Transmission Electron Microscopy Characterization of the Products Obtained during Arsenic

REGINA P. CARVALHO; SYLVIA S.DANTAS; VIRGINIA S.T.CIMINELLI; I K LEVY; M LITTER

Aguas de Lindoia, San Pablo, Brasil

Congreso; XXXII Encontro Nacional de Fisica da Materia Condensada; 2009

Arsenic from mining wastewaters or from natural sources has evident harmful effects for living creatures. This justifies the study of different removing methods. Metallic iron - also called zerovalent iron - is being used in the form of wires or waste materials in low cost processes for arsenic removal. Iron corrosion produces oxides and hydroxides whose interaction with arsenic makes possible its removal by adsorption and/or precipitation. Ultraviolet radiation intensifies the removal process. Simple devices where contaminated water is contacted with an iron source and exposed to the sunshine allow the decontamination of water for human consumption. This technique is being applied for water treatment in remote regions with low income population. In this work we analyzed the products of the reaction between iron wires and an aqueous arsenic solution, after exposition to ultraviolet radiation. The investigation is part of a collaboration project between Brazil and Argentina in the CYTED Iberoarsen network. The reaction products were analyzed using Raman Spectroscopy and Transmission Electron Microscopy. This last technique is usual for condensed matter characterization, but less commonly used in environmental and hydrometallurgy studies. The TEM images indicate the presence of two precipitated phases, one highly crystalline, and the other amorphous or with low crystallinity. These phases can be identified using diffraction patterns. The results were compared with Raman Spectroscopy results. The two techniques gave equivalent information and showed to be useful for the characterization of the studied samples.Arsenic from mining wastewaters or from natural sources has evident harmful effects for living creatures. This justifies the study of different removing methods. Metallic iron - also called zerovalent iron - is being used in the form of wires or waste materials in low cost processes for arsenic removal. Iron corrosion produces oxides and hydroxides whose interaction with arsenic makes possible its removal by adsorption and/or precipitation. Ultraviolet radiation intensifies the removal process. Simple devices where contaminated water is contacted with an iron source and exposed to the sunshine allow the decontamination of water for human consumption. This technique is being applied for water treatment in remote regions with low income population. In this work we analyzed the products of the reaction between iron wires and an aqueous arsenic solution, after exposition to ultraviolet radiation. The investigation is part of a collaboration project between Brazil and Argentina in the CYTED Iberoarsen network. The reaction products were analyzed using Raman Spectroscopy and Transmission Electron Microscopy. This last technique is usual for condensed matter characterization, but less commonly used in environmental and hydrometallurgy studies. The TEM images indicate the presence of two precipitated phases, one highly crystalline, and the other amorphous or with low crystallinity. These phases can be identified using diffraction patterns. The results were compared with Raman Spectroscopy results. The two techniques gave equivalent information and showed to be useful for the characterization of the studied samples.