Abstract. OH radicals play a very important role in non-thermal plasma chemical reactions for decomposition of gaseous pollutants or synthesis of
methanol from methane, etc. In this paper, the CO oxidation monitoring method, which has been used in atmospheric chemistry, was examined to measure
the concentration of OH radicals produced by a pulsed discharge plasma. The concentration of OH radicals in the discharge plasma of H2O/Ar mixture gas
was estimated by measuring the amount of CO2 produced through oxidation of CO by OH radicals. The experimental results and the calculated results
showed that it is possible to measure OH radicals using this simple method. In this experimental work, the maximum concentration of OH radicals
produced by the pulsed discharge plasma of H2O/Ar was measured to be 9.4×1014 molecules cm-3 pulse-1. Within the temperature range investigated in
this study (50–150°C), the formation of OH radicals increased with increase in the specific input energy (discharge energy dissipated in unit
volume of the gas; SIE) value and the content of H2O; in contrast, it decreased with increase in the gas temperature.Hilski - 21-2-2007 at 06:05
I find this OH radical stuff pretty interesting. I never really read much about it until recently when researching electrolytic production of
Fenton's reagent. That's when I came across the papers I asked for in the references thread.roamingnome - 21-2-2007 at 10:02
Yes and in reality Fenton's reagent is probably the most down the earth method one could hope for…. The article which i grabbed up as well seemed to
say that the OH radical is the mechanism, so I was just kicking around using a cheap arc welder or whatever to make these radicals without them being
eating up in side reactions…
cheers to OH radicals if thats the case...12AX7 - 21-2-2007 at 16:59
What do OH radicals smell like? I'm guessing ozone, much like the smell of chlorine and NO2. (Do they react with each other or with O2 to make
ozone?)
TimHilski - 21-2-2007 at 17:55
Quote:
What do OH radicals smell like? I'm guessing ozone, much like the smell of chlorine and NO2. (Do they react with each other or with O2 to make ozone?)
Tim
I'd say it would depend on the manner in which they were produced. According to some stuff I have been reading, the most significant sources of OH
radicals in the troposphere are from ozone-alkene reactions, so who knows what that would smell like. Electrically produced ones would probably smell
like whatever was in the water they were made in.
But then again, I'm just guessing, and really have no idea.Ozone - 21-2-2007 at 19:25
OH radicals are also produced when ionizing radiation goes though water (and also, cells). The oxidative damage imparted by ionizing radiation to a
living cell is predominated by OH and OOH radical species. In terms of oxidative potential, the OH radical is right under Fluorine (so I would not
like to be smelling them, but then, they will probably react with something long before they get to your nose).
Best,
O3roamingnome - 21-2-2007 at 19:45
thats funny, in the first thought i was like yeah what do they smell like, then in the next thought.... wait these things are so reactive that ill
probably never smell again....guy - 22-2-2007 at 14:56
Shine really short ultraviolet light onto oxygen in the presence of water? Or you can shine ultraviolet light (~310nm) on ozone and react that with
water.12AX7 - 22-2-2007 at 15:20
I would assume that ozone, chlorine, NO2, etc. get their smell from their oxidizing properties. (Smell them for long enough and you *won't* smell,
eh?) Hence why, despite their being differently shaped molecules, they all smell similar. I would imagine fluorine and OH smelling similarly, if
they are stable enough to interact with the sensation of smell as such.
I know UV-B can be used to disinfect water, supposedly by making O3 in situ. Would this also make OH and other dissociated-O2 based species?
Timguy - 22-2-2007 at 15:29
I think it would make OH radicals. Anytime a singlet oxygen reacts with water, it can form a hydroxyl radical.tupence_hapeny - 25-3-2007 at 23:31
Here is a patent regarding the generation of hydroxyl radicals via the use of a peroxide (some others) in company with an alkali metal-hydroxide, in
combination with UV light (with or without the addition of a Titanium dioxide catalyst). The patent repeatedly points out that it does not employ
hypochlorite, and its controllability (remove the UV source, it stops - return UV it restarts):
Here is a thesis on the oxidation of baggasse using hydroxyl radicals supposedly generated in situ using a mixture of the baggasse, hypochlorite and
hydrogen peroxide (which makes no reference to a need for UV light):
This last paper makes some reference to the effectiveness of Fe catalysts, although a google search on "hypochlorite + peroxide + hydroxyl radical"
makes for some interesting reading (so much so, that if and when I have any
oxidising to do, I intend to try this shit, it works with 3% peroxide). Heres
another paper on the generation of the same with electrolysis:
It might be worthwhile investing in a UV light and trying this, also for cleaning benches, etc. as the mix was originally patented as a potent
biocidal agent for labs.
[Edited on 26-3-2007 by tupence_hapeny]
[Edited on 26-3-2007 by tupence_hapeny]roamingnome - 31-3-2007 at 13:04
Obtaining a ultrasonic tranducer as been on my mind for a while but i have renewed interst for too many reasons...
The results show that (1) lower frequency ultrasound generates the radicals more efficiently, (2) the radical concentration initially increases
linearly with time and the ultrasound intensity, and then (3) saturates at a value which is independent of the ultrasound intensity
The Journal of the Acoustical Society of America -- October 1996 -- Volume 100, Issue 4, p. 2652
(so much so, that if and when I have any
oxidising to do, I intend to try this shit, it works with 3% peroxide
). Heres
another paper on the generation of the same with electrolysis: