Heterogeneous kinetics of the reduction of chromium (VI) by elemental iron

• Type: Article in International Scientific Journal
• Date: 2010

Authors

fiuza, a (Author) FEUP; silva, a (Author) Other; carvalho, g (Author) Other; de la fuente, av (Author) Other; delerue-matos, c (Author) Other

Journal

Title: Journal of Hazardous Materials

Vol. 175

Pages: 1042-1047

ISSN: 0304-3894

Publisher: Elsevier

Indexing

ISI Web of Knowledge - 39 Citations

ISI Web of Science

Scopus - 21 Citations

COMPENDEX

Scientific classification

FOS: Engineering and technology > Environmental engineering

Other information

Authenticus ID: P-003-89T

DOI: 10.1016/j.jhazmat.2009.10.116

Abstract (EN): 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 a which is the order of the chemical reaction occurring at surface. We assumed alpha = 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.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 6