As principais preocupacoes com relacao a geracao de residuos estao voltadas para os efeitos que estes materiais podem ter sobre a saude humana e sobre o meio ambiente, uma vez que os residuos perigosos produzidos pelas industrias precisam particularmente de atencao e cuidado, pois quando incorretamente gerenciados, tornam-se uma grave ameaca ao meio ambiente. Neste contexto, este trabalho mostra os estudos realizados visando a reciclagem da lama vermelha como materia-prima para a obtencao de compostos de titânio. O estudo abrange tres rotas hidrometalurgicas: lama vermelha calcinada a 900°C (LV900), lama vermelha sem tratamento termico (LV-STT) e lama vermelha sinterizada em atmosfera redutora (LV1300). Os experimentos de lixiviacao foram realizados com valores de temperaturas de 60, 80 e 90 °C e concentracoes de acido sulfurico de 20 e 30% em volume. Junto com o estudo de lixiviacao foi realizada a modelagem matematica do processo de lixiviacao. Os estudos realizados neste trabalho mostram que a lama vermelha pode ser aplicada como fonte de materia-prima alternativa para a concentracao e posterior recuperacao de compostos de titânio. A modelagem cinetica dos dados das curvas de extracao em funcao do tempo e o modelo matematico desenvolvidos no presente trabalho mostram que a reacao quimica e a etapa que descreve esses ensaios de lixiviacao. Os modelos desenvolvidos tambem possibilitaram a obtencao de parâmetros cineticos, tais como: energia de ativacao e as velocidades das reacoes quimicas do processo de lixiviacao.

/pdf/estudo-da-extracao-de-compostos-de-ferro-da-lama-vermelha-51ofo7g98i.pdf

Chemical fixation and solidification of hazardous wastes

Estudo da extração de compostos de ferro da lama vermelha visando a extração e/ou recuperação de compostos de titânio

Highway bridges in the United States are painted to resist corrosion and to help maintain the structural integrity of the bridge. Periodically., it is necessary to remove the existing paint so that the surface can be repainted. Most often the removal process consists of blasting the surface with an abrasive such as sand or slag. The blast media then contains elements present in the paint, such as cadmium, chromium and lead. The spent media may be a hazardous waste as defined by EPA's Toxicity Characteristic (TC) criterion. This criterion uses the Toxicity Characteristic Leaching Procedure (TCLP) to determine whether a waste is classified as a hazardous waste. This procedure subjects the waste to a highly acidic environment in which chemicals can leach out of the waste. The leachate environment is then analyzed to determine the concentration of chemical leached, which must fall within the TC criterion. Some spent blasting material has been shown to have TCLP metal concentrations exceeding the TC criterion. The Texas Department of Transportation (TxDOT) has begun to recycle spent abrasive media in portland cement-based concrete using solidification/stabilization (S/S) techniques. This technology is designed to immobilize the metals, while recycling the spent abrasive media as a component in non-structural concrete. This study has revealed the effectiveness of portland cement-based S/S systems in recycling contaminated spent abrasive media in portland cement-based concrete. The long-term leaching behavior of metals from these concrete products was examined using sequential extraction leaching tests.

Solidification/stabilization of used abrasive media for non-structural concrete using portland cement

Highway bridges in the United States are painted to resist corrosion and to help maintain the structural integrity of the bridge. Periodically, it is necessary to remove the existing paint so that the surface can be repainted. Most often the removal process consists of blasting the surface with an abrasive such as sand or slag. The blast media then contains elements present in the paint, such as cadmium, chromium and lead. The spent media may be a hazardous waste as defined by the Environmental Protection Agency's (EPA's) Toxicity Characteristic (TC) criterion. This criterion uses the Toxicity Characteristic Leaching Procedure (TCLP) to detemine whether a waste is classified as a hazardous waste. This procedure subjects the waste to a highly acidic environment in which chemicals can leach out of the waste. The leachate environment is then analyzed to determine the concentration of chemical leached, which must fall within the TC criterion. Some spent blasting material has been shown to have TCLP metal concentrations exceeding the TC criterion. The Texas Department of Transportation (TxDOT) has begun to recycle spent abrasive media in portland cement-based concrete using solidification/stabilization (S/S) techniques. This technology is designed to immobilize the metals, while recycling the spent abrasive media as a component in non-structural concrete. This study has revealed the effectiveness of portland cement-based S/S systems in recycling contaminated spent abrasive media in portland cement-based concrete. The long-term leaching behavior of metals from these concrete products was examined using sequential extraction leaching tests.

Solidification/stabilization of used abrasive media for non-structural concrete using portland cement. interim report

New methods for assessing solidification/stabilization (S/S) of hazardous waste using solid-state nuclear magnetic resonance are developed for the purpose of diagnosing on a microscopic level the performance of S/S as a hazardous waste disposal technique. There are four techniques developed and described in this dissertation: (1) Solid-state deuterium NMR spectroscopy is used to determine if a particular deuterated organic waste is effectively solidified/stabilized and to determine the lower limit of the bond strength between the waste and the cement matrix; (2) Constant time pulsed field gradient $\sp1$H NMR spectroscopy is tested on a liquid waste encapsulated within a solidified matrix to determine if droplets of liquid waste are entrapped within a solidified matrix. It yields a size distribution image of vesicles containing fluids, and measures the diffusion rate of organic materials in solid matrices; (3) Three-dimensional NMR imaging of a hazardous waste/cement sample is tested for the determination of the pore structure connectivity pattern and the observation of waste leaching; (4) NMR hole-burning spectroscopy is attempted for the study of the microscopic motions of waste in the cement matrix. These NMR techniques give information on the microscopic waste/cement interactions while providing a nondestructive evaluation of the quality of S/S process much superior to the destructive techniques such as leaching. 

Chemical fixation and solidification of hazardous wastes

Citations

Estudo da extração de compostos de ferro da lama vermelha visando a extração e/ou recuperação de compostos de titânio

Solidification/stabilization of used abrasive media for non-structural concrete using portland cement

Solidification/stabilization of used abrasive media for non-structural concrete using portland cement. interim report

Development of New Methods for Assessing Solidification/Stabilization of Hazardous Waste Using Solid-State Nuclear Magnetic Resonance Techniques.

The potential leachability of mine tailings encapsulated in structural concrete

Related Papers (5)

Fundamental aspects of cement solidification and stabilisation

The chemistry of cement and concrete

The binding chemistry and leaching mechanisms of hazardous substances in cementitious solidification/stabilization systems

Stabilization and Solidification of Hazardous, Radioactive, and Mixed Wastes

Hazardous waste management