The oxidation‐reduction thermodynamics for the manganese(III), ‐(IV), and ‐(II) ions, and their various complexes, are reviewed for both aqueous and aprotic media. In aqueous solutions the reduction potential for the manganese(III)/(II) couple has values that range from +1.51 V vs. NHE (hydrate at pH 0) to −0.95 V (glucarate complex at pH 13.5). The Mn(IV)/(III) couple has values that range from +1.0 V (solid MnIVO3 at pH 0) to −0.04 V (tris gluconate complex at pH 13.5). With anhydrous media the propensity for the Mn(III) ion to disproportionate to solid MnIVO2 and Mn(II) ion is avoided. For aprotic systems the range of redox potentials for various manganese complexes is from +2.01 V and +1.30 for the Mn(IV)/(III) and Mn(III)/(II) couples (bis terpyridyl tri‐N‐oxide complex in MeCN), respectively, to −0.96 V for the Mn(IV)/(III) couple (tris 3,5,‐di‐tert‐butylcatecholate complex in Me2SO). The redox reactions between manganese complexes and dioxygen species (O2, O2, and H2O2) also are reviewed.
During the past 15 years the biochemistry1 and chemistry2-5 of superoxide ion (02*-) has been thoroughly characterized.2•5 Superoxide ion can be generated in aqueous solutions from 02 by pulse radiolysis6-9 and from H202 by photolysis.10•11 Stable solutions of 02•-can be prepared in aprotic solvents by electrochemical methods,2-5•12 by the base-induced decomposition of H202,13,14 and by solubilizing K02 with 18-crown-6-ether.15-18 These methods are hindered by the low fluxes of 02'produced and by the presence of other reactive species.Tetramethylammonium superoxide [(Me4N)02], which was first prepared some 20 years ago from KÓ2 and (Me4N)OH-5H20 via a solid-phase metathesis reaction,19 is soluble in aprotic solvents and represents a convenient source of 02*-. A previous paper20Registry No.
In the past few decades, efforts have been made to clean sites polluted by heavy metals such as chromium. One of the new innovative methods of eradicating metals from soil is phytoremediation. Phytoremediation uses plants to pull metals from the soil through the roots. This article develops a system of differential equations to model the plant metal interaction of phytoremediation. We prove there exists a threshold time, t * , where the amount of metals in the environment meet a prescribed EPA criteria. The cost of phytoremediating up to time t * is computed.The cost function can be used to estimate the feasibility of clearing a polluted site through phytoremediation as opposed to alternate techniques such as brown filling.
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