http://www.cnr.it/ontology/cnr/individuo/prodotto/ID42128

CHROMIUM (VI) REDUCTION BY SULPHUR (IV) IN AQUEOUS SOLUTIONS (Articolo in rivista)

Type

Articolo in rivista (Classe)
Prodotto della ricerca (Classe)

Label

CHROMIUM (VI) REDUCTION BY SULPHUR (IV) IN AQUEOUS SOLUTIONS (Articolo in rivista) (literal)

Anno

2006-01-01T00:00:00+01:00 (literal)

Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#doi

10.1016/j.marchem.2005.02.003 (literal)

Alternative label

PETTINE M. (a); TONNINA D. (a); MILLERO F.J. (b) (2006)
CHROMIUM (VI) REDUCTION BY SULPHUR (IV) IN AQUEOUS SOLUTIONS
in Marine chemistry (Print); ELSEVIER SCIENCE BV, PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS, AMSTERDAM (Paesi Bassi)
(literal)

Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#autori

PETTINE M. (a); TONNINA D. (a); MILLERO F.J. (b) (literal)

Pagina inizio

31 (literal)

Pagina fine

41 (literal)

Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#url

http://www.sciencedirect.com/science/article/pii/S0304420305001738 (literal)

Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#numeroVolume

99 (literal)

Rivista

Marine chemistry (Rivista)

Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#note

fascicolo (1-4) (literal)

Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#pagineTotali

11 (literal)

Note

ISI Web of Science (WOS) (literal)

Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#affiliazioni

a) Water Research Institute, Consiglio Nazionale delle Ricerche, via Reno 1, Rome 00198, Italy; b) Rosenstiel School of Marine and Atmospheric Chemistry, University of Miami, 4600 Rickenbacker Causeway, Miami, FL 33149, USA (literal)

Titolo

CHROMIUM (VI) REDUCTION BY SULPHUR (IV) IN AQUEOUS SOLUTIONS (literal)

Abstract

The rates of the reduction of Cr(VI) with S(IV) were measured in deaerated NaCl solution as a function of pH, temperature and ionic strength. The rates of the reaction were found to be first order with respect to Cr(VI) and second order with respect to S(IV), in agreement with previous results obtained at concentrations two order higher than the present study. The reaction also showed a first-order dependence of the rates on the concentration of the proton and a small influence of temperature with an apparent energy of activation DHapp of 22.8 ± 3.4 Kj/mol. The rates were independent of ionic strength from 0.0 1 to 1 M. The rate of Cr(VI) reduction is described by the general expression - d[Cr(VI)]/dt = k[Cr(VI)] [S(IV)](2) where k (M(-2) s(-1)) can be determined from the logk = 12.2 ± 0.7 - (0.95 ± 0.04)pH - (1311.5 ± 210)/T (sigma = ± 0. 11) in the pH range 2 to 5, from 5 to 40 °C and 0.01 to 1 M. The effect of pH and ionic strength on the reaction suggest that the rates are due to H(2)CrO(4) + H(2)SO(3) ->((kH2A-H2B)) products HCrO(4)(-) + H(2)SO(3) ->((kHA-H2B)) products H(2)CrO(4)(-) + H(2)SO(3) ->((kH2A-HB)) products where H(2)A=H(2)CrO(4), HA=HCrO(4)(-), H(2)B=H(2)SO(3) and HB=HSO(3)(-). The overall rate expression over the investigated pH range can be determined from k = k(H2A-H2B)(alpha(H2A))(alpha(H2B))(2) + k(HA-H2B)(alpha(HA))(alpha(H2B))(2) + k(H2A-HB)(alpha(H2A))(alpha(HB))(2) with k(H2A-H2B)=5.0 x 10(7), k(HA-H2B)=1.5 x 10(6) and k(H2A-HB)=6.7 x 10(7). Fe(III) in the range 1.5 to 20 µM exerts a small catalytic effect on the reaction and significantly lowers the initial concentration of Cr(VI) compared to the nominal value. Contrary to Fe(III), formaldehyde (20 to 200 µM) reacts with S(IV) to form the hydroxymethanesulfonate adduct (CH(2)OHSO(3)(-)), which does not react with Cr(VI). Major cations Mg(2+) and some minor elements such as Ba(2+) and Cu(2+) did not affect the rates. The application of this rate law to environmental conditions suggest that this reaction may have a role in acidic solutions (aerosols and fog droplets). This reaction becomes more important in the presence of high Fe(III) and low HMS concentrations, contributing to affect the atmospheric transport of chromium species and the distribution of redox species of chromium, which reach surface water from atmospheric depositions. (c) 2006 Elsevier B.V. All rights reserved. (literal)

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