron 10 formulaciones diferentes. Los resultados indicaron que 2 de las 10 formulaciones formaron una fase cristalina, que es indeseable para un material vítreo. En los análisis estadísticos, el diagrama de Pareto y la superficie de respuesta mostraron que la transición vítrea y las temperaturas de reblandecimiento estaban muy influidas por el nivel de óxido de calcio y de óxido de magnesio, así como por el de escoria, lo que aumentaba las temperaturas de reblandecimiento y transición vítrea. Keywords: Mineral coal, Solid waste, Bottom ash, Pollution, Glasses, Palabras clave: Carbón mineral, Desechos sólidos, Escoria, Contaminación, Vidrio