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Reactions of Cl • /Cl 2 •− Radicals with the Nanoparticle Silica Surface and with Humic Acids: Model Reactions for the Aqueous Phase Chemistry of the Atmosphere
Author(s) -
Caregnato Paula,
Gara Pedro D.,
Bosio Gabriela N.,
Mártire Daniel O.,
Gonzalez Mónica C.
Publication year - 2007
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.2007.00087.x
Subject(s) - chemistry , radical , aqueous solution , deprotonation , reaction rate constant , humic acid , chlorine , flash photolysis , inorganic chemistry , chemical reaction , kinetics , organic chemistry , ion , fertilizer , physics , quantum mechanics
ABSTRACT Reactions of chlorine radicals might play a role in aqueous aerosols where a core of inorganic components containing insulators such as SiO 2 and dissolved HUmic‐LIke Substances (HULIS) are present. Herein, we report conventional flash photolysis experiments performed to investigate the aqueous phase reactions of silica nanoparticles (NP) and humic acid (HA) with chlorine atoms, Cl • , and dichloride radical anions, Cl 2 •− . Silica NP and HA may be taken as rough models for the inorganic core and HULIS contained in atmospheric particles, respectively. Both Cl • and Cl 2 •− were observed to react with the deprotonated silanols on the NP surface with reaction rate constants, k ± σ, of (9 ± 6) × 10 7 M −1 s −1 and (7 ± 4) × 10 5 M −1 s −1 , respectively. The reaction of Cl • with the surface deprotonated silanols leads to the formation of SiO • defects. HA are also observed to react with Cl • and Cl 2 •− radicals, with reaction rate constants at pH 4 of (3 ± 2) × 10 10 M −1 s −1 and (1.2 ± 0.3) × 10 9 M −1 s −1 , respectively. The high values observed for these constants were discussed in terms of the multifunctional heterogeneous mixture of organic molecules conforming HA.