Mercury photoreduction

The photoreduction of nitrobenzene using p5o ex filtered light from a medium pressure mercury arc was studied in petroleum, toluene, ether, 2-propanol, tert-butyl alcohol, diethylamine, triethylamine, aqueous solutions of 2-propanol and diethylamine and also in aqueous t-butylalcohol containing sodium boro-hydiide 3 >. Varying amounts of aniline, azo- and azoxybenzene were obtained. In the presence of a fourty-fold excess of benzophenone, a six-fold increase in the rate of aniline formation in ethereal solution was observed, and aniline formation was completely suppressed by addition of biacetyl or octafluomaphthalene Since unreacted nitrobenzene could be recovered in these experiments, it is demonstrated that the triplet state of nitrobenzene was quenched. 

However, organic pollutants are often accompanied by heavy metal ion contaminants that can be reduced by photogenerated electrons into their less toxic, nonsoluble metallic form. Ti02-assisted photoreductive catalysis was found to be useful in the removal of certain heavy metals including mercury, silver, platinum, palladium, rhodium, and gold via their reduction followed by deposition at the catalyst surface [20-22] or photoreduction of nitroaromatic compounds [23-26]. The use of photogenerated electrons for deposition of metal layers on... 

Tennakone K. Photoreduction of carbonic acid by mercury coated n-titanium dioxide. Sol Energy Mater 1984 10 235-8. 

In a DISP 2 mechanism the second-order disproportionation step is rate limiting (see Section 2). An example of such a process involves the photoreduction of the dye fluorescein in basic aqueous solutions at mercury electrodes (Compton etal., 1988b). The photoreduction of benzophenone (86) and fluorobenzophenone in acetonitrile also proceeds via a DISP 2 type mechanism as verified by channel electrode voltammetry (Leslie et al., 1997). The rate-limiting step is electron transfer (86c) between photoexcited radical anion and the initial anionic species formed on electron transfer at the electrode surface. This process is further complicated by significant con-proportionation (86e) and quenching of the benzophenone excited state (86f). 

The photophysics and photochemistry of gaseous PuFe have been ex-amined. Studies involving zinc porphyrins have been reported and include photo-oxidations in aqueous solution, photoreductions of Zn-TPP with hydrazines, and the role of Zn-TPPSa/ethyl viologen in photoredox processes. The mechanism of the photo-oxidation of water to oxygen with silver chloride has been discussed, and the synthesis of bis(chlorosilyl)-mercury compounds described. Colloidal CdSe has been shown to sensitize the photoreduction of O2 and of methyl viologen by cysteine. ... 

Photoreduction of Fe(hfac)3. The MOssbauer spectrum of a (1 250) mixture of 57pe(hfac)3 (hfacH = hexafluoroacetyl-acetone) in solid ethanol indicates that the complex was isolated uniformly in the matrix (Fig. 9a). When this sample was irradiated with the 300-400 nm light from the ultrahigh pressure mercury lamp, a doublet for high spin iron(II) species developed with the increase in the photoirradiation period (6 "v141 h), at the cost of the magnetic iron(III), i.e., the parent complex (Fig. 9b v f) (14). 

Photoreduction. Irradiation of 3,17/i-cstradiol (1) with a Hanovia mercury vapor lamp in an aqueous ethanol solution containing sodium sulfite gives as the major product 3/J,17/3-dihydroxy-5a,10)3-estrane (2). Reduction in the presence of sodium borohydride gives (3) and (4) in low yield.1 Tt is suggested that the reduction with sodium sulfite may proceed through a sulfinate intermediate. This novel photoreduction method was first observed with kynurenic acid (5), which is reduced in this way to kynurenine yellow (6).2... 

Costa M and Liss P (2000) Photoreduction and evolution of mercury from seawater. Sci Total Environ 261 125-135. 

Mo(CO)g and W(CO)6 adsorbed on porous Vycor glass or NaY zeolite become active when irradiated with a mercury lamp (> 290 nm) at room temperature in the presence of propene (Wada 1988). They remain active after irradiation ceases, indicating that the catalytically active species is formed by photoreduction of the metal carbonyl on the surface. The activity of Mo(CO)6/Al203 is enhanced by irradiation. 

Highly stabile nanoparticles result by combining in situ photopolymerization (acrylamide and N, Ai -methylene-bis-acrylamide, nonfiltered light from a DRSh-250 mercury lamp) and photoreduction of highly stable Ag ions. The... 

Photoreduction of a low loaded calcined Mo03/Si02 catalyst in a CO atmosphere under UV irradiation using a high pressure mercury lamp at room temperature or a laser beam of 308 nm, results in both the selective reduction of Mo " " to Mo + and the appearance of high catalytic activity in propene... 

Separation of Eu from a solution mixture of SmCls, EUCI3, and GdCl3 in a rare earth saturated ethanol—isopropanol system by photoreduction of Eu with a high pressure mercury lamp has been carried out by Qiu et al. (1991). The yield of Eu(II) was 95% and the purity of the precipitated Eu was 92%. EuCh was produced by photoreduction and precipitated from the alcohol mixture. The photochemical separation process is as follows ... 

Donohue (1980, 1982) has found that the quantum yield for the photoreduction of EuClj solutions in methanol is dramatically increased in the presence of 18C6. Upon photolysis by an Ar laser (351-363 nm), the 320 nm band of the divalent species increases by a factor of 10. A similar enhancement is also observed when SmClj solutions are irradiated by an excimer KrF laser (248 nm) the lifetime of the resulting transient blue colour of Sm(II) increases from a few seconds to 3 h and 4h, respectively, when 18C6 and (2,2,2) are added. Attempts to photoreduce R(III) ions using a mercury lamp have been unsuccessful, which points to a multiphoton process. 

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