Utilize este identificador para referenciar este registo: http://hdl.handle.net/10400.22/3014
Título: Heterogeneous kinetics of the reduction of chromium (VI) by elemental iron
Autor: Fiúza, António
Silva, Aurora
Carvalho, Goreti
Fuente, António V. de la
Delerue-Matos, Cristina
Palavras-chave: Chromium reduction
Reactive permeable barriers
Heterogeneous kinetics
Data: 2010
Editora: Elsevier
Relatório da Série N.º: Journal of Hazardous Materials; Vol. 175, Issues 1-3
Resumo: Zero valent iron (ZVI) has been extensively used as a reactive medium for the reduction of Cr(VI) to Cr(III) in reactive permeable barriers. The kinetic rate depends strongly on the superficial oxidation of the iron particles used and the preliminary washing of ZVI increases the rate. The reaction has been primarily modelled using a pseudo-first-order kinetics which is inappropriate for a heterogeneous reaction. We assumed a shrinking particle type model where the kinetic rate is proportional to the available iron surface area, to the initial volume of solution and to the chromium concentration raised to a power ˛ which is the order of the chemical reaction occurring at surface. We assumed α= 2/3 based on the likeness to the shrinking particle models with spherical symmetry. Kinetics studies were performed in order to evaluate the suitability of this approach. The influence of the following parameters was experimentally studied: initial available surface area, chromium concentration, temperature and pH. The assumed order for the reaction was confirmed. In addition, the rate constant was calculated from data obtained in different operating conditions. Digital pictures of iron balls were periodically taken and the image treatment allowed for establishing the time evolution of their size distribution.
Peer review: yes
URI: http://hdl.handle.net/10400.22/3014
Versão do Editor: http://www.sciencedirect.com/science/article/pii/S0304389409017671#
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