Kinetic evidence for the reaction of O?? radical ions and peroxodisulfate in alkaline aqueous solutions

Mártire, Daniel O.; González, Mónica C.

doi:10.1002/(sici)1097-4601(1998)30:7<491::aid-kin5>3.0.co;2-n

Cited by 7 publications

(1 citation statement)

References 21 publications

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“…At lower pH, sols become more stable. Colloidal dispersions of pH > 10.5 were not used because (i) an efficient scavenging of sulfate radicals by HO - ions takes place and (ii) in this pH range colloidal silica becomes increasingly solubilized and the alkali silicate thus formed destabilizes the remaining colloids.…”

Section: Methodsmentioning

confidence: 99%

A Kinetic Study of the Reactions of Sulfate Radicals at the Silica Nanoparticle−Water Interface

et al. 2003

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Sulfate radicals, SO 4 •-, were generated using flash photolysis of aqueous S 2 O 8 2solutions and the reactions of the inorganic radicals with the surface of suspended silica nanoparticles (NP) investigated. In the presence of colloidal silica no absorption traces due to SO 4 •radicals are observed at 100 µs after the flash of light. However, two transient species with absorption maxima around 320 and 600 nm are formed. A kinetic analysis of the experimental results indicate that SO 4 •radicals are adsorbed on the NP surface, leading to the formation of an adduct, with λ max ≈ 320 nm ( ≈ 7000 cm -1 M -1 ), and showing similar reactivity to that observed for the sulfate radical in aqueous solutions. The NP-sulfate radical adducts react with adsorbed water, and with single and geminal SiOsites with reaction rate constants of 1.5 × 10 14 × e -(58(12)kJ/mol)/RT s -1 , < 10 3 × e -(2(17)kJ/mol/RT s -1 and < 10 11 × e -(46(13)kJ/mol/RT s -1 , respectively. Two different SiO • surface defects, showing similar spectra (λ max ≈ 600 nm) but different reactivities, are formed from the reaction of NP-sulfate radicals and deprotonated geminal and single silanols.

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Section: Methodsmentioning

confidence: 99%