Controlled organic redox reactivity

Controlled Organic Redox Reactivity on Irradiated Semiconductor Surfaces... 

The reaction of a redox couple that controls the system will directly cause a change in Eh. pH can affect the redox reactions by determining the concentrations of members of the redox couple in the soil solution. Decrease in soil pH will increase the solubility of trivalent iron and of other oxidized transition metal species, but will have a smaller effect on the solubility of the reduced species of these metals. The redox reactivity of a xenobiotic in soil is dependent on the pH. Altering the pH of the soil can affect redox reactions of toxic organics, just as it affects other pH-dependent reactions such as hydrolysis. 

The main objective of this chapter is to illustrate how fundamental aspects behind catalytic two-phase processes can be studied at polarizable interfaces between two immiscible electrolyte solutions (ITIES). The impact of electrochemistry at the ITIES is twofold first, electrochemical control over the Galvani potential difference allows fine-tuning of the organization and reactivity of catalysts and substrates at the liquid liquid junction. Second, electrochemical, spectroscopic, and photoelectrochemical techniques provide fundamental insights into the mechanistic aspects of catalytic and photocatalytic processes in liquid liquid systems. We shall describe some fundamental concepts in connection with charge transfer at polarizable ITIES and their relevance to two-phase catalysis. In subsequent sections, we shall review catalytic processes involving phase transfer catalysts, redox mediators, redox-active dyes, and nanoparticles from the optic provided by electrochemical and spectroscopic techniques. This chapter also features a brief overview of the properties of nanoparticles and microheterogeneous systems and their impact in the fields of catalysis and photocatalysis. 

Many such studies of sedimentary phosphorus profiles, also incorporating pore water measurement of soluble reactive phosphate, have demonstrated that redox-controlled dissolution of iron (hydr)oxides under reducing conditions at depth releases orthophosphate to solution. This then diffuses upwards (and downwards) from the pore water maximum to be re-adsorbed or co-precipitated with oxidized Fe in near-surface oxic sections. The downwards decrease in solid phase organic phosphorus indicates increasing release of phosphorus from deposited organic matter with depth, some of which will become associated with hydrous iron and other metal oxides, added to the pool of mobile phosphorus in pore water or contribute to soluble unreactive phosphorus . The characteristic reactions involving inorganic phosphorus in the sediments of Toolik Lake, Alaska, are shown in... 

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